Pediatric One-Lung Ventilation: Influence of Ventilatory Mode and Positive End-Expiratory Pressure
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- Category: Vol. 77, June 2009
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Pediatric One-Lung Ventilation: Influence of Ventilatory Mode and Positive End-Expiratory Pressure,MAGDA S. AZER
Abstract
Background: Optimization of ventilatory strategy during one-lung anesthesia is mandatory especially in vulnerable population like pediatric cancer patients. Volume-controlled ventilation (VCV) is a widely used mode, yet pressure-controlled ventilation (PCV) has been proposed to improve arterial oxygenation during OLV in adults. The aim of this study was to assess the pressure controlled ventilation as a tool to improve ventilatory management in pediatric one lung anesthesia and to study its effects on airway pressure, arterial oxygenation and hemodynamics in comparison to conventional volume controlled ventilation. The effect of application of PEEP was also evaluated in the two studied modes.
Methods: In this prospective controlled study, 30 pediatric patients undergoing elective thoracotomy requiring one-lung anesthesia were randomized into two equal groups to undergo either conventional volume control ventilation (VCV group) or pressure control ventilation (PCV group) with standardized anesthesia care. The study was divided into three stages; two-lung ventilation with the chosen mode of ventilation (TLV) in the lateral position. One-lung ventilation, with zero positive end-expiratory pressure (OLV-ZEEP) and the third stage of the study was to add 5cmH2O PEEP to both groups (OLV-PEEP5). Peak airway pressure (Ppeak), mean airway pressure (Pmean), plateau pressure (Pplat), expired tidal volume (Vex) and dynamic compliance (Cdyn) were recorded at each stage. Measurement of arterial oxygen tension (Pao2), arterial carbon dioxide tension (Paco2), arterial oxygen saturation (Sao2), pH and hemoglobin (HB). Hemodynamic variables were also recorded.
Results: Lower peak airway pressure in PCV group during OLV was observed compared to VCV group, Ppeak during the two stages of OLV (OLV-ZEEP, OLV-PEEP5), showed significantly lower values (22.5±0.9 in PCV, Vs 29.2±2.1 in VCV during OLV-ZEEP) and (22.9±1.6 in PCV, Vs 30.4±1.2 in OLV-PEEP5). The same pattern of significant changes was observed as regards Pplat. Improved arterial oxygenation during OLV in PCV group in comparison to VCV group (175.6±28 Vs 123.2±34) was observed. Pao2 values increased significantly after the application of the 5-cm H2O PEEP in the two groups comparably. The decrease in dynamic compli-ance that occurred after initiation of OLV in the VCV group was significantly greater than that occurred in PCV group during OLV (with or without PEEP).
Conclusion: This study demonstrated a favorable outcome of oxygenation with lower peak and plateau pressures during PCV in pediatric OLV compared to conventional VCV. Better preservation of ventilation perfusion ratio during PCV is suggested evidenced by improved dynamic compliance in PCV compared to VCV and that 5cm H2O PEEP improved oxygenation only in VCV during OLV.