[Effect on hemodynamics during different modes of low assist ventilation].
OBJECTIVE
To observe the effect on mechanical ventilation with biphasic positive airway pressure (BIPAP), pressure support ventilation (PSV) and proportional pressure support (PPS) modes on hemodynamics in patients with either normal cardiac function or impaired cardiac function in order to optimize the time to wean mechanical ventilation in patients with severe cardiac dysfunction.


METHODS
Non-invasive cardiac output (NICO) monitoring was instituted in patients 32 with respiratory failure due to different causes, when spontaneous respiration was restored, and they were separated into two groups depending on whether the cardiac index (CI) was normal (CI> or =2.0 L.min(-1).m(-2)) or not (CI<2.0 L.min(-1).m(-2)). The effects of BIPAP, PSV and PPS modes on changes in hemodynamics were compared between two groups.


RESULTS
(1) In patients with normal cardiac function, CO, CI, stroke volume (SV), pulmonary capillary blood flow (PCBF) were significant higher in PSV and PPS modes than BIPAP mode, and they were highest with PPS mode, but no significant difference compared with PSV. Surround vascular resistance (SVR) was reduced significantly in PPS mode compared with BIPAP, but no significant difference was found compared with PSV. (2) In patients with cardiac dysfunction, CO, CI increased gradually when ventilated in BIPAP, PSV, PPS modes and significant difference was found among three groups. In PPS mode, CO and CI were highest. (3) The trends of peak airway pressure (Ppeak) and mean airway pressure (Pmean) were degressive in three groups. In both normal cardiac function group and cardiac dysfunction group, significant difference was found in PSV and PPS modes compared with BIPAP. Ppeak was lowest in PPS mode in cardiac dysfunction group, and there was significant difference compared with the other groups. (4) The ventilated time was significant reduced in PPS mode compared with PSV. (5) In normal cardiac function group, instinct positive end expiratory pressure (PEEPi) showed degressive trend among three different modes, and it was lowest in PPS mode, with significant difference compared with the other two groups.


CONCLUSIONS
In PPS mode, the effect to hemodynamics in patients with severe cardiac dysfunction is minimal, so it is suitable as a weaning mode in this groups of patients.
Xu
Lei
L
Department of Intensive Care Unit, Tianjin Third Central Hospital, Tianjin 300170, China.
Zhang
Na-xin
NX
Qin
Ying-zhi
YZ
Zhan
Chun
C
Wang
Shu-peng
SP
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002302:Cardiac Output; D005260:Female; D006321:Heart / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D008991:Monitoring, Physiologic; D012121:Respiration, Artificial / Q000379:methods*; D012131:Respiratory Insufficiency / Q000503:physiopathology* / Q000628:therapy*