Factors involved in the aerosol transmission of infection and control of ventilation in healthcare premises

A Review of the Research Literature on Evidence-Based Healthcare Design

Objective:

This report surveys and evaluates the scientific research on evidence-based healthcare design and extracts its implications for designing better and safer hospitals.

Background:

It builds on a literature review conducted by researchers in 2004.

Methods:

Research teams conducted a new and more exhaustive search for rigorous empirical studies that link the design of hospital physical environments with healthcare outcomes. The review followed a two-step process, including an extensive search for existing literature and a screening of each identified study for the relevance and quality of evidence.

Results:

This review found a growing body of rigorous studies to guide healthcare design, especially with respect to reducing the frequency of hospital-acquired infections. Results are organized according to three general types of outcomes: patient safety, other patient outcomes, and staff outcomes. The findings further support the importance of improving outcomes for a range of design characteristics or interventions, including single-bed rooms rather than multibed rooms, effective ventilation systems, a good acoustic environment, nature distractions and daylight, appropriate lighting, better ergonomic design, acuity-adaptable rooms, and improved floor layouts and work settings. Directions for future research are also identified.

Conclusions:

The state of knowledge of evidence-based healthcare design has grown rapidly in recent years. The evidence indicates that well-designed physical settings play an important role in making hospitals safer and more healing for patients, and better places for staff to work.

Intervals before tuberculosis diagnosis and isolation at a regional hospital in Taiwan

Background/Purpose

Nosocomial tuberculosis (TB) infection is still a problem in many Taiwanese hospitals. The objectives of this study were to explore the intervals before TB diagnosis and isolation at a regional hospital in Taiwan, and to provide useful knowledge to hospitals for the purpose of TB infection control.

Methods

From 2002 to 2005, we included a total of 343 patients with culture-positive pulmonary TB in a regional hospital in Southern Taiwan for this study. Their medical records were reviewed, and the time intervals between patient-hospital contact points and isolation were recorded.

Results

Of 343 culture-positive pulmonary TB patients, the majority were male, over 40 years old, and unemployed. The mean interval between the first admission and isolation was 20.5 days (median, 2.0 days). The mean intervals between the first admission from outpatient clinics, emergency department and hospitalization and suspected TB were < 1 day, 6.07 days and 25.53 days, respectively. The mean accumulated exposure time was 0.35 days, 0.61 days and 10.09 days in outpatient clinics, the emergency department and hospitalization, respectively; 75.5% of patients had their diagnosis confirmed at the chest department of the department of internal medicine.

Conclusion

Delayed diagnosis was most likely in the case of hospitalized patients and least likely in outpatient clinics. Delayed diagnosis in hospitalized patients also contributed more severely to TB exposure time than others. Enhancing the quality, speed and ability of specialists and physicians to diagnose TB, especially in emergency departments and in hospitalized patients, is essential.

Pandemic preparedness

PURPOSE OF REVIEW

Pandemic influenza remains a threat to world health and will probably result in an overwhelming number of critically ill patients. Preparations should be made now to meet this threat.

RECENT FINDINGS

Limited data are available on which to base preparations. Adequate staffing is crucial to the functioning of an ICU and therefore occupational safety is of central concern. In the absence of knowledge of the method of spread of a pandemic disease, it would seem appropriate to take airborne and contact precautions, and the literature related to this area is reviewed. Methods of recruiting and training additional staff and the issues of bed capacity, stockpiling, triage and ethics are discussed.

SUMMARY

Extensive preparation is needed in advance of an epidemic. This should include occupational safety measures, stockpiling of equipment and drugs, staff training, development of triage policies, and discussion of the limits of duty of care to patients. These preparations take considerable time and therefore these issues should be tackled urgently.

Airflow and droplet spreading around oxygen masks: a simulation model for infection control research

Background

Respiratory assist devices, such as oxygen masks, may enhance the potential to spread infectious aerosols from patients with respiratory infections.

Methods

A technique was developed to visualize exhaled aerosols during simulated patients' use of oxygen masks in a health care setting and tested using the simple, the nonrebreathing, and the Venturi oxygen masks. A smoke tracer was introduced into one of the lungs of the model to enable it to mix with the incoming oxygen and then to be further inhaled/exhaled by the model according to a variety of realistic respiratory settings (14, 24, and 30 breaths per minute, with tidal volumes of 500, 330, 235 mL, respectively) and oxygen supply flow rates (between 6 and 15 liters per minute). Digital recordings of these exhaled airflow patterns allowed approximate distances to be estimated for the extent of the visible exhaled air plumes emitted from each oxygen mask type at these settings.

Results

It was found that the simple, the nonrebreathing, and the Venturi-type oxygen masks produced exhaled smoke plumes over minimum distances of 0.08 to 0.21 m, 0.23 to 0.36 m, and 0.26 to 0.40 m, respectively.

Conclusion

Health care workers may therefore consider any area within at least 0.4 m of a patient using such oxygen masks to be a potential nosocomial hazard zone.

The prospect of pandemic influenza: why should the optometrist be concerned about a public health problem?

BACKGROUND

Optometrists are uniquely placed in the health care field because they provide both services as well as goods to patients. In the event of an influenza pandemic, optometrists may be challenged with a host of issues, including impediments to clinical patient care, manufacture and delivery of ophthalmic devices, and maintaining business continuity and infection control.

OVERVIEW

This report reviews pandemic influenza, the effect of a pandemic event on business survival, and response measures for the primary eye care provider. The ethical and legal issues surrounding control of a pandemic influenza and the prospect of telemedicine as a form of social distancing are also discussed.

CONCLUSIONS

Knowledge of the pharmacologic and nonpharmacologic measures to control a pandemic influenza will help prepare the eye care provider for addressing challenges to patient care and business continuity in the face of a highly contagious disease. Understanding the legal and ethical issues that arise during a pandemic event will help optometrists make informed choices as health care professionals and as citizens.

Hospital and community acquired infection and the built environment--design and testing of infection control rooms

Negative-pressure isolation rooms are required to house patients infected with agents transmissible by the aerosol route in order to minimise exposure of healthcare workers and other patients. Housing patients in a separate room provides a barrier which minimises any physical contact with other patients. An isolation room held at negative pressure to reduce aerosol escape and a high air-change rate to allow rapid removal of aerosols can eliminate transmission of infectious aerosols to those outside the room. However, badly designed and/or incorrectly operating isolation rooms have been shown to place healthcare workers and other patients at risk from airborne diseases such as tuberculosis. Few standards are available for the design of isolation rooms and no pressure differential or air-change rates are specified. Techniques such as aerosol particle tracer sampling and computational fluid dynamics can be applied to study the performance of negative-pressure rooms and to assess how design variables can affect their performance. This should allow cost-effective designs for isolation rooms to be developed. Healthcare staff should be trained to understand how these rooms operate and there should be systems in place to ensure they are functioning correctly.

Model answers or trivial pursuits? The role of mathematical models in influenza pandemic preparedness planning

The panzootic of H5N1 influenza in birds has raised concerns that the virus will mutate to spread more readily in people, leading to a human pandemic. Mathematical models have been used to interpret past pandemics and outbreaks, and to thus model possible future pandemic scenarios and interventions. We review historical influenza outbreak and transmission data, and discuss the way in which modellers have used such sources to inform model structure and assumptions. We suggest that urban attack rates in the 1918-1919 pandemic were constrained by prior immunity, that R(0) for influenza is higher than often assumed, and that control of any future pandemic could be difficult in the absence of significant prior immunity. In future, modelling assumptions, parameter estimates and conclusions should be tested against as many relevant data sets as possible. To this end, we encourage researchers to access FluWeb, an on-line influenza database of historical pandemics and outbreaks.