An investigation of light and sound levels on intensive care units in China.

Background: The intensive care units' (ICU) environment is considered clinically relevant sources of stress for patients.

Objectives: To measure 24-h sound and light levels in 7 ICUs in China [four medical (MICU), two surgical (SICU) and one coronary (CCU) ICUs] and to identify the main sources related to increased sound levels.

Methods: Sound pressure and light levels were monitored for specific times over a 24-h period using a digital sound level meter and a light detector in 7 ICUs. Sound pressure levels were measured for 20min every hour. The main events at the time of peak noise levels were recorded. Light levels were measured every 2h at three locations for each ICU: near a window, in the centre of the room, at eye level of a patient receiving assisted ventilation.

Results: The mean value of 24-h sound pressure levels exceeded 50dB(A) in all ICUs, ranging from 56.5 to 70.1dB(A). The SICUs and CCU had higher sound pressure readings from 0700h to 1600h, compared to the MICUs where the sound pressure readings reflected less variability across the 24-h period. Marked differences were observed in luminance levels among various ICUs and also across the 24-h period for all three locations. The mean highest level of nocturnal luminance at eye level of patients receiving assisted ventilation ranged from 15 to 489lx before midnight (1800-2400h) and 10 to 239lx after midnight (2401-0759h).

Conclusions: High sound pressure levels are prevalent throughout 24h in the ICUs, especially in the SICU. Many of the readings exceeded international standards. Peak sound pressure levels were related primarily to staff activities and the alarm sounds of machines. ICU patients are exposed to high levels of artificial light continuously throughout the day and night.