The Dept of Anaesthesia & Intensive Care, CUHK
Respiratory protection involves 4 levels of infection control:
This consists of mechanisms to identify and isolate potentially infectious patients. In epidemics it may not be possible to isolate each potentially infectious patient and in these circumstances cohorting of patients should be used.
Minimize spread of infectious particles from patient. In the intubated patient the following may help:
Personal protective measures
Hand cleansing is an important part of these measures
Coughing and aerosol generating procedures produce droplets which are potential vehicles for spreading infection. The largest droplets fall to the ground almost immediately. Smaller ones travel a few feet before falling to the ground but some of these droplets may undergo sufficient evaporation as they fall to become very small and remain airborne. These airborne particles will then spread throughout the room in which they are generated. When these airborne particles are inhaled they are rehydrated and therefore become bigger and deposit in the lungs. The ability of an infectious organism to be spread by the airborne route depends, in part, in its ability to survive the dessication and rehydration process.
Personal protective equipment (PPE)
Respiratory PPE can be divided into equipment designed to protect against droplet spread and measures to prevent airborne spread. It is also important to consider eye protection as the conjunctivae serve as a portal of entry for many respiratory viruses.
Surgical masks are thought to be an effective method of preventing droplet spread. Use of multiple masks increases their effectiveness but even 5 surgical masks used together are much less effective than a N95 mask
Risk factors for airborne infection
Probability of infection estimated as:
•I = no. of infectious source patients
•q = no. of infectious quanta produced per hour
•p = minute ventilation of healthcare worker x 60
•t = exposure time
•R = respirator leak ratio
•Q = room ventilation rate (room volume x air changes per hour)
An infectious quanta is the number of organisms that need to be inhaled to produce infection. For tuberculosis this is estimated to be 1.
April, 2014 unless
otherwise stated. The author, editor and The Chinese University of Hong Kong
take no responsibility for any adverse event resulting from the use of this