94 Working rate of oxygen consumption
The working rate of oxygen consumption (%) describes how intensively the body uses oxygen compared with its expected level. It depends on how well arterial blood is oxygenated, on the ability of haemoglobin to bind oxygen in the lungs and release it in the tissues, and on the metabolic rate of the tissues. Thyroid hormones have the strongest influence: thyroxine (T4), converted to triiodothyronine (T3), increases the number and activity of mitochondria, and part of the energy from oxidation is released as heat rather than stored in ATP. As a result, oxygen consumption per kilogram rises in hyperthyroidism and falls in hypothyroidism.
What changes the working rate
Lower rate
Hypothyroidism, hypothermia, sedation and anaesthesia, starvation, reduced oxygen delivery with tissue hypoxia, anaemia, haemoglobin that binds oxygen too tightly (carbon monoxide).
Higher rate
Hyperthyroidism, fever, infection and sepsis, burns and trauma, physical activity, shivering, stimulants, increased work of breathing.
Unexplained weight change, persistent fatigue, palpitations, intolerance of heat or cold, or tremor should be checked with thyroid function tests (TSH, free T4).
References
- Ross DS, Burch HB, Cooper DS, et al. 2016 American Thyroid Association guidelines for diagnosis and management of hyperthyroidism and other causes of thyrotoxicosis. Thyroid. 2016;26(10):1343–1421. doi:10.1089/thy.2016.0229
- Dunn JO, Mythen MG, Grocott MP. Physiology of oxygen transport. BJA Educ. 2016;16(10):341–348.
This article is for general information and does not replace a consultation with a doctor. Measurements must be interpreted by a physician together with symptoms and other tests.
Published on 2 May 2024