Mechanical Ventilation Lessons Learned From Alveolar Micromechanics.

Area of Science:

• Critical Care Medicine
• Respiratory Physiology
• Pulmonary Engineering

Background:

• Lung injury morbidity and mortality have stagnated due to a focus on ventilator macro-parameters, neglecting alveolar micro-environment responses.
• Current bedside assessments like lung compliance and oxygenation cannot predict alveolar and alveolar duct responses to mechanical ventilation.
• Alveolar tidal volumes are influenced by recruitment and heterogeneous mechanical properties, not solely by set ventilator tidal volumes.

Purpose of the Study:

• To review mechanical ventilation adjustments impacting alveolar stability and patient outcomes in lung injury.
• To highlight the under-appreciated role of inspiratory and expiratory times in alveolar stability.
• To emphasize the need to target individual patient respiratory physiology at the alveolar level.

Main Methods:

• Review of experimental data on mechanical ventilation effects at the alveolar level.
• Analysis of current limitations in assessing alveolar responses to ventilation.
• Discussion of how macro-parameters fail to capture micro-environmental dynamics.

Main Results:

• Alveolar tidal volumes are more dependent on recruited alveoli and their heterogeneity than set ventilator volumes.
• Lung calculations averaging alveolar parameters cannot predict individual alveolar heterogeneity.
• The impact of inspiratory and expiratory times on alveolar stability is currently underestimated.

Conclusions:

• Improving lung injury outcomes requires a shift towards targeting alveolar-level respiratory physiology.
• Mechanical ventilation adjustments must consider individual alveolar responses and heterogeneity.
• Further research into alveolar mechanics during ventilation is essential for clinical practice.