Effects of continuous (CPAP) and bi-level positive airway pressure (BiPAP) on extravascular lung water after extubation of the trachea in patients following coronary artery bypass grafting
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To evaluate the effects of continuous positive airway pressure (CPAP) and bilevel positive airway pressure (BiPAP) on extravascular lung water during weaning from mechanical ventilation in patients following coronary artery bypass grafting.
Prospective, randomized clinical study.
Intensive care unit at a university hospital.
Seventy-five patients following coronary artery bypass grafting.
After extubation of the trachea, patients were treated for 30 min with CPAP via face mask (n=25), with nasal BiPAP (n=25), or with oxygen administration via nasal cannula combined with routine chest physiotherapy (RCP) for 10 min (n=25).
Measurements and results
Extravascular lung water (EVLW), pulmonary blood volume index (PBVI) and cardiac index (CI) were obtained during mechanical ventilation (T1), T-piece breathing (T2), interventions (T3), spontaneous breathing 60 min (T4) and 90 min (T5) after extubation of the trachea using a combined dye-thermal dilution method. Changing from mechanical ventilation to T-piece breathing did not show any significant differences in EVLW between the three groups, but a significant increase in PBVI from 155±5 ml/m2 to 170±4 ml/m2 could be observed in all groups (p<0.05). After extubation of the trachea and treatment with BiPAP, PBVI decreased significantly to 134±6 ml/m2 (p<0.05). After treatment with CPAP or BiPAP, EVLW did not change significantly in these groups (5.5±0.3 ml/kg vs 5.0±0.4 ml/kg and 5.1±0.4 ml/kg vs 5.7±0.4 ml/kg). In the RCP-treated group, however, EVLW increased significantly from 5.8±0.3 ml/kg to 7.1±0.4 ml/kg (p<0.05). Sixty and 90 min after extubation, EVLW stayed at a significantly higher level in the RCP-treated group (7.5±0.5 ml/kg and 7.4±0.5 ml/kg) than in the CPAP-(5.6±0.3 ml/kg and 5.9±0.4 ml/kg). No significant differences in CI could be observed within the three groups during the time period from mechanical ventilation to 90 min after extubation of the trachea.
Mask CPAP and nasal BiPAP after extubation of the trachea prevent the increase in extravascular lung water during weaning from mechanical ventilation. This effect is seen for at least 1 h after the discontinuation of CPAP or BiPAP treatment. Fuether studies have to evaluate the clinical relavance of this phenomenon.
Key wordsWeaning CPAP BiPAP Extravascular lung water Cardiac surgery
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