AUTOMATIC-CONTROL OF AIRWAY PRESSURE FOR TREATMENT OF OBSTRUCTIVE SLEEP-APNEA

Obstructive sleep apnea (OSA) occurs when airflow ceases because of ph aryngeal wall collapse in sleep, Repeated apneic events results in the development of a pathological condition called OSA syndrome, We descr ibe the methodology and design of a prosthetic device, named automatic positive airway pressure (APAP), for treatment of this syndrome, APAP applies a stream of air via a nasal mask at an initial pressure selec ted by the patient. By sensing specific pressure characteristics of ai r flow immediately preceding pharyngeal wall collapse, the APAP device automatically raises the applied pressure to maintain a patent upper airway and thus prevent apnea, Conversely, when such conditions are ab sent, pressure is lowered step wise until a preselected minimum pressu re is reached, Performance evaluation of the APAP system in five OSA p atients and five normal (asymptomatic for sleep apnea) subjects reveal ed that it effectively treated OSA syndrome, It lowered the apnea-hypo pnea index without disturbing sleep and resulted in a lower mean airwa y pressure compared to the traditional continuous positive airway pres sure (CPAP) therapy, The results also show that the pressure needed to prevent OSA varied significantly throughout the night, For OSA syndro me patients, this pressure ranged from 3 to 18 cm H2O, The mean airway pressure for these patients had a sample average of 6.80 cm H2O and a standard deviation of 3.17 cm H2O, In normal subjects, the device did not raise pressure except in response to Pharyngeal Wall Vibration ev ents.