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Improvement of cardiac output with BiLevel ventilation in patients with high airway pressures


Studies have shown that airway pressure release ventilation increases cardiac output when compared with synchronized intermittent mandatory ventilation (SIMV). This occurs by allowing more spontaneous ventilation, which increases venous return. BiLevel ventilation is a form of augmented pressure ventilation that allows for spontaneous breathing at any moment of the ventilatory cycle. The purpose of this study is to determine whether BiLevel increases cardiac output when compared with SIMV.


Patients on a ventilator with high peak airway pressures in an intensive care unit from December 2000 to November 2002 were studied. Patients with respiratory failure were initially managed with SIMV. If the peak airway pressure persistently remained greater than 40 cmH2O, patients were changed to BiLevel using a Puritan-Bennett 840 ventilator. Cardiac output measurements were made while on SIMV and after being converted to BiLevel. Results were compared using a paired Student t test.


Thirty-six patients met criteria for the study. Thirteen patients developed respiratory failure from sepsis, 11 from trauma, seven from pneumonia, two from congestive heart failure, one from variceal bleeding, one with renal cell cancer and one after a lung lobectomy. Twenty-five patients (69%) increased their cardiac output after being changed to BiLevel. In 11 patients with a PaO2 A–a gradient > 500, five (45%) increased their cardiac output. Overall results are as presented in Table 1. There was no significant difference in the systemic vascular resistance and wedge pressure.

Table 1


BiLevel can increase cardiac output in most patients at lower airway pressures when compared with SIMV. It is less likely to increase cardiac output in patients with severe lung injury. Further studies are needed to determine whether this improvement in cardiac output will affect outcome.

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Ziegler, D., Burch, V., Geno Tellez, M. et al. Improvement of cardiac output with BiLevel ventilation in patients with high airway pressures. Crit Care 7, P167 (2003).

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  • Cardiac Output
  • Respiratory Failure
  • Airway Pressure
  • Systemic Vascular Resistance
  • Renal Cell Cancer