Accession Number : ADA131331

Title :   Efficiency of High-Frequency Ventilation as Determined by Nitrogen Washouts: A Model Study.

Descriptive Note : Medical research progress rept. (Final),


Personal Author(s) : Clarke,J R ; Homer,L D ; Flynn,E T

PDF Url : ADA131331

Report Date : Apr 1983

Pagination or Media Count : 26

Abstract : We examined the frequency dependency of high-frequency ventilation (HFV) by using a two-compartment mechanical model. A loudspeaker was used as an oscillator to assist mixing between the two compartments. One compartment (C1) contained either O2 or SF6 prior to mixing, while the other (C2) contained air. The rate of change of nitrogen concentration in the latter compartment was used as an index of mixing efficiency. The speaker was driven with either a sinusoidal or random signal, and the spectral characteristics and acoustic power of the pressures generated in each compartment were determined by a Fast Fourier Transform Analyzer and PDP 11/34 and /70 computers. Transport coefficients describing mixing increased approximately linearly with power. For a given power in C1, the mixing rates were highly frequency-dependent. The frequencies for resonance and optimal mixing were essentially identical, and decreased as gas density increased. When powers were matched in C2, however, mixing was much less dependent on frequency. Random noise proved as effective in augmenting mixing as sinusoidal excitation. It can do so while decreasing the magnitude of pressure changes in the system and while reducing the influence of changing resonant frequencies. (Author)

Descriptors :   *Laboratory equipment, *Ventilation, *Respiration, High frequency, Lung, Efficiency, Nitrogen, Determination, Models, Measurement, Rates, Indexes, Transport properties, Coefficients, Analyzers, Fast fourier transforms, Oscillators, Mixing, Gases

Subject Categories : Stress Physiology
      Test Facilities, Equipment and Methods

Distribution Statement : APPROVED FOR PUBLIC RELEASE