because of costs, more and more studies for "sleep apnea" are attempted as split-night studies when there is early evidence for osa. (note that both types of study, with and without a cpap mask, are still polysomnograms.) when the cpap mask is worn, however, the flow-measurement lead in the patient's nose is removed. instead, the cpap machine relays all flow-measurement data to the computer. the below report is an example report which might be produced from a split night study: