Effects of various weaning methods from mechanical ventilation on hemodynamics and arterial oxygenation after open heart surgery
Osaka, S.
Nihon Kyobu Geka Gakkai 34(11): 1892-1902
1986
ISSN/ISBN: 0369-4739 PMID: 3819489 Document Number: 271384
In order to elucidate the efficacy and clinical usefulness of the various weaning methods from mechanical ventilation after open heart surgery, hemodynamic monitoring and blood gas analysis were performed from weaning period to 24 hours after extubation. Twenty one adult patients were divided into three groups (7 of each) for three different weaning methods, including T-piece, IMV using Servo ventilator 900B and high frequency jet ventilation (HFJV) superimposing spontaneous breathing. FiO2 was strictly kept in 0.4 in the whole period. In three groups, hemodynamic responses were very similar; mean BP, CI, HR, and PAP, PCWP and pulmonary vascular resistance increased during weaning period and this tendency persisted in early post-extubation period although stroke volume index and total vascular resistance did not change in the whole period. On the other hand, arterial oxygen tension (PaO2) was well maintained during weaning period but decreased in early post-extubation period (Maxiumum at 3 hours after extubation) in all groups. This post-extubation arterial oxygen drop was significant in T-piece group (143.2 .+-. 32.9 mmHg before weaning to 116 .+-. 27.1 mmHg 3 hours after extubation, p < 0.05) with an increase in intrapulmonary shunt. This phenomenon was presumably due to alveolar collapse caused by sudden change from IPPV to spontaneous breathing. PaO2 drop continued until 24 hours after extubation in T-piece although in the other two groups PaO2 restored very quickly. In IMV group, PaO2 decreased again at 24 hours after extubation but in HFJV group PaO2 was maintained until 24 hours. There was a favorable physiotherapeutic effect of HFJV during weaning period that facilitated raising sputum. It was concluded that a new respiratory mode, HFJV superimposing spontaneous breathing was a satisfactory weaning method from mechanical ventilation after open heart surgery from a view point of arterial oxygenation after extubation.