Assessment of Respiratory System Resistance during High-Frequency Oscillatory Ventilation Based on In Vitro Experiment

Jan Matejka,Martin Rozanek,Jakub Rafl

doi:10.3390/app112311279

Abstract

High-frequency oscillatory ventilation (HFOV) is a type of mechanical ventilation with a protective potential characterized by a small tidal volume. Unfortunately, HFOV has limited monitoring of ventilation parameters and mechanical parameters of the respiratory system, which makes it difficult to adjust the continuous distension pressure (CDP) according to the individual patient’s airway status. Airway resistance Raw is one of the important parameters describing the mechanics of the respiratory system. The aim of the presented study was to verify in vitro whether the resistance of the respiratory system Rrs can be reliably determined during HFOV to evaluate Raw in pediatric and adult patients. An experiment was performed with a 3100B high-frequency oscillator, a physical model of the respiratory system, and a pressure and flow measurement system. The physical model with different combinations of resistance and compliance was ventilated during the experiment. The resistance Rrs was calculated from the impedance of the physical model, which was determined from the spectral density of the pressure at airway opening and the spectral cross-density of the gas flow and pressure at airway opening. Rrs of the model increased with an added resistor and did not change significantly with a change in compliance. The method is feasible for monitoring respiratory system resistance during HFOV and has the potential to optimize CDP settings during HFOV in clinical practice.

Highlights

High-frequency oscillatory ventilation (HFOV) is one of the unconventional methods of mechanical lung ventilation
Attenuation of pressure amplitude along the bronchial tree may contribute to less mechanical stress on lung tissue during HFOV compared with conventional mechanical ventilation (CMV) [2]
It has been shown that other monitoring and computational methods, including electrical impedance tomography (EIT) [9], optoelectronic plethysmography [10], or impedance analysis of the respiratory system [11], can lead to optimization of HFOV settings

Summary

Introduction

High-frequency oscillatory ventilation (HFOV) is one of the unconventional methods of mechanical lung ventilation. It is characterized by a small tidal volume, approaching an anatomical dead space, with a protective potential [1]. The patients with severe acute respiratory distress syndrome (ARDS) that do not tolerate CMV may be the target group for HFOV [3] if an alternative rescue therapy to ECMO is considered. Continuous distension pressure (CDP) and a set fraction of inspired oxygen determine the oxygenation of the ventilated subject in HFOV. There have been studies that emphasize the need for an individualized approach in setting the ventilation parameters of HFOV [7,8]. The results of previous studies conducted with HFOV may have been influenced by settings that were not sufficiently individualized to the needs of individual patients [12,13]

Methods

Findings

Discussion

Conclusion