The study is limited in that we studied units in non-federal hospitals of more than 99 average daily census in urban areas. Smaller, rural and federal hospitals may use different designs and have a different frequency of desirable characteristics. The design did not allow for examining every unit, thus the degree to which design differences within a single institution may be understated. The study design did not allow for including other design aspects (e.g., acoustical tile, air filtration, grab-bars, sitting stations in hallways, and artwork) noted by AHRQ as improving outcomes (AHRQ, 2007
A strength of this study was reliance on personal measurement rather than reliance on architectural plans. Although unit leaders supplied us with schematic pictures or blueprints, in no case was the printed design fully implemented. The most common deviations were conversions of double to single rooms, conversion of patients' rooms to storage or work areas, addition of viewing glass, and computing stations in corridors.
Opportunity for improvement
The results show that there is opportunity for improvement on almost every AHRQ design variable studied with the exception of hand hygiene. A wide gap exists in desirable characteristics between ICUs and M-S units, indicating that greater emphasis should be placed on M-S unit improvement.
Among the designs, the "spokes, no end station" had the longest distances, worst visibility, and fewest private rooms. This design is one that should require much scrutiny before being adopted in new designs. Although others (Hendrich et al., 2004
; Page & Page, 2004
) have noted that parallel corridors often require more walking, this was not true in our study of ICUs. We believe this discrepancy is because of (a) the tendency to place supplies and charting materials within patients' rooms, (b) the placement of multiples of the same work area along the inner supply rectangle, and (c) the relatively small unit size. In contrast, the parallel corridor design on large M-S units was found to have among the longest walking distances. Our recommendation is to consider the potential interaction of bed capacity with configuration in future research.
Based on the large variation of characteristics such as number of beds, distance to supplies, charting, and waste disposal within each design category, we do not recommend that design configuration be used as an unadjusted variable. For example, a great difference probably exists in the amount of walking required on a "parallel-corridor" unit that serves 46 patients in private rooms with only one nursing station versus a parallel-corridor unit that serves 24 patients and has provisions for charting in each room.
Relationship of IOM-cited design categories and study classifications
We did not note any courtyard or duplex designs. No unit met all of the criteria of a simple open (Nightingale) form because no unit was only a completely open ward. In many units that did have placement of glass-walled rooms across from nursing station/staff work space (e.g., surrounded design) the service areas were behind the nursing stations, not located off the unit as defined in the simple open design. The "U shape" designs we noted were not simple open design because not all patients were in wards.
No corridor (continental) designs specified as having four to six beds per room were noted. The "embedded design" was similar in that rooms were placed along corridors of various configurations (squares, rectangles, triangles, and combinations thereof) but different in that nursing stations, work areas, and other support areas were placed at many locations around the unit. The IOM-cited radial design has characteristics much like our "surrounded" and "U-shaped" categories in that all include a greater opportunity to view every patient but in most not every patient could be seen from the nursing work area. The double corridor (racetack) was not noted, although it has many similarities to the "parallel corridor" category. The chief difference was that in the "parallel corridor" units, we did not find a single nursing station. At least two were present in other situations and many ends of corridors and patients' rooms had been converted to stations. In a few cases, additional supply rooms were created from what had been patients' rooms at the ends of corridors.
Two configurations that have not been described before are "off beds" and "more than one configuration." These unit types deserve special consideration in future studies. We noted that the "off beds" design usually resulted in greater walking distances for nurses assigned to the off-beds corridor than those of nurses assigned to the basic design area. The difference was because of the need to return to the basic-design area for supplies and charting. For example, one ICU had a surrounded design on one floor (the original ICU) and a half-parallel corridor on another floor (opened to respond to increased ICU demand). Nurses were assigned regularly between the two areas and some supplies could only be obtained from the original unit because of inadequate storage on the expanded portion. Unit leaders told us that the presence of more than one design was usually because of fiscal or census pressures.
One recommendation for researchers interested in the role of nurse labor on patient outcomes is to explore how unit design elements can be operationalized as risk adjustments. Variation within hospitals leads us to recommend that any risk adjustment be made on a unit, not hospital or service, basis. All investigators face the challenge of determining if the resources studied in this project and those identified by IOM leaders and other safety initiatives are clustered. If design clusters exist, the cluster may exert more influence on outcomes than any single element. A new paradigm for studying nurse-sensitive outcomes could emerge.
Although new building programs are subject to many design standards, the question about what to do with the many units that will not be remodeled or replaced soon remains. Although design features such as carpeting may be added relatively easily, others, such as private rooms, are more difficult to obtain within the limitations of a fixed-wall environment, especially if high bed demand exists. Some features could be attained at only moderate expense; e.g., increase visibility by rehanging doors.
Identifying priorities for these actions within a resource-constrained health care system is necessary. Future researchers should provide comparisons of resource investments by outcome. Our observation that personnel on units had already started to change the physical environment indicates that staff members have begun to seek solutions. What is missing is research that can show estimates not only of how these changes may influence outcomes but also how multiple design elements influence one another. Nurse researchers have a vital role in informing hospital and nursing administrators as well as funders about this topic. Although architects, system designers, and others have important roles in determining hospital design, nurse researchers bring special insight into identifying clinical and workforce issues that may influence the utility of any design and, ultimately, patient outcomes.