Since 2002, there have been three outbreaks reported secondary to coronavirus [1]. On December 31, 2019, in the province of Hubai in Wuhan, China, reported for the first time pneumonia of non-identified etiology. In January 7, 2020, the molecule of Severe Acute Respiratory Syndrome Coronavirus − 2 was identified. The cases increased progressively until it officially declared a pandemic on March 11, 2020 [2].
The most common symptoms described in the study of Xiabo et al. were fever in 97–100% of the cases, cough (75–78%), dyspnea (60–66%), and malaise (20–44%) [3]. According to Zunyou Wu et al., the clinical presentation varied with age. 81% of the cases of severe COVID-19 will present a mild disease, 14% severe, and 5% will be critically ill [4]. Xiabo Yang et al. defined critically ill patients as those who required admission to the intensive care unit with mechanical ventilation or a requirement of FiO2 of at least 60% [5]. There have been settled risk factors for presenting a severe clinical course of the disease, among others, male gender, age > 60 years, type 2 diabetes, systemic high blood pressure, obesity, low income, chronic kidney disease, and chronic obstructive pulmonary disease [4]. Patients with comorbidities have 12 times more risk of death secondary to severe COVID-19 and six times more risk of requiring hospitalization [6].
Tomographic patterns reported in severe COVID-19 varied from patches to diffuse patterns of ground glass opacities of subpleural predominance that progressed at 1–3 weeks to consolidations and occasionally crazy paving, even in asymptomatic patients [7]. Despite this, some patients presented tomographic changes associated with Organizing Pneumonia three weeks after the initial presentation of the disease [8]. Consequently, some questions have been raised about the implications of severe COVID-19 in the pulmonary interstitium.
In this context, it has been disputed the impact of severe COVID-19 on patients with interstitial lung diseases (ILD). Multiple questions arose that we will enunciate in three main points: 1) The diagnostic approach of new patients during the pandemic. 2) the follow-up visits of the known patients with ILD, and 3) the therapeutic approach of the ILD patients with severe COVID-19 [9]. Some authors have developed studies to describe mortality in this group of patients.
Thomas Drake et al. reported a multicentric European study to evaluate the impact of severe COVID-19 in patients with ILD, reporting a mortality of 49% vs. 35% without lung diseases (p = 0.013). 84% of the patients in the group ILD and 79% of the control group received supplementary oxygen through high-flow oxygen devices. The group that did not receive high-flow nasal oxygen devices had better survival than those that received them (93% vs. 75%) [10]. In 2021 in Korea, Lee et al. did a national cohort study of patients with severe COVID-19 (n = 8070) and controls from the same geographic area with a relation of 1:15 without a diagnostic of severe COVID-19 (n = 121,050) from January 1 to May 30, 2020. They evaluated the number of patients with ILD in both groups and found that patients with ILD had a more significant probability of having severe COVID-19, in comparison with the rest of the population (0.8 versus 0.4% p = < 0.001), of presenting a more severe presentation of the disease (OR 2.23, IC 95% 1.24–4.01) and of dying (13.4% vs. 2.8%, p = < 0.001) [11]. Laure Gallay et al. reported that patients with idiopathic lung fibrosis had higher risk of death secondary to severe COVID-19 than other interstitial lung diseases (35% vs. 19%, p = 0.04) [12]. Duut N. carried out a retrospective study in a tertiary care hospital in India with 30 patients and obtained a mortality of 35.7%, however, they did not have a control group. [13]. Wang Y. et. Al. performed a meta-analysis, where they characterized a higher mortality rate in patients with (pooled effect = 1.26 [95% CI: 1.09–1.46) and higher disease (pooled effect = 1.34 [95% CI: 1.16–1.55) [14].
Given that the Instituto Nacional de Enfermedades Respiratorias (INER) is a reference center of interstitial lung diseases in Mexico and, during the pandemic has been a center of exclusive attention for severe and critically severe COVID-19, this study aimed to describe baseline clinical characteristics and the ILD more frequently presented in patients hospitalized by several or critical COVID and compare mortality during hospitalization.