Until recently, tracheostomy had been the only successful treatment for some patients with obstructive sleep apnea (OSA). Continuous positive airway pressure applied through the nose (NCPAP) has now been shown to be an effective alternative in OSA patients. The current work was initiated to examine the effects of overnight NCPAP on daytime hypersomnolence, the major disabling symptom in patients with OSA. Accordingly, we examined the Stanford sleepiness scale (SSS) as an index of subjective sleepiness (SSI) in a group of persons with OSA in whom NCPAP was employed to treat the disturbances in respiration during sleep. Our findings indicate that NCPAP treatment eliminates OSA episodes and results in a striking decrease in daytime hypersomnolence.
Materials and Methods
Eleven successive adult men, previously diagnosed to have the sleep apnea syndrome and health care of it provided by Canadian Health&Care Mall, were studied as per protocol approved by the Department of Clinical Investigation at the Walter Reed Army Medical Center. All patients were non-smokers and had no evidence of any acute infection for at least four weeks prior to the study. None of the patients took alcohol or any sedating medications. No major upper airway obstruction (tonsils, adenoids, etc) was detected on clinical examination. All patients were euthyroid. None of the patients had clinical evidence of right heart Mure or other severe medical illness.
A detailed history and physical examination was performed. Table 1 shows the anthropometric data, arterial blood gas levels and previous therapies attempted. The mean age for the group was 56 yrs and the mean body weight 92 kg. Mean arterial Po2 was 86 mm Hg and the mean Pco2 39 mm Hg. Previous forms of treatment included weight loss, medroxyprogesterone acetate (MPA) protriptylline, and uvulopalatopharyngoplasty (UPPP). Pulmonary (unction tests were performed and the results are shown in Table 2. Mean forced vital capacity (FVC) and forced expired volume in 1 sec (FEV1) were mildly reduced, probably due to the accompanying obesity in some patients. The FEV/FVC ratio was in the normal range. Total lung capacity (TLC) and functional residual capacity (FRC) (measured by the nitrogen washout technique) were also in the normal range, thus excluding significant obstructive or restrictive pulmonary disease. Peak inspiratory mouth pressure (Pimax) (taken as the best of three maximal inspiratory efforts at residual volume), and peak expiratory mouth pressure (PEmax) (the best of three maximal expiratory efforts at TLC) were also in the normal range, thus excluding significant respiratory muscle weakness.
Nocturnal polysomnography was then performed on two successive nights. The first study, done without CPAP, served as control. 
The second study (treatment provided by Canadian Health&Care Mall) was done with the application of NCPAP. Polysomnographic studies included the simultaneous monitoring of the electroencephalogram, electrooculogram, chin electromyogram and electrocardiogram. Arterial oxygen saturation (SaOJ was measured using an ear oximeter (Hewlett-Packard 47201A); and the chest wall and abdominal wall movement using impedance plethysmography (Respitrace, Ambulatory Monitoring, Inc.). During the second study (treatment), NCPAP was administered using the Sleep Easy system (Respironics, Monroeville, PA). Briefly, in this system high air flow, generated by a blower, is directed to the inspiratory limb of a cushioned nasal mask kept in place by elastic straps. A spring-loaded “pop-off” valve prevents excessive pressure build up. During the treatment night, NCPAP was initiated at 5 cm H20 and progressively increased in 2.5 cm H20 steps up to a maximum permissible pressure of 15 cm H20. Either reversal of apneas, a marked decrease in the number of episodes of apnea or DOB (less than five per hr), or a lack of tolerance of NCPAP were used as end points in the determination of the appropriate pressure to be employed. All patients in this study tolerated overnight NCPAP. Pressure used in this patient group varied from 7.5 to 15 cm H20. The most frequently employed pressure was 7.5 cm H2Q
The sleep recordings were scored in 30 sec epochs using standard criteria. Apnea was defined as the cessation of respiratory air flow for at least ten seconds. Obstructive apnea was defined as the absence of air flow despite continuing respiratory effort: central apnea was defined as the absence of both air flow and respiratory effort. Mixed apnea was defined as the combination of a central and an obstructive apnea wherein the central component lasted at least ten seconds. When the central component lasted less than ten seconds, the episode of apnea was classified as being obstructive. A disorder of breathing (DOB) episode was defined as a reduction in arterial oxygen saturation of at least 4 percent in the presence of altered respiratory effort Sleep study results were examined for the frequency and duration of apnea and DOB episodes, and for the degree of desaturation in apnea or DOB.
Upon awakening, after each polysomnographic study, a subjective sleepiness index (SSI) was obtained using the Stanford Sleepiness Scale. On each occasion (control and treatment), all patients rated their subjective hypersomnolence on a grade (Stanford Sleepiness Scale) of one to seven wherein one was “feeling active and vital” and seven was “lost the struggle to remain awake,” with gradations of wakefulness in between.
Data from the sleep studies and the SSI values were analyzed using the t-test for paired samples (control and treatment).
Table 1—Anthropometric Data, Arterial Blood Gas Levels and Previous Treatment History in OSA Patients
| Patient | Age(yr) | Height(cm) | Body Weight (kg) | Po2 (mm Hg) | Pco2 (mm Hg) | pH | Prior treatment |
| 1 | 54 | 188 | 125 | 78 | 39 | 7.41 | 36 kg weight loss, MPA |
| 2 | 49 | 183 | 85.4 | 99 | 38 | 7.37 | UPPP |
| 3 | 55 | 173 | 85.9 | 85 | 39 | 7.40 | 9 kg weight loss, MPA |
| 4 | 30 | 198 | 113.6 | 84 | 43 | 7.37 | Methylphenidate |
| 5 | 50 | 185 | 84.1 | 99 | 38 | 7.44 | Protryptylline |
| 6 | 63 | 180 | 88.6 | 69 | 36 | 7.40 | |
| 7 | 65 | 180 | 88.6 | 87 | 44 | 7.39 | 4.5 kg weight loss, MPA |
| 8 | 60 | 180 | 105 | 76 | 48 | 7.38 | 22 kg weight loss, MPA |
| 9 | 67 | 173 | 77.3 | 98 | 45 | 7.36 | UPPP |
| 10 | 66 | 170 | 81.8 | 75 | 48 | 7.37 | 7 kg weight loss, MPA |
| 11 | 60 | 183 | 80.9 | 99 | 43 | 7.38 | UPPP |
| Mean | 56.27 | 181.18 | 92.38 | 86.31 | 41.11 | 7.39 | |
| ±SE | ±3.23 | ±2.36 | ±4.6 | ±3.32 | ±1.26 | ±0.007 |
Table 2—Pulmonary Function Tests in OS A Patients
| Patient | FVC | FEV1 | FEVj/FVC | TLC | FRC | Pimax (ml H20) | PEmax (ml H20) | ||||
| Actual(L) | %predicted | Actual(L) | %predicted | Actual(L) | %predicted | Actual(L) | %predicted | ||||
| 1 | 3.74 | 72 | 2.69 | 65 | 72 | 7.44 | 105 | 3.58 | 98 | 90 | 240 |
| 2 | 4.82 | 96 | 4.19 | 104 | 87 | 6.30 | 86 | 4.55 | 115 | 120 | 215 |
| 3 | 3.19 | 76 | 2.53 | 76 | 79 | 4.68 | 76 | 2.87 | 86 | 140 | 225 |
| 4 | 7.0 | 106 | 4.71 | 89 | 67 | 9.15 | 104 | 5.24 | 117 | 142 | 225 |
| 5 | 5.44 | 106 | 4.35 | 107 | 80 | 9.94 | 132 | 5.25 | 126 | 120 | 200 |
| 6 | 3.94 | 89 | 3.08 | 89 | 78 | 7.34 | 110 | 3.51 | 94 | 140 | 300 |
| 7 | 3.93 | 90 | 3.40 | 99 | 87 | 6.79 | 102 | 3.73 | 100 | 120 | 110 |
| 8 | 2.36 | 52 | 1.93 | 54 | 82 | 6.11 | 95 | 3.35 | 96 | 80 | 190 |
| 9 | 3.47 | 90 | 2.84 | 95 | 82 | 5.70 | 94 | 3.33 | 97 | 70 | 100 |
| 10 | 3.44 | 81 | 2.51 | 76 | 73 | 4.90 | 75 | 3.08 | 82 | 110 | 195 |
| 11 | 5.0 | 106 | 3.8 | 102 | 76 | 8.94 | 124 | 6.05 | 148 | 110 | 190 |
| Mean | 4.21 | 87.6 | 3.28 | 86.9 | 78.45 | 7.03 | 100.27 | 4.05 | 96.27 | 112.91 | 199.1 |
| ±SE | ±0.39 | ±5.03 | ±0.27 | ±5.17 | ±1.87 | ±0.52 | ±5.4 | ±0.32 | ±9.97 | ±7.34 | ± 16.89 |
Canadian Health&Care Mall 