The Science Journal of the American Association for Respiratory Care

1996 OPEN FORUM Abstracts

NITRIC OXIDE DELIVERY WITH A NEONATAL HIGH FREQUENCY VENTILATOR

Robert Whiteside BS, RRT, Kirk Lunde RRT, Jonathan Klein MD, University of lowa Hospitals & Clinics, lowa City 1A, 52242

Background: Inhaled Nitric Oxide (NO) is a selective pulmonary vasodilator. Inhaled NO is administered by titrating source NO (800 ppm) in to the total gas flow of the ventilator circuit to obtain the prescribed dose (5-80 ppm). There are adverse effects of inhaling excessive NO, thus knowing the total circuit gas flow is essential in calculating the flow of the source NO. Most mechanical ventilators provide a constant or minute total gas flow value. However, the Infant Star (Infrasonics Inc., San Diego, CA) has a variable and non-displayed total gas flow during HFV. The HFV circuit total gas flow must be estimated. Method: In the high frequency ventilation (HFV) mode, the Infant Star ventilator varies the opening of 10 solenoid valves for a duration of 18 milliseconds to provide a total gas flow from 12 to 120 Lpm. An estimate of the total gas flow in HFV can be calculated: Est. Total Gas Flow = Freq. (BPM) x 0.018 sec. x Est. flow (Lpm) /60 sec. HFV flow is estimated by comparing the known range of HFV flows to the range of amplitudes measured on the Infant Star. The typical amplitude range using the Baxter ventilator circuit 1998-4H1 with the Fisher & Paykel water chamber MR220 is 11 to 51 cmH_{2}O. The total estimated gas flow is divided to match the range of amplitudes used during HFV. The total gas flow from the following chart using the measured amplitude and set frequency is then used to determine the flow of source NO. The NO is analyzed in the circuit. If the analyzed NO is not the dose prescribe than the total gas flow is recalculated by applying the analyzed NO value to this formula: Total Gas Flow (Lpm)=Set NO (Lpm) x 800 (ppm) / Analyzed NO (ppm). The new total gas flow is then used to determine the source NO flow and the circuit NO is re analyzed.

Amplitude

(cmH_{2}O) 4 Hz 6 Hz 8 Hz 10 Hz 12 Hz 15 Hz

11-15 1 2 2 3 4 5

16-19 1 2 2 3 4 5

20-23 2 3 4 5 6 8

24-27 3 5 6 8 10 12

28-31 4 6 8 10 12 15

32-35 5 7 10 12 14 18

36-39 6 8 11 14 17 21

40-43 6 10 13 16 19 24

44-47 7 11 14 18 22 27

48-51 8 13 17 21 25 31

52 or

greater 9 13 18 22 26 33

Results: This method of estimating the total gas flow and recalculating the total gas flow during HFV has been bench tested using a wide range of HFV settings. The NO analyzed in the circuit was found to be +/- 2 ppm. This method has since been used successfully on 3 patients. Conclusions: This method provides an estimated starting point for the titraton of NO during HFV with an Infant Star ventilator. The use of an estimated HFV total gas flow can prevent over-or underestimating the source NO flow titrated to the circuit at the initiation of inhaled NO therapy.

Reference: OF-96-136

You are here: RCJournal.com » Past OPEN FORUM Abstracts » 1996 Abstracts » NITRIC OXIDE DELIVERY WITH A NEONATAL HIGH FREQUENCY VENTILATOR