A Novel Constant Bias Flow Rate CPAP Mask for OSA Therapy Treatments

Abstract

Abstract Continuous positive airway pressure (CPAP) therapy is considered the most effective treatment for patients with Obstructive Sleep Apnea (OSA) symptom. A CPAP mask is the interface between the patient and the CPAP humidifier, which contains a series of orifice to circulate the air and ensure that the expired carbon dioxide from the patient's breathing is not rebreathed. The flow through those orifices is called bias flow. For the existing CPAP mask, this bias flow rate increases as the CPAP pressure increases. This raised bias flow rate usually causes a bigger pressure swing inside the mask when the patient is breathing, which is unfavorable for OSA therapy due to the much bigger breathing load required. However, a minimum bias flow rate needs to be maintained inside the mask in order to keep carbon dioxide concentration low. Therefore, this paper introduces a novel mask that can produce a relatively constant bias flow rate (CBFR) over a CPAP range of 0-20cm H2O. Dynamic response tests have proved that this CBFR mask can constrict the mask pressure swing by an order of two so as to offer better comfort for OSA patients.