Patients on mechanical ventilation for severe Covid-19 pneumonia had similar mortality rates to patients with other forms of severe pneumonia, but those with Covid tended to be kept on ventilation for longer, findings from a large health system have showed.
Among more than 1 800 mechanically ventilated patients with severe pneumonia, unadjusted analyses showed higher in-hospital mortality in the group with Covid-19, yet propensity score-matching ultimately revealed no differences between groups (40% vs 38%; OR 1.04, 95% CI 0.81-1.35, P=0.85), discovered Dr William Checkley of Johns Hopkins University in Baltimore, and colleagues in their study.
In the unadjusted analysis, Covid patients had a lower rate of liberation from mechanical ventilation, a finding that held up in the fully-matched model, accounting for differences in a host of clinical characteristics as well as risk factors for Covid-19 mortality (sub-distribution HR 0.81, 95% CI 0.65-1.00).
“Early in the pandemic, it was suggested that respiratory failure due to Covid-19 might exhibit a different physiologic phenotype and higher mortality compared with non-Covid-19 AHRF (acute hypoxemic respiratory failure),” Checkley and colleagues wrote in JAMA Network Open.
“This suggestion and a few small studies comparing respiratory failure due to Covid-19 and non-Covid-19 pneumonia led some clinicians to propose using non-standard mechanical ventilation strategies.”
In their study, patients in the matched groups also had similar respiratory system compliance and ventilatory ratio.
“Proponents of Covid-19 AHRF as a unique respiratory physiology phenotype suggest that strict adherence to low tidal volume ventilation may not be necessary and may even be harmful,” wrote Checkley and co-authors.
“However, if Covid-19 pneumonia leads to physiology typical of classic acute respiratory distress syndrome (ARDS), then evidence-based ARDS treatment strategies, such as low tidal volume ventilation and prone positioning, are the only interventions proven to reduce mortality.”
Prior studies comparing Covid and non-Covid pneumonia had various limitations, the team noted, including small sample sizes and methods of comparison that allowed for a high risk of confounding, leading to the current study, which was designed “to better inform this debate”.
Using electronic health record data, the researchers examined the outcomes of 1 846 adults with pneumonia that needed mechanical ventilation within the first two weeks of their hospitalisation at the Johns Hopkins Healthcare System, including 719 with Covid-19 pneumonia and 1 127 with non-Covid-19 pneumonia.
Before matching, patients were of similar age (62 vs 61 years), while those in the Covid-19 group were more likely to be male (62% vs 52%), have a higher body mass index (mean 32 vs 30), and were more likely to be from a minoritised group (64% vs 41%).
Diabetes was more common in the Covid group, as was a lower Sequential Organ Failure Assessment (SOFA) score, and lower mean PaO2/FiO2 ratio. Chronic obstructive pulmonary disease (COPD) and heart disease were more common in the non-Covid group.
Before matching, patients with Covid-19 pneumonia had a longer median time to discharge than patients with non-Covid-19 pneumonia (25 vs 14 days), and among patients discharged alive, those with Covid-19 spent twice as long on mechanical ventilation (10 vs 5 days).
Along with the differences in mortality and lower rate of liberation from mechanical ventilation, unadjusted analyses also showed lower static respiratory system compliance in the Covid-19 group on the first day of mechanical ventilation (32.0 vs 28.4 mL/kg PBW/cm H2O; P<0.001), with smaller differences on subsequent days.
After propensity-score matching, certain differences in baseline characteristics remained: patients in the Covid-19 group were less likely to have COPD and more likely to have diabetes, immunosuppression, and chronic kidney disease. Patients with Covid-19 pneumonia were also more likely to have a lower white blood cell count and to have received prior high-flow nasal cannula at hospital admission, while non-invasive mechanical ventilation was less common in this group.
After matching, Covid and non-Covid patients had similar static respiratory system compliance (mean difference 1.82 mL/cm H2O, 95% CI -1.53 to 5.17, P=0.28) and similar ventilatory ratios over the first week of ventilation (mean difference -0.05, 95% CI -0.22 to 0.11, P=0.52).
While ultimately not statistically significant, severe Covid-19 pneumonia patients were found to be discharged from the hospital at 90 days at a lower rate than their non-Covid-19 severe pneumonia counterparts (sub-distribution HR 0.83, 95% CI 0.68-1.01).
The study findings “add to the growing evidence that mortality for mechanically ventilated patients with Covid-19 is similar to that of patients with other pneumonias”, Checkley and colleagues concluded. “We did not find convincing evidence of different physiologic phenotypes in patients with Covid-19 pneumonia. We caution that deviating from current evidence-based practices (until there are robust data indicating why, how, and when), risks harm.”
Study details
Outcomes Among Mechanically Ventilated Patients With Severe Pneumonia and Acute Hypoxemic Respiratory Failure From SARS-CoV-2 and Other Etiologies
Eric Nolley, Sarina Sahetya, Chad Hochberg, Shakir Hossen, David Hager, Roy Brower, Elizabeth Stuart, William Checkley.
Published in JAMA Network Open on 10 January 2023
Key Points
Question Does Covid-19 pneumonia have a higher mortality rate than other causes of pneumonia?
Findings In this cohort study of 1 846 patients with pneumonia, Covid-19 pneumonia had similar mortality rates and physiologic phenotypes as other causes of pneumonia.
Meaning These findings suggest that mechanical ventilation use in Covid-19 pneumonia should follow the same evidence-based guidelines as any pneumonia.
Abstract
Importance
Early observations suggested that Covid-19 pneumonia had a higher mortality rate than other causes of pneumonia.
Objective
To compare outcomes between mechanically ventilated patients with pneumonia due to Covid-19 (March 2020 to June 2021) and other etiologies (July 2016 to December 2019).
Design, Setting, and Participants
This retrospective cohort study was conducted at the Johns Hopkins Healthcare System among adult patients (aged ≥18 years) with pneumonia who required mechanical ventilation in the first 2 weeks of hospitalisation. Clinical, laboratory, and mechanical ventilation data were extracted from admission to hospital discharge or death.
Exposures
Pneumonia due to Covid-19.
Main Outcomes and Measures
The primary outcome was 90-day in-hospital mortality. Secondary outcomes were time to liberation from mechanical ventilation, hospital length of stay, static respiratory system compliance, and ventilatory ratio. Unadjusted and multivariable-adjusted logistic regression, proportional hazards regression, and doubly robust regression were used in propensity score–matched sets to compare clinical outcomes.
Results
Overall, 719 patients (mean [SD] age, 61.8 [15.3] years; 442 [61.5%] were male; 460 [64.0%] belonged to a minoritised racial group and 253 [35.2%] were White) with severe COVID-19 pneumonia and 1127 patients (mean [SD] age, 60.9 [15.8] years; 586 [52.0%] were male; 459 [40.7%] belonged to a minoritised racial group and 655 [58.1%] were White) with severe non–Covid-19 pneumonia. In unadjusted analyses, patients with Covid-19 pneumonia had higher 90-day mortality (odds ratio, 1.21, 95% CI 1.04-1.41), longer time on mechanical ventilation (sub-distribution hazard ratio 0.72, 95% CI 0.63-0.81), and lower compliance (32.0 vs 28.4 mL/kg PBW/cm H2O; P < .001) when compared with those with non–Covid-19 pneumonia. In propensity score–matched analyses, patients with Covid-19 pneumonia were equally likely to die within 90 days as those with non–Covid-19 pneumonia (odds ratio, 1.04; 95% CI, 0.81 to 1.35; P = .85), had similar respiratory system compliance (mean difference, 1.82 mL/cm H2O; 95% CI, −1.53 to 5.17 mL/cm H2O; P = .28) and ventilatory ratio (mean difference, −0.05; 95% CI, −0.22 to 0.11; P = .52), but had lower rates of liberation from mechanical ventilation (sub-distribution hazard ratio, 0.81; 95% CI, 0.65 to 1.00) when compared with those with non–COVID-19 pneumonia. Patients with Covid-19 pneumonia had somewhat lower rates of being discharged from the hospital alive at 90 days (sub-distribution hazard ratio, 0.83; 95% CI, 0.68 to 1.01) than those with non–Covid-19 pneumonia; however, this was not statistically significant.
Conclusions and Relevance
In this study, mechanically ventilated patients with severe Covid-19 pneumonia had similar mortality rates as patients with other causes of severe pneumonia but longer times to liberation from mechanical ventilation. Mechanical ventilation use in Covid-19 pneumonia should follow the same evidence-based guidelines as for any pneumonia.
Medpage Today article – Are Severe COVID Patients Being Kept on Ventilation Longer Than Needed?
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