Impact of endotracheal tube size and cuff pressure on tracheal and laryngeal mucosa of adult horses.

The research article investigates the effect of different sizes of silicone endotracheal tubes on the tracheal and laryngeal mucosa in adult horses.

Methodology

• The study was a prospective, randomized, blinded, and crossover experimental study.
• Eight healthy adult mares were involved in the experiment. However, data was collected only from seven horses as one horse with laryngeal hemiplegia was excluded from the study.
• The day before anaesthesia, upper airway endoscopy and ultrasound measurements of the internal tracheal diameter were performed on the horses.
• The horses were then anaesthetized and orotracheally intubated with either a 26mm endotracheal tube (ETT) or a 30mm ETT.
• The ease of intubation was scored. The cuff of the ETT was inflated in 10 mL increments until a seal was produced.
• The final volume of air used and the intracuff (IC) pressure were recorded. The IC pressure was measured using a pressure transducer.
• At the end of anesthesia, a manometer was used to measure IC pressure. These measurements were compared against the measurements from the pressure transducer.
• Finally, the laryngeal and tracheal mucosa were examined via endoscopy, and a score ranging from 0-3 was assigned before anesthesia, and at 2 and 24 hours post-extubation.

Results

• The mean tracheal ultrasound measurement was found to be 3.5 ± 0.4 cm.
• No significant differences were observed between the two canal sizes- 26mm and 30mm, with regards to scores for ease of intubation, IC pressures, inflation volumes or tracheal or laryngeal injury scores at any specified period of time.
• The IC pressure measured by the manometer was slightly higher than the one calculated by the transducer by +1.0 ± 2.8 mmHg.

Conclusion

• The results did not indicate a clear advantage in using one tube size over the other when proper application of endotracheal intubation is ensured, and IC pressure is carefully monitored.
• However, due to the association of 30mm ETT with the highest observed IC pressures and the presence of tracheal circumferential erythema, it appears to be the safer choice. Therefore, the larger ETT is likely a better choice in most cases where tracheal size is ample.