Breathing filters provide an effective barrier that prevent cross contamination between patients, breathing systems, respiratory and anaesthetic equipment, and the clinical environment. Their use is widely recognised as beneficial and is recommended by a number of Anaesthetic Associations(1). They are widely used across the hospital, particularly in the operating theatre, critical care, lung function units, and respiratory care units.
Heat and Moisture Exchangers (HMEs) minimise loss from patient expired gases. When combined with a filter (Heat and Moisture Exchanging Filter, HMEF) this will also reduce the risk of cross contamination in the clinical environment.
The normal function of the body’s upper airway is to filter, humidify and warm the air we breathe in. Air is warmed by passing over a vast network of capillaries in the nose. Mucous membranes line the upper airways and help to moisten the air and trap airborne particles (dust and microbes). Cilia move the mucus away from the lungs and towards the pharynx for removal.
The upper airways also help conserve heat and humidity, which would otherwise be lost during normal respiration. Gas leaving the lungs during expiration will be at body temperature (37°C) and have an Absolute Humidity (AH) of 44mg/l H2O and a Relative Humidity (RH) of 100%. As the patient breaths out, heat and moisture is retained by the upper airways and then transferred to the inspired gas, which is normally cooler and drier depending upon the ambient conditions. The large surface area of the upper airways makes it particularly efficient. This helps minimise any potential side effects associated with breathing cold dry gases over a prolonged period.
This natural physiological protection is bypassed when an artificial airway device is inserted, for example a tracheal tube, a supraglottic airway or tracheostomy tube. This means the gas source has a direct route to the delicate and sensitive lungs, which can result in an increased risk of infection and potential microbial cross contamination.
It could also result in a cooling and drying out of the airways as a result of breathing cold dry medical gases over a prolonged period of time. Room air would normally be approximately 23°C with an RH of 60% and an AH of 21mg/l. Medical gases would normally be 10-15°C with a RH of 0-2 % and an AH of 0.5 mg/l, which would further increase the risk. This can lead to damaged cilia, thicker mucous, mucous crusts leading to an increased risk of tube occlusion, increased risk of infection, atelectasis and increased cost due to prolonged hospital stay.
Protecting the patient
Critically ill patients with reduced immunity are commonly at an increased risk of infections. These nosocomial infections result in increased morbidity and potential mortality as well as having a significant impact on the cost of treating the patient due to increased hospital stay. The strategic use of an efficient, properly validated breathing filter provides an effective barrier between patient, breathing systems and respiratory equipment, which reduces the risk of cross contamination.
|Protection of respiratory equipment and clinical environment
Protecting the equipment
The use of appropriate and effective breathing filters can provide protection to delicate and expensive equipment, helping to preserve functionality, reduce running costs and reduce potential cross contamination.
|Increasingly the only way that a clinician can determine the efficiency and effectiveness of the performance of a breathing filter, HME and HMEF is via standard test protocols and results. Ensuring the data is clinically relevant, up-to-date and reflective of the product that the customer is using is vital.
Our range of breathing filters and HMEFs have been independently tested and proven to be highly efficient in preventing the passage of bacteria and viruses. These tests provide clinically relevant information to allow evidence-based decisions to be made on the most appropriate product to meet your clinical requirements.
All our filters are tested at specialist microbiology laboratory facilities against clinically relevant bacterial and viral challenges. This is normally performed at an independent test facility that develops specific protocols to simulate the types of challenges that a filter may see in the clinical setting.
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