[Diagnosis] confused by sleep study results from 2016

[anbr3]

I am a 32 year old male, 6'0 tall, and 225 pounds (BMI of 31). I had an at home sleep study done in 2016, to which my doctor said "your study is pretty normal so no need to investigate further". The doctor has since left the practice and I decided this week to pick up a bunch of reports from all my doctors over the years just to have for my records. The sleep study report said:

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a total of 14 respiratory events were observed. 0 obstructive apnea’s, 5 central apnea’s, 0 mixed apnea’s and 9 hypos was for a normal AHI of 1.9 events/hr.

The average saturation was 75%. Patient was at or below 88% oximetry for 19% of the study time. The lowest saturation was 89%.

Highest heart rate 91bpm. Lowest was 47bpm. Average was 59bpm.

Impressions: no evidence of sleep disorder led breathing. Significant desaturations noted.
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I am very confused by the saturation part of the study. How can my average saturation be 75% yet my lowest saturation be 89%? Also, why was this conveyed to me as a normal report. I am very confused about all of this.

[Walla Walla]

I'd show those results to another Doctor. Why your former Doctor didn't follow up on the desaturations I have no idea. But he should have.

[Sleeprider]

Home sleep studies notoriously under-estimate AHI because they usually count all hours as sleeping. So Events/hour are diluted. The fact your events are all central is a concern. I would want to follow-up with a clinical polysomnograph that can determine what is going on and whether the oxygen desaturation is real. Those are significant if real. In my opinion your doctor's conclusion was incorrect and your results should have prompted a clinical study.

[anbr3]

thank you.   can you clarify what you mean by "The fact your events are all central is a concern" ?  I'm new to all of this and I know there is Obstructive Sleep Apnea and Central Sleep Apnea, but a concern in what way?  

[Sleeprider]

I'm simply saying that the home study recorded all apnea as central, meaning that whatever technique was used, detected no respiratory effort during a no-flow of 10 seconds or longer. The study was unable to determine if hypopnea were central or obstructive, but central hypopnea usually go hand in hand with central apnea, and vice versa (obstructive apnea generally go with obstructive hypopnea). Combined with the 75% SpO2, these are not inconsequential and merit a clinical follow-up.

Here is the problem; many physicians think of sleep apnea in a binary logic. Apnea is obstructive, and you don't have obstructive apnea or qualifying AHI. The SpO2 results don't even enter into the binary thinking. Big mistake, because there is a problem you have not defined or solved.

[yrnkrn]

Patient was at or below 88% oximetry for 19% of the study time. The lowest saturation was 89%.

This is a contradiction, is there a graph you can scan & post?

[ardenum]

The average saturation was 75%. Patient was at or below 88% oximetry for 19% of the study time. The lowest saturation was 89%.

This whole sentence doesn't make any sense. Did you translate from a different language?

If not the doctor might have already had dementia.

[anbr3]

I know, So frustrating.  It wasn’t translated from another language (New Jersey doctor) and it was only a report so no graphs. I called the sleep study center and asked them to fax me the actual data today.

[anbr3]

got the detailed results.  When I look at the graph for SPO2, it seems to have stayed above 89 for the whole time and then flat lined to 50% at 6:00am (which i assume the thing fell off because the heart rate also stopped recording at that same time).  The report says the "lights on" time is 7:30am so I wonder if it averaged that hour and a half of flat line into it?  
I have no idea...can anyone make anything of this?

[yrnkrn]

The average saturation was 75%. Patient was at or below 88% oximetry for 19% of the study time. 

This takes into account the invalid 50% period... stupid...

The lowest saturation was 89%.

...while this ignores the invalid period.

Overall, the sleep report looks good!