The Science Journal of the American Association for Respiratory Care

2007 OPEN FORUM Abstracts

THE EFFECTS OF FLOW, FREQUENCY, AND PRESSURE SETTINGS ON THE DELIVERED LEVELS OF NITRIC OXIDE AND NITRIC DIOXIDE DURING MANUAL VENTILATION WITH THE T-PIECE RESUSCITATOR

J. T. Gallagher1, T. R. Myers1, K. M. Deakins1


Background Infants treated with inhaled nitric oxide (NO) in the neonatal intensive care unit (NICU) often require periodic manual ventilation which is provided by the manual delivery system module on the INOvent Delivery System (INO Therapeutics, Clinton, NJ). INO Therapeutics recommends using a self-inflating or hyperinflation bag set at 15 Lpm to achieve NO concentrations of 20 ppm + 8 ppm when manually ventilating with this delivery system. The T-piece resuscitator, frequently utilized in the NICU, is pneumatically powered with a flow meter to provide consistent pressures during episodes of manual ventilation and typically requires 8 Lpm of gas flow to achieve its desired settings. The purpose of this study was to determine if varying flow rates, frequencies or pressures would change the NO concentration or nitric dioxide (N02) level when using the t-piece resuscitator in conjunction with the INOvent.

Methods
The manual delivery system of the INOvent was used to pneumatically drive the Neopuff Infant Resuscitator (Fisher/Paykel, Auckland, NZ) in this bench test simulation. A Neopuff circuit was connected to a 3.0 mm endotracheal tube attached to a test lung (Infrasonics) with a fixed compliance. A sample port and tubing were connected to a calibrated INOvent to measure NO and N02 values. A pressure adapter and tubing were connected to a Breath Tracker 1705 electronic manometer (Core-M, L.P.) to accurately measure pressures and frequencies. Simulated manual ventilation scenarios were established to cover a broad range of pressures and frequencies for this bench test. Flow rates of 8, 10, 12, and 15 Lpm were utilized to achieve pressures of (PIP/PEEP in cm H20) 15/5, 20/5, 25/5 and respiratory frequencies of 20, 30, 40 breaths/minute. Values were recorded for each combination of variables after 60 seconds.

Results NO and N02 values are presented in the following table for each set of flows, pressures and frequencies. Changes in measured NO concentrations were consistent with changes in flow rate, and not frequency or pressure. The level of measured NO delivered proportionally increases as flow rate increases; as is true with other resuscitation devices.

Conclusion
Using a t-piece resuscitator with flows of 10-15 Lpm, measured NO is consistent with the manufacturer’s specifications. Based on this bench test, a flow rate of 15 Lpm appears optimal. Changes to current practice with t-piece resuscitators may be necessary to achieve the desired level of NO.

Measured Values of Nitric Oxide / Nitric Dioxide
PIP /PEEP
(cmH2O)
Frequency Flow Rates (L/min)
8 101215
15/5 20 11/0.5 12/0.5 15/0.4 17/0.7
15/5 30 10/0.5 12/0.5 14/0.4 16/0.8
15/5 40 10/0.5 12/0.6 16/0.4 15/1.1
20/5 20 10/0.5 13/0.4 15/0.3 17/0.7
20/5 30 10/0.5 13/0.4 15/0.4 17/0.7
20/5 40 10/0.5 13/0.5 16/0.4 17/0.7
25/5 20 10/0.4 13/0.4 15/0.5 17/0.6
25/5 30 12/0.5 13/0.4 15/0.4 18/0.6
25/5 40 10/0.4 13/0.4 16/0.4 18/0.7



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