Year : 2007  |  Volume : 1  |  Issue : 1  |  Page : 10

The effect of positive pressure ventilatory patterns on post-bypass lung functions

1 Anaesthesia Department, College of Medicine, King Fahad Cardiac Center, King Saud University, Saudi Arabia
2 Consultant Cardiac Anaesthesia, King Khalid University Hospital, Saudi Arabia

Correspondence Address:
Mohamed Essam Abdel-Meguid
Anaesthesia Department, College of Medicine, King Fahad Cardiac Center, King Saud University, Riyadh
Saudi Arabia
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Source of Support: None, Conflict of Interest: None

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Background: This study aimed at evaluating the effect of application of different patterns of positive ventilatory pressure either during or after cardiopulmonary bypass (CPB) on lung functions. Methods: 30 patients undergoing coronary artery revascularisation under the management of CPB were randomly allocated into 3 groups. Group I (VCM) 10 patients were subjected to manual vital capacity manoeuvre (VCM) before weaning off the CPB. Group II (CPAP) 10 patients were subjected to continuous positive airway pressure (CPAP) of 10 cmH 2 O during CPB. Group III (PEEP) 10 patients were subjected to positive end expiratory pressure (PEEP) of 7 cmH 2 O after weaning off the CPB. Measurements included the PO 2 , PCO 2 , together with derived calculated parameters as the alveolar-arterial oxygen difference [P (A-a) DO2] and shunt fraction, as well as the dynamic lung compliance being recorded directly from the anaesthetic and ventilatory equipments. All readings were taken on closed chest and on FiO 2 of 0.5. Intraoperative anaesthetic and surgical data as well as postoperative extubation time and length of ICU stay were also evaluated. Results: Statistical analysis of ventilatory parameters showed no significant differences for both PO 2 and PCO 2 in between the studied groups. Alveolar-Arterial oxygen difference mean values were comparable in the 3 studied groups. The mean values of intrapulmonary shunt fraction showed a significant difference in relation to the baseline values in Group I (VCM) and Group III (PEEP) at 30 minutes after ICU admission and 4 hours post CPB with estimated P value <0.01 and < 0.05 respectively, while in Group II (CPAP) mean values started to be significant after chest closure with a p value <0.05, but there was no significant intergroup differences with a P value > 0.01. Dynamic lung compliance mean values showed no intergroup statistical significance. Conclusion: Maintenance of Ventilatory parameters was achieved in all the positive pressure ventilatory methods applied, either being applied during or after CPB.

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