PSG questions - Can an RT or PSG specialist answer?

[Nodzy]

I am being railroaded by doctors again, and need answers from people who truly know.

1. What is the normal or accepted minimum duration for a valid baseline sleep study?

2. Would a very short 3.9-hour sleep study be considered absolutely valid as a baseline?

3. Would or could 1200mg per day of Gabapentin in the patient's system skew the baseline sleep study to the soft side?

4. Would or could 2400mg per day of Gabapentin in the patient's system skew the baseline sleep study to the soft side?

5. Would or could significant accumulation of Gabapentin in the patient’s system render a very short, 3.9-hour, baseline sleep study invalid?

6. Is carbon dioxide retention routinely monitored during the sleep study, or by blood test right after? Or is CO2 retention not considered an important factor in a PSG?

Nodzy

[6PtStar]

I can't answer most of them but #6 I can help. In my sleep study I wore a Pulse/Oxy recorder on my finger all night. It recorded my Oxygen level at intervals all night. Sleep study report listed the number of times and duration that it dipped below 88 (I think). At times it got down to low 70's.

[Slinky]

Pulse oximetry can NOT measure C02 in the bloodstream. In fact, carbon monoxide can elevate 02 saturation. I've been told that a pulse oximetry taken w/in a few minutes of smoking a cigarette can give an 02 saturation reading as much as 7% over the true 02 saturation level. i.e a reading of 97% when the actual 02 sats level is 84%

I can't swear about the minimum required hours of sleep needed for sleep evaluation but Medicare standards require at least two hours sleep out of 6 hours bedtime during a titration study to qualify for CPAP reimbursement if the apnea and hypopnea criteria are met.

During my first sleep evaluation around 1996-1998 at a local hospital sleep lab they did do a blood draw prior to sending me to bed for the night. The sleep evaluation at a stand alone sleep lab two years later they did not do a blood draw and my 2006 sleep evaluation, again at a stand alone sleep lab, did not do a blood draw. I don't remember if they required a urine sample that first sleep evaluation at the hospital sleep lab or not. Nor do I know if the hospital sleep lab still requires blood draws.

[Nodzy]

Pulse oximetry can NOT measure C02 in the bloodstream. In fact, carbon monoxide can elevate 02 saturation.

Slinky... Thanks for responding. I had learned about the O2 and CO2 things quite a while back. My newest doctor is hellbent on discrediting me, and hindering my care because I recently forced them to prescribe a BIPAP-Auto. Days later, I subsequently found in my medical file where I should have been on BIPAP since 2001, and wasn't. They are miffed that another of their glaring errors is in my spotlight.

In my sleep study I wore a Pulse/Oxy recorder on my finger all night. It recorded my Oxygen level at intervals all night. Sleep study report listed the number of times and duration that it dipped below 88 (I think). At times it got down to low 70's.

Thanks for responding. Yep, the O2 levels are always part of the sleep study, but why aren't CO2 levels? Since CO2 is often what causes or in a prime manner contributes to the absolute worst body pains and headaches for OSA/SDB sufferers. And in many untreated and ineffectively treated OSA/SDB sufferers the CO2 retention levels rise when sleeping.

Nodzy

[Slinky]

I believe the cheapest and most accurate way to detect CO2 levels is via an ABG. (arterial blood gases). This is not the most comfortable of blood draws. Nor the cheapest. I think there is another method, not as accurate, often used during surgery as it is more immediate, but it is an expensive proposition. I could be wrong on this so don't take it as gospel. Hopefully, one of our RTs or RPSGTs will see and respond to your post!!!!

[KansasRT]

In the sleep labs here in my area, they use what looks like a oxygen cannula. That measures C02 retention. The results show on a graph very similar to an oximeters results. I am not sure ( because it has been awhile, and if I remembered all the normal values I might forget something I really needed to know) but I think that normal is 30-45 mmHg. If you wore anything like a cannula they probably measured C02.

[Guest]

I'm a RRT, RPSGT and here are my answers:

1 - 6 hrs recording time with 2 hrs sleep is the MINIMUM we need.
2 - depends on the length of the study (see#1)
3 - not sure what you mean by "to the soft side". That much neurontin could conceivably make the pt a little sleepy if they haven't been taking the med for very long.
4 - See #3, but I've had pts close to that dose get valid results.
5 - need more info, but prolly not. Was the pt having nocturnal seizures?
6 - IMO, it's not that important. I can further clarify if you want, but zero labs out of 3 in my area measure CO2. The cannula that KansasRT spoke of was probably just a pressure transducer to measure breathing flow.

Hope it helps