Journal of Marine Medical Society

: 2019  |  Volume : 21  |  Issue : 1  |  Page : 83--86

Intraoperative kinking of armored endotracheal tube leading to airway obstruction in obese patients positioned prone for spine surgeries: A report of two cases

Vidhu Bhatnagar1, Deepak Dwivedi2, S G S Datta3, Swayam Tara1,  
1 Department of Anesthesiology and Critical Care, INHS Asvini, Mumbai, India
2 Department of Anesthesiology and Critical Care, Command Hospital (Southern Command), Pune, Maharastra, India
3 Department of Surgery, INHS Asvini, Mumbai, India

Correspondence Address:
Surg Cdr Vidhu Bhatnagar
Department of Anesthesiology and Critical Care, INHS Asvini, Near RC Church, Colaba, Mumbai - 400 005, Maharashtra


Obesity is an important problem with increasing incidence in affluent society. Managing obese patients in prone positions under general anesthesia requires optimization and adequate preparation for a successful outcome. Despite all optimizing measures are taken preoperatively, complications such as kinking of armored endotracheal tubes may take place in these patients in prone position leading to problems during mechanical ventilation. Armored tubes are being widely used in anesthesia practice in surgeries involving procedures during which kinking are anticipated. There have been reports of armored tube kinking both intraorally and extraorally in the prone position. Hence, prompt anticipation of tube kinking is desirable, especially in obese patients (increased neck circumference and submental fat) positioned prone. Herewith, we report two cases of unusual complication of armored tube kinking in prone position in obese patients.

How to cite this article:
Bhatnagar V, Dwivedi D, Datta S G, Tara S. Intraoperative kinking of armored endotracheal tube leading to airway obstruction in obese patients positioned prone for spine surgeries: A report of two cases.J Mar Med Soc 2019;21:83-86

How to cite this URL:
Bhatnagar V, Dwivedi D, Datta S G, Tara S. Intraoperative kinking of armored endotracheal tube leading to airway obstruction in obese patients positioned prone for spine surgeries: A report of two cases. J Mar Med Soc [serial online] 2019 [cited 2023 Mar 24 ];21:83-86
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Full Text


Airway obstruction intraoperatively in prone position is a dreaded complication and etiology may be multifactorial. Mechanical causes such as kinking of endotracheal tube (ETT), kinking of breathing circuit, and stuck inspiratory valve and pathological causes such as severe bronchospasm and air embolism are few of the reasons. Obese patients (body mass index [BMI] more than 30 kg/m2) owing to high submental fat and increased neck circumference are more prone to complications such as ETT kinking in the prone position.[1],[2],[3] Prone positioning of patients during anesthesia is not only associated with predictable changes in the physiology but also with a number of complications, and safe use of the prone position in obese patients requires an understanding of both.[4]

Preoperative optimization is very important for the success of anesthetic intervention and safety of obese patients. We wish to elaborate our perioperative experience in two obese patients in prone position, who landed up with complication of kinking of armored ETT.

 Case Reports

Case 1

A 46-year-old female, 92 kg of weight, 154 cm of height (BMI 38.8 kg/m2), presented for laminectomy and excision for a dumbbell-shaped, intradural extramedullary tumor extending from C5 to T1 (posterior as well as anterolateral approach). The patient was to be operated in prone position and then in supine position for the respective approaches. The patient was bedbound for the last 4 months owing to the weakness caused by the tumor.

On preanesthsia evaluation (PAE), her vital parameters were within normal limits (WNL) (heart rate [HR] 86/min, noninvasive blood pressure (NIBP) 116/88 mmHg, and respiratory rate (RR) 14/min with 98% baseline SpO2 on room air), and she was well oriented in time, space, and person. Motor examination revealed normal bulk, increased tone in both lower limbs (LL) and decreased power in right (2/5) and left (3/5) LL. Power in both upper limbs was 5/5. All deep tendon jerks and superficial reflexes were WNL. On sensory examination, fine touch and pain sensation were decreased in both LL (right >left). Cardiovascular, respiratory, and abdominal examination were WNL.

Airway examination revealed a Mallampati Classification Grade III with adequate mouth opening. The neck was short, stocky with submental fat. Neck extension was <35°. Neck circumference was 49.5 cm with thyromental (TM) distance of 4.5 cm. Basic hemogram, electrocardiography (ECG) and chest X-ray, and biochemistry profile were WNL (hemoglobin was 13 g/dl).

The patient was accepted in the American Society of Anesthesiologist physical status (ASA) III and informed consent was obtained. A plan for difficult airway was conceived. Incentive spirometry was advised and encouraged preoperatively.

The patient was premedicated with 100 mcg fentanyl intravenously (IV), induced with 130 mg propofol and vecuronium 8 mg IV, and intubated with 7.0 mm ID flexometallic tube cuffed ETT using McCoy size 4 blade. ETT position was confirmed by auscultation and end-tidal carbon dioxide (EtCO2). General anesthesia (GA) was maintained with oxygen, air, and sevoflurane with a minimum alveolar concentration (MAC) of 0.8–1.0

Arterial line (left radial artery) cannulation was done for invasive monitoring and central venous access (right subclavian vein) was obtained. Monitoring instituted was HR, arterial blood pressures (ABP), ECG, EtCO2, SpO2, and temperature monitoring. Deep venous thrombosis (DVT) prophylaxis was instituted in the form of pneumatic stockings. Hemodynamics was well maintained.

The patient was turned prone for the posterior approach and ventilation was confirmed after positioning. Head was fixed on pins and two-finger distance was maintained while flexing the chin. After 10 min, a sudden rise in peak airway pressure from 26 to 40 cm H2O was noticed with shark fin appearance of EtCO2 on the monitor, there was increased resistance to manual bag ventilation. The possible mechanical causes (inadequate delivery of tidal volume (Vt) by machine, inspiratory valve stuck on ventilator, kink in the breathing circuit, endobronchial intubation, and inadequate depth of anesthesia) were ruled out. To check for intraoral kinking of ETT, we tried inserting a 14 Fr suction catheter but were not successful beyond 12-cm mark from ETT connector. Intraoral kinking of the ETT was suspected and an oropharyngeal airway was inserted so as to relieve the kink, but the obstruction was not relieved as was evident with the reduced Vt being delivered at high peak airway pressure (42 cm of H2O). Decision to turn patient supine for changing the ETT was taken. Fiber-optic bronchoscopy (FOB) was performed in the supine position, which confirmed a deformity due to kinking in the lumen of the ETT, around 4 cm above the cuff, which led to airway obstruction [Figure 1]. Over gum-elastic bougie, ETT was changed and mechanical ventilation confirmed with auscultation and capnography. Airway pressures normalized to 18 cm H2O along with the EtCO2 tracing. An oropharyngeal airway was introduced for supporting the ETT, and the patient was again turned prone. The surgical decompression in prone as well as supine position went uneventful thereafter. Patient was reversed after completion of surgery (surgical time 6 h) and extubated on table. Postoperatively, the patient was treated with noninvasive ventilation (NIV) as a bridging technique for 4 h.{Figure 1}

Case 2

A 65-year-old female, 82 kg weight, 150 cm height (BMI 36.44), presented as a case of spinal cord tumor (D4–D5) with paraparesis for tumor decompression in prone position.

On PAE, her basal vital parameters were HR 82/min, NIBP 138/88 mmHg, RR 14/min, and 98% SpO2 (room air) and higher mental functions were WNL. Motor examination revealed normal bulk, increased tone, and decreased power (2/5) in both LL. Power in both the upper limbs was 5/5. Deep tendon jerks and superficial reflexes were WNL. On sensory examination, fine touch and pain sensation were decreased in both LL. Cardiovascular, respiratory, and abdominal examination was WNL.

Airway examination revealed Mallampati Classification Grade III, adequate mouth opening, short neck, and submental fat. Neck extension was <40°. Neck circumference was 44.5 cm with TM distance of 4.5 cm. Investigations including ECG were WNL.

The patient was accepted in ASA III; informed consent was obtained. Difficult airway plan was considered. Incentive spirometry advised and encouraged preoperatively.

The patient was premedicated with 80 mcg fentanyl, induced with 120 mg propofol IV, and intubated with 7.5 mm ID armored, cuffed ETT by McCoy size 4 blade and gum-elastic bougie, using vecuronium 8 mg IV. Ventilation was confirmed with auscultation and EtCO2. GA maintained with O2; Air: Sevoflurane (MAC of 0.8–1.0).

Left radial artery for ABP monitoring and right subclavian vein cannulated for central venous access. Pneumatic stockings were given for DVT prophylaxis. The patient required noradrenaline infusion at 0.01–0.04 mg/kg/min for maintenance of hemodynamics intraoperatively.

Adequate precautions were taken, while prone positioning and peak airway pressures stabilized to 28 cmH2O with a Vt of 450 ml. Gradually, peak airway pressure increased to 38 cmH2O with amplified resistance to manual bag ventilation. The possible mechanical causes were ruled out. To check for intraoral kinking of ETT, 14 Fr suction when inserted could not negotiate beyond 12-cm mark from ETT connector. Oropharyngeal airway was inserted orally for decreasing the kink but in vain. The patient could only be ventilated on pressure control mode (PCV) with peak pressure of 30 cmH2O and delivered about 250–280 ml of Vt. Surgeon was notified, but the surgical decompression was almost over, so we managed ventilation with PCV mode and intermittent hyperventilation. The patient was turned supine after surgical decompression. FOB was performed; a deformity around 4.5 cm above the cuff was seen in the lumen of the ETT leading to decrease in the lumen of ETT and resultant airway obstruction. ETT was exchanged over gum-elastic bougie, and mechanical ventilation confirmed with auscultation and capnography. Airway pressures resumed to 22 cmH2O with 450 ml of Vt being delivered. The patient was reversed and extubated uneventfully on table after an arterial blood gas (ABG) analysis revealed arterial oxygen and arterial carbon dioxide values WNL. The patient was given NIV for 4 h postoperatively as a bridging technique on account of her obesity.


Obese patients with increased neck circumference and submental fat lead to greater incidence of complications during mechanical ventilation in the prone position.[4] After turning prone, it is mandatory to keep two-finger distance, while flexing the chin on the chest; otherwise, there is rise in peak airway pressures as well as venous return occlusion making mechanical ventilation difficult.[3],[4]

High airway pressures with shark fin appearance of EtCO2 on monitor indicate manual problems in mechanical ventilation such as obstructed expiratory valve, kink in the breathing circuit, ventilator malfunction, ETT kinking, endobronchial intubation, obstruction of ETT due to secretions, mucus, blood, or loosened spirals in the reinforced ETT.[5] They may also point toward pathologies such as bronchospasm, pneumothorax, or any other pulmonary pathology leading to difficulty in ventilation.[5],[6],[7]

The key to identification of complication is to keep a high degree of suspicion. Confirmation of kink in ETT is done by introduction of a suction catheter in the ETT.[6],[7] The gold standard for identification is fiberoptic inspection of the ETT.[6],[7]

Both our patients were obese, required surgery in prone position, had an increased neck circumference and submental fat, and landed in the complication of ETT kinking intraorally intraoperatively. While in the first patient, kinking happened when the surgical decompression had not begun and we could turn the patient supine, confirm kinking, and replace the ETT with the help of gum-elastic bougie, but in our second case, the surgical decompression had been nearly completed when the kinking of the ETT could be identified.

The maneuver to insert an oral airway to relieve kinking did not help in the first case and was partially helpful in the second case.[7],[8] Thus, we decided to continue with the surgical decompression while notifying the surgeon regarding the complication and managed ventilation with PCV and manual ventilation intermittently to tide over the crisis. The ETT was, however, changed once the patient was turned supine. After adequate ventilation and confirmation by ABG, we could extubate the patient on table. Both the patients were given the bridging with NIV in the intensive care unit for sufficient alveolar recruitment postextubation and for optimization of oxygenation and ventilation.[9]

Kinking of ETT in the prone position is not very common and case reports highlighting the same have been published; however, the incidence of ETT kinking in prone position or in obese patients is not known. Kinking is more common when the ETT is maximally flexed at atlantoaxial joint and also in obese patients due to excessive amount of submental tissue. Reusing reinforced ETT also makes ETT prone for kinking.[10],[11],[12]

To relieve kinking, certain maneuvers can be utilized such as manual straightening of ETT, placement of a Berman intubating airway, and maintaining a proper positioning of head and neck before surgery while giving adequate attention to space between the chin and the chest. Placement of a laryngeal mask airway to tide over crisis has also been reported in one case report.[7],[8]

We used single-use reinforced ETT, but the culprit of ETT kinking in prone position seems more likely the excessive submental fat and requirement of flexion at the atlantoaxial joint. We tried manual straightening as well as insertion of an oral airway to relieve kinking which could not help us in the first patient and was of partial comfort in the second.

Our case report highlights the importance of a constant vigil for unusual events, low threshold for potential complication identification, and vigorous management of the hazards, thereby leading to successful management of a significant problem such as kinking ETT with compromised ventilation intraoperatively.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

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Conflicts of interest

There are no conflicts of interest.


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