The ventilator settings for non-ARDS patients in this study mainly explored the following clinical problems: 1) low DP, PEEP and MP could prolong VFD, reduce the ratio of mortality and LOS, however, the effect of VT was inclusive. The beneficial effects of combined strategies need to be further explored; 2) Aged patients had worse outcome, and obese patients had longer VFD, lower mortality ratio, and longer hospital stays; 3) The machine learning models on the prognosis of the population were well-predicted.
The lower DP level, the better patient's prognosis. The DP reflects the strain during each respiratory cycle,. For ARDS patients, DP is an independent risky and the most critical ventilation factor for survival, the reduced DP could improve survival ratio of the population,and higher DP was connected with postoperative pulmonary complications and high ratio of mortality. However, a retrospective study of MIMIC-II public database showed that the DP on the first 24 hours was not related to the patient's mortality.
Low VT may benefit non-ARDS patients. Low VT was associated with better clinical outcomes, a low mortality ratio, shorter VFD, and lower risk of pulmonary complications, but had little more need for sedation or analgesia. Different ventilation strategies for non-ARDS, such as high VT and low PEEP were better on improving lung compliance, while low VT and low PEEP were associated with shorter LOS. However, the difference of VFD in the 21 days was small in another RCT. In addition, a multi-center retrospective study conducted by PRoVENT (Practice of Ventilation in critically ill patients without ARDS at onset of ventilation) in the year of 2016 and 2018 showed that there was little association between VT and clinical prognosis. The results of a trial on protective ventilation in patients without ARDS will soon be on the way. Our analysis shows that VT has little to do with the patient's prognosis, probably because of a clinical consensus on the low VT ventilation strategy.
Low VT may increase alveolar instability, and PEEP could maintain alveolar open, minimize lung damage, and avoid atelectasis and oxygen toxicity35. High PEEP reduced the incidence of ARDS and hypoxemia, but not for VFD and in-hospital mortality, and prophylactic PEEP in non-hypoxic patients could reduce the occurrence of hypoxia and pneumonia. An RCT evaluating the impact on PEEP for non-ARDS patients is still in progress.
MP refers to the energy transferred to the patient's respiratory system during MV which could be an independent predictor of mortality in ARDS patients, and high level of MP was a risk factor for critically ill patients' clinical prognosis16. Could it serve as a novel biomarker for the lung in patients without ARDS?
In patients undergoing MV, the aged has bad clinical prognosis, however, obese patients suffering ARDS tended to have lower mortality and fewer VFD, but not for hospital stays compared with the normal-weight patients,. Prognosis studies exclusive for the obese without ARDS are incomplete.