Faculty Bibliography

Nasal expiratory positive airway pressure (nEPAP) delivered with a disposable device (Provent, Ventus Medical) has been shown to improve sleep-disordered breathing (SDB) in some subjects. Possible mechanisms of action are 1) increased functional residual capacity (FRC), producing tracheal traction and reducing upper airway (UA) collapsibility, and 2) passive dilatation of the airway by the expiratory pressure, carrying over into inspiration. Using MRI, we estimated change in FRC and ventilation, as well as UA cross-sectional area (CSA), in awake patients breathing on and off the nEPAP device. Ten patients with SDB underwent nocturnal polysomnography and MRI with and without nEPAP. Simultaneous images of the lung and UA were obtained at 6 images/s. Image sequences were obtained during mouth and nose breathing with and without the nEPAP device. The nEPAP device produced an end-expiratory pressure of 4-17 cmH(2)O. End-tidal Pco(2) rose from 39.7 +/- 5.3 to 47.1 +/- 6.0 Torr (P < 0.01). Lung volume changes were estimated from sagittal MRI of the right lung. Changes in UA CSA were calculated from transverse MRI at the level of the pharynx above the epiglottis. FRC determined by MRI was well correlated to FRC determined by N(2) washout (r = 0.76, P = 0.03). nEPAP resulted in a consistent increase in FRC (46 +/- 29%, P < 0.001) and decrease in ventilation (50 +/- 15%, P < 0.001), with no change in respiratory frequency. UA CSA at end expiration showed a trend to increase. During wakefulness, nEPAP caused significant hyperinflation, consistent with an increase in tracheal traction and a decrease in UA collapsibility. Direct imaging effects on the UA were less consistent, but there was a trend to dilatation. Finally, we showed significant hypoventilation and rise in Pco(2) during use of the nEPAP device during wakefulness and sleep. Thus, at least three mechanisms of action have the potential to contribute to the therapeutic effect of nEPAP on SDB

Experimental models of human sleep disordered breathing (S

Nasal positive expiratory pressure (nEPAP) delivered with an expiratory valve (ProventVentus Medical) has recently been shown to have a beneficial effect on sleep disordered breathing (Rosenthal, JCSM 2009; 5:532). The mechanism of action is not fully understood but effects on lung volume have been invoked (Patel, JCSM in press). In the present study we evaluate the effect of nEPAP on functional residual capacity (FRC) and upper airway (UA) dimensions. Methods: Fast MRI was used to acquire 4-5 images/sec in the awake state during multiple cycles of nose breathing with and without nEPAP in 6 patients with S

STUDY OBJECTIVE: A one-way nasal resistor has recently been shown to reduce sleep disordered breathing (SDB) in a subset of patients with Obstructive Sleep Apnea Hypopnea Syndrome (OSAHS). The purpose of this study was to examine characteristics predictive of therapeutic response to the device and provide pilot data as to its potential mechanisms of action. PATIENTS, INTERVENTIONS, AND MEASUREMENTS: 20 subjects (15M/5F, age 54 +/- 12 years, BMI 33.5 +/- 5.6 kg/m(2)) with OSAHS underwent 3 nocturnal polysomnograms (NPSG) including diagnostic, therapeutic (with a Provent(R) nasal valve device), and CPAP. Additional measurements included intranasal pressures and PCO(2), closing pressures (Pcrit), and awake lung volumes in different body positions. RESULTS: In 19/20 patients who slept with the device, RDI was significantly reduced with the nasal valve device compared to the diagnostic NPSG (27 +/- 29/h vs 49 +/- 28/h), with 50% of patients having an acceptable therapeutic response. Among demographic, lung volume, or diagnostic NPSG measures or markers of collapsibility, no significant predictors of therapeutic response were found. There was a suggestion that patients with position-dependent SDB (supine RDI > lateral RDI) were more likely to have an acceptable therapeutic response to the device. Successful elimination of SDB was associated with generation and maintenance of an elevated end expiratory pressure. No single definitive mechanism of action was elucidated. CONCLUSIONS: The present study shows that the nasal valve device can alter SDB across the full spectrum of SDB severity. There was a suggestion that subjects with positional or milder SDB in the lateral position were those most likely to respond. CITATION: Patel AV; Hwang D; Masdeu MJ; Chen GM; Rapoport DM; Ayappa I. Predictors of response to a nasal expiratory resistor device and its potential mechanisms of action for treatment of obstructive sleep apnea. J Clin Sleep Med 2011;7(1):13-22

STUDY OBJECTIVES: Since on CPAP, the nose is the primary determinant of upper airway resistance, we assess utility of noninvasive measures of nasal resistance during wakefulness as a predictor of directly assessed upper airway resistance on CPAP during sleep in patients with obstructive sleep apnea/hypopnea syndrome. METHODS: Patients with complaints of snoring and excessive daytime sleepiness were recruited. 14 subjects underwent daytime evaluations including clinical assessment, subjective questionnaires to assess nasal symptoms and evaluation of nasal resistance with acoustic rhinometry (AR) and active anterior rhinomanometry (RM) in the sitting and supine positions. Patients underwent nocturnal polysomnography on optimal CPAP with measurements of supraglottic pressure to evaluate upper airway resistance. Comparisons were made between nasal resistance using AR and RM during wakefulness, and between AR and RM awake and upper airway resistance during sleep. RESULTS: Our study shows that measures of awake nasal resistance using AR and RM had little or no correlation to each other in the sitting position, whereas there was significant but weak correlation in the supine position. Upper airway resistance measured while on CPAP during sleep did not show significant relationships to any of the awake measures of nasal resistance (AR or RM). CONCLUSION: Awake measurements of nasal resistance do not seem to be predictive of upper airway resistance during sleep on CPAP

OBJECTIVE: Determine if the Pillar palatal implant system reduces continuous positive airway pressure (CPAP) pressure and improves patient compliance with CPAP therapy. STUDY DESIGN: Randomized, double-blind, placebo-controlled study. SETTING: Four geographically dispersed tertiary sleep disorder referral centers. METHODS: Subjects with mild to moderate sleep apnea dissatisfied with CPAP because of pressure-related complaints were randomized to receive Pillar implants or a sham procedure performed in double-blind fashion. Active and sham groups were compared for changes in therapeutic CPAP pressures (primary outcome) with a 90-day follow-up sleep study and CPAP compliance (secondary outcome) with a 90-day smart card report. RESULTS: Twenty-six subjects were randomized to Pillar implants and 25 to a sham implant procedure. There were no differences between groups with regard to demographics and baseline parameters. Both sham and active groups had reduced mean CPAP pressure (-1.1 vs -0.5 cm H(2)O) with no difference between groups (P = .32) at 90-day follow-up. In addition, there was no difference in average daily CPAP use between groups (P = .80). Both groups experienced improvements in Epworth sleepiness scores and Functional Outcome of Sleep Questionnaire scores at 90 days with no differences between groups. The active group reported significantly higher CPAP satisfaction scores than the sham group (P = .04). CONCLUSION: Pillar implants do not significantly reduce CPAP pressure or increase CPAP compliance compared to sham controls but may subjectively improve CPAP satisfaction. These findings do not presently support the use of Pillar implants as an adjunctive treatment to improve CPAP compliance