The impact of metabolic syndrome on regional ventilation and perfusion in ARDS: an observational cohort study using electrical impedance tomography

Background: Acute Respiratory Distress Syndrome (ARDS) is characterized by severe hypoxemia from heterogeneous impairments in regional ventilation and perfusion. Metabolic syndrome, a combination of central obesity, insulin resistance, hypertension, and dyslipidemia, affects over one-third of adults worldwide and is associated with systemic inflammation, endothelial dysfunction, and increased ARDS risk. Whether metabolic syndrome alters regional ventilation and perfusion distributions in ARDS remains unknown.

Methods: We performed a retrospective cohort study of 25 mechanically ventilated patients with ARDS evaluated by the Massachusetts General Hospital Lung Rescue Team from 2020 to 2025. After a recruitment maneuver and decremental PEEP titration in the supine position, we quantified regional ventilation and perfusion distributions using electrical impedance tomography across a 32 × 32 pixel impedance matrix. We used Bayesian regression modeling adjusted for age, severity of illness, and ARDS etiology to define associations between metabolic syndrome and regional distributions.

Results: 25 patients were included, of whom 44% (n = 11) had metabolic syndrome. The mean age was 52 (16) years, PaO₂/FiO₂ was 151 (61), and 48% (n = 12) had pulmonary ARDS. Patients with metabolic syndrome were younger and had higher respiratory system compliance. In dorsal lung regions, metabolic syndrome was associated with reduced ventilation distribution (adjusted mean difference: – 5.84%, 95% credible interval: – 12.29 to 1.17, posterior probability of decrease = 95.2%) and modest, uncertain reductions in perfusion distribution (- 2.01%, 95% credible interval: – 9.25 to 5.41). The proportion of pixels with a low ventilation-to-perfusion impedance ratio showed a trend toward increase in dorsal lung regions in patients with metabolic syndrome (4.25%, 95% credible interval: – 4.49 to 13.1, posterior probability = 80.3%). Body mass index accounted for 40% of the difference in dorsal ventilation. The association between regional ventilation and perfusion distributions was similar between groups (interaction coefficient: 0.01, 95% credible interval: – 0.34 to 0.36).

Conclusions: In ARDS, metabolic syndrome may be associated with reduced ventilation distribution to dorsal lung regions with smaller changes in perfusion distribution. The association between regional ventilation and perfusion distributions did not differ by metabolic syndrome. These exploratory findings suggest metabolic syndrome may primarily affect ventilation distribution rather than perfusion distribution in ARDS.