Airway Muscle Activation on Sleep-disordered Breathing Events

Sleep Apnea

The standard for treatment for people suffering from obstructive sleep apnea (OSA) syndrome involves the use of Continuous, or Automatic Positive Airway Pressure (CPAP, APAP) machines, which work by delivering air via tubing and mask to a patient at pressures of up to 20cmH2O. This increased pressure is meant to stabilize the airway to reduce obstruction events. APAP machines are generally more effective and more comfortable for patients than CPAP machines because these devices automatically adjust pressure to treat an apnea. As a result of the high rate of patient dissatisfaction with conventional PAP therapy, alternative treatments for sleep apnea have been developed. One therapeutic target for OSA is stimulation of the genioglossus muscle, a phasic respiratory muscle important in maintaining upper airway patency. Recently, it has been shown that genioglossus reflex responses can be achieved through the application of negative pressure pulses as well as changes in airway pressure. These studies focused on activating pressure-sensitive mechanoreceptors within the upper airway known to contribute to genioglossus activity. Together, these studies have demonstrated that both brief pulses of negative airway pressure and changes in airway pressure are capable of eliciting genioglossus reflex responses. The goal of this interventional study is to evaluate the potential of airway muscle activation on sleep-disordered breathing during sleep therapy by applying brief maneuvers of air pressure using existing pressure and flow sensors in conventional CPAP machines.

Patients recruited for the study will undergo one overnight study period which will take place at the sleep clinic (Sleep Disorders Clinic, QEII Abbie J. Lane Memorial Building). Treatment will be delivered using a positive airway pressure (PAP) device with an Investigational Testing Authorization (ITA) from Health Canada (HC). This medical device consists of a commercially available PAP device which has been integrated with a feature to communicate with a computer hosting the software via USB. The custom software has been developed to allow an operator to specify the pressure routine to be applied using a laptop computer, which then controls the CPAP and applies the routine. The patient's personal PAP therapy settings will be transferred to this device so that the the only modified part of their therapy will be the brief pressure maneuvers. Standard PSG which typically consists of EEG, electrooculography, surface EMG, and electrocardiogram measurements as well as a submental needle EMG will be used to measure genioglossal activity. EMG needle insertion will be performed by an Otolaryngologist. Prior to insertion of the EMG needle, patients will be offered local anesthetic 1-2% lidocaine. Natus coated stainless steel wires (0.38 mm in diameter) will be inserted into the genioglossus muscle submentally using a 28-gauge TECA® Elite Disposable Monopolar Needle. Tegaderm tape will be used to adhere wires to the skin. Participants will be asked to perform tongue protrusions (pushing the tongue as hard and fast as possible against the top two incisor teeth) and several large swallows to confirm correct placement of the electrode and to measure maximal genioglossal activity. The brief air pressure maneuvers will be applied both before falling asleep and while asleep to compare muscle activation in awake and asleep conditions as described in the test plan below: There are 3 stages to the test, described below. Stage 1: Subject is awake. To begin, baseline measurements will be taken while the subject is awake. Genioglossus activity with maximal tongue protrusion will be measured as well as the response to 1 to 2 pressure routines. Stage 2: Subject is asleep, manual control. Once the subject is sleeping, the operator will observe the PSG recording and determine sleep stage and respiratory phase (inspiration, expiration, between breaths). Each of the test routines will be performed for each sleep stage and each respiratory phase. If the operator notices an apnea occurring, one of the routines will be applied. The shapes of the pressure routines are illustrated below, and the table corresponds to the test parameters for each test routine to be applied. If significant arousal is being caused as noted on the EEG, higher levels of pressure amplitudes of the routines may be aborted. Stage 3: Subject is asleep, automatic control. When all manual tests are complete, an automatic mode will be engaged for the remainder of the night. During this mode, a previously developed and trialled AI model will be used to predict if an obstructive apnea is upcoming. The operator will input which routine to test, and the routine will be automatically applied when a prediction occurs. There will be a minimum of 60 seconds between pressure routine applications.

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