Hemodynamic and ventilatory effects associated with increasing inverse inspiratory-expiratory ventilation

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15 Scopus citations

Abstract

Background: Increasing the percentage of inspiratory time during mechanical ventilation (i.e., inverse inspiratory-expiratory (I:E) ventilation) is frequently used to improve oxygenation in patients with acute respiratory distress syndrome; however, an optimal I:E ratio is unknown. Methods: To assess for an optimal I:E ratio, hemodynamic, ventilatory, and oxygenation parameters were determined in eight adult trauma patients with acute respiratory distress syndrome supported with pressure-control ventilation. An indwelling pulmonary artery catheter facilitated the extensive measurements as I:E ratios were randomly changed between 1:1 and 3:1. Measurements were determined 30 minutes after each change in the I:E ratio. Results: Increasing the percentage of inspiratory time resulted in a progressive increase in arterial oxygenation (p < 0.05) in conjunction with elevations in mean airway pressure (p < 0.05) and a decrease in alveolar- arterial oxygen difference (p < 0.05). Furthermore, progressive reversal of the I:E ratio significantly diminished alveolar ventilation (p < 0.01), with worsening dynamic compliance (p < 0.01). There were no demonstrable changes in hemodynamics. Conclusion: These findings demonstrate the effectiveness of increasing inspiratory time to improve oxygenation, yet to the detriment of ventilation. This suggests that within the parameter confines of this study, the preferential I:E ratio is a balance between oxygen demands and ventilatory requirements.

Original languageEnglish (US)
Pages (from-to)268-272
Number of pages5
JournalJournal of Trauma - Injury, Infection and Critical Care
Volume45
Issue number2
DOIs
StatePublished - Aug 1998

Keywords

  • ARDS
  • Oxygenation
  • Pressure-control ventilation
  • Trauma

ASJC Scopus subject areas

  • Surgery
  • Critical Care and Intensive Care Medicine

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