The longer patients with severe COVID-19 pneumonia experience respiratory distress — regardless of severity — the more likely they are to need invasive mechanical ventilation (MV), according to a recent study published in Pulmonology.

The observational cohort study of patients hospitalized in the intensive care units of 5 university hospitals in the Emilia-Romagna region of Italy was conducted to determine whether the length of time COVID-19 patients experienced symptoms of respiratory distress affected the need for invasive MV.

The indications for noninvasive MV in the hospital management protocols included a Pao2/fraction of inspired oxygen (FIO₂) ratio less than 200 mmHg, a respiratory rate of 30 or more breaths per minute, and respiratory distress that activated the accessory respiratory muscles. The indications for invasive MV included neurological failure (Glasgow Coma Scale score <10), cardiovascular failure, and the persistence of severe respiratory distress following a noninvasive MV trial. 


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For the study, the researchers included 171 adults with pneumonia from SARS-CoV-2 who had a Pao2/FIO₂ ratio lower than 300 mmHg, respiratory distress symptoms, and a need for invasive or noninvasive MV. Exclusion criteria included respiratory distress of unknown duration, an end-of-life decision, and mechanical respiratory support occurring prior to hospital admission.

Patients were assigned to 3 groups according to the time elapsed between the onset of respiratory distress and the start of MV. Duration before ventilation varied significantly (P <.001) among the cohorts: 17 of 57 patients fell into the shortest duration group, 29 of 57 into the intermediate duration group, and 40 of 57 into the longest duration group. A longer period of respiratory distress raised the risk of invasive ventilation significantly in the univariate analysis (odds ratio, (OR) 5.5; CI, 2.48 – 12.35; P =.003). Multivariable regression analysis substantiated this association (OR, 10.7; CI, 2.89 – 39.41; P <.001). In the group having the longest duration of symptoms, white blood cell counts (P =.006) and platelet counts (P =.010) were lower at the onset of respiratory distress. Clinical outcomes such as mortality and hospital stay failed to produce significant variations among the groups.

The results of the analysis should be approached with caution, the authors said, because of certain noted limitations. The retrospective observational design may have created unmeasurable biases in patient selection. Identification of the onset of distress was not rigorous, but the researchers said that the onset data were collected with sufficient accuracy. Esophageal pressure was not measured, so confirming whether the pathophysiological conditions of persistent negative intrathoracic pressure existed was not possible.

The researchers concluded that pulmonologists should consider using noninvasive MV early to reduce the progression of respiratory distress. “Regardless of severity, our data showed that the long unresolved duration of respiratory distress before the application of positive pressure ventilation may also represent an earlier marker for invasive MV need,” the authors wrote. “Therefore, from a clinical point of view, it may be advisable to apply positive pressure ventilation (even noninvasive) at the first signs of respiratory distress; thus, preventing disease progression,” they noted.

Reference

Busani S, Coloretti I, Baciarello M, et al. Association between respiratory distress time and invasive mechanical ventilation in COVID-19 patients: a multicentre regional cohort study. Pulmonology. Published online March 28, 2022. doi:10.1016/j.pulmoe.2022.03.004