The density of heliox (80% helium/20% oxygen) is less than ambient air (79% nitrogen/21% oxygen). This theoretically should reduce measured (but not actual) peak flow (PF) values when breathing heliox relative to air. The purpose of this investigation was to demonstrate this effect using a Mini Wright PF meter.
Twenty nonsmoking, nonobese volunteers without a history of asthma or any lung disease underwent PF testing. Three peak flows were obtained first breating air and then again after breathing heliox for two minutes using a nonrebreathing mask. After each heliox PF the subject did rebreathng with heliox for another two minutes before the next PF. The best of three efforts was used in data analysis for air and heliox. The results are expressed as mean + S.D.
There were 12 women and 8 men with an age of 47.8 + 8.6 years (range; 30–59). The average BMI was 24.5 + 3.0 (range; 18.9–29.3). The air and heliox peak flows were 511 + 115 and 470 + 136 liters/min, respectively (p < 0.01). This revealed a significant 8.1% average measured reduction in peak flow values breathing heliox in spite of the known increase in peak flows that should occur when breathing heliox.
The Mini Wright PF meter will not accurately measure peak flows when inhaling Heliox in normal volunteers.
Patient subjective clinical response, vital signs, and measurement of oxygenation are alternatives to replace actual PF values in determining clinical improvement if using heliox to treat obstructive airways disease.
Gene Pesola, No Financial Disclosure Information; No Product/Research Disclosure Information