Dr. Smith: PLMD often accompanies sleep disordered breathing. However, since his AHI and SpO2 are relatively normal, these movements do not appear to be related to his breathing at all. One movement every minute of the night is very excessive, and since he is also aroused out of normal sleep architecture every 2 minutes, I have to think this is affecting his sleep, even though he does not admit to sleepiness.

I have picked up early Parkinsons in a patient like this, so I am a bit sensitive to the issue, and would discuss a referral to rule this out if he was may patient. As the sleep MD is a pulmonologist, and not a neurologist, he would be less likely to make the connection. However, hopefully, I am just an alarmist, and the patient has little to worry about. Maybe you can make him an appliance for his snoring, then get him retested to see if the PLMD has improved. Let me know how it goes!

Dr. Smith: I read 2 or 3 of these every day, and rarely do they resemble each other. However, I can help with some of the acronyms and numbers even without seeing the study.

AHI: Stands for the Apnea-Hypopnea Index. Very simply, this means the number of times you stop (or significantly hinder) breathing for at least 10 seconds every hour. These “events” can be due to an obstruction or due to your brain’s respiratory center being a bit lazy.

RDI: This stands for Respiratory Disturbance Index. There is some controversy here, but generally this number is derived from adding the RERAs to the AHI. So, the RDI should always be higher than the AHI.

RERA: Respiratory Effort Related Arousal. These do not need to last 10 seconds, but they are related to an obstructed breathing effort that created a sleep arousal. If you have many RERAs but a low AHI, this is called Upper Airway Resistance Syndrome (UARS)

ODI: Oxygen Desaturation Index. This is generally considered to be the number of times per hour that your oxygen became desaturated at least 4%. This usually occurs concurrently with or shortly after a respiratory (breathing) interruption, or apneic event.

If you (or anyone) would like to know more about the numbers or acronyms on your sleep study, just let me know. There are far too many possiblities to list them here.

Dr. Dmith:
1. From Sleep and Breathing (When we remove obstructions and anatomically reorient the mandible, we can be surprised at the benefits)

The aim of the present study was to investigate the effect of a mandibular advancement device (MAD) for the treatment of sleep apnea (SA) on plasma brain natriuretic peptide (BNP), left ventricular ejection fraction (LVEF), and health-related qualify of life (HRQL) in patients with mild to moderate stable congestive heart failure (CHF). Seventeen male patients aged 68.4±5.5 with an apnea–hypopnea index (AHI) 10 were equipped with an individually fitted MAD. SA was evaluated using a portable respiratory multirecording system before and after the initiation of treatment. Eleven patients completed follow-up and were evaluated after 6 months of treatment. The AHI reduced from 25.4±10.3 to 16.5±10.0 (p=0.033) compared to baseline and mean plasma BNP levels decreased from 195.8±180.5 pg/ml to 148.1±139.9pg/ml (p=0.035). SA-related symptoms, e.g., excessive daytime sleepiness, were also reduced (p=0.003). LVEF and HRQL were unchanged. We conclude that SA treatment with a MAD on patients with mild to moderate stable CHF appears to result in the reduction of plasma BNP levels. Further studies to investigate if the observed reduction in BNP concentrations also result in improved prognosis are warranted.

2. From articles like this one, it becomes clear that a) Obstructions that create a decrease in respiratory motor output will b) decrease respiratory drive, leading to c) CSA. Therefore, anything that removes obstructions, such as a MAD, can improve CSA.

3. Additionally, OSA leads to arousals, which leads to hyperventilation, which leads to hypocapnia, which leads to a decreased respiratory drive, which leads to CSA. So, control OSA with a MAD, and you can lessen the likelihood of CSA manifestation.

Dr. Smith: RDI stands for the respiratory disturbance index, which includes apneas, hypopneas and RERAs. If the RDI is high and the AHI is low, this indicates Upper Airway Resistance Syndrome, and most sleep centers will not report this on studies. Oral appliances are great for this condition.
AHI stands for the Apnea-Hypopnea Index, and contains apneas and hypopneas. Put simply, although not exactly correct, this is the number of times you stop breathing for at least 10 seconds each hour.
ODI is the desaturation index, and it means the number of times each hour your hemoglobin (storage facility and transporter of O2 in your blood) lets go of at least 4% of the O2 it contains. This is what you measure with your pulse oximeters you use when sedating patients.