title: Cardiorespiratory optimal point: a submaximal variable of the cardiopulmonary exercise testing.
abstract: BACKGROUND
  At the maximal Cardiopulmonary Exercise Testing (CPET), several ventilatory variables are analyzed, including the ventilatory equivalent for oxygen (VE/VO2). The minimum VE/VO2 value reflects the best integration between the respiratory and cardiovascular systems and may be called "Cardiorespiratory Optimal Point (COP)".
  
  
  OBJECTIVE
  To determine the behavior of the COP according to gender and age in healthy adults and verify its association with other CPET variables.
  
  
  METHODS
  Of 2,237 individuals, 624 were selected (62% men and 48 ± 12 years), non- athletes, healthy, who were submitted to maximal CPET. COP or minimum VE/VO2 was obtained from the analysis of ventilation and oxygen consumption in every minute of CPET. We investigated the association between age and COP for both genders, as well as associations with: VO(2)max, VO(2) at anaerobic threshold (VO(2)AT), oxygen uptake efficiency slope (OUES) and with maximum VE. We also compared the intensity of exertion (MET) at the COP, AT and VO(2)max.
  
  
  RESULTS
  COP increases with age, being 23.2 ± 4.48 and 25.0 ± 5.14, respectively, in men and women = (p < 0.001). There are moderate and inverse associations with VO(2)max (r = -0.47; p < 0.001), with VO(2)AT (r = -0.42; p < 0.001) and with OUES (r = -0.34; p < 0.001). COP occurred, on average, at 44% do VO(2)max and before AT (67% of VO(2)max) (p < 0.001).
  
  
  CONCLUSIONS
  COP, a submaximal variable, increases with age and is slightly higher in women. Being modestly associated with other ventilation measures, there seems to be an independent contribution to the interpretation of the cardiorespiratory response to CPET.
authors.affiliation: Faculdade de Ciências Médicas e da Saúde de Juiz de Fora - SUPREMA, MG, Brazil.
authors.forename: Plínio Santos
authors.initials: PS
authors.lastname: Ramos
authors.forename: Djalma Rabelo
authors.initials: DR
authors.lastname: Ricardo
authors.forename: Claudio Gil Soares de
authors.initials: CG
authors.lastname: Araújo
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D005080:Exercise Test / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010101:Oxygen Consumption / Q000502:physiology*; D012123:Pulmonary Ventilation / Q000502:physiology*; D012016:Reference Values; D012189:Retrospective Studies; D012737:Sex Factors; D013147:Spirometry; D018709:Statistics, Nonparametric; D013997:Time Factors; D014692:Ventilation-Perfusion Ratio / Q000502:physiology*; D055815:Young Adult