Sleep apnea can negatively impact health and well-being, but treatments are limited to poorly tolerated positive pressure masks (CPAP) and, in the worst cases, surgery. However, in a recent trial, a nasal spray showed promise in treating this most common form of sleep-disordered breathing.
Obstructive sleep apnea (OSA) refers to the collapse of the upper airway during sleep, reducing or completely blocking airflow. The main causes are damage to the anatomy of the larynx and insufficient muscle function during sleep. This can lead to decreased oxygen intake and sleep arousal, which can have negative health and safety consequences, including daytime fatigue, difficulty concentrating, and high blood pressure.
Treatments for OSA are limited. The first-line treatment is the use of a continuous positive airway pressure (CPAP) machine to prevent airway collapse. Unfortunately, about half of the people who use CPAP machines cannot tolerate them. In this case, surgery may be considered to repair the anatomic obstruction.
Researchers at Australia's Flinders University conducted a small trial using a nasal spray to treat OSA and found it worked well.
"Obstructive sleep apnea (OSA) is a sleep disorder in which the muscles in the back of the throat relax, narrowing or collapsing the upper airway, limiting oxygen intake and causing the patient to wake up repeatedly throughout the night," said Danny Eckert, a professor at Flinders University's School of Medicine and Public Health and a co-author of the study. "It has been linked to a variety of conditions including cardiovascular disease, stroke, obesity, diabetes, anxiety and depression."
Researchers tested a nasal spray that delivers potassium channel blockers topically to the airway muscles to see if it reduces the severity of OSA symptoms.
"Potassium channel blockers are a class of drugs that block potassium channels in the central nervous system," said Ammar Osman, the study's first and corresponding author. "When used in a nasal spray, blockers have the potential to increase the activity of the muscles that keep the upper airways open, reducing the likelihood of the throat collapsing during sleep."
Ten patients with OSA (five women, five men; average age, 55 years) were randomized to receive one of three treatments: a placebo nasal spray, a nasal spray containing a potassium channel blocker, or a blocker nasal spray but with breathing restricted to the "nasal cavity," using oral tape or a chin strap. On average, participants were obese, had severe OSA, were not excessively sleepy, and did not suffer from insomnia.
Participants completed three overnight sleep studies, with about a week between studies. The researchers found that seven of 10 study participants experienced a slight reduction in OSA severity when the nasal spray was combined with unrestricted breathing compared with the placebo group. Total oxygen saturation was higher with unrestricted breathing nasal spray therapy compared with placebo. Morning blood pressure measurements were also lower with unrestricted breathing nasal spray therapy.
Subjects who were restricted to breathing through the nose did not show improvement despite receiving potassium channel blockers via nasal spray. Instead, the researchers found that respiratory and upper airway muscle function tended to worsen when using a chin strap.
"We found that nasal spray application of the potassium channel blockers we tested was safe and well-tolerated," Osman said. "Those who experienced physiologic improvements in airway function during sleep also experienced between 25% and 45% reductions in measures of OSA severity, including improvements in blood oxygen levels and lower blood pressure the next day."
The findings provide a new way to expand treatment options for OSA patients.
"These insights provide potential avenues for [developing] new treatment options for patients with OSA who cannot tolerate CPAP machines and/or upper airway surgery, and for those who want alternatives to existing therapies," Eckert said. "Currently, there are no approved drugs to treat OSA, but through these findings and future research, we are getting closer to developing effective new drugs that are safe, easy to use, and effective."
The researchers plan to conduct a larger study to further explore their initial findings.
The study was published in the journal Heart and Circulatory Physiology.