Two Physiologic Latent Classes of Acute Hypoxemic Respiratory Failure in Sepsis Are Distinguished by Lung Mechanics and Gas Exchange

Abstract

Objectives: Physiologic subtypes of acute hypoxemic respiratory failure (AHRF) may confer a differential response to treatments, particularly therapeutic strategies that are specific to pulmonary organ failure. We sought to identify physiologic latent classes of sepsis-associated AHRF defined by respiratory mechanics, oxygenation, ventilation, and radiographic patterns of lung injury, and to determine the association between class membership and 30-day mortality.

Design: We performed latent class analysis of patients with AHRF newly requiring mechanical ventilation enrolled in a prospective cohort of patients with sepsis from 2011 to 2020. We used logistic regression adjusted for Acute Physiology and Chronic Health Evaluation to determine the association between class membership and 30-day mortality and examined the distribution of patients classified as "hyperinflammatory" by previously described biomarker-based subphenotyping paradigms.

Setting: Philadelphia, Pennsylvania, United States.

Patients: Eight hundred eighty-two patients.

Measurements and main results: We identified two physiologic latent classes. Class 1 (n = 390) was characterized by low static compliance and impaired ventilation when compared with class 2 (n = 432). Mortality at 30 days was higher in the more physiologically severe class 1 when compared with class 2 (adjusted risk difference 0.12, p < 0.001) despite a similar severity of sepsis. Class 1 also contained a higher proportion of female patients and patients with obesity.

Conclusions: We identified two physiologic latent classes of sepsis-associated AHRF. Relative to class 2, class 1 was distinguished by low compliance, impaired ventilation, and higher 30-day mortality independent of the severity of sepsis. The higher percentage of female patients and patients with obesity in class 1 suggests a potential role for body composition in class determination. Physiologic classes were not primarily determined by qualification for acute respiratory distress syndrome or previously described biomarker-based subphenotypes, suggesting a distinct physiologic "axis" of heterogeneity.

Keywords: latent class analysis; mechanical; respiratory insufficiency; respiratory physiologic phenomena; sepsis; ventilators.

Figure 1.

Selection of the study population. ABG = arterial blood gas, AHRF = acute hypoxemic respiratory failure, IMV = invasive mechanical ventilation, MESSI = Molecular Epidemiology of SepsiS in the ICU.

Figure 2.

Continuous variables were log-transformed and scaled to a mean of 0 and sd of 1 (z scale). DP = driving pressure, Pplat = plateau pressure.