The rising number of COVID-19 cases prompted me to create this explainer video on how to use the pulse oximeter correctly. The normal oxygen saturation (SpO2) of a healthy person is between 95 - 100%. It is important to monitor the SpO2 at least daily, better several times a day, for Category 1-2 patients undergoing home quarantine.
The normal oxygen saturation or SpO2 of a healthy person is 95 – 100 %. These numbers generally stay unchanged during moderate intensity exercises and may even increase a little, because one is breathing faster and deeper, resulting in better lung ventilation.
During vigorous short-term exercise, like
in soccer, you may notice a small drop in blood oxygen saturation of about 1 –
2 %. When you stop exercising, the SpO2 will return to your baseline reading quickly.
When a
person complains of shortness of breath, the doctor will take down a medical
history, perform a physical examination and may order some tests. Diseases of the heart, lungs, kidneys or
liver may present with shortness of breath.
The most common functional impairment in patients with lung
disease is impaired gas exchange. In the early stages of many lung diseases, the
oxygen saturation is maintained or is normal at rest, but when the lung is
challenged with increasing demand, like during exercise, the oxygen saturation
may drop.
The 6MWT is used to assess the functional capacity of a
person. The 6MWT is also a simple test
to evaluate gas exchange impairment during exercise. It is widely used, and is considered the gold
standard, to evaluate patients with chronic respiratory disorders like COPD and
ILD. However, it is not feasible to
perform the 6MWT in many office-based practices, which generally, do not have
the flat, straight 30-m corridor required for the test.
There is evidence in the literature, suggesting that the 1MSTST
be used as an alternative to the 6MWT for measuring a person’s functional
capacity and in detecting exercise induced gas exchange impairment. Both tests have a good correlation, and the
advantage of the 1MSTST is that it causes less hemodynamic stress for patients
than the 6MWT. The 1MSTST is well tolerated, easy to perform, understood, and
interpreted; and does not require special hardware.
The mean number of 1MSTST repetitions reported in the literature
achieved ranged from 8 repetitions (patients with stroke) to 50 repetitions (young
men).
The 1MSTST has been validated for use in COPD and ILD of
various aetiologies.
There are many uses for the 1MSTST:
The 1MSTST is used to identify subjects with low exercise
capacity or preserved exercise capacity.
The 1MSTST is used to detect exercise-induced gas exchange
impairment early in the course of ILD, before changes in resting DLco and PaO2,
hence making the early clinical diagnosis of ILD possible. The resting DLco is a specific but an
insensitive predictor of abnormal gas exchange during exercise. The DLco is the
diffusing capacity of lung for carbon monoxide is a measure of the efficiency
of lung gas transfer.
The 1MSTST is used to measure the effectiveness of a
pulmonary rehabilitation programme as an improvement of three repetitions is
consistent with physical benefits.
To perform the 1MSTST place a chair of standard height
(46 cm), without arm rests, against a wall to prevent the chair moving and person
falling during the test. Seat the person upright on the chair with knees and
hips flexed at 90°, feet placed flat on the floor and a hip-wide apart, with
arms held stationary by placing the hands on the hips. The person is asked to
perform repetitions of standing upright and then sitting down in the same
position at a self-paced speed, safely and comfortably, as many times as
possible for 1 minute. The person should not use the arms for support while
rising or sitting. The person is permitted to rest during the one-minute
period.
The patient is given the following instructions:
“The purpose of the test is to assess your exercise capacity
and leg muscle strength. The movement required is to get up from this chair
with the legs straight and sit back continuing the repetitions as fast as
possible within one minute. I will give you the countdown ‘3, 2, 1 Go’ as an
indication to start and I will tell you when we are at the 15 remaining
seconds. If required, you can make a break and resume the test as soon as
possible”.
The patient should be able to perform a minimum of 5
repetitions.
The SpO2 and heart rate are noted before and immediately after
the 1-minute test. The SpO2 and hear
rate are noted for a further 1 minute following the test, during recovery, as oxygen
desaturation can continue for up to a minute after stopping the test. The number of sit-stand repetitions are
recorded for the first 1 minute of the test.
In early lung disease, a person at rest, may have a normal
SpO2 of 95 – 100 %. However, during
exercise the SpO2 may drop because of increased oxygen demand and the presence
of impaired gas exchange in the diseased lungs.
POSITIVE TEST. A SpO2
drop of 3% or more is considered a positive test. A positive test may indicate the presence of
lung disease which requires medical attention.
DO NOT perform the 1MSTST in the following situations.
1. When the resting SpO2 is already abnormal at 94% or less.
2. When the person is immobile or using walking aids.
3. During advanced pregnancy.
4. Following recent abdominal surgery or heart attack.Fo
F STOP the 1MSTST when you notice the following:
1. Feeling faint or giddy.
2. Vision becoming dim or blur.
3. SpO2 falling more than 3% from baseline. (Calculate the value before starting the test. Example: when the resting SpO2 is 96%, stop
the test when the SpO2 fall to 93% or lower.)
4. Sensation of breathlessness which is severe or unbearable.
5. Occurrence of chest pain
You MUST CONSULT a doctor when the test is positive.
The 1MSTST is currently being evaluated for use in
respiratory illnesses other than COPD and ILD.
The IMSTST is being used in some EDs or emergency departments to quickly identify exercise induced oxygen desaturation caused by lung disease, so a decision can be made regarding patient discharge, with or without enhanced monitoring, or hospitalisation.