Douglas N; Melbourne, Australia.Altamimi H; Wang A; Basto J; Smith R; Taylor HE;
Internal medicine journal [Intern Med J] 2021 May 24. Date of Electronic Publication: 2021 May 24.
Background: One metabolic equivalent (MET) is equal to resting oxygen consumption. The average value for one MET in humans is widely quoted as 3.5ml/kg/min. However this value was derived from a single male participant at the end of the nineteenth century and has become canonical. Several small studies have identified varied estimates of one MET from widely varying populations. The ability of a patient to complete 4 METS (or 14mls/kg/min) is considered an indicator of their fitness to proceed to surgery.
Aims: The study aimed to define a typical value of one MET from a real-world patient population, as well as determine factors that influenced the value.
Methods: A database of cardiopulmonary exercise tests (CPET) tests was interrogated to find total of 1847 adult patients who had undergone CPET testing in the previous 10 years. From this database, estimates of oxygen consumption (VO 2 ) at rest and at the anaerobic threshold and a number of other variables were obtained. The influence of age, body mass index (BMI), sex and the use of beta blockers was tested.
Results: The median resting VO 2 at rest was 3.6ml/kg/min (IQR 3.0-4.2). Neither sex nor age greater than 65 years nor the use of beta blockers produced a significant difference in resting VO 2 , while those with a BMI greater than 25 had a significantly lower VO 2 at rest (3.4ml/kg/min vs 4.0ml/kg/min, p <0.001).
Conclusions: The estimate of 3.6ml/kg/min for resting VO 2 presented here is consistent with the previous literature, despite this being the first large study of its kind. This estimate can be safely used for pre-operative risk stratification.