The breathless problem of snoring

Anyone who shares a bed with a snorer will know how annoying the nasal noise can be. It’s a point of contention among roommates, campers and in marriages the world over. However, snoring is often accompanied by a much more sinister problem – obstructive sleep apnea (OSA), in which the upper airways can collapse during sleep. It is a known cause of tiredness among snorers but can also lead to high blood pressure and other serious health issues.

Now, researchers in Australia and Japan have used noise analysis to test audio recordings of 5,568 episodes of snoring to reveal that not only is the snoring sound complicated but it seems to follow a non-linear mathematical pattern, which is different from the linear sound pattern researchers had assumed it to follow previously. The discovery might one day help in monitoring chronic snoring to help diagnose the more serious problem of OSA.

Takahiro Emoto of the Institute of Technology and Science, at The University of Tokushima, and colleagues there and at The University of Queensland, in Brisbane, explain that while not everyone who snores suffers from OSA almost everyone with OSA snores. This means that the presence of snoring has not been considered a reliable indicator of OSA. A method of easily diagnosing the condition has therefore remained elusive.

Writing in the International Journal of Medical Engineering and Informatics, the team describes an approach to analyzing the sound of snoring that can reveal characteristic audio patterns that, in their preliminary investigation seem to correlate with a likely diagnosis of OSA. These patterns are entirely absent in the snoring of people without OSA. The team has carried out early tests of their analytical approach to snoring on a small group of just 27 volunteers, which suggests they might be able to reveal which snorers also suffer from OSA on the basis of this sound analysis. More work needs to be done before such a test can be validated for clinical use.

Research Blogging IconTakahiro Emoto, Udantha R. Abeyratne, Masatake Akutagawa, Yohsuke Kinouchi, & Shinsuke Konaka (2011). Testing the system non-linearity in snoring sound via neural networks Int. J. Medical Engineering and Informatics, 3 (3), 299-310

Detecting glaucoma before it blinds

Early detection and diagnosis of open angle glaucoma important so that treatment can be used in the early stages of the disease developing to prevent or avoid further vision loss. Writing in a forthcoming issue of the International Journal of Medical Engineering and Informatics, researchers in the US have analyzed and ranked the various risk factors for open angle glaucoma so that patients can be screened at an earlier stage if they are more likely to develop the condition.

Glaucoma is one of the main leading causes of blindness; it is a progressive and irreversible disease. Of the various forms of glaucoma, open angle glaucoma (OAG) is the most common and can cause the most damage. Unfortunately, unless a patient is undergoing regular screening from about the age of 40 years because of a family history, it is otherwise difficult to detect until substantial and irreversible vision loss has occurred. Glaucoma is the third leading cause of blindness worldwide and the second leading cause of blindness in the USA.

Now, Duo Zhou and colleagues at the University of Medicine and Dentistry of New Jersey, Newark, have used statistical collinearity analysis to evaluate risk factors for OAG, and logistic regression models to identify a minimum set of such risk factors for prognosis and diagnosis of the disease. Their study was based on more than 400 patients with subtle or severe vision problems who attended hospital. It reveals the relative risk of being a smoker, age, visual “field test” results, presence of a localized notch or thinning of the neuroretinal rim identified during standard eye examination, cup to disk ratio (a measure of restriction of the optic nerve at the back of the eye) and other factors.

The data are complex and separating out predictors from diagnostic factors was difficult, the team admits. However, they suggest that family history, medical history, current medications, geographic location, visual field test and ocular examination must all be considered in diagnosis and prognosis for OAG. They have excluded certain factors from the OAG prognosis: gender, race, family history of glaucoma, diabetes mellitus, hypercholesterolemia, thyroid disease, migraine, Reynaud’s disease and myopia as these have no direct effect on OAG development.

As revealed in the analyses, the odds of developing OAG will be increased by 91% with an increase in the Cup-to-Disc ratio of 0.1. Risk increases by 3% annually by age but decreases by 31% for every dB increase of mean deviation of Humphrey visual field. The odds of developing OAG will be 4.36 higher for patients with abnormal Humphrey visual filed overall test, 7.19 higher in patients with localized notch or thinning of the neuroretinal rim. Interestingly, patients with a smoking history seem to be less likely to develop OAG as compared to those with smoking history; although there are many smokers with OAG. Oddly, because of the location of the study, the team can also say that patients living in Atlantic/Quebec will be 73% less likely to develop OAG compared to their fellow Canadians in Ontario.

“Risk factors for open angle glaucoma – analyses using logistic regression” in Int. J. Medical Engineering and Informatics, 2011, 3, 203-222

Radiation boost for your hip replacement

A blast of gamma radiation could toughen up plastic prosthetic joints to make them strong enough to last for years, according to researchers in China writing in the current issue of the International Journal of Biomedical Engineering and Technology.

Whole joint replacement, such as hip and knee replacement, commonly use stainless steel, titanium alloys or ceramics to replace the damaged or diseased bone of the joint. Non-stick polymer or nylon is usually used to coat the artificial joint to simulate the cartilage. However, none of these materials are ideal as they produce debris within the body as the joint is used, which leads to inflammation, pain and other problems.

Now, Maoquan Xue of the Changzhou Institute of Light Industry Technology, has investigated the effect of adding ceramic particles and fibers to two experimental materials for coating prosthetic joints, UHMWPE (ultra-high-molecular-weight polyethylene) and PEEK (polyether ether ketone). Alone neither UHMWPE nor PEEK is suitable as a prosthetic cartilage materials because both crack and fracture with the kind of everyday stresses that a hip or knee joint would exert on them. The problem is that the long polymer chains within the material can readily propagate applied forces causing tiny fractures to grow quickly and the material to fail.

Xue has now demonstrated that by adding ceramic particles to the polymers and then blasting the composite with a short burst of gamma-radiation it is possible to break the main polymer chains without disrupting the overall structure of the artificial cartilage. There is then no way for microscopic fractures to be propagated throughout the material because there are no long stretches of polymer to carry the force from one point to the next. The resulting treated material is thus much tougher than the polymer alone and will not produce the problematic debris within a joint that might otherwise lead to inflammation and pain for the patient.

Xue adds that the treated composite materials might also be more biocompatible and so less likely to be rejected by the patient’s immune system on implantation. He suggests that the particular structure of the composites would also be receptive to addition of bone-generating cells, osteocytes or stem cells, that could help a prosthetic joint be incorporated more naturally into the body.

Xue, M. (2011). Research on polymer composites of replacement prostheses International Journal of Biomedical Engineering and Technology, 7 (1) DOI: 10.1504/IJBET.2011.042495