Energy is needed to perform the work required while exercising. This energy is supplied via cellular metabolism. In simple terms, the food that we eat supplies us with the necessary substrate for energy production. During this process, energy is ‘trapped’ in molecules of adenosine triphosphate (ATP).

There are many different potential causes of exercise limitation and there can be overlap between disease processes. We suggest applying the approach to interpretation outlined in Table 8.1 and Figure 8.7, explore what constitutes a ‘normal’ test, and how parameters may vary in different clinical scenarios.

A typical CPET for a patient with cardiovascular disease is shown in Figures 22.1 and 22.2 and Table 22.1 and described in ‘Test Review and Interpretation’.

Spirometry literally means ‘measuring of breath’, and as an investigation it reflects the lung’s bellows function and can be used to determine the extent of respiratory disease.

To understand basic spirometry, we need to describe how the total space within the lungs is divided into volumes and capacities. A volume is a specific measurement of either inspired or expired gas (or in the case of tidal volume both), whereas a capacity is combination of two or more volumes.

All 9-panel plots contain a graph of VO2 versus work rate (some also include a VCO2 plot on the same graph for a better overall appreciation of exercise capacity).

In this part, we explore the ways of presenting data as 9-panel plots and the importance, meaning, and variations of each individual plot.

The Fick principle (first described by Adolf Eugen Fick in 1870) is one of the key physiological concepts that underpins cardiopulmonary exercise testing. In his work, Fick described the use of oxygen as a ‘marker substance’ that could be used to measure the cardiac output of a dog’s heart.

Dysfunctional Breathing

A typical for a patient with pulmonary vascular limitation is shown in Figures 24.1 and 24.2 and Table 24.2.

This plot examines the end-tidal partial pressures of O2 and CO2 (the plot may also include arterial partial pressures if invasive monitoring is also used).

Cardiopulmonary exercise testing is usually performed using either a treadmill or a cycle ergometer; each has their benefits and limitations (outlined in Table 6.1). Most institutions use a cycle ergometer for CPET – although semi-recumbent ergometers can also be used and it is also possible to use a hand crank for patients with limited leg mobility. It is worth noting that CPET values reported in research papers in peri-operative medicines tend to have been derived from cycle ergometers.

This plot examines the relationship between tidal volume (Vt) and minute ventilation (VE).

Minute ventilation (VE) is the sum of the volumes of each breath over the course of a minute.

A typical CPET for a patient with peripheral vascular limitation is shown in Figures 25.1 and 25.2 and Table 25.1.

The variables that a cardiopulmonary exercise test aims to measure can be presented in a number of different ways. The standard method of presenting these data is as a 9-panel plot. Different 9-panel plots are available; which arrange individual plots in different orientations.