Noninvasive measurement of the systolic time intervals is a routine procedure for the determination of myocardial performance, even in subjects without clinical or electrocardiographic signs of cardiopathy. Statistically significant differences in pre-ejection period (PEP) and PEP/left ventricular ejection time (LVET) between days and between observations were demonstrated by Levi et al. A high correlation between systolic time intervals and catecholamines was recorded. The aim of the present study was to evaluate the spontaneous modifications in pulmonary and cardiac parameters during a stressful situation, such as right heart catheterization. Seventeen patients with chronic obstructive lung disease (COLD) underwent right heart catheterization. Heart rate (HR), systemic artery pressure (SAP), pulmonary artery pressure (PAP), cardiac output (Q'c), cardiac index (CI), systolic stroke volume (SV), respiratory rate (RR), minute ventilation (V'E), oxygen consumption (V'O2), carbon dioxide production (V'CO2), their ratio (RQ), arterial and venous O2 and CO2, systolic time intervals (total electromechanical interval (QS2), LVET, PEP, PEP/LVET), total pulmonary resistance (TPR), adrenaline (A), and noradrenaline (NA) were recorded at the beginning of the test and 20, 40, 60 and 80 min thereafter. Analysis of variance (ANOVA) showed significant differences between the observations for systolic pulmonary artery pressure (SPAP), Q'c, V'O2, V'CO2, V'E, PEP/LVET, and NA. In conclusion, it is necessary to take into account spontaneous modifications in pulmonary haemodynamic parameters following a stressful situation, such as a catheterization, when studying the effects of drugs such as vasodilators and vasoactive agents.