Alveolar Dead Space Fraction is Not Associated with Early RV Systolic
Dysfunction in Pediatric ARDS
Abstract
Primary Hypothesis: We hypothesized that higher alveolar dead space
fraction (AVDSf) at PARDS onset would be associated with right
ventricular (RV) systolic dysfunction within the first 24 hours of
PARDS. Study Design and Methods: We performed a retrospective
single-center cohort study of PARDS patients with clinically obtained
echocardiograms within 24 hours. Primary exposure was AVDSf at PARDS
onset. Primary outcome was RV systolic dysfunction as defined by RV
global longitudinal strain (GLS) (> - 18%). Secondary
outcomes included pulmonary hypertension (PH) and RV systolic
dysfunction as defined by other echocardiogram parameters, and measures
of oxygenation. Unadjusted and adjusted logistic and linear regression
were used to investigate AVDSf associations with outcomes. Results:
Seventy-six patients were included: median age 6.2 years, 50% female,
and 66% with moderate or severe PARDS. Median AVDSf was 0.2 (IQR
0.1-0.3), 32% had RV dysfunction, and 24% had PH. Unadjusted and
adjusted logistic regression showed no association between AVDSf and RV
systolic dysfunction or PH by any echocardiographic measure. Unadjusted
and adjusted linear regression demonstrated the association of AVDSf
with both oxygenation index and PaO 2/FiO
2. AVDSf did not discriminate RV dysfunction (AUROC for
RV GLS was 0.51, 95% CI 0.36-0.66). Conclusion: AVDSf at PARDS onset
was not associated with RV systolic dysfunction or PH within 24 hours
but was associated with metrics of hypoxemia and may be more reflective
of pulmonary causes of ventilation-perfusion mismatch. Future
investigations should focus on clarifying the clinical utility of AVDSf
in relation to existing metrics throughout the course of PARDS.