Under Open Lung Conditions Inverse Ratio Ventilation Causes Intrinsic Peep and Hemodynamic Impairment

  • Agneta M. Markström
  • Michael Lichtwarck-Aschoff
  • Anders J. Hedlund
  • K. Anders Nordgren
  • Ulf H. Sjöstrand

Abstract

Inverse ratio ventilation (IRV) is commonly used in clinical practice. Several studies have used IRV in order to recruit collapsed alveoli. In a randomised trial in twelve surfactant depleted piglets, the lungs were ventilated with sufficient positive end-expiratory pressure (PEEP) to prevent end-expiratory collapse, and the effects of increased inspiration-to-expiration (I:E ratio) were evaluated. Pressure regulated ventilation (with I:E of 1:1, constant tidal volume and decelerating inspiratory flow) was used at 30 breaths per minute (bpm). I:E ratios of 1.5:1,2.3:1 and 4:1 were applied sequentially. When the I:E ratio was increased, external PEEP had to be reduced in order to keep total PEEP constant. Functional residual capacity, airway pressures, gas exchange, extra-thermal volume and hemodynamics were measured. With I:E ratios above 2:1 intrinsic PEEP was generated and with concomitant decrease in cardiac index. PaO2 was not affected, but oxygen delivery was reduced. It is concluded that I:E ratios of 2:1, or above, generate increased intrinsic PEEP with compromised hemodynamics.

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Published
1996-07-29
How to Cite
Markström A. M., Lichtwarck-Aschoff M., Hedlund A. J., Nordgren K. A., & Sjöstrand U. H. (1996). Under Open Lung Conditions Inverse Ratio Ventilation Causes Intrinsic Peep and Hemodynamic Impairment. Upsala Journal of Medical Sciences, 101(3), 257-272. https://doi.org/10.3109/03009739609178925
Section
Original Articles

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