CPAP therapy via oronasal mask for obstructive sleep apnea.

STUDY OBJECTIVE: To determine the effectiveness of oronasal masks for positive pressure therapy in alleviating obstructive sleep apnea (OSA). METHODS AND PROCEDURES: Polysomnographic records of all 245 patients with OSA who underwent therapeutic trials of either continuous positive airway pressure (CPAP) or bilevel positive airway pressure between January 1991 and December 1992 were reviewed. Thirty patients who had been prescribed positive pressure therapy employing an oronasal mask were identified. Two patients known to be successfully treated with CPAP via oronasal mask underwent repeat polysomnography. The initial portion of the study was a diagnostic evaluation during which the patients were untreated. During the second portion of the study, both patients used CPAP via an oronasal mask while wearing a mouthpiece designed to maintain oral patency. RESULTS: The 30 patients with OSA who were identified in this study had significant amelioration of OSA while receiving positive pressure therapy via oronasal mask compared with the baseline, diagnostic polysomnogram (apnea index: 55.3 +/- 36.9-->1.6 +/- 3.7, p < 0.001; hypopnea index: 21.2 +/- 20-->2.7 +/- 4.9, p < 0.001; nadir of SaO2: 72.5 +/- 13.9-->87.1 +/- 4.3, p < 0.001, mean +/- SD). Improvement of OSA did not depend on maintenance of a closed mouth, as evidenced by elimination of sleep-disordered breathing in the two patients receiving positive pressure via oronasal mask while wearing a mouthpiece to keep the mouth open. CONCLUSION: Oronasal masks are a viable alternative interface for alleviating OSA with positive pressure therapy in those patients who are unwilling or unable to tolerate conventional nasal interfaces. Although there were no adverse consequences associated with the use of oronasal masks in our patients, appropriate safety precautions should be taken to minimize the possibility of aspiration of gastric contents and avoid untoward sequelae due to positive pressure device failure.

Accuracy of end-tidal and transcutaneous PCO2 monitoring during sleep.

STUDY OBJECTIVE: Although it is intuitively desirable, the measurement of arterial carbon dioxide tension (PaCO2) during diagnostic polysomnography and nocturnal trials of positive pressure therapy is invasive and potentially expensive. The accuracy of end-tidal carbon dioxide tension (PETCO2) and transcutaneous carbon dioxide (tcPCO2) monitoring in these contexts has not been systematically evaluated. This investigation was undertaken to evaluate the accuracy of PETCO2 and tcPCO2 in patients undergoing polysomnography. METHODS AND PROCEDURES: Values of PETCO2 were compared with PaCO2 in 19 patients spontaneously breathing room air (condition 1), in 13 patients receiving supplemental oxygen via nasal cannula (condition 2), and in 22 patients receiving nocturnal positive pressure ventilatory assistance (all but one with continuous positive airway pressure or bilevel positive airway pressure) (condition 3). The accuracy of tcPCO2 monitoring during sleep was also examined by comparing tcPCO2 values with simultaneously recorded PaCO2 values obtained during sleep in patients undergoing nocturnal polysomnography. Data were collected using three commercially available brands of tcPCO2 monitors (capnograph R, n = 17 patients; capnograph S, n = 17; and capnograph N, n = 15). RESULTS: Accuracy of PETCO2--There was significant scatter in the PaCO2 vs PETCO2 relationship such that only 23 percent of the variability in PaCO2 was explained by variation of PETCO2 during condition 1 and only 15 percent and 20 percent of the variability in PaCO2 was explained by variation of PETCO2 during conditions 2 and 3, respectively. 21.3 percent of patients had average PETCO2 values in error by > 10 mm Hg during condition 1, while during conditions 2 and 3, 46.2 and 63.7 percent of patients had average values in error by > 10 mm Hg, respectively. Accuracy of tcPCO2--While capnographs S and N generally overestimated PaCO2 with a wide scatter, capnograph R tended to have offsetting overestimations and underestimations of PaCO2 with a wide scatter. With each capnograph, a relatively small portion of the variability of the PaCO2 was explained by variability of the tcPCO2 (r2 = 0.2, 0.45 and 0.64 for capnographs S, N, and R, respectively). Across the three capnographs, 43.1 to 66.7 percent of measurements were in error by > 10 mm Hg, and 5 to 20 percent of measurements reflected errors > 20 mm Hg. There was no consistent relationship between the tcPCO2 error and the level of PaCO2, nor was the tcPCO2 error consistent in individual patients. There was no relationship between tcPCO2 accuracy and body mass index. CONCLUSION: Neither PETCO2, measured within a face mask, nor tcPCO2 is a consistently accurate reflection of PaCO2. This limits the utility of these variables in monitoring patients during diagnostic and therapeutic sleep studies, and in particular, during trials of nocturnal ventilatory assistance where adequate levels of support are to be established and unacceptable hyperventilation and respiratory alkalosis must be recognized.

Adequacy of prescribing positive airway pressure therapy by mask for sleep apnea on the basis of a partial-night trial.

We tested the hypothesis that a prescription for positive-pressure therapy (including pressure level, patient-device interface, and positive-pressure modality, e.g., CPAP or BiPAP) for obstructive sleep apnea (OSA) can be developed on the same night as the polysomnographic (PSG) diagnosis is made. Fifty consecutive patients with OSA in whom a partial-night PSG diagnosis was made (PSGD) underwent a therapeutic trial of positive-pressure therapy during the remainder of the night (PSG-PPP). The average apnea index during PSGD was 54.96 +/- 36.3 (mean +/- SD). On a subsequent full-night PSG (PSG-PPF), the prescription was tested. Thirty-one of the 50 patients were satisfactorily treated with CPAP, without variation of the interface during both PSG-PPP and PSG-PPF. In these patients the average pressure prescription while receiving PSG-PPF was statistically higher than during PSG-PPP (11.77 +/- 3.6 versus 10.56 +/- 3.6 cm H2O, respectively, p = 0.002). In 14 of these 31 patients (45%) some alteration in pressure requirement was necessary during PSG-PPF. Eleven patients required 2.5 cm H2O higher pressure and three patients required 5 cm H2O higher pressure during PSG-PPF than during PSG-PPP. There was a change of interface across the two therapeutic trials in 15 patients.(ABSTRACT TRUNCATED AT 250 WORDS)