title: A comparison of methods for determining the ventilatory threshold: implications for surgical risk stratification.
abstract: OBJECTIVE
  The ventilatory threshold (VT) is an objective physiological marker of the capacity of aerobic endurance that has good prognostic applications in preoperative settings. Nevertheless, determining the VT can be challenging due to physiological and methodological issues, especially in evaluating surgical risk. The purpose of the current study was to compare different methods of determining VT and to highlight the implications for assessing perioperative risk.
  
  
  METHODS
  Our study entailed analysis of 445 treadmill cardiopulmonary exercise tests from 140 presurgical candidates with an aortic abdominal aneurysm (≥3.0 to ≤5.0 cm) and a mean (standard deviation [SD]) age of 72 (8) yr. We used three methods to determine the VT in 328 comparable tests, namely, self-detected metabolic system (MS), experts' visual (V) readings, and software using a log-log transformation (LLT) of ventilation vs oxygen uptake. Differences and agreement between the three methods were assessed using analysis of variance (ANOVA), coefficient of variation (CV), typical error limits of agreement (LoA), and interclass correlation coefficients (ICC).
  
  
  RESULTS
  Overall, ANOVA revealed significant differences between the methods [MS = 14.1 (4.3) mLO2·kg-1·min-1; V = 14.6 (4.4) mLO2·kg-1·min-1; and LLT = 12.3 (3.3) mLO2·kg-1·min-1; P < 0.001]. The assessment of agreement between methods provided the following results: ICC = 0.85; 95% confidence interval (CI), 0.82 to 0.87; P < 0.001; typical error, 2.1-2.8 mLO2·kg-1·min-1; and, 95% LoA and CV ranged from 43 to 55% and 15.9 to 19.6%, respectively.
  
  
  CONCLUSIONS
  The results show clinically significant variations between the methods and underscore the challenges of determining VT for perioperative risk stratification. The findings highlight the importance of meticulous evaluation of VT for predicting surgical outcomes. Future studies should address the prognostic perioperative utility of computed mathematical models combined with an expert's review. This trial was registered at ClinicalTrials.gov, identifier: NCT00349947.
authors.affiliation: Division of Cardiology, Veterans Affairs Palo Alto Health Care System/Stanford University, 111C, 3801 Miranda Ave, Palo Alto, CA, 94304, USA. baruch.v1981@gmail.com.
authors.forename: Baruch
authors.initials: B
authors.lastname: Vainshelboim
authors.affiliation: Division of Cardiology, Veterans Affairs Palo Alto Health Care System/Stanford University, 111C, 3801 Miranda Ave, Palo Alto, CA, 94304, USA.
authors.forename: Shravan
authors.initials: S
authors.lastname: Rao
authors.affiliation: Division of Cardiology, Veterans Affairs Palo Alto Health Care System/Stanford University, 111C, 3801 Miranda Ave, Palo Alto, CA, 94304, USA.
authors.forename: Khin
authors.initials: K
authors.lastname: Chan
authors.affiliation: Division of Cardiology, Veterans Affairs Palo Alto Health Care System/Stanford University, 111C, 3801 Miranda Ave, Palo Alto, CA, 94304, USA.
authors.forename: Ricardo M
authors.initials: RM
authors.lastname: Lima
authors.affiliation: Stanford Center for Inherited Cardiovascular Disease, Stanford University, Stanford, CA, USA.
authors.forename: Euan A
authors.initials: EA
authors.lastname: Ashley
authors.affiliation: Division of Cardiology, Veterans Affairs Palo Alto Health Care System/Stanford University, 111C, 3801 Miranda Ave, Palo Alto, CA, 94304, USA.
authors.forename: Jonathan
authors.initials: J
authors.lastname: Myers
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D015308:Anaerobic Threshold / Q000502:physiology*; D017544:Aortic Aneurysm, Abdominal / Q000601:surgery; D005080:Exercise Test / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D008962:Models, Theoretical; D010101:Oxygen Consumption / Q000502:physiology*; D011300:Preoperative Care / Q000379:methods*; D011379:Prognosis; D018570:Risk Assessment / Q000379:methods