Objectives:

To evaluate the differences in environmental sound, illumination and physiological parameters in the Boekelheide Neonatal Intensive Care Unit (BNICU), which was designed to comply with current recommendations and standards, as compared with a conventional neonatal intensive care unit (CNICU).

Study Design:

Prospectively designed observational study.

Result:

Median sound levels in the unoccupied BNICU (37.6 dBA) were lower than the CNICU (42.1 dBA, P<0.001). Median levels of minimum (6.4 vs 48.4 lux, P<0.05) and maximum illumination (357 vs 402 lux, P<0.05) were lower in the BNICU. A group of six neonates delivered at 32 weeks gestation showed significantly less periodic breathing (14 vs 21%) and awake time (17.6 vs 29.3%) in the BNICU as compared to the CNICU.

Conclusion:

Light and sound were both significantly reduced in the BNICU. Care in the BNICU was associated with improved physiological parameters.

Introduction

Forty years ago, neonatal medicine was an emerging pediatric specialty with a primary goal of improving the survival of premature neonates. In the early 1970s, the majority of neonates delivered at 24 to 26 weeks of gestation died.¹ Recent data indicate that 60 to 80% of these infants currently survive.² With this improvement, much attention has been directed toward the quality of survival. This has included the implementation of methods to minimize the neurodevelopmental sequelae of prematurity and the potential adverse effects of conditions in the neonatal intensive care unit (NICU).³

In the 1980s, Als⁴ was the first to describe a method for the assessment of the behavioral state of the preterm neonates. This method was then used to restructure care activities and minimize stress on the infant. Care modified in this manner was associated with improved short-term outcomes;^{5, 6} however, data regarding the long term benefits have been more difficult to document, as reported by Symington in a meta-analysis of outcomes related to developmental care.⁷

Investigators have been unable to establish the specific link between developmental interventions in the NICU and a reduction in adverse long-term neurodevelopmental consequences. The work of Graven⁸ makes a compelling argument that given the immature state of brain development of neonates less than 30 weeks gestation and the active process of neuronal migration, the unregulated NICU environment can be expected to have harmful consequences. Noise, light and painful stimuli interfere with the neonate's ability to sleep, a complex process that is absolutely required for normal neuronal migration and brain development.

The objective of this paper is to report the preliminary findings of a comprehensive research evaluation of the impact of the new single family room Boekelheide Neonatal Intensive Care Unit (BNICU) at Sanford Children's Hospital in Sioux Falls, SD, USA upon the outcome of care. This paper will specifically address the change in the NICU environmental sound and illumination in relationship to a single family room facility designed in accordance with the recommendations and standards for neonatal ICU design⁹ as compared with a conventional NICU. Preliminary physiological findings for a small group of neonates who were hospitalized in the conventionally designed facility (CNICU) and the BNICU are also reported.

Methods

The CNICU at Sanford Children's Hospital was built in the late 1970s using the typical construction of the era with multiple babies in a single large room.¹⁰ The unit was modified in 1986, resulting in the floor plan, as shown in Figure 1. With the addition of five private rooms (Figure 1), the total capacity was 40 babies with an area of 7700 ft².

Figure 1.

Floor plan of the CNICU at Sanford Children's Hospital. Rectangular boxes represent bed/incubator locations. Dashed lines represent countertops. Numbers indicate bed locations for the two groups of neonates in the pneumogram study.

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Planning for the BNICU began in 2002 with occupancy in June 2006. The unit is comprised of 45 rooms with a total capacity of 58 babies and occupies an area of 27 000 ft². Ten rooms are equipped for twins and one room is equipped for triplets. The planning involved hospital administrators, architects, biomedical engineers, neonatologists, nurses, hospital staff from all disciplines and members of a parent advisory committee. The design process included site visits to recently completed facilities and the involvement of consultants in the fields of illumination and sound control. Sound-reducing flooring and ceiling acoustical panels were trialed in the CNICU prior to construction. The primary goal was to design a NICU that complies with the neurodevelopmental needs of preterm neonates.⁹ The floor plan is shown in Figure 2 and photographs of a single family room are shown in Figure 3, Figure 4, Figures 5.

Figure 2.

Floor plan of a single family room with an exterior window in the BNICU. Cardiorespiratory monitors are mounted to the headwall to the right of the patient bed.

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Figure 3.

Photograph of the room demonstrated in Figure 2. Photograph by George Heinrich.

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Figure 4.

Photograph of the head wall of a single family room with electronic monitors and supply exchange cart to the right of the incubator.

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Figure 5.

Photograph of the nursing work area in a single family room. At the far left is the glass door with privacy curtain leading to the main corridor of the NICU.

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A comprehensive research program for evaluation of this new facility was designed in 2004. This included a 6-month baseline measurement period in the CNICU between November 2005 and May 2006 and a study period in the BNICU between November 2006 and May 2007. Sound and illumination reported in this paper were recorded in the two unoccupied NICU facilities in June 2006. Measurements were recorded only once in the BNICU rooms equipped for twins or triplets.

Sound measurements for the bed locations in the CNICU and the rooms in the BNICU were performed when neither unit was occupied by patients or staff. Sound measurements were performed in each room at the location of the incubator with the dosimeter microphone suspended 160 cm above the floor.

Continuous sound measurements for individual neonates were performed either inside a closed Giraffe incubator (Giraffe Omnibed, Ohmeda Medical, Laurel, MD, USA) or at the head of the bed, depending upon the needs of the infant at the time of recording. The dosimeter microphone was positioned so as to project above the level of the mattress by supporting the wire in a stack of cotton sponges 2 inches thick. This apparatus was placed at the side of the mattress in the incubator, or on the mattress in an open bed, approximately 25 cm from the neonate's ear.

All measurements of sound were performed and analyzed using a Larson Davis Noise Dosimeter Model 706 and Blaze Analysis Software (Larson Davis Inc., Provo, UT, USA). Recordings of environmental sound in the two units were discrete measurements of the equivalent continuous sound level (average sound level, L_eq) measured after the dosimeter readings stabilized in the desired location. Continuous sound recordings performed in incubators or beds included the L_eq and the sound level that was exceeded 90% of the time (L₉₀). All continuous recordings were made at 1 s intervals. All measurements used the A-weighted decibel scale (dBA) with slow recording frequency and an exchange rate of 5 s.¹¹

Illumination was measured at each bed location in the CNICU and in the BNICU on an open table (height=95 cm) with the window shades closed using an Extech Instruments EasyView Digital Light Meter Model EA30 using footcandles (lm ft^-2) as the unit of measurement. Continuous recordings of illumination were made using an Extech Datalogging Light Meter with PC Interface Model 401036 at 1-min intervals (Extech Instruments Corp., Waltham, MA, USA). Footcandles were converted to lux (lm m^-2) using the formula lux=footcandles 10.76391.¹²

Illumination was measured in the CNICU under the only two possible circumstances, with all bedside overhead lights off and on. Illumination was measured in the BNICU under four possible circumstances of lights off and one, two and three banks of indirect overhead lights on. Illumination was also measured inside a covered Giraffe incubator (cover from Children's Medical Ventures, Pittsburgh, PA, USA) in rooms with the shades closed but with the artificial lights on. Measurements of illumination for the staff work area were taken in the usual clinical circumstances of having the overhead lights off in the CNICU. In the BNICU, these measurements were made with the light over the staff work desk on and with overhead lights off, and with one, two and three banks of overhead lights turned on. Continuous 1-min recordings of natural illumination were made on the window ledge of rooms on the north, west and south exterior rooms and the north interior rooms of the BNICU with all window shades open. These recordings were repeated with window film (NV-15, 3M Corp., St Paul, MN, USA) between the illumination sensor and the window. Illumination was also measured inside an incubator with the light sensor facing in the directions that a baby's eyes might face in the described areas (facing the window, the ceiling and the interior door).

All equipment used in this investigation was certified by the National Institute of Standards and Technology (NIST, Gaithersburg, MD, USA) on an annual basis. The dosimeters were recalibrated weekly throughout the baseline and study periods.

To compare physiological parameters for a convenience sample of neonates who were hospitalized in both the CNICU and the BNICU, two 6-h pneumogram recordings^{13, 14, 15} were performed at the same time of the day and within a time period of 8 days with one recording in each NICU. The overall research program and this project were approved by the Sanford University of South Dakota Medical Center Institutional Review Board. Informed consent was obtained from the parents for the pneumogram recordings. Continuous digital recordings of heart rate, respiratory rate and oxygen saturation were obtained using a Respironics Smart Monitor, and they were scored using Synergy v1.2.1 software (Respironics Inc., Murrysville, PA, USA). All recorded events were reviewed and verified by a trained pneumogram technician and a research nurse with experience in pneumogram scoring. Awake time was calculated by subtracting scored active and quiet sleep time from the total tape duration. Percent periodic breathing, with apnea of 6 to 11.9, 12 to 14.9 and 15 s duration, was recorded. Periodic breathing was defined as three or more episodes of apnea of 3 s duration interrupted by <20 s of normal breathing. In addition, events of bradycardia to a heart rate of <80 beats per minute for >10 s and desaturation of <80% for >10 s were recorded. Mixed events were classified only once under the primary category of apnea, bradycardia or desaturation. Simultaneous measurements of sound and illumination were recorded as previously described.

Preliminary results of data for in-bed continuous sound recordings for neonates in the CNICU and BNICU are provided. Median sound levels for each of six clinical situations are provided in each NICU as follows: room air in an open bed, nasal cannula oxygen in an open bed, room air in a closed Giraffe incubator, nasal continuous positive airway pressure (NCPAP) in an open bed, NCPAP in a closed Giraffe incubator and high-frequency oscillatory ventilation (SensorMedics, Model 3100A, Yorba Linda, CA, USA) in a closed Giraffe incubator.

Statistical analysis was performed by the principal investigator with the input of a consulting statistician with SPSS PC software, version 14 (SPSS Inc., Chicago, IL, USA).

Results

All sound and illumination meters were tested under standardized conditions and were found to have coefficients of agreement of 0.99 for the illumination meters and 0.98 for the sound meters.¹⁶

Sound measurements were performed in 34 bed locations in the CNICU and 40 bed locations in the BNICU. These measurements were obtained in the open room, not inside a bed or incubator. Data were excluded for two isolation rooms in the BNICU, because airflow characteristics and sound levels were different from that in the remaining rooms. Figure 6 shows the frequency distribution of the sound levels measured in the two facilities. These data were not normally distributed, so median values with 25th to 75th percentile ranges are reported. Non-parametric statistical analysis was performed using the Mann–Whitney test.¹⁶ The median L_eq for the CNICU was 42.1 (39.2 to 42.7) dBA and for the BNICU 37.6 (36.5 to 38.6) dBA (P<0.001).

Figure 6.

Histograms illustrating the distribution of L_eq (sound intensity) measured in the BNICU and the CNICU.

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Illumination was measured in 35 bed locations in the CNICU and 31 in the BNICU. A comparison of the frequency distribution of levels of illumination in the CNICU and the BNICU may be found in Figure 7. Median (25th to 75th percentile) values for minimum illumination in the CNICU were 48.4 (36.6 to 77.5) and 6.4 (5.3 to 9.6) lux for the BNICU (P<0.05). Values for maximum illumination in the CNICU were 402.0 (347.9 to 474.1) lux compared with 357.3 (329.6 to 409.0) lux in the BNICU (P=0.05). Intermediate median values in the BNICU for one and two banks of overhead lights were 78.5 (67.0 to 95.0) and 191.6 (166.0 to 206.0) lux. Levels of illumination inside a covered incubator ranged from 0 lux with the lights off to 2 lux with all three banks of room lights on.

Figure 7.

From top to bottom, histograms illustrating the distribution of measurements of illumination in the BNICU with three, two, one and no banks of lights on and in the CNIUC with the lights on and off.

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Data for minimum task lighting for staff are illustrated in Figure 8. Median minimum illumination was 18.8 (14.8 to 25.5) lux in the CNICU and 72.1 (39.8 to 141.0) lux in the BNICU (P<0.05). These increased to 101.1 (75.3 to 199.1), 158.2 (127.0 to 237.8) and 243.2 (193.7 to 294.9) lux with one, two and three banks of overhead lights on.

Figure 8.

Histograms illustrating the distribution of measurements of illumination for staff work areas in the BNICU with three, two, one and no overhead light on and in the CNICU with the overhead lights off.

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Maximum values for illumination of the window ledges were 18 761, 9816 and 5672 lux for the west, south and north windows. North interior rooms maintained levels of 21 lux throughout the day. Maximum levels of illumination inside the incubator are demonstrated in Table 1. The table also gives estimated levels of illumination following the application of window film using the following linear regression equation: illumination with film=0.164 (illumination without film)+81.2 (r²=0.949, P<0.01).¹⁶

Table 1 - Levels of illumination by exterior window and position of neonate (estimated illumination with window film in place).

Full table

A total of nine neonates participated in the pneumogram study. Sound and illumination data reported for these neonates were recorded in the occupied nurseries in each neonate's bed or incubator, whereas the results described above were obtained in the two facilities when not occupied. Detailed evaluation of the data indicated that two distinct groups of neonates were included. The first group of three neonates had a mean gestation at birth of 25.10.7 weeks and had their first pneumogram performed at a postnatal age of 10.22.2 weeks (bed positions are indicated by 1 in Figure 1). In this group of three, the mean L_eq measured in the bed in the CNICU was 53.9 (median=53.6) dBA and it was 60.8 (median=64.7) dBA in the BNICU. The mean L₉₀ was 43.1 (median=45.5) dBA in the CNICU and 51.8 (median=47.5) dBA in the BNICU. Two of these three neonates were cared for in open cribs and one in a Giraffe incubator in both units. None of the differences in sound, illumination or the physiologic parameters were statistically significant.

The second group of six neonates had a mean gestation of 32.00.2 weeks at birth and had their first pneumogram recorded at a postnatal age of 2.00.8 weeks (bed positions are indicated by 2 in Figure 1). The mean L₉₀, measured in the infant's bed, was 47.4 (median=47.2) dBA in the CNICU and 41.5 (median=40.0) dBA in the BNICU (P=0.01), but L_eq was not significantly different (CNICU: mean=59.3, median=59.1 dBA; BNICU: mean=60.6 dBA, median=57.9 dBA). Four of these neonates received care in Giraffe incubators and two in open beds in the CNICU. All neonates received care in open cribs in the BNICU. Periodic breathing decreased from 20.9 to 14.1% (P<0.001), and awake time decreased from 28.3 to 17.6% (P=0.023). Illumination showed a trend toward a reduced level with 17.7 lux in the CNICU and 3.2 lux in the BNICU (P=0.08).

To provide a basis for comparison of the sound levels for the pneumogram study, the following preliminary data are presented. Data for 24 h (in bed) sound recordings of different neonates in the CNICU indicated median L_eq levels of 49.6 dBA in an open crib on room air, 51.1 dBA for neonates in an open crib on nasal cannula oxygen and 51.6 dBA in a closed Giraffe incubator on room air. Median L_eq values for three different neonates in these same clinical conditions in the BNICU were as follows: 43.6, 45.7 and 47.3 dBA, respectively. Recordings of neonates who required respiratory support in the CNICU had median L_eq sound levels of 55.7 dBA on NCPAP in an open crib, 64.0 dBA on NCPAP in a closed Giraffe incubator and 54.0 dBA on high-frequency oscillatory ventilation in a closed Giraffe incubator. Median L_eq values for the same clinical situations in the BNICU were 55.0, 56.3 and 57.3 dBA, respectively.

Discussion

This report contains the first results of a comprehensive evaluation of a single room NICU facility designed to comply with the current recommendations and standards³ for NICU design. The data indicate that the unoccupied CNICU complied with the most recent recommendations of an L_eq of less than 45 dBA.¹⁷ With attention to architectural detail, sound load in the BNICU was reduced by more than 3 dBA, which represents 50% of the load in the CNICU. This was documented in spite of previous attempts to dampen noise in the CNICU, which would have reduced the measurable effect. Sound levels in the occupied BNICU recorded in the pneumogram study were much higher than these levels, but in this study, no attempt was made to change the manner in which care was provided in the new facility.

A significant reduction in the level of illumination for neonates and staff was documented. Levels of illumination in both units were quite low, and the difference is probably of minimal clinical significance. A qualitative difference not indicated by the data is that all illumination in the BNICU was indirect¹⁷ as opposed to the direct overhead fluorescent illumination in the CNICU. Additionally, the data clearly indicate that environmental lighting can be effectively controlled through the use of supplemental incubator covers.

The results regarding illumination of staff work areas are of concern. Current recommendations for work areas in the NICU include levels of 2000 lux for procedures and 1500 to 2500 lux at the work plane or 300 to 500 lux at the eye for basic care tasks.¹⁷ All BNICU single rooms had levels less than these standards. The low levels of illumination combined with the decreased environmental noise could have the unintended result of impairing the ability of the staff to maintain their vigilance during 12-h night shifts.¹⁸ A project regarding this topic is currently being conducted.

Window ledge illumination measurements were performed because external windows were not a factor in the CNICU. Over half of the rooms in the BNICU have windows in the exterior wall (Figure 3). These data were obtained by the end of June when west-facing rooms had direct sun exposure in the afternoon. If the neonate is inside an incubator and facing the window, light exposure is much greater than the recommended 600 lux¹⁷ in all but exterior rooms in the north. In response to these observations, light-reducing window film has been applied. This addition has reduced the exposure of neonates to recommended maximum levels except in the rooms in the west in which the use of the window shades will be necessary. Seasonal variation in natural illumination continues to be investigated in the BNICU.

The ability to draw meaningful conclusions regarding neonatal physiological parameters investigated in the pneumogram study is limited by the small number of subjects who could be enrolled at the time of moving to the new BNICU. In comparisons where statistical differences were not found, the power of the study was too low to confidently accept a conclusion of no difference.¹⁹

In the pneumogram study, the median L_eq for the smaller neonates was less in the CNCIU than in the BNICU. The median L_eq for the larger neonates was essentially unchanged. These comparisons were confounded by differing clinical conditions for the same neonates at the two time periods of recording; however, the baseline median for the smaller neonates in the CNICU and the median values for both groups in the BNICU are much greater than the preliminary data obtained for continuous in-bed recordings of neonates in these two facilities. One might speculate that noise levels in the BNICU were greater than that in the CNICU because of the activity associated with moving to the new unit and the staff learning about the new environment and equipment. It is encouraging that the L₉₀ was 40.0 dBA in the larger neonates in the BNICU. This indicates that low levels of sound load can actually be achieved in this facility.

In spite of the limitations of the pneumogram study, when one considers the entire group of nine infants, illumination and 8 of the 10 of the physiological parameters improved in the BNICU. Further, awake time significantly decreased in the larger neonates by an amount that could approach more than 2.5 h per day. These improvements occurred in the absence of a reduction in the sound load. These data are compelling, especially when one considers the importance of sleep in sensory neuronal development.⁸

The preliminary in-bed data presented for comparison of the sound data from the pneumogram study are of interest. The contribution of equipment to the sound load to which a neonate is exposed is clearly demonstrated by the fact that an empty room in the BNICU had a median L_eq of 37.6 dBA and a neonate in an open crib had a median L_eq of 43.6 dBA, but with the addition of NCPAP or high-frequency ventilation, median levels were greater than 55.0 dBA. Sound levels with respiratory support were virtually the same in both the CNICU and the BNICU. Clearly, if reducing adverse environmental factors, including sound, is important in the subsequent development of premature neonates, steps must be taken to explore methods by which equipment noise can be reduced so as to take full advantage of the benefits of the single family room architectural design described in this report.

Conclusion

These data indicate that the design of the new single family room in the BNICU was successful in significantly reducing the potential sound and illumination levels to which preterm babies are exposed. Unanticipated results of the design include the finding that neonates could be exposed to extremely high levels of natural illumination in exterior rooms. Additionally, the low levels of illumination in staff work areas combined with low sound levels could impair the ability of the staff to maintain their vigilance during 12-h night shifts. The physiological data strongly suggest improved physiological stability and improved sleep time.

Much remains to be learned regarding outcomes and the mechanisms through which single room design impacts care. The unanticipated results of this investigation demonstrate the need for each institution to evaluate its own outcomes. The authors hope that these findings will serve to assist those who plan to construct new NICUs in the future.

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Acknowledgments

This work was supported by grants from the following organizations: the Sanford Health System, the Sanford Health Research Foundation and the Foundation for the Advancement of Medical Education and Research of the Sanford School of Medicine.