Abstract
IntroductionThere is relatively little published on the effects of COVID-19 on respiratory physiology, particularly breathing patterns. We sought to determine if there were lasting detrimental effect following hospital discharge and if these related to the severity of COVID-19.MethodsWe reviewed lung function and breathing patterns in COVID-19 survivors > 3 months after discharge, comparing patients who had been admitted to the intensive therapy unit (ITU) (n = 47) to those who just received ward treatments (n = 45). Lung function included spirometry and gas transfer and breathing patterns were measured with structured light plethysmography. Continuous data were compared with an independent t-test or Mann Whitney-U test (depending on distribution) and nominal data were compared using a Fisher’s exact test (for 2 categories in 2 groups) or a chi-squared test (for > 2 categories in 2 groups). A p-value of < 0.05 was taken to be statistically significant.ResultsWe found evidence of pulmonary restriction (reduced vital capacity and/or alveolar volume) in 65.4% of all patients. 36.1% of all patients has a reduced transfer factor (TLCO) but the majority of these (78.1%) had a preserved/increased transfer coefficient (KCO), suggesting an extrapulmonary cause. There were no major differences between ITU and ward lung function, although KCO alone was higher in the ITU patients (p = 0.03). This could be explained partly by obesity, respiratory muscle fatigue, localised microvascular changes, or haemosiderosis from lung damage. Abnormal breathing patterns were observed in 18.8% of subjects, although no consistent pattern of breathing pattern abnormalities was evident.ConclusionsAn “extrapulmonary restrictive” like pattern appears to be a common phenomenon in previously admitted COVID-19 survivors. Whilst the cause of this is not clear, the effects seem to be similar on patients whether or not they received mechanical ventilation or had ward based respiratory support/supplemental oxygen.
Highlights
There is relatively little published on the effects of COVID-19 on respiratory physiology, breathing patterns
Like other pneumonias (SARS, Middle East Respiratory Syndrome (MERS)), early reports show that COVID-19 produces a sustained restrictive lung function pattern after survivors are discharged from hospital when reviewed in COVID-19 follow up clinics [2,3,4,5]
Spirometry parameters included F EV1, Forced Vital Capacity (FVC), Forced Expired Volume in 1 Second (FEV1)/FVC, Vital Capacity (VC) and Peak Expiratory Flow (PEF), whilst single breath carbon monoxide gas transfer test measured gas transfer (TLCO), transfer coefficient (KCO) and alveolar volume (Alveolar Volume (VA)). VA in the absence of any airflow obstruction was used as a surrogate for total lung capacity (TLC)
Summary
There is relatively little published on the effects of COVID-19 on respiratory physiology, breathing patterns. The severe acute respiratory syndrome Coronavirus 2 (SARS-CoV-2), which emerged from Wuhan, China in December 2019 has developed into the COVID-19 global pandemic [1]. It has become one of the most studied infections in recent medical history with a plethora of publications on pathology, immunology, physiology and Stockley et al Respir Res (2021) 22:255 virology in multiple areas of clinical specialisation. Like other pneumonias (SARS, MERS), early reports show that COVID-19 produces a sustained restrictive lung function pattern after survivors are discharged from hospital (at least 3 months post-hospital discharge) when reviewed in COVID-19 follow up clinics [2,3,4,5]. Much work is focussing on the treatment of post-COVID-19 symptoms including tackling dyspnoea, fatigue, and dysfunctional breathing [6]
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