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The following is a summary of “Modes of administration of nitric oxide devices and ventilators flow-by impact the delivery of pre-determined concentrations,” published in the August 2024 issue of Critical Care by Vuillermoz et al.
Inhaled nitric oxide (iNO) is mainly used with patients in intensive care units (ICU) for refractory hypoxemia in patients under ventilation. The device’s primary purpose is to guarantee an accurate inspiratory NO concentration, with (NO2) concentrations lower than 0.3 ppm.
Researchers conducted a retrospective study to assess the accuracy of 7 different iNO devices with different ICU ventilators to reach inspiratory NO concentration targets and evaluate their potential toxicity risk.
They tested 7 iNO-devices on a test lung connected with ICU ventilators at 4 different levels of flow-by. The flow and the airway pressure were measured in the inspiratory limb of the patient circuit. The nitric oxide/nitrogen (NO/N2) flow was measured on the administration line of the iNO-devices along with an electrochemical analyzer was used to measure in the test-lung.
The results showed 3 iNO-device generations based on the way they deliver NO flow: “Continuous,” “Sequential to inspiratory phase” (I-Sequential), and “Proportional to inspiratory and expiratory ventilator flow” (Proportional). Median accuracy of iNO concentration measured in the test lung was 2% (interquartile range, IQR -19; 36), -23% (IQR -29; -17), and 0% (IQR -2; 0) with Continuous, I-Sequential, and Proportional devices, respectively. Increased ventilator flow decreased concentration in the test lung with Continuous and I-sequential devices. (NO2) formation was measured to assess potential risks of toxicity not exceeding the safety target of 0.5 ppm. However, (NO2) concentrations higher than or equal to 0.3 ppm can cause bronchoconstriction, which was observed in 19% of the different configurations.
They concluded 3 different iNO devices were associated with highly variable iNO concentrations’ accuracy. The ventilator’s flow demonstrated a significant impact on iNO concentration, and the accuracy of delivering iNO was only permitted by the proportional devices.
Source: annalsofintensivecare.springeropen.com/articles/10.1186/s13613-024-01351-w
