Oral-Nasal Continuous Positive Airway Pressure as a Treatment for Obstructive Sleep Apnea

Oral-Nasal Continuous Positive Airway Pressure as a Treatment for Obstructive Sleep Apnea* Glen L. Prosise, B.A.; and Richard B. Berry, M.D., F.C.C.P. The effect of continuous positive airway pressure (CP AP) applied via a mask covering the nose and mouth (oralnasal CPAP=ONCPAP) on obstructive sleep apnea (OSA) was studied in ten male patients with a mean ( ± SD) age of 48.1 ± 11.1 years who could not tolerate nasal CPAP (NCPAP) due to nasal congestion. Using ONCPAP at pressures of 11.0 ± 4.5 em H20, the apnea+hypopnea index was reduced from 58.3 ± 22.3 (baseline night) to 5.2 ± 1.6 events per hour (ONCPAP night) (p<0.001). Five of these patients were studied on a subsequent night with a dual chamber mask allowing separate measurement of nasal and oral flow. All patients had combined oral and nasal flow at times during the night, but the fraction of time spent with this breathing pattern was lower during sleep than wakefulness. In a separate study, we compared the effects of a therapeutic level of CPAP pressure (12.8 ± 2.5 em H 20) applied through a nasal mask (NCPAP) and ONCPAP in a different group

of patients (mean age 60 ± 14.6 years) with moderate to severe OSA using NCPAP on a long-term basis. The apnea-hypopnea indexes on NCPAP nights (7 .2 ± 3.5) and ONCPAP nights (7.6±4.9 events per hour of sleep) were very similar. We conclude that ONCPAP may be a reasonable treatment alternative in patients who cannot tolerate NCPAP due to nasal congestion and that the pressure required to maintain upper airway patency may be similar to the level required using NCPAP. (Chest 1994; 106:180-86)

Nasal continuous positive airway pressure (NCPAP) is the standard therapy for moderate to severe obstructive sleep apnea (OSA) . This therapy is very effective in reducing the frequency of apnea, improving sleep quality, and improving the sym ptoms of daytime sleepiness. 1·2 Unfortunately, the therapy is tolerated on a long-term basis by only 60 to 80 percent of patients. 3-6 There are multiple reasons patients may not tolerate NCPAP such as claustrophobia, mask discomfort, or mucosal dryness. Occasionally patients may not tolerate nasal CPAP due to discomfort involved with breathing totally through the nasal route. Such patients usually have nasal congestion (partial obstruction) present either at baseline or developing during therapy with NCp AP. Although attempts at preventing or minimizing the nasal congestion such as inhaled nasal steroids or decongestants will work in many patients with this problem, a few will continue to have difficulty using NCPAP. Such patients frequently breathe orally at least part of the time during the night. We hypothesized that CPAP applied via a mask

covering the nose and mouth would be better tolerated by patients who found breathing through the nose alone uncomfortable. Expiratory positive airway pressure (EP AP) applied via a full-face mask has been shown to improve but not eliminate obstructive apneas.7 Conversely, others have suggested that CPAP applied via a full-face mask will not result in a patent upper airway during sleep. 8•9 To determine if CP AP applied via a mask covering both the nose and mouth (oral-nasal CPAP= ONCPAP) would provide a treatment alternative in patients with nasal congestion or obstruction, we performed a CP AP trial using a full-face mask in patients with moderate to severe OSA who could not tolerate NCPAP due to nasal obstruction. In another group of patients with OSA who had been using NCPAP on a long-term basis, we compared the effectiveness of a therapeutic level of NCPAP pressure with the same level of pressure applied via a mask covering both the nose and mouth.

*From the Department of Medicine, Long Beach Veterans Medical Center, University of California Irvine, Long Beach, California. These data were presented in part at the annual meeting, American Thoracic Society, San Francisco, May 18, 1993. Manuscript received September 28, 1992; revision accepted November 29, 1993. Reprint requests: Dr. Berry, Pulmonary Section lllP, Long Beach VA Medical Center, Long Beach, CA 90822

180

CPAP=continuous positive airway pressure; EPAP= expiratory positive airway pressure; NCPAP=nasal CPAP; ONCPAP=oral-nasal CPAP; OSA =obstructive sleep apnea; REM=rapid eye movement; SPT=sleep period time=time from first sleep until final awakening; TST=total sleep time

METHODS

In part 1 of the study, ten male patients with moderate to severe OSA who were unable to tolerate NCPAP due to nasal obstruction were given a trial of ONCPAP. A baseline all-night sleep study was performed as part of their clinical evaluation. If they were unable to tolerate NCPAP on a subsequent night, they were enrolled in the study. On the first night (ONCPAP titration night), the CP AP level was titrated upward until an optimum level of CP AP was reached (prevention of apnea and hypopnea). On the Oral-Nasal CPAP for Obstructive Sleep Apnea (Prosise, Berry)

second night (designated ONCPAP night), the patients slept for the entire night at that level of CPAP. The results of the second night of ONCPAP were compared with the baseline sleep study. Five of these patients were restudied with a dual-chamber mask that allowed separate measurement of oral and nasal flow during CP AP to determine the relative amounts of nasal and oral flow. In part 2 of the study, five patients with moderate to severe OSA who were undergoing long-term treatment with NCPAP were studied to see if a given level of CP AP would be less effective if applied by a mask covering the nose and mouth. Patients were studied on an adaptation night and two consecutive study nights. On the adaptation night, the level of NCPAP was titrated upward until apnea and hypopnea were no longer present. On the following two nights, patients slept with either NCP AP or ONCPAP at the same level of CPAP documented to be effective on the adaptation night. The order of the types of CPAP was randomized. The efficacy of NCPAP and ONCPAP was compared. All patients participating in parts l and 2 of the study gave informed consent and the project was approved by the Institutional Review Board of our hospital. The presence and stage of sleep were detected by monitoring central and occipital EEG derivations (C4-Al, 02-Al), two electro-oculographic derivations, and surface chin electromyographic activity using standard methods. 10 Arterial oxygen saturation was continuously measured by pulse oximetry and an ECG lead was also monitored. Respiratory effort was detected by chest and abdominal bands using respiratory inductance plethysmography. Airflow was detected by a thermocouple inside the mask and tidal volume was estimated by monitoring changes in the plethysmography Vsum tracing 11 On CPAP nights, mask pressure (either nasal or oral/ nasal) was continuously measured using a pressure transducer (Validyne) and a water manometer. Continuous positive airway pressure was provided using a routine nasal CP AP flow generator (Sleep Easy Plus or BIPAP-SD, Respironics, Murrysville, Pa). These machines were equipped with a digital readout of the airway pressure. On NCPAP nights, a routine clinical NCPAP mask (Respironics) was utilized. On ONCPAP nights, a customized mask covering the nose and mouth was used to administer CPAP (Fig 1). This fullface mask was constructed by covering the open side of a large full face mask (modell33122, Puritan-Bennett, Carlsbad, Calif)

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with a sheath of latex rubber. An opening was then cut in the rubber sheath to a size that would just fit over the nose and mouth of each patient. When under pressure, the latex film bulged outward making a seal against the face. Both masks were held in place by head straps. Rebreathing of C02 was prevented in both CP AP modes by using a controlled leak. A whisper valve (Respironics) was used on NCPAP nights and on ONCPAP nights an 8-mm hole was drilled in the mask. This size hole is used on commercially available CP AP masks (Healthdyne, Marietta, Ga). Five of the subjects were restudied on a single night using a dual-chamber mask that separated the nasal and oral compartments. A full-face CPAP mask with an air cushion at the maskface interface and two ports (Vital signs, Totowa, NJ) was customized. A septum between the superior and inferior mask ports was constructed with Silastic polymer (dividing the mask into nasal and oral compartments) and the one-way valves in the ports were removed. When the septum was positioned below the nares the superior port/ chamber provided nasal flow and the inferior port/ chamber provided oral flow. Pneumotachographs were placed in each port to separately measure nasal and oral flow. Fresh polymer was applied to the mask and septum prior to being placed on the subjects. Once the polymer dried, the airtightness of both chambers was tested. A Yadapter was then used to connect both compartments to a common hose leading to a CPAP machine (BIPAP-SD, Respironics Murrysville, Pa). The CP AP pressure was monitored proximal to the Y connector. The CP AP mode was used in four patients but one patient was treated with bilevel CP AP. The level of CPAP was rapidly titrated upward until the upper airway was stabilized.

Data Analysis Sleep was staged in 30-s epochs using standard criteria.10 The sleep period time (SPT) was defined as the total sleep time (TST) plus minutes of wakefulness after sleep onset but prior to the final awakening. Respiratory events were noted using the following definitions. An apnea was defined as a absence of airflow (or change in the Vsum tracing) for ;:o:IO s. A hypopnea was defined as a reduction in tidal volume to less than 50 percent of baseline and associated with a fall in arterial oxygen saturation of ;:::4 percent. The apnea + hypopnea index was the total number of

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events per hour of sleep. In part 1 of the study, the sleep and respiratory variables were compared between the baseline and second ONCPAP nights using the paired t test. In the five patients who were restudied with the dual-chamber full-face mask, the ratio of peak flow into the oral and nasal compartments was measured every fifth breath on every epoch while awake and every fifth epoch during sleep to estimate the relative importance of the two routes of breathing. The number of epochs in which only nasal or oral flow was present was also determined. The apnea and hypopnea index was also determined. In part 2 of the study, the sleep and respiratory variables were compared between the NCPAP and ONCPAP nights using the paired t test. A p<0.05 was assumed to represent statistical significance. RESULTS

The ten male patients who participated in part 1 of the study ranged in age from 39 to 71 years (mean± SD=48.1 ± 11.1 years) and weighed 157.6±37.2 percent of ideal body weight. 12 They had moderate to severe OSA with an apnea + hypopnea index on the baseline study night that ranged from 24.2 to 79.7 events per hour of sleep with a mean of 58.3 ± 22.3 events per hour of sleep (Fig 2). All ten patients complained of chronic symptoms of nasal congestion or rhinitis. At the time of study, none were using medications known to increase nasal congestion. No patient was using inhaled nasal steroids or oral decongestants at the time of the study. The level of CP AP found to prevent apnea on the ONCPAP titration night ranged from 5 to 16 em H 20 with a mean pressure of 12.1 ± 3.4 em H20. On the ONCPAP night, this pressure level reduced the mean apnea+hypopnea index to 5.2± 1.6 events per hour (p<0.001). The apnea+hypopnea indices for the individual patients are shown in Figure 2. The mean TST was higher on the ONCPAP night (368.6±50.7 vs 308.9 ± 65.3 min, p<0.005). The amount of slowwave sleep also increased (86.5 ± 53.1 vs 27.5 ± 35.8 mins, p<0.005). Similarly, the mean amount of rapid 182

eye movement (REM) sleep was also greater on the ONCPAP nights (93±30.1 vs 49.7±29.5 mins, p<0.005) . The SPTs on the baseline and ONCPAP nights were 377.0±39.2 min and 422.6±36.6 min, respectively (p<0.01) . The fraction of the SPT spent in the different sleep stages is depicted in Figure 3. Subjects spent a smaller fraction of time in stage 1 sleep (p<0.01) on ONCPAP nights and a greater percentage of time in slow-wave sleep (p<0.01) and REM sleep (p<0.01). Using the customized mask, we were able to achieve an adequate seal without undue tightness of the head straps. However, the cheeks did tend to "bulge out" in patients requiring higher pressures. Although this caused some discomfort, the patients found this tolerable. All patients were subsequently treated with inhaled nasal steroids and/ or bedtime oral decongestants. Six were eventually converted to NCPAP because of the lack of commercially available ONCPAP masks. However, four were unable to tolerate NCPAP and continue to use ONCPAP on a nightly basis for at least 6 h per night from 6 to 12 months poststudy. Their symptoms of nasal congestion have remained stable. The six patients converted to NCPAP also continue to use their machines. However, all report occasional nights when they are unable to use CP AP due to nasal congestion. The five patients restudied using the dual-chamber mask had a baseline apnea + hypopnea index of 62.3 ± 28.2 events per hour. During this study, they slept for 332 ± 78.6 min and had a apnea + hypopnea index of 4.4 ± 1.7 events per hour. During wakefulness, the percentage of time spent breathing through both the nose and mouth varied (Table 1). This percentage tended to decrease during sleep. During combined nasal and oral breathing, the ratio of oral to nasal peak flow was 1.51 ± 0.58 during w ~

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3. The percentage of the sleep period time spent awake and in each sleep stage on the baseline and the second ONCPAP nights. The error bars are the standard deviations. The percentage of stage 1 sleep was lower (p<0.01) and the percentages of slow-wave and REM sleep were higher (p<0.01) on ONCPAP compared with baseline nights. FIGURE

Oral-Nasal CPAP for Obstructive Sleep Apnea (Prosise, Berry)

Table !-Patients Using the Dual Chamber Mask Dual Chamber Mask Percentage of Timet With Combined Oral and Nasal Flow

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wakefulness and 1.05 ± 0.97 during sleep (Table 1) . A sample tracing of subject 2 during an episode of combined nasal and oral breathing while receiving bilevel pressure is shown in Figure 4. Part 2

The patients participating in study 2 ranged in age

from 37 to 72 years with a mean age of 60± 14.6 years. The patients were obese (170.7 ± 27 percent of ideal body weight) 12 and had moderate to severe OSA. They had been using NCPAP on a long-term basis for 6 months to 3 years. On an adaptation night, a mean pressure of 12.8 ± 2 .5em H20 (range, 9 to 15) using NCPAP was found to prevent apnea and

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CHEST / 106 / 1 / JULY,1994

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5. The percentage of the sleep period time spent awake and in each sleep stage on the NCPAP and ONCPAP nights in part 2 of the study. The error bars are the standard deviations. The subjects had a higher percentage of stage 2 sleep on NCP AP nights (p=0.03) and tended to spend more time awake and in stage 1 sleep on the ONCPAP nights. FIGURE

hypopnea. The mean apnea+hypopnea indices on subsequent NCPAP and ONCPAP nights using this pressure were 7.2±3.5 and 7.6±4.9 events per hour, respectively (P=NS). The TST was higher on the NCP AP nights, although this difference was not statistically significant (357.0±50.7 vs 320.8±44.9 min, p=0.09). The mean SPTs were very similar on the NCPAP and ONCPAP nights (404.6 ± 42.9 and 398.7 ± 33.4 min). The percentages of the SPT spent in each sleep stage are displayed in Figure 5. The percentage of the SPT spent awake and in stage 1 tended to be higher on ONCPAP nights. However, the only statistically significant difference was a smaller percentage of stage 2 sleep on the ONCPAP night (p=0.03). Thus, the patients tended to sleep less well on the ONCPAP nights and the apnea+ hypopnea index tended to be slightly higher, although still less than 10 events per hour of sleep. Thus, an effective level of CPAP applied with NCPAP was also effective using ONCPAP. DISC USSION

This study showed that CPAP delivered by a fullface mask (covering nose and mouth) may be an effective treatment alternative in patients with OSA who have difficulty tolerating NCPAP due to nasal congestion present de novo or developing while using NCPAP. Although such patients are a small fraction of the candidates for CP AP therapy , they still provide a difficult challenge. Treatment with decongestants, inhaled (nasal) steroids, or cromolyn sodium, humidification, and in some cases nasal surgery will control nasal symptoms in most patients. However, a few will continue to find NCPAP uncomfortable due to high nasal resistance. When several of our patients were restudied with 184

a dual-chamber mask, we found that the relative amounts of nasal and oral flow on CP AP varied among the patients and also varied during the night in the same patient. In fact, most patients still breathed a portion of the night through the nose alone. This does not diminish the importance of our findings , as all found breathing through the nose alone quite uncomfortable during wakefulness. It is likely that during sleep the lower flow rates and increased tolerance for resistive loading made nasal breathing more comfortable. It is also possible that the ability to breathe orally as well as nasally allowed these patients to acclimate to CP AP and fall asleep. However, another explanation is that the reason our subjects could tolerate ONCPAP but not NCPAP was due to an adaptation effect induced by an additional night of CP AP. This possibility cannot be eliminated, although we chose our study population as having very specific complaints and used an entire night to allow them to become adapted to NCPAP using slowly increasing pressures. This study was not designed to absolutely eliminate the possibility that these patients could be treated with NCPAP. The purpose was to test a possible alternative in a specific group of patients. Indeed, for reasons to be discussed below, we would still attempt to use NCPAP if possible in such patients. There have been few systematic studies of the effects of ONCPAP in patients with OSA. Mahadevia et aF studied EPAP using a full-face mask in patients with OSA. Although this therapy reduced the frequency of apnea, a clinically significant amount persisted in some patients. The failure of EP AP to maintain a positive pressure during inspiration probably explains the failure to abolish apnea. In NCPAP, the pressurized flow of air is delivered via the nares but usually does not escape through the mouth. The soft palate moves forward against the back of the tongue sealing off the oral route in most but not all patients. Some have suggested that CPAP applied to both the nose and mouth would not be effective as there would be no net pressure pushing the palate forward against the tongue and thereby opening the airway.8 Smith and coworkers9 were unable to open the upper airway in a group of patients with OSA at any pressure with a full-face CPAP mask. The difference in the findings of this study and the current report could be due to several factors. First, it is possible that a difference in mask or circuit construction resulted in different results. If full-face masks are pulled very tight, this tends to displace the mandible posteriorly and inferiorly which can narrow the upper airway. The system used by Smith and colleagues used a fixed flow of air (50 L/ min) while our CPAP devices varied flow to maintain airway pressure. However, the fixed flow Oral-Nasal CPAP for Obstructive Sleep Apnea (Prosise, Berry)

did not prevent NCPAP from opening the airway in their subjects. Second , it is possible that our patients were somehow already well adapted to breathing through both the nose and mouth due to long-term nasal obstruction. In any case, the fact remains that our patients with sleep apnea slept well with ONCPAP. We documented in several patients periods of sleep while receiving CPAP with both nasal and oral flow (Fig 4) . In awake subjects, the position of the palate is maintained either posteriorly against the posterior pharynx (oral breathing route) , anteriorly against the tongue (nasal breathing route), or in a midposition (oral and nasal route)P Although pharyngeal muscle tone is reduced during sleep, many normal-sleeping persons (especially male subjects) breathe orally at least some of the time.l 4 This implies that the palate rests in a either a mid position or a posterior position against the posterior pharyngeal wall to allow oral flow. These palate positions could be maintained passively or via reflexes. From our studies with the dual-chamber mask, it appears that CPAP can maintain airway patency during combined nasal and oral breathing. Thus, positive pressure must have been transmitted to the hypopharynx even if the palate was held in a midposition by equal pressure on both its nasal and oral sides. In the part 2 of our study, we found that an effective level of pressure administered as nasal CP AP was also effective when administered via a full-face mask. However, the findings of this study may not generalize to all full-face masks or all patients with OSA. The safest approach would still be a titration of the level of CPAP using the full-face mask . As mentioned previously, a tight full-face mask could potentially narrow the posterior airspace. It is also likely that the patients in part 2 of our study breathed almost entirely through the nose during sleep while receiving ONCPAP. We cannot eliminate the possibility that a greater amount of oral breathing might have required a higher amount of pressure to maintain airway patency . When the mouth is opened for oral breathing, this tends to displace the mandible posteriorly and inferiorly. This could reduce the size or compliance of the upper airway. In study 2, the patients slept less well using ONCPAP. If we had used an adaptation night to ONCP AP, perhaps this difference would have been reduced . However, since the patients had been using NCPAP for a long time, one night of adaptation to ONCPAP would not have been adequate to control for the months of adaptation to NCPAP. We did randomize the order of NCPAP and ONCPAP nights to minimize the effect of adaptation to the sleep laboratory. It is possible that had we studied more patients, the small difference in the apnea + hypo-

pnea indices between the two methods would have reached statistical significance. However, the small difference is unlikely to be clinically significant. The low amount of slow-wave sleep on both ONCPAP and NCPAP nights was probably due to the fact that four of the five subjects were aged 55 years or greater. In this population, the mean percentage of slow-wave sleep (as a percentage of SPT) is around 5 percent.l 5 Our prototype mask design attempted to produce an adequate face/ mask seal and avoid the need for excessive mask tightness. By cutting different size openings in the rubber sheath, we could adapt the mask to different facial sizes. However, one problem we encountered was the tendency of the cheeks to puff out, especially at the higher CP AP pressures. This is not a problem with nasal CP AP as the bony nasal structures are more rigid. An advantage of NCPAP over ONCPAP is that the mouth provides both a pressure relief valve during coughing and a route of ventilation should the flow source fail. Commercial ONCPAP masks would need to have a valve allowing inspiration of room air should the CPAP machine fail to provide adequate flow. In addition, some form of quick release to the straps would be useful to allow quick removal of the mask in case of coughing or vomiting. In summary , we found that ONCPAP may be a reasonable treatment alternative for patients with OSA who cannot tolerate NCPAP due to severe nasal congestion when other measures fail or as a temporary treatment until nasal obstruction can be adequately treated and the patient adapts to a purely nasal breathing route before and during sleep. However, obtaining an adequate mask seal is more difficult with ONCPAP and NCPAP. Certainly, additional studies of the effectiveness of ONCPAP would be necessary before this method of CP AP could be recommended for routine clinical use. REFERENCES

1 Sullivan CE, Issa FG, Berthon-Jones M , Eves L. Reversal of obstructive sleep apnea by continuous positive airway pressure applied through the nares. Lancet 1981; 1:862-65 2 Sullivan CE, FG Issa. Obstructive sleep apnea: In: Kryger MH, ed. Clinics in chest medicine: sleep disorders. 1985; 6:533-650 3 Rolfe I, Olson LG, Saunders NA. Long-term acceptance of continuous positive airway pressure in obstructive sleep apnea. Am Rev Respir Dis 1991; 144:1130-33 4 RauscherH, Popp W, WankeT, Zwick H. AcceptanceofCPAP therapy for sleep apnea. Chest 1991 ; 100:1019-23 5 Nino-Murcia G, McCann CC, Bliwise DL, Guilleminault C, Dement WC. Compliance and side effects in sleep apnea patients treated with nasal continuous positive airway pressure. West J Med 1989; 150:165-69 6 Fletcher EC, Luckett RA. The effect of positive reinforcement on hourly compliance in nasal continuous positive airway pressure users with obstructive sleep apnea. Am Rev Respir Dis 1991; 143:936-41 7 Mahadevia AK, Onal E, Lopata M. Effects of expiratory posCHEST /106 / 1/ JULY, 1994

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itive airway pressure on sleep-induced respiratory abnormalities in patient with hypersomnia sleep apnea syndrome. Am Rev Respir Dis 1983; 128:708-11 8 Kuna ST, Remmers JE. eural and anatomic factors in upper airway obstruction. In: Thaw ley SE, ed. Sleep apnea syndromes: medical clinics of north america. Philadelphia: WB Saunders 1985; 1237 9 Smith PL, Wise RA, Gold AR, Schwartz AR, Permutt S. Upper airway pressure-flow relationships in obstructive sleep apnea. J Appl Physiol 1988; 64:789-95 10 Rechtschaffen A, Kales A. A manual of standardized terminology, techniques, and scoring system for sleep stages in human adults. Los Angeles: Brain Information Service/ Brain Research

Institute, University of California, 1968 11 Sackner MA, Watson H , Belsito AS, Feinerman D, Suarez M, Gonzalez G, et al. Calibration of respiratory inductive plethysmography during natural breathing. J Appl Physiol 1989; 66:410-20 12 Russell RM, McGandy RB, Jelliffe D. Reference weights. Am J Med 1984; 76:767-69 13 Rodenstein DO, Stanescu DC. The soft palate and breathing. Am Rev Respir Dis 1986; 134:311-25 14 Gleeson K, Zwillich CW, Braier K, White DP. Breathing route during sleep. Am Rev Respir Dis 1986; 134:115-20 15 Williams RL, Karacan I, Hurshch CJ. EEG of human sleep: clinical applications. New York: Johns Wiley & Sons, 1974; 60

60th

Annual International Scientific Assembly October 30November 3, 1994 New Orleans For more information call 800 343-ACCP

186

AMERICAN COLLEGE OF CHEST PHYSICIANS

Oral-Nasal CPAP for Obstructive Sleep Apnea (Prosise, Berry)