Each subject’s immediate environment was continuously monitored
using a sound meter and infrared camera synchronized to the PSG.
In addition to background sound intensity, the magnitude, source, and
disruptive effect of each abrupt sound elevation above 10 dB(A)
(A-weighted decibel scale) was recorded. Each interaction between the
patient and a member of the critical care team, sleep technician, or
visitor that occurred during sleep was classified by type, and its effect
on sleep continuity was documented.