The way the cpap or bipap machines measure you ahi is they have a algorithm that measures your exhalation. Pinto vl sharma s. How To Make The Most Of Your Bedtime With Images What Is Sleep There may be a choking or snorting sound as breathing resumes. How is sleep apnea measured . The apnea hypopnea index ahi is a scale that tells whether you have a sleep disorder called apnea and if so how serious it is. The three types of sleep apnea are central apnea obstructive apnea and a mixture of central and obstructive apnea. J clin sleep med. Obstructive sleep apnea is caused by the collapse of the airway during sleep. Impaired vasodilator responses in obstructive sleep apnea are improved with continuous positive airway pressure therapy. Ueno k kasai t brewer g et al. So when the machine blower sends a signal for air and then checks to see that you are giving it a return flow. Continuous positive airway pressure cpap. Sleep apnea is when you stop breathing for 10 seconds...