Mechanical power (MP), the rate of mechanical energy (ME) delivery, is a recently introduced unifying ventilator parameter consisting of tidal volume, airway pressures, and respiratory rates, which predicts pulmonary complications in several clinical contexts. However, ME has not been previously studied in the perioperative context and neither parameter has been studied in the context of thoracic surgery utilizing one lung ventilation.
The relationships between mechanical energy variables and postoperative pulmonary complications were evaluated in this post hoc analysis of data from a multicenter randomized clinical trial of lung resection surgery conducted between 2020 and 2021 (n=1,170). Time-weighted average MP (MPTWA) and ME (the area under the MP time curve) were obtained for individual patients. The primary analysis was the association of MPTWA and ME with pulmonary complications within 7 postoperative days. Multivariable logistic regression was performed to examine the relationships between energy variables and the primary outcome.
In 1,055 patients analyzed, pulmonary complications occurred in 41% (431/1055). The median (interquartile ranges) ME and MPTWA in patients who developed postoperative pulmonary complications (PPC) vs those who did not were 1,146 (811‒1530) J vs 924 (730‒1240) J (P<0.001), and 6.9 (5.5‒8.7) J/min vs 6.7 (5.2‒8.5) J/min (P=0.091), respectively. ME was independently associated with PPCs (ORadj 1.44 [95%CI 1.16‒1.80], P=0.001). However, the association between MPTWA and PPCs was time dependent and MPTWA was significantly associated with PPCs in cases utilizing longer periods of mechanical ventilation (≥210 minutes; ORadj 1.46 [95%CI 1.11‒1.93], P=0.007). Normalization of ME and MPTWA to either predicted body weight or to respiratory system compliance did not alter these associations.
ME and, in cases requiring longer periods of mechanical ventilation, MP were independently associated with PPC in thoracic surgery.
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