Fig. 2

Cardiovascular panels.

Panel 1: O₂ uptake (VO₂) and CO₂ output (VCO₂) vs. time plus relationship of peak VO₂ and work rate (WR). B, beginning and E, end of exercise. Peak \({\dot{\text{V}}\text{O}}_{2}\) indicates peak exercise capacity and oxygen uptake at the end of an incremental exercise test. Validity is dependent on patient effort. It is an index of long-term survival. Increase ΔV̇O₂/ΔWR: provides information about the contribution of aerobic metabolism to exercise (aerobic capacity). A low ratio indicates impaired O₂ delivery and high anaerobic metabolism during exercise (e.g., peripheral artery, cardiovascular, pulmonary vascular and/or lung disease). Panel [3] refers to the original 9-panel display [26]. 

Analysis (target values and response kinetics): Peak \({\dot{\text{V}}\text{O}}_{2}\) within normal limits or reduced (indicates impaired O₂ transport and/or utilisation)? Early flattening, reduction or plateau of peak V̇O₂? Overshoot in \({\dot{\text{V}}\text{O}}_{2}\) following termination of exercise (short-term increase in stroke volume [SV] with reduced afterload; e.g., cardiovascular disease)? Post-exercise \({\dot{\text{V}}\text{O}}_{2}\) recovery to baseline delayed (indicates high O₂ deficit during exercise)? Δ\({\dot{\text{V}}\text{O}}_{2}\)-peak/ΔWR during exercise: normal, increased (e.g., obesity) or flattening/downsloping? Oscillatory patterns at rest/moderate exercise (indicates left chronic heart failure [CHF] with poor prognosis)?

Panel 2: Relationship of heart rate and oxygen pulse vs. time. O₂ pulse (\({\dot{\text{V}}\text{O}}_{2}\)/HR) indicates the amount of oxygen extracted by the tissues per heartbeat. This provides information about SV and cardiac output (SV × C(a-\(\overline{\upsilon }\)) O₂) during exercise. Heart rate (HR) is the factor that normally limits exercise capacity in healthy subjects.

Analysis (target values and response kinetics): O₂ pulse at peak exercise: normal or reduced (impaired transport of O₂ and/or O₂ utilisation, e.g., cardiovascular disease, anaemia, peripheral arterial disease [PAD], myopathy) or elevated (chronotropic incompetence, e.g. beta-blocker therapy, heart failure, atrial flutter, tachycardia)? Plateau formation of O₂ pulse (below predicted value)? Linear or flat increase of O₂ pulse during early, middle or late exercise? Post-exercise O₂ pulse recovery to baseline delayed (suggests large O₂ deficit during exercise)? Increase in HR vs. \({\dot{\text{V}}\text{O}}_{2}\) normal, steep or low (suggests chronotropic incompetence)? HR: elevated at rest? Alternating course of HR during exercise (indicates arrhythmia)? HR reserve (maximal HR predicted—peak HR at peak \({\dot{\text{V}}\text{O}}_{2}\)): normal, high or low?

Panel 3: Relationships of CO₂ output (\({\dot{{\mathbf{V}}}\mathbf{CO}}_{2}\)) (y-axis) and O₂ uptake (\({\dot{{\mathbf{V}}}\mathbf{O}}_{2}\) (x-axis) and the relationship between HR and \({\dot{{\mathbf{V}}}\mathbf{O}}_{2}\). First reference to determine AT (see main text). AT corresponds to the curve point at which, due to CO₂-related hyperventilation, \({\dot{\text{V}}\text{CO}}_{2}\) begins to continuously rise more steeply than the \({\dot{\text{V}}\text{O}}_{2}\) (V-slope method). The V-slope is less responsive to breathing irregularities than P_ETO₂ and \({\dot{\text{V}}\text{E}}/{\dot{\text{V}}\text{O}}_{2}\). HR: more detailed information on HR behaviour (incl. target value range) See also HR at Panel 2.

Analysis (target values and response kinetics): AT in target range or reduced (indicates impaired O₂ delivery)? Cross-check with panels 4, 7 (3-panel view). Linear increase in HR relative to \({\dot{\text{V}}\text{O}}_{2}\)? HR reserve: normal, low or increased?