Transmission Based Precautions Literature Reviews. Airborne Precautions

Transcription

1 Transmission Based Precautions Literature Reviews Airborne Precautions April 2008

2 PRINCIPAL RESEARCH QUESTION/OBJECTIVE: Search Strategy Airborne Precautions What precautions can be taken to ensure patients / healthcare workers / visitors safety, from pathogens which are disseminated as aerosols? Search strategy for identification of studies Key Questions 1. What healthcare and human activities can cause an infectious agent to be disseminated as an aerosol into the environment and potentially cause cross transmission or colonisation of patients / healthcare workers / visitors? 2. What precautions can be taken to ensure patients / healthcare workers/ visitors safety, from pathogens which are disseminated as aerosols? 3. What infectious agents are disseminated via aerosols from infected / colonised patients with the potential to cause cross-transmission or colonisation in patients / healthcare workers / visitors? The recommendations and Airborne Precautions a systematic review of the evidence are based on a collation of review and critical appraisal of the scientific evidence identified by search strategies carried out using the above key questions. Further details on each search strategy and results can be supplied on request. Period of publication Strategy key words Airborne Healthcare acquired infection (Full search strategies available Airborne transmission Hospital acquired infection on request) Aerosol transmission Hospital Cross infection Healthcare Nosocomial Occupational transmission Healthcare associated infection Infective agent Healthcare-associated infection Infective pathogen Infective microorganism Speaking Coughing Patient$ Sneezing Healthcare worker$ Healthcare personnel Visitor$ Healthcare activit$ Aerosol Respiratory adj2 infection Infective material Gloves Gown$ Mask FFP3 N95 Eye protection Personal protective equipment Environment Patient placement Single room Cohorting Handwashing Patient Environment Patient transport Infection control Isolation Negative pressure Bacteria Viruses Prions Fungi Mucous membrane Measles Tuberculosis Electronic databases Vericella Zoster MEDLINE X PsycINFO (tick as appropriate) Science Direct EMBASE CINAHL X SIGLE Cochrane Library X Web of Science British Nursing Index X 1

3 Additional Resources (tick as appropriate) References checked for relevant articles Review of abstracts of professional meetings/ conferences Personal libraries consulted Experts consulted (give details if applicable) Handsearching of journals (name relevant journals e.g. Journal of Hospital Infection, Infection Control and Hospital Epidemiology) X Websites CDC X WHO X (tick as appropriate) Department of Health X Scottish Government X HPA X Scottish Government Health Dept. X How many papers found 538 How many papers included 18 (+ 11 guidance documents) How many papers excluded 520 ii) Selection criteria for inclusion of studies Sample All health and social care workers. Outcome measure(s) Other inclusion criteria Language Limitations Interventions to minimise the spread of infections by aerosols. Any study or guidance document not reviewed within the CDC Guideline for Isolation Precautions: Preventing Transmission of Infectious Agents in Healthcare Settings 2007 English language only iii) Quality assessment Study quality assessment The newly published CDC Guideline for Isolation Precautions: Preventing Transmission of Infectious Agents in Healthcare Settings 2007, (Siegel et al., 2007) has been evaluated by five independent reviewers using the AGREE instrument (The AGREE Collaboration, 2001) which is designed to assess the methodological quality of guidelines. The results show the guidelines suitable for adaptation as primary reference source for literature review and formulation of recommendations. A literature search was conducted using HPS ICT search strategies, based on agreed research questions. Identified studies, not already reviewed within the CDC guidelines, were assessed for relevance and critically appraised using SIGN-50 methodology (SIGN, 2004) to determine if additional information or considerations were required for production of transmission based precautions for healthcare settings in NHS Scotland. The methodology for grading the supporting evidence is found on the Evidence Tables including Considered Judgment Section and available from the HPS Infection Control Team on request Category of Recommendation The recommendations have been categorised based on a combination of the system used in the CDC/HICPAC (Siegel et al., 2007) and EPIC 2 National Evidence-Based Guidelines for Preventing Healthcare-Associated Infections in NHS Hospitals in England Category IA - Strongly recommended for implementation and strongly supported by well-designed experimental, clinical, or epidemiologic studies. Category IB - Strongly recommended for implementation and supported by some experimental, clinical, or epidemiologic studies and a strong theoretical rationale. Category IC - Mandatory or required for implementation Category II - Suggested for implementation and supported by suggestive clinical or epidemiologic studies or a theoretical rationale. GPP (Good Practice Point) Is a recommendation for best practice based on the expert opinion or practical experience of the Model Policies Steering Group No recommendation; unresolved issue. Practices for which insufficient evidence or no consensus regarding efficacy exists. 2

4 Data collation and analysis The SIGN 50 methodology including reviewing templates are available from the SIGN website ( The AGREE Instrument which is used for assessment and evaluation of the quality of evidence-based guidelines can be found at 3

5 Table of Contents Search Strategy Airborne Precautions Recommendations Airborne Precautions Airborne Precautions Patient Placement Non Acute Settings Personal Protective Equipment Patient Transport Additional precautions Mycobacterium tuberculosis (TB) Practical Application Resource Implications Airborne Precautions a systematic review of the evidence... 9 Sources of infectious agents... 9 General Principles of Transmission Based Precautions... 9 Airborne transmission... 9 Activities resulting in airborne transmission Infectious Agents transmissible by airborne route Infectious agents transmitted from environmental sources Airborne precautions Patient Placement Personal Protective Equipment Immune status of healthcare workers Organism Specific Considerations Tuberculosis Respiratory Protection for tuberculosis Sputum generating procedures Aerosol generation Severe Acute Respiratory Syndrome (SARS) Noroviruses Setting Specific Considerations Burn Units Paediatrics GP Waiting Rooms and Triage Long Term Care Facilities (Care Homes) Community Care Hand Hygiene Patient Transport Additional precautions Control of the Environment Linen Waste Dishes and cutlery Care Equipment Conclusions Sources of infectious agents General Principles of Transmission Based Precautions Airborne transmission Activities resulting in airborne transmission Infectious agents transmitted from environmental sources Airborne precautions Patient Placement

6 5.7 Personal Protective Equipment Immune status of healthcare workers Organism Specific Considerations Tuberculosis Aerosol generating procedures Infectious agents transmitted from environmental sources Setting Specific Considerations Burns Units Paediatrics GP waiting rooms and triage Long Term Care Facilities (Care Homes) Community Care Hand Hygiene Patient Transport Additional precautions Control of the Environment Linen Waste Dishes and cutlery Care Equipment References

7 1 Recommendations Airborne Precautions Caveat Transmission based precautions are designed to be an adjunct to standard infection control precautions. It is therefore stressed that the nine elements of standard infection control precautions must underpin all health and social care activities. It is therefore assumed for the purpose of this literature review that all standard infection control precautions are being adhered to and therefore do not require specifically addressed within this literature review and associated recommendations. More information on the standard infection control precautions including associated literature reviews is available from the Model Infection Control Policies website: Airborne Precautions Airborne precautions should be applied for patients with known or suspected infections transmissible by the airborne route e.g. pulmonary or laryngeal TB, measles etc. (See Appendix 1 in policy) (Category 1A/1C) Airborne precautions should be continued until cessation of symptoms or according to specific advice relevant to the causative organism. (See Appendix 1 in policy) (Category 1B) 1.2 Patient Placement In acute hospitals, patients requiring provision of care with airborne precautions should be placed in a negatively pressured isolation room; the type of facility currently recommended from the Scottish Health Facilities Building Note 30 is given below. Isolation Suite enhanced single room with positive pressure ventilated lobby and en-suite facilities with extract ventilation If there is not a suitable isolation suite available within the acute setting, the patient should be transferred to another hospital with the suitable facility. (Category II) If this type of facility is not available then patient placement decisions may be subject to local risk assessment and advice from the Infection Control/ Health Protection Team. (Category GPP) 1.3 Non Acute Settings Within non-acute settings e.g. GP waiting rooms etc, there should be appropriate systems such as triage or availability of signage to enable identification, on entry of patients requiring provision of care with airborne precautions on entry. (Category 1A) Patients requiring airborne precautions should be placed in a suitable isolation facility as soon as possible. (Category 1B/1C) If a suitable isolation facility is not available, the patient should be placed in an examination room and requested to wear a surgical mask (if possible) and instructed on the principles of respiratory and cough etiquette and the room left vacant for a period of time afterwards usually 1 hour, to allow a change of air to take place. (Category 1B/1C) 6

8 1.3.4 Once transferred to a suitable isolation suite, the surgical mask may be removed. (Category 1B /1C) 1.4 Personal Protective Equipment An appendix has been attached to the policy which covers the safe donning and removal of PPE to avoid contamination. Respiratory Protection A FFP3 facemask, (conforming to the European Standard EN ) which has been fit tested to the wearer should be donned before entrance to the patient s room in the case of known or suspected infection with the following list and the fit of the mask should be checked prior to entrance into the room. (Category 1B) 1. Tuberculosis (pulmonary; laryngeal (confirmed or suspected) 2. Extrapulmonary (draining lesion) 3. If infectious TB lesions are present and potentially aerosol generating procedures to be performed (irrigation, incision, drainage etc) 4. Smallpox (in all cases and not dependant on immune status of the healthcare worker 1.5 Patient Transport It is recommended that patients requiring care using airborne precautions within acute and community settings should not be moved unless there is a necessary requirement to do so i.e. medical reasons (Category II) If it is necessary to move a patient requiring care using airborne precautions, the patient should be instructed on respiratory hygiene / cough etiquette and asked to wear a surgical mask, if possible. (Category II) If it is necessary to move a patient requiring care using airborne precautions who has skin lesions associated with M tuberculosis, varicella or smallpox, the lesions should be covered to prevent contact or potential aerosolisation of the infectious agent (Category IB) The wearing of a mask by patient transport staff responsible for transport of patients on airborne precautions is not usually required (Category II) 1.6 Additional precautions Some personnel restrictions may have to be put into place for the care of patients on airborne precautions dependant on the immune status of the healthcare worker (if known) and the nature of the infection e.g. measles (Category 1B) Potentially susceptible healthcare workers caring for patients with measles or varicella (chickenpox) should refer to their Organisation s Occupational Health Department immediately for specific advice regarding post-exposure immunisation. (Category GPP) 1.7 Mycobacterium tuberculosis (TB) These recommendations cover aspects of the transmission-based precautions required for the delivery of care to patients with pulmonary or laryngeal TB. This is not an exhaustive list of guidance on infection control aspects of TB, which also includes detail on administrative and engineering controls 7

9 required and separate guidance documents should be referred to for additional disease specific guidance (Jensen et al., 2005, NICE, 2006) A risk assessment for potential drug resistance and HIV should be carried out on all patients with TB as additional precautions may be required and advice sought from Infection Control / Health Protection Team. (Category GPP) If requiring admission to hospital, patients with known or suspected pulmonary or laryngeal TB should be admitted to an isolation suite if possible or transferred to another hospital with suitable facilities. (Category II) If this type of facility is not available then patient placement decisions may be subject to local risk assessment and advice from the Infection Control / Health Protection Team. (Category GPP) Respiratory protection in the form of a FFP3 facemask, (conforming to the European Standard EN ) which has been fit tested to the wearer should be donned before entrance to the patient s room in the case of known or suspected infection with pulmonary or laryngeal TB or extrapulmonary (draining lesion) and the fit of the mask should be checked prior to entrance into the room. (See recommendation 1.4.1) (Category 1B) Aerosol generating or sputum inducing procedures should be carried out in a suitable isolation suite and respiratory protection should be worn. (See recommendations & 1.4.1) (Category 1A / 1C) Information on the duration of airborne precautions for pulmonary or laryngeal TB is included in appendix 1 in the policy 2 Practical Application As the use of airborne precautions has been recommended for some time, no significant change to practice should be required however, the standards set down must be achieved. 3 Resource Implications All resources required for implementing airborne precautions should already be in place. 8

10 4 Airborne Precautions a systematic review of the evidence Caveat Transmission based precautions are designed to be an adjunct to standard infection control precautions. It is therefore stressed that the nine elements of standard infection control precautions must underpin all health and social care activities. It is therefore assumed for the purpose of this literature review that all standard infection control precautions are being adhered to and therefore do not require specifically addressed within this literature review and associated recommendations. More information on the standard infection control precautions including associated literature reviews is available from the Model Infection Control Policies website: Sources of infectious agents Patients, healthcare workers and visitors are potential sources of infectious agents. Individuals can be incubating infectious diseases in a number of forms ranging from active infections to unknown asymptomatic infections or they may be colonised with pathogens either chronically or transiently (Siegel et al., 2007). There are a range of microorganisms that cause infection including bacteria, viruses and fungi. Infections can also be transmitted by prions, which are widely accepted to be an infectious protein molecule. The route of transmission is dependant on the particular pathogen and the range covers blood borne, droplet spread, airborne and contact (direct and indirect) and some pathogens are spread by more than one route. There is a great deal of published literature available describing the modes by which pathogens are spread (Siegel et al., 2007). General Principles of Transmission Based Precautions Transmission Based Precautions is the umbrella term that covers a set of specific infection prevention and control measures that are required to be implemented when patients are either suspected or known to be infected with potentially transmissible infectious agents. The precautions are defined and grouped according to the route of transmission of the particular causative pathogens and are consequently divided into the three main routes of transmission, namely Droplet, Contact and Airborne precautions (Siegel et al., 2007). Transmission Based Precautions should be implemented based on available clinical knowledge, while awaiting actual identification of the causative agent and should be continued either for the duration of illness or while there is still considered a risk of transmission. The guidelines produced will be made available as model polices covering Droplet, Contact and Airborne Precautions each of which will be able to be used independently or more than one set of precautions applied, dependant on the nature of the infectious agent (Siegel et al., 2007) (See appendix 1 in policy). The duration that transmission based precautions are required depends on a number of factors such as patient group affected e.g. immuno-suppressed patients may required a greater duration of precautions due to increased length of viral shedding etc. (Siegel et al., 2007) (See appendix 1 in policy). Airborne transmission The definition of airborne transmission is the spread over distance, of airborne particles of small size (<5µ), which retain infectivity over time and are able to access the respiratory tracts of individuals exposed without necessarily having close contact with the source. Examples of infectious agents which can be transmitted in this way include Mycobacterium tuberculosis (TB) and Varicella Zoster 9

11 virus. In addition there is evidence available that a number of pathogens, normally transmitted by the droplet route such as SARS and influenza, can sometimes form small particle aerosols which have the potential to be transmitted by the airborne route and which are generated during certain aerosol generating procedures, and this therefore has to be considered when deciding on the precautions required (Siegel et al., 2007). Activities resulting in airborne transmission Activities which can result in airborne transmission of infectious agents include human activities such as breathing, coughing, sneezing, talking, laughing etc particularly if the individual is suffering from respiratory symptoms. This can be problematic in some settings e.g. including condition within prisons and shelters such as overcrowding, poor ventilation etc and the general health of the population of these facilities who may be intravenous drug users, alcoholics and have poor nutrition and there a number of reports of outbreaks of tuberculosis within these settings.. In addition, any healthcare activities, which promote production of respiratory secretions such as bronchoscopy, intubation etc may also result in the production of aerosolised infectious agents. (Siegel et al., 2007) Infectious Agents transmissible by airborne route A small number of infectious agents are known to be transmissible mainly by the airborne route, whereas there are other pathogens which can under some circumstances have some airborne transmission component. This led to some researchers proposing that a classification system could be established which would take this into account. The method of classification proposed was that 3 categories could be identified; 1. Obligate which would encompass infectious agents which transmit only through the inhalation of small aerosolised particles (TB). 2. Preferential; which covers infectious agents which can transmit through more than one route but where respiratory exposure to small aerosolised particles is the main route (e.g. measles and Varicella zoster) and a third category of 3. Opportunistic; which would cover pathogens normally transmissible by other routes but which will transmit via aerosols under certain circumstances. (e.g. SARS, noroviruses, influenza etc). This method of classification certainly elucidates the differences of the mode of transmission of different pathogens and perhaps improves the difference in the choice of precautions required for protection of staff, patients and visitors (Siegel et al., 2007). The main infectious agents which are considered airborne are Mycobacterium tuberculosis, rubeola virus (measles) and varicella-zoster virus (chicken pox). In addition there a number of other pathogens which believed to be transmissible by the airborne route under certain circumstance including noroviruses, influenza and SARS and these and the implication in terms of precautions required will be discussed in more detail within this literature review Infectious agents transmitted from environmental sources There are some infectious agents which are transmissible by the airborne route directly from environmental sources but do not usually result in person to person transmission e.g. Bacillus anthracis and Aspergillus spp spores. Activities which can result in dissemination of the spores into the air and thereby accessing the respiratory tract of individuals can occur during construction work. Although this is generally accepted to be the cause of transmission of Aspergillus spp spore, there is one documented case within the CDC Isolation Guidance that describes a case of transmission of Aspergillus which occurred within an ICU and which was attributed to aerosolisation of spores during wound debridement. Infectious agents such as Aspergillus, which can be disseminated as a result of building works, can be a particular problem for some patients groups e.g. severely immunocompromised due to cancer therapy (Siegel et al., 2007). This possibility should be considered during renovation work and one prospective study at a neonatal intensive care unit, looked at the 10

12 relationship between nasopharyngeal colonisation of neonates and the load of Aspergillus spores in the air (Mahieu et al., 2000). This study looked at the effect of a number of different physical barriers such as air filtration, positive air pressure and the addition of an extra HEPA filtration unit during this time and identified that there was a significant decrease in Aspergillus spp spores in the air. The study identified the role of adequate filtration and discussed the possibility of additional temporary filtration devices to be put into use during periods of renovation work to provide additional protection. However, this study found no link between biocontamination of the environment and nasopharyngeal colonisation of the neonates, although it was postulated that this was due to the existing engineering controls in place to protect the specific immunocompromised patient population. It has to be noted, that there were limitations to the study in terms of the frequency of the sampling which was on a weekly basis, however the results are interesting for further study. Additionally publication also identified the efficacy of the use of HEPA filtration for substantially reducing the load of Aspergillus spores spp during renovation work (Cornet et al., 1999). Airborne precautions These are a set of precautions designed to prevent cross transmission of infectious agents, which are transmissible by small airborne particles and include the components below. 4.1 Patient Placement Historically in the UK, isolation rooms have been used for the provision of care of patients with infectious diseases. In addition, ventilated isolation suites have also been used with positive pressure; for patients requiring protection from infectious disease due to underlying medical conditions or treatment regimes. Negative pressure has been used in the provision of care to patients with transmissible infectious diseases and indeed some facilities have the capability of switching from positive to negative pressure, dependant on the requirements. However, this type of option maybe a risk in itself as it relies on the admitting healthcare worker having sufficient knowledge and understanding of the infectious agent and engineering controls to correctly assess the required setting (HFS, 2007, DH and NHS Estates, 2005) and consequently this type of facility is no longer recommended for use. There are four categories that require patients to be cared for in isolation facilities which are; 1) patient susceptibility from infection; 2) Patient is an infection risk to others; 3) Non-medical reasons; 4) clinical but not infection related. From an infection and prevention point of view, only the first 2 categories require the use of an isolation suite instead of use of a single room with en-suite facilities. Scottish Health Facilities Note 30: Infection Control in the Built Environment: Design and Planning (HFS, 2007), which is adapted from (DH and NHS Estates, 2005) HBN 4, and recommends the provision of 2 different types of isolation facility, namely a single room with en-suite and a single room with ventilated lobby at positive pressure (isolation suite), which would enable this facility to be used for both categories 1 and 2 of patients requiring isolation within an acute care setting. This design ensures that patients potentially infectious to others are not a danger by preventing air from the room accessing the outside. Specifically for production of guidance on transmission-based precautions, only the second category of patients will be considered further and for airborne precautions, the currently recommended facility is an Isolation Suite or Enhanced Single Room with en-suite facilities and ventilated lobby (HFS, 2007) and this is the preferred option in terms of patient placement for patients with active infections transmissible by the airborne route such as pulmonary TB. Within HBN 4 there is a description of the basic engineering requirement for an isolation suite of 10 air changes per hour, with the entry lobby to be at +10 pascals with respect to the corridor. In addition, the en-suite is to be at a negative pressure with respect to the patient s bedroom with 10 air changes per hour. In order that the positive pressure status of the lobby with respect to the room can be checked before entry, there should be a gauge at eye level mounted adjacent to the lobby door with a suitable logbook for recording the lobby pressure by the staff (DH and NHS Estates, 2005). The 11

13 Scottish version of this updated document is still in draft form and has not been issued (at the date of this literature review). The role of suitable ventilation in the prevention of infectious agents disseminated by the airborne route has been well described in a systematic review in which 40 original studies were evaluated by a team of experts in the field of engineering and microbiology. The conclusion was that there was strong evidence to show an association between the spread of airborne infectious diseases such as chicken pox and measles within the healthcare environment and the direction of airflow, ventilation and this supported the use of negative pressure isolation rooms for the control of these specific infectious agents (Li et al., 2007). However, one research study (Damji et al., 2005) carried out an audit on the use of isolation facilities within their NHS Trust and the results showed that one third of patients admitted to a dedicated isolation facility were not thought to pose an infection risk by infection control staff. These rooms were being used at times of high bed demand by patients not requiring this level of care and this highlights that although such facilities do exist in some hospitals that they may not be available due to inappropriate use. The CDC guidelines on placement of patients on airborne precautions recommends the use of a single room which has air handling capable of supplying 12 air changes per hour and meets USA standards, however it is clear that the engineering recommendations within the UK are different and designed to meet alternative standards, therefore this has to be borne in mind with respect to recommendations resulting from the CDC guidance specifically in this regard (DH and NHS Estates, 2005). Additionally, the systematic review of airborne spread of infectious agents in relation to ventilation (Li et al., 2007), concludes that there is a lack of controlled studies specifically on the precise conditions of air flow and ventilation in order to prevent spread and therefore it is perhaps unsurprising that there is variation within different countries. Another review article (Walker et al., 2007), also notes that there is a lack of evidence specifically on this subject and also of consistent guidance. These authors make the point that isolation of patients is an incremental process which is dependant on a number of factors such as the infectious agent and other options may be applicable before the use of full isolation, such as cohorting and the use of non-specialist single rooms. The authors also note that the interest in air handling and the use of isolation suites has increased as a result of the occurrences such as the SARS outbreak and the emergence of drug resistant TB. 4.2 Personal Protective Equipment The terminology PPE refers to equipment that can be used as barrier to prevent exposure to potentially hazardous microorganisms and infections agents and is designed to protect both the healthcare worker and patient. The decision on the type of PPE required is based on the route of transmission of infectious agent if known or the potential risk if not known. The general evidence base surrounding transmission based precautions would imply that due to the increased risk from infectious agents spread by droplet, contact and airborne additional PPE must be considered. Even if the requirement for PPE is in line with SICPs alone it should be donned prior to entering the patient area or providing care activities in order to minimise the risk of transmission of the known/suspected infectious agent. An appendix has been attached to the policy which covers the safe donning and removal of PPE to avoid contamination. 12

14 4.2.1 Respiratory Protection Masks (FFP3) One of the main precautions potentially required for delivery of care for patients with infections transmissible by the airborne route, is respiratory protection. Respiratory protection masks are designed to prevent inhalation of infectious airborne particles and to prevent access to the mucous membranes of the respiratory tract of the individual (Siegel et al., 2007). In the UK, it is deemed by the Approved Codes of Practice (ACoPs) which support the COSHH regulations (HSE, 2002) that suitable respiratory protective equipment must be worn in situations when despite all other precautions taken, there is still a potential risk of exposure. The mask required must be able to reduce the exposure to within acceptable limits. The FFP3 facemask, which conforms to the European Standard EN is a filtering facepiece and the efficiency of these masks depends on there being a tight fit to the wearers face as an inadequate fit will result in lowering of the protection to the wearer. There is therefore a requirement for employers to ensure that respiratory protection available has been fit tested to the wearer. There are a number of additional sources of information on this subject and these should be referred for the necessary information required to ensure that the respiratory protection provided is adequate and that suitable fit tests have been carried out to avoid the protective equipment being compromised. Therefore prior to the use of FFP3 masks, it is recommended that fit testing according to the HSE guidance is carried out. One of the conditions for provision of respiratory protection is that FFP3 masks which are the same make, model, type, material and size of the one worn for successful fit test, is made available to employees, when required. It is imperative that if a proper fit cannot be achieved that the patient s area should not be entered. It is also worth noting that the fit of the mask can be compromised by a number of factors such as lack of clean shaven skin, or change in weight of the wearer since the fit testing. The fit of the mask should be checked before each occasion that the mask is donned and this is in addition to the fit testing which is required to be carried out by the employer upon issue. Due to the nature of the route of transmission and the fact that the infectious particles have the potential to disseminate beyond the immediate environment of the patient, the FFP3 mask should be donned before entry into the room or area of a patient suspected or confirmed to be infectious. There are a number of additional considerations required for wearing the FFP3 masks such as when and how to safely don and remove the masks and the fact that the surface of the masks should not be touched when in place. Scientific evidence shows that there is a possibility of contamination occurring on the outside surface of the mask therefore it is recommended that the mask is neither touched nor reused and are single use and disposable (Siegel et al., 2007, SEHD and HPS, 2005). In addition to leaving the patient s environment, masks should be disposed of when damaged, wet or visibly soiled as this may result in a decrease in protection. During the process of literature review specifically for droplet precautions, one of the recommendations identified for the prevention of cross transmission of infectious agents which transmit by droplets, is that a surgical mask is worn by patients being cared for using droplet precautions when they are being transported. It may seem therefore that the wearing of an FFP3 mask by a patient on airborne precautions may also be required. However, due to the nature of the filtration of an FFP3 mask, which filters incoming air and not expelled air, this would then result in air which has not been filtered being expelled and is therefore not suitable for use by the patient in this occasion but may be considered for use by the healthcare worker to protect from airborne infectious particles. 13

15 4.2.2 Gloves Gloves are recommended specifically to prevent exposure to infectious agents by both the healthcare worker and patient including the prevention of exposure to pathogens. Gloves should be worn when there is a possibility of direct contact with blood or body fluids, mucous membrane and also during healthcare procedures carried out on patients who are infected or colonised with epidemiological important organisms (Siegel et al., 2007). The use of gloves as PPE to prevent exposure to pathogens transmissible by contact with blood or body fluids is part of standard infection control precautions and is covered in detail within the HPS model infection control policy on PPE and associated literature reviews (HPS, 2007). As per standard infection control precautions, the need for a correct procedure for the removal of the PPE is stressed to avoid contamination at this stage, followed by hand hygiene. (Siegel et al., 2007, Farr et al., 2001, McBryde et al., 2004) Gowns The use of gowns has been reviewed within the CDC guidance and within the HPS model policy on PPE. Specific advice on the use of gowns and aprons is recommended as part of standard infection control precautions to protect from exposure to potentially infected blood and body fluids such as respiratory secretions and is covered in detail within the HPS Standard Infection Control Precautions Model Policy on PPE and associated literature reviews (Siegel et al., 2007, HPS, 2007). The requirement for use of the gown is governed by the nature of the healthcare procedure and whether it is anticipated that there will be a great deal of exposure to blood and body fluids. When a gown is required for Transmission Based Precautions, it should be donned on entry to the room and not just when it is anticipated that exposure to blood or body fluids may take place Eye Protection Certain procedures such as bronchocsopy, endotracheal intubation etc can result in the generation of aerosols and therefore additional precautions will be required to prevent transmission and it is recommended that eye protection and masks as well as gloves are required. As per standard infection control precautions, eye protection is required if there is anticipated to be a risk of exposure to spraying or splashing of respiratory secretions, blood or body fluids from procedures being carried out (HPS, 2007). 4.3 Immune status of healthcare workers There has been specific advice issued by the Scottish Executive Health Department recommending the immunisation of all non-immune healthcare workers in primary and acute care both in the NHS and privately, against varicella zoster virus (SEHD, 2004). This applies to everyone who performs direct patient care and is designed to protect both vulnerable patients and also susceptible healthcare workers from exposure. It is anticipated that this strategy will avoid the need for exclusion of staff groups depending on their immune status and also the costs incurred if exposure occurs. This CMO letter sets out the recommendation for immunisation of healthcare workers with no clinical history of chickenpox and / or shingles and with a negative blood titre. In addition to this specific CMO letter, further information on immunisation policy is available in the Varicella chapter of DH Green Book of Immunisation Against Infectious Disease (DH, 2006). 14

16 Organism Specific Considerations 4.1 Tuberculosis Over the years there have been a number of worldwide and UK guidance documents produced specifically for control of M.tuberculosis and the most recent have been considered within this literature review. The CDC released Guidelines for Preventing The Transmission of Mycobacterium tuberculosis in Healthcare Settings in 2005, which superseded the 1994 guidelines. It was noted that as a result of implementation of measures recommended in the 1994 guidelines within healthcare facilities that there was a decline in the number of cases associated with outbreaks of TB in the USA with concomitant decrease in cases of cross transmission to healthcare workers and other patients. The most recent guidelines (2005) have increased coverage to include facilities in addition to the acute setting such as prisons, primary care settings, long term care facilities etc, where healthcare is delivered and outbreaks of TB have been known to occur (Jensen et al., 2005). 4.2 Respiratory Protection for tuberculosis There is a hierarchy of strategies that should be employed to reduce the risk of nosocomial transmission of Mycobacterium tuberculosis within healthcare settings. The first line is the presence of barriers such as air handling and engineering controls however it is acknowledged that at times extra precautions in the form of respiratory protection should be taken. This is dependant on whether the patients are within their first two weeks of anti-microbial therapy; or placed in rooms without the correct engineering controls; certain procedures such as sputum induction or aerosol generating procedures may be carried out that may cause temporary increase in the airborne contamination before the appropriate air changes have taken place (Jensen et al., 2005). The CDC Guidelines of Management of Mycobacterium tuberculosis in Healthcare Settings (Jensen et al., 2005) specifically discuss that the risk of transmission of TB is associated with persons with unsuspected disease, or those receiving inadequate therapy or who are in the early stages of therapy. Furthermore the results of a study looking a the mathematical modeling of airborne infection demonstrated that the use of personal respiratory protection was likely protect against nosocomial TB in settings where room ventilation rates are low (Fennelly et al., 2004). The guidelines issued by the CDC specifically for prevention of transmission of TB (Jensen et al., 2005) recommends that all persons, including healthcare workers and visitors should wear respiratory protection when entering a room in which patients with known or suspected pulmonary or laryngeal TB are isolated. The guidelines also state that respiratory protection should be worn by all persons present when aerosol generating or cough producing procedures are being carried out and also in other settings and rooms without the correct engineering controls in place including during provision of emergency dental care and also during transport. On review of the evidence, the authors have concluded that there are considerable gaps in the scientific knowledge specifically on the dose of infectious agent that results in transmission, however given the fact that documented outbreaks of nosocomial TB have occurred within these settings, it would seem appropriate that suitable precautions are taken (Siegel et al., 2007). Guidelines covering the clinical diagnosis and management of tuberculosis and measures for its prevention and control (NICE, 2006) have been issued in the UK as a source of best practice advice on the care of patients with or at risk of contracting TB. These guidelines offer comprehensive advice on clinical management of active TB as well as infection prevention and control measures that should be used by healthcare workers caring for patients with this disease. It should be noted, however that the recommendations specifically on infection control are classified as D(GPP) which is defined as a good practice point which is based on expert opinion and formal consensus of the Guideline Development Group. The recommendations covering TB which form part of the CDC guidelines on Isolation and 15

17 those specifically for management of TB in healthcare settings (Siegel et al., 2007, Jensen et al., 2005) have included a full literature review of the scientific evidence supporting the use of respiratory protection for the initial period until treatment is established and the period of maximum infectivity passed. The risk of nosocomial transmission of TB is associated with close proximity to the case and the longer the duration of exposure the higher the risk. Nosocomial outbreaks of TB have been documented as a result of exposure during aerosol generating procedures, sputum induction, open abscess irrigation, and autopsy (Jensen et al., 2005). It has been identified in a number of publications, including retrospective studies of outbreaks within healthcare settings that one of the highest risks for healthcare workers is associated with delivery of care to patients with unrecognised respiratory TB, who are then treated without use of the appropriate precautions such as use of engineering controls and suitable respiratory protection (Jensen et al., 2005). The majority of reported outbreaks within healthcare settings have been associated with transmission of MDR TB strains and the patients and indeed some healthcare workers exposed had an HIV positive status and the result was swift progression to MDR TB. On analysis of the reasons for these outbreaks it was clear that some of the factors involved were the delay in diagnosis, with associated delay in instigation of airborne precautions such as the use of isolation suites and suitable respiratory protection. Following the release of the first set of TB guidelines by the CDC in 1994 (Anonymous, 1994), surveillance studies showed an increased level of compliance with the recommendations given within acute settings across the US with concomitant reduction in nosocomial TB. Studies from this time noted that infection control recommendations had not been so fully implemented in non-acute settings, probably due to barriers such as cost and that outbreaks had occurred within these settings i.e. GP surgeries etc where guidelines were not followed. Furthermore it has been highlighted in a number of scientific publications that the highest transmission risk was from patients with unrecognised TB or MDR-TB and who were treated without recommended airborne precautions. The current NICE guidelines in the UK (NICE, 2006) recommend that: Healthcare workers caring for people with TB should not use masks, gowns or barrier nursing techniques unless MDR TB is suspected, or aerosol generating procedures are being performed. As previously discussed, this recommendation is given the category D(GPP) which is defined as; Good Practice Point which is a recommendation for practice based on the experience of the Guideline Development Group and / or Extrapolated from level 2 clinical evidence, supplemented with health-economic modeling. A number of publications have resulted from the publication of this UK guidance specifically discussing potential confusion surrounding this specific recommendation. One article (Pratt and Curran, 2006) discusses the fact that although administrative and engineering controls form the main precautions required for prevention of cross transmission of TB, that respiratory protection has always formed a main part of the measures required and this fact has been recognised in by the HSE under COSHH legislation (HSE, 2002). This article documents an occasion where an outbreak of MDR-TB occurred in a London teaching hospital due to a failure of engineering controls and another occasion due to ineffective screening at admission and delay in starting treatment and instigation of appropriate precautions. In the section of the ACDP guidance Biological Agents: Managing the risks in laboratories and healthcare premises, (HSE, 2002), it states that although the hierarchy of controls in COSHH indicates that respiratory protective equipment should be considered as a last resort that the practicalities of patient care mean that a combination of approaches should be taken. In accordance with the NICE guidelines, implementation of the use of FFP3 respirators on admission is subject to successful screening by triage staff to determine if there is possibility of MDR TB. However if no risk is identified at this stage, then care will be provided by healthcare workers without respiratory protection, and if the patient subsequently is identified to have drug resistant TB then there is a period of time that healthcare workers are unnecessarily put at risk. The difference in risk assessment attributed to MDR- TB as compared to drug sensitive TB is perhaps due to the fact that the majority of healthcare workers are assumed to be immune, due to BCG vaccination. However there is some debate 16

18 over the efficacy of this vaccine and also the duration of protection (WHO, 1999). The Green Book (DH, 2006) has a literature review section specifically discussing the efficacy of the BCG vaccine. From the result of numerous studies it is clear that it is not possible to attribute an exact figure to the efficacy of the vaccine as there is wide variation between with the highest figures estimated as 70-80%. It is expected of most vaccines that the efficacy approaches 100%, and the BCG is obviously less than this, therefore it would seem on risk assessment that the use of the vaccine alone may not be relied upon and therefore the use of additional precautions may appropriate. Another recent review article (Humphreys, 2007) also highlights that the guidance specifically on this subject differs in the UK compared to Europe and the USA and the author argues that there is a strong case, based on observational studies and mathematical modeling that isolation facilities and personal respiratory protection should be used for the care of all patients with active respiratory TB as the diagnosis of MDR-TB may not always be obvious at admission. 4.3 Sputum generating procedures The particular risks associated with sputum induction were addressed in an article (Menzies et al., 2003), in which the researchers measured the airborne bacterial load within the sputum induction room within a healthcare facility by evaluation of a large number of samples during the performance of 58 sputum inductions. The results showed a substantial increase in the airborne bacterial load at these times, despite the presence of ventilation and air changes through engineering controls, although it was observed that there was marked variation between patients. The authors note that there have been a number of outbreaks of nosocomial transmission within healthcare facilities by this procedure being carried out on patients with active pulmonary TB and the results of this study indicate that there is the possibility of exposure to the infectious agents despite the presence of regulation engineering controls. It should be noted, however that this study was a real time study during treatments and not a randomised control study, therefore the results may have to be treated with caution, however there is still an indication that the use of engineering controls alone may not be sufficient to prevent exposure. The potential hazards of sputum generating procedures with respect to cross transmission of TB have been well addressed in the available guidelines UK and worldwide (Jensen et al., 2005, NICE, 2006) and also in the ACDP guidelines (HSE, 2002). The common recommendation is that in order to provide the most effective prevention and control of transmission of this pathogen during this type of procedure that all controls should be in place, with the addition of respiratory protection Aerosol generation 4.1 Severe Acute Respiratory Syndrome (SARS) There are an extensive number of publications, which have resulted from the SARS outbreak in 2002, which was caused by the SARS CoV virus. A large number of the scientific studies were concerned with outbreaks which had occurred in healthcare settings in which cross transmission to healthcare workers, patients and visitors had occurred. From the results of the various studies it was concluded that the main mode of transmission was via respiratory droplets (>5 μ), which do not travel far from the source. However, there was some suggestion that there was an element of airborne dissemination by the formation of airborne droplets during the performance of aerosol generating procedures i.e. intubation, nasopharyngeal aspiration, tracheostomy care, chest physiotherapy, bronchoscopy and nebuliser therapy etc for patients suffering from SARS (HPA, 2005, Siegel et al., 2007). Analysis of retrospective case studies showed that there was a higher risk of cross transmission to healthcare workers when suitably fit tested respiratory protection was not used in conjunction with other precautions such as gowns, gloves and eye protection. The literature also shows that there is higher risk of cross transmission of respiratory infections to healthcare personnel if they are not adequately 17