Airway closure and distribution during hip arthroplasty.

Airway closure, resting lung volume (FRC) and gas distribution were assessed single breath nitrogen washout during hip arthroplasty. Airway closure occurred above FRC in all the patients during enflurane anaesthesia and surgery, with no change in either FRC or airway closure when the femoral and acetabular prostheses were inserted. The slope of the nitrogen alveolar plateau, which was considered to indicate gas distribution, rose significantly from 4.1 to 5.7% N2/1 when the prostheses were inserted. By the end of surgery the slope had returned to the initial value. This finding indicates a transient effect on the airways when the prostheses are implanted.