Background: Inhaled nitric oxide (iNO) is a commonly prescribed therapy for pediatric patients with pulmonary hypertension. At our pediatric institution (260-bed hospital, Level 1 Trauma, Level IV NICU), iNO is sampled on the dry side of the ventilator heater circuit for ventilated patients. On occasion, intrapulmonary percussion (IPV) therapy is necessary to improve airway clearance in patients receiving iNO. We hypothesize that the additional flow of the IPV would dilute the delivered iNO dose and aim to evaluate the effects of IPV on iNO delivery in a bench model. Methods: In an IRB-exempt bench study a simulated patient was ventilated on a Michigan Test Lung with a Servo-U (Getinge) ventilator set to pressure regulated volume control (PRVC) mode, FIO2 100%, VT 60 PS 10, PEEP of 5 with a Fisher & Paykel MR850 heater as a passover (not heated/humidified). Two INOMAX DSIR iNO delivery systems were utilized: one injecting and sampling on the dry side of the ventilator circuit and one at the patient y-piece for sampling purposes only, distal to the inflow of the IPV to the ventilator circuit (Figure 1). The iNO device was set to deliver 20 ppm throughout the treatment. The IPV (HillRom Metaneb) was connected to a 50 PSI oxygen source and was run for 10 min with 0.9 NSS in the nebulizer cup on CHFO mode with a high frequency. The IPV treatment was repeated thrice, and the sampled values were recorded every minute for the duration of the treatment (Table 1). Data were analyzed using a t-test to determine statistical significance. Results: Increased flow from the IPV decreased the total delivered iNO and sampled iNO at both locations in the ventilator circuit, measured in ppm (Figure 2). The difference between iNO sampled at the delivery site and the sampling site close to the patient was not statistically significant in any trial (P = .6, .06, and .26, respectively). However, the decrease from the 20 ppm to the sampled NO (averages- Sample 1 = 16.2, Sample 2 = 14.4) in both locations was statistically significant (P < .001). Conclusions: IPV treatment inline with the ventilator and iNO impacted iNO delivery and sampling in our bench model. Care should be considered for the change in delivered dose during these concurrent treatments. Further research must be done to understand accurately delivered doses when flow-driven adjunct therapies are required based on patient condition during iNO delivery.Figure 1 details the set-up of the bench study, from left to right: INO machine sampling at the patient wye, Michigan Test Lung, INO machine delivering 20ppm NO, Servo Ventilator, IPV device.Figure 2 details to minute by minute results of iNO from the bench study.
Ramsey et al. (Tue,) studied this question.