Pulmonary vascular distensibility predicts aerobic capacity in healthy individuals

Key points Pulmonary transit of agitated contrast (PTAC) occurs during exercise in healthy individuals. It has been suggested that positive PTAC reflects a greater pulmonary vascular reserve, allowing for the right ventricle to operate at a decreased afterload at high levels of exercise. In this study, we determined whether individuals with highest maximal aerobic capacity have the greatest pulmonary vascular distensibility, highest PTAC and greatest increase in the capillary blood component of lung diffusing capacity during exercise. We observed that individuals with highest maximal aerobic capacity have a more distensible pulmonary circulation as observed through greater pulmonary vascular distensibility, greater pulmonary capillary blood volume, and lowest pulmonary vascular resistance at maximal exercise. Pulmonary vascular distensibility predicts aerobic capacity in healthy individuals. Abstract It has been suggested that shallow slopes of mean pulmonary artery pressure (MPPA)cardiac output () relationships and pulmonary transit of agitated contrast during exercise may be associated with a higher maximal aerobic capacity (). If so, individuals with a higher could also exhibit a higher pulmonary vascular distensibility and increased pulmonary capillary blood volume during exercise. Exercise stress echocardiography was performed with repetitive injections of agitated contrast and measurements of MPPA, and lung diffusing capacities for carbon monoxide (DL,CO) and nitric oxide (DL,NO) in 24 healthy individuals. A pulmonary vascular distensibility coefficient a was mathematically determined from the slight natural curvilinearity of multipoint MPPA plots. Membrane (Dm) and capillary blood volume (Vc) components of lung diffusing capacity were calculated. Maximal exercise increased MPPA, cardiac index (CI), DL,CO and DL,NO. The slope of the linear best fit of MPPACI was 3.2 +/- 0.5 mmHg min l-1 m2 and a was 1.1 +/- 0.3% mmHg-1. A multivariable analysis showed that higher a and greater Vc independently predicted . All individuals had markedly positive pulmonary transit of agitated contrast at maximal exercise, with increases proportional to increases in pulmonary capillary pressure and Vc. Pulmonary transit of agitated contrast was not related to pulse oximetry arterial oxygen saturation. Therefore, a more distensible pulmonary circulation and a greater pulmonary capillary blood volume are associated with a higher in healthy individuals. Agitated contrast commonly transits through the pulmonary circulation at exercise, in proportion to increased pulmonary capillary pressures.