Abstract: An apnea monitoring system which utilizes a portable data storage cartridge for storing the monitored events and waveforms of a patient's respiration, ECG and the like. The cartridge is easily carried or mailed to a remote location and connected to a transfer unit to provide a cost-effective and time-efficient method of transferring the stored information to a computer for displaying selected events and waveforms. The monitor includes provisions for indicating the available memory space on the cartridge, and the cartridge is replaceable to provide an unlimited amount of memory space and permit continued use of the monitor during transferring of information to a computer.