paper ID: 210 /p.1

SOUND ANALYSIS OF NOISE POLLUTION IN OPERATING ROOMS S. Luzzia, S. Falchib, C. Becchib, A. Baldacchinic a

Ordine degli Ingegneri della Provincia di Firenze, [email protected] b Santa Maria Nuova Hospital, Florence - Italy , c Vie En.Ro.Se. s.a.s., Florence - Italy

Noise in operating rooms (OR), recovery rooms and intensive care units is a hazard to surgeons, anaesthetists, personnel and patients. OR noise can reduce the mental efficiency and short-term memory of anaesthesia residents. Excessive exposure to noise pollution may be also an important cause of sleep disruption for conscious patients in the hospital. The paper refers to case studies carried out in OR and intensive care units of some Tuscan general hospitals. The structure of buildings has been considered and all the related characteristics of sound propagation towards sensitive receivers, workers and patients, in the operating theatre are analysed, using procedures for sound measurements reported by ISO and EC standard. The workgroup is composed of anaesthetists and acoustic engineers, joining their experiences and approaches.

1. INTRODUCTION OR are as susceptible to noise pollution as other working environments; the noise levels in an OR were likened to those encountered on a motorway. Staff and patients in the OR are exposed to a barrage of sounds. This cacophony is often enhanced by noise by adjacent scrub-up areas, instrument rooms, and sterilisers. For theatre staff this noise can lead to impaired concentration and performance, interference with communication, and increased levels of stress, and patients who are conscious for part or all of their time in the OR may become more anxious because of the noise [1]. In intensive care units several sources (SpO2 alarm, telephones, bed transfer, nursing care, opening packet and staff conversation, electro medical machines, air-conditioning plant, surgical suckers, sterilizers, clanging of metal bowls, instruments, trolleys) exceed this treshold and could influence quality of care and staff performances [2]. Also in the OR patients are exposed to unnecessary and preventable sounds, in particular during induction and recovery phases of anaesthesia. Many patients are distressed by the surgical suite sound levels and would desire a quieter environment [3]. The aim of this work is to show the results of measurements and the acoustic analysis performed in the main OR of a general hospital placed in an ancient building (Santa Maria Nuova Hospital, Florence-Italy). It is the starting point of a study for the requalification of the OR based on the definition of suitable models and simulation procedures to determine a general methodological approach for OR acoustic planning that will be applicable to different sceneries.

2. METHODS The analytic approach of the study is composed of following steps: sound levels measurements, frequency and statistic analysis, computation of indexes and definition of the acoustic environment during standard surgical activities, study of acoustic quality of building, furniture, materials, means of sound propagation and radiation. Workers and patients are considered sources of noise as well as noise receivers. (See Table 1)

paper ID: 210 /p.2

After installation of all noise sources their sound emission levels and the acoustic impact on the inside receivers was evaluated to verify the respect of the design parameters. The relative and simultaneous machinery use was took into account to built various noise emission sceneries. For the verification of the sound emission levels indications of specific norms were considered carrying out sound pressure level surveys both close to a single sound source than near sound source groups working simultaneously. For the impact acoustic assessment inside OR was defined for each meaningful source (single or grouped) an emission box comprising all receiver locations representative for the source and the correspondent paths of sound transmission. The locations interested by noise introduction coming from a given sound source, acoustically more close to the sound source itself according the modalities of air and structural propagation as well as horizontal and vertical one have been characterized like representative. Every box has been shaped like an independent scenery that can be utilized for the determination of noise introduction levels. From the sound pressure level measurements at the locations of the receivers it has been possible to obtain the entity of the various contributions.

Table 1: Analyitc approach. 1. SOURCES ANALYSIS

1. Sources For each single source present in the cases scenery identification and Code classification Picture Structural and Functional description

1.b Emission theatre representation

Technologic state of art for the type of source – Sound Emission Levels according to ISO standards Functional description of standard work cycles and each phase of activity Maps pointing out: -

static and dynamic sources position, motion areas of mobile sources, working places, position and motion areas for workers, patients position, position of other (eventual) active and passive receivers. Vertical Map, sections or 3D maps pointing out: - doors, windows, other points of sound transmission - sound reflecting areas in walls, floors and ceilings

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2. SOUND LEVEL MEASUREMENT

2.a. Residual and Background noise level measurement in all the receiver points

Inside the operating theatre closed without any activity around Inside the operating theatre closed with air conditioning systems on Inside the operating theatre open without main sources activity Inside the operating theatre open with standard speech between the staff Inside the operating theatre open during preparation phase 2.b Emission levels Sources emission - only source with no operating theatre activities levels - with standard hospital and OR activities (peculiar source measurements contribution) other statistic parameters: with omni-directional emission box, along the receivers’ directions Critical phases levels - starting points and higher speed of machines, gas escaping, sucker, alarm Comparison of measured data with datasheets and technical reference’s data of machinery in the following cases: - tested sources given by producers, - most recent machine of that kind, - most noise protected and lowest sound emitting machine of that kind 2.c Time histories and evaluation of indexes behaviour in time Noise mapping and frequency. Sequence of measurement and single events’ of two working analysis [Leq], [L90], [L10] [SEL] + other statistic days in the parameters surgical theatre Measurements with sound meters in LAF regulation for the with full most complex phases of the working cycles. operating cycles Spot measurements during equipment cleaning, preparation, using glass bottles, metallic bowls, etc. Measurements performed in proximity of workers ears to determine their own exposure to noise pollution and the related hazard in term of professional disease. Calculation of day and week A-weighted equivalent levels. 2.d Measurements of breaking in noise levels. Study of Noise impact on propagation model from sources located in outer spaces. the surgical Spatial and time decay law model for incoming Leq, theatre coming determined by acoustic features of the surgical environment: from outside. noise radiation surfaces, propagation patterns toward receivers and critical areas.

paper ID: 210 /p.4

3. NOISE DATA In the following figures are reported the noise continuous levels at the operator locations near to the operating table. In figure 1 are plotted equivalent and minimum noise continuous levels pointing out the single phases of the performed operations: in general anesthesia (a) and (b) or spinal anesthesia (c). In figure 2 are showed the time histories of three complete operations (a, b, c) and of their arrangement during day (d). Operation

Bed 2 moved

preparation

Speech 1

Speech 2

dB

90

80

70

60

50

40

30

N om e T o ta le (T u tti) (T u tti) (T u tti) (T u t ti) (T u tti)

L L eq O r a d i i n z io [d B ] 2 0 /0 1 /2 0 0 3 1 0 . 4 7 .4 7 2 0 /0 1 /2 0 0 3 1 0 . 4 7 .4 7 2 0 /0 1 /2 0 0 3 1 0 . 5 0 .0 1 2 0 /0 1 /2 0 0 3 1 1 . 0 0 .1 6 2 0 /0 1 /2 0 0 3 1 1 . 5 9 .1 4 2 0 /0 1 /2 0 0 3 1 2 . 1 9 .0 3

In te rv e n to S g o m b e ro le tto 2 p re p a ra z io n e c a m p o p a rla to 1 p a rla to 2

L L F M in [d B ] 6 0 ,3 6 0 ,3 6 2 ,4 6 2 ,9 6 2 ,3 6 2 ,8

7 2 ,6 7 2 ,6 70 7 5 ,6 7 3 ,5 7 0 ,4

20 10.50.00

11.00.00

11.10.00

11.20.00

11.30.00

11.40.00

11.50.00

12.00.00

12.10.00

12.20.00

12.30.00

LLeq LLFMin Cursore: 20/01/2003 11.59.07 - 11.59.08 LLeq=68,5 dB LLFMin=64,6 dB

Figure 1.a General Anaesthesia 1; Figure 1.b General Anaesthesia 2 Preinduction

Induction

Operation

Recovery

dB

90

80

70

60

50

40

30

N om e T o ta le (T u tti) (T u tti) (T u tti) (T u tti)

L Leq LLFM O ra d i in z io [d B ] [d B ] 2 0 / 0 1 / 2 0 0 3 0 9 .2 9 .5 1 7 2 ,8 A n e s te s ia 2 0 / 0 1 / 2 0 0 3 0 9 .2 9 .5 1 72 In t e r v e n t o 2 0 / 0 1 / 2 0 0 3 0 9 .5 5 .0 0 7 3 ,2 P a rla to 2 0 / 0 1 / 2 0 0 3 0 9 .5 5 .4 7 7 4 ,8 B l o c c o d i t e m p o 2 0 / 0 1 / 2 0 0 3 0 9 .2 9 .5 1 7 2 ,8

in 6 1 ,4 6 1 ,5 6 1 ,4 6 1 ,4 6 1 ,4

20 13.20.00

LLeq

13.30.00

13.40.00

13.50.00

14.00.00

14.10.00

14.20.00

14.30.00

LLFMin Cursore: 20/01/2003 13.46.21 - 13.46.22 LLeq=67,6 dB LLFMin=65,5 dB

paper ID: 210 /p.5 Anaesthesia Operation

Speech

dB 90

80

70

60

50

N om e T o ta le (T u tti) (T u tti) (T u tti) (T u tti)

40

30 20 09.30.00

L Leq O ra d i in z io [d B ] 2 0 /0 1 /2 0 0 3 0 9 .2 9 .5 1 A n e s te s ia 2 0 /0 1 /2 0 0 3 0 9 .2 9 .5 1 In te rv e n to 2 0 /0 1 /2 0 0 3 0 9 .5 5 .0 0 P a rla to 2 0 /0 1 /2 0 0 3 0 9 .5 5 .4 7 B lo c c o d i te m p o 2 0 /0 1 /2 0 0 3 0 9 .2 9 .5 1

09.40.00

09.50.00

10.00.00

LLFMin

LLeq

7 2 ,8 72 7 3 ,2 7 4 ,8 7 2 ,8

10.10.00

L L F M in [d B ] 6 1 ,4 6 1 ,5 6 1 ,4 6 1 ,4 6 1 ,4 10.20.00

10.30.00

Cursore: 20/01/2003 10.05.56 - 10.05.57 LLeq=69,9 dB LLFMin=65,6 dB

Figure 1.c Spinal anaesthesia 85

85

80

80

75

75

70

70 65

65

60

time

60

time

55

55 0

50 Lleq (dB)

100 Llfmin(dB)

0

150

20 Lleq(dB)

Poli. (Lleq (dB))

Figure 2.a General anaesthesia 1

40

60

Llfmin(dB)

80

100

Poli. (Lleq(dB))

Figure 2.b General anaesthesia 2 85

80

80

75

75 70

70

65

65 60

60

time

55

time 55

0 0

20 Llfmin(dB)

40 Lleq(dB)

Figure 2.c Spinal anaesthesia

60

80

Poli. (Lleq(dB))

100

200

300

LLFMin [dB] 60,3 60,3 60,3 spinale generale1 generale2 Poli. (spinale)

Figure 2.d Whole day

400

paper ID: 210 /p.6

4. DISCUSSION The collected data show that the min. noise level inside OR during a standard working day always exceeds 60dB. In particular noise pollution reaches the highest levels (80-90dB(A)) during the induction and recovery phases of anaesthesia. As shown by the trend lines overlapped to the time histories, the induction and awakening phases are clearly noisier in the case of operations (Fig.2 a,b) in general anesthesia. Looking at the collected processed data a priority scale about the possible interventions for noise reduction can be obtained. In the considered case study the improvement of acoustic passive requirements of the room including the OR appear to be the more effective noise reduction method. The parameters used to acoustically characterize the buildings are: the reverberation time (T) defined by norm ISO 3382, 1975; the appearing transmission loss of separation elements between rooms (R) defined by norm UNI EN ISO 140-4, 2000; standardized sound insulation of facade (D2m, NT) defined by norm UNI EN ISO 140-5, 2000 and standardized impact sound level of floors (Ln) defined by norm UNI EN ISO 140-7, 2000. Italian regulations with reference to the hospitals, clinics, old cure houses establish the values that the following rating indices have to assume: rating index of appearing transmission loss of separation elements between rooms (Rw); rating index of sound insulation of facade (D2m, NT, w) and rating index of the standardized impact sound level of floors (Ln, w).

5. CONCLUSIONS The definition of a general methodological approach to noise mapping of the surgical environment of a General Hospital represent the first methodological step of a project called ADOR (Acoustic Design of OR). During the first analytical phases of this study a priority scale about the possible interventions for noise reduction and reclamation inside OR has been obtained. In conclusion, when there are not mechanical sound sources or particularly noisy systems, as in the considered case study, the more effective noise reduction method is the improvement of acoustic insulation requirements of the architectonic elements as well as the improvement of acoustic absorption. It remains however important to reduce the noise due to the conversations among the sanitary staff not necessary to the therapy.

REFERENCES [1] Hodge B., Thompson J.F., Noise pollution in the operating theatre, Lancet 335, pp.891-894, (1990). [2] Allaouchiche B. Et al.,Noise in the postanaesthesia care unit, British Journal of Anaesthesia 88, pp.369-373, (2002). [3] Liu E.H.C., Tan S.M., Patient’s perception of sound levels in surgical suites, Journal of Clinical Anesthesia 12, pp.298-302, (2000).