Digital measurements of air leak flow and intrapleural pressures in the immediate postoperative period predict risk of prolonged air leak after pulmonary lobectomy

Background: The objective of this prospective observational study was to evaluate the association between the airflow and intrapleural pressures digitally recorded during the immediate postoperative period after lobectomy and their ability to predict the risk of subsequent prolonged air leak (PAL). Methods: A total of 145 consecutive patients underwent pulmonary lobectomy in two centers. All patients were managed with the chest tube placed on suction (-20cmH₂O) until the morning of the first postoperative day. Measurement of airflow and maximum and minimum intrapleural pressures were recorded during the 6th postoperative hour using a digital chest drainage device. Logistic regression analysis validated by bootstrap was used to test independent association of variables with PAL (air leak>72h). Results: The mean air leak flow at the 6th postoperative hour was 86mlmin^-1 (0-1100mlmin^-1). The mean maximum and minimum pleural pressures at the 6th postoperative hour were -11.4cmH₂O and -21.9cmH₂O, respectively. Logistic regression and bootstrap showed that the mean air leak flow (p=0.007) and the mean differential pleural pressure (ΔP: maximum-minimum intrapleural pressure) (p=0.02) at the 6th postoperative hour were reliably associated with PAL, independent of the effect of age, forced expiratory volume 1 (FEV1), chronic obstructive pulmonary disease (COPD) status, diffusing capacity of the lung for carbon monoxide (DLCO), side, and site of lobectomy. According to best cutoffs derived by receiver operating characteristic (ROC) analysis the following combinations showed incremental risk of PAL: ΔP<10+Flow<50: 4% (3/73); ΔP>10+Flow<50: 15% (5/33); ΔP<10+Flow>50: 36% (5/14); ΔP>10+Flow>50: 52% (13/25). Conclusions: The levels of both air leak flow and pleural pressure measured at the 6th postoperative hour are associated to a different extent with the duration of air leak. Interpretation of the data measured at an early time point by digital chest drainage systems allows estimation of the risk of subsequent PAL. In this way, digital devices may help to plan postoperative management to allow both safe and more accurate implementation of fast-tracking strategies.