Physiological measurement
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Physiological measurement · Jun 2005
Compliance and resistance levels and unloading in proportional assist ventilation.
During proportional assist ventilation (PAV), resistive and elastic unloading relieve the work of breathing. Excessive unloading, however, results in resonant oscillations and runaway pressures. Our aim was to determine the appropriate levels of unloading that could be applied to clinical practice. ⋯ When the level of unloading fully compensated for the model's compliance, peak inflating pressures greater than 40 cmH(2)O were delivered; peak pressure limits of 20 cmH(2)O, however, resulted in very short (0.2 s or less) inflation times. High peak pressures were not delivered if the level of elastic unloading used was limited to that which reduced the model's elastance to that of a 'normal lung'. In conclusion, these results suggest that when using PAV, it is important to assess the compliance and resistance of the infant and endotracheal tube, so that levels of unloading that fully compensate for the resistance and compliance levels can be avoided.
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Physiological measurement · Jun 2005
Inertance measurements by jet pulses in ventilated small lungs after perfluorochemical liquid (PFC) applications.
Perfluorochemical liquid (PFC) liquids or aerosols are used for assisted ventilation, drug delivery, lung cancer hyperthermia and pulmonary imaging. The aim of this study was to investigate the effect of PFC liquid on the inertance (I) of the respiratory system in newborn piglets using partial liquid ventilation (PLV) with different volumes of liquid. End-inspiratory (I(in)) and end-expiratory (I(ex)) inertance were measured in 15 ventilated newborn piglets (age < 12 h, mean weight 724 +/- 93 g) by brief flow pulses before and 80 min after PLV using a PFC volume (PF5080, 3 M) of 10 ml kg(-1) (N = 5) or 30 ml kg(-1) (N = 10). ⋯ Measurements of I by jet pulses in intubated small animals are reproducible. PFC increases the respiratory inertance, but the magnitude depends considerably on its spatial distribution which changes during the breathing cycle. Large differences between I(in) and I(ex) are an indicator for liquid in airways or the ETT.