Article

Patients affected by pulmonary arterial hypertension (PAH) show a reduced
exercise tolerance with early occurrence of dyspnoea and fatigue. The origin of
functional capacity limitation is multifactorial and several mechanisms have been
proposed, including right heart failure, which leads to a limited increase in
cardiac output during exercise, and hyperventilation with a reduced perfusion of
properly ventilated alveoli. In addition, abnormalities in arterial blood gases
are observed, with the occurrence of hypoxemia and hypocapnia, related to an
abnormal ventilation/perfusion match, gas diffusion abnormalities, low mixed
venous oxygen saturation and to the development of intra- and extra-pulmonary
right-to-left shunts. At present, the 6-minute walking test is the most used
method to assess exercise tolerance in PAH; it is also useful to monitor the
response to therapy and provides prognostic information. However, the assessment
of functional capacity by cardiopulmonary exercise test (CPET) seems to be more
complete, because CPET allows for discrimination between the metabolic,
cardiovascular and pulmonary components of exercise limitation. Moreover, CPET
estimates the severity of disease and assesses patients' prognosis and response
to therapy. In PAH, a typical CPET-response is observed, characterized by a
severe reduction in peak VO2, work rate, O2 pulse and anaerobic threshold and by
a marked increase in VE/VCO2 slope and in the dead space to tidal volume ratio.
However, the use of CPET should be limited to experienced centres. This review
will focus on resting lung function and exercise tolerance tests, showing that
CPET can provide the physiological explanation of functional limitation in PAH.

Langue : ANGLAIS