Original article 49
Intubation after noninvasive ventilation failure in chronic obstructive pulmonary disease: associated factors at emergency department presentation Johanna P. van Gemerta, Folkert Brijkerb, Marja A. Wittenc and Loek P.H. Leenend Objective Noninvasive ventilation (NIV) is a common practice in acute hypercapnic respiratory failure (AHRF) because of exacerbation of chronic obstructive pulmonary disease (COPD). However, a recent study has shown that patients who require invasive mechanical ventilation (IMV) after failure of NIV experience high mortality rates (up to 30%). Therefore, the aim of this study is to determine the parameters, specifically for emergency department (ED) presentation, associated with the transition from NIV to IMV because of NIV failure. Patients and methods This is a 4-year retrospective cohort study in the EDs of two Dutch hospitals. International Classification of Disease codes were used to identify 139 COPD patients treated with NIV. Those with AHRF (pH limits: 7.25–7.35), a full resuscitation order, and those without a pneumonia were selected for the study (n = 40 with 50 NIV episodes). Parameters in patients treated successfully with NIV were compared with those in patients requiring transition to IMV due to NIV failure. Univariable regression analysis was used and, if P-value less than 0.20, analyses were entered into a multivariable logistic regression analysis model.
Results NIV was successful in 33 (66%) patients, 10 (20%) required transition to IMV, and seven (14%) died. Age over 65 years and a Glasgow Coma Score less than 15 were associated significantly with the transition from NIV to IMV in multivariable analysis (P < 0.05). Conclusion Older age and a low Glasgow Coma Score at ED presentation are factors associated with the transition from NIV to IMV in COPD patients with AHRF. European Journal of Emergency Medicine c 2015 Wolters Kluwer Health, Inc. All 22:49–54 Copyright rights reserved. European Journal of Emergency Medicine 2015, 22:49–54 Keywords: chronic obstructive pulmonary disease, emergency department, noninvasive ventilation a
Department of Internal Medicine, Academic Medical Center, Amsterdam, Department of Pulmonology, Diakonessenhuis, Utrecht, Departments of Emergency Medicine and dSurgery, University Medical Centre, Utrecht, The Netherlands
b c
Correspondence to Johanna P. van Gemert, MD, Department of Internal Medicine, Academic Medical Center, Room No. F4-222, PO Box 22660, 1100 DD Amsterdam, The Netherlands Tel: + 31 062 495 7208; fax: + 31 20 566 4440; e-mail: [email protected] Received 28 November 2013 Accepted 18 February 2014
Introduction Acute exacerbation of chronic obstructive pulmonary disease (COPD) is a common cause of acute hypercapnic respiratory failure (AHRF) in the emergency department (ED). Patients with AHRF might require mechanical ventilation, either by invasive mechanical ventilation (IMV) or by noninvasive ventilation (NIV) [1–3]. As systematic reviews of randomized-controlled trials show that NIV is associated with decreased mortality and intubation rates, NIV is considered a first-line therapy in the management of COPD patients with AHRF [4–8]. However, despite a profound beneficial value in many patients, failure rates of 18–52% have been reported [9–15]. Failure of NIV can result in a dangerous delay in endotracheal intubation, which might adversely affect the outcome [1,16]. A recent large study showed that the mortality rate among patients who required a transition from NIV to IMV because of NIV failure was almost 30%, which is higher than the mortality rate among patients placed on IMV initially [17]. Consequently, there is a need for early recognition of patients at risk for c 2015 Wolters Kluwer Health, Inc. All rights reserved. 0969-9546 Copyright
transition from NIV to IMV. As decisions for this intensive treatment are usually made in the ED setting, factors predicting NIV failure should be available in the ED. Previous studies have not yet focused on emergencyspecific factors for NIV failure [11–14]. Therefore, the aim of this study is to determine parameters in the ED associated with transition from NIV to IMV because of NIV failure in COPD patients with AHRF.
Patients and methods Study setting and population
A retrospective cohort study was carried out in COPD patients with AHRF, admitted between January 2008 and March 2012, to the ED of two hospitals in geographic proximity to and working in close collaboration with each other: a general hospital (Diakonessenhuis Utrecht; ED characteristics: total number of ED presentations 21 000 and pulmonary patients 1000 per year) and a University Hospital (University Medical Center Utrecht; ED characteristics: total number of ED presentations 26 000 DOI: 10.1097/MEJ.0000000000000141
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European Journal of Emergency Medicine 2015, Vol 22 No 1
and pulmonary patients 1600 per year). Patients were identified by International Classification of Diseases codes. AHRF was defined as an atrial pH less than 7.35 with a PaCO2 more than 6.0 kPa at the time of admission to the ED. The diagnosis of COPD was made according to the Global Initiative for Chronic Obstructive Lung Disease (GOLD) guidelines [8]. Only patients with a pH of 7.25–7.35 were included in the study [18,19]. Moreover, only those who received NIV within 24 h from admission to the ED and those with a full resuscitation order were included. Exclusion criteria for NIV therapy were as follows: hemodynamic instability, lack of cooperation, hypercapnic coma, pH less than 7.25, inefficient clearance of secretions, upper airway obstruction, central nervous system disorders, cardiac arrest, myocardial infarction, recent upper gastrointestinal bleeding, and pneumonia as the primary cause of AHRF [18,19]. All patients who fulfilled the inclusion criteria received standard therapy including controlled oxygen, bronchodilators, corticosteroids, and antibiotics in the ED. After admission to the ED, patients were transported to the ICU or the respiratory ward for the initiation of NIV treatment. The Research Ethics Committee of both hospitals approved the study. Noninvasive ventilation
The type of ventilator was adjusted to the setting on the ward, that is, Galileo/G5 (Hamilton Medical, Rhazuns, Switzerland), Servo-1 (Maquet Critical Care, Solna, Sweden), BiPAP Harmony (Philips Healthcare, Eindhoven, the Netherlands). NIV pressures were delivered through a face or a nasal mask. The inspiratory pressure and expiratory pressure were set according to protocol [19]. Successful NIV was defined as clinical improvement leading to successful weaning from the ventilator with the patient’s discharge from hospital. Failure of NIV was defined as the need for IMV or death during admission. Criteria for endotracheal intubation included the following: worsening of arterial blood gases and/or pH in 1–2 h, lack of improvement in arterial blood gases and/ or pH after 4 h, hemodynamic instability, lack of control of airway secretions requiring airway protection, and hypercapnic coma [19].
Table 1
Characteristics of the study groups NIV success (group 1) (n = 33)
Transition to IMV (group 2) (n = 10)
Death (group 3) (n = 7)
64±9 14 (42) 15 (45) 22 (67)
71±8 8 (80) 6 (60) 7 (70)
77±10 6 (86) 4 (57) 4 (57)
27±8 18 (55) 5 (15)
25±3 7 (70) 3 (30)
25±4 2 (29) 3 (43)
8 (24)
3 (30)
5 (71)
105±23 19 (58)
108±19 6 (60)
115±18 6 (86)
27±7 9 (27)
24±8 2 (20)
26±5 1 (14)
4 (12) 79±22 7 (21)
6 (60) 86±26 2 (20)
0 (0) 140±76 5 (71)
6.9±3.5 12 (36) 7.30±0.07 9.5±2.6
8.0±2.6 6 (60) 7.30±0.09 9.8±2.3
14.1±4.4 7 (100) 7.29±0.07 9.8±3.8
11.2±7.7
13.2±12.2
10.8±5.7
31.8±12.6
33.7±7.0
34.3±11.7
15.5±4.3 7±6 10 (30)
15.2±3.9 5±4 1 (10)
17.7±2.8 6±7 2 (29)
4 (12) 7 (21)
3 (30) 2 (20)
0 (0) 2 (29)
0.9±0.4 2.2±0.7 43±15
0.9±0.3 2.2±0.9 43±16
0.9±0.4 2.0±0.6 46±12
Mean age (years) Age > 65 years [n (%)] Male sex [n (%)] Admission to ICU [n (%)] BMI Smoking [n (%)] ADL severe limits [n (%)] Oxygen at home [n (%)] Heart rate (beats/min) Heart rate > 100 beats/ min [n (%)] Respiratory rate Respiratory rate > 30 breaths/min [n (%)] GCS 9–14 [n (%)] Creatinine (mmol/l) Creatinine > 100 mmol/l [n (%)] Urea (mmol/l) Urea > 7 mmol/l [n (%)] pH at admission PaCO2 at admission (kPa) PaO2 at admission (kPa) Bicarbonate at admission (mmol/l) APACHE II Start time NIV (h) NIV treatment before [n (%)] IMV before [n (%)] Cardiogenic pulmonary edema [n(%)] FEV1 (l) VC (l) FEV1/VC (%)
Missing data: smoking (n = 2), VC (n = 2), FEV1 (n = 2). ADL, Activities of Daily Living; APACHE II, Acute Physiology and Chronic Health Evaluation II; FEV1, forced expiratory volume in the first second; GCS, Glasgow Coma Score; IMV, invasive mechanical ventilation; NIV, noninvasive ventilation; VC, vital capacity.
Acute Physiology and Chronic Health Evaluation II (APACHE II) scores were calculated. The primary outcomes were as follows: NIV success (group 1), transition from NIV to IMV (group 2), and death (group 3). NIV failure was defined as transition to IMV or death (group 2 + group 3).
Data collection
The study parameters were based on previous studies and were considered to be reproducible parameters, easily obtained and measured in the ED [11–14]. The following data were collected from the first measurement at ED admission: demographic parameters, hemodynamic parameters, Glasgow Coma Score (GCS), Activities of Daily Living score, arterial blood gas results, blood count, routine chemistry and associated comorbidities, and patient history (Table 1). The Activities of Daily Living score according to Seneff et al. [20] was used. Furthermore, spirometry results were recorded and the baseline
Statistical analysis
All analyses were carried out using SPSS (18.0; SPSS Inc., Chicago, Illinois, USA) for Mac. All variables were first analyzed by univariable logistic regression. Parameters in patients who were treated successfully with NIV (group 1) were compared with those in patients who required transition to IMV (group 2) and with those who failed NIV therapy (group 2 + group 3). All variables with a P-value less than 0.20 by univariable analysis were considered as a trend to statistical
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ED factors associated with NIV failure van Gemert et al. 51
significance and were entered into a multivariable logistic regression analysis model (backward logistic regression) to identify the variables associated with the failure of NIV. A P-value of less than 0.05 was considered significant. Risk factors are expressed as odds ratios with 95% confidence intervals and P-values.
Fig. 1
COPD Patients with AHRF treated with NIV n = 139
Results International Classification of Diseases codes were used to identify 139 COPD patients treated with NIV (Fig. 1). Of these patients identified, those with AHRF (pH limits: 7.25–7.35), with full resuscitation orders, and treated with NIV within 24 h from admission were selected (n = 40 with 50 NIV episodes). Of these patients, 88% were recruited in the Diakonessenhuis and 12% in the University Medical Center Utrecht. NIV therapy was successful in 33 (66%) patients (group 1), 10 (20%) required IMV after initial NIV therapy (group 2), and seven (14%) died (group 3). Finally, three (30%) of the patients in group 2 died after transition to IMV. The patient characteristics are described in Table 1. Univariable analysis
GCS less than 15 and age more than 65 years were significantly (P < 0.05) associated with the transition from NIV to IMV (group 2) in univariable analysis (Table 2). Age more than 65 years and urea more than 7 mmol/l were significantly (P < 0.05) associated with NIV failure (group 2 + group 3) in univariable analysis (Table 2). Multivariable analysis
Age more than 65 years and a GCS less than 15 were significantly associated with the transition from NIV to IMV (group 2) in multivariable analysis (P < 0.05). Age more than 65 years, GCS less than 15, and the use of home oxygen were significantly associated with NIV failure (group 2 + group 3) in multivariable analysis (P < 0.05). These results are shown in Table 3. In patients older than 65 years of age, the NIV failure rate was 50%. In patients with a GCS less than 15, the failure rate was 60%.
Excluded DNI
n = 29
Excluded pH < 7.25
n = 15
Excluded Uncooperative
n=4
Excluded comorbidity Pneumonia
n = 33
CPE
n=3
CNSD
n=3
Pickwick
n=2
Included n = 50
Three-month survival
The survival rate 3 months after admission was 96% in patients successfully treated with NIV and 70% in patients treated with IMV because of NIV failure. Most patients (88%) attended an outpatient pulmonary rehabilitation program (respiratory specialist and nurse followup appointments, psychological support, exercise program, and nutritional support) and 8% of the patients were transferred to a rehabilitation clinic.
Discussion This study focused on ED-specific parameters associated with the transition from NIV to IMV in COPD patients with AHRF. Most importantly, this study shows that age
Flow chart of patients enrolled in the study. AHRF, acute hypercapnic respiratory failure; CNSD, central nervous system disorders; COPD, chronic obstructive pulmonary disease; CPE, cardiogenic pulmonary edema; DNI, do-not-intubate orders; NIV, noninvasive ventilation.
more than 65 years and a GCS less than 15 are associated with a transition from NIV to IMV. As it is now known that patients who require IMV because of NIV failure experience high mortality rates (up to 30%), there is a need for additional predictive parameters in the ED to decide which patients are suitable candidates for NIV treatment and which patients should be intubated immediately [17]. Therefore, the additional value of this
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52 European Journal of Emergency Medicine 2015, Vol 22 No 1
Table 2
Univariable analysis: association between selected parameters and noninvasive ventilation failure Transition to IMV (group 2)
Parameters
P-value
Age > 65 years Male sex BMI Smoking ADL severe limits Oxygen at home Heart rate > 100 beats/min Respiratory rate > 30 breaths/min GCS < 15 (9–14) Creatinine > 100 mmol/l Urea > 7 mmol/l pH at admission PaCO2 at admission PaO2 at admission Bicarbonate at admission APACHE II Start time NIV NIV treatment before IMV before Decompensatio cordis FEV1 VC FEV1/VC
0.032 0.419 0.271 0.496 0.310 0.718 0.892 0.638 0.003 0.934 0.187 0.924 0.788 0.545 0.623 0.833 0.250 0.166 0.204 0.934 0.569 0.997 0.965
NIV failure (death + IMV) (group 2 + group 3)
OR (95% CI) 5.4 0.6 0.9 1.7 2.4 1.4 1.1 0.7 10.9 0.9 2.6 1.0 1.0 1.0 1.0 1.0 0.9 0.3 3.1 0.9 0.6 1.0 1.0
(1.0–29.6) (0.1–2.3) (0.8–1.1) (0.4–7.8) (0.5–12.5) (0.3–6.4) (0.3–4.7) (0.1–3.8) (2.1–56.1) (0.2–5.4) (0.62–11.2) (0.9–1.1) (0.8–1.4) (1.0–1.1) (0.9–1.1) (0.8–1.2) (0.8–1.1) (0.0–2.3) (0.6–17.1) (0.2–5.4) (0.1–4.2) (0.4–2.7) (1.0–1.1)
P-value
OR (95% CI)
0.005 0.370 0.184 0.732 0.111 0.105 0.365 0.442 0.058 0.142 0.006 0.854 0.739 0.683 0.509 0.549 0.401 0.323 0.599 0.852 0.631 0.657 0.783
6.3 0.6 0.9 0.8 3.1 2.8 1.8 0.6 4.0 2.6 5.7 1.0 1.0 1.0 1.0 1.0 1.0 0.5 1.6 1.1 0.7 0.8 1.0
(1.5–26.3) (0.2–1.9) (0.8–1.0) (0.2–2.7) (0.8–12.1) (0.8–9.6) (0.5–6.2) (0.1–2.5) (0.9–16.7) (0.7–9.3) (1.5–21.4) (0.9–1.1) (0.8–1.3) (0.9–1.1) (1.0–1.1) (0.9–1.2) (09–1.1) (0.1–2.1) (0.3–7.9) (0.3–4.6) (0.1–3.4) (0.4–1.9) (1.0–1.1)
ADL, Activities of Daily Living; APACHE II, Acute Physiology and Chronic Health Evaluation II; CI, confidence interval; FEV1, forced expiratory volume in the first second; GCS, Glasgow Coma Score; IMV, invasive mechanical ventilation; NIV, noninvasive ventilation; OR, odds ratio; VC, vital capacity.
Table 3
Multivariable analysis: association between selected parameters and noninvasive ventilation failure Transition to IMV (group 2)
GCS < 15 Age > 65 Oxygen at home
NIV failure (death + IMV) (group 2 + group 3)
P-value
OR (95% CI)
P-value
OR (95% CI)
0.001 0.010
0.04 (0.00–0.4) 12.97 (1.19–141.4)
0.006 0.001 0.011 R2 = 0.448
0.08 (0.01–0.6) 16.0 (2.5–104.7) 7.7 (1.4–41.8)
R2 = 0.454
CI, confidence interval; GCS, Glasgow Coma Score; IMV, invasive mechanical ventilation; NIV, noninvasive ventilation; OR, odds ratio.
study is its important role in decision-making at the first patient contact in the ED. We showed that age and GCS, which are easily obtainable bedside variables, can be useful in making such decisions. Our study showed that older age is associated with the transition from NIV to IMV and with NIV failure as a whole (defined as all patients who died plus all patients who required transition from NIV to IMV), which is comparable with the findings of other studies [21,22]. Older individuals might be prone to NIV failure because of the poor baseline situation, comorbidity, or poor NIV treatment tolerance. However, in a small study of 34 COPD patients aged 65 years or older, NIV was successful in 27 (79%) patients [23]. Although NIV might be used as a ‘rescue’ therapy for patients with donot-intubate orders, our study showed that NIV failure rates are high among older patients with full resuscitation orders. Consequently, with the progressive aging of the population, there is a need to assess whether elderly COPD patients are suitable candidates for NIV.
Multivariate logistic regression identified that a GCS less than 15 was associated with the transition from NIV to IMV and NIV failure as a whole. As we excluded comatose patients, it may be concluded from this study that even patients with a slightly altered level of consciousness are at risk for NIV failure. These patients may be less likely to accept NIV because of poor cooperation. Furthermore, in patients with a low GCS, NIV is considered to be contraindicated because of the risk of pulmonary aspiration. This point of view is supported by two prospective studies involving 1145 patients [13,14]. In contrast, this effect was not found in two smaller studies (n = 100) [11,12]. However, studies are difficult to compare because of heterogeneous inclusion criteria. Patients included in previous studies were elderly patients with limitation to respiratory care and a lower overall GCS, and one of these studies was characterized by a selection bias [11,12]. We observed a relationship between the use of home oxygen and NIV failure. This reported relationship is
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ED factors associated with NIV failure van Gemert et al. 53
unsurprising as home oxygen is used in patients with endstage disease and a poor prognosis. Finally, we found an association between elevated plasma urea levels and NIV failure in univariable analysis. This parameter has not proved to have statistical significance on multivariable analysis, which might be explained by an age-related increase in plasma urea levels [21,24]. Other parameters studied frequently are arterial pH and respiratory rate before NIV initiation [12,13,21,25]. Our results did not confirm a relationship between those parameters and NIV outcome. These discrepancies may be attributed to the inclusion of patients with a pH less than 7.25 in previous studies, whereas we excluded patients with a pH less than 7.25 (according to the guidelines) [19]. Furthermore, unlike previous studies, parameters in our study were measured at ED admission instead of before NIV initiation. In contrast with four previous studies, we did not find a relationship between the APACHE II score and NIV failure [12–14,25]. However, the APACHE II score has not been developed for use outside the ICU and is not very practical for calculation at presentation in the ED. Furthermore, two other studies did not prove such a relationship [15,26]. In this study, the mean time between triage in the ED and NIV initiation ranged from 5 to 7 h. In the participating hospitals, NIV could not be initiated in the ED because of a lack of NIV-trained staff. Therefore, patients were transferred to the respiratory ward or ICU for NIV treatment, after a trial of standard therapy in the ED, which might have prolonged the time interval. The time interval in this study was based on computer registration times, starting with the patient’s arrival in the ED and ending with the time registered in the computer by the nurse when the patient was comfortable on NIV therapy. Consequently, the time interval calculated might be incorrectly prolonged by late registration by the nurse caused by the extra time needed to comfort the patient. Furthermore, the mean time interval may have been prolonged by those patients who initially improved with standard therapy, but deteriorated after a couple of hours, and finally received NIV. However, in line with four other studies, we did not find a relationship between the time from admission to NIV and NIV outcome [11,12,27,28]. In essence, the combination of age more than 65 years and a GCS less than 15 in a patient with COPD with AHRF before initiation of NIV might predict the transition from NIV to IMV. A prospective study is needed to confirm our findings and for the development of a prognostic index on the basis of these parameters. The primary limitations of our study are its low power because of a small sample size and its retrospective designs. Second, we used cut-off values implicit in other prediction rules, which might be less appropriate for NIV failure. Third, as this was the first study of ED-specific
parameters associated with NIV failure, we carefully selected a broad spectrum of study parameters suitable for the ED stetting, on the basis of previous studies involving intensive care patients. Therefore, the sample size to parameter ratio may have resulted in unstable parameter estimates and inadequate power. We have reconstructed an overall picture of ED-specific parameters associated with the transition from NIV to IMV. An older age and a low GCS were associated with the transition from NIV to IMV. These easily obtainable factors can be helpful in selecting appropriate candidates for NIV in the ED. Immediate intubation, instead of NIV, should be considered in those patients at risk for NIV failure. Conclusion
Older age and a low GCS at presentation in the ED are associated with the transition from NIV to IMV in COPD patients with AHRF.
Acknowledgements Conflicts of interest
There are no conflicts of interest.
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Intubation after noninvasive ventilation failure in chronic obstructive pulmonary disease: associated factors at emergency department presentation Johanna P. van Gemerta, Folkert Brijkerb, Marja A. Wittenc and Loek P.H. Leenend Objective Noninvasive ventilation (NIV) is a common practice in acute hypercapnic respiratory failure (AHRF) because of exacerbation of chronic obstructive pulmonary disease (COPD). However, a recent study has shown that patients who require invasive mechanical ventilation (IMV) after failure of NIV experience high mortality rates (up to 30%). Therefore, the aim of this study is to determine the parameters, specifically for emergency department (ED) presentation, associated with the transition from NIV to IMV because of NIV failure. Patients and methods This is a 4-year retrospective cohort study in the EDs of two Dutch hospitals. International Classification of Disease codes were used to identify 139 COPD patients treated with NIV. Those with AHRF (pH limits: 7.25–7.35), a full resuscitation order, and those without a pneumonia were selected for the study (n = 40 with 50 NIV episodes). Parameters in patients treated successfully with NIV were compared with those in patients requiring transition to IMV due to NIV failure. Univariable regression analysis was used and, if P-value less than 0.20, analyses were entered into a multivariable logistic regression analysis model.
Results NIV was successful in 33 (66%) patients, 10 (20%) required transition to IMV, and seven (14%) died. Age over 65 years and a Glasgow Coma Score less than 15 were associated significantly with the transition from NIV to IMV in multivariable analysis (P < 0.05). Conclusion Older age and a low Glasgow Coma Score at ED presentation are factors associated with the transition from NIV to IMV in COPD patients with AHRF. European Journal of Emergency Medicine c 2015 Wolters Kluwer Health, Inc. All 22:49–54 Copyright rights reserved. European Journal of Emergency Medicine 2015, 22:49–54 Keywords: chronic obstructive pulmonary disease, emergency department, noninvasive ventilation a
Department of Internal Medicine, Academic Medical Center, Amsterdam, Department of Pulmonology, Diakonessenhuis, Utrecht, Departments of Emergency Medicine and dSurgery, University Medical Centre, Utrecht, The Netherlands
b c
Correspondence to Johanna P. van Gemert, MD, Department of Internal Medicine, Academic Medical Center, Room No. F4-222, PO Box 22660, 1100 DD Amsterdam, The Netherlands Tel: + 31 062 495 7208; fax: + 31 20 566 4440; e-mail: [email protected] Received 28 November 2013 Accepted 18 February 2014
Introduction Acute exacerbation of chronic obstructive pulmonary disease (COPD) is a common cause of acute hypercapnic respiratory failure (AHRF) in the emergency department (ED). Patients with AHRF might require mechanical ventilation, either by invasive mechanical ventilation (IMV) or by noninvasive ventilation (NIV) [1–3]. As systematic reviews of randomized-controlled trials show that NIV is associated with decreased mortality and intubation rates, NIV is considered a first-line therapy in the management of COPD patients with AHRF [4–8]. However, despite a profound beneficial value in many patients, failure rates of 18–52% have been reported [9–15]. Failure of NIV can result in a dangerous delay in endotracheal intubation, which might adversely affect the outcome [1,16]. A recent large study showed that the mortality rate among patients who required a transition from NIV to IMV because of NIV failure was almost 30%, which is higher than the mortality rate among patients placed on IMV initially [17]. Consequently, there is a need for early recognition of patients at risk for c 2015 Wolters Kluwer Health, Inc. All rights reserved. 0969-9546 Copyright
transition from NIV to IMV. As decisions for this intensive treatment are usually made in the ED setting, factors predicting NIV failure should be available in the ED. Previous studies have not yet focused on emergencyspecific factors for NIV failure [11–14]. Therefore, the aim of this study is to determine parameters in the ED associated with transition from NIV to IMV because of NIV failure in COPD patients with AHRF.
Patients and methods Study setting and population
A retrospective cohort study was carried out in COPD patients with AHRF, admitted between January 2008 and March 2012, to the ED of two hospitals in geographic proximity to and working in close collaboration with each other: a general hospital (Diakonessenhuis Utrecht; ED characteristics: total number of ED presentations 21 000 and pulmonary patients 1000 per year) and a University Hospital (University Medical Center Utrecht; ED characteristics: total number of ED presentations 26 000 DOI: 10.1097/MEJ.0000000000000141
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European Journal of Emergency Medicine 2015, Vol 22 No 1
and pulmonary patients 1600 per year). Patients were identified by International Classification of Diseases codes. AHRF was defined as an atrial pH less than 7.35 with a PaCO2 more than 6.0 kPa at the time of admission to the ED. The diagnosis of COPD was made according to the Global Initiative for Chronic Obstructive Lung Disease (GOLD) guidelines [8]. Only patients with a pH of 7.25–7.35 were included in the study [18,19]. Moreover, only those who received NIV within 24 h from admission to the ED and those with a full resuscitation order were included. Exclusion criteria for NIV therapy were as follows: hemodynamic instability, lack of cooperation, hypercapnic coma, pH less than 7.25, inefficient clearance of secretions, upper airway obstruction, central nervous system disorders, cardiac arrest, myocardial infarction, recent upper gastrointestinal bleeding, and pneumonia as the primary cause of AHRF [18,19]. All patients who fulfilled the inclusion criteria received standard therapy including controlled oxygen, bronchodilators, corticosteroids, and antibiotics in the ED. After admission to the ED, patients were transported to the ICU or the respiratory ward for the initiation of NIV treatment. The Research Ethics Committee of both hospitals approved the study. Noninvasive ventilation
The type of ventilator was adjusted to the setting on the ward, that is, Galileo/G5 (Hamilton Medical, Rhazuns, Switzerland), Servo-1 (Maquet Critical Care, Solna, Sweden), BiPAP Harmony (Philips Healthcare, Eindhoven, the Netherlands). NIV pressures were delivered through a face or a nasal mask. The inspiratory pressure and expiratory pressure were set according to protocol [19]. Successful NIV was defined as clinical improvement leading to successful weaning from the ventilator with the patient’s discharge from hospital. Failure of NIV was defined as the need for IMV or death during admission. Criteria for endotracheal intubation included the following: worsening of arterial blood gases and/or pH in 1–2 h, lack of improvement in arterial blood gases and/ or pH after 4 h, hemodynamic instability, lack of control of airway secretions requiring airway protection, and hypercapnic coma [19].
Table 1
Characteristics of the study groups NIV success (group 1) (n = 33)
Transition to IMV (group 2) (n = 10)
Death (group 3) (n = 7)
64±9 14 (42) 15 (45) 22 (67)
71±8 8 (80) 6 (60) 7 (70)
77±10 6 (86) 4 (57) 4 (57)
27±8 18 (55) 5 (15)
25±3 7 (70) 3 (30)
25±4 2 (29) 3 (43)
8 (24)
3 (30)
5 (71)
105±23 19 (58)
108±19 6 (60)
115±18 6 (86)
27±7 9 (27)
24±8 2 (20)
26±5 1 (14)
4 (12) 79±22 7 (21)
6 (60) 86±26 2 (20)
0 (0) 140±76 5 (71)
6.9±3.5 12 (36) 7.30±0.07 9.5±2.6
8.0±2.6 6 (60) 7.30±0.09 9.8±2.3
14.1±4.4 7 (100) 7.29±0.07 9.8±3.8
11.2±7.7
13.2±12.2
10.8±5.7
31.8±12.6
33.7±7.0
34.3±11.7
15.5±4.3 7±6 10 (30)
15.2±3.9 5±4 1 (10)
17.7±2.8 6±7 2 (29)
4 (12) 7 (21)
3 (30) 2 (20)
0 (0) 2 (29)
0.9±0.4 2.2±0.7 43±15
0.9±0.3 2.2±0.9 43±16
0.9±0.4 2.0±0.6 46±12
Mean age (years) Age > 65 years [n (%)] Male sex [n (%)] Admission to ICU [n (%)] BMI Smoking [n (%)] ADL severe limits [n (%)] Oxygen at home [n (%)] Heart rate (beats/min) Heart rate > 100 beats/ min [n (%)] Respiratory rate Respiratory rate > 30 breaths/min [n (%)] GCS 9–14 [n (%)] Creatinine (mmol/l) Creatinine > 100 mmol/l [n (%)] Urea (mmol/l) Urea > 7 mmol/l [n (%)] pH at admission PaCO2 at admission (kPa) PaO2 at admission (kPa) Bicarbonate at admission (mmol/l) APACHE II Start time NIV (h) NIV treatment before [n (%)] IMV before [n (%)] Cardiogenic pulmonary edema [n(%)] FEV1 (l) VC (l) FEV1/VC (%)
Missing data: smoking (n = 2), VC (n = 2), FEV1 (n = 2). ADL, Activities of Daily Living; APACHE II, Acute Physiology and Chronic Health Evaluation II; FEV1, forced expiratory volume in the first second; GCS, Glasgow Coma Score; IMV, invasive mechanical ventilation; NIV, noninvasive ventilation; VC, vital capacity.
Acute Physiology and Chronic Health Evaluation II (APACHE II) scores were calculated. The primary outcomes were as follows: NIV success (group 1), transition from NIV to IMV (group 2), and death (group 3). NIV failure was defined as transition to IMV or death (group 2 + group 3).
Data collection
The study parameters were based on previous studies and were considered to be reproducible parameters, easily obtained and measured in the ED [11–14]. The following data were collected from the first measurement at ED admission: demographic parameters, hemodynamic parameters, Glasgow Coma Score (GCS), Activities of Daily Living score, arterial blood gas results, blood count, routine chemistry and associated comorbidities, and patient history (Table 1). The Activities of Daily Living score according to Seneff et al. [20] was used. Furthermore, spirometry results were recorded and the baseline
Statistical analysis
All analyses were carried out using SPSS (18.0; SPSS Inc., Chicago, Illinois, USA) for Mac. All variables were first analyzed by univariable logistic regression. Parameters in patients who were treated successfully with NIV (group 1) were compared with those in patients who required transition to IMV (group 2) and with those who failed NIV therapy (group 2 + group 3). All variables with a P-value less than 0.20 by univariable analysis were considered as a trend to statistical
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ED factors associated with NIV failure van Gemert et al. 51
significance and were entered into a multivariable logistic regression analysis model (backward logistic regression) to identify the variables associated with the failure of NIV. A P-value of less than 0.05 was considered significant. Risk factors are expressed as odds ratios with 95% confidence intervals and P-values.
Fig. 1
COPD Patients with AHRF treated with NIV n = 139
Results International Classification of Diseases codes were used to identify 139 COPD patients treated with NIV (Fig. 1). Of these patients identified, those with AHRF (pH limits: 7.25–7.35), with full resuscitation orders, and treated with NIV within 24 h from admission were selected (n = 40 with 50 NIV episodes). Of these patients, 88% were recruited in the Diakonessenhuis and 12% in the University Medical Center Utrecht. NIV therapy was successful in 33 (66%) patients (group 1), 10 (20%) required IMV after initial NIV therapy (group 2), and seven (14%) died (group 3). Finally, three (30%) of the patients in group 2 died after transition to IMV. The patient characteristics are described in Table 1. Univariable analysis
GCS less than 15 and age more than 65 years were significantly (P < 0.05) associated with the transition from NIV to IMV (group 2) in univariable analysis (Table 2). Age more than 65 years and urea more than 7 mmol/l were significantly (P < 0.05) associated with NIV failure (group 2 + group 3) in univariable analysis (Table 2). Multivariable analysis
Age more than 65 years and a GCS less than 15 were significantly associated with the transition from NIV to IMV (group 2) in multivariable analysis (P < 0.05). Age more than 65 years, GCS less than 15, and the use of home oxygen were significantly associated with NIV failure (group 2 + group 3) in multivariable analysis (P < 0.05). These results are shown in Table 3. In patients older than 65 years of age, the NIV failure rate was 50%. In patients with a GCS less than 15, the failure rate was 60%.
Excluded DNI
n = 29
Excluded pH < 7.25
n = 15
Excluded Uncooperative
n=4
Excluded comorbidity Pneumonia
n = 33
CPE
n=3
CNSD
n=3
Pickwick
n=2
Included n = 50
Three-month survival
The survival rate 3 months after admission was 96% in patients successfully treated with NIV and 70% in patients treated with IMV because of NIV failure. Most patients (88%) attended an outpatient pulmonary rehabilitation program (respiratory specialist and nurse followup appointments, psychological support, exercise program, and nutritional support) and 8% of the patients were transferred to a rehabilitation clinic.
Discussion This study focused on ED-specific parameters associated with the transition from NIV to IMV in COPD patients with AHRF. Most importantly, this study shows that age
Flow chart of patients enrolled in the study. AHRF, acute hypercapnic respiratory failure; CNSD, central nervous system disorders; COPD, chronic obstructive pulmonary disease; CPE, cardiogenic pulmonary edema; DNI, do-not-intubate orders; NIV, noninvasive ventilation.
more than 65 years and a GCS less than 15 are associated with a transition from NIV to IMV. As it is now known that patients who require IMV because of NIV failure experience high mortality rates (up to 30%), there is a need for additional predictive parameters in the ED to decide which patients are suitable candidates for NIV treatment and which patients should be intubated immediately [17]. Therefore, the additional value of this
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52 European Journal of Emergency Medicine 2015, Vol 22 No 1
Table 2
Univariable analysis: association between selected parameters and noninvasive ventilation failure Transition to IMV (group 2)
Parameters
P-value
Age > 65 years Male sex BMI Smoking ADL severe limits Oxygen at home Heart rate > 100 beats/min Respiratory rate > 30 breaths/min GCS < 15 (9–14) Creatinine > 100 mmol/l Urea > 7 mmol/l pH at admission PaCO2 at admission PaO2 at admission Bicarbonate at admission APACHE II Start time NIV NIV treatment before IMV before Decompensatio cordis FEV1 VC FEV1/VC
0.032 0.419 0.271 0.496 0.310 0.718 0.892 0.638 0.003 0.934 0.187 0.924 0.788 0.545 0.623 0.833 0.250 0.166 0.204 0.934 0.569 0.997 0.965
NIV failure (death + IMV) (group 2 + group 3)
OR (95% CI) 5.4 0.6 0.9 1.7 2.4 1.4 1.1 0.7 10.9 0.9 2.6 1.0 1.0 1.0 1.0 1.0 0.9 0.3 3.1 0.9 0.6 1.0 1.0
(1.0–29.6) (0.1–2.3) (0.8–1.1) (0.4–7.8) (0.5–12.5) (0.3–6.4) (0.3–4.7) (0.1–3.8) (2.1–56.1) (0.2–5.4) (0.62–11.2) (0.9–1.1) (0.8–1.4) (1.0–1.1) (0.9–1.1) (0.8–1.2) (0.8–1.1) (0.0–2.3) (0.6–17.1) (0.2–5.4) (0.1–4.2) (0.4–2.7) (1.0–1.1)
P-value
OR (95% CI)
0.005 0.370 0.184 0.732 0.111 0.105 0.365 0.442 0.058 0.142 0.006 0.854 0.739 0.683 0.509 0.549 0.401 0.323 0.599 0.852 0.631 0.657 0.783
6.3 0.6 0.9 0.8 3.1 2.8 1.8 0.6 4.0 2.6 5.7 1.0 1.0 1.0 1.0 1.0 1.0 0.5 1.6 1.1 0.7 0.8 1.0
(1.5–26.3) (0.2–1.9) (0.8–1.0) (0.2–2.7) (0.8–12.1) (0.8–9.6) (0.5–6.2) (0.1–2.5) (0.9–16.7) (0.7–9.3) (1.5–21.4) (0.9–1.1) (0.8–1.3) (0.9–1.1) (1.0–1.1) (0.9–1.2) (09–1.1) (0.1–2.1) (0.3–7.9) (0.3–4.6) (0.1–3.4) (0.4–1.9) (1.0–1.1)
ADL, Activities of Daily Living; APACHE II, Acute Physiology and Chronic Health Evaluation II; CI, confidence interval; FEV1, forced expiratory volume in the first second; GCS, Glasgow Coma Score; IMV, invasive mechanical ventilation; NIV, noninvasive ventilation; OR, odds ratio; VC, vital capacity.
Table 3
Multivariable analysis: association between selected parameters and noninvasive ventilation failure Transition to IMV (group 2)
GCS < 15 Age > 65 Oxygen at home
NIV failure (death + IMV) (group 2 + group 3)
P-value
OR (95% CI)
P-value
OR (95% CI)
0.001 0.010
0.04 (0.00–0.4) 12.97 (1.19–141.4)
0.006 0.001 0.011 R2 = 0.448
0.08 (0.01–0.6) 16.0 (2.5–104.7) 7.7 (1.4–41.8)
R2 = 0.454
CI, confidence interval; GCS, Glasgow Coma Score; IMV, invasive mechanical ventilation; NIV, noninvasive ventilation; OR, odds ratio.
study is its important role in decision-making at the first patient contact in the ED. We showed that age and GCS, which are easily obtainable bedside variables, can be useful in making such decisions. Our study showed that older age is associated with the transition from NIV to IMV and with NIV failure as a whole (defined as all patients who died plus all patients who required transition from NIV to IMV), which is comparable with the findings of other studies [21,22]. Older individuals might be prone to NIV failure because of the poor baseline situation, comorbidity, or poor NIV treatment tolerance. However, in a small study of 34 COPD patients aged 65 years or older, NIV was successful in 27 (79%) patients [23]. Although NIV might be used as a ‘rescue’ therapy for patients with donot-intubate orders, our study showed that NIV failure rates are high among older patients with full resuscitation orders. Consequently, with the progressive aging of the population, there is a need to assess whether elderly COPD patients are suitable candidates for NIV.
Multivariate logistic regression identified that a GCS less than 15 was associated with the transition from NIV to IMV and NIV failure as a whole. As we excluded comatose patients, it may be concluded from this study that even patients with a slightly altered level of consciousness are at risk for NIV failure. These patients may be less likely to accept NIV because of poor cooperation. Furthermore, in patients with a low GCS, NIV is considered to be contraindicated because of the risk of pulmonary aspiration. This point of view is supported by two prospective studies involving 1145 patients [13,14]. In contrast, this effect was not found in two smaller studies (n = 100) [11,12]. However, studies are difficult to compare because of heterogeneous inclusion criteria. Patients included in previous studies were elderly patients with limitation to respiratory care and a lower overall GCS, and one of these studies was characterized by a selection bias [11,12]. We observed a relationship between the use of home oxygen and NIV failure. This reported relationship is
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ED factors associated with NIV failure van Gemert et al. 53
unsurprising as home oxygen is used in patients with endstage disease and a poor prognosis. Finally, we found an association between elevated plasma urea levels and NIV failure in univariable analysis. This parameter has not proved to have statistical significance on multivariable analysis, which might be explained by an age-related increase in plasma urea levels [21,24]. Other parameters studied frequently are arterial pH and respiratory rate before NIV initiation [12,13,21,25]. Our results did not confirm a relationship between those parameters and NIV outcome. These discrepancies may be attributed to the inclusion of patients with a pH less than 7.25 in previous studies, whereas we excluded patients with a pH less than 7.25 (according to the guidelines) [19]. Furthermore, unlike previous studies, parameters in our study were measured at ED admission instead of before NIV initiation. In contrast with four previous studies, we did not find a relationship between the APACHE II score and NIV failure [12–14,25]. However, the APACHE II score has not been developed for use outside the ICU and is not very practical for calculation at presentation in the ED. Furthermore, two other studies did not prove such a relationship [15,26]. In this study, the mean time between triage in the ED and NIV initiation ranged from 5 to 7 h. In the participating hospitals, NIV could not be initiated in the ED because of a lack of NIV-trained staff. Therefore, patients were transferred to the respiratory ward or ICU for NIV treatment, after a trial of standard therapy in the ED, which might have prolonged the time interval. The time interval in this study was based on computer registration times, starting with the patient’s arrival in the ED and ending with the time registered in the computer by the nurse when the patient was comfortable on NIV therapy. Consequently, the time interval calculated might be incorrectly prolonged by late registration by the nurse caused by the extra time needed to comfort the patient. Furthermore, the mean time interval may have been prolonged by those patients who initially improved with standard therapy, but deteriorated after a couple of hours, and finally received NIV. However, in line with four other studies, we did not find a relationship between the time from admission to NIV and NIV outcome [11,12,27,28]. In essence, the combination of age more than 65 years and a GCS less than 15 in a patient with COPD with AHRF before initiation of NIV might predict the transition from NIV to IMV. A prospective study is needed to confirm our findings and for the development of a prognostic index on the basis of these parameters. The primary limitations of our study are its low power because of a small sample size and its retrospective designs. Second, we used cut-off values implicit in other prediction rules, which might be less appropriate for NIV failure. Third, as this was the first study of ED-specific
parameters associated with NIV failure, we carefully selected a broad spectrum of study parameters suitable for the ED stetting, on the basis of previous studies involving intensive care patients. Therefore, the sample size to parameter ratio may have resulted in unstable parameter estimates and inadequate power. We have reconstructed an overall picture of ED-specific parameters associated with the transition from NIV to IMV. An older age and a low GCS were associated with the transition from NIV to IMV. These easily obtainable factors can be helpful in selecting appropriate candidates for NIV in the ED. Immediate intubation, instead of NIV, should be considered in those patients at risk for NIV failure. Conclusion
Older age and a low GCS at presentation in the ED are associated with the transition from NIV to IMV in COPD patients with AHRF.
Acknowledgements Conflicts of interest
There are no conflicts of interest.
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