The Science Journal of the American Association for Respiratory Care

2004 OPEN FORUM Abstracts

TIDAL VOLUME EVALUATION IN TWO HIGH-FREQUENCY OSCILLATORS FOR ADULT PATIENTS USING A MODEL LUNG WITH A POSITION SENSOR

Naoya Iguchi MD1, Yuji Fujino MD1, Osamu Hirao MD1, Takashi Mashimo MD1, Masaji Nishimura MD2 1Intensive Care Unit, Osaka University Hospital; 2Emergency and Critical Care Medicine, University of Tokushima Graduate School

INTRODUCTION: Until the recent introduction of the R100® (Metran, Saitama, Japan), the 3100B® (SensorMedics, Yorba Linda, CA) was the only high-frequency oscillator available for adult patients. Both of these oscillators create airway pressure swings by driving a diaphragm to and fro. It has been difficult to compare delivered tidal volume (VT) at a specific setting during HFOV although it is a very important aspect of oscillator performance.

METHODS: A model lung (TTL, Michigan Instruments, MI) was oscillated using the 3100B or R100. Settings for both oscillators were: frequency 5, 7, 9 Hz; mean airway pressure, 15 cmH2O; oxygen inspiratory fraction, 0.21; and inspiration:expiration (I:E) ratio, 1:1. At each setting, the oscillator pressure swing was set at maximum. Model lung compliance was set at 50 mL/cmH2O and an endotracheal tube of 8.0 mm internal diameter was used to provide resistance. During the trials, attached to the upper surface of the model lung and converting lung movement to analog electrical signals, a position sensor evaluated VT. Pressure and volume signals were recorded at a sampling rate of 667 Hz, digitized using an analog-to-digital converter, and recorded in a computer. At each setting, three waveforms were analyzed and the average value was used.

RESULTS: At 5 Hz, the R100 delivered more VT than the 3100B. As frequency increased the difference of delivered VT decreased (Figure).


CONCLUSION: Using a model lung with a position sensor, oscillator performance can be evaluated by measuring VTs.

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