Physiological noise versus white noise to drive a variable ventilator in a porcine model of lung injury

Abstract

This study demonstrates that the nature of the variability files, chosen to drive the variable ventilator, had no effect on indices of gas exchange or respiratory mechanics in this model. A considerable overlap of the multifractal files existed. The potential to drive a variable ventilator using algorithm-derived files with multifractal characteristics, thereby eliminating the requirement to use physiologically-derived signals, is discussed.

Variable rate ventilation strategies for the injured lung

“…As a result, the current value of the measured parameter is influenced not only by recent events, but also by those occurring in the "distant" past. Such longrange correlations are viewed as a type of memory that may be useful in predicting the future behaviour of the respiratory system, and valuable in providing clues to the underlying dynamics governing the respiratory generator and its feedback controllers.In the current study, Froehlich et al 5 used two types of computer-generated files to control the mechanical ventilation of pigs subjected to acute lung injury by the intravenous infusion of oleic acid. one of the files was physiologically-derived from the spontaneous breathing pattern of a healthy human at rest.…”

“…In the current study, Froehlich et al 5 used two types of computer-generated files to control the mechanical ventilation of pigs subjected to acute lung injury by the intravenous infusion of oleic acid. one of the files was physiologically-derived from the spontaneous breathing pattern of a healthy human at rest.…”

“…It has been suggested 4 that the variability of peak airway pressure recruits collapsed alveoli, thereby leading to an increase in Pao 2 . In this issue of the Journal, Froehlich et al 5 have gone one step further by asking whether the temporal order of the fluctuations in breathing rate and volume, as well as the fluctuations themselves, account for the beneficial effects of variable mechanical ventilation. The question arises from the fact that fluctuations in respiratory period and tidal volume, characterizing spontaneous breathing in healthy humans and other species, are time-scale invariant [6][7][8] rather than random in occurrence.…”

“…For the moment, however, efforts to optimize the beneficial effects of variable mechanical ventilation should be focused as much on changing the distribution of data points comprising the computer-generated file used to drive the mechanical ventilator, as on changing the fractal exponents characterizing their temporal order of occurrence. 5 vont un peu plus loin en se demandant si l'ordre temporel des fluctuations dans le débit et le volume respiratoires, outre les fluctuations en soi, sont responsables des effets bénéfiques de la ventilation mécanique variable. la question provient du fait que les fluctuations de période respiratoire et de volume courant, qui caractérisent la respiration spontanée chez les humains et les autres espèces en bonne santé, surviennent de façon invariante plutôt qu'aléatoire à l'échelle du temps.…”

“…5 ont utilisé deux types de fichiers créés par ordinateur pour contrôler la ventilation mécanique chez des cochons soumis à une lésion pulmonaire aiguë par perfusion intraveineuse d'acide oléique. Un des fichiers se voulait physiologique et était dérivé du schéma de respiration spontanée d'un être humain sain au repos.…”