Effects of non-invasive mechanical ventilation on hemodynamic and gas exchanges parameters after cardiac surgery in patients with 300 >PaO2/FiO2 >150

Abstract

INTRODUCTION: Non-invasive mechanical ventilation (NIV) has been used in hypoxic post-operative cardiac patients but more studies are necessary to clarify its respiratory and hemodynamic effects. Therefore, our objective was to study its effects in the oxygenation index (PaO2/FiO2) and in hemodynamic variables in this group of patients. METHODS: This is a randomized trial in which all post-operative cardiac patients since April 2008, having a Swan-Ganz catheter and showing a PaO2/FiO2 between 150 and 300 (with FIO2 0.31), 1 h after extubation, were included. Intervention group used NIV with a bilevel positive airway pressure (an inspiratory pressure to generate a tidal volume of 6 ml/kg and an expiratory pressure of 7cmH2O) with a FIO2 0.4. Control group used oxygen by Venturi mask in order to keep a good oxygenation. In both groups measurements were done in basal situation and 1 h after beginning the treatment. Variables studied included: PaO2/FiO2, PaO2, heart rate (HR), mean arterial pressure (MAP), pulmonary capillary wedge pressure (PCWP) and cardiac output (CO) (Table 1) (Table presented). RESULTS: Until now, 36 patients were included (20 male and 16 female). The most important results are shown in the table below. CONCLUSION: These preliminary results showed that NIV with bi-level pressure improves oxygenation without significant hemodynamic changes, except a small increase in PCWP and a trend to decrease in HR.