What does pi on a pulse oximeter mean

Monitoring your body

Learn from your body by monitoring yourself in the morning, after exercise, or anytime you want to know what your body is telling you

Morning monitoring

• Keep your MightySat at your bedside and each morning
• Monitor yourself before you get out of bed
• Establish your normal, or “baseline” values
• Oxygen saturation (SpO2)
  • A fully oxygenated body generally means a fully recovered and ready body. An SpO2 between 97 and 100% means your body is ready!
  • Note: At higher elevation starting at about 3,000 feet, it is normal for your SpO2 to be 3 to 5% lower. The higher elevation you go, the lower your SpO2 will be.
• Pulse Rate (PR)
  • Your pulse rate changes constantly to provide the necessary blood flow to deliver the oxygen your body needs. Generally, a lower resting pulse rate (40 to 60 beats per minute) means your body is performing more effectively and efficiently.
• Perfusion Index (Pi)
  • Your perfusion index changes based on whether the blood flow to your body is going up or down, and whether the arteries in your fingers are narrowing (causing your fingers to feel colder) or widening (causing your fingers to feel warmer). There is no specific “normal” value for perfusion index, each person should establish their own baseline value and note how it changes over time. A higher perfusion index means greater blood flow to the finger and a lower perfusion index means lower blood flow to the finger. Your perfusion index may or may not change significantly in the morning or after exercise. Note any changes to your perfusion index and whether you feel any differently when your perfusion index is lower.

After exercise monitoring

• Keep your MightySat with you when you exercise
• Immediately after exercise, measure how long it takes for your measurements to change
• Oxygen saturation (SpO2)
  • Measure how long it takes for your oxygen saturation to return to your baseline value (example, from 95% to 98%).
• Pulse Rate (PR)
  • Measure how long it takes for your pulse rate to go down by 20 beats per minute (example, from 160 to 140 beats per minute).

Live at your best by tracking and trending your data to make adjustments in exercise, diet, or rest/relaxation

Morning monitoring

• Oxygen saturation (SpO2)
  • If your oxygen saturation drops more than 3% from baseline, or if it is below 96%, this may be an indication that you need more rest and recovery
• Pulse Rate (PR)
  • If your resting pulse rate is 10 beats per minute higher than normal, this may be an indication that you are dehydrated, stressed, or fatigued. This may be an indication that you need to rehydrate, relax, or skip intense workouts.

After exercise monitoring

• Oxygen saturation (SpO2)
  • If your oxygen saturation takes longer to return to your baseline value, this may be an indication that you need more rest and recovery.
• Pulse Rate (PR)
  • If your pulse rate takes longer than usual to fall by 20 beats per minute, this may be an indication that you need:
    • To rehydrate
    • Give yourself more rest and recovery
    • Change your workout regimen, as you may have hit a plateau and may need a different type of workout to make progress (example, if you have been doing all aerobic training at moderate pulse rate levels, you may need to consider more interval training at higher pulse rate levels to improve your recovery time).

Silent hypoxia is one of the symptoms in which Covid-19 patients have alarmingly low blood oxygen saturation levels, yet they do not show any other symptoms of Covid-19 or breathlessness to identify the hidden danger. The pulse oximeter, a non-invasive device of arterial blood oxygen saturation and pulse rate, can help people to monitor the symptoms at home, and ask for medical care sooner before this deadly symptom kills them. It has been in high demand recently, although it is not always reliable to identify that you are Covid-19 positive or not. But you can consult a doctor if you find any abnormality in the pulse oximeter reading.

How does a pulse oximeter work?

It uses light to work out oxygen saturation levels. The probe has a light source on the upper side and a light indicator on the lower side. When a finger is placed on the probe, a part of the light will be absorbed and the rest won't be. The amount of light that is absorbed depends on the physical properties. And these are used by the pulse oximeter to determine the oxygen saturation. According to the World Health Organization (WHO), oxygen saturation (SpO2) should be between 95% and 100%. If the rate is 94% or less than it, the person needs to be treated quickly. Less than 90% of oxygen saturation is a clinical emergency. The normal perfusion index (PI) ranges from 0.02% to 20% showing weak to strong pulse strength.

How accurate is it?

You can never say that your oximeter is 100% accurate. It can show a 2% over or 2% under due to your arterial blood gas or mechanical fault. Remember that while determining an emergency. For example, if your oxygen saturation is 96% according to a pulse oximeter, then it is anywhere between 94% and 98%. And some factors may affect the actual reading too.

Factors that might adulterate a pulse oximeter reading

According to the World Health Organization (WHO), nail varnish or any kind of pigment on the finger, user's movement, bright light on the probe, poor perfusion, and carbon monoxide poisoning might adulterate or stop a pulse oximeter reading.

Nail varnish: Nail polish colours contain organic or inorganic pigments that can absorb the light emitted from the oximeter that detects the pulse rate. These can work as a hindrance on the way to show the actual oxygenated haemoglobin of a person. So it's always best to remove nail colours to avoid the confusions. For emergency, put the finger turning sideways.

Henna pigmentation: Henna on the hand represents dark skin pigmentation that absorbs the light at two wavelengths and allows the infrared light to infiltrate. The outcome will faulty in this case.

User's movement- If the person who is using the oximeter has a condition that leads to rapid movement or to shiver or moves being careless while checking, the pulse waveform can fluctuate. The reading will be misleading. Both the user and oximeter should be in a steady position to get the proper result.

Bright light on the probe: The interference of light on the probe will create an erratic result if it directly reaches the sensor. It has soft rubber to shield the probe from light, but when the light shines directly on the probe or the presence of radiated lights such as infrared or ultraviolet enters, it'll impact the reading.

Poor perfusion: If the perfusion index is at or below 0.4% showing weak pulse strength, then the oximeter reading can be unreliable. Peripheral artery diseases, diabetes, obesity, blood clots, etc. are the reasons of poor perfusion.

Carbon monoxide poisoning: Carbon monoxide molecules easily replace the oxygen molecules and turn haemoglobin bright red. The pulse oximeter is unable to distinguish between carbon monoxide and oxygen and so the result is faulty. For example, the reading will be misleading for up to 4 hours after smoking. People who have recently inhale smoke from fires or heavy traffic environments will also have faulty readings.

Which finger should you choose for pulse oximeter?

The third finger of the dominant hand has been considered the best option for a pulse oximeter. The second option can be the dominant thumb. That means if you are right-handed, use your right middle finger or thumb. And left middle finger or thumb for left-handed people. The difference between fingers is not huge. So it's fine if you are using your index finger.

Should one have a pulse oximeter amid this pandemic?

"Pulse oximeter does not identify Covid-19. It only shows the changes in the oxygen saturation in the blood, regardless of cause. However, the pulse oximeter is useful for monitoring oxygen levels at home, as falling oxygen saturation is an indication for hospitalization when Covid-19 is suspected. Thus, given the circumstances, it is better to have one at home", said Dr. Shahida Akhter, senior consultant at BIRDEM and professor at Ibrahim Medical College.

What is normal PI on pulse oximeter?

What if Pi is high in oximeter?

What is considered a low perfusion index?

What is Pi in oximeter 4%?