Indoor Climate in Hospitals and Health Effects on Patients

The indoor environment plays an important role in the recovery process of patients. Appropriately designed heating, ventilation and air conditioning (HVAC) systems can improve the patient recovery process, shorten the length of the hospital stay, reduce medical errors and infection rates and improve indoor air quality (IAQ). In addition, an improved indoor environment of a hospital building can reduce costs associated with airborne diseases by up to 20%. What is the state of research on this? A brief overview.

The disinfection robot UVD Robot is an autonomous disinfection robot equipped with UV-C light that kills viruses and bacteria on surfaces and in the air. (Image: businesswire.com)

Covid-19 is changing our expectations of indoor environments. Buildings can play a central role in the spread of disease: It is increasingly clear that the virus spreads primarily indoors. 
Coronavirus infections occur predominantly in family environments and workplaces. In addition to masks and distance rules, good ventilation is therefore also important. Good ventilation of indoor spaces with fresh air is mandatory for good and healthy indoor air. But how does the necessary fresh air get into our buildings?  
Conventional window ventilation is reaching its limits. The narrative of energy efficiency and sustainability, as well as the dense construction of new buildings and sealing measures in the context of renovations, have reduced the uncontrolled natural air exchange to a minimum. As a result, fresh air must be supplied and is usually provided continuously by elaborate building technology without the knowledge of the occupants. (1)

Part 1 covered some basic thoughts on the indoor society’s relationship to air as a food: “Air and Covid-19. One Year of Covid-19: Effects of Indoor Environmental Parameters on Health” (2)
Part 2 examines the impact of indoor environmental parameters on patient medical outcomes through a review of scientific research on indoor air quality in hospital buildings. 
Hospitals are considered hotspots for the transmission of coronavirus, as pointed out by the Robert Koch-Institute in its situation reports, for example. (3) 
This problem is particularly dramatic in heavily occupied rooms such as patients rooms. An analysis from Texas examined studies over the past 20 years on the relationship between indoor climate and health outcomes for patients. (4)

The Importance of the Indoor Climate 

The indoor climate of a mechanically ventilated hospital (5) controls infection rates and influences patient healing processes and overall medical outcomes. Sufficient and hygienically clean air is a basic requirement for a successful recovery process. Therefore, a perfectly functioning room air control system is a prerequisite for this. If natural ventilation is not sufficient for the necessary air exchange, mechanical ventilation is used. With targeted air guidance and one or more fans, it ensures the required air exchange in the room as needed and independently of external influences (wind pressure/temperatures). Due to increasingly airtight construction methods, mechanical ventilation has been on the rise for some time. Modern, energy-saving ventilation systems adapt the air exchange rate to the respective requirements. 

The air exchange rate indicates how often the total air volume of a room or building is exchanged per hour. It can be used for rough dimensioning of a ventilation system. Reference values for this are: 

  • Apartments 0.3 to 0.5 h 
  • Offices 1.0 to 2.0 h 
  • Trains: In the latest Giruno train of the Swiss Federal Railways from Stadler-Rail, there are eleven outside air changes per hour. If there are few passengers sitting on the train, there are seven air changes per hour. In full regional traffic, there are even 16 air changes in one hour in modern trains. 

In hospitals, there are different specifications for the air exchange rate, depending on the functional area (operating room, patient rooms, etc.). 

The importance of the room climate for the healing process of patients was first mentioned by Florence Nightingale in 1859: 

“The very first canon of nursing, the first and the last thing to which a nurse’s attention must be directed, the first essential for the patient, without which everything else you can do for him is nothing, of which I almost said you could leave everything else, is this: KEEP THE AIR HE BREATHES IN AS PURE AS THE OUTSIDE AIR WITHOUT COOLING HIM. But so little thought is given to this. Even where it is thought of at all, the most extraordinary misunderstandings about it prevail. Even when air is admitted into the sickroom or ward, very few people think of where that air comes from. I may come from a corridor into which other wards are ventilated, from a corridor which is always unventilated, always full of gas fumes, food fumes, of various kinds of mustiness; from an underground kitchen, sink, laundry, water closet, or even, as I have myself painfully experienced, from open sewers laden with refuse; and thus the sick room or ward is ventilated, as it is called-poisoned, one should rather say. Always air from outside, and that, too, through the windows, through which the air comes freshest.” (6)

Nightingale thus outlines one of the main issues that healthcare professionals, environmental psychologists, consultants and architects continue to prioritize today – more than ever. The indoor environment controls infection rates and affects the overall outcome of patients. 

Current State of Research 

Appropriately designed heating, ventilation and air conditioning (HVAC) systems can improve patient recovery processes, shorten the length of hospital stays, reduce medical errors and infection rates and improve indoor air quality (IAQ). An improved indoor environment of a hospital building can reduce costs associated with airborne diseases by 9-20%. A review at the U.S. Texas A&M University College Station, Department of Architecture (7) examined those scientific researches since 1998 that investigated how mechanical ventilation systems of a hospital building (including indoor air temperature, relative humidity and other indoor ventilation parameters) affected medical outcomes of patients.  

Of nearly 900 studies, 176 papers were included in this review to understand the relationships between a hospital’s indoor environment and patient health outcomes.  

To determine the relationship between health outcomes and the physical environment, an additional 85 relevant studies were identified that examined parameters such as room size, privacy in the room, interior design of a room, patient control over their environment, music, lighting, sunlight, view out the window to nature, contaminants in the ventilation system, humidity and temperature. Of these studies of the effect of the medical environment on patient outcomes, 7 were related to humidity, 4 to the air filtration system, 4 to the ventilation system and 2 to temperature. (Including increasing outside air exchange, improving filter efficiency, maintaining constant temperature and humidity, increasing positive pressure of OR air). They concluded that there is compelling evidence of a relationship between patient clinical outcomes and the parameters of the built environment.  

Zimring et al. (8) identified a relationship between the hospital’s indoor environment and patient and staff outcomes in relation to four areas:  

  • Reduce staff stress and fatigue and increase effectiveness in the delivery of care 
  • Improve patient safety 
  • Stress reduction and improvement in patient outcomes 
  • Overall improvement in the quality of health care 

Dijkstra et al. (9) summarized the literature on environmental stimuli (e.g. furniture, art, color, nature, plants, gardens, indoor air) and focused on their influence on patient psychological outcomes. Huisman et al. (10) examined hospital interior design and its relationship to medical staff errors, patient falls, infection rates, room quality, comfort, building materials, visual comfort, acoustics, views and privacy. They addressed indoor climate (e.g. ambient temperature, humidity, ventilation strategies and air quality) under the subtopic of safety and security. 

Recommendations

Based on this literature review, temperature, humidity and the indoor ventilation system in hospitals influence various infectious organisms, which then impact patient outcomes. Published results contain conflicting findings, making comparative evaluation difficult due to inconsistencies in experimental design, choice of variables, location and settings, demographics, diseases, patients and types of outcome measures. As a result, it is impossible to make evidence-based decisions about the optimal areas to improve patient-oriented outcomes such as symptoms, morbidity, quality of life, or mortality. These conflicting results of the current research suggest that all indoor environmental parameters associated with the HVAC system need to be measured or included in the comparative analysis of each study. The review also identified avenues for future interdisciplinary collaborative research to quantify the optimal range for indoor environmental parameters considering positive patient medical outcomes.

A few epidemiological studies have been conducted specifically to investigate the appropriate ranges of several indoor environmental parameters (e.g. temperature, humidity, etc.). However, there is little patient-oriented evidence to formulate guidelines for hospitals. Although extensive simulation-based research has been conducted, very little patient-oriented evidence has been obtained. For validation, simulations and experiments need to be correlated by physical measurements. Additional multidisciplinary studies involving researchers, patients, building owners, building managers and maintenance staff are needed to address evidence-based decisions regarding optimal areas to improve patient-centered outcomes. 

Studies that address nosocomial infection rates, the spread of infections within healthcare facilities and associated costs are potential avenues for research. A multidisciplinary study combining available molecular biology tests, advanced computer modeling, experimental testing and field experimental designs could provide evidence to identify optimal temperature ranges and ventilation strategies. It is also necessary to consider these variables as a function of the spaces within a hospital, as each zone has unique occupants and different functions. In addition, the structural variations of infectious agents (i.e. viruses, bacteria and fungi) must be considered separately when studying airborne survival, as they each have different conditions under which they can be optimally suppressed. Finally, the relationships between the Involvement Evaluation Questionaire (IEQ) variables, patient perception of thermal comfort and airborne contamination must be examined. The health effects of ventilation in locations with highly polluted outdoor air and other varying outdoor conditions represent an important area for future research. At the same time, awareness of the ventilation problem and the need for contemporary ventilation concepts in dense buildings should also increase significantly, especially among architects, planners and builders. 


Notes

(1) See, among others:  Thick Air (Part 2) – Indoor Climate and SARS-CoV-2. 

(2) Part 1: Air and Covid-19

(3) https://www.rki.de/DE/Content/InfAZ/N/Neuartiges_Coronavirus/Situationsberichte/Maerz_2021/Archiv_Mrz_2021.html

(4) Shajahan, Amreen et al. (2018).; Effects of Indoor Environmental Parameters related to Building HVAC Systems on Patients’ Medical Outcomes: A Review of Scientific Research on Hospital BuildingsTexas A&M University, Department of Architecture Williamson, Brandon; Texas A&M University, College of Medicine; Indoor Air 10-Dec-2018
https://pubmed.ncbi.nlm.nih.gov/30588679/

(5) In German-speaking countries, the term “maschinelle Lüftung” is used primarily in industrial construction, while in residential construction the term “mechanische Lüftung” is used. 
https://www.baunetzwissen.de/gebaeudetechnik/fachwissen/lueftung/mechanische-lueftung-2466143

(6) Florence Nightingale (1820-1910) was a British nurse and statistician and can be considered a founder of modern Western nursing. 
Nightingale F. Notes on nursing. London, Harrison 1859:59
https://www.bl.uk/learning/timeline/item106499.html
See also: Blog post Following the Tradition

(7) Shajahan, Amreen et al. (2018).; Effects of Indoor Environmental Parameters related to Building HVAC Systems on Patients’ Medical Outcomes: A Review of Scientific Research on Hospital BuildingsTexas A&M University, Department of Architecture Williamson, Brandon; Texas A&M University, College of Medicine; Indoor Air 10-Dec-2018
https://pubmed.ncbi.nlm.nih.gov/30588679/

(8) Roger S. Ulrich, PhD; Craig Zimring, PhD; Xuemei Zhu, BArch, PhD Candidate; Jennifer DuBose, MS; Hyun-Bo Seo, MArch; Young-Seon Choi, MArch; Xiaobo Quan, PhD; and Anjali Joseph, PhD (2008).  A Review of the Research Literature on Evidence-Based Healthcare Design; HERD  Vol. 1, No. 3  HEALTH ENVIRONMENTS RESEARCH & DESIGN JOURNAL
https://www.researchgate.net/publication/49686913

(9) Dijkstra K., Pieterse M., Pruyn A. (2006)., Physical environment stimuli that turn health care facilities into healing environment through psychologically medical effects; systematic review; Journal of Advanced Nursing 2006 Oct; (56(2): 166-81
https://www.researchgate.net/publication/6777106

(10) Huisman E.R. et al. (2012) Healing environment: A review of the impact of physical environmental factors on users
DOI: 10.1016/j.buildenv.2012.06.016


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Jean Odermatt

Prof. Jean Odermatt is sociologist and interior designer. He is a professor emeritus at Bern the University of the Arts (HKB). His research focus is on how interior design can promote the process of recovery.

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