It is often presumed that high frequency ventilation (HFV) with low tidal volumes (smaller than anatomic dead space) produces lower alveolar pressures than conventional mechanical ventilation, thus reducing the attendant risks of barotrauma and diminished cardiac output. However, in a preliminary modeling study, we found that this presumption is not always valid. We propose a series of experiments on dogs to test the model prediction and to further our understanding of the interaction between gas transport and lung mechanics during HFV. We will determine the optimal combination of HFV parameters that would simultaneously maximize gas exchange and minimize alveolar pressures. The parameters in question are frequency, tidal volume, airflow waveform and lung volume. We will investigate how respiratory optimization is affected under certain simulated disease conditions. We will also compare the effects of applying HFV by external chest oscillation with the more common mode of HFV application via the trachea. From our measurements of gas transport, local airway transport resistances and lung mechanical characteristics, we will develop a mathematical model that incorporates both the gas exchange and lung mechanics aspects of HFV, including important nonlinearities such as gas trapping. This model will be used to generate clinically significant predictions of how respiratory function may best be optimized in human adults and infants with pulmonary disease.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Unknown (R23)
Project #
5R23HL033976-03
Application #
3448839
Study Section
Respiratory and Applied Physiology Study Section (RAP)
Project Start
1985-09-01
Project End
1989-05-31
Budget Start
1987-09-01
Budget End
1989-05-31
Support Year
3
Fiscal Year
1987
Total Cost
Indirect Cost
Name
University of Southern California
Department
Type
DUNS #
041544081
City
Los Angeles
State
CA
Country
United States
Zip Code
90033
Khoo, M C; Ye, T H; Tran, N H (1989) Lung pressures and gas transport during high-frequency airway and chest wall oscillation. J Appl Physiol 67:985-92
Khoo, M C; Yamashiro, S M; Yamashiro, P (1989) Minimization of lung pressure swings during high-frequency ventilation: a model. J Appl Physiol 67:993-1000
Khoo, M C; Gelmont, D; Howell, S et al. (1989) Effects of high-frequency chest wall oscillation on respiratory control in humans. Am Rev Respir Dis 139:1223-30