title: The influence of APACHE II score on the average noise level in an intensive care unit: an observational study.
abstract: BACKGROUND
  Noise levels in hospitals, especially in intensive care units (ICUs) are known to be high, potentially affecting not only the patients' well-being but also their clinical outcomes. In an observational study, we made a long-term measurement of noise levels in an ICU, and investigated the influence of various factors on the noise level, including the acute physiology and chronic health evaluation II (APACHE II) score.
  
  
  METHODS
  The average noise level was continuously measured for three months in all (eight) patient rooms in an ICU, while the patient data were also registered, including the APACHE II score. The 24-hour trend of the noise level was obtained for the patients of length-of-stay (LOS) ≥1 day, which was compared to the timeline of the ICU routine events. For the patients with LOS ≥4 days, the average noise levels in the first four days were analyzed, and regression models were established using the stepwise search method based on the Akaike information criterion.
  
  
  RESULTS
  Features identified in the 24-hour trends (n = 55) agreed well with the daily routine events in the ICU, where regular check-ups raised the 10-minute average noise level by 2~3 dBA from the surrounding values at night, and the staff shift changes consistently increased the noise level by 3~5 dBA. When analyzed in alignment with the patient's admission (n=22), the daytime acoustic condition improved from Day 1 to 2, but worsened from Day 2 to 4, most likely in relation to the various phases of patient's recovery. Regression analysis showed that the APACHE II score, room location, gender, day of week and the ICU admission type could explain more than 50% of the variance in the daily average noise level, LAeq,24h. Where these factors were argued to have causal relations to LAeq,24h, the APACHE II score was found to be most strongly correlated: LAeq,24h increased by 1.3~1.5 dB when the APACHE II score increased by 10 points.
  
  
  CONCLUSIONS
  Patient's initial health condition is one important factor that influences the acoustic environment in an ICU, which needs to be considered in observational and interventional studies where the noise in healthcare environments is the subject of investigation.
authors: Brain, Cognition & Perception Group, Philips Research, High Tech Campus 36, AE Eindhoven, 5656 The Netherlands.
authors: Munhum
authors: M
authors: Park
authors: Department of Intensive Care Medicine, St. Elisabeth Hospital, P.O. Box 90151, LC Tilburg, 5000 The Netherlands.
authors: Pieter
authors: P
authors: Vos
authors: Brain, Cognition & Perception Group, Philips Research, High Tech Campus 36, AE Eindhoven, 5656 The Netherlands.
authors: Björn N S
authors: BN
authors: Vlaskamp
authors: Brain, Cognition & Perception Group, Philips Research, High Tech Campus 36, AE Eindhoven, 5656 The Netherlands ; Human-Technology Interaction Group, Technische Universiteit Eindhoven, P.O. Box 513, MB Eindhoven, 5600 The Netherlands.
authors: Armin
authors: A
authors: Kohlrausch
authors: Department of Intensive Care Medicine, St. Elisabeth Hospital, P.O. Box 90151, LC Tilburg, 5000 The Netherlands.
authors: Annemarie W
authors: AW
authors: Oldenbeuving
mesh_terms: D018806:APACHE; D000162:Acoustics; D004781:Environmental Exposure / Q000009:adverse effects / Q000032:analysis; D006801:Humans; D007362:Intensive Care Units; D007902:Length of Stay; D009623:Noise, Occupational; D012044:Regression Analysis