End-Tidal Carbon Dioxide as a Prognostic Feature in Pulmonary Arterial Hypertension.

Rationale: Pulmonary arterial hypertension (PAH) is characterized in part by increased dead space ventilation, which can be estimated noninvasively at the bedside by measurement of end-tidal CO (ETco).

Objectives: Prior work has demonstrated that ETco is lower in patients with PAH than in control patients, but whether ETco has prognostic value is unknown. We hypothesized that lower measurements of ETco in patients with PAH correlate with worse long-term outcomes.