Journal of Cardiac Failure Vol. 21 No. 10 2015
Clinical Investigations
Effect of Semirecumbent Sleep Position on Severity of Obstructive Sleep Apnea in Patients With Heart Failure OZEN K. BASOGLU, MD,1 BENGISU KESKIN, MD,2 MEHMET SEZAI TASBAKAN, MD,1 AND CEMIL GURGUN, MD3 Izmir, Turkey
ABSTRACT Background: Overnight rostral leg fluid displacement in heart failure (HF) patients is related to the high prevalence and severity of obstructive sleep apnea syndrome (OSAS). We hypothesized that rostral fluid shift would decrease in a semirecumbent (45-degree elevated) position, and evaluated the effect of semirecumbent sleeping on severity of sleep apnea in HF patients with OSAS. Methods and Results: Demographic, anthropometric characteristics, and medical history of 30 consecutive patients with HF and OSAS were recorded. The patients underwent 2 polysomnographic procedures within 1 week: 1 while lying flat and the other in a semirecumbent position. Out of 30 patients (mean age 54.7 6 10.2, 26 men), 16 (53.3%) were obese and 29 (96.7%) had comorbidities other than HF. Mean apnea-hypopnea index was 30.8 6 20.7 events/h while lying flat which decreased to 17.8 6 12.1 events/h in semirecumbent position (P ! .0001). Similarly, oxygen desaturation index decreased from 22.3 6 19.8 to 12.7 6 11.5 events/h (P ! .0001), and the percentage of sleep time with oxygen saturation (SpO2) !90% (P 5 .036) and lowest SpO2 (P 5 .004) were improved in the semirecumbent position. Furthermore, the percentage of stage N2 sleep decreased from 47.0% while lying flat to 39.6% (P 5 .014). Conclusions: The present findings support that the severity of OSAS decreased significantly in a semirecumbent sleep position in patients with HF. Therefore, semirecumbent sleeping may be a promising therapeutic option in the management of HF-related sleep apnea. (J Cardiac Fail 2015;21:842e847) Key Words: Obstructive sleep apnea, heart failure, fluid shift, semirecumbent sleep position.
higher (12%e53%) than in the general population.3e5 The prevalence of OSAS increases with increasing body mass index (BMI) and neck circumference, probably owing to fat deposition in the soft tissue surrounding the pharynx, which narrows the lumen and increases its collapsibility.6 However, factors other than obesity, such as nocturnal rostral fluid displacement, may play a greater role in the pathogenesis of OSAS in HF patients. The observation that OSAS is more prevalent in patients with edematous states, such as heart and renal failure, despite lower body weight raises the possibility that fluid retention may increase the risk of developing OSAS.7,8 This led to the hypothesis that fluid retention is involved in the pathogenesis of both obstructive and central sleep apnea. According to this hypothesis, during the day, fluid accumulates in the intravascular and interstitial spaces of the legs owing to gravity, and after lying down at night it redistributes rostrally, again owing to gravity. Some of this fluid may accumulate in the neck, increasing tissue pressure
Obstructive sleep apnea syndrome (OSAS) is a prevalent disorder, with at least 4% of middle-aged men and 2% of middle-aged women estimated to be affected in the general population. It is characterized by intermittent and recurrent episodes of partial (hypopnea) or complete (apnea) obstruction of the upper airway during sleep.1,2 OSAS is common in patients with heart failure (HF), and its prevalence is From the 1Department of Chest Diseases, Ege University Faculty of Medicine, Izmir, Turkey; 2Ege University Faculty of Medicine, Izmir, Turkey and 3Department of Cardiology, Ege University Faculty of Medicine, Izmir, Turkey. Manuscript received January 23, 2015; revised manuscript received May 4, 2015; revised manuscript accepted June 9, 2015. Reprint requests: Ozen K. Basoglu, MD, Professor, Department of Chest Diseases, Ege University School of Medicine, Bornova 35100, Izmir, Turkey. Tel: þ90 232 390 2900; Fax: þ90 232 388 7192. E-mail: ozen. [email protected] See page 847 for disclosure information. 1071-9164/$ - see front matter Ó 2015 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.cardfail.2015.06.004
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Effect of Sleep Position on Sleep Apnea in HF Patients
and causing the upper airway to narrow, predisposing to obstructive sleep apnea (OSA), or in the lungs, where it may provoke hyperventilation, predisposing to central sleep apnea.9,10 Lying down and standing up are associated with significant alterations in body fluid distribution, especially in OSAS patients who are edematous due to HF, and the interventions to decrease hypervolemic state and rostral overnight fluid shift improve OSAS severity.7,11,12 Therefore, we hypothesized that fluid displacement into peripharyngeal soft tissues while recumbent may contribute to narrowing and increased airflow resistance of the pharynx, predisposing to pharyngeal collapse and increasing the severity of sleep apnea in HF patients with OSAS, additionally that rostral fluid displacement would decrease if the patients sleep in a 45-degree elevated (semirecumbent) body position. The objective of the present study was to evaluate the effect of semirecumbent sleeping on the severity of sleep apnea in patients with HF and OSAS. Methods Study Population From October 2013 to September 2014, 155 consecutive HF patients who were followed in the HF outpatient clinic of the Department of Cardiology, School of Medicine, Ege University, were evaluated. Sixty-seven patients with clinical symptoms of sleep apnea (excessive daytime sleepiness, loud snoring, or witnessed apneas) were asked to undergo polysomnography. Fourteen patients refused to be included in the study, and 16 were excluded because of the diagnosis of central sleep apnea or primary snoring. Therefore, the study population consisted of 31 HF and OSAS patients in this prospective, cross-sectional, self-controlled study. Inclusion criteria were as follows: 1) men and women aged $18 and #80 years; 2) chronic HF due to ischemic or nonischemic dilated cardiomyopathy; 3) left ventricular ejection fraction #40% as assessed by echocardiography performed within 3 months of the diagnostic sleep study; 4) New York Heart Association functional class I or II with stable clinical status and optimal medical therapy for $1 month preceding the study; and 5) diagnosis of OSAS (apnea-hypopnea index [AHI] $5 events/h and the presence of sleep apnea clinical symptoms). Exclusion criteria were decompensated HF, cardiac cachexia, terminal disease, and organ deficiency (end-stage liver or kidney disease). The investigation conformed to the principles outlined in the Declaration of Helsinki, the local Ethics Committee approved the study protocol (reference number 12-8/8), and every subject gave written informed consent before participation. Demographic data (age, sex, smoking history, and psychotropic drug use), anthropometric measurements, medical history, and all prescribed medications were recorded. Pulmonary function tests, chest x-ray, arterial blood gas and biochemical analyses, including N-terminal proeB-type natriuretic peptide (NT-proBNP) levels, were performed. Subjective daytime sleepiness was assessed with the use of the Turkish version of the Epworth Sleepiness Scale, and scores O10 were considered to be indicate sleepiness.13 To evaluate daily physical activity, subjects also completed a diary of the day, indicating how much time they spent in the sitting, standing, and lying positions during the day preceding the sleep study from the time they arose in the morning until they lay down in the sleep laboratory.
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Polysomnography was performed with the use of standard techniques while the patients were lying flat on bed. The patients then underwent another polysomnography in a semirecumbent position within 1 week. Consequently, we performed a self-controlled clinical trial in which each patient served as his or her own control. Anthropometric and polysomnographic parameters of the patient while lying flat were compared with his/her parameters in a semirecumbent position. Polysomnography All patients underwent full overnight in-laboratory polysomnography (Alice 5 Diagnostic Sleep System; Philips, Respironics). Electroencephalography electrodes were positioned according to the international 10-20 system. Polysomnography consisted of monitoring of sleep by electroencephalography, electrooculography, electromyography, airflow, and respiratory muscle effort and included measures of electrocardiographic rhythm and blood oxygen saturation (SpO2). Thoracoabdominal plethysmograph, oronasal temperature thermistor, and nasal cannula pressure transducer system were used to identify apneas and hypopneas. A transcutaneous finger pulse oximeter was used to measure SpO2. Sleep was recorded and scored according to standard methods. Apnea was defined as obstructive if it was associated with continued or increased inspiratory effort throughout, as central if it was associated with absent inspiratory effort, and as mixed if it was associated with no inspiratory effort initially, followed by resumption of inspiratory effort in the latter portion of the event.14 AHI was the sum of the number of apneas and hypopneas per hour of sleep. OSAS was defined as an AHI of 5 events/h and the presence of clinical symptoms eg, excessive daytime sleepiness, loud snoring, witnessed apneas, and nocturnal choking or as an AHI of 15 events/h without any OSAS symptoms.15 Anthropometric Measurements Height, weight, BMI, and circumferences of neck, waist, and hip were measured before polysomnography. Subsequently, body weight was measured just before bedtime and within 30 minutes of waking in the morning. We measured the circumference of the neck at the superior border of the cricothyroid cartilage, and of the calf of the legs at their thickest portion, with a tape measure. Lines were drawn at these levels to ensure that measurements before and after sleep were made at exactly the same level. Patients then slept during polysomnography. Within 30 minutes of patients waking the next morning and before they got out of bed, urinated, or had anything to eat or drink, measurements of neck and calf circumferences were repeated. Differences between body weight and neck and calf circumferences before and after sleep were calculated as the overnight changes in these variables. All measurements were repeated in the 2nd polysomnography. The same sleep technicians, who were blinded to the study design, performed the measurements. Statistical Analysis Statistical analysis was performed with the use of SPSS 16.0 for Windows packaged software. Numeric variables were summarized as mean 6 SD. The significance of differences among repeated measures of groups was assessed by means of paired-samples test and Wilcoxon signed ranks test. A value of P ! .05 was considered to be significant for all statistical analyses. Correlation analysis was used to determine the relationship between the change in neck and calf circumferences and AHI or oxygen
844 Journal of Cardiac Failure Vol. 21 No. 10 October 2015 desaturation index. The correlations were scored as weak (r 5 0e0.49), moderate (r 5 0.5e0.74), or strong (r 5 0.75e1).
Results Characteristics of the Study Subjects
Eligible 31 HF patients, all diagnosed with OSAS, underwent polysomnography. One patient refused to undergo the 2nd sleep test and was excluded. Thirty HF patients with OSAS (26 men, 4 women) were included in the study. Sixteen patients (53.3%) were obese, and 29 (96.7%) had risk factors for HF (60.0% hypertension, 50.0% coronary artery disease, 46.7% dyslipidemia, 36.7% diabetes mellitus). The patients were using beta-blockers (90.0%), thiazide, loop diuretics or aldosterone antagonist (80.0%), angiotensin-converting enzyme inhibitors or angiotensin-2 antagonists (76.7%), and digitalis (30.0%). The most frequent sleep-related symptoms reported by the patients were snoring (96.7%), unrefreshing sleep (70.0%), nocturnal choking (60.0%), nocturia (60.0%), night sweating (56.7%), witnessed apnea (46.7%), dry month (46.7%), daytime sleepiness (36.7%) and morning headache (36.7%). Epworth Sleepiness Scores of 9 patients (30.0%) were O10. The characteristics of the patients are presented in Table 1. Effect of Sleep Position on Anthropometric Measurements
The anthropometric parameters were measured just before polysomnography and within 30 minutes of waking the next morning. Body weight (P ! .0001) and circumferences of the neck (P 5 .015), right calf (P ! .0001), and left calf (P ! .0001) decreased in the morning while lying flat. In a Table 1. Characteristics of the Study Subjects Characteristic Male/female, n Age (y) Current smoker, n (%) Psychotropic drug use, n (%) Body mass index (kg/m2) Neck circumference (cm) Waist circumference (cm) Hip circumference (cm) FEV1 (%) FVC (%) PaO2 (mm Hg) PaCO2 (mm Hg) NT-proBNP (pg/mL), median (range) LVEF (%) NYHA functional class, n (%) I II Epworth Sleepiness Score
Value 26/4 54.7 6 10.2 4 (13.3) 7 (23.3) 30.8 6 6.4 40.6 6 4.3 108.0 6 14.6 106.6 6 10.7 81.4 6 20.3 88.4 6 17.0 12.0 6 1.6 4.3 6 0.5 513.2 (4239.2) 28.7 6 6.6 6 (20.0) 24 (80.0) 7.5 6 4.4
FEV1, forced expiratory volume in 1 second; FVC, forced vital capacity; LVEF, left ventricular ejection fraction; NT-proBNP, N-terminal proeBtype natriuretic peptide; NYHA, New York Heart Association; PaCO2, arterial partial pressure of carbon dioxide; PaO2, arterial partial pressure of oxygen. Data are presented as mean 6 SD, unless otherwise specified.
semirecumbent position, there was also decrease in body weight (P ! .0001) and circumferences of the neck (P 5 .018), right calf (P ! .0001), and left calf (P ! .0001; Table 2). No association was found between the change in neck (P 5 .099; P 5 .069), right calf (P 5 .568; P 5 .530) and left calf (P 5 .604; P 5 .489) circumferences and AHI or oxygen desaturation index, respectively, during polysomnography performed while lying flat. Furthermore, there was no association between the change in neck (P 5 .742; P 5 .840), right calf (P 5 .369 and; P 5 .471), and left calf (P 5 .423; P 5 .558) circumferences and AHI or oxygen desaturation index, respectively, during polysomnography performed in a semirecumbent position. There was no difference between the time spent in sitting (5.6 6 2.8 vs 5.8 6 3.1 h; P 5 .819) and standing (6.2 6 2.9 vs 5.4 6 3.2 h; P 5 .299) positions the day preceding the sleep studies performed in the flat and semirecumbent positions, respectively. Effect of Sleep Position on Sleep Parameters
The mean AHI was 30.8 6 20.7 events/h while lying flat, whereas it was 17.8 6 12.1 events/h in a semirecumbent position, and the decrease was statistically significant (P ! .0001; Fig. 1). Similarly, oxygen desaturation index decreased from 22.3 6 19.8 to 12.7 6 11.5 events/h in the semirecumbent body position (P ! .0001), as shown in Figure 2. The percentages of stage N3 and rapid eye movement (REM) sleep increased while sleeping in a semirecumbent position, but the differences were not statistically significant, whereas the percentage of N2 sleep decreased from 47.0% to 39.6% compared with lying flat (P 5 .014). The percentage of sleep time with SpO2 ! 90% (P 5 .036) and lowest SpO2 (P 5 .004) also were improved in semirecumbent sleeping (Table 3). We assessed the sleeping positions of the patients with the help of an electrode during polysomnographic procedures and found that the patients slept more supine in a semirecumbent position (86.8%) compared with lying flat (68.2%; P ! .0001). Furthermore, out of 30 patients, 19 (63.3%) had positional sleep apnea, defined as a difference of $50% in apnea index between supine and nonsupine positions. Discussion Overnight rostral leg fluid displacement in HF patients is related to the high prevalence and severity of sleep apnea. In the present study, we hypothesized that rostral fluid shift would decrease in a 45-degree elevated sleep position, and therefore evaluated the effect of lying in a semirecumbent position on the severity of sleep apnea in HF patients with OSAS. We observed highly significant decreases in the indicators of OSAS severity, including AHI and oxygen desaturation index, while sleeping semirecumbently compared with lying flat. Furthermore, nocturnal oxygen saturations improved, and the percentage of stage N2 sleep
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Table 2. Effect of Sleep Position on Anthropometric Measurements Flat Position Measurement Weight (kg) Neck circumference (cm) Right calf circumference (cm) Left calf circumference (cm)
Before PSG 87.2 41.4 39.0 38.7
6 6 6 6
20.7 4.6 4.0 4.1
Semirecumbent Position
After PSG
P Value
Before PSG
6 6 6 6
!.0001 .015 !.0001 !.0001
86.9 41.3 38.8 38.7
86.3 41.0 38.2 38.0
20.4 4.5 4.1 4.0
6 6 6 6
20.6 4.4 4.1 4.1
After PSG
P Value
6 6 6 6
!.0001 .018 !.0001 !.0001
86.3 41.0 38.0 37.8
20.5 4.3 4.1 4.2
PSG, polysomnography. Data are presented as mean 6 SD.
decreased with the semirecumbent position. These findings suggest that semirecumbent sleeping may be a promising therapeutic option in the management of HF-related sleep apnea. Although continuous positive airway pressure (CPAP) is currently the mainstay of therapy for OSAS, semirecumbent sleep position can be used as adjuvant to other treatment modalities in patients with HF and OSAS. Fluid displacement from the lower extremities to the peripharyngeal soft tissues while recumbent contributes to narrowing and increased airflow resistance of the pharynx, and predisposes to pharyngeal collapse in patients with sleep apnea. Consequently, the interventions to reduce the overnight fluid shift to the neck may decrease the severity of sleep apnea. Redolfi et al11 investigated the effect of venous compression of the legs with the use of compression stockings in 6 nonobese sedentary men with OSA and found that AHI decreased in association with a reduction in leg fluid volume. Bucca et al12 evaluated whether intensive unloading with diuretics improves sleep-disordered breathing and increases pharyngeal caliber in 15 obese patients with severe OSAS, hypertension, and diastolic HF. They showed that intensive diuretic therapy increased upper airway cross-sectional area and decreased the AHI. In another study, the overnight reduction in leg fluid volume correlated inversely with AHI in 57 patients with HF and sleep apnea. Furthermore, the reduction in AHI in response
to CPAP therapy correlated with the attenuation of the overnight increase in neck circumference, which suggests that CPAP also alleviates OSA by preventing overnight fluid accumulation in the neck by increasing intrathoracic and extrathoracic airway pressure.16 In the present study, we hypothesized that rostral fluid displacement would decrease if the patients slept in a semirecumbent position, and we performed polysomnography on 2 different nights with the patients lying flat and in a semirecumbent position. We observed that nocturnal oxygen desaturations and respiratory events decreased significantly in semirecumbent position. The mean AHI was 30.8 events/h while lying flat and 17.8 6 12.1 events/h in semirecumbent sleeping. Similarly, oxygen desaturation index decreased from 22.3 to 12.7 events/h in a semirecumbent body position. We suggest that semirecumbent sleeping may be a conservative therapeutic option in the management of HF-related sleep apnea, because we observed highly significant decreases in the indicators of OSAS severity. OSA tends to worsen in the supine posture owing to the effect of gravity on tongue position. Positional OSA was first defined as a difference of $50% in apnea index between supine and nonsupine positions. Positional therapy has been found to have a significant influence on OSA severity.16 In the present study, 19 patients (63.3%) had positional OSA. Although more than one-half of our patients
Fig. 1. Comparison of apnea-hypopnea index (AHI) in flat and semirecumbent positions. Data are presented as interquartile range (boxes), data range (whiskers) and median (horizontal line).
Fig. 2. Comparison of oxygen desaturation index (ODI) in flat and semirecumbent positions. Data are presented as interquartile range (boxes), data range (whiskers) and median (horizontal line).
846 Journal of Cardiac Failure Vol. 21 No. 10 October 2015 Table 3. Effect of Sleep Position on Sleep Parameters Parameter Apnea-hypopnea index (/h) Oxygen desaturation index (/h) Total sleep time (min) Sleep efficiency (%) Sleep latency (min) N1 sleep (%) N2 sleep (%) N3 sleep (%) REM sleep (%) Mean SpO2 (%) Lowest SpO2 (%) Sleep time with SpO2 !90% (%)
Flat Position
Semirecumbent Position
P Value
30.8 6 20.7 22.3 6 19.8
17.8 6 12.1 12.7 6 11.5
!.0001 !.0001
6 6 6 6 6 6 6 6 6 6
.304 .202 .321 .229 .014 .106 .360 .063 .004 .036
347.9 81.6 17.0 6.2 47.0 35.1 11.7 94.5 80.9 3.6
6 6 6 6 6 6 6 6 6 6
46.2 10.6 33.2 6.7 16.7 15.8 7.4 1.5 10.7 7.1
336.1 78.5 15.0 6.1 39.6 40.5 12.9 94.9 84.9 1.9
54.6 13.4 16.7 4.2 12.9 15.1 7.0 1.4 6.9 4.1
N, nonerapid eye movement; REM, rapid eye movement; SpO2, pulse oximeter oxygen saturation. Data are presented as mean 6 SD.
were position dependent and the patients slept more supine in semirecumbent position (86.8%) compared with lying flat (68.2%), the severity of sleep apnea decreased significantly during semirecumbent sleeping. Soll et al17 performed polysomnography at 0-, 15-, 30-, and 45-degree elevated positions in 25 stable HF patients. Seventeen of them had Cheyne-Stokes respiration (CSR) and 8 had no CSR. They found that the Cheyne-Stokes apnea index decreased with the increase in sleeping angle, whereas hypopnea index showed no change. To the best of our knowledge, ours is the 1st study evaluating the effect of semirecumbent sleeping in patients with HF and obstructive-dominant sleep apnea. We observed highly significant decreases in the indicators of OSAS severity in the semirecumbent position. Furthermore, the percentages of stage N3 and REM sleep increased, and stage N2 decreased, that is, the sleep architecture improved with semirecumbent sleeping. CPAP is the most effective treatment for OSA, because it improves symptoms, normalizes the risk of traffic and workplace accidents, and reduces the elevated sympathetic activity and risk for cardiovascular morbidity and mortality.18 However, semirecumbent sleeping can be used as conservative treatment in HF patients with OSAS. Rostral fluid shift from the lower extremities to the upper body plays a role in narrowing the upper airway in patients with OSA. Several studies have demonstrated a consistent association between nocturnal fluid shift, increase in neck circumference, and the severity of OSA in patients with HF, hypertension, and end-stage renal disease.7,8,19,20 Yumimo et al19 evaluated 57 patients with HF and sleep apnea (35 obstructive-dominant and 22 central-dominant). The overnight reduction in leg fluid volume correlated inversely with AHI and the overnight change in neck circumference in both groups. Friedman et al20 also showed that AHI was strongly related to the amount of fluid displaced from the leg overnight and increase in neck circumference in both drug-resistant and controlled hypertension patients. In 26
end-stage renal disease patients, it was demonstrated that nocturnal rostral fluid shift was associated significantly with neck circumference and apnea-hypopnea time but not with AHI.8 In contrast to earlier data, we found no correlation between the change in neck and calf circumferences and AHI or oxygen desaturation index. In addition, circumferences of the calf and body weight measured in the morning decreased significantly compared with the measurements at night, as expected, whereas the average neck circumference in the morning was smaller than in the night in both flat and semirecumbent positions. Therefore, the significantly lower value of AHI in the semirecumbent position could not be connected to the neck circumference changes. This might be explained by the fact that a majority of patients (80%) were using diuretics and they lost significant weight during the night. The decreased effect of gravity on the tongue base in the semirecumbent position could be another explanation. Furthermore, we measured the circumferences with a tape measure and did not use objective methods. For all these reasons, the rostral fluid shift hypothesis could not be rejected with the use of the present results. It is known that complex anatomic, physiologic, and neural factors are involved in upper airway collapse in OSAS patients. Study Limitations The present study has a number of limitations. First, we did not design it as a randomized controlled trial, because it was not possible to recruit age-, sex-, BMI-, ejection fraction-, and AHI-matched sleep apnea and HF patients. Therefore, we performed a self-controlled clinical trial in which each patient served as his or her own control. The patients were all in stable clinical status and taking optimal medical therapy. They underwent 2 polysomnographic procedures within 1 week while lying flat and in a semirecumbent position. Anthropometric and polysomnographic parameters of the patient in the flat position were compared with the patient’s parameters in semirecumbent sleeping. Second, we measured the circumference of the neck and calf of the legs with a tape measure. However, there are objective methods such as bioelectrical impedance for leg fluid volume and acoustic pharyngometry for pharyngeal cross-sectional area.8,12 Even so, the measurements were performed by the same technicians, and lines were drawn to ensure that the measurements were made at exactly the same levels. Additionally, the assessment of daily physical activity of the patients was self-reported and was not an hour-by-hour schedule. Sleep apnea patients follow a sedentary lifestyle, and this is related to impaired fluid dynamics in the lower body, particularly the legs.21 We did not evaluate physical activity in detail, but there was no difference between the time spent in the sitting and standing positions the day preceding the sleep studies performed in flat and semirecumbent positions. Furthermore, the volume of urine excreted was not recorded in the study although 80% of the patients were using diuretics and there was a
Effect of Sleep Position on Sleep Apnea in HF Patients
significant weight loss in the morning. Finally, the patients were using different kinds of medications, but standardizing the treatments would not be appropriate owing to the serious comorbidities of the patients. Conclusion The present findings suggest that semirecumbent sleeping may be a promising therapeutic option in the management of HF-related sleep apnea, because we observed highly significant decreases in the indicators of OSAS severity, including AHI and oxygen desaturation index, while semirecumbent sleeping compared with lying flat. CPAP is regarded to be the criterion standard treatment of OSA, but semirecumbent sleep position therapy can be used as an adjuvant to other treatment modalities in patients with HF and OSAS. The role of semirecumbent position therapy, indicators for treatment response, and long-term outcomes should be clarified in large-sample well designed studies in HF patients with OSAS. Acknowledgments The authors thank sleep technicians Bahar Yoruk, Yakup Coskun, and Merve Ozdemir in the Sleep Disorders Laboratory, Department of Chest Diseases, School of Medicine, Ege University, for their valuable help in gathering the data related to the systemic health of the patients. The authors also thank Timur Kose from the Department of Biostatistics, Ege University School of Medicine, for statistical assistance. Disclosures None.
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4. Arzt M, Young T, Finn L, Skatrud JB, Ryan CM, Newton GE, et al. Sleepiness and sleep in patients with both systolic heart failure and obstructive sleep apnea. Arch Intern Med 2006;166:1716e22. 5. Kasai T, Bradley TD. Obstructive sleep apnea and heart failure: pathophysiologic and therapeutic implications. J Am Coll Cardiol 2011;57: 119e27. 6. Schwartz AR, Patil SP, Laffan AM, Polotsky V, Schneider H, Smith PL. Obesity and obstructive sleep apnea: pathogenic mechanisms and therapeutic approaches. Proc Am Thorac Soc 2008;5: 185e92. 7. Redolfi S, Yumino D, Ruttanaumpawan P, Yau B, Su MC, Lam J, et al. Relationship between overnight rostral fluid shift and obstructive sleep apnea in nonobese men. Am J Respir Crit Care Med 2009;179:241e6. 8. Elias RM, Bradley TD, Kasai T, Motwani SS, Chan CT. Rostral overnight fluid shift in end-stage renal disease: relationship with obstructive sleep apnea. Nephrol Dial Transplant 2012;27:1569e73. 9. White LH, Bradley TD. Role of nocturnal rostral fluid shift in the pathogenesis of obstructive and central sleep apnoea. J Physiol 2013;591:1179e93. 10. Mirrakhimov AE. Supine fluid redistribution: should we consider this as an important risk factor for obstructive sleep apnea? Sleep Breath 2013;17:511e23. 11. Redolfi S, Arnulf I, Pottier M, Bradley TD, Similowski T. Effects of venous compression of the legs on overnight rostral fluid shift and obstructive sleep apnea. Respir Physiol Neurobiol 2011;175:390e3. 12. Bucca CB, Brussino L, Battisti A, Mutani R, Rolla G, Mangiardi L, et al. Diuretics in obstructive sleep apnea with diastolic heart failure. Chest 2007;132:440e6. 13. Izci B, Ardic S, Firat H, Sahin A, Altinors M, Karacan I. Reliability and validity studies of the Turkish version of the Epworth Sleepiness Scale. Sleep Breath 2008;12:161e8. 14. Iber C, Ancoli-Israel S, Chesson AL, Quan SF, American Academy of Sleep Medicine. The AASM manual 2007 for the scoring of sleep and associated events: rules, terminology and technical specifications. Westchester, Illinois: American Academy of Sleep Medicine; 2007. 15. American Academy of Sleep Medicine. International classification of sleep disorders: diagnostic and coding manual. 2nd ed. Westchester, Illinois: American Academy of Sleep Medicine; 2005. 16. Ravesloot MJ, van Maanen JP, Dun L, de Vries N. The undervalued potential of positional therapy in position-dependent snoring and obstructive sleep apneada review of the literature. Sleep Breath 2013;17:39e49. 17. Soll BA, Yeo KK, Davis JW, Seto TB, Schatz IJ, Shen EN. The effect of posture on Cheyne-Stokes respirations and hemodynamics in patients with heart failure. Sleep 2009;32:1499e506. 18. Kakkar RK, Berry RB. Positive airway pressure treatment for obstructive sleep apnea. Chest 2007;132:1057e72. 19. Yumino D, Redolfi S, Ruttanaumpawan P, Su MC, Smith S, Newton GE, et al. Nocturnal rostral fluid shift: a unifying concept for the pathogenesis of obstructive and central sleep apnea in men with heart failure. Circulation 2010;121:1598e605. 20. Friedman O, Bradley TD, Chan CT, Parkes R, Logan AG. Relationship between overnight rostral fluid shift and obstructive sleep apnea in drug-resistant hypertension. Hypertension 2010;56:1077e82. 21. Mirrakhimov AE. Physical exercise related improvement in obstructive sleep apnea. Look for the rostral fluid shift. Med Hypotheses 2013;80:125e8.
Clinical Investigations
Effect of Semirecumbent Sleep Position on Severity of Obstructive Sleep Apnea in Patients With Heart Failure OZEN K. BASOGLU, MD,1 BENGISU KESKIN, MD,2 MEHMET SEZAI TASBAKAN, MD,1 AND CEMIL GURGUN, MD3 Izmir, Turkey
ABSTRACT Background: Overnight rostral leg fluid displacement in heart failure (HF) patients is related to the high prevalence and severity of obstructive sleep apnea syndrome (OSAS). We hypothesized that rostral fluid shift would decrease in a semirecumbent (45-degree elevated) position, and evaluated the effect of semirecumbent sleeping on severity of sleep apnea in HF patients with OSAS. Methods and Results: Demographic, anthropometric characteristics, and medical history of 30 consecutive patients with HF and OSAS were recorded. The patients underwent 2 polysomnographic procedures within 1 week: 1 while lying flat and the other in a semirecumbent position. Out of 30 patients (mean age 54.7 6 10.2, 26 men), 16 (53.3%) were obese and 29 (96.7%) had comorbidities other than HF. Mean apnea-hypopnea index was 30.8 6 20.7 events/h while lying flat which decreased to 17.8 6 12.1 events/h in semirecumbent position (P ! .0001). Similarly, oxygen desaturation index decreased from 22.3 6 19.8 to 12.7 6 11.5 events/h (P ! .0001), and the percentage of sleep time with oxygen saturation (SpO2) !90% (P 5 .036) and lowest SpO2 (P 5 .004) were improved in the semirecumbent position. Furthermore, the percentage of stage N2 sleep decreased from 47.0% while lying flat to 39.6% (P 5 .014). Conclusions: The present findings support that the severity of OSAS decreased significantly in a semirecumbent sleep position in patients with HF. Therefore, semirecumbent sleeping may be a promising therapeutic option in the management of HF-related sleep apnea. (J Cardiac Fail 2015;21:842e847) Key Words: Obstructive sleep apnea, heart failure, fluid shift, semirecumbent sleep position.
higher (12%e53%) than in the general population.3e5 The prevalence of OSAS increases with increasing body mass index (BMI) and neck circumference, probably owing to fat deposition in the soft tissue surrounding the pharynx, which narrows the lumen and increases its collapsibility.6 However, factors other than obesity, such as nocturnal rostral fluid displacement, may play a greater role in the pathogenesis of OSAS in HF patients. The observation that OSAS is more prevalent in patients with edematous states, such as heart and renal failure, despite lower body weight raises the possibility that fluid retention may increase the risk of developing OSAS.7,8 This led to the hypothesis that fluid retention is involved in the pathogenesis of both obstructive and central sleep apnea. According to this hypothesis, during the day, fluid accumulates in the intravascular and interstitial spaces of the legs owing to gravity, and after lying down at night it redistributes rostrally, again owing to gravity. Some of this fluid may accumulate in the neck, increasing tissue pressure
Obstructive sleep apnea syndrome (OSAS) is a prevalent disorder, with at least 4% of middle-aged men and 2% of middle-aged women estimated to be affected in the general population. It is characterized by intermittent and recurrent episodes of partial (hypopnea) or complete (apnea) obstruction of the upper airway during sleep.1,2 OSAS is common in patients with heart failure (HF), and its prevalence is From the 1Department of Chest Diseases, Ege University Faculty of Medicine, Izmir, Turkey; 2Ege University Faculty of Medicine, Izmir, Turkey and 3Department of Cardiology, Ege University Faculty of Medicine, Izmir, Turkey. Manuscript received January 23, 2015; revised manuscript received May 4, 2015; revised manuscript accepted June 9, 2015. Reprint requests: Ozen K. Basoglu, MD, Professor, Department of Chest Diseases, Ege University School of Medicine, Bornova 35100, Izmir, Turkey. Tel: þ90 232 390 2900; Fax: þ90 232 388 7192. E-mail: ozen. [email protected] See page 847 for disclosure information. 1071-9164/$ - see front matter Ó 2015 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.cardfail.2015.06.004
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Effect of Sleep Position on Sleep Apnea in HF Patients
and causing the upper airway to narrow, predisposing to obstructive sleep apnea (OSA), or in the lungs, where it may provoke hyperventilation, predisposing to central sleep apnea.9,10 Lying down and standing up are associated with significant alterations in body fluid distribution, especially in OSAS patients who are edematous due to HF, and the interventions to decrease hypervolemic state and rostral overnight fluid shift improve OSAS severity.7,11,12 Therefore, we hypothesized that fluid displacement into peripharyngeal soft tissues while recumbent may contribute to narrowing and increased airflow resistance of the pharynx, predisposing to pharyngeal collapse and increasing the severity of sleep apnea in HF patients with OSAS, additionally that rostral fluid displacement would decrease if the patients sleep in a 45-degree elevated (semirecumbent) body position. The objective of the present study was to evaluate the effect of semirecumbent sleeping on the severity of sleep apnea in patients with HF and OSAS. Methods Study Population From October 2013 to September 2014, 155 consecutive HF patients who were followed in the HF outpatient clinic of the Department of Cardiology, School of Medicine, Ege University, were evaluated. Sixty-seven patients with clinical symptoms of sleep apnea (excessive daytime sleepiness, loud snoring, or witnessed apneas) were asked to undergo polysomnography. Fourteen patients refused to be included in the study, and 16 were excluded because of the diagnosis of central sleep apnea or primary snoring. Therefore, the study population consisted of 31 HF and OSAS patients in this prospective, cross-sectional, self-controlled study. Inclusion criteria were as follows: 1) men and women aged $18 and #80 years; 2) chronic HF due to ischemic or nonischemic dilated cardiomyopathy; 3) left ventricular ejection fraction #40% as assessed by echocardiography performed within 3 months of the diagnostic sleep study; 4) New York Heart Association functional class I or II with stable clinical status and optimal medical therapy for $1 month preceding the study; and 5) diagnosis of OSAS (apnea-hypopnea index [AHI] $5 events/h and the presence of sleep apnea clinical symptoms). Exclusion criteria were decompensated HF, cardiac cachexia, terminal disease, and organ deficiency (end-stage liver or kidney disease). The investigation conformed to the principles outlined in the Declaration of Helsinki, the local Ethics Committee approved the study protocol (reference number 12-8/8), and every subject gave written informed consent before participation. Demographic data (age, sex, smoking history, and psychotropic drug use), anthropometric measurements, medical history, and all prescribed medications were recorded. Pulmonary function tests, chest x-ray, arterial blood gas and biochemical analyses, including N-terminal proeB-type natriuretic peptide (NT-proBNP) levels, were performed. Subjective daytime sleepiness was assessed with the use of the Turkish version of the Epworth Sleepiness Scale, and scores O10 were considered to be indicate sleepiness.13 To evaluate daily physical activity, subjects also completed a diary of the day, indicating how much time they spent in the sitting, standing, and lying positions during the day preceding the sleep study from the time they arose in the morning until they lay down in the sleep laboratory.
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Polysomnography was performed with the use of standard techniques while the patients were lying flat on bed. The patients then underwent another polysomnography in a semirecumbent position within 1 week. Consequently, we performed a self-controlled clinical trial in which each patient served as his or her own control. Anthropometric and polysomnographic parameters of the patient while lying flat were compared with his/her parameters in a semirecumbent position. Polysomnography All patients underwent full overnight in-laboratory polysomnography (Alice 5 Diagnostic Sleep System; Philips, Respironics). Electroencephalography electrodes were positioned according to the international 10-20 system. Polysomnography consisted of monitoring of sleep by electroencephalography, electrooculography, electromyography, airflow, and respiratory muscle effort and included measures of electrocardiographic rhythm and blood oxygen saturation (SpO2). Thoracoabdominal plethysmograph, oronasal temperature thermistor, and nasal cannula pressure transducer system were used to identify apneas and hypopneas. A transcutaneous finger pulse oximeter was used to measure SpO2. Sleep was recorded and scored according to standard methods. Apnea was defined as obstructive if it was associated with continued or increased inspiratory effort throughout, as central if it was associated with absent inspiratory effort, and as mixed if it was associated with no inspiratory effort initially, followed by resumption of inspiratory effort in the latter portion of the event.14 AHI was the sum of the number of apneas and hypopneas per hour of sleep. OSAS was defined as an AHI of 5 events/h and the presence of clinical symptoms eg, excessive daytime sleepiness, loud snoring, witnessed apneas, and nocturnal choking or as an AHI of 15 events/h without any OSAS symptoms.15 Anthropometric Measurements Height, weight, BMI, and circumferences of neck, waist, and hip were measured before polysomnography. Subsequently, body weight was measured just before bedtime and within 30 minutes of waking in the morning. We measured the circumference of the neck at the superior border of the cricothyroid cartilage, and of the calf of the legs at their thickest portion, with a tape measure. Lines were drawn at these levels to ensure that measurements before and after sleep were made at exactly the same level. Patients then slept during polysomnography. Within 30 minutes of patients waking the next morning and before they got out of bed, urinated, or had anything to eat or drink, measurements of neck and calf circumferences were repeated. Differences between body weight and neck and calf circumferences before and after sleep were calculated as the overnight changes in these variables. All measurements were repeated in the 2nd polysomnography. The same sleep technicians, who were blinded to the study design, performed the measurements. Statistical Analysis Statistical analysis was performed with the use of SPSS 16.0 for Windows packaged software. Numeric variables were summarized as mean 6 SD. The significance of differences among repeated measures of groups was assessed by means of paired-samples test and Wilcoxon signed ranks test. A value of P ! .05 was considered to be significant for all statistical analyses. Correlation analysis was used to determine the relationship between the change in neck and calf circumferences and AHI or oxygen
844 Journal of Cardiac Failure Vol. 21 No. 10 October 2015 desaturation index. The correlations were scored as weak (r 5 0e0.49), moderate (r 5 0.5e0.74), or strong (r 5 0.75e1).
Results Characteristics of the Study Subjects
Eligible 31 HF patients, all diagnosed with OSAS, underwent polysomnography. One patient refused to undergo the 2nd sleep test and was excluded. Thirty HF patients with OSAS (26 men, 4 women) were included in the study. Sixteen patients (53.3%) were obese, and 29 (96.7%) had risk factors for HF (60.0% hypertension, 50.0% coronary artery disease, 46.7% dyslipidemia, 36.7% diabetes mellitus). The patients were using beta-blockers (90.0%), thiazide, loop diuretics or aldosterone antagonist (80.0%), angiotensin-converting enzyme inhibitors or angiotensin-2 antagonists (76.7%), and digitalis (30.0%). The most frequent sleep-related symptoms reported by the patients were snoring (96.7%), unrefreshing sleep (70.0%), nocturnal choking (60.0%), nocturia (60.0%), night sweating (56.7%), witnessed apnea (46.7%), dry month (46.7%), daytime sleepiness (36.7%) and morning headache (36.7%). Epworth Sleepiness Scores of 9 patients (30.0%) were O10. The characteristics of the patients are presented in Table 1. Effect of Sleep Position on Anthropometric Measurements
The anthropometric parameters were measured just before polysomnography and within 30 minutes of waking the next morning. Body weight (P ! .0001) and circumferences of the neck (P 5 .015), right calf (P ! .0001), and left calf (P ! .0001) decreased in the morning while lying flat. In a Table 1. Characteristics of the Study Subjects Characteristic Male/female, n Age (y) Current smoker, n (%) Psychotropic drug use, n (%) Body mass index (kg/m2) Neck circumference (cm) Waist circumference (cm) Hip circumference (cm) FEV1 (%) FVC (%) PaO2 (mm Hg) PaCO2 (mm Hg) NT-proBNP (pg/mL), median (range) LVEF (%) NYHA functional class, n (%) I II Epworth Sleepiness Score
Value 26/4 54.7 6 10.2 4 (13.3) 7 (23.3) 30.8 6 6.4 40.6 6 4.3 108.0 6 14.6 106.6 6 10.7 81.4 6 20.3 88.4 6 17.0 12.0 6 1.6 4.3 6 0.5 513.2 (4239.2) 28.7 6 6.6 6 (20.0) 24 (80.0) 7.5 6 4.4
FEV1, forced expiratory volume in 1 second; FVC, forced vital capacity; LVEF, left ventricular ejection fraction; NT-proBNP, N-terminal proeBtype natriuretic peptide; NYHA, New York Heart Association; PaCO2, arterial partial pressure of carbon dioxide; PaO2, arterial partial pressure of oxygen. Data are presented as mean 6 SD, unless otherwise specified.
semirecumbent position, there was also decrease in body weight (P ! .0001) and circumferences of the neck (P 5 .018), right calf (P ! .0001), and left calf (P ! .0001; Table 2). No association was found between the change in neck (P 5 .099; P 5 .069), right calf (P 5 .568; P 5 .530) and left calf (P 5 .604; P 5 .489) circumferences and AHI or oxygen desaturation index, respectively, during polysomnography performed while lying flat. Furthermore, there was no association between the change in neck (P 5 .742; P 5 .840), right calf (P 5 .369 and; P 5 .471), and left calf (P 5 .423; P 5 .558) circumferences and AHI or oxygen desaturation index, respectively, during polysomnography performed in a semirecumbent position. There was no difference between the time spent in sitting (5.6 6 2.8 vs 5.8 6 3.1 h; P 5 .819) and standing (6.2 6 2.9 vs 5.4 6 3.2 h; P 5 .299) positions the day preceding the sleep studies performed in the flat and semirecumbent positions, respectively. Effect of Sleep Position on Sleep Parameters
The mean AHI was 30.8 6 20.7 events/h while lying flat, whereas it was 17.8 6 12.1 events/h in a semirecumbent position, and the decrease was statistically significant (P ! .0001; Fig. 1). Similarly, oxygen desaturation index decreased from 22.3 6 19.8 to 12.7 6 11.5 events/h in the semirecumbent body position (P ! .0001), as shown in Figure 2. The percentages of stage N3 and rapid eye movement (REM) sleep increased while sleeping in a semirecumbent position, but the differences were not statistically significant, whereas the percentage of N2 sleep decreased from 47.0% to 39.6% compared with lying flat (P 5 .014). The percentage of sleep time with SpO2 ! 90% (P 5 .036) and lowest SpO2 (P 5 .004) also were improved in semirecumbent sleeping (Table 3). We assessed the sleeping positions of the patients with the help of an electrode during polysomnographic procedures and found that the patients slept more supine in a semirecumbent position (86.8%) compared with lying flat (68.2%; P ! .0001). Furthermore, out of 30 patients, 19 (63.3%) had positional sleep apnea, defined as a difference of $50% in apnea index between supine and nonsupine positions. Discussion Overnight rostral leg fluid displacement in HF patients is related to the high prevalence and severity of sleep apnea. In the present study, we hypothesized that rostral fluid shift would decrease in a 45-degree elevated sleep position, and therefore evaluated the effect of lying in a semirecumbent position on the severity of sleep apnea in HF patients with OSAS. We observed highly significant decreases in the indicators of OSAS severity, including AHI and oxygen desaturation index, while sleeping semirecumbently compared with lying flat. Furthermore, nocturnal oxygen saturations improved, and the percentage of stage N2 sleep
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Table 2. Effect of Sleep Position on Anthropometric Measurements Flat Position Measurement Weight (kg) Neck circumference (cm) Right calf circumference (cm) Left calf circumference (cm)
Before PSG 87.2 41.4 39.0 38.7
6 6 6 6
20.7 4.6 4.0 4.1
Semirecumbent Position
After PSG
P Value
Before PSG
6 6 6 6
!.0001 .015 !.0001 !.0001
86.9 41.3 38.8 38.7
86.3 41.0 38.2 38.0
20.4 4.5 4.1 4.0
6 6 6 6
20.6 4.4 4.1 4.1
After PSG
P Value
6 6 6 6
!.0001 .018 !.0001 !.0001
86.3 41.0 38.0 37.8
20.5 4.3 4.1 4.2
PSG, polysomnography. Data are presented as mean 6 SD.
decreased with the semirecumbent position. These findings suggest that semirecumbent sleeping may be a promising therapeutic option in the management of HF-related sleep apnea. Although continuous positive airway pressure (CPAP) is currently the mainstay of therapy for OSAS, semirecumbent sleep position can be used as adjuvant to other treatment modalities in patients with HF and OSAS. Fluid displacement from the lower extremities to the peripharyngeal soft tissues while recumbent contributes to narrowing and increased airflow resistance of the pharynx, and predisposes to pharyngeal collapse in patients with sleep apnea. Consequently, the interventions to reduce the overnight fluid shift to the neck may decrease the severity of sleep apnea. Redolfi et al11 investigated the effect of venous compression of the legs with the use of compression stockings in 6 nonobese sedentary men with OSA and found that AHI decreased in association with a reduction in leg fluid volume. Bucca et al12 evaluated whether intensive unloading with diuretics improves sleep-disordered breathing and increases pharyngeal caliber in 15 obese patients with severe OSAS, hypertension, and diastolic HF. They showed that intensive diuretic therapy increased upper airway cross-sectional area and decreased the AHI. In another study, the overnight reduction in leg fluid volume correlated inversely with AHI in 57 patients with HF and sleep apnea. Furthermore, the reduction in AHI in response
to CPAP therapy correlated with the attenuation of the overnight increase in neck circumference, which suggests that CPAP also alleviates OSA by preventing overnight fluid accumulation in the neck by increasing intrathoracic and extrathoracic airway pressure.16 In the present study, we hypothesized that rostral fluid displacement would decrease if the patients slept in a semirecumbent position, and we performed polysomnography on 2 different nights with the patients lying flat and in a semirecumbent position. We observed that nocturnal oxygen desaturations and respiratory events decreased significantly in semirecumbent position. The mean AHI was 30.8 events/h while lying flat and 17.8 6 12.1 events/h in semirecumbent sleeping. Similarly, oxygen desaturation index decreased from 22.3 to 12.7 events/h in a semirecumbent body position. We suggest that semirecumbent sleeping may be a conservative therapeutic option in the management of HF-related sleep apnea, because we observed highly significant decreases in the indicators of OSAS severity. OSA tends to worsen in the supine posture owing to the effect of gravity on tongue position. Positional OSA was first defined as a difference of $50% in apnea index between supine and nonsupine positions. Positional therapy has been found to have a significant influence on OSA severity.16 In the present study, 19 patients (63.3%) had positional OSA. Although more than one-half of our patients
Fig. 1. Comparison of apnea-hypopnea index (AHI) in flat and semirecumbent positions. Data are presented as interquartile range (boxes), data range (whiskers) and median (horizontal line).
Fig. 2. Comparison of oxygen desaturation index (ODI) in flat and semirecumbent positions. Data are presented as interquartile range (boxes), data range (whiskers) and median (horizontal line).
846 Journal of Cardiac Failure Vol. 21 No. 10 October 2015 Table 3. Effect of Sleep Position on Sleep Parameters Parameter Apnea-hypopnea index (/h) Oxygen desaturation index (/h) Total sleep time (min) Sleep efficiency (%) Sleep latency (min) N1 sleep (%) N2 sleep (%) N3 sleep (%) REM sleep (%) Mean SpO2 (%) Lowest SpO2 (%) Sleep time with SpO2 !90% (%)
Flat Position
Semirecumbent Position
P Value
30.8 6 20.7 22.3 6 19.8
17.8 6 12.1 12.7 6 11.5
!.0001 !.0001
6 6 6 6 6 6 6 6 6 6
.304 .202 .321 .229 .014 .106 .360 .063 .004 .036
347.9 81.6 17.0 6.2 47.0 35.1 11.7 94.5 80.9 3.6
6 6 6 6 6 6 6 6 6 6
46.2 10.6 33.2 6.7 16.7 15.8 7.4 1.5 10.7 7.1
336.1 78.5 15.0 6.1 39.6 40.5 12.9 94.9 84.9 1.9
54.6 13.4 16.7 4.2 12.9 15.1 7.0 1.4 6.9 4.1
N, nonerapid eye movement; REM, rapid eye movement; SpO2, pulse oximeter oxygen saturation. Data are presented as mean 6 SD.
were position dependent and the patients slept more supine in semirecumbent position (86.8%) compared with lying flat (68.2%), the severity of sleep apnea decreased significantly during semirecumbent sleeping. Soll et al17 performed polysomnography at 0-, 15-, 30-, and 45-degree elevated positions in 25 stable HF patients. Seventeen of them had Cheyne-Stokes respiration (CSR) and 8 had no CSR. They found that the Cheyne-Stokes apnea index decreased with the increase in sleeping angle, whereas hypopnea index showed no change. To the best of our knowledge, ours is the 1st study evaluating the effect of semirecumbent sleeping in patients with HF and obstructive-dominant sleep apnea. We observed highly significant decreases in the indicators of OSAS severity in the semirecumbent position. Furthermore, the percentages of stage N3 and REM sleep increased, and stage N2 decreased, that is, the sleep architecture improved with semirecumbent sleeping. CPAP is the most effective treatment for OSA, because it improves symptoms, normalizes the risk of traffic and workplace accidents, and reduces the elevated sympathetic activity and risk for cardiovascular morbidity and mortality.18 However, semirecumbent sleeping can be used as conservative treatment in HF patients with OSAS. Rostral fluid shift from the lower extremities to the upper body plays a role in narrowing the upper airway in patients with OSA. Several studies have demonstrated a consistent association between nocturnal fluid shift, increase in neck circumference, and the severity of OSA in patients with HF, hypertension, and end-stage renal disease.7,8,19,20 Yumimo et al19 evaluated 57 patients with HF and sleep apnea (35 obstructive-dominant and 22 central-dominant). The overnight reduction in leg fluid volume correlated inversely with AHI and the overnight change in neck circumference in both groups. Friedman et al20 also showed that AHI was strongly related to the amount of fluid displaced from the leg overnight and increase in neck circumference in both drug-resistant and controlled hypertension patients. In 26
end-stage renal disease patients, it was demonstrated that nocturnal rostral fluid shift was associated significantly with neck circumference and apnea-hypopnea time but not with AHI.8 In contrast to earlier data, we found no correlation between the change in neck and calf circumferences and AHI or oxygen desaturation index. In addition, circumferences of the calf and body weight measured in the morning decreased significantly compared with the measurements at night, as expected, whereas the average neck circumference in the morning was smaller than in the night in both flat and semirecumbent positions. Therefore, the significantly lower value of AHI in the semirecumbent position could not be connected to the neck circumference changes. This might be explained by the fact that a majority of patients (80%) were using diuretics and they lost significant weight during the night. The decreased effect of gravity on the tongue base in the semirecumbent position could be another explanation. Furthermore, we measured the circumferences with a tape measure and did not use objective methods. For all these reasons, the rostral fluid shift hypothesis could not be rejected with the use of the present results. It is known that complex anatomic, physiologic, and neural factors are involved in upper airway collapse in OSAS patients. Study Limitations The present study has a number of limitations. First, we did not design it as a randomized controlled trial, because it was not possible to recruit age-, sex-, BMI-, ejection fraction-, and AHI-matched sleep apnea and HF patients. Therefore, we performed a self-controlled clinical trial in which each patient served as his or her own control. The patients were all in stable clinical status and taking optimal medical therapy. They underwent 2 polysomnographic procedures within 1 week while lying flat and in a semirecumbent position. Anthropometric and polysomnographic parameters of the patient in the flat position were compared with the patient’s parameters in semirecumbent sleeping. Second, we measured the circumference of the neck and calf of the legs with a tape measure. However, there are objective methods such as bioelectrical impedance for leg fluid volume and acoustic pharyngometry for pharyngeal cross-sectional area.8,12 Even so, the measurements were performed by the same technicians, and lines were drawn to ensure that the measurements were made at exactly the same levels. Additionally, the assessment of daily physical activity of the patients was self-reported and was not an hour-by-hour schedule. Sleep apnea patients follow a sedentary lifestyle, and this is related to impaired fluid dynamics in the lower body, particularly the legs.21 We did not evaluate physical activity in detail, but there was no difference between the time spent in the sitting and standing positions the day preceding the sleep studies performed in flat and semirecumbent positions. Furthermore, the volume of urine excreted was not recorded in the study although 80% of the patients were using diuretics and there was a
Effect of Sleep Position on Sleep Apnea in HF Patients
significant weight loss in the morning. Finally, the patients were using different kinds of medications, but standardizing the treatments would not be appropriate owing to the serious comorbidities of the patients. Conclusion The present findings suggest that semirecumbent sleeping may be a promising therapeutic option in the management of HF-related sleep apnea, because we observed highly significant decreases in the indicators of OSAS severity, including AHI and oxygen desaturation index, while semirecumbent sleeping compared with lying flat. CPAP is regarded to be the criterion standard treatment of OSA, but semirecumbent sleep position therapy can be used as an adjuvant to other treatment modalities in patients with HF and OSAS. The role of semirecumbent position therapy, indicators for treatment response, and long-term outcomes should be clarified in large-sample well designed studies in HF patients with OSAS. Acknowledgments The authors thank sleep technicians Bahar Yoruk, Yakup Coskun, and Merve Ozdemir in the Sleep Disorders Laboratory, Department of Chest Diseases, School of Medicine, Ege University, for their valuable help in gathering the data related to the systemic health of the patients. The authors also thank Timur Kose from the Department of Biostatistics, Ege University School of Medicine, for statistical assistance. Disclosures None.
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