[End tidal PCO(2) for evaluation of severity of disease in idiopathic pulmonary arterial hypertension and chronic thromboembolic pulmonary hypertension].

Objective: To explore the difference in end tidal PCO(2) (P(ET)CO(2)) between idiopathic pulmonary arterial hypertension (IPAH) and chronic thromboembolic pulmonary hypertension (CTEPH), and to analyze the correlation between P(ET)CO(2) and the indexes of disease severity in IPAH and CTEPH patients. Methods: Data were retrieved from 68 IPAH patients and 52 CTEPH patients who all had received right-heart catheterization, pulmonary function test and cardiopulmonary exercise testing at Shanghai Pulmonary Hospital from October 2011 to October 2014. In addition, other clinical parameters were also collected. Results: The IPAH group had a significantly higher mPAP, PVR [(60±16) mmHg (1 mmHg=0.133 kPa), (13±6) Wood U ] than the CTEPH group [(46±12) mmHg, (9±4) Wood U, t=4.90, 4.83, all P<0.01]. Meanwhile, the IPAH group had a lower percentage of predicted peakVO(2), oxygen pulse [(45±15)%, (60±22)%] compared with the CTEPH group [(53±16)%, (68±21)%, t=-2.42, -1.96, all P<0.05]. The value of P(ET)CO(2) at rest, AT, peak in the IPAH patients [(27±5), (28±7), (25±7) mmHg] were higher than those in the CTEPH patients [(24±4) mmHg, (23±6) mmHg, (21±6) mmHg, t=3.22-4.54, all P<0.01]. There was a significantly difference in P(ET)CO(2) at AT and peak between WHO-FC Ⅰ-Ⅱ and Ⅲ-Ⅳ subgroups in IPAH (t=2.55, 2.60, all P<0.05) and CTEPH (t=2.39, P<0.05), except for P(ET)CO(2) at peak in the CTEPH patients (t=1.71, P>0.05). A moderately inverse correlation was found between P(ET)CO(2) at AT and NT-proBNP in the IPAH group (r=-0.58, P<0.01), meanwhile P(ET)CO(2) at AT in the CTEPH group was weakly correlated with NT-proBNP (r=-0.34, P<0.05). Conclusions: Compared with the CTEPH patients, the IPAH patients had significantly decreased exercise capacity and increased P(ET)CO(2). P(ET)CO(2) could reflect the disease severity in both IPAH and CTEPH patients, being superior in IPAH than in CTEPH. Furthermore, P(ET)CO(2) at AT might be better than P(ET)CO(2) at peak in reflecting the ventilatory efficiency.