to whoever is paying for the study. The split-night study has these disadvantages: There is less time to make a diagnosis of OSA (Medicare in the US requires a minimum of 2 hours of diagnosis time before the mask can be applied); and There is less time to assure an adequate CPAP titration. If the titration begins with only a few hours of sleep left, the remaining time may not assure a proper CPAP titration, and the patient may still have to return to the lab. 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: See also Polysomnographic technician Respiratory monitoring Sleep disorder Sleep medicine Sleep study References Further reading Iber C, Ancoli-Israel S, Chesson A, and Quan SF for the American Academy of Sleep Medicine. The AASM Manual for the Scoring of Sleep and Associated Events: Rules, Terminology and Technical Specifications, 1st ed.: Westchester, Illinois: American Academy of Sleep Medicine, 2007. External links Practical guide to Polysomnography What is Polysomnography What is a Sleep Study for Sleep Apnea? Polysomnography by Carmel Armon, on Medscape Reference Diagnostic neurology Diagnostic pulmonology Sleep medicine