Pulse oximetry – measuring blood oxygen saturation and monitoring the pulse
Measuring blood oxygen levels and checking the heart rate (pulse) is standard practice in monitoring patients during illness and recovery, as well as healthy people. During examinations and exercise testing, and when improving sports performance or recreational activity, monitoring blood oxygen saturation together with the pulse and heart rhythm helps rehabilitation medicine to plan and adjust the recovery process optimally while improving safety. Together with arterial blood pressure measurement, spirometry, the electrocardiogram and 24-hour Holter ECG and blood pressure monitoring, pulse oximetry is becoming part of the work not only of cardiologists but also of physiatrists, occupational medicine specialists, family doctors and other specialties.
Heart activity and its rhythm are key to a healthy cardiovascular system. The contraction and relaxation of the heart muscle during systole and diastole are transmitted mechanically (through the walls of the blood vessels) and through the blood (via the aorta and its branches) all the way to the extremities, right to the fingertips. On the nail bed, the pulse oximeter sensor can register pulse waves as well as blood oxygen saturation.
In a number of diseases, oxygenation – that is, blood oxygen saturation – is impaired, which is a limiting factor in rehabilitation, so the rehabilitation process has to be adapted, especially in postoperative rehabilitation and/or in people who are physically inactive or poorly trained and want to return to training and greater daily exertion. The heart and the respiratory system are closely linked, so it is no coincidence that they are referred to by a single term: the cardiopulmonary (heart-lung) system. Any activity or inactivity of our musculoskeletal system has perhaps its greatest impact on this system.
During the rehabilitation of cardiac patients after a myocardial infarction, bypass surgery or vascular implants, and of all older people with a heart arrhythmia (most often atrial fibrillation, but also other heart rhythm disorders), we must use monitoring – by observation, clinical examination or with instruments. Patients with chronic obstructive pulmonary disease, asthma, emphysema or allergic lung diseases also have reduced blood oxygenation, which is why, during rehabilitation, the physiatrist must and can monitor their state of health in order to adjust and modify the exercise therapy, that is, the exercise programme, both aerobic and anaerobic. On the basis of the clinical examination, the physiatrist can also order other tests, in cooperation with other clinical specialties (especially cardiology). Monitoring is needed for cardiorespiratory patients, and also for patients after musculoskeletal trauma or with arthritis, because these patients are at risk of cardiovascular events. This is supported by recent studies showing accelerated vascular ageing in all patients with inflammatory rheumatic diseases and a higher rate of all cardiovascular and cerebrovascular events, particularly myocardial infarction, atherosclerosis, stroke, degeneration of the heart's conduction system and neurodegenerative changes.
Ancient Chinese medicine pays particular attention to analysing the pulsation of the blood vessels, as does the Western tradition. Newer technologies make this analysis easier, but nothing can replace a medical examination, during which the doctor obtains a great deal of information about the person's physical and mental state. In doctors' medical training, particular attention is paid to the pulse, because it reveals a lot about a person's clinical condition. An adult's pulse is usually 60–80 beats per minute. A slow heart rhythm is called bradycardia, a fast heart rhythm is tachycardia and an irregular heart rhythm is called arrhythmia, while occasional irregularities noticed during an examination do not necessarily have a pathological origin. Simply by modulating our breathing, we can change the heart rhythm.
The pulse is synchronised with the work of the heart and the peripheral arteries. It is usually measured by counting the beats over 15 seconds and multiplying by 4, which is a quick and effective way to check the heart rate. A more detailed evaluation of the pulse requires a longer analysis, which is carried out when arrhythmia, atherosclerosis, poor circulation or blocked blood vessels are suspected.
