2003 Abstracts

THE EFFECT OF TUBING LENGTH ON DELIVERED OXYGEN FLOW

Deborah Cullen EdD, RRT, FAARC, Joseph Koss, MS, RRT, FAARC, Katy Parker BS CRT, Natalie Lannan BS CRT, Respiratory Therapy Program, Indiana University, Indianapolis, Indiana.

Background: COPD patients have options for delivery of long term oxygen therapy in the home. Generally, patients may utilize several lengths of tubing anchored to a stationary device to perform activities of daily living. Excessive length in oxygen tubing may decrease the amount of flow delivered to the patient, leading to a variable F_IO₂. The purpose of this study was to discriminate at what lengths clinically relevant decreases in flow occur and whether statistically significant differences exist between the delivery systems at the given lengths of tubing.

Method: To ensure accurate delivery of flow and to titrate flow at 1-5 LPM, the RT 200 flow calibration device was utilized with 25-feet of tubing, as the control. Flow was measured using a calibration analyzer, series RT 200, then set. Flow was generated from an H-cylinder with a Thorpe tube flowmeter (at 1800 PSI) and an Invacare 5 concentrator. Tubing length was then increased in 25-foot intervals up to 200 feet connected via Salter swivel adapters (#1220) for flows ranging from 1-5 LPM to simulate a home oxygen situation. At each liter, actual flow output was recorded for each 25-feet of oxygen tubing added. The Paired t test was conducted via Minitab^TM

Results: There was a measurerable decrease in delivered flow when tubing length was greater than 100 feet and flow exceeded 3 LPM. At 3 LPM, the H-cylinder lost 25% of delivered flow and the concentrator lost 10% of flow, as measured by the RT 200. The H cylinder demonstrated a progressive loss of flow of approximately 5% with each 25-feet of tubing added, while the concentrator showed a loss of approximately 3% with each 25-foot addition. There was a statistically significant difference between the two systems at 50-200 feet (p< 0.006; Paired t-test).

Conclusion: The study demonstrated the relationship between tubing length and flow for two systems. The H-cylinder produced a greater loss in flow with increased tubing length than the Invacare concentrator. Tubing length greater than 100-feet at 3 LPM produced a clinically discernable loss in delivered flow. It may be beneficial for long term oxygen patients with excessive tubing lengths to utilize a concentrator for oxygen delivery.

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