2006 OPEN FORUM Abstracts
IMPACT OF VARIOUS O2 DEVICES AND FLOWRATES ON THE PERCENT OXYGEN MEASURED IN EXPIRED ERV GAS
Langenderfer, MEd, RRT-NPS, Asst.
Prof and DCE Northern Kentucky Univ. Highland Heights, KY.
Background: Evaluating oxygen therapy techniques is problematic because of difficulties in measuring the real FiO2 achieved. Gas sampling via pharyngeal catheter disrupts normal ventilation and fails to measure the actual % oxygen within the lung. In an attempt to evaluate various oxygen devices and flowrates, we tried a new approach. We measured the O2% in the ERV, the last portion of gas exhaled with effort, after multiple subjects breathed oxygen for 7+ minutes from various devices and flowrates. We then calculated the FiO2 using the (modified) alveolar gas equation.
Methods: Fifteen volunteers each breathed oxygen for 7+ minutes from various devices/flowrates. After tidal exhalation, ERV gas was collected, and the % oxygen measured with a calibrated VacuMed lab O2 analyzer. To calculate FiO2 and to assure normal breathing, PETCO2 was measured.
Results: On room air the average expired ERV was 17 % oxygen. (N=15)
|Device: Flow:||NC 2 lpm Close Os||NC 2 lpm Open Os||28%Venti at 6 lpm||NC 6 lpm Close Os||NC 6 lpm Open Os|
|N; range||11; 19-23||11; 18-23||6; 21-24%||12; 28-36||10; 24-38|
|Device: Flow:||Standard NC 10 l.||HighFlow NC 10 l.||HighFlow NC 14 l.||NRB 15 l. SafeVent||NRB 15 l. No Vent|
|N; Range||17; 30-51||10; 31-47||12; 32-53||12; 48-62||9; 48-65|
|Device: Flow:||SmplMsk 10 lmp||Oxymizer 1 lpm||Oxymizer 6 lpm||PlseDose = 2 lpm||PlseDose = 6 lpm|
|N; Range||6; 33-40||6; 21-23||6; 29-37||8; 19-24||11; 24-35|
Conclusions: Percent O2 in ERV gas is a useful
tool to evaluate oxygen therapy devices and flowrates. Open-mouth breathing lowers FiO2 slightly.
NC flows above 6 lpm do increase ERV O2%,
but with less increase at flows above 10 lpm. Equivalent ERV O2 % is achieved by
NC 2 lpm, 28% venturi, 1 lpm
Oxymizer and Salter PulseDose
set = to 2 lpm.
Salter PulseDose = 6 lpm
gives lower FiO2 than cannula at 6 lpm.
NRB at 15 lpm only gives 62-65% O2, with
the higher FiO2 when using all 3 flap valves.