Do I Need Oxygen Therapy?

[Thomas3.20.2010]

Let's start with a few questions:

Have you had a Spirometry Test?

Have you had an ABG (arterial blood)?

Have you been measuring your Oxygen Sats with an Oximeter?

My guess is the answer to some if not all of these questions is yes. But it helps to know your numbers.

So without having those numbers I can only explain the reasoning behind Oxygen Therapy diagnosis.

According to the American Thoracic Society, every cell in your body needs oxygen to live. Unfortunately, your pulmonologist believes that your lungs can no longer provide the amount of oxygen your body needs. This may be caused by one of two things: either the airways have narrowed and become blocked by mucus or damaged alveoli in the lungs can no longer absorb enough oxygen.

Either way, blood oxygen levels can become dangerously low in your body especially when you are exerting yourself or when you are sleeping or both. Since the body cannot store oxygen, therapy may be used to deliver this life-saving element to your lungs up to 24 hours a day.

Determining How Much Oxygen You Need

Oxygen therapy is used to ensure the amount of oxygen in your bloodstream remains at a healthy level. Breathlessness alone is not a good indicator of whether you need this therapy. Many people who need oxygen therapy don't feel short of breath, yet they lack the oxygen to stay healthy. Your doctor will use more precise methods to find out how much oxygen you need and when you need it. He or she does this by running these tests, according to American Thoracic Society:

Arterial blood gas (ABG): This measures carbon dioxide, oxygen and pH levels in the blood. The test is conducted at an office or hospital where ABG equipment is available.

Pulse oximeter: This is not as precise as an ABG and should only be used as a guide to oxygen therapy. It involves placing a clip on your finger and shining a light through. A tiny computer determines the oxygen level based on the color of the light passing through your finger. Often your pulmonologist will order a sleep oximetry test to find out your oxygen levels during sleep - which tends to be lower than waking hours.

Based on the results of these tests, your doctor can determine the rate of oxygen delivery you need, how many hours a day you should use it and whether you need to use oxygen while you sleep.

If you have a general understanding of what each of the numbers mean, then you won't be in the dark when docs, nurses, or respiratory therapists are throwing these numbers around. You'll have a better understanding of what is going on inside your body.

Oxygen enters the blood inside the lungs and is delivered to each cell in your body. Blood is made up of a bunch of stuff, but for this discussion, we'll focus on red blood cells (RBCs) and plasma. RBCs are what makes your blood red whereas plasma is a clear fluid that the RBCs travel in.

What I've found is that most people don't realize that oxygen is moved from the lungs to the cells in your body inside the blood in TWO ways, not just one.

Oxygen is transported inside the RBCs AND dissolved in the plasma. The pulse-ox number is having a look at how full the RBCs. The ABG is looking at how much oxygen is dissolved in the plasma (like salt dissolves into water). The pulse-ox number is important because about 98% of your oxygen is found inside the RBCs. The ABG number is important because it gives information about how well oxygen is getting into your blood in the first place.

When I describe what the pulse-ox/ABG numbers means, I use a story about washing the dishes.

You fill up the sink with water and you reach for a dry dish rag. You submerge the dry dish rag into the water and pull it out soaking wet; the rag couldn't possibly hold anymore water. You might say that the rag is 100% saturated.

Well you continue on and you wash all of the dishes. When all the dishes are clean, you look down at the floor and realize that you've spilled water all over the place. So you reach for a new dry dish rag and soak the water up off the floor and counter. You notice that the rag is wet, but you could still pick up more water if you needed to; maybe it's 80% saturated.

In this example you can think of the oxygen dissolved in plasma as the water and the RBC as the dishrag. The amount of oxygen (water) available in the plasma determines how much is soaked up by the RBC (dishrag)

The pulseox is telling you how full the RBC is as a percentage and the ABG is giving you a pressure (P) of oxygen (O2) in plasma in pressure units of millimeters of mercury, or mmHg.

Here are the steps that oxygen gets into your blood:

1. you breathe a nice deep breath
2. the air travels down your windpipe and deep into your lungs
3. just like the smell of freshly baked cookies travels from the kitchen to the living room, oxygen travels from the lungs into the plasma of the blood.
4. once in the plasma, the oxygen is absorbed by the RBC.

Step 3 is what the ABG results reveal

Step 4 is what the Pulseox reveals

Further:

Pulseox reading 99% is approximately PO2 of 100 mmHg

Pulseox reading 96% is approximately PO2 of 80 mmHg

Pulseox reading 90% is approximately PO2 of 60 mmHg

Pulseox reading 75% is approximately PO2 of 40 mmHg

The ABG results also reveal the amount of carbon dioxide in your blood this number is PCO2. P for pressure and CO2 for carbon dioxide. The results also show the pH of your arterial blood.

If your Pulseox is consistently below 90% then otherwise healthy cells in your body are dying prematurely and eventually you will feel sympoms. Also, when your oxygen /CO2 exchange is not working properly you are putting extra stress on the right side of your heart which must use only oxygen rich cells but must pump a lot of blood back around because it's not oxygenated enough. eventually this work will cause the right chamber of your heart to enlarge (Congestive heart failure.)

My recommendation to you, Dear Reader, is to ask your Doctor to explain all of this to you until you 100% get it. If you are still not convinced then get a second opinion. If 2 good pulmonologists are telling you that you need Oxygen Therapy, then by all means - DO IT! It is saving your quality and quantity of Life and although a big lifestyle change, it's well worth it!

[constanceclum]

I became aware of needing O2 because I told my Doc I was tired all the time. She ordered a sleep test and we discovered my levels were dropping at night. I had been diagnosed with COPD but other than shortness of breath on exertion, was able to function pretty normally so, yeah, pretty important to stay on top of.

Connie

[elvan]

I use oxygen at night but, admittedly, not every night.  I sometimes fall asleep and forget to put it on.  I do measure my oxygen saturations with an oximeter and they are consistently at 93% or higher...UNLESS I am bending over and compressing my lung tissue, I will become markedly short of breath and my oxygen saturations have dropped into the 70's with a pulse rate in the mid 30's.  My normal pulse is 60-64.  I have had an EKG, and echocardiogram, and a stress test and all showed that my heart has no issues at this point. The drop that I mentioned about only lasts seconds and I can get my sats up by taking deep breaths and my pulse responds accordingly. I told my pulmonologist all of this when I saw her.  I have not had an ABG in years and years and when I had them, I had pneumonia and I was hospitalized.  I must admit that I have been surprised that they never ordered one.  I am getting the full respiratory testing done in August unless I have some issue before then.  I was surprised to hear that oxygen saturations drop at night...when they did my overnight oximetry, it was reportedly shown that my sats dropped into the high 80's more than once.  I checked that oximeter whenever I woke up and I wake up a LOT at night, it was never reading lower that 95%.  Go figure.

[Thomas3.20.2010]

While a DLCO may be helpful, the best measure for assessing your cause of SOB is really doing a walk test WHILE ALSO measuring your oxygen saturation.  If your saturation drops below 88 % - and keep in mind, a true measurement in that range REQUIRES that you walk NON-STOP for at least 90 seconds or more -  then you can assume that your CO2 (not necessarily O2!) goes up, a sign that your have 'dynamic hyperinflation' and a CO2 increase accompanied by a decrease in pH, the LEADING cause of desaturation during exertion for those with advanced COPD.  The best measure would be a blood gas done WITHIN a maximum of 45 seconds after walking for 2 or three minutes NON-STOP, which would reveal exact measurements of pO2 and pCO2, as well as pH.    The problem with doing the blood gas is that too often, the blood sample is obtained far longer after that 45 second window when oxygen and carbon dioxide have already moved SIGNIFICANTLY back towards one's baseline.  So, the ABG doesn't reflect the "true low-point" in one's O2 and CO2 blood gas changes.

So, if you are going to the doctor, ask about doing a walk test with saturation measured DURING the walk test.  AND, don't let whoever guides you through the test stop you if you drop into the 80's.  You need to find out just how low you go to determine IF you need supplemental oxygen during activity AND roughly how much.  Another walk test while wearing oxygen would help to "titrate" the flow to cover your needs AND to determine how your exertional oxygen flow should be ordered/set.

Source: Dr. Mark W. Mangus, Sr., BSRC, RRT, RPFT, FAARC
San Antonio, TX

Thomas: Saving this for future reference.

[elvan]

I had to have oxygen on to do the walk test before I had my surgery but since then I have done the 6 minute test and not dropped below 92%...UNLESS they make me talk and then it drops and I can FEEL it.  I cannot walk and talk at the same time...even SINCE the surgery.