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    Blast Lung Injury Severity Score

    Stratifies primary blast lung injuries into three categories to guide ventilator treatment.
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    INSTRUCTIONS

    Use in patients who have sustained blast injury and have respiratory symptoms (e.g. cough, cyanosis, dyspnea, hemoptysis).

    When to Use
    Pearls/Pitfalls
    Why Use

    Patients with respiratory symptoms after blast injury.

    • Primary blast injury (PBI) occurs when a blast wave accelerates and decelerates while traveling through tissues of varying density. Thus, PBI affects organs with greater air-tissue interfaces such as auditory, pulmonary, and gastrointestinal systems.
    • Primary blast lung injury (BLI) is radiological and clinical evidence of acute lung injury occurring after blast injury that is not due to secondary or tertiary blast injury. The pathophysiology is thought to be due to capillary rupture within alveoli leading to hemorrhage and pulmonary edema, which then reduce gas exchange, causing hypoxia and hypercarbia.
    • Clinical suspicion of primary BLI should be high after blast injury within an enclosed space, as the blast wave becomes amplified as it reflects off of the structural walls (Leibovici 1996).
    • Characteristic chest x-ray shows bilateral diffuse opacities in a “butterfly” pattern. Patients present with hypoxemia with associated pneumothoraces, bronchopleural fistulae, or hemoptysis.
    • In the studies, patients diagnosed with BLI were intubated immediately or within 2 hours of presentation due to respiratory decompensation. Thus, patients breathing spontaneously and adequately 2 hours after injury are unlikely to require mechanical ventilation because of BLI alone (Pizov et al 1999, Avidan et al 2005).
    • 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 (e.g. nitric oxide, high-frequency jet ventilation, independent lung ventilation, or extracorporeal membrane oxygenation).
    >200
    60 to 200
    <60
    Localized lung infiltrates
    Bilateral or unilateral lung infiltrates
    Massive bilateral lung infiltrates
    No
    Yes

    Result:

    Please fill out required fields.

    Next Steps
    Evidence
    Creator Insights

    Advice

    • Screening chest x-rays for asymptomatic patients is not recommended (Matthews et al 2015), as patients with blast lung injury (BLI) present either immediately or early with hypoxemia. Contrary to previous belief that the clinical picture of BLI may develop over 24 to 48 hours, studies have shown that patients do not present with a delay in manifestation of lung injury (Pizov et al 1999, Avidan et al 2005).
    • Similarly, it was previously suggested that tympanic membrane (TM) rupture, the most common primary blast injury, was a marker for increased risk of development of BLI. Studies have shown that TM perforation is in fact poorly correlated with BLI (Leibovici et al 1999, Ballivet de Regloix 2017).
    • Low inspiratory pressure with avoidance of positive end-expiratory pressure (PEEP) is ideal in BLI in order to avoid secondary barotrauma, arterial air embolism, or pneumothorax. However, patients with blast lung often have injury patterns similar to acute respiratory distress syndrome (ARDS) and require positive pressure ventilation (PPV) and PEEP.
    • Other treatment considerations include avoiding aggressive intravenous hydration after physiology capture, as it can worsen pulmonary edema, and considering the need for a prophylactic thoracostomy tube before air transportation.

    Management

    Intubated patients require the following ventilation management:

    • Mild BLI patients will usually require volume-controlled or pressure support ventilation modes. PEEP requirement is ≤5 cm H₂O.
    • Moderate BLI will use conventional ventilator modes, including inverse-ratio ventilation as needed. PEEP requirement is 5-10 cm H₂O.
    • Severe BLI will use conventional ventilator modes and commonly require additional therapies such as nitric oxide, high-frequency jet ventilation, independent lung ventilation, or extracorporeal membrane oxygenation. PEEP requirement is >10 cm H₂O.

    Formula

    Addition of the selected points:

     

    Value

    Points

    PaO/FiO

    >200

    0

    60 to 200

    1

    <60

    2

    Chest x-ray

    Localized lung infiltrates

    0

    Bilateral or unilateral lung infiltrates

    1

    Massive bilateral lung infiltrates

    2

    Bronchial pleural fistula

    No

    0

    Yes

    1

    Facts & Figures

    Interpretation:

    BLI Severity Score

    Severity

    ARDS Risk (ARDS 24 hrs post-injury)*

    BLI-associated mortality*

    0

    Mild

    ~0%

    ~0**

    1-4

    Moderate

    33%

    ~0%

    5

    Severe

    100%

    75%

    *From Pizov et al 1999. Note the study was small (n = 10 patients). A more recent study by Avidan et al in 2005 saw 1 mortality out of 29 patients but not primarily due to pulmonary issues.

    **One patient with mild BLI died from head injury.

    Evidence Appraisal

    The original blast lung injury (BLI) severity score was proposed in 1999 by Pizov et al. The study evaluated 15 patients with primary BLI after explosions on two civilian buses. BLI Severity Scores were compared to Murray Scores for acute lung injury at 6 and 24 hours after injury, and at 24 hours, there was good correlation between the proposed BLI score and the modified Murray Score.

    Three of the three (100%) patients with severe BLI who were still alive after 24 hours (one patient died within 24 hours from intrapulmonary hemorrhage after being placed on extracorporeal membrane oxygenation), and two of the six (33%) patients with moderate BLI developed ARDS (Murray Score >2.5). None of the five 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, three of the four patients with severe BLI died, all six of the patients with moderate BLI survived, and one of the five patients with mild BLI 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 resolutions of chest radiograph findings.

    In comparison, Avidan et al in 2005 evaluated 29 patients with primary BLI, and only one patient died 24 days after admission from sepsis and multi-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 seven patients with PaO₂/FiO₂ ratio <60, four patients requiring PEEP >10 cm H₂O, and three 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 improving critical care and respiratory management.

    The study also assessed long term outcomes by contacting 21 of 28 (75%) survivors from 6 months to 21 years after discharge. 16 patients (76%) were free of respiratory symptoms and did not require respiratory therapy. Five (24%) reported respiratory symptoms, but two of these five had a past medical history of asthma, and another two of the five were contacted less than one year after injury.

    Literature

    Other References

    Research PaperMatthews ZR, Koyfman, A. Blast Injuries. J Emerg Med. 2015 Oct;49(4):573-87.Research PaperScott TE, Kirkman E, Haque M, Gibb IE, Mahoney P, Hardman JG. Primary blast lung injury – a review. Br J Anaesth. 2017 Mar 1;118(3):311-316.Research PaperLeibovici D, Gofrit ON, Stein M, Shapira SC, Noga Y, Heruti RJ, Shemer J. Blast injuries: bus versus open-air bombings—a comparative study of injuries in survivors of open-air versus confined-space explosions. J Trauma. 1996 Dec;41(6):1030-5.Research PaperLeibovici D, Gofrit ON, Shapira SC. Eardrum Perforation in Explosion Survivors: Is It a Marker of Pulmonary Blast Injury?. Ann Emerg Med. 1999 Aug;34(2):168-172.Research PaperBallivet de Regloix S, Crambert A, Maurin O, Lisan Q, Marty S, Pons Y. Blast injury of the ear by massive explosion: a review of 41 cases. J R Army Med Corps. 2017 Oct:163(5):333-338. Research PaperCannon JW, Hofmann LJ, Glasgow SC, Potter BK, Rodriguez CJ, Cancio LC, Rasmussen TE, Fries CA, Davis MR, Jezior JR, Mullins RJ, Elster EA. Dismounted Complex Blast Injuries: A Comprehensive Review of the Modern Combat Experience. J Am Coll Surg. 2016 Oct;223(4):652-664.e8.
    Dr. Reuven Pizov

    About the Creator

    Reuven Pizov, MD, is a professor of anesthesiology at Hadassah Medical Center in Jerusalem, Israel. He is also the chair of the department of anesthesiology, intensive care and pain medicine at Carmel Medical Center. Dr. Pizov has authored several peer-reviewed studies in the field of anesthesiology.

    To view Dr. Reuven Pizov's publications, visit PubMed

    Content Contributors
    • Jennie Kim, MD
    Reviewed By
    • Travis Polk, MD, FACS
    About the Creator
    Dr. Reuven Pizov
    Partner Content
    Content Contributors
    • Jennie Kim, MD
    Reviewed By
    • Travis Polk, MD, FACS