ICFO develops medical optics for sleep apnea

By March 20, 2018ICFO

ICFO researchers develop a non-invasive, point-of-care optical device to study this sleeping disorder and its treatment.

Millions of people suffer from Obstructive Sleep Apnea (OSA), a sleeping disorder that occurs when a person’s breathing is interrupted regularly during sleep. OSA is the most common type of sleep apnea syndrome and it occurs when the soft tissue in the back of the throat that collapses during sleep blocks the passage of air. People with untreated sleep apnea stop breathing repeatedly during their sleep, sometimes hundreds of times. This means that the brain — and the rest of the body — may not get enough oxygen, and, over time, chronic OSA leads to permanent alterations in brain circulation with the risk of causing severe health problems including high blood pressure, heart failure or attacks, and even strokes, among others.

The mechanisms responsible for this disorder remain partly unknown. However, what is clear is that OSA alters the basic control mechanisms for regulating cerebral blood flow (CBF) by decreasing resting CBF, impairing autoregulation and reducing cerebrovascular reserve capacity. A diminished cerebrovascular reactivity, an alteration to normal cerebrovascular control, interferes with brain function and renders the brain more vulnerable to ischemic events because the brain tissue is very sensitive to hypoxic damage and rapid reperfusion. There are several techniques for monitoring the state of cerebral vasoreactivity (CVR) in patients. However, many of these techniques are expensive, have limited availability and some are invasive and require exposure to ionizing radiation. For example, Transcranial Doppler ultrasound (TCD) is one of these implemented techniques, although its accuracy is sometimes questioned and it can only insonate the major cerebral arteries.

In a recent study published in PLOS ONE, researchers Clara Gregori-Pla , Gianluca Cotta, Igor Blanco, Peyman Zirak, Martina Giovannella, led by ICREA Prof. at ICFO Turgut Durduran have reported on the development of a non-invasive, portable optical device, capable of continuously monitoring cerebral blood flow of patients with OSA at the patient bedside. The study was inspired and designed by a collaboration with the Department of Respiratory Medicine at the Hospital de la Santa Creu i Sant Pau in Barcelona led by Dr. Mercedes Mayos and her team members Anna Mola and Ana Fortuna.

The team of researchers implemented DCS to study cerebral hemodynamic responses to a head-of-bed position change in a group of patients with OSA with different levels of severity, and compared their cerebral hemodynamics to a control group of healthy subjects. The device, which uses Diffuse Correlation Spectroscopy (DCS), measured CBF at a microvascular level, a major improvement compared to TCD that can only measure at a macro-vascular level. They have shown that the cerebral vasoreactivity (CVR) is impaired in patients suffering from moderate and severe OSA, possibly indicating an increased risk of cerebrovascular accidents. They have also found that cerebral vasoreactivity improved with two year treatment of positive airway pressure (CPAP) treatment in a small group of highly compliant patients, suggesting that cerebrovascular impairment may be reversible, at least in part, with the treatment.

The results of this study show a promising future for non-invasive optical devices as continuous monitoring devices that could make a difference for clinicians allowing them to adjust in real-time the type of treatment they are delivering to patients in order to radically improve their outcome.

More information on the ICFO website.

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