End tidal CO(2) tension: pulmonary arterial hypertension vs pulmonary venous hypertension and response to treatment.

Hemnes AR, Pugh ME, Newman AL, Robbins IM, Tolle J, Austin ED, Newman JH
Chest. 2011 140 (5): 1267-1273

PMID: 21622547 · PMCID: PMC4694178 · DOI:10.1378/chest.11-0155

BACKGROUND - CO(2) excretion is impaired in pulmonary arterial hypertension (PAH) due to underlying vascular obstruction and increased dead space. Our aim was to determine whether resting end tidal CO(2) (Etco(2)) could differentiate patients with PAH from those with pulmonary venous hypertension (PVH) or patients without pulmonary hypertension (PH) and whether successful treatment of PAH resulted in higher Etco(2) values.

METHODS - We performed Etco(2) measurements for five breaths at rest and after a 6-min walk test (6MWT) in patients seen at our pulmonary vascular center. Mean Etco(2) values were correlated with 6-min walk distance and right-sided heart catheterization data.

RESULTS - We enrolled 84 patients with PAH, 17 with PVH without left ventricular systolic dysfunction, and seven with no PH and no severe alterations in pulmonary function testing. Etco(2) was significantly lower in patients with PAH than in those with no PH and PVH (P < .0001 PAH vs both groups). Etco(2) correlated with the pulmonary artery diastolic pressure-to-pulmonary artery occlusion pressure gradient (r = -0.50, P = .0002) and pulmonary vascular resistance (r = -0.44, P = .002). Etco(2) after 6MWT correlated with walk distance (r = 0.34, P = .003). In patients with prostaglandin therapy escalation, Etco(2) increased in those who had clinical improvement, whereas in patients who did not improve clinically, Etco(2) failed to rise (P = .04).

CONCLUSIONS - Etco(2) is a promising tool to differentiate patients with PAH from those with PVH or no PH, correlates with diagnostic and prognostic hemodynamic indicators, and may increase with successful treatment of PAH.

MeSH Terms (18)

Adult Antihypertensive Agents Area Under Curve Capnography Carbon Dioxide Case-Control Studies Epoprostenol Exercise Test Female Hemodynamics Humans Hypertension, Pulmonary Male Middle Aged Prospective Studies Statistics, Nonparametric Tidal Volume Treatment Outcome

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