Masks were introduced into clinical practice at the beginning of the 20th century to protect patients from microorganisms being expelled from healthcare workers’ respiratory tracts during clinical procedures (Wilson, 2006).

Interest in the effectiveness of masks has been raised by the swine flu pandemic.

In discussing effectiveness of masks, it is important to differentiate between standard surgical face masks and respirators.

The Health Protection Agency (2009) advises people with flu to use face masks when they are in contact with other people and healthy people to wear a face mask when they are caring for a person with flu in non-clinical situations.

Where healthcare staff are involved in caring for a patient with a probable/confirmed diagnosis, they should wear a face mask, plastic apron and gloves as a standard precaution, with the addition of eye protection if splashing is likely to occur. Where aerosol-generating procedures such as physiotherapy are being undertaken, an FFP3 respirator is required in addition to a gown, gloves and eye protection.

The same precautions also apply to caring for patients with severe respiratory illness as a result of swine flu as they are likely to be shedding high quantities of virus.

Health professionals, to avoid transferring bacteria from their mouths to patients, usually wear a surgical mask, during surgery, or when visiting vulnerable patients. The surgical mask may also protect against blood splatters from a patient during surgeries. It is usually made of paper or synthetic materials suitable for one-time use only.

Some people also wear a paper or synthetic surgical mask to protect themselves from pollen inhalation during hayfever months. This may provide some benefit, and help reduce inhaled pollen, but again it should not be reused. Because an oxygen mask is not necessary when you are trying to avoid pollen, there are better face masks than the sterile surgical mask to keep pollen out of the nose and mouth. Others use a surgical mask to protect themselves from disease, but this is actually not a benefit of the mask.

When Severe Acute Respiratory Syndrome (SARS) outbreaks in China, Hong Kong and Vietnam threatened the local population, many could be seen wearing surgical masks in public in the hopes that these would offer them a little extra protection against SARS. In reality, viral particles of diseases like SARS can easily penetrate a surgical mask. In order for true protection to be provided, you would need an airtight mask that can trap tiny virus particles, like the National Institute for Occupation Safety and Health (NIOSH) masks.

People with SARS, or any illness can protect others from a some exposure by wearing a surgical mask. Yet if a person infected with SARS coughs or sneezes, viruses will penetrate most surgical masks. There is still chance of viral transmission when a person with a highly contagious disease wears a surgical mask. To this end, when certain superflus are suspected, medical workers may wear masks with respirators and special safety suits so that the virus cannot be transmitted.

The surgical mask also has a somewhat limited time period in which it will be effective. They frequently will only work for an hour or two at most. Moisture from the mouth and nose will ultimately transfer to the outside of the mask, making the simple surgical mask sterile for only a short time period. When parents or friends visit people with extremely vulnerable immune systems from diseases like cancer, they usually must exit the room and change their masks after an hour or two.

Even though wearing a surgical mask may briefly protect others from any germs you might be carrying, the principle means of avoiding virus transmission is still through good handwashing practices. These should be observed in any public setting, and are a particularly important practice in hospitals.

Types of endotracheal tube (ETT) include oral or nasal, cuffed or un-cuffed, preformed (eg RAE tube), reinforced tubes, feeding tubes, double-lumen tubes and tracheostomy tubes. For human use, tubes range in size from 2-10.5 mm in internal diameter (ID). The size is chosen based on the patient's body size, with the smaller sizes being used for paediatric and neonatal patients. Tubes larger than 6 mm ID usually have an inflatable cuff.

Originally made from red rubber, most modern suction catheters are made from polyvinyl chloride. Those placed in a laser field may be flexometallic.

Dr. Robertshaw (and others) developed double-lumen endo-bronchial tubes for intra-thoracic surgery. These allow single-lung ventilation whilst the other lung is collapsed to make surgery easier. The deflated lung is re-inflated as surgery finishes to check for fistulas (tears).

Another type of endotracheal tube has a small second lumen opening above the inflatable cuff, which can be used for suction of the nasopharngeal area and above the cuff to aid extubation (removal). This allows suctioning of secretions which sit above the cuff which helps reduce the risk of chest infections in long-term intubated patients.

A shortened tube, a tracheostomy tube, can be inserted through an opening in the neck (a tracheostomy) into the trachea. This is often a temporary stoma, but pat