title: Determination of respiratory point compensation in healthy adults: Can non-invasive near-infrared spectroscopy help?
abstract: OBJECTIVE
  We tested the hypothesis that the respiratory compensation point can be accurately determined in healthy participants during incremental cycling exercise using non-invasive near-infrared spectroscopy-derived measures of deoxygenated hemoglobin (deoxyHb).
  
  
  METHODS
  Validation study.
  
  
  METHODS
  118 healthy men (average age 47 ± 19 yrs, range 20-79 yrs) performed an incremental cycling test to exhaustion. Breath-by-breath pulmonary oxygen uptake (VO2) and other ventilatory and gas exchange variables were measured and used to determine respiratory compensation point. Vastus lateralis deoxyHb was monitored using a frequency domain multi-distance system near-infrared spectroscopy device and deoxyHb data were modeled with a piece-wise double-linear function from which the deoxyHb deflection point (deoxyHbDP) was determined. The absolute (L min(-1)) and relative (% maximal VO2 [VO 2max]) VO2 values associated with the respiratory compensation point and deoxyHbDP were determined for each individual.
  
  
  RESULTS
  DeoxyHb increased as a function of exercise intensity up to a point (deoxyHbDP) after which the signal displayed a "near-plateau". The deoxyHbDP corresponded to a VO2 of 2.25 ± 0.69 L min(-1) (74 ± 12% VO 2max) which was not significantly different from the VO2 at respiratory compensation point (2.28 ± 0.70 L min(-1) and 74 ± 10% VO 2max, p < 0.05). Both indices were highly correlated (r(2) = 0.86) and Bland Altman analyses confirmed a non-significant bias for VO2 (-0.024 L min(-1)) concomitant with a small imprecision of 0.26 L min(-1).
  
  
  CONCLUSIONS
  During incremental cycling exercise, the VO2 associated with the onset of a plateau in near-infrared spectroscopy-derived deoxyHb occurs in coincidence with the VO2 at respiratory compensation point suggesting that respiratory compensation point can be accurately estimated, non-invasively, using near-infrared spectroscopy-derived deoxyHb in alternative to the use of ventilatory-based techniques.
authors.affiliation: Department of Neurological and Movement Sciences, University of Verona, Italy.
authors.forename: Federico Y
authors.initials: FY
authors.lastname: Fontana
authors.affiliation: Canadian Center for Activity and Aging, School of Kinesiology, University of Western Ontario, Canada.
authors.forename: Daniel A
authors.initials: DA
authors.lastname: Keir
authors.affiliation: Department of Neurological and Movement Sciences, University of Verona, Italy.
authors.forename: Cecilia
authors.initials: C
authors.lastname: Bellotti
authors.affiliation: Department of Neurological and Movement Sciences, University of Verona, Italy; Faculty of Physical Activity and Sport, University of Flores, Argentina.
authors.forename: Gabriela F
authors.initials: GF
authors.lastname: De Roia
authors.affiliation: Canadian Center for Activity and Aging, School of Kinesiology, University of Western Ontario, Canada; Faculty of Kinesiology, University of Calgary, Canada.
authors.forename: Juan M
authors.initials: JM
authors.lastname: Murias
authors.affiliation: Department of Neurological and Movement Sciences, University of Verona, Italy. Electronic address: silvia.pogliaghi@univr.it.
authors.forename: Silvia
authors.initials: S
authors.lastname: Pogliaghi
mesh_terms: D000328:Adult; D000368:Aged; D015308:Anaerobic Threshold / Q000502:physiology*; D001642:Bicycling / Q000502:physiology*; D005080:Exercise Test; D064368:Healthy Volunteers; D006801:Humans; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000502:physiology; D010101:Oxygen Consumption; D019265:Spectroscopy, Near-Infrared
keywords: Anaerobic metabolism; Exercise prescription; Functional evaluation; Non-invasive techniques