AHI and Fluid Retention

-SWS wrote:Scientists are considering the possibility that soft-tissue fluid displacement or "loading" just may serve as a variable contributor to sleep apnea:

American Journal of Respiratory and Critical Care Medicine, December 15, 2006 wrote:Fluid displacement may contribute to sleep apnea

NEW YORK (Reuters Health) - When fluid in tissues is displaced from the lower body into the upper body, the circumference of the neck grows, which may hinder the flow of air, Canadian researchers report. These findings may help explain why the prevalence of obstructive sleep apnea (OSA) is increased in patients with diseases characterized by "fluid overload," like heart failure and kidney failure, for example.

People with sleep apnea stop breathing temporarily and repeatedly while asleep causing them to gasp for breath. Although obesity and a thick neck are known risk factors for the disorder, they account for only about one third of variability in the apnea-hypopnea index -- a measure of the frequency of slow or stopped breathing episodes at night.

Dr. T. Douglas Bradley, from the Toronto General Hospital, and his team theorized that fluid accumulation in soft tissues in the neck might cause narrowing or blockage of the pharynx -- the tube that connects the mouth and nasal passages with the esophagus.

Experiments in 11 healthy non-obese subjects with no symptoms suggesting OSA support this line of thinking.


In order to measure airflow resistance, investigators inserted two open catheters, one into the nose and the other advanced beyond the base of the tongue.

To force fluid redistribution from the lower to the upper body, to simulate effects in patients with fluid overload, the subjects wore medical anti-shock trousers that exert pressure on the legs when inflated.

In the control condition, the subjects just rested lying down face up with the trousers deflated while measurements were made. During the test condition, the trousers were inflated causing displacement of fluid.

While lower leg pressure was increased, airflow resistance rose by a significant 40 percent over at 1 minute and a full 102 percent at 5 minutes. Neck circumference also increased significantly from baseline at these time points.

The investigators say that the change in neck circumference is in keeping with displacement of fluid into nearby blood vessels and soft tissues as a cause of the increase in breathing difficulties.

They note that in patients with fluid overload, when lying down, excess fluid in the lower extremities is displaced, and conclude that this may increase obstruction of the pharynx in patients predisposed to obstructive sleep apnea.

SOURCE: American Journal of Respiratory and Critical Care Medicine, December 15, 2006

Obstructive apnea patients with renal, cardiac, or even general water-weight issues may find the above research particularly interesting. Patients with unexplained SDB variability may find this avenue of research interesting as well.

Alisha wrote:I find this very interesting and will add "Degree of Swelling/Distension" to my daily chart which I am using to try to determine what causes/worsens/helps/works to lead to a path to a healthier me. I have read that some believe xpap treatment causes or worsens edema, and, if I understand this article, it indicates that edema can cause or worsen sleep apnea.

This is of particular interest to me because of undiagnosed edema, i.e., after being examined by my family doctor, a Heart Specialist, Pulmonary Specialist, ENT, and taking test after test, it has not been determined what is causing the edema. I even have a packet of fluid on the left side just above the collar bone, which is puffier some days but never flattens out.

I have read the threads on this subject in cpaptalk.com, but if any of you know of any more articles that relate to the correlation of sleep apnea and edema, I'd like to read them.

This is a wonderful site and posters share a wealth of information. For this I am grateful.

krousseau wrote:As the simplest application of that research - recliners may help if that is a part of a person's OSA problem

NightHawkeye wrote: <snip>

Thanks for the link on edema, -SWS. It's along the lines of what I read some weeks ago, in the Wall Street Journal IIRC. Like the test subjects in the article, I'm not overweight. I do, however, experience slight edema in my feet, often visible at bedtime, and my apnea tends to occur in the latter hours of sleep after fluid has had time to redistribute. For years I slept with the head of the bed elevated slightly. That was followed by sleeping sitting up for a few more years until starting xPAP therapy. Even now, particularly when aerophagia gets bad, I'll revert to sleeping the remainder of the night sitting up in bed with the machine OFF.

At least part of my apnea appears to be caused by the same TMJ issues which prevented me from being able to wear a full-face mask because at some point increased pressure pushed my lower jaw back, thereby increasing my apnea. However, it also appears that part of my apnea correlates with the edema.