Sleep fragmentation and deprivation in critically ill patients – Is noise a factor?

Abstract

High noise levels disrupt quality and reduce quantity of sleep. Excessive noise may thereby increase the risk of delirium, resulting in increased Medical Intensive Care Unit (MICU) length of stay and possibly increased mortality. The study was conducted in a 24 bed tertiary care academic MICU where Physicians, Nurses, and other allied health care providers were involved. A pre-post intervention design methodology was used for this study. MICU staff responded to an online survey assessing baseline perceptions about patients’ sleep quality and quantity. Data was also gathered on providers’ perception of noise levels in the MICU and factors contributing to high noise levels. In addition, baseline measurements of noise levels (in decibels (dBA) were obtained using a dosimeter. Decibel levels for different noise sources such as ventilator alarms, infusion pumps, telephones, pagers and staff conversations were measured. Multi-pronged interventions involving environmental changes (reducing alarm sound levels, reducing telephone ringer levels etc.), provider education and patient level interventions (use of sleep enhancement order sets, closing room doors at night time to reduce noise exposure) were implemented. A repeat survey was performed post-intervention to re-assess provider perceptions regarding patients’ sleep and noise levels in the MICU. Also, noise levels were re-measured with the dosimeter. Baseline survey data revealed that 88% of the MICU staff agreed that patients slept poorly in the MICU, 69% felt that on an average our patients slept for less than 4 h per day, and more than half (52%) of the interruptions to sleep were secondary to high noise levels. Noise level measurements revealed that alarms (64 dBA), pagers (64 dBA) and staff conversations (60 dBA) were the most significant contributors to noise. Post-intervention, we noted an increase in the proportion of respondents (26% vs 35% p = 0.07) who felt that our patients slept more than 5 h per day. Also, post- intervention, staff continued to perceive that greater than 50% of the interruptions to sleep were secondary to noise. Although mean noise levels were not significantly different pre and post intervention (54.2 dBA vs 53.8 dBA), there was a significant reduction in the number of episodes of peak noise level elevations above 60 dBA (1735 vs 1289, p = <0.00). High noise level in the MICU is a contributing factor to patient’s sleep fragmentation and deprivation in the ICU. Reducing mean and peak noise levels in an ICU proved difficult, and gains may be difficult to sustain over time. In addition to noise reduction, efforts to modify the patient experience of noise, such as provision of hearing protection or white noise, may be more fruitful in reducing influence on sleep. Medical Intensive Care Unit staff at Mayo Clinic, Rochester, MN.