Procedure of the examination

During the examination, the test person usually performs physical work either on a bicycle ergometer or on a treadmill. However, there are also other devices, such as rowing or canoe ergometers, especially for spiroergometry with competitive athletes. The performance that is to be achieved is usually increased continuously, this is individually adapted to the performance of the respective test person.

The increase is either stepwise (step method) or continuous (ramp method). Meanwhile the test person wears a breathing mask, which measures on the one hand the breathing volumes and on the other hand the portion of oxygen (O2) and carbon dioxide (CO2) in the breathing air. In addition, an electrocardiogram (ECG) is taken via electrodes, which shows, among other things, the heart rate per minute.

Depending on the problem, blood pressure can also be measured. Lactate values and blood gases can also be measured. For this purpose, the test person’s blood is usually taken from the earlobe.

Measured values

During the examination the main focus is on the determination of respiratory gases. Respiratory frequency (AF), respiratory minute volume (AMV), carbon dioxide emission (VCO2) and oxygen uptake (VO2) are measured directly. From the above-mentioned variables, spiroergometry also calculates the respiratory quotient (RQ = VCO2/VO2) and the maximum oxygen uptake (VO2max).

Here the measured values mean the following:

The respiratory minute volume is the volume inhaled and exhaled per minute. At an average breathing frequency of 12 to 14/min and a respiratory volume of about 600 ml per breath, the respiratory minute volume of an adult is about 8000 ml.
Oxygen uptake is the amount of oxygen that the body extracts from the inhaled air per unit of time. It increases with increasing physical exertion, as the body needs more oxygen than at rest.
The maximum oxygen uptake (VO2max) describes the maximum amount of oxygen taken from the inhaled air per unit of time, i.e. it corresponds to the oxygen exhaustion under maximum load.With untrained persons it is 3-3.5 l/min, with trained persons it rises up to 5-6 l/min.
However, since this value depends heavily on the physical constitution, it is now usually given in relation to kilograms of body weight. The standard value for a young man is 44-50 ml/kg body weight. Top athletes reach values of up to 95 ml/kg body weight.
The respiratory quotient is calculated from carbon dioxide release divided by oxygen uptake, i.e. VCO2/VO2.
It can give information about the proportion of carbohydrate or fat burning. The RQ is 0.7 for pure fat burning and 1 for pure carbohydrate burning. At high intensity of exertion, CO2 exhalation exceeds the O2 intake, and the RQ rises to 1.1.

An RQ of 1.1 is thus a sign of exertion, i.e. the achievement of the maximum possible physical load.

Spiroergometry can also be used to determine the anaerobic threshold, also called lactate threshold. This is the point at which the body can no longer cover its energy requirements during performance by means of aerobic energy production alone, it must now also break down carbohydrates (sugars) without the addition of oxygen, which produces lactate. A performance above the anerobic threshold cannot be sustained for long, whereas a performance below the anerobic threshold allows a long endurance, for example in marathon runners.

The anaerobic threshold can be determined by taking a blood sample from the earlobe and measuring the lactate level. The anaerobic threshold is reached from a value of around 4 mmol/l, although this value can vary greatly from person to person. The lactate concentration at rest is usually 1-2 mmol/l.