Re: The new UK antimicrobial resistance strategy and action plan
One point not often mentioned in relation to spread of antibiotic resistant organisms is whether improved monitoring of hospital ventilation, heat and humidity at the patient level on the ward would help reduce the cross infection risk. In my experience, many patients complain of hot, humid wards (1), both in mechanically ventilated hospitals and in hospitals with natural ventilation (where window opening is restricted to 10cm to prevent suicides & falls (2).)
The large amount of heat-producing electrical equipment in hospitals (computers, medical equipment, televisions, bright lights, refrigerators, fans etc) must be giving heat increases far in excess of those in even the relatively recent past. In general, as temperature increases, so relative humidity decreases but this requires an adequate air flow at patient (& commode) level. If air changes are not adequate, water vapour and steam from kitchens and bathrooms will not be so easily lost through evaporation. Also, surfaces will dry more slowly. Bacteria including antibiotic resistant Gram-negative bacilli and some respiratory viruses will survive in areas which are moist and warm (3).
When humidity increases, sufficient air changes are also needed to allow evaporation of perspiration (which helps regulate body temperature). Under warm, humid conditions, both staff and patients will be less able to lose body heat and sweat will not evaporate so easily from the skin. Moist hands will acquire and transmit both antibiotic resistant and antibiotic sensitive organisms more readily than dry hands (4-7)
With intensive bed use and high occupancy rates, adequate air changes are also necessary to refresh the air (8) and dilute the airborne bacterial load.
There are no official NHS regulations on heat and humidity. To maintain acceptable levels, alterations to naturally ventilated areas may not be expensive. One study showed that air-borne spread of organisms (using Mycobacterium tuberculosis as an example) was less with openable doors and windows than in some more expensive mechanically ventilated areas. (9)
Proper control of hospital temperature and humidity is overdue and air changes at patient level should be monitored regularly -- and would also provide a much more comfortable environment for the patient.
1. Williams M BMJ Rapid Responses 27.6.2008 A breath of fresh air
2. NHS Estates Health Technical Memorandum 55 Windows 98.
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5. Marples RR, Towers AG. A laboratory model for the investigation of contact transfer of micro-organisms. J Hyg (Lond) 1979;82(2):237-248.
6. Hill HW, Mathews H. Transfer of infection by handshakes. The Public Health Journal 1926:(7):347-352.
7. Patrick DR, Findon G, Miller TE. Residual moisture determines the level of touch-contact-associated bacterial transfer following hand washing. Epidemiol Infect 1997;119(3):319-325.
8. Clements-Croome DJ, Awbi HB, Bako-Biro Zs, Kochhar N, Williams M. Ventilation rates in schools. Building and Environment 2008; 43:362-367
9. Escombe AR, Oeser CC, Gilman RH, Navincopa M, Ticona E, Pan W. Natural ventilation for the prevention of airborne contagion PLoS Med 4(2):e68. doi:10.1371/journalpmed0040068
Competing interests: No competing interests