Data collection
Data was gathered from the electronic medical system including age, gender, underlying disease, clinical symptoms, imaging tests, medication history and laboratory indicators. Indicators with missing data≥60% were excluded from the statistical analysis. (The comparison of dynamic changes in oxygenation indices between the PP and non-PP groups was limited to the first 13 days of ICU admission.)
The laboratory indicators obtained within 24 hours of the patient’s admission to the ICU were designated as the initial laboratory indicators (Entering ICU), while those obtained within 24 hours prior to discharge were designated as the final laboratory indicators (At discharge). The time point closest to the beginning/end of PP (within 24h) was designated as the before/end PP laboratory indicator (B-PP/End-PP).
Detailed information was gathered regarding the PP: encompassing the initiation and conclusion times of each PP; comprehensive respiratory and hemodynamic parameters within the 6-hour pre-PP period, throughout the 12-hour PP duration, and within the 6-hour post-PP period. Additionally, any complications that transpired during the PP were documented.
Definition of PP time point: PP1 refers to the first PP , PP2 refers to the second PP, and PP3 refers to the third PP. T0 represents the time period of 0-6 hours before the current cycle of PP; T1 represents the time period of 0-6 hours in the current cycle of PP; T2 represents the time period of 6-12 hours in the current cycle of PP; and T3 represents the time period of 0-6 hours after the current cycle of PP.
Definition of changes in oxygenation index: Improvement of oxygenation represents that the average oxygenation index in T3 of the current cycle was greater than the average oxygenation index at PP1-T0; No improvement of oxygenation represents that the average oxygenation index in T3 of the current cycle was not greater than the average oxygenation index at PP1-T0.