An analysis of flow volume curves during artificial ventilation

Expiratory flow-volume curves during artificial ventilation (FV-av) were analyzed in 48 patients undergoing general anesthesia. They were divided into 4 groups according to preoperative respiratory disorders; obstructive type (group 1), restrictive type (group 2), small airway disease (group 3) and normal control (group 4). Expiratory flow rates and volumes during artificial ventilation were plotted on an X-Y recorder to calculate V50/V25, mean time constant ratio (MTCR), obstructive index (OI) and slope ratio (SR). FV-av values were compared among groups. FV-av values in groups 2 were significantly higher than those in group 4. The values in group 1 and those in group 3 were not significantly different from those in group 4. FV-av values may reflect restrictive respiratory dysfunctions but they are not sensitive enough to detect obstructive lung disease.