The design of intensive care units (ICUs) is increasingly recognized as a critical factor influencing patient outcomes. In recent years, evidence-based design has driven significant changes in ICU architecture, most notably the transition from multi-bed patient rooms (MPRs) to single-bed patient rooms (SPRs) [1,2]. This shift has been motivated by the potential benefits of SPRs, such as reduced nosocomial infections, improved patient privacy, and enhanced family involvement [2,3]. Various studies have explored the relationship between ICU design and patient outcomes, emphasizing the significant impact of architectural features on mortality and morbidity rates. For example, Leaf et al. [4] demonstrated that ICU rooms with high visibility from nursing stations were associated with lower patient mortality, highlighting the critical role of direct patient observation. This finding suggests that improved visibility in SPRs may facilitate faster detection of clinical deterioration and prompt interventions. Notably, the transition to SPRs has been associated with various advantages for both the healthcare system and patients. For instance, SPR design has been associated with lower rates of delirium among ICU patients, a key factor in improving patient outcomes and reducing the length of hospital stays [5]. From a cost perspective, Sadatsafavi et al. [3] demonstrated that the financial savings from reduced nosocomial infections in SPRs significantly outweigh the increased construction and operational costs.

However, concerns have been raised regarding the potential drawbacks of SPRs, such as increased patient isolation, which can complicate care coordination and monitoring. Additionally, the physical separation inherent to SPRs may impair situational awareness among staff, leading to delayed response in emergencies [1,4,6]. Interestingly, Pettit et al. [7] reported that in certain patient populations, such as trauma patients, ICU room placement did not significantly affect mortality rates after adjusting for patient acuity. Notably, before statistical adjustment, patients assigned to high-visibility rooms had higher mortality rates than those in low-visibility rooms.

In recent years, the introduction of SPR-ICUs in South Korea has marked a departure from traditional MPR-ICUs [8]. However, in South Korea, few studies have examined the long-term operation of SPR-ICUs staffed by dedicated intensivists. Jung et al. [9] reported a reduction in infection rates following the remodeling of a mixed-room ICU into an SPR-ICU. However, differences in baseline characteristics between the pre- and post-renovation groups complicate the interpretation of these findings. Therefore, it is essential to evaluate and report the clinical outcomes associated with ICU design changes. This study aims to assess the clinical improvements observed in newly implemented SPR-structured ICUs compared to traditional MPR-ICUs.

The study highlighted potential clinical improvements in SPR-structured ICUs compared to MPRs. Jung et al. [9] found that room privatization in ICUs significantly reduced the incidence of clinical infections, including bacteremia and pneumonia. This underscores the importance of consulting infection control specialists to determine the appropriate number of isolation rooms. During the coronavirus disease 2019 (COVID-19) pandemic, discussions in South Korea emphasized the need for appropriate isolation structures in ICUs [17]. Although the country had previously dealt with the Middle East Respiratory Syndrome outbreak [18], those cases were largely concentrated in a few medical facilities. In contrast, COVID-19 revealed the need for adequate isolation infrastructure across healthcare institutions nationwide. The pandemic also initiated discussions regarding the design of single-patient isolation rooms, addressing challenges such as limited isolation spaces, resource constraints, and patient transfer difficulties required for maintaining isolation [19,20]. At the time, no ICUs in South Korea were composed entirely of SPRs. However, some hospitals began operating single-patient isolation rooms as a prototype for SPRs, leading to the adoption of SPR-based designs for ICUs in newly constructed hospitals.

To assess nosocomial infections at each facility using the Korean National Healthcare-associated Infection Surveillance System [21] criteria, data were requested from infection control departments. However, access to detailed patient-specific nosocomial infection data, including cases involving multidrug-resistant organisms, was restricted in two hospitals due to legal concerns surrounding patient privacy and data security. These restrictions limited the depth of analysis on individual patient outcomes, highlighting the challenges of retrospective infection surveillance research in a legally constrained environment.

Adequate staffing is a critical factor in delivering effective patient care. Various studies have highlighted the significant impact of nursing staff and intensivists on ICU mortality rates. The Society of Critical Care Medicine Taskforce on ICU staffing [22] emphasized that adequate intensivist staffing is crucial for ensuring the quality of patient care and safety, as well as supporting education and staff well-being. They further cautioned that high staff turnover or declining care quality may indicate overworked personnel, underscoring the need to monitor intensivist-to-patient ratios to prevent burnout. Similarly, Lee et al. [23] demonstrated that optimal nurse-to-patient and intensivist-to-patient ratios significantly reduce ICU mortality. Additionally, a study conducted across 69 ICUs in the United States [24] found that lower bed-to-nurse ratios were associated with decreased annual ICU mortality rates.

ICU design also significantly influences organizational efficiency and clinical outcomes. Guidelines [25] emphasize the importance of creating a healing environment by addressing factors such as noise control, natural lighting, ergonomic design, and infection control. However, SPR may inadvertently contribute to increased nurse fatigue and reduced visibility [4,5], potentially impacting patient care. SPRs require nurses to attend to patients in physically separate spaces, increasing walking distances, reducing the capacity to monitor multiple patients simultaneously, and heightening physical and mental strain [6,26,27]. This fragmentation of care may contribute to delayed responses in emergencies or missed early warning signs of clinical deterioration, particularly in high-acuity settings. Additionally, limited familiarity with SPR workflows may further exacerbate fatigue and reduce efficiency compared to the well-established routines of nursing teams in MPR environments [28,29].

This study explored the impacts of ICU architecture by comparing two distinct designs: a linear layout versus a centralized layout and an ICU composed entirely of SPR versus a mix of SPRs and MPRs. However, the adoption of SPR-based ICUs in South Korea remains limited due to their relatively recent introduction. Consequently, existing SPR-structured ICUs do not fully align with international guidelines. For example, although ICUs at site A consisted entirely of SPRs with glass-fronted walls, their design restricts nurses’ ability to observe patients effectively unless they are near the patient rooms. This limitation hinders efficient monitoring of patient conditions from a distance. In contrast, many advanced healthcare systems employ design strategies that enhance visibility and optimize nursing efficiency [26,28]. A common approach involves incorporating recessed walls with glass windows between adjacent rooms, enabling nurses to directly observe patients and continuously monitor vital signs without frequent movement between rooms. On the other hand, the MPR-based design at site B offers notable advantages in terms of nursing efficiency. Its centrally located nursing station provides a clear view of most patient areas, allowing nurses to monitor patients more effectively, respond more promptly, and maintain better situational awareness.

This study has some limitations that may have influenced the interpretation of its findings. First, significant differences in hospital structure, patient demographics, and institutional policies across the three hospitals complicated direct comparisons of clinical outcomes. PSM was applied to address these differences; however, residual bias may persist due to unmeasured confounding factors, such as socioeconomic status, chronic conditions, and hospital-specific operational practices. Second, patients assigned to SPRs may have been selectively placed based on factors such as clinical severity, isolation requirements, or specific diagnoses. This selection process could introduce bias in mortality comparisons despite matching efforts and logistic regression analysis. Additionally, the unequal distribution of SPR and MPR patients across hospitals, particularly the smaller sample size at site C, may have reduced statistical power and generalizability. Third, while the study demonstrated an association between SPRs and reduced mortality rate, it did not establish causality. Other variables, such as increased nurse-to-patient ratios, may have contributed to improved patient outcomes. We did not adjust for differences in nurse-to-patient or physician-to-patient ratios across hospitals. These ratios are subject to frequent fluctuations throughout the day, making it difficult to reflect real-time clinical conditions using average values without potential bias. Instead, this investigation qualitatively described staffing patterns and included ICU bed counts to illustrate institutional differences in resource allocation. Demonstrating a meaningful difference in staffing intensity of the SPR compared to the MPR model would require a significant disparity in nurse-to-patient or physician-to-patients ratios and the availability of at least two comparable ICU cohorts comprised exclusively of either SPR or MPR models. However, due to the absence of such directly comparable cohorts, we were only able to reference findings from other studies. Furthermore, the study primarily focused on ICU mortality as the main outcome, with a limited assessment of variables such as ventilator use duration, delirium, and functional recovery, which are clinically important and patient-centered indicators. Delirium data were not included in our primary analysis, though we recognize their importance. Fourth, the study did not include important metrics such as patient functional recovery, satisfaction of patient and their families, or quality of life, limiting insight into SPRs’ broader impact on patient-centered care. Fifth, the economic analysis also lacked an evaluation of the long-term cost-effectiveness of SPR implementation, including potential savings from reduced infections and improved clinical outcomes relative to the initial construction and operational costs. Finally, the retrospective study design and limited study period restricted the evaluation of certain variables, including specific microbial pathogens and antibiotic resistance profiles. Legal and data security concerns further restricted access to patient-specific nosocomial infection data, limiting infection-related analyses. These limitations highlight the complexity of evaluating the impact of ICU design on clinical outcomes and emphasize the need for future research using larger, prospective studies that incorporate broader clinical, economic, and patient-centered metrics.

Future research should broaden the range of clinical, operational, and patient-centered outcomes. The following recommendations are proposed: Research should evaluate a broader range of outcome measures, including patient functional recovery, satisfaction of patients and their families, and stress levels among healthcare providers. Comparative investigations on various SPR configurations, including visibility-enhanced layouts, patient acuity, and staffing levels, should be conducted to explore strategies for improving operational efficiency while maintaining patient privacy and safety. Furthermore, studies should incorporate additional endpoints, such as re-admission rates, ventilator-free days, continuous renal replacement therapy-free days, nutritional support adequacy, and discharge disposition. Moreover, detailed economic analysis examining long-term cost-effectiveness, including potential savings from reduced infections and improved clinical outcomes, should be conducted to inform healthcare policy and investment decisions. Additionally, exploring the effects of SPR implementation on ICU staff stress levels, job satisfaction, and burnout rates could be considered [6,24,30-32].

In conclusion, transitioning from MPR to SPR in ICU architecture demonstrated a protective effect by reducing the ICU mortality rate. The analysis suggests that the positive outcomes associated with SPRs result from a complex interplay of room design, operational efficiency, and institution-specific factors.