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Chest. 2011 Nov;140(5):1284-1291. doi: 10.1378/chest.10-3357. Epub 2011 Apr 28.

Differences in ventilatory inefficiency between pulmonary arterial hypertension and chronic thromboembolic pulmonary hypertension.

Author information

1
Imperial College School of Medicine, Imperial College London, London, England; Respiratory and Critical Care Department, Beijing Institute of Respiratory Medicine, Beijing Chao-Yang Hospital, Capital Medical University, Beijing, China.
2
Department of Respiratory Medicine, Hammersmith Hospital, London, England.
3
Respiratory and Critical Care Department, Beijing Institute of Respiratory Medicine, Beijing Chao-Yang Hospital, Capital Medical University, Beijing, China.
4
Division of Experimental Medicine and Toxicology, Imperial College London, London, England.
5
National Pulmonary Hypertension Service (London), Hammersmith Hospital, Imperial College Healthcare NHS Trust, National Heart and Lung Institute, Imperial College London, London, England.
6
National Pulmonary Hypertension Service (London), Hammersmith Hospital, Imperial College Healthcare NHS Trust, National Heart and Lung Institute, Imperial College London, London, England. Electronic address: l.howard@imperial.ac.uk.

Abstract

BACKGROUND:

Measures of ventilatory efficiency during cardiopulmonary exercise testing (CPX) are increasingly being used as prognostic markers in heart failure and pulmonary hypertension (PH). Little is known about whether these measures can be applied to all forms of PH, in particular chronic thromboembolic pulmonary hypertension (CTEPH), wherein thrombotic vascular occlusion has an impact on gas exchange.

METHODS:

One hundred twenty-seven patients, 50 with CTEPH and 77 with pulmonary arterial hypertension (PAH), underwent incremental CPX.

RESULTS:

Physiologic ventilatory dead space fraction (Vd/Vtphys) measured at peak exercise with arterial blood gas analysis was higher in CTEPH than PAH (52.9% vs 41.8%, P < .001). The V(E)/V(CO(2)) slope was higher in patients with CTEPH than in patients with PAH (50.7 L/min/L/min vs 44.4 L/min/L/min, P = .024) and was mirrored by similar changes in the ventilatory equivalent for CO(2) at anaerobic threshold (Eqco(2)_AT) (47.7 L/min/L/min vs 42.0 L/min/L/min, P = .008). In a multivariate linear regression analysis, disease subtype was found to be an independent predictor of Vd/Vtphys (P < .001), V(E)/V(CO(2)) slope (P = .003), and Eqco(2)_AT (P < .001). These three measures could distinguish between World Health Organization functional classes I/II and III/IV in PAH but not CTEPH.

CONCLUSION:

Significant differences in gas exchange exist between CTEPH and PAH, due to differences in Vd/Vtphys likely as a result of vascular occlusion due to thromboembolic disease. This dissociates measures of ventilatory efficiency from disease severity and also contributes to our understanding of the differences in exercise limitation and breathlessness in PAH and CTEPH. Common prognostic end points from CPX cannot be applied to all forms of PH.

PMID:
21527511
DOI:
10.1378/chest.10-3357
[Indexed for MEDLINE]

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