[A comparative study of the effects on the left ventricular function of 2 methods of noninvasive ventilation: NIPPV...

Among the non-invasive ventilatory methods, the Nasal Intermittent Positive Pressure Ventilation (NIPPV) can cause important effects on circulation since a positive intrathoracic pressure is obtained and thus in the transmural cardiac pressure. In contrast, the External High Frequency Oscillation around a Negative Baseline (EHFO-NB) obtains a negative thoracic pressure. Therefore, the opposite circulatory changes should be expected.

To study and compare the effects on the left systolic and diastolic ventricular functions derived from the application of both NIPPV and EHFO-NB ventilatory support methods in patients with chronic obstructive pulmonary disease (COPD).

Nine patients with COPD were studied. The investigation was carried out from the third to the seventh day of follow-up at the ICU. For each patient three equilibrium radionuclide angiocardiography (ERA) were performed. With the patient breathing room air spontaneously, 45 minutes after ventilatory support with NIPPV and also 45 minutes after ventilatory support with EHFO-NB. Measurements of radionuclide activity (counts) and derived parameter of left systolic and ventricular functions were determined following a previously reported protocol.

During ventilatory support with NIPPV a significant increase in the time elapsed since the end of the diastole to the peak systolic ejection was observed. During ventilatory support with EHFO-NB a significant decrease in cardiac radioactivity (counts) in tele-systole was observed together with an increase in the ejection velocity measured in the first third of the systolic phase. These findings occurred both with respect to the basal situation and to the ventilatory phase with NIPPV:

Under the study conditions, none of the non-invasive ventilatory support methods compromised hemodynamic parameters in patients studied. Ventilation with EHFO-NB improved the left ventricular function.