Increased intrapulmonary shunt and alveolar dead space post-COVID-19

Area of Science:

• Pulmonary Medicine
• Infectious Diseases
• Physiology

Background:

• COVID-19, caused by SARS-CoV-2, can lead to persistent respiratory complications.
• Intrapulmonary shunt (Q_S/Q_t) and alveolar dead space (V_D/V_T) are known indicators of impaired gas exchange.

Purpose of the Study:

• To investigate the prevalence and predictors of increased intrapulmonary shunt (Q_S/Q_t) and alveolar dead space (V_D/V_T) in patients recovering from COVID-19.
• To compare gas exchange abnormalities between patients with mild-moderate versus severe-critical COVID-19 illness.

Main Methods:

• Studied 59 unvaccinated patients 15-403 days post-infection.
• Measured arterial and end-tidal gases to calculate Q_S/Q_t, V_D/V_T, and relative alveolar ventilation (VArel).
• Analyzed the relationship between gas exchange parameters and NIH severity, age, BMI, and time since infection.

Main Results:

• 37% of patients had increased Q_S/Q_t and 86% had increased V_D/V_T.
• Severe-critical COVID-19 predicted higher Q_S/Q_t, while increasing age weakly predicted higher V_D/V_T.
• Increased VArel was observed in most patients, irrespective of initial disease severity.

Conclusions:

• Persistent intrapulmonary shunt and alveolar dead space are common after COVID-19 recovery, suggesting ongoing pulmonary microvascular pathology.
• Gas exchange abnormalities are more prevalent in patients with a history of severe-critical COVID-19.
• Elevated alveolar dead space may persist long-term, potentially linked to microvascular dysfunction.