These results indicated that RR, PEEP and plateau pressure minus PEEP all had significant effects on the magnitude of ΔPaO2, but that RR and PEEP were much more significant predictor values. As with previous studies ( Folgering et al., 1978, Purves, 1965 and Purves, 1966), this work was conducted on the flat part of the dissociation curve (the rabbits

inspired 100% oxygen), where small changes in arterial oxygen content (or saturation) would lead to relatively large changes in PaO2PaO2. In agreement with conclusions previously reported in the literature ( Williams et al., 2000), this study concluded that the Etoposide large PaO2PaO2 oscillations suggested significant cyclic recruitment of atelectasis in the animal surfactant depletion model. The need for very fast oxygen and saturation sensors became clearer when ΔPaO2 appeared to be MDV3100 chemical structure linked

to RR in studies of ARDS animal models (Baumgardner et al., 2002, Folgering et al., 1978, Hartmann et al., 2012, Shi et al., 2011 and Syring et al., 2007). Taken together, RR was varied between 6 bpm and 30 bpm in these animal studies, where RRs greater than 20 bpm were generally associated with reduced PaO2PaO2 oscillation amplitude (from ∼26 to 2.6 kPa [∼200–20 mmHg]), especially when no or low PEEP was applied. This decrease in the amplitude of PaO2PaO2 oscillations was attributed to the effect of high RRs on maintaining lung recruitment, yet it appeared unclear whether this result Pregnenolone was a physiological phenomenon or, possibly, a failure of the AL300 sensor to respond fast enough to catch the true magnitude of the physiological oscillations at high RRs. In fact, it was calculated that the AL300 sensor would detect only about 80% of the actual PaO2PaO2 oscillation at RR of 24 bpm, and thus presumably smaller proportions at higher RRs (Costa

and Amato, 2007); this inaccuracy in the PaO2PaO2 measurements is acceptable in terms of maintenance of end-expiratory recruitment up to RRs of about 20 bpm (Baumgardner and Syring, 2007). Fig. 1, Fig. 2 and Fig. 3 confirm the AL300 sensor’s incapacity to measure large PO2PO2 oscillations at elevated RR in vitro   (on the test rig), where no effect can be attributed to lung recruitment. The question of whether or not the diminutions in the recorded rabbit ΔPaO2 with increasing RR are due to physiology or diminution in sensor performance (or a mixture of both) still remains unresolved, and the physiological implications for the AL300′s limited accuracy at RR of ∼30 bpm or greater are unclear. However, it seems clear that the fastest possible PaO2PaO2 sensor should be used to provide more reliable information at any RR, including high RRs between 30 bpm and 60 bpm. This would then afford the opportunity to extend the use of this sensing technology to neonatal intensive care units and small animal studies.