The Impact of Low Versus High Positive End-expiratory Pressure on Diaphragm Function, Ventilation Efficiency, and Lung Mechanics

The Impact of Low Versus High Positive End-Expiratory Pressure on Diaphragm Function, Ventilation Efficiency, and Lung Mechanics During Pressure Support Ventilation: A Randomized Interventional Crossover Study

The goal of this interventional study is to evaluate the effect of different positive end-expiratory pressures (PEEP) on lung and diaphragm function in patients mechanically ventilated with pressure support ventilation in the intensive care unit. The main questions aim to answer:

Does higher PEEP level affect diaphragm contractions and ventilatory efficiency? Does higher PEEP level limit inspiratory efforts? Does higher PEEP level affect lung compliance?

The participants will be subjected to three different PEEP levels during pressure support ventilation:

Low PEEP (4 cmH2O), Medium PEEP (10 cmH2O), High PEEP (16 cmH2O).

The lung and diaphragm function will be evaluated using high-resolution esophageal manometry, electrical activity of the diaphragm, external diaphragm ultrasound and spirometric ventilator data.

Inclusion Criteria:

• Mechanical ventilation with pressure support or mechanical ventilation with possibility to transition to pressure support
• Oxygen requirement ≤ 50%
• Pressure support ≤ 12 cmH2O
• PEEP ≤ 12 cmH2O
• Age ≥ 18 years
• Adequate intravascular volume status

Exclusion Criteria:

• Circulatory instability
• Brain death diagnosis/brain death evaluation
• Norepinephrine dose > 0.4 µg/kg/min
• Muscle relaxation administered within 2 hours
• Pregnancy
• Contraindication to esophageal catheterization (e.g., esophageal varices)
• Conditions with increased risk of pneumothorax (such as severe COPD (Chronic Obstructive Pulmonary Disease) or extensive emphysema)
• Untreated pneumothorax
• Symptomatic airway obstruction

Discontinuation criteria during ongoing study intervention:

• Heart rate > 120 beats/min
• Systolic blood pressure > 180 mmHg
• Inspired oxygen fraction > 70%
• Respiratory rate > 35/min
• RASS (Richmond Agitation Sedation Scale) ≥ 2
• Doubling of norepinephrine dose or increase of norepinephrine dose to > 0.5 µg/kg/min to maintain mean arterial pressure
• Bradycardia < 45 beats/min