Chest Wall Oscillation

Study objective: The objective was to determine whether external chest wall oscillation (ECWO) during sleep (1) reduced spontaneous ventilation while maintaining adequate gas exchange over several hours, (2) influenced the quality and distribution of sleep, and (3) increased the number of respiratory events. Design: Prospective controlled study with counterbalanced order of intervention. Setting: Pulmonary function sleep laboratory. Participants: Seven healthy volunteers. Intervention: One night ofECWO at 1 Hz (I:E=I:l; oscillation mean [SEM] from -11.1 [0.7] to 6.0 [0.7] cm H20) and a night during which the cuirass was applied without ECWO. Measurements and results: ECWO resulted in a significant decrease in spontaneous minute ventilation (ViE) in all stages of sleep. ECWO was associated with a reduction in the total sleep time and a reduction in rapid eye movement (REM) sleep. The number of stage changes and the sleep effiiciency did not change significantly. The mean Pco2 was similar between the control and cuirass nights (44 to 46 mm Hg). There was a significant decrease in the mean Pco2 during stage 1 (41 [2] mm Hg) and stage 2 (42 [2]mm Hg) sleep during theECWO night. The mean arterial oxygen saturation (SaO2) was maintained at 96 to 97% throughout sleep during the control, cuirass, and ECWO nights. The apnea+hypopnea index increased (p<0.05) during ECWO mostly due to an increase in the number of hypopneas in stage 2 sleep. During ECWO, 18 of 30 respiratory events were associated with an arousal, whereas only 2 events were associated with an arousal during the control night. Conclusions: ECWO can be tolerated for several hours and will assist ventilation while maintaining normal mean Pco2 and mean SaO2 during sleep. Monitoring of the apnea+hypopnea index and the SaO2 is recommended at the time of application. Clinical trials to define the most appropriate indications for ECWO are now necessary. (CHEST 1996; 110:128-35)