Clinical Research Directory

The APL valve on the anaesthesia machine will be adjusted to 30 cmH₂O, and the rapid oxygen inflow valve will be pressed to increase the pressure to the maximum, maintaining the pressure for 30 seconds.

Starting from 5 cmH₂O, PEEP will be titrated upwards in 5 cmH₂O increments every 30 seconds until a maximum of 30 cmH₂O is reached. After maintaining for 40 seconds, PEEP will be decreased by 5 cmH₂O every 30 seconds until it returns to the pre-recruitment level.

Lung ultrasound will be performed on patients. If any lung region has an LUS score ≥ 2, ultrasound-guided RM will be performed; otherwise, no operation will be conducted. After the ultrasound examination, the probe will be positioned over the lung region exhibiting the most severe aeration loss (highest LUS) to guide the RMs. The ventilator will be set to pressure-controlled ventilation (PCV), maintaining the inspiratory pressure at 40 cmH₂O. PEEP will be gradually increased from 5 cmH₂O, with increments of 5 cmH₂O every 5-10 seconds, until ultrasound shows no atelectatic areas. The pressure will be maintained at 40 cmH₂O for 40 seconds. An airway pressure ceiling of 40 cmH₂O was established, and the pressure and the time used for the RM will be recorded.