Determination of the Respiratory Compensation Point by Detecting Changes in Intercostal Muscles Oxygenation by Using Near-Infrared Spectroscopy

Felipe Contreras-Briceño*, Maximiliano Espinosa-Ramirez, Vicente Keim-Bagnara, Matías Carreño-Román, Rafael Rodríguez-Villagra, Fernanda Villegas-Belmar, Ginés Viscor, Luigi Gabrielli, Marcelo E. Andía, Oscar F. Araneda, Daniel E. Hurtado

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

7 Scopus citations


This study aimed to evaluate if the changes in oxygen saturation levels at intercostal muscles (SmO2-m.intercostales) assessed by near-infrared spectroscopy (NIRS) using a wearable device could determine the respiratory compensation point (RCP) during exercise. Fifteen healthy competitive. triathletes (eight males; 29 ± 6 years; height 167.6 ± 25.6 cm; weight 69.2 ± 9.4 kg; VO2-máx 58.4 ± 8.1 mL·kg−1·min−1) were evaluated in a cycle ergometer during the maximal oxygen-uptake test (VO.2-máx), while lung ventilation (VE),. power output (watts, W) and SmO2-m.intercostales were measured. RCP was determined by visual method (RCPvisual: changes at ventilatory equivalents (VE·. VCO.−1. 2, VE·VO.−12) and end-tidal respiratory pressure (PetO2, PetCO2) and NIRS method (RCPNIRS: breakpoint of fall in SmO2-m.intercostales). During exercise, SmO2-m.intercostales decreased continuously showing a higher decrease when VE. increased abruptly. A good agreement between methods used to determine RCP was found (visual vs NIRS) at %VO... 2-máx, VO2, VE, and W (Bland-Altman test). Correlations were found to each parameters analyzed (r = 0.854; r = 0.865; r = 0.981; and r = 0,968; respectively. p < 0.001 in all variables, Pearson test), with no differences (p < 0.001 in all variables, Student’s t-test) between methods used (RCPvisual and RCPNIRS). We concluded that changes at SmO2-m.intercostales measured by NIRS could adequately determine RCP in triathletes.

Original languageEnglish
Article number444
Pages (from-to)444
Issue number3
StatePublished - Mar 2022

Bibliographical note

Funding Information:
Funding: This research was funded by PUENTE UC (VRI, Chile) to F.C.-B., III Concurso de Investi-gación & Innovación del Departamento Ciencias de la Salud (UC) to F.C.-B., and ANID-Millennium Science Initiative Program-ICN2021_004 to M.A.

Publisher Copyright:
© 2022 by the authors. Licensee MDPI, Basel, Switzerland.


  • exercise
  • near-infrared spectroscopy
  • oxygen uptake
  • respiratory compensation point
  • respiratory muscles


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