656 J Oral Maxillofac
UPPER AIRWAY IN SNORING
Surg
49:656-659.1991
Improvement in Upper Airway Structure and Function in a Snoring Patient Following Orthogna thic Surgery V. HOFFSTEIN,
PHD, MD,* AND S. WRIGHT, MDt
Orthognathic surgery is one of the therapeutic procedures recently described as being beneficial in treatment of obstructive sleep apnea (OSA).iq2 The majority of patients undergoing this procedure show a significant improvement in OSA, but the mechanism of this improvement remains unclear. This report documents increased patency of the pharyngeal airway and reduction in pharyngeal distensibility in a snoring patient after orthognathic surgery. Based on these results, we suggest that one possible mechanism of improvement in snoring and, perhaps, sleep apnea following this procedure is its beneficial effect on pharyngeal mechanics. Report of a Case A 3 l-year-old man originally presented because of cosmetic concerns involving his receded jaw. He was known to be a heavy snorer, but denied any other symptoms suggestive of sleep apnea. His past medical history was unremarkable. Physical examination showed retrognathia. A three-piece Le Fort I osteotomy was performed with l-mm impaction and 6-mm advancement, as well as shifting of the maxillary midline to the left. In the mandible, a bilateral sagittal split ramus osteotomy was performed. Measurements of upper airway area were performed using the acoustic reflection technique before and 4 months after surgery. This noninvasive technique3.4 is based on the measurements of reflected sound waves that are launched toward the subject, travel along the respiratory tract, and are subsequently reflected back because of changes in acoustic impedance of the airway. The analysis of the incident and reflected sound waves allows construction of a plot of airway area versus distance from the mouth, referred to as the “airway echogram.” An example of such an echogram is seen in Fig 1; the initial 7- to * Head, Respiratory Division, St Michael’s Hospital, Toronto, Ontario, Canada. t Research Fellow, Respiratory Division, The Toronto Hospital, Toronto, Ontario, Canada. Address correspondence and reprint requests to Dr Hoffstein: St Michael’s Hospital, 30 Bond St, Toronto, Ontario, Canada MSB lW8. 0 1991 American geons
Association
0276-2391/91/4906-0014$3.00/O
of Oral and Maxillofacial
Sur-
&cm distance corresponds to the mouthpiece, a large flare in area represents the pharynx, local minimum just distal to the pharynx corresponds to the glottis, and distal to that are the subglottic airways. These airway echograms can be measured as frequently as five times per second during quiet breathing. We used this technique to measure the patient’s pharyngeal and glottic areas during quiet tidal breathing at functional residual capacity (FRC), and at residual volume (RV). At each of these lung volumes we obtained 64 airway echograms, averaged them, and calculated the pharyngeal and glottic areas. Pharyngeal area was defined as the average area of a segment contained between the end of the mouthpiece and the glottis; glottic area was defined as the average area of a 2-cm segment centered on the glottic minimum. To assess the distensibility of the pharyngeal tissues, we measured the patient’s pharyngeal areas at FRC when a positive pressure of 4 cm H,O was applied to the pharynx, and calculated specific pharyngeal compliance (percent change in pharyngeal area per cm H,O pressure) defined as A AiAo A P, where A A is the change in pharyngeal area between 4 cm H,O and atmospheric pressure, Ao is the pharyngeal area at zero (atmospheric) pressure, and A P is 4 cm H,O. The results of preoperative and postoperative measurements of pharyngeal and glottic area are summarized in Table 1 and the echograms are shown in Figure 2. Following surgery, there was a 49% increase in pharyngeal area at residual volume and a 44% increase in glottic area. Concomitant with this change in upper airway structure, there was also improvement in pharyngeal function; specific pharyngeal compliance decreased from 0.120 (cm H,O)-’ to 0.019 (cm H,O)- ‘. At the follow-up visit the patient reported complete disappearance of snoring.
Discussion In this case report we present objective measurements illustrating that orthognathic surgery can be associated with alterations in upper airway structure and function. This has important implications regarding the use of this procedure in treatment of snoring and obstructive sleep apnea. It is a relatively well established fact that patients with snoring and obstructive sleep apnea have abnormal pharyngeal structure and function.4-8 The structural abnormalities comprise reduction in
HOFFSTEIN
AND WRIGHT
657
Area ‘*(cm*) 8-
AREA GW
I
I
10
I
I
I
20 30 40 DISTANCE (CM)
1
L
50
FIGURE 1. A typical airway echogram with the anatomical regions indicated.
cross-sectional area, while the functional abnormalities consist of increased pharyngeal compliance. This renders the pharynx of these patients more susceptible to complete collapse during inspiration. Snoring, which represents incomplete airway occlusion, may be associated with similar abnormalities, but to a lesser degree. This close association between snoring and sleep apnea accounts for the fact that all of the therapeutic procedures used for treatment of sleep apnea also benefit snoring. Uvulopalatopharyngoplasty (UPPP) is the most common surgical procedure used for treatment of snoring and sleep apnea.’ However, the success rate of this procedure for treatment of sleep apnea is only about 50%,” presumably because many patients with this disorder exhibit several abnormal anatomical craninofacial landmarks, causing subtle abnormalities at multiple sites along the upper airway. This led to the development of other surgical approaches to treatment sleep apnea, involving the maxilla, mandible, and hyoid bone.‘,2 The patients most likely to benefit from orthognathic surgery usually are those with a moderate degree of skeletal craniofacial deficiencies, such as our patient who had retrognathia. Maxillomandibular advancement. when used in Tablo 1. PrmoPwative and Postoperative Size of Pfmyngeal8nd Qlottic Areas Preoperative Pharyngeal area FRC (Pm = 0) FRC (Pm = 4) RV Glottic area FRC RV Specific pharyngeal compliance
(cm*)
Postoperative
(cm’)
5.5 IT 0.3 7.2 + 0.9 3.9 2 0.1
6.0 r 0.4 6.3 + 0.3 5.8 r 0.1
1.8 2 0.2 1.7 f 0.2
2.6 ? 0.2 2.2 2 0.2
0.120 (cm H,O)-’
0.019 (cm H,O)-’
Abbreviations: FRC, functional residual capacity; Pm, mouth pressure: RV, residual volume.
8 FIGURE 2. Airway echograms after surgery.
40 30 Distance (cm) at RV measured
50 before and
selected surgical candidates, can lead to impressive improvement in sleep apnea. Guilleminault et al 2 found a dramatic reduction in the respiratory disturbance index from 66 to 9 in 18 patients who underwent orthognathic surgery and hyoid advancement. The reason for this improvement is not clear, but is thought to be due to increased patency of the upper airway, demonstrated by the cephalometric measurements in some isolated cases. The results presented in this case report indicate that orthognathic surgery can be associated with improvement in phaymgeal patency and distensibility-the two properties of pharyngeal mechanics found to be abnormal in patients with snoring and OSA. This most likely led to the reduction in turbulent flow during breathing and accounted for the resolution of snoring. Although the precise pathogenesis of snoring is incompletey understood, this case suggests that static and dynamic properties of the upper airway may be a contributing factor. In selected cases presenting with definite anatomical abnormality involving the bony structures of the face, correction of these abnormalities results in the improvement in airway structure and disappearance of snoring or apnea. Acknowledgment We wish to thank Dr W. Dobrovolsky for performing the surgery and discussing the case.
References I. Riley RW, Powell N, Guilleminault C: Current surgical concepts for treating obstructive sleep apnea syndrome. J Oral Maxillofac Surg 45: 149, 1987 2. Guilleminault C, Quera-Salva MA, Powell NB, et al: Maxilomandibular surgery for obstructive sleep apnea. Eur Respir J 2:604, 1989 3. Fredberg JJ, Wohl MEB, Glass GM, et al: Airway area by acoustic reflections measured at the mouth. J Appl Physiol 48:749, 1980 4. Rivlin J, Hoffstein V, Kalbfleish J, et al. Upper airway morphology in patients with idiopathic obstructive sleep apnea. Am Rev Respir Dis 129:355, 1984 5. Haponik EF. Smith PL, Bohlman ME, et al: Computerized
DISCUSSION
tomography in obstructive sleep apnea. Am Rev Respir Dis 127:221, 1983 6. Bradley TD, Brown IB, Grossman RF, et al: Pharyngeal size in snorers, nonsnorers, and patients with obstructive sleep apnea. N Engl J Med 315:1327, 1986 7. Brown I, Bradley TD, Zamel N, et al: Pharyngeal compliance in snoring subjects with and without obstructive sleep apnea. Am Rev Respir Dis 132:211, 1985
J Oral Maxillotac
8. Issa F. Sullivan CE: Upper airway closing pressures in snorers. J Appl Physiol 57528, 1984 9. Fujita S, Conway W, Zorick F, et al: Surgical correction of anatomic abnormalities in obstructive sleep apnea syndrome. Uvulopalatopharyngoplasty. Otolaryngol Head Neck Surg 89:923, 1981 10. Conway W, Fujita S, Zorick F, et al: Uvulopalatopharyngoplasty. One-year follow up. Chest 88:385, 1985
Surg
49:658.1991
Discussion Improvement in Upper Airway Structure and Function in a Snoring Patient Following Orthognathic Surgery Peter D. Waite, MPH, DDS, MD The University of Alabama School of Dentistry, Birmingham
This article describes a very interesting application of a noninvasive technique to evaluate pharyngeal changes. The method (acoustic reflection technique) is a modilication of ultrasound. Low-frequency sound waves are projected from a mouthpiece and reflections of acoustic disturbances are used to determine airway diameter.‘** This technique has been correlated in dogs and computed tomography (CT) scans in humans3 Maxillomandibular advancement surgery increases the upper airway diameter and has been shown to be the most successful surgical treatment for obstructive sleep apnea.4 Maxillomandibular advancement seems logical in the treatment of snoring and upper airway obstruction; however, the exact anatomic change responsible for curing obstructive sleep apnea is unknown. Because the upper airway and pharynx are dynamic structures and extremely variable, specific measurement with radiographs is difficult to use in evaluating preoperative and postoperative changes. The acoustic reflection method thus may have significant potential in evaluating surgical results in patients with obstructive sleep apnea because it is not a static examination, and allows measurement during function. However, because this is only a single case study of a snoring patient who did not have a full polysomnogram, further work needs to be done and correlations with polysomnography made before the efficacy of the method can be established. It has been used in small series of cases involving uvulopalatopharyngoplasty.’ As seen in Table 1, the pharyngeal area is significantly variable, depending on the phases of respiration. It appears that following surgery, residual volume increased 49%. However, with a pressure of 4 cm of water, the space actually showed a 12% decrease in surface area.
This implies that following surgery, the compliance of the pharynx was decreased and that it did not respond normally. Based on cephalometric studies and CT scans in other patients, the posterior airway space increases have been significantly greater than those demonstrated in this case.4 Unfortunately, the amount of maxillary and mandibular advancement is not provided nor is its correlation with the posterior airway space in the cephalogram. This case presentation is a valuable contribution to the literature in that it introduces a noninvasive method of evaluating upper airway space under dynamic function following orthognathic surgery. It also has application for evaluating surgical treatment of obstructive sleep apnea. Research in this area is necessary for improved treatment planning and determination of the amount of maxillomandibular advancement. In future studies, this method should be correlated with the amount of maxillomandibular advancement and with the results of the nocturnal polysomnogram. I suspect this method is superior to routine cephalometric evaluation of the posterior airway space, but it should be correlated with the respiratory index in obstructive sleep apnea. I look forward to seeing this method used in future research designs.
References 1. Fredberg JJ, Wohl MEB, Glass GM, et al: Airway area by acoustic reflections measured at the mouth. J Appl Physiol 48:749, 1980 (suppl) 2. Jackson AC, Butler JP, Millet FJ, et al: Airway geometry by analysis of acoustic pulse response measurements. J Appl Physiol43:523, 1977 3. Jackson AC, Krevan JR: Tracheal cross sectional areas from acoustic reflections in dogs. J Appl Physiol 57:351, 1984 4. Waite PD, Wooten V, Lachner J, et al: Maxillomandibular advancement surgery in 23 patients with obstructive sleep apnea syndrome. J Oral Maxillofac Surg 47: 1256, 1989 5. Wright S, Haight J, Zamel N, et al: Changes in pharyngeal properties after uvulopalatopharyngoplasty. Laryngoscope 99:62, 1989
UPPER AIRWAY IN SNORING
Surg
49:656-659.1991
Improvement in Upper Airway Structure and Function in a Snoring Patient Following Orthogna thic Surgery V. HOFFSTEIN,
PHD, MD,* AND S. WRIGHT, MDt
Orthognathic surgery is one of the therapeutic procedures recently described as being beneficial in treatment of obstructive sleep apnea (OSA).iq2 The majority of patients undergoing this procedure show a significant improvement in OSA, but the mechanism of this improvement remains unclear. This report documents increased patency of the pharyngeal airway and reduction in pharyngeal distensibility in a snoring patient after orthognathic surgery. Based on these results, we suggest that one possible mechanism of improvement in snoring and, perhaps, sleep apnea following this procedure is its beneficial effect on pharyngeal mechanics. Report of a Case A 3 l-year-old man originally presented because of cosmetic concerns involving his receded jaw. He was known to be a heavy snorer, but denied any other symptoms suggestive of sleep apnea. His past medical history was unremarkable. Physical examination showed retrognathia. A three-piece Le Fort I osteotomy was performed with l-mm impaction and 6-mm advancement, as well as shifting of the maxillary midline to the left. In the mandible, a bilateral sagittal split ramus osteotomy was performed. Measurements of upper airway area were performed using the acoustic reflection technique before and 4 months after surgery. This noninvasive technique3.4 is based on the measurements of reflected sound waves that are launched toward the subject, travel along the respiratory tract, and are subsequently reflected back because of changes in acoustic impedance of the airway. The analysis of the incident and reflected sound waves allows construction of a plot of airway area versus distance from the mouth, referred to as the “airway echogram.” An example of such an echogram is seen in Fig 1; the initial 7- to * Head, Respiratory Division, St Michael’s Hospital, Toronto, Ontario, Canada. t Research Fellow, Respiratory Division, The Toronto Hospital, Toronto, Ontario, Canada. Address correspondence and reprint requests to Dr Hoffstein: St Michael’s Hospital, 30 Bond St, Toronto, Ontario, Canada MSB lW8. 0 1991 American geons
Association
0276-2391/91/4906-0014$3.00/O
of Oral and Maxillofacial
Sur-
&cm distance corresponds to the mouthpiece, a large flare in area represents the pharynx, local minimum just distal to the pharynx corresponds to the glottis, and distal to that are the subglottic airways. These airway echograms can be measured as frequently as five times per second during quiet breathing. We used this technique to measure the patient’s pharyngeal and glottic areas during quiet tidal breathing at functional residual capacity (FRC), and at residual volume (RV). At each of these lung volumes we obtained 64 airway echograms, averaged them, and calculated the pharyngeal and glottic areas. Pharyngeal area was defined as the average area of a segment contained between the end of the mouthpiece and the glottis; glottic area was defined as the average area of a 2-cm segment centered on the glottic minimum. To assess the distensibility of the pharyngeal tissues, we measured the patient’s pharyngeal areas at FRC when a positive pressure of 4 cm H,O was applied to the pharynx, and calculated specific pharyngeal compliance (percent change in pharyngeal area per cm H,O pressure) defined as A AiAo A P, where A A is the change in pharyngeal area between 4 cm H,O and atmospheric pressure, Ao is the pharyngeal area at zero (atmospheric) pressure, and A P is 4 cm H,O. The results of preoperative and postoperative measurements of pharyngeal and glottic area are summarized in Table 1 and the echograms are shown in Figure 2. Following surgery, there was a 49% increase in pharyngeal area at residual volume and a 44% increase in glottic area. Concomitant with this change in upper airway structure, there was also improvement in pharyngeal function; specific pharyngeal compliance decreased from 0.120 (cm H,O)-’ to 0.019 (cm H,O)- ‘. At the follow-up visit the patient reported complete disappearance of snoring.
Discussion In this case report we present objective measurements illustrating that orthognathic surgery can be associated with alterations in upper airway structure and function. This has important implications regarding the use of this procedure in treatment of snoring and obstructive sleep apnea. It is a relatively well established fact that patients with snoring and obstructive sleep apnea have abnormal pharyngeal structure and function.4-8 The structural abnormalities comprise reduction in
HOFFSTEIN
AND WRIGHT
657
Area ‘*(cm*) 8-
AREA GW
I
I
10
I
I
I
20 30 40 DISTANCE (CM)
1
L
50
FIGURE 1. A typical airway echogram with the anatomical regions indicated.
cross-sectional area, while the functional abnormalities consist of increased pharyngeal compliance. This renders the pharynx of these patients more susceptible to complete collapse during inspiration. Snoring, which represents incomplete airway occlusion, may be associated with similar abnormalities, but to a lesser degree. This close association between snoring and sleep apnea accounts for the fact that all of the therapeutic procedures used for treatment of sleep apnea also benefit snoring. Uvulopalatopharyngoplasty (UPPP) is the most common surgical procedure used for treatment of snoring and sleep apnea.’ However, the success rate of this procedure for treatment of sleep apnea is only about 50%,” presumably because many patients with this disorder exhibit several abnormal anatomical craninofacial landmarks, causing subtle abnormalities at multiple sites along the upper airway. This led to the development of other surgical approaches to treatment sleep apnea, involving the maxilla, mandible, and hyoid bone.‘,2 The patients most likely to benefit from orthognathic surgery usually are those with a moderate degree of skeletal craniofacial deficiencies, such as our patient who had retrognathia. Maxillomandibular advancement. when used in Tablo 1. PrmoPwative and Postoperative Size of Pfmyngeal8nd Qlottic Areas Preoperative Pharyngeal area FRC (Pm = 0) FRC (Pm = 4) RV Glottic area FRC RV Specific pharyngeal compliance
(cm*)
Postoperative
(cm’)
5.5 IT 0.3 7.2 + 0.9 3.9 2 0.1
6.0 r 0.4 6.3 + 0.3 5.8 r 0.1
1.8 2 0.2 1.7 f 0.2
2.6 ? 0.2 2.2 2 0.2
0.120 (cm H,O)-’
0.019 (cm H,O)-’
Abbreviations: FRC, functional residual capacity; Pm, mouth pressure: RV, residual volume.
8 FIGURE 2. Airway echograms after surgery.
40 30 Distance (cm) at RV measured
50 before and
selected surgical candidates, can lead to impressive improvement in sleep apnea. Guilleminault et al 2 found a dramatic reduction in the respiratory disturbance index from 66 to 9 in 18 patients who underwent orthognathic surgery and hyoid advancement. The reason for this improvement is not clear, but is thought to be due to increased patency of the upper airway, demonstrated by the cephalometric measurements in some isolated cases. The results presented in this case report indicate that orthognathic surgery can be associated with improvement in phaymgeal patency and distensibility-the two properties of pharyngeal mechanics found to be abnormal in patients with snoring and OSA. This most likely led to the reduction in turbulent flow during breathing and accounted for the resolution of snoring. Although the precise pathogenesis of snoring is incompletey understood, this case suggests that static and dynamic properties of the upper airway may be a contributing factor. In selected cases presenting with definite anatomical abnormality involving the bony structures of the face, correction of these abnormalities results in the improvement in airway structure and disappearance of snoring or apnea. Acknowledgment We wish to thank Dr W. Dobrovolsky for performing the surgery and discussing the case.
References I. Riley RW, Powell N, Guilleminault C: Current surgical concepts for treating obstructive sleep apnea syndrome. J Oral Maxillofac Surg 45: 149, 1987 2. Guilleminault C, Quera-Salva MA, Powell NB, et al: Maxilomandibular surgery for obstructive sleep apnea. Eur Respir J 2:604, 1989 3. Fredberg JJ, Wohl MEB, Glass GM, et al: Airway area by acoustic reflections measured at the mouth. J Appl Physiol 48:749, 1980 4. Rivlin J, Hoffstein V, Kalbfleish J, et al. Upper airway morphology in patients with idiopathic obstructive sleep apnea. Am Rev Respir Dis 129:355, 1984 5. Haponik EF. Smith PL, Bohlman ME, et al: Computerized
DISCUSSION
tomography in obstructive sleep apnea. Am Rev Respir Dis 127:221, 1983 6. Bradley TD, Brown IB, Grossman RF, et al: Pharyngeal size in snorers, nonsnorers, and patients with obstructive sleep apnea. N Engl J Med 315:1327, 1986 7. Brown I, Bradley TD, Zamel N, et al: Pharyngeal compliance in snoring subjects with and without obstructive sleep apnea. Am Rev Respir Dis 132:211, 1985
J Oral Maxillotac
8. Issa F. Sullivan CE: Upper airway closing pressures in snorers. J Appl Physiol 57528, 1984 9. Fujita S, Conway W, Zorick F, et al: Surgical correction of anatomic abnormalities in obstructive sleep apnea syndrome. Uvulopalatopharyngoplasty. Otolaryngol Head Neck Surg 89:923, 1981 10. Conway W, Fujita S, Zorick F, et al: Uvulopalatopharyngoplasty. One-year follow up. Chest 88:385, 1985
Surg
49:658.1991
Discussion Improvement in Upper Airway Structure and Function in a Snoring Patient Following Orthognathic Surgery Peter D. Waite, MPH, DDS, MD The University of Alabama School of Dentistry, Birmingham
This article describes a very interesting application of a noninvasive technique to evaluate pharyngeal changes. The method (acoustic reflection technique) is a modilication of ultrasound. Low-frequency sound waves are projected from a mouthpiece and reflections of acoustic disturbances are used to determine airway diameter.‘** This technique has been correlated in dogs and computed tomography (CT) scans in humans3 Maxillomandibular advancement surgery increases the upper airway diameter and has been shown to be the most successful surgical treatment for obstructive sleep apnea.4 Maxillomandibular advancement seems logical in the treatment of snoring and upper airway obstruction; however, the exact anatomic change responsible for curing obstructive sleep apnea is unknown. Because the upper airway and pharynx are dynamic structures and extremely variable, specific measurement with radiographs is difficult to use in evaluating preoperative and postoperative changes. The acoustic reflection method thus may have significant potential in evaluating surgical results in patients with obstructive sleep apnea because it is not a static examination, and allows measurement during function. However, because this is only a single case study of a snoring patient who did not have a full polysomnogram, further work needs to be done and correlations with polysomnography made before the efficacy of the method can be established. It has been used in small series of cases involving uvulopalatopharyngoplasty.’ As seen in Table 1, the pharyngeal area is significantly variable, depending on the phases of respiration. It appears that following surgery, residual volume increased 49%. However, with a pressure of 4 cm of water, the space actually showed a 12% decrease in surface area.
This implies that following surgery, the compliance of the pharynx was decreased and that it did not respond normally. Based on cephalometric studies and CT scans in other patients, the posterior airway space increases have been significantly greater than those demonstrated in this case.4 Unfortunately, the amount of maxillary and mandibular advancement is not provided nor is its correlation with the posterior airway space in the cephalogram. This case presentation is a valuable contribution to the literature in that it introduces a noninvasive method of evaluating upper airway space under dynamic function following orthognathic surgery. It also has application for evaluating surgical treatment of obstructive sleep apnea. Research in this area is necessary for improved treatment planning and determination of the amount of maxillomandibular advancement. In future studies, this method should be correlated with the amount of maxillomandibular advancement and with the results of the nocturnal polysomnogram. I suspect this method is superior to routine cephalometric evaluation of the posterior airway space, but it should be correlated with the respiratory index in obstructive sleep apnea. I look forward to seeing this method used in future research designs.
References 1. Fredberg JJ, Wohl MEB, Glass GM, et al: Airway area by acoustic reflections measured at the mouth. J Appl Physiol 48:749, 1980 (suppl) 2. Jackson AC, Butler JP, Millet FJ, et al: Airway geometry by analysis of acoustic pulse response measurements. J Appl Physiol43:523, 1977 3. Jackson AC, Krevan JR: Tracheal cross sectional areas from acoustic reflections in dogs. J Appl Physiol 57:351, 1984 4. Waite PD, Wooten V, Lachner J, et al: Maxillomandibular advancement surgery in 23 patients with obstructive sleep apnea syndrome. J Oral Maxillofac Surg 47: 1256, 1989 5. Wright S, Haight J, Zamel N, et al: Changes in pharyngeal properties after uvulopalatopharyngoplasty. Laryngoscope 99:62, 1989
