Background: Side-stream spirometry offers a non-invasive method to mon
itor continuously respiratory mechanics in intubated patients. We stud
ied the effects of different positions on dynamic lung compliance duri
ng anaesthesia. Methods: The study consisted of 56 patients, operated
in supine, prone, kneeling or lateral park-bench position. Dynamic lun
g compliance and inspiratory peak pressure were recorded after inducti
on of anaesthesia, 15 min and 1 h after posturing the patient. Results
: The first measured compliances were comparable in all groups. The co
mpliance in the lateral and the prone positions was significantly lowe
r than in the supine position at 15 min (P<0.01) and 1 h (P<0.001) aft
er the posture change. The peak inspiratory pressure was significantly
lower in the kneeling position than in the other groups (P<0.01 at th
e first measurement, P<0.001 at the later measurements). No correlatio
n was found between body mass index and compliance. Conclusion: We fou
nd that dynamic lung compliance decreased significantly upon change of
posture from supine to lateral or prone position, whereas in the knee
ling position no change in compliance was observed. We suggest that th
e kneeling position might be preferable to the prone position. (C) Act
a Anaesthesiologica Scandinavica 41 (1997).