Portuguese Version

Year:  2003  Vol. 69   Ed. 6 - (6º)

Artigo Original

Pages: 766 to 771

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Qualification and quantification of ambient noise exposure in a general intensive care unit

Author(s): Raquel Paganini Pereira1,
Ronaldo N. Toledo2,
José Luiz G. do Amaral3,
Arnaldo Guilherme4

Keywords: intensive care units, noise measurement, sound contamination, hospitals

Abstract:
Noise levels in hospitals are excessively high, especially in the ICU environment, because of the numerous alarms and equipment, in addition to the conversation of the hospital staff itself. For this reason, this environment, which should be quiet and calm, has become noisy, thus converting into a major stress factor, likely to cause physiological and psychological disorders in both inpatients and the unit personnel. Aim: The purpose of this study was to assess the equivalent noise pressure level in a general ICU, in an attempt to establish the period of greatest exposure and to compare the results to both domestic and international recommendations. Study design: Observational study. Material and Method: Measure the ambient noise in the ICU of Hospital São Paulo using a noise analyzer model 2260 (Brüel & Kjaer) for a total period of 6.000 minutes, at a rate of one reading every 27 seconds, was carried out with the following configuration: fast response time, measuring the noise pressure level in decibels with A-frequency weighting, from September 2001 to June 2002, without knowledge by the sector personnel. Results: The average equivalent noise pressure level (Leq) was of 65.36 dB(A) ranging from 62.9 to 69.3 dB(A). During the day, the average Leq was of 65.23 dB(A), and at night 63.89 dB(A). LFMax was found to be 108.4 dB(A) and LFMin of 40 dB(A). Conclusions: The noise level found in this ICU is above the recommended by the literature during all the periods examined. Thus, excessive noise sources need to be better identified so that proper steps may be taken to reduce this noise and make this environment more silent, thus improving the professionals' work and the patients' recovery.

Introduction

Excessive environmental noise, a problem that started after the industrial revolution, is widely disseminated and almost intolerable nowadays. There are practically no places free from noise. We are exposed to noise during leisure time, at home, in the streets and at work 1. Also at hospitals, technology advances have brought as a consequence potentially harmful noise levels 2.

Many hospitals are located in areas exposed to external noise sources, such as the traffic of large avenues, airports, etc. It seems, however, that much noise in the hospital is derived from within, being that the main sources of noise are the ICU equipment and the talks among hospital teams 3-5.

At hospital settings, the Intensive Care Units (ICUs) are particularly problematic areas. They have devices with sound alarms, essential to warm physicians and nursing staff about changes in the clinical conditions of patients or poor functioning of the devices. Thus, this area that should be quiet and calm, became noisy and stressing 5, increasing anxiety and the perception of pain, reducing sleep and prolonging convalescence 1, 6, 7.

In fact, in order to increase efficiency and safety, more physiological parameters are monitored and more pieces of equipment are used in the clinical routine 8. Among the common examples of noise generators, we can name aspirators, cardio scopes, oxymeters, ventilators, oxygen and compressed air outputs, computers, printers, fax machines, telephones, furniture changes, and dialogs between the healthcare professionals and the patients 1.

Noise affects the psychological status of subjects that are in the ICU causing sleep disorders and disorientation in patients and anxiety in more susceptible nursing staff members 9, 10.

A calm and pleasant environment can benefit the patients and the hospital staff. Healthcare professionals may feel less tired and less psychologically stressed, patients will have fewer psychological and physiological deficits and, therefore, they will recover quickly 2.

Since 1974, the United States Environmental Protection Agency11 recommends that levels of hospital noise should not exceed 45 dB (A) during the day and 35dB (A) during the nigh. The Brazilian Association of Technical Norms 12 (ABNT-NBR 10152, 1987) recommends 35 to 45 dB (A) as acceptable levels for different hospital settings. These limits are frequently exceeded, generating physiological and psychological disorders both in patients and in those that work in the area 5, 13.

Noise and its subsequent effects on health and on the cure of diseases has been a concern for years 14, 15. Therefore, the determination of the amplitude of ICU noise is essential, so that we can quantify the problem and propose measures that aim at dealing with it.

Material and Method

The present study was conducted at the general ICU of Hospital Sao Paulo using environmental noise measurements through a Noise Analyzer model 2260 (Brüel & Kjaer, Denmark), in compliance with ABNT (2000) norms, and set up as follows: fast response time (Fast), measuring in decibels sound pressure level (SPL) with A-frequency weighting. The measurement range comprised 40 to 120 dB (A) and the sound spectrum ranged in the octaves of 31.5 Hz to 8KHz. The environmental noise measures at the ICU were conducted between October 2001 and June 2002 in the period of 8, 12 and 24 hours, from Monday to Friday. In each period of analysis, we measured noise every 27 seconds, amounting to 6,000 minutes of measurements (Figures 1 and 2).

The equipment was always placed approximately in the center of the ICU at 1.5m from the floor, over a tripod, at the same level of the bed.

The noise analyzer 2260 stored the data, recorded all sound occurrence throughout time and later we analyzed them through the software Brüel & Kjaer 7696 (Evidence).

We adopted the following measures of sound intensity: Leq (equivalent sound pressure level), LFMax (maximum sound pressure level), LFMin (minimum sound pressure level).

Before each measurement, the device was calibrated according to the manufacturer's instructions to standardize the measurements. The measures were performed by the main investigator and the local staff was not aware of the recordings.

Results

As to total period of measurement (6,000 minutes), the equivalent sound pressure level (Leq) found in our study presented a mean of 65.36 dB (A) ranging from 62.9 to 69.3 dB (A). The values of LFMax found were 108.4 dB (A) and LFMin was 40 dB (A), as shown in Table 1, which represented, respectively, the maximum and minimum values of sound pressure level reached.

The mean of Leq found for the nigh shift was 65.23 dB (A), in the morning shift it was 65.85 dB (A) and in the afternoon shift it was 65.07 dB (A) (Table 2).

Table 3 shows the Mean Leq referring to the nigh period (6:00 to 06:00am) was 63.89 dB (A). In the first period (06pm to 12:00) it was 65.52 dB (A) and in the second period (12:00 to 06:00 am) it was 59.84 dB (A).

Table 1. Mean, maximum and minimum values in dB (A) of environmental noise measurements in a total period of 6,000 minutes.



Table 2. Values in dB (A) of environmental noise measurements in the night, morning and afternoon shifts.



Table 3. Values in dB (A) of environmental noise measurements at night, during the first and second periods.




Figure 1. Individual profile of Leq in dB(A) in different measurements.



Figure 2 - Mean profile of Leq in dB(A) of measures made for 24 hours.

DISCUSSION

If on the one side the technology advances experienced in past years at the ICUs have been very important because provided better care to patients, on the other side they have brought a number of technical devices, monitored by acoustic alarms that added by the background noise created by the activities and the conversation of the medical staff, end up transforming the ICU area, which should be calm and quiet, into a noise and stressing environment that hinders the occupational performance of the teams and the recovery of hospitalized patients.

As noise levels range randomly in time, normally we measure the so-called equivalent level (Leq), expressed in dB, which represents the mean of sound energy during a time interval 16.

The noise level found in our study presented mean of 65.36dB (A) that exceeded the maximum value of 45 dB (A) recommended by the United States Environmental Protection Agency11 (1974) and ABNT12 (1987), as well as by the World Health Organization17 (1993), which recommenced Leq of up to 40 dB (A) for day period and 35 dB (A) for the night period at hospitals.

The difference between our findings and the recommended levels is particularly important because the sound pressure level in dB (A) is proportional to the sound intensity measured in logarithmic scale. Within this context, a relevant issue is that, according to acoustic physics laws, an increase in 10dB (A) results in double the value in subjective sound scale 18. Therefore, we face 20dB over the literature recommended levels, which demonstrates a concerning increment of noise level.

Normally, the sound levels in a calm hospital 6 should be range from 40 and 50 dB; in an intermediate area, between 50 and 60 dB, and in noisy environment, as already observed, it would be around 60 to 70 dB.

Many studies have demonstrated high levels of noise in the ICU, with Leq between 60 and 65 dB (A) in a hospital in Austria5; sound levels that exceeded 55 dB (A) in a hospital of the University of Valencia 15, in Spain, and 68.0 dB (A) in an ICU of a hospital in Manitoba 19, Canada, consolidating the idea that noise pollution in the ICU is not limited to a single country or culture.

In the study by Mendoza-Sánchez et al.3 the levels of noise varied from 50 to 59 dB (A) at the site in which it was considered moderately noisy; except for the ICU, in which the levels exceeded 59 dB (A), owing to the use of many devices, such as monitors, continuous infusion pumps, mechanical ventilation devices, alarms and other sources of noise.

The levels of noise have also been analyzed by measuring the generating sources 20, such as hospital team discussions and dropping of objects on the floor (especially metallic objects), reaching values of 75 to 92 dB (A), respirators recorded 49 to 72 dB (A) and equivalent level (Leq) ranged from 60.3 to 67.4 dB (A).

Meyer-Falcke et al.14 observed that Leq was never below 60dB (A) and the Lmax recorded was over 100dB (A), values probably due to alarms of the devices used by the unit. The authors highlighted in their work that noise level was low in situations of emergency and stress for the hospital team, differently from those recorded in situations of routine, in which they were louder.

Our findings concerning the day period were higher than those by Aitken4, who found Leq values between 50 and 60 dB (A) during the day; in addition, Bentley et al.3 observed mean of 53 dB (A) in a ICU unit of London, whereas Murthy et al.21 obtained Leq = 77.32 dB (A).

Analyzing the acoustic level of the ICU in Italy, Bovenzi and Collareta22 found Leq of 56.9 and 61.2 dB (A) during the day. These values were below those found in our study, but even so the levels were of concern and above the recommended doses.

In the study by Garrido and Moritz23 the levels of noise found in the ICU reached 80db(A) during the day and 70 dB (A) during the night, reporting that the noise levels above the desirable range generated unpleasant memories in patients hospitalized in the area.

Innumerous studies 24, 25 have demonstrated that sleep deprivation is a common problem in ICUs and, therefore, quality of sleep is frequently impaired by excessive noise and REM sleep is very reduced in these patients. In view of that, it would be desirable to have a significant reduction in noise levels, especially during the night.

Bovenzi and Collareta22 found values of Leq of 53.5 to 57.7 dB (A) referring to the noise of the ICU at night, whereas Soutar and Wilson18 found mean sound level of 66dB (A), a value above the one that calculated in our study, which demonstrates that patients' sleep was severely affected during the night period.

Excessively loud sound levels, such as 70 dB (A), were observed during the night in the study by Garrido and Moritz23. These authors reinforced the importance of having a restructuring of the operation of ICUs so that the hospitalized patients can receive comprehensive treatment, both from clinical and psychological perspectives.

Conversely, the values of Leq closer to the recommended levels reported in the literature were found by Aitken4, who found Leq of 45 dB (A) during the night and Bentley et al.3, who recorded 42.5 dB (A) during the most silent night period.

A noisy environment hinders comfortable rest causing in patients sleep disorders, psychological disorders such as disorientation and even anxiety in more susceptible nursing staff members9, 21, 26. Moreover, the exposure to loud noise can cause pathophysiological disorders to the cardiovascular system, possibly the circadian rhythm disorders 27, 28.

Noise prevention should be planned at the beginning of installation and acquisition of equipment or its handling, since later modifications are more costly. Some noise sources, such as the inevitable oxygen use, suction devices or respirators cannot be changed, however, Tsiou et al.20 stated that the alarms could be more silent, especially during the night.

Patients submitted to ICU hospitalization can present behavioral disorders, among them ICU psychosis, which are exacerbations caused by sleep deprivation and generated by environmental conditions, among them continuous noise exposure 29.

Grumet 30 considered that noise control in hospitals is a priority, and in our opinion, to prevent excessive noise exposure we should insist on studies that demonstrate the excessive noise to which subjects are exposed, including staff and patients in the ICU. The next step would be to come up with measures, together with the team, to improve the stay in the unit. Simple measures such as closing the doors, speaking softly and turning off alarms whenever possible would drastically reduce noise levels 7.

In order to make the work environment as quieter and pleasant as possible, aiming at benefiting occupational activities and the more satisfactory recovery of patients, we suggest the adoption of some measures to ensure reduction of noise levels, such as for example replacement of acoustic for visual alarms, whenever possible; creation of different categories of alarms, aiming at distinguishing them in case of life-threatening occurrence as opposed to routine occurrence; periodical analysis of the acoustic profile of ICUs; revision of devices used and the care provided to patients and also further communication of study findings, making the teams aware and instructed about possible auditory and/or non-auditory effects of high noise levels.

At the end of the analysis, we could observe that the noise comfort level in the assessed ICU is very deficient, showing exposure to loud noise levels, louder than the levels recommended by the literature and the standardization agencies.

Therefore, noise sources should be identified for such data to serve as subside to the responsible parties so that measures can be taken to attenuate the noise to more acceptable levels.

The contribution of each one should be defined so that efficient measures for their reduction can be adopted, since noise in the work environment originates from many sources.

The hospital team should be aware of noise and its effects, since then they can act in a more effective way to reduce loud noise level exposure.

Thus, we believe that the ICU will become a quieter and calmer environment, benefiting the performance of the staff and the recovery of patients.

CONCLUSIONS

1. There was no statistically significant difference between level of noise exposure during the day x night, presenting a tendency to quieter levels during the night.
2. Regardless of the period, the noise levels recorded in the ICU were considerably louder than recommended.

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1 Master studied under course, UNIFESP-EPM.
2 Doctorate studies under course, UNIFESP-EPM.
3 Full Professor, Escola Paulista de Medicina - UNIFESP. Faculty Professor, Discipline of Anesthesiology, Pain and Intensive Care, UNIFESP-EPM.
4 Ph.D. in Medicine, UNIFESP-EPM. Joint Professor, Department of Otorhinolaryngology and Human Communication Disorders, UNIFESP-EPM.
Affiliation: Escola Paulista de Medicina -Federal University of Sao Paulo - Department of Otorhinolaryngology and Human Communication Disorders.
Address correspondence: A/C Raquel Paganini Pereira - Rua Apeninos, 990 apto 64 Paraíso São Paulo SP 04104-020
Tel (55 11) 9657-1057
Article submitted on August 01, 2003. Article accepted on September 04, 2003.

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