Validating Acoustic Guidelines for Healthcare Facilities

By Jo M. Solet, Ph.D.; Orfeu M. Buxton, Ph.D.; Jeffrey M. Ellenbogen, M.D.; Wei Wang, Ph.D.; and Andy Carballiera, BM

Published by The Center for Health Design, 2010

EXECUTIVE SUMMARY

National healthcare quality surveys have found that noise in hospitals is an urgent concern. The purpose of this study was to demonstrate the impact of hospital noise on all stages of human sleep by developing sleep arousal probability threshold curves for specific hospital-based sounds. Most hospital sound sources were recorded on-site corresponding to specific categories identified in the American Institute of Architects’ Draft Interim Guideline on Sound and Vibration in Healthcare Facilities. Fourteen sounds were chosen and calibrated for dynamic presentation. They were transmitted through an array of speakers positioned in a hospital sleep laboratory room. Sounds were delivered in rising 5 decibel-step exposures from 40 to 70 dB(A), with steady 32 dB(A) night background levels from air-handling equipment.

Noise-related sleep arousals were recorded and quantified using current American Association of Sleep Medicine EEG criteria. These arousals were summed for each sleep stage by sound type at each decibel step level and then plotted as arousal probability thresholds. The results provide evidence that repeated arousals occur from common hospital noises at typical decibel levels even in healthy young adults. The reported responses varied with the sound stimulus characteristics and across different sleep stages.

The Problem

Healthcare quality surveys report patient sleep disruption from noise as a very common and serious complaint. Disrupted and/or limited sleep has been demonstrated to have adverse impacts on several important health measures and outcomes including blood pressure, weight gain, heart disease, pain, stress levels, and inflammation. However, no quantification of the relationship of common hospital sounds to patient arousal has been available to guide policy, design and technical innovation.

The stakeholders

Patients and Families: The most vulnerable patients are the youngest and sickest, those admitted for the longest periods, or those exposed to high hospital census.

Caregivers and Staff: Their challenge is to offer compassionate care and to make critical time sensitive decisions in high stress environments.

Government Regulators: They are responsible for structuring the funding of care, especially for older patients. As a wave of baby boomers reaches the age when health typically declines, expanded need for care is anticipated.

Hospital Board and Management: Leaders must balance budgets in the face of rising expenses while delivering quality care.

Employers and Insurers: They seek cost effective care, placing patients in settings where insurance dollars translate into clinical outcomes.

Research methods and materials

Twelve sleeping fully-monitored healthy adult human subjects were exposed to a series of 14 hospital sounds, including voices, derived from the recording of an inpatient medical-surgical unit. The sounds were delivered in rising decibel level steps during all stages of sleep at a Harvard Medical School affiliated sleep laboratory.

Summary of research project steps

The research steps of this project included:

• Record real hospital sounds to develop a “virtual hospital” soundscape.
• Expose subjects, during all sleep stages, to soundscape components.
• Quantify specific physiological and cognitive responses.
• Demonstrate sleep arousal probability thresholds.
• Organize outcome data to inform the Acoustic Guidelines.

Summary of research project requirements

The selection, screening, and physiological measurement of sleep disrupted participants in this study required:

• Adult human subjects who had no medical or psychological problems, including sleep and hearing disorders.
• Robust methodology for presenting adequate numbers of scientifically valid reproducible sound stimulus exposures to subjects during 2 full nights of sleep monitoring.
• Analysis of all subject arousals attributable to sound stimulus exposures, controlling for depth of sleep at stimulus presentation and loudness of sound (with repeated measures for statistical precision).

Key findings and recommendations

The combined responses of all sleeping subjects are reported as sleep-stage-specific arousal probability curves. The curves demonstrate the percentage of those subjects experiencing lightened sleep or full arousal for each of 14 sounds (stimuli) at stepwise decibel levels from 40 to 70 dB(A).

A. Phone and intravenous infusion pump alarms, which are intentionally designed to be alerting, were effective in evoking the highest arousal probabilities.

Recommendations:

• Answer IV alarms promptly and lower background sound levels so important alarm signals can be easily discerned.
• Reduce telephone ring tone volume to prevent transmission beyond the patient rooms.
• Set telephones to stop after a specific number of rings.

B. Staff conversations, as well as voice paging, were also shown to be highly alerting. The threshold curves for voice stimuli are consistent with the arousal recollections reported by our subjects and documented as troublesome in health-care quality surveys. Voice level exposures can be modified behaviorally as well as through design and construction solutions. Some variation was identified among sleep stages, with light sleep (NREM2) showing the least protection from voices as well as other acoustic disruptions.

Recommendations:

• Materials and surfaces should be chosen to limit sound transmission from nurses’ stations.
• Special consulting spaces should be allocated for nurses in which voice-based information can be transferred away from open hall areas, yet not far from nursing stations.
• Protocols such as dimming hall lights at night as a “quiet cue” should be incorporated as part of behavioral protocols to limit sleep disruption by staff voices.

C. Exterior noises, those coming from outside the hospital building (jets, helicopters, road traffic) were found to be the least arousing stimuli at levels tested. Jets and helicopters may actually be experienced by patients at levels louder than those tested here. Further, the vibration and low frequency components experienced with actual exposures were not fully duplicated in our study and may in reality impact sleep arousal.

Recommendations:

Site considerations are critical to reduce air, train, and road traffic noise exposure.

• When site options are limited, enhanced building envelope solutions must be put in place to protect patients.
• Increasing concerns with regard to low frequency sounds, such as those attributed to airplane over flights and wind turbines, call for additional consideration of protective building envelopes, especially in rural areas where ambient noise levels have historically been low.

D. With regard to other stimuli, those with shifting contours (towel dispenser, door close, toilet flush, ice machine) tended to be more arousing than those with continuous contours (traffic and laundry cart).

Recommendations:

• Ice machines should be architecturally isolated from patient areas or dramatically re-engineered.
• Quieter or low-tech alternatives for automatic hand towel dispensers (often described as disruptive by patients) should be substituted.
• Proper door hardware will limit latch noises; door gasket selection will better protect patients from hall and nurses’ station noise, as well as blocking transfer out of noise generated within that patient room.
• Policy regarding keeping patient doors open should be re-examined. Other options should be considered, including systems-level solutions such as telemetry to a common station and assignment of staff to specific patients, allowing them to be individually alerted to patient needs.

Conclusion

Our results provide evidence in support of incorporation of minimum acoustic standards as part of the Guidelines for Design and Construction of Health Care Facilities. An estimated $240 billion price tag has been placed on healthcare construction for the period 2009 through 2013 (Jones, 2009). In this context the cost implications of additional requirements call for justification.

We are now witnessing a transformation in healthcare reimbursement to a “pay for performance” model. Design and construction mandates related to acoustics can be expected to enhance performance through more accurate communication, increased speech privacy and HIPAA compliance, lowered staff stress levels, decreased medical errors, and limited patient sleep disruption. Together these should produce better clinical outcomes, reduce staff turnover rates, and provide advantages in the competitive marketplace, all of which carry positive cost implications.