Interpretation of CPET

ByDr. Samiaa Hamdy Sadek

Assiut University

Interpretation of Cardio-Pulmonary Exercise Testing (CPET)

Maximal exercise testing

This is the highest attainable oxygen consumption

achieved during an incremental exercise test

VO2 is defined by the Fick equation:

VO2 = CO* C (a – v)O2

where CO is cardiac output and C (a – v)O2 is the

arterio-venous O2 content difference.

O2 pulse = VO2/HR

ml O2 consumed per beat

taken to reflect stroke volume

assuming PaO2 and C(a-v)O2 respond

normally

O2 pulse < 80% predicted is abnormal

Pco2 of respired gas, determined at the end of an

exhalation.

This is commonly the highest Pco2 measured during the

alveolar phase of the exhalation.

It is expressed in units of millimeters of mercury (or

kilopascals).

Normal resting end tidal CO2 ranges between 36 – 44

mmHg, approximating arterial PaCO2.

With exercise end tidal CO2 should increase 3 -8

mmHg from rest to AT and then slightly decline at

maximal exercise secondary to the anaerobically

induced increase in VE (minute ventilation).

Po2 of respired gas, determined at the end

of an exhalation.

End tidal O2 normaly at rest 90mmHg or greater and

increases with exercise 10-30 mmHg for exercise

above the anaerobic threshold because of metabolic

acidosis induced hyperventilation and rising R

(respiratory exchange ratio) at maximal exercise.

the ratio of VE at peak exercise to the estimated maximal voluntary ventilation (MVV) represents the assessment of the ventilatory limitation or of the prevailing ventilatory constraints. Ventilatory limitation is judged to occur when VE /MVV exceeds 85%.

In lung diseases, the increase in VE /MVV may reflect either the reduction in ventilatory capacity (reduction in MVV), the increase in ventilatory demand (increase in VE ), or both.

Achievement of age-predicted maximal HR during exercise is often used as a reflecion of maximal or near maximal effort and presumably signals the

achievement of VO2max.

The difference between the age maximal HR and the maximal HR achieved during exercise is referred to as the HR reserve (HRR). Normally, at maximal exercise, there is little or no HRR.

Anaerobic threshold

VE/VO2VE/VO2

VE/VCO250 -

0 -

ATRC AT RC

Normal Obstructive Restrictive/PVD(Efficiency of ventilation)

Normal values at AT: VE/VO2: 25 (22-27) VE/VCO2: 28 (26-30)

Ventilatory Equivalents