Residual Lung Function Impairment Is Associated with Hyperventilation in Patients Recovered from Hospitalised COVID-19: A Cross-Sectional Study

Abstract

Patients who have recovered from COVID-19 show persistent symptoms and lung function alterations with a restrictive ventilatory pattern. Few data are available evaluating an extended period of COVID-19 clinical progression. The RESPICOVID study has been designed to evaluate patients' pulmonary damage previously hospitalised for interstitial pneumonia due to COVID-19. We focused on the arterial blood gas (ABG) analysis variables due to the initial observation that some patients had hypocapnia (arterial partial carbon dioxide pressure-PaCO₂ ≤ 35 mmHg). Therefore, we aimed to characterise patients with hypocapnia compared to patients with normocapnia (PaCO₂ > 35 mmHg). Data concerning demographic and anthropometric variables, clinical symptoms, hospitalisation, lung function and gas-analysis were collected. Our study comprised 81 patients, of whom 19 (24%) had hypocapnia as compared to the remaining (n = 62, 76%), and defined by lower levels of PaCO₂, serum bicarbonate (HCO^3-), carbon monoxide diffusion capacity (DL_CO), and carbon monoxide transfer coefficient (K_CO) with an increased level of pH and arterial partial oxygen pressure (PaO₂). K_CO was directly correlated with PaCO₂ and inversely with pH. In our preliminary report, hypocapnia is associated with a residual lung function impairment in diffusing capacity. We focus on ABG analysis's informativeness in the follow-up of post-COVID patients.

Keywords: COVID-19; hyperventilation; hypocapnia; interstitial pneumonia; lung function; restrictive pattern.

Figure 1

Scatterplots. Lines represent the regression with the 95% confidence intervals. Abbreviations: K_CO represents the carbon monoxide transfer coefficient; PaCO₂, arterial partial carbon dioxide pressure.