Defective endotracheal tube: Undetected by routine inspection.

Sir,

Endotracheal intubation is an essential step for securing the airway of a patient. Ideally endotracheal tube (ETT) should be of appropriate size, as it acts as an extension of trachea, with added disadvantage of increased dead space, increased resistance and work of breathing.[1] The increase work of breathing is considerable in paediatric patients due to narrower airway.[23] Factors which determine the resistance imposed by ETT on gas flow are internal diameter, length, configuration, and dead space of the tube.

According to Hagen Poiseuille law

Δ = ( × × )/[4]

Where ΔP is the pressure gradient across the tube, r is the radius of the tube, L is length, v is the viscosity of the gas, and V is the flow rate.

American National Standards Institute/International Standards Organization had put recommendations for anesthetic and respiratory equipment — tracheal tubes and connectors (ANS/ISO 5361), including material of construction, internal diameter, length, inflation system, cuff, radius of curvature, markings, packing, and labelling of ETT. Previous cases[45] of endotracheal tube malfunction or defects inside the tube, cuff inflation tube, or pilot valve have been reported.

A 1 year old child with diagnosis of tetralogy of Fallot (TOF) with cyanotic spell was received in cardiothoracic and vascular surgery ICU for management. The oxygen saturation was not improved satisfactorily, even after administration of parenteral morphine, intravenous fluid, and noradrenaline infusion. Then plan for intubation and emergency modified Blalock — Taussig (BT) shunt was made. After administration of intravenous ketamine, atropine and suxamithonium, endotracheal intubation was performed with 4 mm uncuffed ETT(Sterimed, India). There was resistance to manual ventilation. Chest was auscultated for assessment of equal bilateral air entry, which revealed feeble breath sound. Ventilation with Jackson and Rees (JR) circuit was rechecked for tube kink or malfunction of the components, which were found to be alright. Endotracheal tube was thought to be appropriate as it had snugly passed through the vocal cord and there was no palpable or audible leak. Suspecting the presence of secretions or mucus plug a 6F suction catheter was inserted into the ETT. Surprisingly, the catheter could not be negotiated freely beyond the ETT connector. The patient was reintubated with another 4 mm uncuffed ETT (Portex) after removing the earlier one. The air entry was adequate and equal bilaterally. Rest course of the patient during the perioperative period was uneventful. External examination of the first ETT revealed nothing, but connector of the tube revealed annular meniscus eventually creating a narrowed orifice at the patient end of the connector [Figure 1]. The machine end of the connector was absolutely normal when compared with connector of ETT of the same size [Figure 2]. Bilateral air entry was decreased due to high resistance. We suspect the ETT connector lastly after ruling out all other causes of poor air entry.

Figure 1

Patient end of ETT connector showing meniscus

Figure 2

Machine end of ETT connector

We have reported a case of defective endotracheal tube, where the problem was in the patient end of ETT connector which could not be detected even after through and repeated external examination. Such similar situation may occur in other hospitals also due to lack of standardization or quality control of endotracheal connector. The main learning point to be highlighted here is, in the absence of any common obvious reason (esophageal intubation, bronchospasm, kinking of ETT, secretions, tension pneumothorax, cuff herniation) for inadequate ventilation to replace the ETT after performing direct laryngoscopy and inspect both tube and connector of previous tube.