Abstract
Background: Intrapulmonary percussive ventilation (IPV) in conjunction with conventional ventilation provides benefits for secretion clearance, improved oxygenation, and atelectasis[1]. Studies have shown IPV can cause dynamic hyperinflation and lung injury in patients receiving Volume Control ventilation (VC) [2]. Riffard et al demonstrate hyperinflation and auto-PEEP to be affected by extrinsic PEEP with higher extrinsic PEEP (PEEPex) diminishing auto-PEEP[2]. The goal of this study was to determine if hyperinflation and auto-PEEP would be increased if PEEPex were set to zero. To evaluate these effects, changes in peak pressure (Ppeak), plateau pressure (Ppause), and auto-PEEP were measured with low and high frequency IPV settings using an active lung simulator with long and short time constants.
Methods: An Avea ventilator was set to VC, f 15 breaths/min, VT 500 mL, flow 60 L/min, PT 0.50 s, PEEP 0 cm H2O, flow trigger 2.0 L/min, and FIO2 0.21. Then connected to an ASL 5000 as a passive lung (compliance of 20 mL/cm H2O or 50 mL/cm H2O with resistance set at 5 cm H2O/L/s). After baseline measures were obtained IPV was added to the system at low and high frequency settings. Six trials with low compliance, 3 of which had low frequency IPV and 3 with high frequency IPV. The same procedure was repeated with a high compliance. Driving pressure was approximately 27 psig and was applied for 2 min. Measurements of Ppeak, Ppause, and auto-PEEP were collected at steady state.
Results: Pressure and volume data ± IPV at low and high frequency are shown in Figures A and B. VT increased the most in conditions of high compliance. Ppeak and Ppause increased the most in conditions of low compliance. The altering of IPV frequency did not affect these pressures significantly. Altering IPV frequency increased auto-PEEP in both conditions of low and high compliance with a greater effect in the latter.
Conclusions: The addition of IPV to a conventional ventilator increases Ppeak, Ppause, and levels of auto-PEEP in a model with varying compliance. In a patient with varying lung units of compliance and resistance the modality should be applied with caution. The observation that auto-PEEP develops with IPV warrants future studies to evaluate patient-ventilator trigger dyssynchrony when IPV is superimposed on conventional ventilation.
1. Dellamonica J, Louis B, Lyazidi A, et al. Intensive Care Med 2008;34:2035-2043. 2. Riffard G, Buzenet J, Guerin C. Respir Care 2014;59(7):1116-1122.
Figure A) Average tidal volume changes under varying conditions. LC = Low compliance; HC = High compliance; HF = high frequency IPV; LF = low frequency IPV. Figure B) Average pressure changes under varying conditions. Ppeak = peak pressure; Ppause = plateau pressure; and autoPEEP. Data are mean +/- standard deviation (n=3).
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