[Experimental results of using the "open lung concept"]

Area of Science:

• Critical Care Medicine
• Respiratory Physiology
• Experimental Animal Models

Background:

• The "open lung concept" integrates strategies to maintain alveolar stability.
• Previous research incorporated elements like small tidal volumes into ventilatory strategies.
• A standardized protocol for applying the full open lung concept in an animal model was lacking.

Purpose of the Study:

• To demonstrate the application of the "open lung concept" in an animal model of acute lung injury.
• To evaluate the effectiveness of recruitment maneuvers and positive end-expiratory pressure (PEEP) in reopening and maintaining lung aeration.

Main Methods:

• Acute lung injury was induced in pigs (30-45 kg) via surfactant washout.
• Ventilation initially followed the ARDS Network protocol (PEEP 9 cmH2O, tidal volume 6 ml/kg).
• Opening and closing pressures were titrated to set recruitment pressure and PEEP; respiratory rate adjusted for normocapnia.

Main Results:

• Oxygenation Index (OI) decreased post-injury (556 to 176 mmHg), improved with ARDS Network mode (285 mmHg), and normalized after recruitment (near baseline).
• Recruitment with peak pressure 53 cmH2O and PEEP 17 cmH2O restored oxygenation.
• Normocapnia was achieved with a respiratory rate of 39 breaths/min and median tidal volume of 8 ml/kg.

Conclusions:

• Low tidal volumes alone do not fully reopen experimentally induced acute lung injury.
• The "open lung concept," utilizing recruitment maneuvers and adequate PEEP, successfully reopened and maintained lung aeration in this animal model.
• This approach offers a potential strategy for managing acute lung injury.