Baseline respiratory system compliance and its decline during general anesthesia for surgery: A retrospective observational study.

Maintaining respiratory system compliance (Crs) is a clue for lung recruitment strategies during surgery; however, patients' baseline Crs values have not been adequately addressed. We studied the association of low Crs at the induction of anesthesia (iCrs) with limited intraoperative respiratory management. We conducted a secondary analysis of retrospective study of consecutive surgical patients on ventilators between 2019 and 2020. The intra- and postoperative respiratory-related parameters were compared between the low iCrs group (<25% of the distribution) and others. Primary outcome was postoperative respiratory support related with iCrs and intraoperative Crs decline. Multivariate analysis and other root-cause analysis were performed to evaluate the relationships between low iCrs and outcomes. A total of 5568 patients were included and classified into either the low iCrs group (<43 mL/cmH2O, n = 1392) or the other group (n = 4176). The age was older and both the duration of surgery and the duration of anesthesia were shorter in the low iCrs group than in the other groups. Unexpectedly, the low iCrs group was associated with a smaller decrease in hourly changes in Crs (-1.4% [-11.3% to 11.2%] vs -13.0% [-21.3% to -5.3%], P < .001). Despite the smaller decrease in Crs, the low iCrs group showed a higher incidence of > 3 days of postoperative oxygen therapy (adjusted OR 1.60 (1.29-1.97), P < .001) and > 3 days of mechanical ventilation following surgery (adjusted OR, 1.55 (1.02-2.36), P = .039) than the other group. The significances in postoperative therapies were exaggerated in emergency surgery. The low iCrs patients showed a smaller decline in hourly changes in Crs and longer postoperative respiratory supports. Not only the decrease in Crs during surgery but also the initial Crs value warrant the intra- and postoperative respiratory management.