What Setting is Correct?

I recently received the following email from Tom in Florida.


I responded as follows.


In the article "Hypoxia, Oxygen, and Pulse Oximetry," Dr. Fred Furgang suggests minimum requirements for pilots so those pilots are adequately oxygenated without wasting the oxygen their planes are carrying. He suggests pilot start supplemental oxygen when an oximeter reading is below 90 percent and continue to monitor saturation every 15 minutes. Dr. Furgang suggests keeping the pilot's saturation at 91-92 percent for remedial tasks and at 93-94 percent for tasks that require reasoning and/or physical action. To me that means rest or sleep in the lower range, but don't argue with my spouse, carve a turkey, or drive the car unless I am in the higher range.

So, if you aren't flying an plane in the stratosphere, what oxygen settings should you be comfortable with? The best place to answer this question is in your doctor's office. To help with the discussion, collect information about the times you are short of breath. What were you doing? What was your oxygen setting? What was your saturation and pulse readings? If your saturation was below 90, how long did it take to recover and at what oxygen setting?

On the other hand, being SOB is only indirectly related to a need for more oxygen. When my chest feel tight and unable to expand, the problem is often eased with a puff of albuterol or a nebulizer treatment. I find that tightening of the chest is also be related to a lung infection, particularly when my pulse rate are elevated.

Can you set oxygen too high? From a conservation point-of-view, the answer is "Yes." Setting your portable too high means exchanging or refilling oxygen units more frequently than necessary.

From a medical point-of-view, the best authorities I can find say No, you cannot set your oxygen too high.  

"...the current widespread assumption that everyone with a diagnosis of chronic obstructive pulmonary disease should therefore have their oxygen treatment drastically restricted is dangerous. Where there is a suspicion of a retention of carbon dioxide, further history should be sought to avoid increasing hypoxia in an already exhausted patient." (Source: Inglis, Andrew et al. Letter to editor. (British Medical Journal, 31 March 2001)

The myth that too much oxygen causes a carbon dioxide (CO₂) retainer to stop breathing has never been verified or documented. Recent and ongoing research, particularly that which is being done by Richard Casaburi and his colleagues is increasingly showing that higher saturation does not pose a risk for those who retain CO2. 

Why Oxygen at Night?

You may be surprised to learn that many oxygen users only require oxygen at night. Here are the symptoms that cause physicians to believe nighttime oxygen is required.

• Unusual sleepiness during the day may be caused by the inability to get quality sleep at night.
• Increased shortness of breath when lying down. Patients with this condition often sleep with multiple pillows or in a recliner.
• Waking up suddenly at night short of breath.
• Morning headaches caused by noctural hypoxia.

One cause may be apnea--the absence of spontaneous respiration. Sleep apnea occurs when nighttime breathing stops many times. Severe snoring may be a sign of sleep apnea, particularly when accompanied by any of the above symptoms. For more information,  see the American Sleep Apnea Association.

A second cause may be reduced oxygen levels in the blood as you sleep. During the day, such factors as level of activity and weather conditions have the greatest influence on oxygen consumption. Some of us desaturate in hot weather, whereas others desaturate in cold weather. Some of us can predict stormy weather by becoming more breathless as the atmospheric pressure drops. When we are at rest, under moderate or extensive exercise, or digesting a large meal all impact oxygen consumption.

Whereas those without COPD have nice dome-shaped diaphragms, which move air in and out of the lungs very efficiently, our lungs are in a constant state of over-inflation, causing our diaphragms to flatten and be unable to single handedly move air in and out of our lungs without some help. It is the skeletal muscles of the chest, shoulders, and abdomen that take help. 

When you sleep, the skeletal muscles go to sleep. Your breathing becomes shallow and breathing frequency decreases. The work of breathing at night is turned back to the flattened diaphragm, which is unable to adequately do the job and ventilation of the lungs falls to as low as half that during the daytime.

This is the first thing a doctor checks when you are diagnosed with COPD. Perhaps you, like me, went on oxygen during the night only and wondered why not also during the day? Now you know. You perhaps now understand why doctors prescribe sleep studies--studies where you are connected to a recording oximeter while you sleep.

Acquiring an Oximeter

All oximeters record both saturation and pulse. Pulse/oximeters come in three sizes—portable, handheld, and finger. All are self-contained and run on batteries.

• Portables, which have a lot of bells and whistles, are about the size and weight of a hardback novel.
  
• Handhelds are about the size of a large TV remote.
• Wrist oximeters which are worn like watches.
  
• Finger oximeters clip on the finger.

All are noninvasive and have a probe that clips to the finger. A cable connects to probe to portable, handheld, and wrist oximeters. The probe of the finger oximeter is built into its casing, so the entire unit sits on the finger when in use.

Some oximeters have features that might be important to you.

• Has a probe that attaches to the ear.
• Can store readings overnight.
• Sounds an alarm (important when a caregiver is involved)

Handheld Oximeters 

Wrist Oximeters

Finger Oximeters 

	IRC 600	Pulsox 2	BCI 3420	Nonin 9500	Nonin 9500
Height (in.)	1.7	2.2	1.7	1.3	1.3
Width (in.)	1.5	1.1	1.5	1.3	1.3
Depth (in.)	2.25	2.7	2.25	2.2	2.2
Batteries	2 AAA	2 AAA	2 AAA	2 AAA	2 AAA
Weight w/Batteries (oz.)	3	2.5	2	2	1.9
Auto Power Shutdown	Yes	Yes	Yes	Yes	Yes
Low Battery Indicator	Yes	Yes	Yes	Yes	Yes
Pulse Accuracy (%)	2	2	2	2	2
Saturation Accuracy (%)	2	2	2	2	2
Battery Life (hours)	18	?	16	18	21
Warranty (years)	1	2	2	1*	2
*Since 2004, Nonin has added an additional warranty year at no additional cost.

I have not heard from oximeter owners a single bad word about any of the above brands.

All oximeters have a warranty from the manufacturer. My personal experience is that oximeters last many years after any warranty expires, even when one is soaked in water. Remember that a warranty does not cover accidental damage. I suggest you use the lanyard to carry it about your neck. The one problem with that is your oximeter will catch food you drop and will need periodic disassembly and cleaning. Follow the instructions for cleaning that appear in your user manual.

Marketing Oximeters

There is quite a bit of competition among sellers of oximeters. Prices vary from between $200 and $400. Some sellers offer free shipping while others offer lower prices.

An oximeter is a medical device approved by the FDA. As such, it can only be sold by a licensed pharmacy and requires a prescription signed by a licensed physician. Many distributors ignore these requirements.

I do not usually recommend any particular distributor of any product when there are many to choose from. I do, however, in this case recommend AeromedixRx. This distributor is a pharmacy owned by a physician who, when asked will write a prescription for you. You will also find included with your oximeter Tips for Using Oximetry in Home Oxygen Therapy written by this physician. If you are a member of Pulmonary Paper, expect a $50 discount. by Brent Blue, M.D.

Insurance Coverage

Whereas Medicare will not cover the purchase by patients, many insurance companies will. If you are not on Medicare, your insurance company may pay for an oximeter.

For example, Aetna covers a pulse oximeter for home use for members with DME benefits who have ANY of the following conditions.

• To wean the patient from home oxygen
• To change in the patient's physical condition requires an adjustment in the liter flow of their home oxygen needs
• To determine appropriate home oxygen liter flow for ambulation, exercise, or sleep
• To monitor patients on a ventilator at home.

To be reimbursed, you may find it necessary to write a Letter of Necessity to your insurance company. Such a letter should be signed by your physician. For an example of such a letter see A Sample Letter of Necessity.
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