Table 2.

Identification of abnormal reaction pattern(s)

Individual findings	Patient	Cardiovascular	Pulmonary vascular	Pulmonary	Lack of fitness
Reduced peak ${\dot{\text{V}}\text{O}}_2$		X	X	X	X
Low ${\dot{\text{V}}\text{O}}_2$ at AT		X	X	X	(X)
Steep HR increase relative to ${\dot{\text{V}}\text{O}}_2$ and shallow rise in O2 pulse, respectively		X	X		X
Low ${\dot{\text{V}}\text{O}}_2$/WR slope during incremental exercise		X	X
Elevated $\dot{\text{V}}\text{E}/{\dot{\text{V}}\text{CO}}_2$ slope or elevated EqCO2 at AT		*	X	X
Normal breathing reserve		X	X		X
ECG changes, inadequate BP behaviour		X
Low peak HR				X	X
Low PETCO2 or PaCO2 at rest and/or decrease during exercise		*	X
SpO2 or PaO2 decrease during exercise			X	(X)
Low breathing reserve				X
Abnormal breathing pattern**				X

Distinction between cardiovascular, pulmonary vascular and pulmonary reaction patterns or deconditioning as the primary cause(s) of exercise limitation (modified according to [1, 3, 7, 10, 20]). In the table, the findings that apply individually can be check-marked in the patient column. The identified pathophysiology can be used to establish the likely primary cause of the individual exercise limitation. Overlaps can occur between the categories (e.g., in chronic lung diseases with secondary effects on pulmonary vascular and myocardial function or in comorbid disease states). It should be noted that the severity of the underlying disorder has a major influence on the reaction patterns (e.g., normal peak ${\dot{\text{V}}\text{O}}_2$ in mild to moderate asthma). Exercise intolerance by claudications, pain or muscle fatigue etc. support the clinical suspicion of peripheral artery disease (PAD) or myopathies

a arterial, AT anaerobic threshold, BP blood pressure, CO₂ carbon dioxide, ECG electrocardiogram, Eq ventilatory equivalent, ET end-tidal, HR heart rate, O₂ oxygen, P pressure, SpO₂ oxygen saturation, $\dot{\text{V}}\text{E}/{\dot{\text{V}}\text{CO}}_2$ ventilatory equivalent for carbon dioxide, ${\dot{\text{V}}\text{O}}_2$ oxygen uptake, WR work rate

*Moderate to severe left ventricular failure. Patients with myocardial ischaemia without chronic heart failure, mild left ventricular failure, PAD, anaemia, deconditioning and poor effort alone demonstrate normal V/Q ratios and normal values for P_ETCO₂, PaCO₂

**Restrictive or obstructive breathing pattern, not including exercise oscillatory ventilation