Interchangeability between two breath-by-breath O-2 uptake calculation algorithms in asthmatic and healthy volunteers

摘要

Introduction The interchangeability analysis has been recently proposed to objectively assess whether a newly developed measurement tool can substitute the older ones; this analysis assumes that the measures yielded by the compared tools should differ less than a maximum acceptable value. We aimed to assess the interchangeability rate (IR) of the breath-by-breath O-2 uptake data calculated with the "Independent breath" (IND) and the "Expiration-only" (EXP) algorithms. Methods Oxygen, carbon dioxide fractions, and ventilatory flow were recorded continuously over 26 min in 18 asthmatic and 20 well-matched healthy volunteers at rest, during cycling, and recovery; oxygen uptake (V'O-2) was calculated with the two algorithms under comparison. Coefficients of variation (CVs) of all the steady-state condition were modeled as a function of the average V'O-2 values and IR was calculated accordingly. Results CVs were significantly greater in the asthmatic volunteers (F = 5.97, p 7.04, p < 0.02). CVs decreased as a function of the reciprocal of the square root of the average V'O-2. The IR, calculated on the basis of this relationship, was not significantly different in the two groups of volunteers (F = 0.77, p = 0.385); taking as reference method the IND, or EXP algorithms, the IR values were significantly different (F = 58.6, p < 0.001), amounting to 97.4 +/- 2.2% or to 98.2 +/- 1.7%, respectively. Conclusion The relative noise of V'O-2 was greater in the asthmatic volunteers compared to the healthy ones and was lower for IND compared to EXP. The interchangeability analysis suggested that IND might be a better substitute for EXP than the opposite.