ABSTRACT Airway management is a vital part of the anaesthetic process and crucial to the health and welfare of animals undergoing anaesthetic procedures by delivering oxygen and inhalational agents . The methods available to veterinary practice are well discussed and the advantages and disadvantages widely known . They are summarised in Part 1 of this two-part series . However , it is not known which methods are most often used for feline neutering procedures and why , as there have been no previous studies on this topic . This will be explored in Part 2 of this series .
Keywords face masks , endotracheal tubes , supraglottic airway devices , tracheostomy tubes , airway management , intubation , feline , neutering
Airway management for general anaesthesia
General anaesthesia can have several effects on the body that place the airway at risk . The relaxation of the pharyngeal muscles allows the upper airway to collapse inward and the relaxation of the upper and lower oesophageal sphincters increases the likelihood of regurgitation [ 1 ] . Therefore , confirming a secure airway is essential to provide safe anaesthesia and maintain adequate respiratory function .
Sheppard [ 2 , 3 ] discussed five methods used to secure a patient ' s airway : face masks , endotracheal tubes ( ETTs ), supraglottic airway devices ( SGADs ), emergency options ( e . g tracheostomy tubes ) and the option of using no airway management . The most discussed methods include ETTs , face masks and , more recently , the SGAD v-gel [ 4 , 5 ] .
ETTs are widely accepted in the literature as being the most commonly used method of airway management in small animal practice [ 2 , 6 , 7 ] . Currently , both the American Association of Feline Practitioners ( AAFP ) [ 7 ] and the American Animal Hospital Association ( AAHA ) [ 8 ] agree that a cuffed ETT or an SGAD , such as the v-gel , is the preferred way to maintain an airway during anaesthesia .
Endotracheal tubes
Use of an ETT enables the delivery of oxygen and volatile agents and secures a clear airway . ETTs also reduce environmental contamination with anaesthetic gases and facilitate positive-pressure ventilation , if required [ 6 ] . The tubes are available in a range of materials and in cuffed and non-cuffed varieties . The use of a cuffed ETT is widely debated in the profession . Yates and Holgate [ 9 ] explored the use of cuffed ETTs in cats and the associated risks and benefits . When using a cuffed ETT , the aim is to achieve a seal between the cuff and trachea , with a pressure great enough to prevent aspiration but not so high that tracheal blood flow is impeded [ 2 ] .
Cuffed versus non-cuffed ETTs
The cited benefits of cuffed ETTs include the seal on the tube being superior to non-cuffed tubes , resulting in reduced environmental exposure to volatile agents and a reduced likelihood of aspirated material travelling down the trachea .
However , key risks of cuff inflation include barotrauma , when combined with high flow rates and assisted ventilation , in addition to the risk of iatrogenic damage to the tracheal mucosa with inappropriate cuff inflation [ 9 ] . Sheppard [ 2 ] agreed that over-inflation of the cuff can lead to a range of deleterious effects , including inflammation , ischaemia , granulation , ulceration and necrosis .
Yates and Holgate [ 9 ] evaluated methods of cuff inflation ( including pilot balloon palpation , minimal occlusive volume and a cuff manometer ) and concluded that the use of a manometer to inflate the cuff to a pressure of 20 – 30 cm H 2
O is a precise method of safe cuff inflation . This method ensures a safe pressure , which will prevent aspiration but not impede tracheal blood flow .
Additionally , a recent study in dogs by Hung et al . [ 10 ] evaluated the minimal occlusive volume method with two types of cuff manometers . Results showed that minimal occlusive volume over-inflated the cuff in 80 % ( n = 24 ) of cases , whereas the use of the AG Cuffill manometer to inflate the cuff to 30 cm H 2
O overinflated the cuff in only 3.3 % ( n = 1 ) of cases ( Table 1 ).
The results of these studies confirm that the ideal method for cuff inflation would be to use a cuff manometer such as Tru-cuff or AG Cuffil to ensure cuff inflation to a safe pressure and avoid the risk of tracheal damage [ 9 ] .
Table 1 . The distribution of ETT cuff inflation conditions after the use of regular injectable syringe , Tru-cuff and AG Cuffill syringes [ 10 ] .
ETT cuff inflation
Regular syringe Normal inflation 1 Over-inflation 24 Under-inflation 5 Tru-cuff syringe Normal inflation 15 Over-inflation 2 Under-inflation 13 AG Cuffill syringe Normal inflation 26 Over-inflation 1 Under-inflation 3
Number of dogs
Volume 38 ( 1 ) • February 2023
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