(Update August 11, 2021)
Not everyone could use oximeters effectively. In the UK, experts have found that these devices would give “misleading readings” for patients with dark skin.
On Saturday July 31, the British public health service (NHS) revised its instructions for the use of these devices. The change comes after a study in April that found that pulse oximeters sometimes boost blood oxygen levels for people with darker skin color, leading to a misleading reading. However, a misleading number can delay hospitalization or oxygen intake.
“We must ensure that we have knowledge of the potential limits of certain health equipment, in particular for populations at increased risk of the disease,” said Dr. Habib Naqvi, director of the Observatory of race and health. Despite these findings, the NHS recommends that the entire population continue to use the oximeter.
As a result, the health department is now advocating paying more attention to changes between readings than to numbers given, which always allows you to see if oxygen levels are dropping, even if the oximeter is not fully accurate. .
How does a pulse oximeter work? for what indications?
Available on the Internet or in pharmacies, pulse oximeters measure the amount of oxygen in the blood. Covid-19, asthma, COPD … in which cases are these self-measuring devices useful? What are their limits ? Repayment ?
Measuring the main parameters of your health yourself to take better care of yourself or heal yourself is a fundamental trend, thanks in particular to connected objects. And pulse oximeters are no exception. We find them free on the Internet, in pharmacies or in certain supermarkets, at prices varying from tens to hundreds of euros. But are they really useful?
What is a pulse oximeter? What is it used for ?
Thanks to a sensor usually placed on the end of a finger, the pulse oximeter measures the amount of oxygen circulating in the blood of the arteries. the manual is simple: slide your finger into the device and close it to lightly pinch your finger. A light beam then passes through the skin and measures the pulse and blood oxygen saturation.
Oximetry: what is the normal value?
In general, this rate is between 95% and 100%, which means that each red blood cell contains 95% to 100% oxygen. Depending on the person, it may be between 90% and 93% suitable, but should alert when it goes below 90% (this is called desaturation).
How to properly use a pulse oximeter?
- Put your finger correctly (preferably middle finger or index finger) at the bottom of the appliance and stand still.
- Take the measurement in a vertical position (sitting or standing).
- Do not have your fingers too cold (warm your hands slightly if necessary).
- Avoid wearing nail polish (the light beam may not be well absorbed by the skin).
- Keep the pulse oximeter in place for at least a minute (or more, if the value has not yet stabilized).
To note : saturation is generally low when you wake up, better to wait a little before taking it.
The pulse oximeter, useful in the face of Covid-19 and reimbursed at 100% for some patients
Oximeters are used to measure blood saturation at home in oxygen, therefore early detection of worsening symptoms of Covid-19 and avoid emergency hospitalization. The World Health Organization has recommended their use since January 2021.
“The objective of the first-line medical prescription for monitoring pulsed oxygen saturation (SpO2) is to prevent the possible worsening of patients with respiratory signs and / or with serious risk factors for the disease. Covid-19 and / or over 65. “
“The prescription specifies the daily monitoring frequency (at least 3 times per 24 h), the duration of the surveillance (until D14 after the onset of symptoms or after the date of the positive test if the patient is asymptomatic) and the characteristics of the device (medical device CE marked conforms to the ISO standard 80601-2-61“Says the Directorate General of Health in a press release published on April 26, 2021 (source 2). Oximeters on a smartphone or a connected watch are therefore not supported.
Regular monitoring of patients at risk of severe disease is necessary with in particular a consultation of control between the 6th and the 12th day after the onset of symptoms or the result of prescriber testing.
(Haute Autorité de santé, April 8, 2021, source 3) © Haute Autorité de Santé
Pulse oximeter is not that useful in asthma
Dr Nicolas Postel-Vinay, founder of the medical site automesure.com, and Dr Yacine Tandjaoui-Lamotte, resuscitator at the Avicenne hospital, in Bobigny, are worried about advertising messages touting the usefulness of pulse oximeters to monitor the development of asthma. “No study allows to recommend it in this disease”, indicates Dr. Jesus Gonzalez, head of respiratory equipment of the pneumology department, at the hospital of La Pitié-Salpêtrière (Paris).
“Apart from the seizures, the person is well, his hemoglobin saturation curve is almost normal. But this curve can drop suddenly during a seizure; the person is breathing poorly, is agitated and if the usual treatment does not help. no effect, sometimes you have to call emergencies, “he continues.
During a acute asthma attack, the oxygen saturation can drop below 90%. If the amount of oxygen drops during an asthma attack, measuring it does not necessarily detect it before it occurs.
Pulse oximeter helps better manage COPD
On the other hand, specialists believe that the pulse oximeter can be useful in cases of chronic obstructive pulmonary bronchitis (COPD). Affecting mainly smokers, it causes a significant decrease in respiratory function. “In these patients, the slightest element like a tired or a little bit of fever, can trigger a drop in oxygen saturation, continues Dr Gonzalez. In this case, the oximeter is interesting for detecting it. ”
The oximeter is all the more useful for advanced stages of COPD, which make it necessary to live a large part of the day under oxygen to keep saturation greater than 90 %. “These people must control their oxygen therapy device on their own, says Dr Postel-Vinay. This is why they know perfectly well how to use the pulse oximeter for their therapeutic monitoring. ”
At milder stages of the disease, “use a pulse oximeter strengthens the feeling of taking charge of one’s health, specifies Dr Tandjaoui-Lamotte. This is especially true during physical activity, such as active walking. Recommended by doctors for people with COPD, it improves their quality of life and can make them gain one or two saturation points after a few months of training. Viewing your progress on the screen of a pulse oximeter can be a good motivation to keep going.
The pulse oximeter is also useful for returning to sport
“The pulse oximeter is interesting for people returning to exercise with respiratory risk factors, such as former smokers “, indicates Pr Xavier Bigard, scientific adviser of the French Agency for the fight against doping. Observing the evolution of its reoxygenation performance over the weeks reassures and motivates.
But “be careful that these connected objects do not become anxiety-inducing!” Continues the specialist. ‘Stop.”
How do you choose the right pulse oximeter?
Before using this self-measuring device, it is essential to seek the advice of your doctor or pharmacist. He alone can help determine the hemoglobin saturation figures from which to act or not.
- To find your way around, the first criterion is the medical CE mark.
- Ideally, the device should also respond to the ISO standard 80601-2-61.
- Otherwise, check if the instructions specify the inaccuracy of the device, namely less than 4%, between 70 and 99% oxygen saturation.