7-29-2017: I was unable to find the resource cited in this post on searching. Please see the following subsequent posts on exercise oximetry from this blog:
- Exercise Oximetry And Walking Tests in Chronic Respiratory Diseases
Posted on July 27, 2017
- A 2012 Algorithm For Assessing Fitness To Fly In COPD Using Rest and Exercise Oximetry Posted on July 24, 2017
What follows is a protocol on when and how to do exercise oximetry.
Exercise oximetry is indicated for all patients who are short of breath unless they have contraindications.
Exercise oximetry is contraindicated in patients with unstable ischemic heart disease. However, stable angina is not a contraindication to exercise oximetry. Patients who have severe arthritis or back pain or leg weakness and who are unable to walk won’t benefit from the test. The test is not indicated in patients who are severely short of breath at rest or who have marked resting hypoxemia on oximetry.
Performing the test:
Place the oximeter on the patient’s finger and wait until the oxygen saturation reading is stabilized for at least 1 min. If after a minute it continues to fluctuate, say for example between 93 and 96%, record the average value or the most persistent value as well as the range.
Record the patient’s exercise time with a stopwatch because it’s much more accurate than your wristwatch.
The patient is asked to climb on and off the 18 cm step. Ask the patient to do this at a rate that’s comfortable for them and that they’ll be able to keep doing for 3 min. If he or she goes too fast they’ll tire out too soon.
Tell the patient to stop if he becomes too short rest or if he has any other symptoms that are uncomfortable such as chest pain or joint pain or weakness in the legs.
You need to record the reason for stopping if the patient has to stop before 3 min. are up. And also you need to record whether or not shortness of breath is present at 3 min.
If the patient is old or weak or unstable, it’s a good idea to help support the patient’s balance by holding on to the hand or forearm on which the oximeter has been placed. Don’t touch the finger on which the oximeter is placed however because pressure or motion artifacts on the oximeter can lead to measurement error.
Have the patient exercise for 3 min. if they can. But there’s no point in having them exercise longer than 3 min. because longer tests don’t add anything. Again, reminded patient that they can stop anytime the become shorter breath or have other uncomfortable symptoms. Just record why they stopped early and the time at which they stopped.
When the patient stops exercising, you should record: the oximetry and pulse rate immediately following cessation of exercise, the time of exercise, the number of steps the patient took (so you’ll need to count the steps during the test), and record why the patient stopped.
Keep monitoring the oximetry for at least 1 min. following the cessation of exercise. This is because most people who do desaturate will have their lowest saturation about 30 to 45 seconds after they stop exercising. Write down the lowest post exercise saturation.
Record any abnormalities of breathing that occurred during the test (for example breath holding or hyperventilation or noisy breathing [upper airway breathing sounds]).
Background information on the exercise oximetry test:
The normal resting oximetry for adults is between 96 and 98%. That value should not fall with exercise. However it might be a little bit lower in the elderly and many patients who have significant lung disease will have low resting oxygen saturation’s.
It is normal for the oxygen saturation to fall up to 3%. Thus, if the resting baseline oxygen saturation is 95%, a fall with exercise to a low of 92% would be normal. But if the exercise oxygen saturation falls more than 3% below the baseline oxygen saturation that is usually significant.
Don’t let the hand with the oximeter on it swing freely as that will cause a motion artifacts that can cause inaccuracy. Also nail polish can interfere with the oxygen saturation accuracy. So if the patient has nail polish on, remove it or place the oximetry sensor as high as possible on the little finger.
Make sure that the patient does not hold his breath during the exercise and make sure that he doesn’t Valsalva as these can produce rapid desaturation. Remind the patient to breathe normally.
Hyperventilation, upper airway dysfunction, vocal cord adduction, or extreme breath holding can also affect the test results. Any abnormal breathing during the test needs to be documented.
*The source of this post is “exercise oximetry as part of respiratory assessment and preoperative assessment in Salford Royal foundation trust” which I found by searching Google with the query “exercise oximetry”. Unfortunately, it automatically downloads as a pdf and there is no link that I can post. By putting the title in quotes into the Google search box, this pdf will be at the top of the page. The author is Dr. Ronan O’Driscoll.