OBJECTIVE: To assess cardiorespiratory variables during weaning from mechanical ventilation by using the T-tube and pressure support techniques, and to compare them in groups of patients with and without heart disease. METHODS: To assess the following parameters of 20 patients (57±15 years) undergoing weaning from mechanical ventilation: oxygenation; CO2 elimination; respiratory and heart rates; tidal and minute volumes; blood pressure; and electrocardiographic alterations. Data were recorded by using both techniques at the following times: zero, 15, and 30 minutes, and after a 30-minute interval. The patients were divided into 2 groups, with heart disease (n=11) and without heart disease (n=9), and then compared. RESULTS: The pressure support ventilation showed significantly more elevated oxygenation and CO2 elimination values, and reduced respiratory rate as compared with those of the T-tube ventilation. No difference was found in regard to blood pressure and heart rate. More patients with heart disease had alterations in the ST segment [7 (64%) patients versus 2 (22%)] and arrhythmias [3 (27%) versus 1 (11%)], as compared with patients without heart disease. A lower frequency of tachycardia was observed in those with heart disease. CONCLUSION: When comparing pressure support ventilation with T-tube ventilation, a better response was observed in the measurements of the respiratory and oxygenation parameters when using pressure support ventilation. No significant difference was observed in the measurements of cardiovascular parameters. In both weaning techniques, patients with heart disease had tachycardia less frequently, more alterations in the ST segment, and a greater tendency towards the occurrence of arrhythmias.
mechanical ventilation; myocardial ischemia; weaning
