Minimizing Lung Injury During Laparoscopy in Head-Down Tilt: A Physiological Cohort Study

Area of Science:

• Anesthesiology
• Pulmonary Medicine
• Surgical Critical Care

Background:

• Laparoscopy increases intra-abdominal pressure, leading to lung atelectasis.
• Positive end-expiratory pressure (PEEP) can mitigate atelectasis but risks hyperinflation.
• Cyclic alveolar opening and hyperinflation may cause ventilator-induced lung injury and postoperative pulmonary complications.

Purpose of the Study:

• To investigate the effects of PEEP on atelectasis, lung stress, and hyperinflation.
• To evaluate PEEP's impact during laparoscopic surgery in the Trendelenburg position.

Main Methods:

• An open-label, interventional physiological cohort trial involving 23 nonobese patients.
• A decremental PEEP protocol (15, 10, 5 cm H2O) was applied.
• Lung atelectasis assessed by lung ultrasound score, transpulmonary pressure, and Pao2/FiO2 ratio. Lung stress evaluated by driving pressure and dynamic compliance. Hyperinflation assessed by dead space volume.

Main Results:

• Higher PEEP levels significantly reduced lung ultrasound scores (atelectasis) and driving pressures (lung stress).
• End-expiratory transpulmonary pressures became more negative with lower PEEP, indicating reduced lung strain.
• Pao2/FiO2 ratios and dynamic respiratory system compliance decreased with higher PEEP, while dead space ventilation remained unchanged.

Conclusions:

• Higher PEEP levels during Trendelenburg laparoscopy promote lung-protective ventilation.
• PEEP effectively reduces atelectasis and lung stress.
• Lung protection is achieved without inducing significant global alveolar hyperinflation.