Oral airway resistance during wakefulness in patients with obstructive sleep apnoea
- Department of Respiratory Medicine, Westmead Hospital, and University of Sydney, NSW 2145, Australia
- Dr T C Amis, Department of Respiratory Medicine, Westmead Hospital, Westmead, NSW 2145, Australia
- Received 15 July 1998
- Revision requested 6 October 1998
- Revised 4 December 1998
- Accepted 27 January 1999
Abstract
BACKGROUND Patients with obstructive sleep apnoea (OSA) have a number of upper airway structural abnormalities which may influence the resistance of the oral airway to airflow. There have been no systematic studies of the flow dynamics of the oral cavity in such patients.
METHODS Inspiratory oral airway resistance to airflow (RO) was measured in 13 awake patients with OSA in both the upright and supine positions (neck position constant). Each subject breathed via a mouthpiece while the nasal airway was occluded with a nasal mask.
RESULTS In the upright position the mean (SE) RO was 1.26 (0.19) cm H2O/l/s (at 0.4 l/s) which increased to 2.01 (0.43) cm H2O/l/s when supine (p<0.05, pairedt test). The magnitude of this change correlated negatively with the respiratory disturbance index (r = –0.60, p = 0.03).
CONCLUSION In awake patients with OSA RO is normal when upright but abnormally raised when in the supine position.
