@laureenm The numbers you cite are actually for an hour. This means that you have that many events per hour of record when you use the machine. When using the machine, and it is properly programmed for your individual needs, your therapy, it should be less than five (5) events per hour. Above 5 is deemed to be unsuccessfully treated, below 5 events per hour is deemed to be treated. The unit of measurement is known as the 'apnea-hypopnea index', or simply AHI. So, untreated, your severe apnea has an AHI of 55/hr, and treated you have 2-3/hr.