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Interchangeability between two breath-by-breath O2 uptake calculation algorithms in asthmatic and healthy volunteers

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Abstract

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 O2 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’O2) 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’O2 values and IR was calculated accordingly.

Results

CVs were significantly greater in the asthmatic volunteers (F = 5.97, p < 0.05), being lower for IND compared to EXP (F > 7.04, p < 0.02). CVs decreased as a function of the reciprocal of the square root of the average V’O2. 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’O2 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.

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Abbreviations

ANOVA:

Analysis of variance

BMI:

Body mass index

CV:

Coefficient of variation

EXP:

“Expiration-only” approach, i.e., the breath-by-breath gas-exchange algorithm that uses information obtained during expiration and the Haldane transformation (Ward 2018)

FEV1 :

Forced expiratory volume in the first second

FeF25-75:

Forced expiratory flow between 25 and 75% of vital capacity

FVC:

Forced vital capacity

IND:

“Independent breath” approach, i.e., the breath-by-breath alveolar gas-exchange algorithm that uses information obtained during both inspiration and expiration (Cettolo and Francescato 2018)

IR:

Interchangeability rate

\(\dot{\mathrm{V}}{\mathrm{O}}_{2}\) :

Oxygen uptake value (generic)

\(\dot{\mathrm{V}}{\mathrm{O}}_{2}^{\mathrm{I}\mathrm{N}\mathrm{D}}\;\text {and}\; \dot{\mathrm{V}}{\mathrm{O}}_{2}^{\mathrm{E}\mathrm{X}\mathrm{P}}\) :

Oxygen uptake calculated applying the “Independent breath” and the “Expiration-only” approaches, respectively; all the data are expressed in STPD conditions

SD:

Standard deviation

STPD:

Standard temperature pressure dry

tn−1(0.975):

0.975th Quantile of a Student’s t distribution with n − 1 degrees of freedom, where n is the number of data

References

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Acknowledgements

We thank Cortex GmbH (Liepzig, Germany) for having provided us with the metabolic unit. Cortex GmbH was not involved in the study design, data collection, analysis, or interpretation. This experimentation was conducted with the unconditioned support of the ALPI Association (Association for the Pediatric Allergies and Pneumopaties), Udine (Italy).

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Authors and Affiliations

  1. Department of Medicine, University of Udine, P.le Kolbe 4, 33100, Udine, Italy

    Maria Pia Francescato & Valentina Cettolo

  2. Allergology and Pulmonology Clinic and Laboratory, ALPI Association, Udine, Italy

    Mario Canciani

Authors
  1. Maria Pia Francescato
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  2. Mario Canciani
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  3. Valentina Cettolo
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Contributions

MPF, MC, and VC contributed in conception and design of the experiments; VC and MPF performed the experiments, analyzed the data and wrote the paper. All the authors read and approved the final version of the manuscript.

Corresponding author

Correspondence to Maria Pia Francescato.

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None of the authors has conflicts of interest to declare.

Additional information

Communicated by Guido Ferretti.

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Francescato, M.P., Canciani, M. & Cettolo, V. Interchangeability between two breath-by-breath O2 uptake calculation algorithms in asthmatic and healthy volunteers. Eur J Appl Physiol 120, 1417–1428 (2020). https://doi.org/10.1007/s00421-020-04374-w

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  • DOI: https://doi.org/10.1007/s00421-020-04374-w

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