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Feeling muscle weakness, tired and fatigued. Why does my Sp02 levels drops down significantly?

Nov 2013
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Answered by

Practicing since : 1994
Answered : 5572 Questions
Hello Doctor:

I'm trying to get some answers to a health issue that has been with me for many years.
I first started to notice muscle weakness/fatigue around the age of 26. I was a very active soccer player in my teenage years....but "something changed" later on in life. When I attempted to restart playing on a soccer team around the age of 26...I couldn't. My fuscles would easily get tired and I could not last too long on the field. I would get fatigued and would not understand why. I have mentioned this issue to MANY doctors that I have seen over the years...but got no solid answers. I have been waking up during the night with a fast heart rate and many times feeling breathless. Generally...for many sleep has not been restful and I feel tired/sleepy during the day. For the longest while I've been told that that this is due to anxiety/panic attacks. Recently I noticed my breathing is "different" when lying in the supine position. Because I ended up in the emergency many times and always nothing was found after the usual tests(x rays, blood tests ECG)....I became curious enough and invested in a oximeter for some self experimentation. I discovered that my Sp02 drops down significantly when assuminng the supine position (say from 97% standing to 93%-92% lying down...while awake). During sleep...the SpO2 drops even more...I've noticed as far as the mid 80's(ie. I program the oximeter to wake me up is SpO2 drops below 90%). So in my view....all this years....this so called "panic attack" issue seems to have been a "SpO2 desaturation" issue....simply missed....because by the time the ambulance arrived...I was always in the sitting/standing position and the SpO2 numbers normalized....therefore...."the evidence of the crime scene always got erased". Recently the ambulance paramedics noticed the SpO2 drops and commented .."there is something physliological going on here". I am not saying that this issue has not made me more anxious over the years...anybody would become more anxious if this happened to them and basically got no answers,

Furthermore....recently I have had different episodes of fast heart rate (up to 160bpm) while awake. I saw a cardiologist and was able to record one of this episodes. He told me that he does not know why my heart speeds up but the sinus rythm is normal. Previously I had two stress echos that turned out to be normal. So I am told that my heart is fine.

I had some type of viral lung infection back in March/12 and it appears that since then my health has deteriorated even more. The supine desatuartion is more noticeble, my mood is more down and my intollerance to exercise is way more present that previously.

In late October I went for a sleep study I am waiting for the results. The technician who recorded the sleep study data commented that he did see SpO2 driops into the 80's during sleep.

Could this health issue that has taken so much...and for so long....from my life be some neuromascular condition that is "raising its ugly head" more noticeably at the moment?

I have tried to educate myself since I got no answers so far from the medical system here in Toronto, Canada. I think that I may be getting closer to the truth. I have been looking for an answer for the last 20+ years!!!!

Your input/suggestions/opinions will be greatly valued and appreciated!!!!

Thank you,
Posted Sun, 25 Nov 2012 in Brain and Spine
Answered by Dr. Sudhir Kumar 1 hour later

Thank you very much for posting your query. I appreciate the detailed description, which you have provided here, and I am pleasantly surprised with your good analytical thinking.

I agree with you, that it must have been depressing for you to not get an answer for your problems.

The commonest reason for your muscle fatigue is likely to be a neuromuscular disorder. In this group, there are two likely possibilities:

1. Neuromuscular junction disorder, such as myasthenic syndromes. In this condition, fatigue after exercise is common. There are a few syndromes, which can start from childhood too.

EMG, repetitive nerve stimulation, serum antibody testing and muscle biopsy are helpful in establishing the diagnosis.

2. Metabolic disorders of muscle, such as glycogen storage disorders (McArdle's disease, etc): exercise intolerance and fatigue are common in this condition. This also starts in childhood.

Diagnosis can be made with blood tests such as CPK levels, muscle biopsy, ischemic lactate test, etc.

For your supine desaturation, I would prefer the term "orthopnea". In this condition, respiratory problems begin on lying down, which may also lead to desaturation at times. Since, heart and lung problems have been ruled out, I won't discuss them.

From neuro point of view, two possibilities exist:

1. Neuromuscular weakness- weakness of diaphragmatic muscles on both sides can lead to orthopnea. Diaphragmatic weakness can be evaluated by fluoroscopy, and other radiological investigations.

2. Sleep apnea- this can be diagnosed with polysomnography (sleep study), which you have already undergone.

I hope it helps you a bit. I would be glad to answer any further queries.

Best wishes,
Dr Sudhir Kumar MD (Internal Medicine) DM (Neurology) XXXXXXX Consultant Neurologist
Apollo Hospitals, Hyderabad, India
Above answer was peer-reviewed by
Follow-up: Feeling muscle weakness, tired and fatigued. Why does my Sp02 levels drops down significantly? 1 hour later
Hello Dr. Kumar:

Thank you so much for your prompt and solid answer...with such oustanding help and expertise......I will get to the bottom of this condition...its just a matter of time!!! Although we have never met Dr. XXXXXXX intuition tells me that you are a brilliant doctor!!! I came across a powerpoint presentation by a University of Toronto Neurologist/Professor and slide 15 discuses arrhythmia (specifically WPW) also associated with a neuromascular disease. I am sending you the connection to the powerpoint presentation which you may find interesting since it relates to your field of expertise. Please see:


My question is....since arrhythmia/fast heart rate is discussed here....can this happen with a specific type of neuromuscular disorder/disease?....or can it be a symptom in various neuromascular disorders/diseases? Could this possibly explain my recent episodes of abrupt onset of fast heart rate(up to 160bpm)? If so....what causes the heart to beat in such a fashion if someone has neuromascular disease/disorder?

Thank you,
Answered by Dr. Sudhir Kumar 23 minutes later

Thank you for getting back with more details and for the appreciation.

Cardiac arrhythmias and other cardiac problems can occur with neuromuscular diseases. This is partly because the heart is also made up of muscle tissue, and a generalised problem with muscle tissue in the body is bound to affect the cardiac muscle too.

The intermittent tachycardia (fast heart rate) that you have is definitely abnormal and since it is not related to either exercise or fever or panic states (the three common causes of tachycardia), the most likely explanation is a cardiac arrhythmia.

The cause of tachycardia needs to be determined. Since your Holter is normal, what can help you is cardiac electrophysiological studies. This can be done in consultation with a cardiac electrophysiologist (a sub speciality of cardiology).

I would be glad to answer any further queries.

Dr Sudhir Kumar MD DM
Above answer was peer-reviewed by
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