Positive End-expiratory Pressure and Mechanical Power

Area of Science:

• Mechanical ventilation
• Pulmonary physiology
• Critical care medicine

Background:

• Positive end-expiratory pressure (PEEP) is typically protective against ventilation-induced lung injury.
• PEEP contributes to the total mechanical power required for lung ventilation.
• The specific impact of increasing mechanical power via PEEP requires further investigation.

Purpose of the Study:

• To investigate the effects of increasing mechanical power by selectively modifying the PEEP component.
• To determine the threshold of mechanical power associated with lung injury and hemodynamic impairment.

Main Methods:

• Thirty-six piglets were ventilated in the prone position for 50 hours.
• PEEP levels ranged from 0 to 18 cm H2O, applied to six groups of six animals.
• Respiratory, gas exchange, hemodynamic, and histological variables were assessed.

Main Results:

• Lung mechanical power increased linearly with PEEP above 7 cm H2O.
• Lung elastances, vascular congestion, atelectasis, inflammation, and septal rupture decreased at PEEP 4-7 cm H2O but increased at higher PEEP.
• Mortality and hemodynamic impairment (increased pulmonary arterial pressure, fluid administration, and noradrenaline) significantly increased at PEEP levels of 14 and 18 cm H2O.

Conclusions:

• PEEP levels below 7 cm H2O mitigate atelectrauma compared to zero PEEP.
• Mechanical power exceeding a threshold of approximately 13 J/min, driven by elevated PEEP, causes significant lung injury and hemodynamic compromise.