Effect of expiratory positive airway pressure on sleep disordered breathing.

Study Objectives: We sought to determine the effect of expiratory positive airway pressure on end expiratory lung volume (EELV) and sleep disordered breathing in obstructive sleep apnea patients.

Design: Observational physiology study

Participants: We studied 10 OSA patients during sleep wearing a facial mask. We recorded 1 hour of NREM sleep without treatment (baseline) and 1 hour with 10 cm H2O EPAP in random order, while measuring EELV and breathing pattern.

Mechanisms used to restore ventilation after partial upper airway collapse during sleep in humans.

Background: Most patients with obstructive sleep apnoea (OSA) can restore airflow after an obstructive respiratory event without arousal at least some of the time. The mechanisms that enable this ventilatory recovery are unclear but probably include increased upper airway dilator muscle activity and/or changes in respiratory timing. The aims of this study were to compare the ability to recover ventilation and the mechanisms of compensation following a sudden reduction of continuous positive airway pressure (CPAP) in subjects with and without OSA.

Influence of wakefulness on pharyngeal airway muscle activity.

Background: Whether loss of wakefulness itself can influence pharyngeal dilator muscle activity and responsiveness is currently unknown. A study was therefore undertaken to assess the isolated impact of sleep on upper airway muscle activity after minimising respiratory/mechanical inputs.

Methods: Ten healthy subjects were studied.

The effect of altitude descent on obstructive sleep apnea.

Background: The present requirement for "at facility" polysomnograms requires many residents in mountain communities to descend in elevation for sleep testing, which may cause misleading results regarding the severity of obstructive sleep apnea (OSA).

Design: Eleven patients with previously undiagnosed sleep apnea living at an altitude > 2,400 m (7,900 feet) in Colorado underwent diagnostic sleep studies at their home elevation and at 1,370 m (4,500 feet), and 5 of the 11 patients were also studied at sea level.

Results: The mean (SE) apnea-hypopnea index (AHI) fell from 49.

Genioglossal muscle response to CO2 stimulation during NREM sleep.

Study Objectives: The objective was to evaluate the responsiveness of upper airway muscles to hypercapnia with and without intrapharyngeal negative pressure during non-rapid eye movement (NREM) sleep and wakefulness.

Design: We assessed the genioglossal muscle response to CO2 off and on continuous positive airway pressure (CPAP) (to attenuate negative pressure) during stable NREM sleep and wakefulness in the supine position.

Setting: Laboratory of the Sleep Medicine Division, Brigham and Women's Hospital.

Respiratory control stability and upper airway collapsibility in men and women with obstructive sleep apnea.

Obstructive sleep apnea (OSA) is two to three times more common in men as in women. The mechanisms leading to this difference are currently unclear but could include gender differences in respiratory stability [loop gain (LG)] or upper airway collapsibility [pharyngeal critical closing pressure (Pcrit)]. The aim of this study was to compare LG and Pcrit between men and women with OSA to determine whether the factors contributing to apnea are similar between genders.