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. 2008 Dec;34(12):2291-9.
doi: 10.1007/s00134-008-1301-7. Epub 2008 Sep 30.

Ability of dynamic airway pressure curve profile and elastance for positive end-expiratory pressure titration

Alysson R Carvalho  1 , Peter M Spieth, Paolo Pelosi, Marcos F Vidal Melo, Thea Koch, Frederico C Jandre, Antonio Giannella-Neto, Marcelo Gama de Abreu
Affiliations

Ability of dynamic airway pressure curve profile and elastance for positive end-expiratory pressure titration

Alysson R Carvalho et al. Intensive Care Med. 2008 Dec.

Abstract

Objective: To evaluate the ability of three indices derived from the airway pressure curve for titrating positive end-expiratory pressure (PEEP) to minimize mechanical stress while improving lung aeration assessed by computed tomography (CT).

Design: Prospective, experimental study.

Setting: University research facilities.

Subjects: Twelve pigs.

Interventions: Animals were anesthetized and mechanically ventilated with tidal volume of 7 ml kg(-1). In non-injured lungs (n = 6), PEEP was set at 16 cmH(2)O and stepwise decreased until zero. Acute lung injury was then induced either with oleic acid (n = 6) or surfactant depletion (n = 6). A recruitment maneuver was performed, the PEEP set at 26 cmH(2)O and decreased stepwise until zero. CT scans were obtained at end-expiratory and end-inspiratory pauses. The elastance of the respiratory system (Ers), the stress index and the percentage of volume-dependent elastance (%E (2)) were estimated.

Measurements and main results: In non-injured and injured lungs, the PEEP at which Ers was lowest (8-4 and 16-12 cmH(2)O, respectively) corresponded to the best compromise between recruitment/hyperinflation. In non-injured lungs, stress index and %E (2) correlated with tidal recruitment and hyperinflation. In injured lungs, stress index and %E (2) suggested overdistension at all PEEP levels, whereas the CT scans evidenced tidal recruitment and hyperinflation simultaneously.

Conclusion: During ventilation with low tidal volumes, Ers seems to be useful for guiding PEEP titration in non-injured and injured lungs, while stress index and %E (2) are useful in non-injured lungs only. Our results suggest that Ers can be superior to the stress index and %E (2) to guide PEEP titration in focal loss of lung aeration.

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Figures

Fig. 1
Fig. 1
Relationship between values of stress index and %E2 and amount of tidal hyperinflation (left column) and tidal recruitment (right column) measured at all levels of positive end-expiratory pressure (PEEP) in non-injured animals
Fig. 2
Fig. 2
Distribution of aeration as a function of PEEP in non-injured (left panels), oleic acid (midpanels) and lavage (right panels) injured animals. a Regions of interest in the CT scan images obtained in a representative animal at each PEEP level: red hyperinflation, blue normal aeration, light gray poor aeration, dark gray non-aeration. Note the focal loss of aeration in dependent lung regions at lower PEEP and the hyperinflation of non-dependent regions throughout inspiration; b–d elastance of the respiratory system, %E2 and stress index. Open and filled symbols represent individual and median values, respectively; e median fractions of hyperinflation (FHyper, open red squares) and recruitment (FRec, open black circles) at end-expiration, i.e., induced by PEEP. Red and black dots represent individual values of fractional hyperinflation and recruitment, respectively; f median tidal hyperinflation (Tidal Hyper, filled red squares) and recruitment (Tidal Rec, filled black circles) (ml). Red and black dots represent individual values of hyperinflation and recruitment, respectively
See this image and copyright information in PMC

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