LAUSR

An increase of Pulmonary Arterial Systolic Pressure (PASP) during exercise in Pulmonary Arterial Hypertension(PAH) may indicate a good functional reserve of right ventricle. Volumetric Capnography(VCap) can reveal the ventilatory pattern of these patients. Objectives: to evaluate the ventilatory pattern of PAH patients and to correlate the findings with stress echocardiography (SE) variables. Methods: cross-sectional study, 14 idiopathic PAH patients and 14 healthy controls. All subjects underwent VCap, SE and spirometry. Arterial blood gases were determined (PAH group). Study was approved by the Ethics Commitee. Results: PAH patients had hypocapnia (mean CO2=29.5 mmHg). Spirometry: 57.1% of PAH patients (none of controls) showed FVC below the lower limit of normality. VCap: PAH patients had higher respiratory rate (RR)(16.9x13.4; p=0.020) and lower CO2/breath(10.6x16.4; p=0.012) than controls. Correlation analysis: reduced FVC was associated to smaller increases in tricuspid regurgitation velocity(TRV) during SE. Comments: Although PAH patients had lower arterial CO2 levels, VCap showed similar tidal volumes but a higher RR. Hypocapnia does not justifiy the need for such high ventilation pattern. Expanding the lungs seems to be easy for PAH patients. The persistent reduction of the total amount of blood in the lungs at any moment increases pulmonary compliance and reduces pulmonar elasticity. Reduced FVC was present in more than half of the PAH patients and the smaller FVC the smaller the increase in TRV during SE. Mechanical alterations in the lungs of PAH patients may explain the reduced FVC and may be linked to other findings such as reduction in Inspiratory capacity at rest, and dynamic hyperinflation during exercise.