Clinical Predictors of Lung Function in Patients Recovering From Mild COVID-19

Arturo Cortes-Telles; Esperanza Figueroa-Hurtado; Diana Lizbeth Ortiz-Farias; Gerald Stanley Zavorsky


BMC Pulm Med. 2022;22(294) 

In This Article

Abstract and Introduction


Background: Few studies have assessed lung function in Hispanic subjects recovering from mild COVID-19. Therefore, we examined the prevalence of impaired pulmonary diffusing capacity for carbon monoxide (DLCO) as defined by values below the lower limit of normal (< LLN, < 5th percentile) or less than 80% of predicted in Hispanics recovering from mild COVID-19. We also examined the prevalence of a restrictive spirometric pattern as defined by the ratio of forced expiratory volume in 1 s (FEV1) to forced vital capacity (FVC) being ≥ LLN with the FVC being < LLN. Finally, we evaluated previous studies to find factors correlated to impaired DLCO post-COVID-19.

Methods: In this observational study, adult patients (n = 146) with mild COVID-19 were recruited from a long-term follow-up COVID-19 clinic in Yucatan, Mexico, between March and August 2021. Spirometry, DLCO, and self-reported signs/symptoms were recorded 34 ± 4 days after diagnosis.

Results: At post-evaluation, 20% and 30% of patients recovering from COVID-19 were classified as having a restrictive spirometric pattern and impaired DLCO, respectively; 13% had both. The most prevalent reported symptoms were fatigue (73%), a persistent cough (43%), shortness of breath (42%) and a blocked/runny nose (36%). Increased age and a restrictive spirometric pattern increased the probability of having an impaired DLCO while having a blocked nose and excessive sweating decreased the likelihood. The proportion of patients with previous mild COVID-19 and impaired DLCO increased by 13% when the definition of impaired DLCO was < 80% predicted instead of below the LLN. When comparing previous studies, having severe COVID-19 increased the proportion of those with impaired DLCO by 21% compared to those with mild COVID-19.

Conclusions: One-third of patients with mild COVID-19 have impaired DLCO thirty-four days post-diagnosis. The criteria that define impaired DLCO and the severity of COVID-19 disease affects the proportion of those with impaired DLCO at follow-up. One-fifth of patients have a restrictive spirometric pattern.


Severe acute respiratory syndrome coronavirus 2 (SARS-CoV2) is a virus that originated in Wuhan City, China, in December of 2019 and is responsible for the coronavirus disease (COVID-19).[1] Between December 29, 2019, and February 16, 2020, deaths increased from 1 to 1666 in China.[1] By October 1, 2021, over 4.79 million people worldwide have died from COVID-19.[2] As such, COVID-19 has become one of the fatal pandemics ever recorded in human history.

As the number of patients recovering from COVID-19 increases worldwide, there is an urgent need to keep analysing pulmonary sequelae to facilitate optimal clinical treatments. COVID-19 is a heterogeneous disease with several long-term sequelae.[3] Patients recovering from the acute phase may report long-term multi-system symptoms, including various pulmonary function abnormalities,[3–22] psychological sequelae,[3] and reduced physical functioning.[10,23,24] Specifically, pulmonary diffusing capacity for carbon monoxide (DLCO) is significantly impaired 30 to 180 days after the onset of (SARS-CoV-2) (Additional file 1: Table S1). However, most of these studies evaluated lung function in hospitalised patients due to the severity of their condition; very few studies focused on patients recovering from mild COVID-19.[4,7,10,20] Furthermore, even fewer studies focus on the effects of COVID-19 in Latino populations.[6,25]

Recent reports indicate the presence of racial and ethnic disparities with a disproportionate burden of COVID-19-related severity infections and mortality.[26,27] These disparities may be partly attributable to higher comorbidities that worsen COVID-19 outcomes.[28] Specifically, there is limited research on the physiological effects of COVID-19 in the Mexican Latino population. Few studies have analysed the Latino community's persistent symptoms and lung function post-COVID-19.[28]

Our main objectives were to (1) determine factors associated with an impaired DLCO in Hispanic patients with mild COVID-19; and (2) evaluate data from previous studies to determine which factors predicted the proportion of patients with an impaired DLCO at follow-up.