Patient-ventilator flow dyssynchrony
- 1 October 1997
- journal article
- clinical trial
- Published by Wolters Kluwer Health in Critical Care Medicine
- Vol. 25 (10) , 1671-1677
- https://doi.org/10.1097/00003246-199710000-00016
Abstract
Patient-ventilator flow dyssynchrony occurs when ventilator flow delivery is insufficient to meet patient demands. If sufficiently severe, flow dyssynchrony can produce significant imposed loads on ventilatory muscles. Flow dyssynchrony can be improved by increasing ventilator flow delivery. We hypothesized that the variable flow pressure-limited breath would be a better approach for matching patient flow demands than adjusting a set flow on a conventional volume-cycled breath. Clinical interventional study. Medical intensive care unit. Sixteen stable, mechanically ventilated patients receiving volume-cycled assist-control ventilation. Flow dyssynchrony was produced by reducing the set flow by 50%. Dyssynchrony was quantified by measuring the esophageal pressure time product during the assisted breath. Two strategies were then employed in an attempt to reduce the dyssynchrony. One strategy was to increase flow back to the initial set flow and then further increase flow by an additional 25% (VI strategy). The other strategy was to use a pressure-limited breath feature coupled to a volume assist breath (the P strategy). With the P strategy, the pressure limit was set at 75% and 100% of the static elastic recoil pressure at end-inspiration. Pressure time product, intrinsic positive end-expiratory pressure, and the ventilatory pattern were measured with each strategy and were analyzed by analysis of variance. Induced baseline flow dyssynchrony, as measured by the pressure time product, was > 5 cm H2O/sec in ten of 16 patients. This dyssynchrony was significantly reduced by both the VI strategy and the P strategy, although the P strategy appeared to be more effective in those patients with the greatest baseline dyssynchrony. Baseline inspiratory time was also shortened by both the VI strategy and the P strategy; the VI strategy shortened baseline inspiratory time more than the P strategy. Baseline tidal volume, frequency, and intrinsic positive end-expiratory pressure were only minimally affected by either strategy. The pressure-limited, variable-flow approach to ventilator gas delivery appears to be more responsive to a vigorous patient effort than a fixed-flow approach.Keywords
This publication has 38 references indexed in Scilit:
- Combining pressure-limiting and volume-cycling features in a patient-interactive mechanical breathCritical Care Medicine, 1994
- Regulation of Inspiratory Neuromuscular Output during Synchronized Intermittent Mechanical VentilationAnesthesiology, 1994
- Imposed work of breathing and methods of triggering a demand-flow, continuous positive airway pressure systemCritical Care Medicine, 1993
- Pressure Support Ventilation Decreases Inspiratory Work of Breathing During General Anesthesia and Spontaneous VentilationAnesthesia & Analgesia, 1992
- Oxygen Cost of Breathing and Diaphragmatic Pressure-Time IndexChest, 1990
- The Nagoya Conference on System Design and Patient-Ventilator Interactions During Pressure Support VentilationChest, 1990
- Diaphragmatic Contraction during Assisted Mechanical VentilationChest, 1989
- Additional work of breathing imposed by endotracheal tubes, breathing circuits, and intensive care ventilatorsCritical Care Medicine, 1989
- Oxygen Cost of Breathing in Postoperative PatientsChest, 1988
- Bedside Estimation of the Inspiratory Work of Breathing during Mechanical VentilationChest, 1986