Gurpreet Kaur*, Manju Chawla**, Adarsh Chandra Swami***, Ashwini Sharma****
*Clinical associate, **Senior Resident, ***Add. Director & Head, ****Consultant Anesthesia
Deptt of Anaesthesia and Critical Care, Fortis Hospital, Mohali, Punjab, India.
Correspondence: Dr. Gurpreet Kaur, Clinical Associate, Deptt of Anaesthesia and Critical Care, Fortis Hospital Mohali, Punjab- 160072 (India); Cell: 9815974429; E-mail: gurbaryah@msn.com
Minute ventilation is the product of respiratory rate and tidal volume. Low values, despite adequate tidal volume and respiratory rate setting on the ventilator can be due to several causes. A rare cause can be a hole in the endotracheal tube (ETT) due to patient’s biting or chewing on it. We discuss a 34 year old lady, known patient of diabetes mellitus, rheumatic heart disease with severe mitral stenosis and chronic kidney disease. She had been referred to us from a nursing home after radical nephrectomy. Patient was on full mechanical ventilatory and inotropic support on the 5th postoperative day. A continuous ventilator alarm of low minute ventilation was noticed. The tidal volume delivered by ventilator was normal but the expired tidal volume was persistently low. Breathing circuit was checked for disconnection and integrity. ETT cuff pressure was checked and was found to be adequate (25 mmHg). She was given additional doses of the sedatives and muscle relaxants, which further decreased the minute ventilation. There was no bronchospasm on chest auscultation. We found a small rent in the ETT at the level of molar teeth caused perhaps due to intermittent biting by the patient. In the mean time, patient’s SpO2 dropped, so the hole was blocked with sterile, gloved hand and ventilation continued to attain 100% saturation. The ETT was then changed and thus ventilation normalized.
The major goal of mechanical ventilation is to maintain adequate alveolar minute ventilation and normal levels of partial pressure of CO2.¹ Low minute ventilation can be due to decrease in respiratory rate, tidal volume, circuit disconnection, ETT cuff leak, insufficient gas flow, increased airway resistance, inadequate ventilatory settings, incorrect alarm settings, non delivery of gas or chest wounds allowing air escape.²
Further, ETT cuff rupture can occur due to application of lubricant or local anesthetic spray, during central venous cannulation (both subclavian and internal jugular vein cannulation ), laser beam can perforate the cuff, patient can chew a hole in or completely severe a tube, tube malposition (cuff at or above the level of vocal cords ) and eccentric cuff inflation can result in leakage during mechanical ventilation. In case of a leak, direct laryngoscopy should be done to check the position of cuff. ³
We opine that a bite block should be in used to prevent damage to all types of oral tracheal tubes in a lightly anaesthetized or conscious patients, also the circuit should be checked in entirety to when ever an alarm goes on. ⁴
REFERENCES
- Scherf R, Carr C. Understanding Ventilation Care: Part II. On Advance healthcare Network for Nurses. Feb 24,2010. [Access Online]
- Kane Guthrie. Ventilator alarm check list from Slideshare. [Access Online]
- Dorsch JA, Dorsch SA. Tracheal tube. In : Zinner S. Understanding Anesthesia Equipment. Fourth Edition. USA: Lippincott William & Wilkins; 1999.p. 557-671.
- McLean R, Houston P, Carmichael F, Bernstein M. Disruption of an armoured endotracheal tube caused by biting. Can Anaesth Soc J 1985;32(3 Pt 1):313-4. [PubMed]
