Nitric oxide delivery by neonatal noninvasive respiratory support devices

Inhaled nitric oxide (INO) has been used with heated and humidified high-flow nasal cannula (HFNC), nasal CPAP and several forms of noninvasive ventilation (NIV). This study was designed to evaluate the delivered dose of INO, level of NO2 generation, and effect of net gas delivery (addition of INO to the ventilator circuit--gas removed for sampling) on lung pressure at different NO doses during noninvasive respiratory support.

An infant lung model was supported with the different noninvasive modes during INO therapy. NO and NO2 were measured from within the patient circuit of the noninvasive devices and simulated neonatal trachea at several NO levels. Lung pressures were compared with and without INO and at several INO settings.

Accuracy of NO delivery was determined to be within the stated accuracy by the manufacturer with nasal CPAP and NIV, but accuracy was compromised during HFNC. INO and NO2 measured by the INOmax DSIR (Ikaria, Hampton, New Jersey) did not consistently reflect the delivered dose of NO or formation of NO2 across all types of neonatal noninvasive respiratory support. Tracheal NO2 levels were <1.5 ppm with all forms of noninvasive support, except nasal intermittent mandatory ventilation at 40 ppm INO. Lung model mean airway pressures were mildly affected by gas sampling/delivery during combined INO therapy/HFNC at certain flows but remained stable with all other forms of noninvasive support.

Clinicians cannot always assume that the set INO level results in a similar lung dose when using all forms of neonatal noninvasive support. Clinical decisions regarding ways to improve INO delivery may need to include changing settings or placing patients on a different form of noninvasive support. The NO2 level delivered to the patient could be greater than the value recorded by the INO delivery system.