ASSOCIATIONS OF ACOUSTIC ENVIRONMENT WITH PHYSIOLOGICAL AND PSYCHOLOGICAL STATES AMONG HOSPITALIZED PATIENTS IN GENERAL HOSPITAL WARDS

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1 ASSOCIATIONS OF ACOUSTIC ENVIRONMENT WITH PHYSIOLOGICAL AND PSYCHOLOGICAL STATES AMONG HOSPITALIZED PATIENTS IN GENERAL HOSPITAL WARDS Zhixiao Deng University of Sheffield, School of Architecture, Western Bank, Sheffield, UK Hui Xie Chongqing Chongqing, School of Architecture and Urban Planning, Chongqing, China Jian Kang University of Sheffield, School of Architecture, Western Bank, Sheffield, UK Hospital ward is supposed to provide a safe and quiet environment for patients treatment and recovery. However, noise levels in most hospitals across the world have exceeded the limit of relevant standards. To test whether excessive noises have negative influence in the rehabilitation of patients, 60 eligible participants were recruited during their hospitalized treatments in a general hospital in China. They were randomly allocated to the normal ward and acoustically refurbished silent ward, with the same geometry and appearance. Sound pressure level in the ward (SPL), patients vital parameters were measured synchronously for 24 hours for each participating patient. As a result of acoustical absorption treatment, reverberation time of the silent ward was 0.30 s at middle frequencies, compared with 0.56 s of the normal ward. Although there were little differences on the average daytime noise level (L eq_daytime ) between silent ward (59.6 dba) and normal ward (61.4 dba), the average night-time noise level (L eq_nighttime ) decreased by approximately 5 dba from 51.7 dba to 46.5 dba. Lower sleep disturbance on conversation, emotion and sleep was found among patients in the silent ward. No significant correlations between noise level and blood pressure, and body temperature of patients. However, L 90 and L eq were significantly correlated with HR and HRV of patients, at both daytime and night-time, while higher L 10 were obtained with higher HR, particularly at night-time. Keywords: hospital acoustics, noise control, noise effects, general wards 1. Introduction It has been widely recognised that acoustic environment plays an important role in the healthcare setting. World Health Organization (WHO) [1] suggested that the noise level should not exceed 35 dba in therapy room or hospitalization area. Similarly, Chinese national standard [2] advised the limit of equivalent noise level in ward were 45 dba during daytime and 40 dba during night-time. However, a large number of studies indicated that noise level in hospitals rarely meet these guidelines and noise is often on the top list of complaints by patients and staff [3, 4]. To investigate influence of exceeded noise level on patients physiological and psychological states, several studies have been conducted in ICU wards. Vital parameters of critical patients, including blood pressure, heart rate and respiratory frequency can be affected by excessive noise [5-9]. Noise generated by medical devices 1

2 and staff activities were found positively and significantly associated with increased heart rate and blood pressure [7, 9]. However, many previous studies only concentrated on ICU ward. Less attention has been foucused on the acoustic environment in general departments and lacked in-depth considerations on other room acoustic characters beyond noise level. Besides, most of hospitalized patients during common treatments are fully conscious, hence they could be more sensitive to noise than critical patients. previous study conducted by the authors in a Chinese general hospital indicated that primary noise sources in general ward were distinctly different from ICU ward [10]. Although medical equipment was not the primary noise source and has slight contribution to noise level of general ward, higher noise level had still been found in general ward during daytime [11]. Subsequent to these findings, a series of acoustic treatments were planned to reduce the internal noise level of general ward. The aim of this study is to demonstrate the associations of acoustic environment with patients physiological and psychological states in general wards. In this paper, the differences of acoustic environment between normal ward and acoustically refurbished silent ward was compared, through a series of field measurements. The noise influence on patients in the two different wards was evaluated based on a questionnaire survey. Quantitative relation between sound pressure level and patients vital states was explored as well. 2. Methodologies 2.1 Case study site It was decided that the study should be carried out in building and locations that was representative of Chinese general hospital stock, with a range of ward designs, finishes and ages. Oncology department of Yibin 2 nd hospital, which is located in a six-story building in Sichuan, China agree to take part in the study. Four double-bed wards in this department on the 5th floor were chosen as the case study site, including three normal wards and one acoustically refurbished silent ward with the same geometry and similar appearance (figure 1). Walls and floors in the normal wards were hard surfaced, and the suspended ceilings of wards were solid plaster board, without any sound absorbing materials inside of the wards. Single layer glass windows and a wood door in the normal ward also led a poor sound insulation from corridor and outside. In the silent ward, an antibacterial mineral fibre tile with high-performance of sound-absorbing (NRC 0.70) was installed as the ward ceiling. The door and windows of the ward were replaced with a soundproof one, with Rw+Ctr=32 db and Rw+c=24 db respectively. 2.2 Subjects The subjects purposively sampled in this study were patients with hepatocarcinoma sought palliative care. Participants were required to be aged years with clear consciousness, be able to communicate verbally without visual or auditory defects, and have their pain well controlled. The subjects who were eligible to participate in this study were randomly assigned into the normal wards or silent ward. Noise level in the wards and vital signs of patients were recorded synchronously for 24 hours during working days. Patients psychological responses to acoustic environment were also assessed by using questionnaire survey. 2.3 Acoustic measurements To test the sound absorbing performance of the ceiling in the silent ward, reverberation time (RT) in the wards were tested in the condition of unoccupied with door and windows closed. A Bruel and Kjaer 2250 sound level meter and an omni-directional loudspeaker were chosen, and three receiver positions were placed for both silent ward and normal ward. Two Aihua class 1 sound level meters were chosen to record the sound pressure. To avoid interference with general healthcare activities, the meters were hanged at a height of 2.0 m in ward away from the reflecting surfaces as appropriate. 2 ICSV24, London, July 2017

3 As well as statistical sound level, L10 and L90 were used to give approximate indications of impulsive peak noise level and background noise level, respectively. Figure 1: Site-plan of Oncology department (left side) and floor-plan of case study site (right side). 2.4 Physiologic monitoring Patients heart rate (HR) were recorded every minute using a DMS 300-4A Holter Recorder, during the same time period within which the SPL was measured. Heart rate variability was analysed in the time domain using standard deviation of the NN intervals (SDNN). To minimize interference with patients, systolic arterial blood pressure (SABP), diastolic blood pressure (DABP), and mean arterial blood pressure (MABP), were measured and recorded every hour using a Philips G30 Patient Monitor, and basal body temperature (BBT) of patients were measured every 2 hours during daytime ( ). 2.5 Questionnaire survey In order to analyse the relationship between participants perceptions and the field measurements, the questionnaire surveys were administered to patients after physiologic monitoring. Participants were asked to subjectively evaluate the acoustic environment of their ward, such as subjective noise levels, main noise sources and the influence of noises. Most of the questions were designed in the standard 5-point scale for the convenience of data analysis. 2.6 Statistical analysis The statistical software SPSS 22.0 was used to test the patients perception on the acoustic environment and their physiological responses in the two kind of wards. Nonparametric test (kruskalwallis ANOVA) were applied accordingly to test the significance of differences in the questionnaire. Pearson s rank order correlation was used to assess the relationships between noise level and physiological responses. The significance level was set at 5% (p=0.05) for all tests, with * representing p <0.05 and ** representing p<0.01. ICSV24, London, July

4 3. Results A total of 60 participants were involved in the study. The majority of them were male (60.0%), with the age between 39 and 75-year-old. Sixty questionnaires of all the subjects were considered to be effective. Since 24-hour monitoring on blood pressure and body temperature would disturb the sleep of patients, only six of them (three in normal ward and three in silent ward) agreed and completed all the vital parameters tests, including heart rate, blood pressure and body temperature. The rest of 54 participants, including 30 in normal ward and 24 in silent ward were only recorded the heart rate in physiologic monitoring. 3.1 RTs and noise levels A shorter RT can be found at the silent ward (0.30s) compared with the normal wards (0.56s), indicating a relative higher speech intelligibility in the silent ward. On the other hand, lower average noise level could be found in the silent ward, especially in night-time (table 1). L eq declined by 1.8 dba and 5.2 dba during daytime and night-time in the silent ward. Meanwhile, greater changes can be found in the background noise level (L90) compared with the impulsive peak noise level (L10) in the silent ward due to the change of ceiling. As show in figure 2, noise levels increased dramatically at the beginning of daytime (6:00) in both normal ward and silent ward, and decreased gradually at the beginning of night-time (22:00). The peak levels occurred between 6:00 to 18:00, with 65.2 dba in normal ward and 62.1 dba in silent ward, implying the noisiest period is always during working time as expected. Remarkable differences on noise level in the two kind of wards can be found at and , which were the sleeping time for most patient but medical activities in the corridor were continued at these times. The door of silent ward with better sound-insulation performance can significant decrease the noise influence from corridor and extended quiet period for patients sleep. Table 1: L eq, L10 and L90 (dba) in normal ward and silent ward. Normal ward Silent ward Difference L eq L 10 L 90 daytime 61.4± ± night-time 51.7± ± daytime night-time daytime night-time ICSV24, London, July 2017

5 Leq_avg (dba) Normal ward Silent ward 5:00 4:00 3:00 2:00 1:00 0:00 23:00 22:00 21:00 20:00 19:00 18:00 17:00 16:00 15:00 14:00 13:00 12:00 11:00 10:00 9:00 8:00 7:00 6:00 Time Figure 2: Distribution of L Aeq over 24 hours in normal ward and silent ward. 5 Normal ward Silent ward Mean value of evaluation Conversation Sleep Emotion Recovery * ** ** Figure 3: Comparison of noise impacts in various aspects of patients in normal ward and silent ward. 3.2 Influence of noise level on vital parameters According to ECG data recorded by the holter, mean heart rate of silent ward group and normal ward group were 75±11.8 and 83±15.5 during day time, while 67±9.1 and 74±16.6 during nighttime. Relative slowly heart rate with lower standard deviation might suggested that less noise stimulation on patient s autonomic nervous system in silent ward. Table 2 showed the associations of noise level (L eq, L10, L90) with various physiological responses of patients. There were no significant correlations between noise levels and systolic arterial blood pressure (SABP), diastolic blood pressure (DABP) and basal body temperature (BBT), indicated by Pearson correlation coefficients. However, the heart rate (HR) was significantly and positively correlated with Leq, L10, L90, while the heart rate variability (SDNN) was significantly and negatively correlated with Leq, L90. The results of linear regression on noise levels and heart rate showed that increase in equivalent sound level (L eq ) and ICSV24, London, July

6 impulsive peak noise level (L10) was significantly associated with mean value of heart rate (HR) in both daytime and night time at 10-minute intervals. Table 2: Correlations between noise level and physiological parameters during daytime and night-time Daytime Night-time Leq L10 L90 Leq L10 L90 HR N= **.152 **.108 **.154 **.118 *.163 ** SDNN N= ** * * ** SABP N= DABP N= BBT N= N/A 4. Conclusions The study showed that a certain degree of improvement on acoustic environment in the acoustically refurbished silent ward with sound-absorption ceiling and sound-isolation door and windows. RT dropped by 47% and the Leq decreased by 5.2 dba during night-time in the silent ward. Although the equivalent noise level in the silent ward did not meet Chinese national standard, questionnaires provide that the subjective evaluation on noise level decreased, while less negative noise impact on patients conversation, emotion and sleep could be found in the silent ward group. A notable improvement in patients sleep quality due to more sufficient sleep time with less noise disturbance in the silent ward. On the other hand, the mean heart rate of patients was significantly and positively correlated with noise level in the ward. The increasing of equivalent sound level and impulsive peak noise level was significantly associated with mean value of heart rate in both daytime and night time. Therefore, a silent ward condition would be beneficial for physiological and psychological states among hospitalized patients. 5. Acknowledgements The authors would like to express their gratitude to all the participating patients and medical staff at Yibin 2nd hospital for their cooperation in this study. The financial supports were given by Armstrong and by Chinese National Natural Science Foundation ( ). REFERENCES 1 Organization, W. H. and Organization, W. H. Guidelines for community noise, WHO, Geneva, (1999). 2 Lau, S. Code for Design of Sound Insulation of Civil Buildings GB , (2010). 3 Ryherd, E. E., Waye, K. P. and Ljungkvist, L. Characterizing noise and perceived work environment in a neurological intensive care unit, The Journal of the Acoustical Society of America, 123 (2), , (2008). 6 ICSV24, London, July 2017

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