Identifying determinants of noise in a medical intensive care unit

Abstract

Continuous and intermittent exposure to noise elevates stress, increases blood pressure, and disrupts sleep among patients in hospital intensive care units. The purpose of this study was to determine the effectiveness of a behavior-based intervention to reduce noise and to identify determinants of noise in a medical intensive care unit. Staff were trained for 6 weeks to reduce noise during their activities in an effort to keep noise levels below 55 dBA during the day and below 50 dBA at night. One-min noise levels were logged continuously in patient rooms 8 weeks before and after the intervention. Noise levels were compared by room position, occupancy status, and time of day. Noise levels from flagged days (>60 dBA for >10 hr) were correlated with activity logs. The intervention was ineffective, with noise frequently exceeding project goals during the day and night. Noise levels were higher in rooms with the oldest heating, ventilation, and air-conditioning system, even when patient rooms were unoccupied. Of the flagged days, the odds of noise over 60 dBA occurring was 5.3 dBA higher when high-flow respiratory support devices were in use compared to times with low-flow devices in use (OR = 5.3, 95% CI = 5.0-5.5). General sources, like the heating, ventilation, and air-conditioning system, contribute to high baseline noise and high-volume (>10 L/min) respiratory-support devices generate additional high noise (>60 dBA) in Intensive Care Unit patient rooms. This work suggests that engineering controls (e.g., ventilation changes or equipment shielding) may be more effective in reducing noise in hospital intensive care units than behavior modification alone.

Keywords: Hospital; quality improvement; respiratory device; sound; ventilation.

Figure 1.

Layout of the MICU with Pods 1–5 numbered. Sound Level Meters were placed in a near (N) room and a far (F) room for each of the four included pods. Central nurses’ stations are shown as stars.

Figure 2.

Example of the weekly feedback provided to MICU staff during the intervention. Each week the project leaders generated summary data and figures using a custom web application. Messages incorporating these data were disseminated via email and posted at each nursing station, and frequently referenced by project leaders during weekly bedside rounds. The gap in the sound data tracing indicates the instrumented rooms were unoccupied during this time. Sound levels shown are measured in A-weighted decibels.

Figure 3.

Boxplot comparing hourly sound equivalent levels (L_eq-H) in each pod during occupied (O) and unoccupied (U) time periods.

Figure 4.

One-min noise measurements over full days with medical interventions in use. Time periods shown in Panels B, D, and F were identified as having >10 hr of noise >60 dBA. Panels A, C, and E show the same rooms one day prior as a baseline comparison. Interventions include oxygen delivery systems such as a face mask (FM), nasal cannula (NC), CPAP, and BIPAP device which are shown in liters per minute (L/min).