Modelling lung diffusion-perfusion limitation in mechanically ventilated SARS-CoV-2 patients

Area of Science:

• Pulmonary Medicine
• Critical Care Medicine
• Respiratory Physiology

Background:

• COVID-19 significantly impacts respiratory function, particularly in mechanically ventilated patients.
• Understanding the evolution of respiratory parameters is crucial for managing severe cases.
• High-altitude environments may influence respiratory physiology in critically ill patients.

Purpose of the Study:

• To describe the daytime changes in respiratory parameters for mechanically ventilated COVID-19 patients.
• To differentiate respiratory mechanics between survivors and non-survivors.
• To investigate the gas exchange limitations in COVID-19 patients.

Main Methods:

• Analysis of respiratory parameters in mechanically ventilated COVID-19 patients at high altitude (Arequipa Hospital, Peru).
• Comparison of respiratory compliance, oxygen saturation (SatO2), and capnia between survivors and non-survivors.
• Utilizing a model to partition diffusion and perfusion limitations in the air-blood barrier for gas exchange.

Main Results:

• Both survivors and non-survivors showed decreased respiratory compliance, indicating fewer inflatable alveolar units.
• All patients were hyperventilated with SatO2 maintained above 90%.
• Non-survivors exhibited progressive hypercapnia, unlike survivors who remained normocapnic.
• Impaired CO2 removal in non-survivors was linked to increased positive end-expiratory pressure (PEEP) and plateau pressure (Pplat), causing capillary compression and reduced air-blood contact time.

Conclusions:

• Mechanical ventilation in COVID-19 patients leads to reduced respiratory compliance.
• Progressive hypercapnia in non-survivors suggests a shift towards perfusion limitation in gas exchange.
• Increased ventilatory pressures (PEEP, Pplat) contribute to impaired CO2 removal by affecting pulmonary microcirculation.