Phrenic nerve stimulation causes contraction of a patient’s diaphragm that creates negative pressure within the chest cavity in a manner similar to that of natural breathing. The stimulation is adjusted to make it imperceptible to patients, and stimulation does not occur when a patient is standing or sitting, only when lying down. “With positive airway pressure in patients with advanced heart failure you reduce venous return, and when a patient’s heart is sick and depends on preload this can hurt the patient. Phrenic nerve stimulation does the opposite. It contracts the diaphragm and creates negative pressure, so it anything it facilitates venous return,” she explained.
The trial, run at 31 centers, mostly in the United States with the others in Europe, enrolled patients with moderate to severe central sleep apnea with an average apnea-hypopnea index of 45 episodes per hour while sleeping. The average age was 65 years, about 90% of the patients were men, and average body mass index was 31 kg/m2.
In addition to the primary efficacy endpoint of reduced apnea-hypopnea index, the patients on active treatment also showed statistically significant reductions compared with baseline in central apnea episodes and in daytime sleepiness measured on the Epworth Sleepiness Scale and an improvement in the patients’ global assessment of their condition. The changes did not occur in the control patients. In the treated patients central apnea episodes fell from an average of 32 episodes per hour at baseline to an average of 6 central episodes an hour after 6 months on treatment.
Dr. Costanzo is a consultant to and has received research support from Respicardia, the company developing the tested phrenic-nerve stimulation device. Dr. Jessup had no disclosures.
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