Clinical Concepts and Commentary
Jerrold H. Levy, M.D., F.A.H.A., F.C.C.M., Editor
Noise in the Operating Room
Jonathan D. Katz, M.D.
“Unnecessary noise is the most cruel absence of care
which can be inflicted either on sick or on well.”
—Florence Nightingale, 1859
perception, hospital, operating room, and music. Searches
were conducted using PubMed, Ovid, and Google Scholar.
The reference lists of all articles discovered in these searches
were examined for additional references.
A
s recently as the 1960s, hospitals were famous for their quiet
and serene environment. Noise restrictions were zealously
enforced internally by uniformed nurses and externally by street
signs around the perimeter declaring “Hospital—Quiet Zone.”
Hospitals and especially operating rooms are no longer
quiet.1 In 1972, before the introduction of much of the noisy
equipment now routinely used during surgical procedures, it
was observed that noise levels in operating rooms frequently
exceed those of a busy highway.2 The authors labeled noise as the
“third pollution” along with air and water pollution. Others have
described the noise in critical care areas as equivalent to the cafeteria at noon and only slightly less noisy than in the boiler room.
More recent studies have reaffirmed the escalation of the
noisy atmosphere of hospitals and operating rooms. Average noise levels commonly are greater than federal limits for
occupational noise exposure and frequently exceed those
considered a hazard to health.
Noise levels of this intensity have wide-spread implications for healthcare workers and their patients. In the following report, we will examine the common sources and
possible consequences of excessive operating room noise and
suggest some remedies.
Regulation of Occupational Noise
Several federal agencies, including the Occupational Safety and
Health Administration, National Institute for Occupational
Safety and Health, and the Environmental Protection Agency,
have developed guidelines and recommendations for safe levels
of noise in the workplace. These differ considerably in large part
because of differences in the formulae used to determine harmful exposure. For example, the guidelines from the National
Institute for Occupational Safety and Health are most conservative in that they begin with a time-weighted average of 85
decibels (A) (dBA) (the allowable continuous exposure for an
8-h work day) and use a 3-dBA time/intensity exchange rate
in which the permissible time of exposure is halved for each 3
dBA increase in sound (the “3 dBA rule”)* (fig. 1). The limits
established by the Occupational Safety and Health Administration begin at 90 dBA for an 8-h work day and use a 5-dBA
exchange rate in recognition of the fact that in most workplaces
interruptions in noise exposure occur throughout the day.† Specifically within hospitals, average noise levels of 45 dBA or less
are recommended. Both National Institute for Occupational
Safety and Health and Occupational Safety and Health Administration guidelines agree that the peak level for impulsive noise
(characterized by a steep rise in the sound level to a high peak
followed by a rapid decay) should not exceed 140 dBA.
These noise exposure regulations represent a compromise
between practicality and hearing protection. They are not
Materials and Methods
A literature search was conducted during the period from
October 2013 to January 2014 searching for the following
terms: noise, noise pollution, occupational noise, auditory
This article is featured in “This Month in Anesthesiology,” page 1A. The figure was created by Annemarie B. Johnson, C.M.I., Medical
Illustrator, Vivo Visuals, Winston-Salem, North Carolina.
Submitted for publication January 4, 2014. Accepted for publication April 16, 2014. From the Department of Anesthesiology, Yale University School of Medicine, New Haven, Connecticut.
* National Institute for Occupational Safety and Health. Criteria for a recommended standard: Occupational noise exposure. Revised criteria
1998. Available at: http://www.cdc.gov/niosh/docs/98-126/pdfs/98-126.pdf. Accessed August 27, 2014.
† U.S. Department of Labor. Occupational Noise Exposure.29 CFR x1910.95. Available at: http://www.osha.gov/dts/osta/otm/noise/standards.html. Accessed December 23, 2013.
Copyright © 2014, the American Society of Anesthesiologists, Inc. Lippincott Williams & Wilkins. Anesthesiology 2014; 121:894–8
Anesthesiology, V 121 • No 4
894
October 2014
EDUCATION
Fig. 1. A schematic illustration to show relative intensities of different noises and the acceptable time limits of exposure. The
noise levels commonly experienced in a modern operating room frequently exceed limits for a workplace established by the
National Institute for Occupational Safety and Health (NIOSH). Adapted, with permission, from the Centers for Disease Control and Prevention. Original graphic available at: http://www.cdc.gov/niosh/topics/noise/chart-lookatnoise.html. (Adaptions are
themselves works protected by copyright. So in order to publish this adaption, authorization must be obtained both from the
owner of the copyright in the original work and from the owner of copyright in the translation or adaption.)
designed to protect every worker from experiencing any noiseinduced hearing loss and they do not address other noiseassociated health and performance hazards. Many authorities
believe that a workplace noice limit of approximately 55 dBA
would be necessary to ensure universally safe conditions.
Sources of Noise in the Operating Room
Noise within operating rooms comes from both staff and
equipment. Staff-related activities and conversations are a
major component of operating room noise and can produce
noise levels as high as 78 dBA.3 Equipment-related noises
as great as 120 dBA are caused by movement of equipment,
clanging and dropping of metal instruments, and use of electric
or air-powered surgical instruments, hammers, suction apparatus, anesthetic monitors, and alarms. Forced air warming units
alone add as much as 84 dBA to the background noise (Jonathan D. Katz, M.D., Noise from forced air patient warming
units. Unpublished data. Data collected in November, 2013).
The monitors in a modern operating room are host to a
great many alarms and alerts which are commonly cited as
the most intrusive of operating room noises. These alarms
frequently provide extraneous, ambiguous, or false information that has no therapeutic significance. In one study
conducted during cardiac surgery, there was an average of
359 ± 158 alarms (1.2 min−1), 80% of which had no therapeutic significance.4 All of these false alarms can desensitize the staff so that true alarms go unrecognized. In many
cases, the alarms are so annoying and distracting that they
are turned off. This practice is discouraged in the Standards
for Basic Anesthetic Monitoring of the American Society of
Anesthesiologists which suggest only “brief ” interruptions of
monitoring in “rare or unusual circumstances.”‡
‡ American Society of Anesthesiologists, Standards for Basic Anesthetic Monitoring. Last Amended October 20, 2010. Available at:
http://www.asahq.org. Accessed December 23, 2013.
Anesthesiology 2014; 121:894-8895
Music is also a frequent contributor to operating room
noise. The exact noise levels resulting from background
music in operating rooms have not been quantitated but can
be extrapolated from a report citing noise levels as high as 87
dBA that are commonly generated by music played on home
audio equipment.5
Noise Levels in Operating Rooms
Noise levels in operating rooms frequently exceed the limits established by federal regulatory agencies. In 1972, Shapiro and Berland2 reported noise levels as high as 85 dBA
in the operating room during a routine cholecystectomy.
Twenty years later, Hodge and Thompson6 reported intermittent sounds to 108 dBA during a “typical major surgical
procedure.” Forty years after Shapiro’s report, Fritsch et al.7
reported noise levels as high as 131 dBA during simulated
otolaryngeal surgery.
Operating rooms are noisy even when unoccupied due in
part to their high-capacity air conditioning systems. Noise
increases progressively with the entry of staff and patient.
Once surgery commences, peak levels can exceed 120 dBA.8
Levels remain greater than 100 dBA for greater than 40%
of the time during some particularly noisy procedures, such
as orthopedics, neurosurgery, and extracorporeal shock wave
lithotripsy. The beginning and the end of surgery, which
coincide with anesthetic induction and emergence, are especially noisy periods.9 At these times, surgical equipment is
being prepared or dismantled and conversations unrelated to
direct patient care occur between staff members.
Impact of Noise Pollution in the
Operating Room
Occupational Health
Exposure to occupational noise levels as low as 75 dBA can
have both short- and long-term adverse effects on health.10
Jonathan D. Katz
Noise in the Operating Room
Predisposing individual factors such as age, comorbid medical conditions, medications, and lifetime total cumulative
noise exposure also play a role in how and to what extent an
individual responds to noise.
The most commonly reported health consequences of
chronic exposure to high noise levels are tinnitus and hearing
loss. The nature and severity of the hearing impairment is a
direct function of the intensity and frequency of the sound
pressure and duration and pattern of exposure.
There is growing evidence that nurses and surgeons who
consistently work in noisy operating rooms are susceptible
to noise-induced hearing loss.11 Substantial hearing loss has
also been demonstrated among anesthesiologists. In a study
conducted by Wallace et al.,12 66% of anesthesiologists had
abnormal audiograms and those younger than 55 yr had a
hearing acuity significantly worse than the general population.
Anesthetized patients may be particularly vulnerable to
acoustic trauma after long exposure to noisy surgical equipment. Anesthetic drugs weaken the stapedius muscle, which
normally contracts and protects the cochlea when exposed to
loud sounds. In the absence of this protective reflex, hearing
impairment may occur, especially among vulnerable populations such as the elderly.
Noise, especially unexpected high-intensity sounds, acts as a
biologic stressor that can produce a startle reaction and activate
the fight or flight response of the autonomic and endocrine systems. Chronic exposure to excessive noise has been associated
with increases in heart rate, blood pressure, peripheral vascular
resistance, and an increased prevalence of various forms of cardiovascular diseases, including hypertension, angina pectoris,
myocardial infarction, and premature death.13
Cognition
Chronic noise exposure, even at moderate intensity, can
hamper psychomotor, intellectual, attention, and memory
functions. This impairment is especially apparent when an
individual is exposed to “irrelevant speech” while engaged in
mental activities that rely heavily on working memory, such
as during multitasking. The impact of this detrimental effect
of noise on anesthesiologists was demonstrated in a study
in which deterioration of mental efficiency and short-term
memory was observed among anesthesia residents exposed
to a recording of typical operating room noises.14
Communication
One of the most harmful of the acute effects of noise pollution in the operating room is the interference it imposes on
verbal communication. Communication among staff members is a key component of patient safety. However, communication failures during surgery are common and have been
identified as one of the leading root causes of error and poor
§ The Joint Commission. Sentinel Event Data: Root Causes by Event
Type. 2011. Available at: http://www.jointcommission.org/Sentinel_
Event_Statistics/. Accessed December 23, 2013.
Anesthesiology 2014; 121:894-8896
patient outcomes by The Joint Commission.§ The ability of
noise to disrupt operating room communication was demonstrated in a study in which the auditory processing functions of surgeons were significantly diminished by music and
operating room noise.15
Performance
Activities that require a high degree of information processing and concentration are particularly susceptible to the
adverse effects of noise. There have been conflicting reports
on the impact of noise on surgical performance, explained in
part by variables in experimental design. The complexity of
the task and the experience of the surgeon play a significant
role in how noise affects surgical tasks.
There is little evidence to demonstrate a direct association
between excessive operating room noise and poor surgical
outcomes. In one study, a correlation was identified between
increased sound levels during surgery and surgical-site infections.16 The authors hypothesized that the increased sound
levels might be a surrogate marker indicating distraction or
difficulty encountered during the procedure.
Anesthesiologists are especially affected by a noisy operating room because of their continuous presence in the room,
their close proximity to noisy equipment, and the fact that
the noisiest times occur during the critical anesthesia components of a case. In one study, 84% of anesthesiologists
reported that the noise levels in their operating rooms negatively affected their work.17
Nurses and other operating room personnel who work in
close quarters with surgeons and anesthesiologists are subject
to the same noise-induced handicaps.
Patient safety and comfort can be adversely affected by
noise pollution. Noise is a top complaint among hospital
patients and consistently gets the worst marks on Medicare
patient surveys. In a study of patients undergoing elective
surgery, 52% reported that it was noisy during the induction
and/or emergence of anesthesia and 16% found the noise
to be distressing.18 In addition, higher doses of propofol are
necessary to achieve the desired bispectral index in a noisy
operating room.19
Music
Music is a special type of noise. Carefully selected music has a
well-known calming effect during stressful situations. However,
the role of music in the operating room remains controversial.
Music can add 87 dBA or more to the already considerable
ambient noise levels in the operating room.5 Depending on a
number of circumstances, including coexistent environmental
factors, personal taste, and the required task, an individual’s
response to music can vary from soothed to distressed.
Music has variously been shown to have a positive, neutral, or negative effect on different measures of surgeons’
performance. In one frequently cited study, Allen and Blascovich20 found that autonomic reactivity was reduced and
mental task performance increased in surgeons listening
Jonathan D. Katz
EDUCATION
to self-selected music as compared with no music and to
generic stress reduction background music. It is important
to note that the volunteers in this study were all self-reported
music enthusiasts, the music was self-selected, the study was
conducted in a sound-proof laboratory, and the task tested
was an arithmetic exercise.
Others have reported a detrimental effect of music on
surgical performance, especially among less experienced
surgeons. For example, in one randomized controlled trial
of novice surgeons, music during training procedures was
shown to cause distraction and impaired performance.21
The impact of music on anesthesiologists is also unclear.
Carefully selected and modulated music can improve vigilance
and monitoring performance. However, many anesthesiologists feel that music can reduce the ease and accuracy of performing their tasks. In one study, 26% of anesthesiologists felt
that music reduced their vigilance and impaired their communication with other staff and 51% felt that music was distracting when a problem was encountered.22 Seventy-eight percent
felt that music that they disliked was the most distracting. On
the contrary, a subsequent study by the same group failed to
identify any adverse effect of self-selected or classical music
on psychomotor tests (testing numeric vigilance, tracking, and
reaction time) performed by residents in anesthesiology.23
Patients are also affected by music in the operating room.
Carefully selected music can have an anxiolytic and sedative
effect on patients before, during, and after surgery. This beneficial effect seems to be independent of the additional advantage
provided by blocking out ambient operating room noises.24
For all personnel in the operating room, it is apparent
that the selection of the music and the manner in which it is
delivered play a key role in its effect.
Suggested Remedies
The adverse effects of noise pollution can be ameliorated by
either blocking the production of the noise or the entry of
noise into the ear. The easiest and most effective solution is
to minimize the noise production.
Because the operating room staff is the source of a large
component of the noise pollution, efforts can be directed
toward minimizing irrelevant conversation, especially during
critical times. One approach that has been advocated is to
adapt a “sterile cockpit” environment, as used in the aviation
industry, which also requires use of standardized nomenclature and a structured format for communication.25
A second approach is to develop a behavior modification
program to educate staff members about the sources and
potential harm of noise pollution. This educational program
should focus on common and easily remedied sources of
extraneous operating room noise. The effectiveness of this
approach has been demonstrated on acute inpatient hospital
wards and in intensive care units.26
Consideration should be given to noise when decisions
are made concerning supplies and operating room design.
Noisy equipment such as speakers should be placed as far
Anesthesiology 2014; 121:894-8897
as possible from the anesthetizing location. Substitution of
plastic bowls and trays for metallic ones can minimize noise
from clanging of these implements. Installation of sound
insulation and avoidance of sound-reflective floor, wall, and
ceiling surfaces would be significant factors in limiting echoing and reverberation of unavoidable noises.
Conclusion
The noise levels in hospitals and operating rooms are consistently above the limits established by federal regulatory
agencies, in many cases by as much as 40 dBA. These noise
levels have been associated with adverse consequences on
the health and performance of staff and on patient safety.
Much of this noise is generated by operating room personnel and is avoidable. Some corrective measures can be taken
at little expense and inconvenience to staff. Additional
research is needed to identify materials and design to further
limit equipment-related noise.
Acknowledgments
Support was provided solely from institutional and/or departmental sources.
Competing Interests
The author declares no competing interests.
Correspondence
Address correspondence to Dr. Katz: Department of Anesthesiology, Yale University School of Medicine, 41 Island View Avenue, Branford, Connecticut 06405. jonathan.
[email protected]. Information on purchasing reprints may be
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at the beginning of this issue. Anesthesiology’s articles are
made freely accessible to all readers, for personal use only,
6 months from the cover date of the issue.
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Jonathan D. Katz