The Science Journal of the American Association for Respiratory Care

2005 OPEN FORUM Abstracts

THE EFFECT OF VARIOUS HELIOX MIXTURES ON PEAK EXPIRATORY FLOWS (PEF).



Sorenson HM MA RRT; Vines DL MHS RRT, Ditsch K BS RRT, and Peters JI MD. The University of Texas Health Science Center at San Antonio, San Antonio, TX.

BACKGROUND:
Little is known about the effect of heliox on expiratory peak flow. To determine if benefits exist, we compared PEF with various heliox mixtures and air at airway resistances of 5, 20 and 40 cmH2O/L/sec during pressure support ventilation (PSV) in a spontaneously breathing lung model.

METHODS: One lung of a two compartment lung model was driven by a Puritan Bennett 7200 ventilator (Tyco International, Pleasanton CA.) to simulate spontaneous breathing. Patient efforts were simulated using varying tidal volumes (300, 400, 500, 600 mL) and peak flows (40, 60, and 80 L/min). PEF, exhaled tidal volume (VEXH) and peak inspiratory pressure (PIP) were measured using a Ventraks 1550 Respiratory Mechanics monitoring system (Novametrix Medical Systems, Inc., Wallingford, CT). Various tidal volumes and inspiratory flows were combined with the following lung conditions: normal resistance (5cmH2O/L/sec), increased resistance (20 cm H2O/L/sec) and severe resistance (40 cm H2O/L/sec). Each of the lung conditions received assistance from PSV at 5, 10, 15, and 20 cm H20. Measurements were made using the following gas sources; 80/20 heliox, 70/30 heliox, 60/40 heliox, air through the Aptaer delivery system (GE Healthcare, Madison, Wisconsin), and air on the SERVOi (Maquet Inc., Bridgewater, NJ). The heliox was provided using the Aptaer Heliox delivery system. The respiratory mechanics monitor was set for the various gas concentrations. All equipment was calibrated and checked for leaks before use.

RESULTS: The following table contains the mean PEF for the various gas mixtures. There were no significant differences in mean VEXH or mean PIP.

Gas Source Airway Resistance 5 cmH2O/L/sec Airway Resistance 20 cmH2O/L/sec Airway Resistance 40 cmH2O/L/sec
  Mean PEF (L/min) Mean PEF (L/min) Mean PEF (L/min)
80/20 Heliox 69 + 20 a 55 + 12 a, b, c, d 46 + 9 a, b, c, d
70/30 Heliox 63 + 17 a 50 + 10 a, b, c 41 + 8 a, b, c
60/40 Heliox 61 + 15 a 46 + 9 a, b 36 + 8 a, b
Air Aptaer 44 + 9 33 + 6 27 + 4
Air Servo i 68 + 16 a 42 + 7 a 31 + 5 a
  1. Significantly greater than Air Aptaer (p< .05)
  2. Significantly greater than Air Servo i (p< .05)
  3. Significantly greater than 60/40 Heliox (p< .05)
  4. Significantly greater than 70/30 Heliox (p< .05)

CONCLUSION: Heliox may allow patients to achieve higher PEF during ventilation with the Aptaer Heliox delivery system. Higher PEF may promote alveolar emptying and result in less air trapping.

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