Study objectives: Repeated episodes of upper-airway
occlusion are the main characteristics of patients with obstructive
sleep apnea (OSA) during sleep. It has been reported that an impairment
in the sensation of detection and a depression of ventilatory
compensation to added load could be observed in such patients. In this
study, we examined patients with OSA to evaluate the inspiratory effort
sensation (IES), ventilation, and mouth occlusion pressures during
added resistive loading while awake and to determine whether they can
be reversed by nasal continuous positive airway pressure (CPAP)
Design: A hospital-based case-control
Setting: A sleep laboratory of a medical unit
Subjects: Seventeen patients with moderate
to severe OSA and 10 control subjects were included in this study.
Measurements: All patients with OSA had undergone standard
nocturnal polysomnography. Patients with OSA and control subjects were
evaluated for IES measured by a modified Borg score, ventilation, and
mouth occlusion pressure during control and inspiratory resistive
loaded breathing. These tests were repeated in all patients with OSA
after 2 weeks of nasal CPAP treatment.
Results: IES to
inspiratory resistive loading was lower in patients with OSA than in
control subjects. There were no differences in ventilation and mouth
occlusion pressure between patients and control subjects during loaded
breathing. After 2 weeks of nasal CPAP, the decreased IES was increased
in patients with OSA.
Conclusion: In patients with
OSA, the decreased IES to inspiratory resistive loaded breathing is
reversible with nasal CPAP. This could be one additional benefit of
nasal CPAP in the treatment of OSA.