| Abstrakt: |
Objective. Inhaled nitric oxide (NO) can be delivered continuouslyor sequentially (= during inspiration) at different locations of theventilation circuit. We have tested the influence of locations, modes of NOadministration and the ratio of the inspiratory time over the respiratorycycle time (I/I + E ratio) on the accuracy of NO fractions, delivered by 2devices: Opti-NO and Flowmeter. Methods.We used a simplified lungmodel consisting of a ventilation circuit with a Y piece, a tracheal tube, a150 ml dead-space volume and a 5 liter balloon. Three fractions (3, 6, 9 ppm)were administered continuously or sequentially, in controlled volume, in 4different sites on the inspiratory branch above the Y piece:i) justafter the water trap, ii) just before the Y piece; below the Y piece:iii) just after the Y piece, iv) into the endotracheal tube. In addition,different I/I + E ratios (25, 33, 50, 80%) were studied. The delivered NOfractions were measured in the balloon by chemiluminescence (CLD 700,Ecophysics). A linear regression analysis was used to test the relationshipbetween administered and measured NO fractions for the 3 fractions (3, 6 and9 ppm) in sequential and continuous modes. Intercept values were compared tozero and slopes to the identity line. Results.When NO was administeredin the continuous mode upstream the Y piece, NO fractions measured in theballoon corresponded to the administered fractions. In contrast, below the Ypiece, the measured NO fractions were significantly lower than theadministered NO fractions. In the sequential mode, above and below the Ypiece, the delivered NO fractions were within the manufacturer's range.Conclusions.For the continuous NO delivery, locations above the Ypiece are mandatory. However, locations below the Y piece imposes a sequentialsystem, which can also be used for the sites located above the Y piece. |
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