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Why to Use
Placing the ETT too deep may cause right mainstem intubation, hypoxemia, and pneumothorax. However, placing the ETT too shallow may risk injury to the vocal cords and accidental extubation. Standard approaches to verify ETT depth (eg, bilateral auscultation) are insensitive. Use of lower tidal volumes appears to prevent the development of acute respiratory distress syndrome, even in patients who do not have lung injury.
When to Use
Use in adult patients (aged > 20 years) requiring orotracheal intubation.
Chula formula: ETT depth = 0.1 * [height (cm)] + 4
Joshua Farkas, MD
Obtain chest radiograph and measurement of CO2 level (eg, end-tidal CO2 or blood gas analysis) to confirm ETT position and adequacy of ventilation.
The Chula formula was developed and validated by Techanivate et al (2005) at King Chulalongkorn Memorial Hospital in Thailand. The authors prospectively validated the use of this formula among 100 patients in Thailand. Patients were intubated and the ETT placed according to the formula. Subsequently, a bronchoscope was used to determine the relationship among the ETT, carina, and vocal cords. The distance between the ETT and carina ranged between 1.9-7.5 cm. No patient was at immediate risk of endobronchial intubation. The upper border of the ETT cuff was always > 1.9 cm below the vocal cords, avoiding risk of laryngeal trauma or inadvertent extubation.
Pak et al in 2010 and Hunyady et al in 2008 developed similar assessments of optimal ETT placement. The average of the 3 scores (Pak, Hunyady, and Chula) is nearly identical to the Chula formula.
Anchalee Techanivate, MD
The Blast Lung Injury Severity Score stratifies primary blast lung injuries into 3 categories to guide ventilator treatment.
Why to Use
The Blast Lung Injury (BLI) Severity Score is useful in guiding triage decisions in the setting of mass casualties, determining ventilation treatment, and predicting outcomes. BLI severity correlates with the likelihood of developing acute respiratory distress syndrome (ARDS), and can be helpful to delineate patients who will require more aggressive and potentially unconventional respiratory care (eg, nitric oxide, high-frequency jet ventilation, independent lung ventilation, or extracorporeal membrane oxygenation).
When to Use
Use the BLI Severity Score in patients who have sustained blast injury and have respiratory symptoms (eg, cough, cyanosis, dyspnea, hemoptysis).
Intubated patients require the following ventilation management:
Jennie Kim, MD
Travis Polk, MD
The original BLI Severity Score was proposed in 1999 by Pizov et al. The study evaluated 15 patients with primary BLI after explosions on 2 civilian buses. BLI Severity scores were compared to Murray scores for acute lung injury at 6 and 24 hours after injury; at 24 hours, there was good correlation between the proposed BLI score and the modified Murray score.
Three of the 3 patients (100%) with severe BLI who were still alive after 24 hours (1 patient died within 24 hours from intrapulmonary hemorrhage after being placed on extracorporeal membrane oxygenation) and 2 of 6 patients (33%) with moderate BLI developed acute respiratory distress syndrome (ARDS) (Murray score > 2.5). None of the 5 patients with mild BLI developed ARDS. Other unconventional respiratory therapies such as independent lung ventilation, high-frequency jet ventilation, and nitric oxide were used in patients with severe BLI with improvements in their PaO2 levels. When comparing mortality rates, 4 patients with severe BLI died, all 6 patients with moderate BLI survived, and 1 of the 5 patients with mild BLI subsequently died from a traumatic head injury.
One year after the study by Pizov et al, Hirshberg et al conducted a follow-up study of the 11 surviving original patients. None of the 11 survivors had pulmonary-related complaints, and lung physical examinations were normal with complete resolution of chest radiograph findings.
In comparison, Avidan et al, in 2005, evaluated 29 patients with primary BLI, and only 1 patient had died (death occurred 24 days after admission from sepsis and multiple organ failure). The authors concluded that death because of BLI in patients who survived the explosion is unusual. Although these 29 patients were not categorized by BLI severity scores, there were 7 patients with PaO2 / FiO2 ratios < 60, 4 patients requiring positive end-expiratory pressure (PEEP) > 10 cm H2O, and 3 patients requiring unconventional therapies such as high-frequency ventilation or nitric oxide inhalations. The decreased mortality rate compared to Pizov et al, despite the presence of patients with characteristics of severe BLI, may be attributed to improvements in critical care and respiratory management.
The study also assessed long-term outcomes by contacting 21 of 28 survivors (75%) from 6 months to 21 years after discharge. Sixteen patients (76%) were free of respiratory symptoms and did not require respiratory therapy. Five patients (24%) reported respiratory symptoms but 2 of the 5 had a past medical history of asthma and another 2 of the 5 were contacted less than 1 year after injury.
Reuven Pizov, MD
Copyright © MDCalc • Reprinted with permission.
Eric J. Morley, MD, MS ; Scott Johnson, MD; Evan Leibner, MD, PhD; Jawad Shahid, MD;
June 1, 2016
July 1, 2019