REGIONAL DISTRIBUTION OF NITRIC OXIDE (NO) and NITRIC DIOXIDE (NO2) DURING INHALATIONAL THERAPY: EFFECT OF VENTILATION STRATEGY. † 2329

Optimal physiologic benefit of inhaled nitric oxide (INO) as a selective pulmonary vasodilator has been related to adequate delivery to its site of action. While various forms of ventilation are under investigation for INO delivery in the neonate, the effect of ventilation strategy on regional INO delivery and NO₂ has not been evaluated. To test the hypothesis that regional INO and NO₂ are dependent upon the mode of ventilation, neonatal lambs (1-7days) were anesthetized, paralyzed, instrumented (tracheal, distal airway, arterial, and venous cannulae), hyperventilated with F₁O₂ = 1 and INO (20,40,80 ppm) was administered during conventional mechanical ventilation (CMV: n=6) and randomization to high frequency oscillatory (HFOV; SensorMedics; n = 3) or high frequency jet ventilation (HFJV; Life Pulse; n = 3). NO and NO₂ was measured at the inspiratory limb (INSP) and distal airway (DISTAL) using electrochemical analysis (Pulmonox). The distribution profile of NO DISTAL and NO₂ DISTAL was assessed as a% of INSP NO and in ppm, respectively. The results(mean ± SE) demonstrate that the concentration of NO distally was less than 50% of the INO, independent of the INO and ventilatory strategy. In addition, distal NO was significantly higher with HFJV and CMV as compared to HFOV (##p < 0.05), independent of the INO. At INO ≥ 40 ppm, distal NO₂ was significantly lower (#p < 0.05) with both HFOV and HFJV as compared to CMV and was <1 ppm with all strategies. These data indicate that the distribution of INO is influenced by the ventilatory strategy; the relatively lower concentration of NO₂ distally during HFV may reflect improved lung volume recruitment and uptake of NO by the bronchopulmonary circulation. (Supp. ASRI, Bunnel Inc, SensorMedics, and NIH R29HD26341)Table

Table 1