To our knowledge, this is the first nationwide survey among Chinese anesthesiologists that demonstrate considerablely variabe practices with respect to intraoperative ventilation management in non-cardiothoracic surgical setting. The majority of respondents reported applying low VT, PEEP, and ARM separately, while only about a fifth performed LPV with bundles of low VT, PEEP, and ARM.
The LPV strategies
It has been well established that intraoperative LPV strategies, containing low VT, appropriate PEEP with or without ARMs, could reduce the development of PPCs[12-14]. A retrospective study reported that approximate half of anesthesiologists at U.S. academic medical centers utilized both low VT and PEEP. Our survey showed that only 21.8% routinely applied both low VT and PEEP, although most respondents recognized bundles of “low VT, PEEP, and ARMs” as LPV strategy. This may explained by the knowledge-practice gap among Chinese anesthesiologists. In recent years, some studies have proposed that open-lung ventilation strategy, driving pressure (ΔP) guided ventilation strategy[17, 18], and mechanical power–guided ventilation strategy may have lung protective effects. However, results remain equivocal regarding their ability to prevent PPCs[20-23].
Low VT and PEEP
In our survey, the majority of respondents performed low VT ventilation. The finding was in line with existing literature, which described that the use of low VT had been significantly increased[24, 25]. However, less than half of respondents calculated VT using PBW in accordance with expert recommendation. Two studies found that compared to PBW, calculating VT with ABW would overestimate the target VT and that may expose patients to harmful volutrauma and barotrauma, especially to obese patients[27, 28]. In addition, our survey suggested more than 3/5 respondents set PEEP. While an observational study noted that 80% of patients still were ventilated without PEEP. Reasons for not using PEEP included concerns about potential hemodynamic fluctuations  and PEEP not included in the default settings of ventilators. Besides, we found most participants preferred PEEP level at 0-5 cmH2O, which was consistent with prior studies [32, 33]. However, a network meta-analysis found that moderate-to-high PEEP (≥5 cmH2O) combined with low VT ventilation could reduced the risk of PPCs in surgical patients. By far, there was no consensus on optimal PEEP level, and individualized PEEP according to patients’ lung compliance or ΔP was suggested by several studies [18, 34]. Our findings suggested that most anesthesiologists preferred to set PEEP based on lung compliance.
Our survey showed that more than 60% of anesthesiologists performed ARMs during MV. The results differed from a large observational study, in which less than 1/5 patients received intraoperative ARMs . The implementation of ARMs after intubation was suggested to alleviate the deterioration of functional residual capacity following anesthesia. However, it remains inconsistent regarding the role of ARMs after intubation to prevent PPCs. In our study, only a small number of respondents performed ARMs after tracheal intubation. This might be the result of detrimental effects of ARMs on cardiac output which could aggravate the instability of hemodynamics after induction. Our survey showed that respondents preferred to perform manual ARMs, while ventilator-driven ARMs recommended in the expert consensus were rarely utilized.
Other ventilatory settings
Our survey suggested that VCV was most commonly used among respondents, which was consistent with the results of two observational studies[36, 37]. Most anesthesiologists preferred FiO2 at 40%-60%. Until now, the optimal level of FiO2 remains unknow. Two randomized controlled trials comparing the use of high (80%) versus low (30%) FiO2 showed no difference in reducing the incidence of PPCs[38, 39]. Expert consensus recommended FiO2 should be set to ≤ 0.4 with the goal of using the lowest possible FiO2 to achieve normoxia (or SpO2 ≥ 94%) and reduce the occurrence of resorption atelectasis. In our survey, a small number of anesthesiologists applied high FiO2 (>80%) during operation.