The Science Journal of the American Association for Respiratory Care

2011 OPEN FORUM Abstracts


Jeffrey W. Wright, Stephen Burton, Kevin Crezee; Respiratory Care, Primary Childrens Medical Center, Salt Lake City, UT

This study is to determine liter flows needed to attain the prescribed NitricOxide (NO) parts per million (ppm) to the lower airway using a Heated Humidified Nasal Cannula (HHNC). Study variables: Multiple inspiratory times (Ti), Tidal Volumes (Vt), Respiratory Rates (RR), and liter per minute (lpm) flows. Lung model: The lung model was a lexan plastic box with a silastic test lung placed inside the box to simulate thoracic motion. The the box volume was 165cc with multiple ports for gas sampling/return, and for mounting the model's nose. The nose consisted various adaptors and tygon tubing. To turn the model into a breathing device it was attached to a Drager Evita XL in Airway Pressure Release Ventilation (APRV) mode. In APRV, the pressure release time became the Ti, and the P high was the expiratory phase in our lung model. The communication tube between the Drager and lung had a screw clamp to regulate flows. The Study: A Fisher Paykel (FP) humidifier, FP HHNC, and INO Max DS were used in this study. The circuit was assembled and warmed to 37 C. The INO Max DS calibrated, and then set at a delivered dose of 20 ppm and analyzed. The sample line was attached to the lung model. The HHNC was placed on the lung model nose, 2 to 3 minutes would pass to allow lung gasses to reached a steady state before recording data. Parameter changes started with HHNC flows being increased in increments of 1 lpm starting at 2 lpm and ending at 6 lpm. After all lpm changes were complete, the flow would be decreased back to 2 lpm and the RR would be increased by about 10. The flow rates were again increased as described. Once the RR was 60 and HHNC was at 6 lpm, the Ti would be increased, RR decreased back to 30, HHNC flow rate back to 2 lpm. The process would start over.(see tables 1, 2, and 3) When Ti or Vt were changed the screw clamp was adjusted to ensure flow throughout the Ti. Results: It was found that RR made little change in the delivered NO. The lower flow rates showed the biggest decrease in the delivered NO ppm. Ti, Vt, and HHNC flows were the factors that made the greatest effect. A Vt of 15cc with 2 lpm showed a 25% reductions in the analyzed NO within the lung model. As the Vt decreased, so did the difference between set NO and delivered NO. Conclusion: Where Ti and Vt are variables that can't be controlled higher flow rates with the HHNC are going to be needed to deliver the prescribed dose of NO to a patient's lower airways. Sponsored Research - None