Non-invasive Mechanical Ventilation After Cardiac Surgery

Effects of Non-invasive Mechanical Ventilation on Hemodynamics and Gas Exchanges Parameters After Cardiac Surgery in Patients With Relative Hypoxemia

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, the investigators objective was to study its effects in the oxygenation index (PaO2/FiO2) and in hemodynamic variables in this group of patients.

• Postoperative cardiac surgery patients having a Swan-Ganz catheter and showing a PaO2/FiO2 between 150 and 300 (with FIO2 0.31), one hour after extubation, were included.
• Then, the patients were randomized into two groups: control and intervention group. Intervention group used NIV with a bi-level positive airway pressure (an inspiratory pressure to generate a tidal volume of 6ml/kg and an expiratory pressure of 7cmH2O) with a FIO2 0.4. Control group used oxygen by Venturi mask(FIO2 0.4) in order to keep a good oxygenation.
• In both groups measurements were done in basal situation, one and three hours after beginning the treatment and one hour after stop the treatment (FiO2 0.31).
• Variables studied included: PaO2/FiO2, PaO2, PaCO2, heart rate (HR), mean arterial pressure (MAP), pulmonary capillary wedge pressure (PCWP) and cardiac output (CO).

Inclusion Criteria:

• Oxygenation index (PaO2/FiO2)between 150 and 300 one hour after extubation following cardiac surgery.
• Swan-Ganz catheter

Exclusion Criteria:

• Invasive mechanical ventilation more than 24 hours
• Serious obstructive pulmonary chronic disease (FEV1<40%)