A ventilator generating a positive or negative internal compliance.
This paper describes technical details of a ventilator for altering the resistive and elastic load placed on respiratory muscles during spontaneous breathing in intubated infants. Positive or negative values for ventilator resistance and/or ventilator compliance can be chosen by superimposing the weighted sum of the flow and/or the volume signal over the input to a pressure controller within the pressure feedback control system of the ventilator. The aim of the study was to compare values of the ventilator's compliance (Cv), as measured with a ventilation mechanics calculator, with those Cv values set by the ventilator's Cv control knob on the front panel. Another aim was to compare measured values of total compliance of a combined ventilator-lung model system (Ct) with the values expected according to theory where 1/Ct = 1/Cv + 1/C1m (Eq. alpha; C1m is the lung model's compliance). The Cv values set on the front panel were nearly identical to those measured (Cvm = 0.97 * Cvs + 0.54) over the whole tested range from -20 to +20 ml/kPa. Similarly, the measured Ct values were almost equal to those expected according to Eq. alpha; the standard deviation of the relative residuals was 2.7% for elastic loading and 12.4% for elastic unloading. We conclude that the ventilator described in this study can effectively provide both elastic loading and elastic unloading of spontaneous breathing, as expected according to theory.
Schaller
P
P
Dresden Medical Academy, Institute of Biomedical Engineering, Germany.
Schulze
A
A
D001698:Biomedical Engineering; D004548:Elasticity; D006801:Humans; D007231:Infant, Newborn; D008170:Lung Compliance / Q000502:physiology*; D008954:Models, Biological; D015656:Respiratory Mechanics / Q000502:physiology; D012132:Respiratory Muscles / Q000502:physiology; D012122:Ventilators, Mechanical