Measurement of tidal volume using a pneumotachometer during high-frequency oscillation

High-frequency oscillatory ventilation: What large-animal studies have taught us!

“…A tidal volume of 4.4 ± 1.2 mL/kg was delivered at an I:E of 1:1, delta pressure of 60 cm H 2 O, and rate of 4 Hz. These findings were similar to those observed in other smaller animal models (30)(31)(32). It is interesting to speculate that at the capability of current adult oscillators with delta pressures of 90 cm H 2 O and rates of 3 Hz, tidal volumes of ≥6 mL/kg would be delivered during HFO in this 30-kg lavage injury sheep model.…”

Four methods of measuring tidal volume during high-frequency oscillatory ventilation

“…These techniques have included whole body plethysmography (animal studies) (12,30,31), jacket plethysmography (32), impedance plethysmography (33), and differential pressure pneumotachometers (11)(12)(13)(14)30). However, none of these approaches are readily adaptable for use in the intensive care unit, and all are challenging to calibrate for use during HFOV.…”

“…Courtney et al (12) measured VTs in ten rabbits at a single frequency (10 Hz) at ⌬Ps of 20, 40, 60, 80, and 100 cm H 2 O using a heated Hans-Rudolph Ptach. They compared Ptach-measured VTs to those calculated from a whole body plethysmograph assuming adiabatic conditions (12).…”

“…They compared Ptach-measured VTs to those calculated from a whole body plethysmograph assuming adiabatic conditions (12). Although they observed a good correlation between the two measurements (R ϭ .92), the Ptach-measured VTs consistently overestimated those measured by the plethysmograph.…”

“…Traditional differential pressure pneumotachometers have been used for this purpose (11)(12)(13)(14) but are cumbersome. Many exhibit nonlinear behavior outside of a narrow range of flows.…”