The Science Journal of the American Association for Respiratory Care

2005 OPEN FORUM Abstracts

EVALUATION OF 6 AND 12-FOOT CIRCUIT LENGTHS ON DELIVERED VOLUME AND PEAK PRESSURE DURING CPAP/PSV ON THE LTV 1000

Dan Neifert, Matthew Seitz, Lonny Ashworth MEd RRT, Boise State University, Boise, ID.

Background: The purpose of this study was to determine how 6-foot and 12-foot adult circuit lengths affect the delivered volume and peak pressure during CPAP and PSV, using the LTV 1000 for patients desiring longer circuits to provide more mobility.

Method: The LTV 1000 was connected to the Hans Rudolph Breathing Simulator (HR1101). HR1101 settings: Resistance (RAW) 10, 15, 20 and 25 cm H2O/L/sec; Compliance (CST) 20, 40 and 60 mL/cm H2O; rate 10/min. LTV 1000 settings: CPAP 5 cm H2O, PSV 10 cm H2O. A minimum of five breaths was recorded at each setting as compliance and resistance were changed, with the 6-foot circuit and the 12-foot circuit.

Results: At CST 20: increasing Raw from 10-25, the 6-foot circuit had PIP of 17, 14, 13 and 12 cm H2O and VT of 409, 309, 263 and 226 mL; the 12-foot circuit had PIP of 18, 15, 14 and 13 cm H2O and VT of 415, 314, 266 and 235 mL. At CST 40: increasing Raw from 10-25, the 6-foot circuit had PIP of 15, 13, 11 and 12 cm H2O and VT of 656, 495, 362 and 282 mL; the 12-foot circuit had PIP of 16, 14, 13 and 13 cm H2O and VT of 641, 454, 398 and 351 mL. At CST 60: increasing Raw from 10-25, the 6-foot circuit had PIP of 15, 13, 12 and 12 cm H2O and VT of 786, 638, 592 and 515 mL; the 12-foot circuit had PIP of 16, 14, 13 and 13 cm H2O and VT of 754, 559, 465 and 399 mL.

Conclusion: During CPAP with Pressure Support Ventilation, at a higher compliance, even though PIP remains fairly constant, the delivered volume with the 12-foot circuit is greater than the 6-foot circuit as resistance increases.

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