The longer-term effects of COVID-19 on lung physiology remain poorly understood. Here, a new technique, computed cardiopulmonography (CCP), was used to study two COVID-19 cohorts (MCOVID and C-MORE-LP) at both ~6 and ~12 months post infection. CCP is comprised of two components. The first is to collect highly precise, highly time-resolved measurements of gas exchange using a purpose-built molecular flow sensor based around laser absorption spectroscopy. The second component is to estimate physiological parameters by fitting a cardiopulmonary model to the dataset. The measurement protocol involved 7 min breathing air followed by 5 min breathing pure O2. 178 participants were studied, with 97 returning for a repeat assessment. 126 arterial blood gas samples were drawn from MCOVID participants. For participants who had required intensive care and/or invasive mechanical ventilation, there was a significant increase in anatomical deadspace of ~ 30 ml and a significant increase in alveolar-to-arterial PO2 gradient of ~ 0.9 kPa relative to controls. Those who had been hospitalised had reductions in functional residual capacity of ~ 15%. Irrespectively of COVID-19 severity, participants who had had COVID-19 demonstrated a modest increase in ventilation inhomogeneity, broadly equivalent to that associated with 15 years of aging. This study illustrates the capability of CCP to study aspects of lung function not so easily addressed through standard clinical lung function tests. However, without measurements prior to infection, it is not possible to conclude whether the findings relate to the effects of COVID-19, or whether they constitute risk factors for more serious disease.
J Appl Physiol (1985)
human, laser absorption spectroscopy, lung volumes, respiratory dead space, specific ventilation