Evaluation of Diagnostic Accuracy of Airway Ultrasound for Inhalational Burn Injury

Aims and objective

Primary objective â€“ To correlate the findings of ultrasonography with fiberoptic bronchoscopy in patients with suspected inhalational injury

Secondary objective

1. To identify airway edema
2. To identify the need for intubation in patients with suspected inhalational injury using

ultrasound

Type of study: A Prospective Correlational Observational Trial

Duration of study: Cases will be taken up till sample size is achieved

Sample size : Since this study has not been done before, the study will be done as a pilot on 50 patients.

Place of study: The study will be conducted at the Department of Anaesthesiology ,Pain Medicine and Critical care ,All India Institute of Medical Sciences , New Delhi.

Inclusion criteria

1. Age >18 years
2. Patients presenting to burns emergency with inhalational/ suspected inhalational

injury

Exclusion criteria

1. Refusal to consent
2. Patients requiring urgent intubation in view of threatened airway
3. Associated airway or maxillofacial traumaConsent: Consent for the study will be obtained as per the Declaration of Helsinki. The patients will be well informed and explained in their language that they are participating in a study. They will be explained in person and written consent will be obtained from the patient. Patients will be made aware of their right to withdraw from the study at any time without any adverse effects on their clinical care.

Randomisation: Randomisation can not be ensured due to the nature of presentation of the cases.

Blinding: Two separate anaesthesiologists will be doing the airway assessments. One anaesthesiologist will conduct the airway examination and fibreoptic bronchoscopy. The second anaesthesiologist will be doing the ultrasound of the airway and will be unaware of the airway and FOB findings.

Methodology

After obtaining written informed consent, the patient’s baseline hemodynamic parameters will be noted. Oral and nasal cavity will be examined for the presence of any soot, mucosal ulcerations and erythema, singed nasal hair. Symptoms like dyspnea, hoarsness, stridor will be observed. Requirement of oxygen will be noted.

A bedside point of care ultrasound (Sonosite©) of the airway will be done by an experienced anesthesiologist at the initial presentation to the intensive care unit using a high frequency linear transducer (5-12 MHz). The person doing the ultrasound will be unaware of the airway

findings on general examination and FOB. The patient will be lying supine with neck slightly extended with spontaneous breathing. Transverse and longitudinal scan will be done from the submandibular region till the tracheal rings in a sequential manner with specific focus on the region above and below the thyroid cartilage.

The vocal cords will be identified and confirmed by patient phonation. External identification of the thyroid cartilage by physical exam should guide placement of the ultrasound transducer in the transverse plane at the level of the thyroid cartilage. The transducer will then be slid superiorly and inferiorly in the transverse plane until the vocal cords are clearly identified. Evaluation of the vocal cords will be done at rest and during phonation. This region, along with the regions above and below the vocal cords from the submandibular region to the base of the neck will be interrogated for asymmetry.

In the longitudinal scan the transducer will be placed vertically at 1–1.5 cm medial and aligned to the lateral surface of thyroid cartilage lamina where the arytenoid cartilage will be in the back of the oblique line of thyroid cartilage. The transducer will be applied at the right and left sides of the thyroid cartilage lamina and the right and left arytenoid cartilage and anteroposterior and craniocaudal diameters will be observed separately. (13)

The false vocal cords, arytenoids and true vocal cords will be identified. The presence of airway edema will be evaluated by measuring the laryngeal air column width, tracheal wall thickness, thickness of the vocal cords, arytenoids for false vocal cord fullness, the inter- arytenoid distance using ultrasound caliper method.

The findings will then be correlated with using fiberoptic bronchoscopy in the patient using airway preparation and sedation. FOB will be done by an anesthesiologist not participating in the USG examination and will be blinded to the USG findings. The fiberoptic grading will be done according to the FOB classification of inhalation injury: prediction of acute lung injury.(14)

Negative G0

1. G1  Mild edema and hyperemia, with or without carbon soot
2. G2  Severe edema and hyperemia, with or without carbon soot
3. G3  Ulcerations, necrosis, absence of both cough reflex and bronchial secretions (dry)