Objective: To study the efficacy and safety of non-invasive positive pressure ventilation (NPPV) in the care of dyspnea after cardiac surgery.
Methods: Among patients who underwent cardiac surgery with cardiopulmonary bypass from December 2004 to December 2006,58 patients developed dyspnea (respiratory rate>25 breaths per minute with "three depressions" sign) and acute respiratory failure after extubation. Among them 30 patients underwent NPPV and 28 patients were treated with face mask oxygen therapy. Intubation and invasive mechanical ventilation were begun when the treatment failed or still hypoxemic [partial pressure of oxygen in artery (PaO(2))<60 mm Hg (1 mm Hg=0.133 kPa)], ventricle arrhythmia, or other indications for endotracheal intubation.
Results: No significant differences were found between two groups in age,acute physiology and chronic health evaluation II (APACHE II) score,duration of cardiopulmonary bypass and aortic cross-clamp, and New York Heart Association class (all P>0.05). Compared with face mask oxygen therapy group, NPPV was associated with a lower incidence of arrhythmia (P<0.05) at 120 minutes after treatment, a lesser necessity for reintubation (P<0.01), a shorter length of stay in intensive care unit (ICU) (P<0.01), a lower mortality (P<0.05). Arterial pH and arterial CO(2) partial pressure (PaCO(2)) of two groups began to rise significant at 480 minutes (P<0.05 or P<0.01), PaCO(2) began to rise at 120 minutes (P<0.05). At 30 minutes, significant differences in PaO(2), HCO(-)(3), respiratory rate, heart rate and arterial systolic blood pressure in NPPV group began to appear (P<0.05 or P<0.01). The time of significant differences in PaO(2), HCO(-)(3), respiratory rate, heart rate and arterial systolic blood pressure in face mask oxygen therapy group were respectively 120, 60, 120, 480 and 480 minutes (P<0.05 or P<0.01). Lactate concentration showed a significant drop at 60 minutes in NPPV (P<0.05), but at 480 minutes in face mask oxygen therapy group (P<0.05).
Conclusion: These results suggest that NPPV is an effective and safe means for improving dyspnea and tissue perfusion, decreasing arrhythmia and necessity for reintubation, shortening the length of stay in ICU and decreasing mortality in dyspneic patients after cardiac surgery.