Source: Annual Congress 2011 - Physiology of human pulmonary hypertension
Disease area: Pulmonary vascular diseases

Abstract

INTRODUCTION: Pulmonary hypertension (PH) is a disease of elevated pulmonary artery pressure leading to the inability of the overloaded right ventricle to adapt pulmonary blood flow (PBF) and systemic oxygen delivery to peripheral tissue oxygen demand. 6 minutes walk test (6MWT) is a submaximal, well tolerated but strenuous test regularly used for the assessment of PH functional status and is strongly associated to survival.
AIM: To study the adaptation of PBF during a 6MWT.
METHODS: We measured heart rate (HR) and PBF with a rebreathing device (INNOCOR) before and directly after a 6MWT in 28 patients with chronic thromboembolic pulmonary hypertension and 8 with pulmonary arterial hypertension. The relation between increase (after – before 6MWT) in PBF (ΔPBF) in response to 6MWdistance (6MWD) was plotted and different mathematical model applied to describe the relation (Akaike test).
RESULTS/DISCUSSION: The best fitting model is a polynomial cubic model, showing a small and constant ΔPBF for patients walking less than 300-350 m but more rise in ΔPBF is observed with increased distance.

We notice that the rise in ΔPBF occurs at comparable 6MWD that is associated with better survival in PH. The stroke volume (PBF/HR) is not increased whatever the distance covered.
CONCLUSIONS: Ability to substantially increase PBF determines 6MWD and is dependent on chronotropic response in patient with PH.

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Citations should be made in the following way:
G. Deboeck, R. McKenzie Ross, L. Sharples, J. Pepke-Zaba (Papworth, United Kingdom). Incapacity to increase pulmonary blood flow determines 6 minutes walking distance in pulmonary hypertension. Eur Respir J 2011; 38: Suppl. 55, 2311

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