Airway devices are used to secure , maintain and protect a patent airway , provide a means to deliver oxygen and volatile gases , remove expired waste gases and support ventilation . Commonly used airway devices include ETTs , supraglottic airway devices ( SGADs ) and face masks .
Face masks are used in conscious or sedated patients for oxygen supplementation . Their use in providing gaseous maintenance anaesthesia can lead to personnel being exposed to anaesthetic gases . They offer no airway protection from aspiration and inhibit the ability to provide effective positive-pressure ventilation ( PPV ). They will not be discussed further in this article .
Endotracheal tubes
ETTs are made from red rubber , polyvinylchloride ( PVC ) or silicone and can be manufactured with or without a polyurethane cuff . The two cuff types are described in Table 1 .
The components of an ETT are shown in Figure 3 . They include a pilot balloon ( which indicates cuff inflation ), a Murphy eye ( which allows gas flow if the bevel becomes obstructed ), a radiopaque position guideline and measurements in centimetres from the distal tip ( to confirm the depth of insertion ).
Table 1 . ETT cuff types .
Cuff type Description Image
Low-volume / high-pressure ( LV / HP )
A lower volume of air is required to inflate the cuff but it creates a narrow area of high pressure on the mucosa . The cuff lies flat against the ETT when deflated .
High-volume / low-pressure ( HV / LP )
A higher volume of air is required to inflate the cuff but the pressure is spread throughout the length of the cuff , reducing high-pressure damage to the mucosa . The cuff is wrinkled against the ETT when deflated .
Figure 3 . ETT components and markings . A : A size 4.0 mm ETT in a standard length . B : A size 3.5 mm ETT that has been cut to a more appropriate size at the proximal end .
46 Veterinary Nursing Journal