2006 OPEN FORUM Abstracts
Effect of Altitude on Peak Inspiratory Pressure and tidal volume during Pressure-Targeted A/C using the LTV 1000 and HT 50
Denise Y. Chase, Susan Marmentini, Lonny
Background: During pressure-targeted A/C, the peak inspiratory pressure (PIP) should remain constant. The PIP and tidal volume (VT) at various altitudes were evaluated using the Pulmonetics LTV 1000 and the Newport HT 50.
Method: The testing altitudes were 2938, 5600 and 8890 feet. Each ventilator was connected to the Hans Rudolph Electronic Breathing Simulator (HR 1101). HR 1101 settings: Resistance (Raw) 5, 15 and 25 cm H2O/L/sec; Compliance (Cst) 20, 40, 60 and 80 mL/cm H2O. LTV 1000 and HT 50 settings: Pressure-Targeted A/C; Rate 8/minute; Pressure 25 cm H2O; PEEP 5 cm H2O; TI 1.0 second. PIP and VT were the average of five breaths as the altitude, compliance and resistance were changed. Recorded values were: LTV 1000 displayed values (LTV), HR 1101 measured values with the LTV 1000 (HR-LTV), HT 50 displayed values (HT), and HR 1101 measured values with the HT 50 (HR-HT).
Results: Peak inspiratory pressure with a Cst of 40 mL/cm H2O and Raw of 15 cm H2O/L/sec: at 2938 ft LTV 25.0 cm H2O, HR-LTV 24.9 cm H2O, HT 28.0 cm H2O and HR-HT 26.8 cm H2O; at 5600 ft LTV 26.8 cm H2O, HR-LTV 26.4 cm H2O, HT 28.4 cm H2O and HR-HT 26.7 cm H2O; at 8890 ft LTV 27.0 cm H2O, HR- LTV 27.0 cm H2O, HT 29 cm H2O and HR-HT 26.2 cm H2O.
Tidal volume with a Cst of 40 mL/cm H2O and Raw of 15 cm H2O/L/sec: at 2938 ft LTV 621 mL, HR-LTV 655 mL, HT 669 mL and HR-HT 581 mL; at 5600 ft LTV 592 mL, HR-LTV 652 mL, HT 661 mL and HR-HT 579 mL; at 8890 ft LTV 557 mL, HR-LTV 662 mL, HT 654 mL and HR-HT 599 mL. There was a similar trend as compliance and resistance were changed at each altitude.
Conclusion: The change in altitude had little effect on PIP as compliance and resistance were changed. PIP should remain constant, but should still be monitored while ventilating patients in pressure-targeted ventilation. Tidal volume is affected by altitude with some ventilators at different compliance and resistance, while ventilating in pressure-targeted A/C.