Abstract
Noise and excessive, unwanted sound in the Pediatric Intensive Care Unit (PICU) is common and has a major impact on patients’ sleep and recovery. Previous research has focused mostly on absolute noise levels or included only staff as respondents to acknowledge the causes of noise and to plan for its reduction. Thus far, the suggested interventions have not ameliorated noise, and it continues to serve as a barrier to recovery. In addition to surveying PICU providers through internet-based software, patients’ families were evaluated through in-person interviews utilizing a pretested instrument over 3 months. Families of patients admitted for more than 24 h were considered eligible for evaluation. Participants were asked to rank causes of noise from 1 to 8, with eight being highest, and identified potential interventions as effective or ineffective. In total, 50 families from 251 admissions and 65 staff completed the survey. Medical alarms were rated highest (mean ± standard deviation [SD], 4.9 ± 2.1 [2.8-7.0]), followed by noise from medical equipment (mean ± SD, 4.7 ± 2.1 [2.5-6.8]). This response was consistent among PICU providers and families. Suggested interventions to reduce noise included keeping a patient's room door closed, considered effective by 93% of respondents (98% of staff; 88% of families), and designated quiet times, considered effective by 82% (80% of staff; 84% of families). Keeping the patient's door closed was the most effective strategy among survey respondents. Most families and staff considered medical alarms an important contributor to noise level. Because decreasing the volume of alarms such that it cannot be heard is inappropriate, alternative strategies to alert staff of changes in vital signs should be explored.
Keywords: Intensive Care Unit, Intensive Care Unit staff and families, sound reduction interventions, survey
Introduction
Noise is defined as “any sound that may produce an undesired physiological or psychological effect in an individual or group.”[1] When such sound is produced in an environment that must be conducive to healing, it hinders recovery. Literature suggests that noise leads to physiological responses experienced by patients including higher heart rates, respiratory rates and also sleep deprivation.[2,3] In addition, noise is noted to cause higher levels of stress in the staff, which may impair their ability to concentrate on their tasks and care for the critically ill.[4] The process of caregiving in the Pediatric Intensive Care Unit (PICU) if not orchestrated well leads to a greater potential of error and unfavorable results.
Despite an increased emphasis on the need for noise reduction in intensive care settings, a number of studies published in the past few years have found that sound levels in the ICU continue to be louder than the World Health Organization noise recommendations.[5,6] Patient families and staff surveys previously conducted in the ICUs in the US and Europe have reported noise to be disruptive and uncomfortable with better patient satisfaction in noise-reduced environments.[7,8]
Two categories of people are in the PICU typically staff and patients’ families. Any quality improvement project that does not take into consideration the perception of both these groups does not have a potential for success. We believe that the reason previous researchers have not been able to reduce noise in the PICU is a lack of stakeholders’ input. The present study was designed to identify causes of noise in the PICU, identify interventions that would help decrease the noise and thereby the stress in the PICU, and compare the perceptions of staff and patients’ families on noise and modifications that could reduce it.
Methods
A survey of staff was done as part of quality improvement efforts in the PICU, with ethical approval for the survey of patients’ families obtained from the Mayo Clinic Institutional Review Board.
The PICU at Mayo Clinic in Rochester, Minnesota, is a 16-bed mixed medical-surgical unit. A descriptive-comparison design was used to examine the multiple sources of noise and the interventions that could reduce noise in patients’ rooms, as well as the ICU as a whole. Noise levels in the PICU were measured using a Dosimeter at a day before starting the surveys at 08:00 am-11:00 am, 01:30 pm-03:00 pm, and 09:00 pm-06:00 am in the PICU general work area with patient room open and closed.
We created a 28-question survey (see Appendix A), keeping in mind the most common sources of noise in the PICU and the modifications used or that can be used to reduce noise pollution, based on clinical experience. For surveys, internet-based software Research Electronic Data Capture (RedCap was developed by an informatics core at Vanderbilt University with ongoing support from NCRR and NIH grants) was utilized. Study data were collected and managed using RedCap electronic data capture tools hosted at Mayo Clinic.[9] RedCap is a secure, web-based application designed to support data capture for research studies, providing:
An intuitive interface for validated data entry,
Audit trails for tracking data manipulation and export procedures,
Automated export procedures for seamless data downloads to common statistical packages, and
Procedures for importing data from external sources.
The staff took an internet-based survey through RedCap software; the families were interviewed in person. This study was conducted from 1st August to 31st October, 2014.
All staff members, including nurses, physicians, and para-clinical staff were asked to participate in the PICU provider survey (n = 65). For the PICU family survey, families of patients who stayed in the PICU more than 24 h (n = 50) were considered eligible and were approached for an in-person survey. Patients who stayed <24 h in the PICU were excluded from the study. The patients’ families gave oral consent for study participation. Survey questions asked respondents to rank the noise levels from 1 to 8 on a Likert scale, with eight being the highest among the sources, which included alarms, medical equipment, environmental noises, pagers, staff conversations, telephones, family conversations, television, and radio. Participants also ranked the frequency of noise levels from these sources.
Next, the questions focused on the interventions and their effectiveness, ranging from very effective to not at all, in reducing excessive noise levels. These interventions included staff education, posting signs on the doors alerting people about noise, turning pagers and phones to vibration mode, turning down alarm to the lowest appropriate volume, assuring alarms were set to appropriate limits, turning down room telephone ringers, lowering voices during staff conversations, closing patients’ doors when appropriate, and providing a designated quiet time in the PICU with dimmed lighting. Questions regarding patient sleep, as well as family sleep, were asked, and the effect of noise level on recovery from illness was examined. The in-person survey questions were collected on paper and then uploaded into RedCap software. Data received from staff and patients’ families were subjected to statistical analysis through JMP software (SAS Institute Inc., SAS Campus Drive, Cary, North Carolina 27513, USA). Descriptive analysis was performed of the various contributors of noise and their frequency. Effective modifications or interventions were compared among responses of staff and families. The Chi-square test was used for categorical variables; the t-test was used for continuous variables.
Results
Pediatric Intensive Care Unit dB levels
When measured by a Dosimeter, noise levels in our PICU averaged between 49 and 59 dB [Table 1]. During all hours of the day, the general work area had the most noise; the patient's room with its door closed had the least. The loudest time of day was 01:30 pm-03:00 pm.
Table 1.
Noise dosimeter recordings for 1 day in various locations of the Pediatric Intensive Care Unit
| Location, dB | Time period | ||
|---|---|---|---|
| 08:00 am-11:00 am | 01:30 pm-03:00 pm | 09:00 pm-06:00 am | |
| General work area, median (range) | 56 (51-59) | 52 (51-58) | 54 (49-57) |
| Patient room door closed, mean | 53 | 45 | No recording done |
| Patient room door open, mean | 49 | 55 | 52 |
Causes of noise
The survey was completed by 50 families, out of 251 admissions, and 65 staff members out of 176 total staff members. Among all respondents, medical alarms were rated the greatest contributor to excessive noise (mean ± standard deviation [SD], 4.9 ± 2.1 [2.8-7.0]), with medical equipment noise being the second highest (mean ± SD, 4.7 ± 2.1 [2.6-6.80]) [Table 2]. While these trends were consistent between staff and families, they were at variance with regard to the contribution of staff conversation; providers ranked it higher than patients’ families (mean ± SD, 5.2 ± 1.9 [3.3-7.1] vs. 2.0 ± 1.6 [0.4-3.6], P < 0.001). Other differences were seen in noise created by pagers and environmental sounds. Telephone ringers were ranked higher by staff than the patients’ families. Television and radio sounds and family conversations were rated the lowest causes.
Table 2.
Comparison of various sources of noise in the Pediatric Intensive Care Unit
| Sources | Valuesa, mean ± SD | P | ||
|---|---|---|---|---|
| All (n = 115) | Staff (n = 65) | Patient’s families (n = 50) | ||
| Alarms | 4.9±2.1 (2.8-7.0) | 5.8±1.6 (4.2-7.4) | 3.8±2.1 (1.7-5.9) | <0.001 |
| Medical equipment | 4.7±2.1 (2.6-6.8) | 5.5±1.8 (3.7-7.3) | 3.7±2.0 (1.7-5.7) | <0.001 |
| Environmental noise | 3.7±2.0 (1.7-5.7) | 4.5±1.8 (2.7-6.3) | 2.7±1.8 (0.9-4.5) | <0.001 |
| Pagers | 2.5±1.5 (1.0-4.0) | 3.8±1.4 (2.4-5.2) | 1.7±1.2 (0.5-2.9) | <0.001 |
| Staff conversations | 3.8±2.4 (1.4-6.2) | 5.2±1.9 (3.3-7.1) | 2.0±1.6 (0.4-3.6) | <0.001 |
| Telephones | 2.7±1.6 (1.1-4.3) | 3.5±1.5 (2.0-5.0) | 1.6±1.1 (0.5-2.7) | <0.001 |
| Family conversations | 2.4±1.6 (0.8-4.0) | 2.9±1.6 (1.3-4.5) | 1.7±1.4 (0.3-3.1) | <0.001 |
| Television/radio | 2.0±1.5 (0.5-3.5) | 2.6±1.7 (0.9-4.3) | 1.4±0.9 (0.5-2.3) | <0.001 |
aNoise values range from 1 to 8 on the Likert scale, with 1 being the lowest and 8 being the highest amount, SD = Standard deviation
Interventions to reduce noise
Among the various suggested interventions to reduce noise, keeping the patient's room door closed was considered effective by 93% of respondents (P = 0.003), followed by designated quiet times by 82% [Table 3]. Staff and families agreed about the effectiveness of silencing inappropriate alarms (P = 0.93) and decreasing the volume of the phone ringer (P = 0.54). Among staff, 71% reported feeling that more staff education is required; only 50% of the families considered it effective (P = 0.02), and posting signs on doors was considered effective by 66% of families and 43% of staff (P = 0.01).
Table 3.
Effective interventions to reduce noise in the Pediatric Intensive Care Unit
| Interventions mentioned by respondents | Survey respondents, n (%) | Pa | ||
|---|---|---|---|---|
| Total (n = 115) | Staff (n = 65) | Patient’s families (n = 50) | ||
| Educating staff | 71 (61) | 46 (71) | 25 (50) | 0.02 |
| Posting signs that encourage quiet | 61 (53) | 28 (43) | 33 (66) | 0.01 |
| Setting pagers to vibrate | 69 (60) | 32 (49) | 37 (74) | <0.01 |
| Decreasing number of inappropriate alarms | 92 (80) | 52 (80) | 40 (80) | 0.93 |
| Decreasing volume of phone ringer | 65 (56) | 38 (59) | 27 (54) | 0.54 |
| Lowering voices of staff conversations | 89 (88) | 58 (90) | 31 (62) | <.01 |
| Closing patient doors | 108 (93) | 64 (98) | 44 (88) | 0.02 |
| Creating quiet time in PICU | 94 (82) | 52 (80) | 42 (84) | 0.64 |
| Providing visual feedback | 37 (57) | 37 (57) | NA | NA |
aP value of responses of staff versus patients’ families, NA = Not available, PICU = Pediatric Intensive Care Unit
Discussion
Two groups of people typically occupy the PICU at any given time-staff and patients’ families. As such, any quality improvement project that does not take into consideration the perception of both groups has the potential for nonattainment and bias.
Factors in the Pediatric Intensive Care Unit responsible for noise
Alarms
In this comparative survey, we evaluated the perceptions of noise by patients’ families and PICU staff. We found similarities in the factors implicated by both groups. Medical alarms and medical equipment were identified as the loudest disruptive noises leading to discomfort. Ugras and Oztekin,[10] who studied a Neurosurgical Unit in Turkey, have reported a relation between medical alarms and patient discomfort previously. They measured patient perception of environmental and nursing factors leading to sleep disturbances and concluded that alarm sounds were the major environmental noise contributor. Bridi et al.[11] reported that “the alarms of equipment intended to protect patients may, in fact, lead to increased noise within the unit and consequently lead to alarm fatigue, distraction, and interruption of the workflow.” Thus, the process of caregiving in the PICU is optimized only under conditions in which distractions and stress are minimized; in the presence of excessive noise, the care process is disrupted and error prone.
Communication
In our study, we found inter-staff communication a considerable cause of the noise pollution in the PICU among staff responders, a finding consistent with previous surveys of patients in a critical care setting in the United Kingdom.[12] Those investigators found staff communication and telephone conversations as the main reasons for noise and as significantly affecting the sleep of patients in the ICU. Interestingly, in our survey, patients were relatively unconcerned about staff conversation as a noise etiology than the staff.
Akansel and Kaymakçi[13] studied the effects of ICU noise on patients and found that patients closest to the nursing station were most affected by noise because of noise-creating activities performed by staff and conversations held among staff. Background noise has been established as a negative impact in the working environment and the performance of staff, including exposure to high numbers of alarms, which also leads to alarm fatigue.[14,15]
Suggested interventions to reduce noise
Interventions to reduce noise in the ICU include actions that can be taken by staff and actions related to hospital design.[16,17] The staff should be educated to be considerate since even minor conversations in the corridors can add to the background noise level. Behavior modification has been shown as possible[18] for staff and is effective in reducing noise levels in the ICU. Thus, such modification should be advocated strongly.
Alarms
Deterioration in a patient's physiological parameters that trigger alarms in monitoring equipment should alert the nurses and the physicians; however, in a closely monitored setting like the ICU, these alarms can be detrimental to the sleep of patients and their families. Earlier intervention by nursing staff to silence alarms has been suggested by Way et al.,[19] which may be possible with staff education. Turning off alarms may be unsafe and inappropriate; yet, alternative strategies to alert staff regarding changes in a patient's vital signs should be explored. Changing the position of the medical alarms from the rooms to the nursing station may be a viable option. Richardson et al.[12] suggested the use of soft ear plugs and eye masks to minimize sleep disturbances caused by medical alarms and equipment.
Medical equipment
Medical equipment such as intravenous pumps — Another major source of noise in the patient's room — Need to be modified or renewed to reduce background sounds. Johansson et al.[20] have stated that “it is unacceptable for machines to be positioned just behind the patient's head and produce high noise levels and loud alarm signals.”
Closing doors
Previous studies also have discussed strategies such as moving television speakers closer to the listener to minimize disturbance to others, closing patients’ doors, and performing shift-change reports behind closed doors.[16,17] The intervention most frequently suggested by the patients’ families and the staff in our survey was to close the patients’ doors to minimize the disturbance due to noise from outside and adjoining rooms, including television and radio sounds. Although studies have shown that such interventions as a designated quiet time and door closing do not help ICU staff achieve the sound-level objective of the World Health Organization or the US Environmental Protection Agency,[6] these are still some of the most commonly applied and suggested interventions to dampen sounds in the ICU.
Sound proofing of the doors and walls is another consideration. Krueger et al.[21] found that the average noise level decreased significantly after reconstruction, but it was still above the recommended limits. Single rooms are the best option for all critically ill patients but are seldom practical, which makes noise reduction in the rooms a necessary intervention. This can be achieved through making the ceilings and walls sound absorbent, along with action plans for modifying staff behaviors.[22]
Limitations of our study would include measuring the noise levels on 1 specific day. Noise in the PICU can vary by days and patient load of the unit. Also, since our study is survey-based, there can be an element of response bias among our study population.
Conclusion
In summary, noise in health care settings leading to increased tension among the staff and the patients has been a topic of concern for the past three decades. The strategies to cut down the noise pollution in critical care settings have not been successful until date. Although physical design of ICUs can contribute considerably to noise reduction, subtle human factors and practices may have a larger role when design changes become prohibitive. Technological advancements such centralized alarms or for mobile, wearable alarm monitoring system by nurses should be promoted. In addition, behavior modification for staff is effective in reducing noise levels in the ICU and should be advocated strongly.
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
Appendix A: Survey
Noise Reduction and Sleep Enhancement in the Pediatric Intensive Care Unit (PICU)
This survey is done for research purposes to gather data on the perception of families and patients in the PICU concerning various aspects of noise levels in the PICU. Data gathered from this survey will be used to create appropriate interventions to reduce noise levels in the PICU and improve the overall quality of care for our patients. Your participation in this survey is voluntary and please understand that your current and future employment, educational and/or medical care at Mayo Clinic will not be affected by whether or not you participate. Specifically, your care will not be jeopardized if you choose not to participate.
For how long have you or your loved one in the PICU
□ 24-48 h
□ 2 days-1 week
□ 1 week-1 month
□ >1 month
The following section gathers data on your perception of the contribution of various sources to noise in the PICU
Please rate the following items based on their contribution to noise on the unit with ‘8’ being the largest contributor and ‘1’ being the smallest contributor.
Each number may be used only once (Please circle the number which you feel most appropriately reflects the noise contribution).
Alarms
8 7 6 5 4 3 2 1
Medical Equipment (Ventilators, IV pumps, Hugs Tags Alarms, etc.)
8 7 6 5 4 3 2 1
Environmental Noise/Equipment (Carts, Floor Cleaner, Sinks, Doors, Tube station, Computers, etc.)
8 7 6 5 4 3 2 1
Pagers of medical/nursing staff
8 7 6 5 4 3 2 1
Staff conversations
8 7 6 5 4 3 2 1
Telephones
8 7 6 5 4 3 2 1
Family conversations
8 7 6 5 4 3 2 1
TV/Radio
8 7 6 5 4 3 2 1
How frequent do you feel the following contribute to noise levels in the PICU?
Alarms
Very Frequent Frequent Infrequent Not at all Unsure
Medical Equipment (Ventilators, IV pumps, Hugs Tags Alarms, etc.)
Very Frequent Frequent Infrequent Not at all Unsure
Envirionmental Noise/Equipment (Carts, Floor Cleaner, Sinks, Doors, Tube station, Computers, etc.)
Very Frequent Frequent Infrequent Not at all Unsure
Pagers
Very Frequent Frequent Infrequent Not at all Unsure
Staff conversations
Very Frequent Frequent Infrequent Not at all Unsure
Telephones
Very Frequent Frequent Infrequent Not at all Unsure
Other family conversations
Very Frequent Frequent Infrequent Not at all Unsure
TV/Radio
Very Frequent Frequent Infrequent Not at all Unsure
The following section focuses on interventions to reduce noise in the PICU
How effective do you feel the following interventions would be at reducing noise in the PICU?
Education of the staff in the PICU
Very effective Effective Ineffective Not at all Unsure
Posting signs on the doors in to the unit alerting staff regarding noise
Very effective Effective Ineffective Not at all Unsure
Turning pagers/portable phones to vibrate
Very effective Effective Ineffective Not at all Unsure
Turning down/off inappropriate alarms
Very effective Effective Ineffective Not at all Unsure
Turning down telephone ringers
Very effective Effective Ineffective Not at all Not sure
Lowering voices of staff conversations
Very effective Effective Ineffective Not at all Unsure
Closing patient doors when appropriate
Very effective Effective Ineffective Not at all Unsure
Designated quiet time with dimmed lights
Very effective Effective Ineffective Not at all Unsure
The following section gathers data on your perception of how much PICU noise has affected your or your loved ones sleep quality and recovery
How frequent do you feel the noise levels in the PICU has affected your (or your loved ones) sleep quality
Very Frequent Frequent Infrequent Not at all Unsure
How significant do you feel noise level in the PICU has affected your (or your loved ones) recovery from the illness
Very significant Significant Minor effect Not at all Unsure
The following section focuses on your comments to improve noise reduction and sleep enhancement
Do you have suggestions for noise reduction interventions in the PICU?
Do you have suggestions for sleep enhancement strategies in the PICU?
References
- 1.Mazer SE. Hear, hear. Assessing and resolving hospital noise issues. Health Facil Manage. 2005;18:24–9. [PubMed] [Google Scholar]
- 2.Choiniere DB. The effects of hospital noise. Nurs Adm Q. 2010;34:327–33. doi: 10.1097/NAQ.0b013e3181f563db. [DOI] [PubMed] [Google Scholar]
- 3.Kudchadkar SR, Aljohani OA, Punjabi NM. Sleep of critically ill children in the pediatric intensive care unit: A systematic review. Sleep Med Rev. 2014;18:103–10. doi: 10.1016/j.smrv.2013.02.002. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 4.Morrison WE, Haas EC, Shaffner DH, Garrett ES, Fackler JC. Noise, stress, and annoyance in a pediatric intensive care unit. Crit Care Med. 2003;31:113–9. doi: 10.1097/00003246-200301000-00018. [DOI] [PubMed] [Google Scholar]
- 5.Cranmer K, Davenport L. Quiet time in a pediatric medical/surgical setting. J Pediatr Nurs. 2013;28:400–5. doi: 10.1016/j.pedn.2013.02.028. [DOI] [PubMed] [Google Scholar]
- 6.Stafford A, Haverland A, Bridges E. Noise in the ICU. Am J Nurs. 2014;114:57–63. doi: 10.1097/01.NAJ.0000446780.99522.90. [DOI] [PubMed] [Google Scholar]
- 7.Jongerden IP, Slooter AJ, Peelen LM, Wessels H, Ram CM, Kesecioglu J, et al. Effect of intensive care environment on family and patient satisfaction: A before-after study. Intensive Care Med. 2013;39:1626–34. doi: 10.1007/s00134-013-2966-0. [DOI] [PubMed] [Google Scholar]
- 8.Salandin A, Arnold J, Kornadt O. Noise in an intensive care unit. J Acoust Soc Am. 2011;130:3754–60. doi: 10.1121/1.3655884. [DOI] [PubMed] [Google Scholar]
- 9.Harris PA, Taylor R, Thielke R, Payne J, Gonzalez N, Conde JG. Research electronic data capture (REDCap) — A metadata-driven methodology and workflow process for providing translational research informatics support. J Biomed Inform. 2009;42:377–81. doi: 10.1016/j.jbi.2008.08.010. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 10.Ugras GA, Oztekin SD. Patient perception of environmental and nursing factors contributing to sleep disturbances in a neurosurgical intensive care unit. Tohoku J Exp Med. 2007;212:299–308. doi: 10.1620/tjem.212.299. [DOI] [PubMed] [Google Scholar]
- 11.Bridi AC, Louro TQ, da Silva RC. Clinical alarms in intensive care: Implications of alarm fatigue for the safety of patients. Rev Lat Am Enfermagem. 2014;22:1034–40. doi: 10.1590/0104-1169.3488.2513. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 12.Richardson A, Allsop M, Coghill E, Turnock C. Earplugs and eye masks: Do they improve critical care patients’ sleep? Nurs Crit Care. 2007;12:278–86. doi: 10.1111/j.1478-5153.2007.00243.x. [DOI] [PubMed] [Google Scholar]
- 13.Akansel N, Kaymakçi S. Effects of intensive care unit noise on patients: A study on coronary artery bypass graft surgery patients. J Clin Nurs. 2008;17:1581–90. doi: 10.1111/j.1365-2702.2007.02144.x. [DOI] [PubMed] [Google Scholar]
- 14.Siebig S, Kuhls S, Imhoff M, Gather U, Schölmerich J, Wrede CE. Intensive care unit alarms — How many do we need? Crit Care Med. 2010;38:451–6. doi: 10.1097/CCM.0b013e3181cb0888. [DOI] [PubMed] [Google Scholar]
- 15.Hannibal GB. Monitor alarms and alarm fatigue. AACN Adv Crit Care. 2011;22:418–20. doi: 10.1097/NCI.0b013e318232ed55. [DOI] [PubMed] [Google Scholar]
- 16.Joseph A, Rashid M. The architecture of safety: Hospital design. Curr Opin Crit Care. 2007;13:714–9. doi: 10.1097/MCC.0b013e3282f1be6e. [DOI] [PubMed] [Google Scholar]
- 17.Montague KN, Blietz CM, Kachur M. Ensuring quieter hospital environments. Am J Nurs. 2009;109:65–7. doi: 10.1097/01.NAJ.0000360316.54373.0d. [DOI] [PubMed] [Google Scholar]
- 18.Kahn DM, Cook TE, Carlisle CC, Nelson DL, Kramer NR, Millman RP. Identification and modification of environmental noise in an ICU setting. Chest. 1998;114:535–40. doi: 10.1378/chest.114.2.535. [DOI] [PubMed] [Google Scholar]
- 19.Way RB, Beer SA, Wilson SJ. Whats that noise.Bedside monitoring in the emergency department? Int Emerg Nurs. 2014;22:197–201. doi: 10.1016/j.ienj.2014.01.001. [DOI] [PubMed] [Google Scholar]
- 20.Johansson L, Bergbom I, Waye KP, Ryherd E, Lindahl B. The sound environment in an ICU patient room — A content analysis of sound levels and patient experiences. Intensive Crit Care Nurs. 2012;28:269–79. doi: 10.1016/j.iccn.2012.03.004. [DOI] [PubMed] [Google Scholar]
- 21.Krueger C, Schue S, Parker L. Neonatal intensive care unit sound levels before and after structural reconstruction. MCN Am J Matern Child Nurs. 2007;32:358–62. doi: 10.1097/01.NMC.0000298131.55032.76. [DOI] [PubMed] [Google Scholar]
- 22.Monsén MG, Edéll-Gustafsson UM. Noise and sleep disturbance factors before and after implementation of a behavioural modification programme. Intensive Crit Care Nurs. 2005;21:208–19. doi: 10.1016/j.iccn.2004.12.002. [DOI] [PubMed] [Google Scholar]