The Science Journal of the American Association for Respiratory Care

1996 OPEN FORUM Abstracts

ULTRA HIGH FREQUENCY VENTILATION (UHFV) IN THE TREATMENT OF SEVERE, CONFINED INHALATION OF A MILITARY SMOKE GRENADE

Lynn Mellecker, RRT. D. Michael Shasby, MD, LuAnn Wilford, RRT, University of Iowa Hospitals & Clinics, Iowa City, IA 52242

Introduction: A military smoke grenade contains hexachloroethane, zinc oxide, aluminum powder, silicon and potassium nitrate. Upon detonation these substances create zinc chloride. When inhaled, zinc chloride is highly caustic to mucous membranes and has been associated with fatal, necrotizing pulmonary lesions. A literature review confirmed the severity of respiratory failure and extreme mortality with conventional therapy. We describe the use of the Adult Star 1010 (Infrasonics Inc., San Diego, CA) Ultra High Frequency Ventilator in a case of high exposure to a detonated "white" smoke grenade. Case Summary: A 21 year old male was transferred to the medical center three days post exposure to detonation of a smoke grenade in the confines of a cave. Prior treatment included aerosolized bronchodilators, steroids and supplemental oxygen. The arterial blood gas upon admission was 7.46/35/41 (pH/PCO_{2}/PO_{2} respectively) on 6 Lpm oxygen cannula. After 10 days of accelerated aerosolized bronchodilator, steroid and supplemental oxygen therapy, his blood gas was 7.43/44/69 on 100% oxygen by mask. Chest radiograph revealed diffuse, opacified pockets without evidence of a pneumothorax. Thereafter, a tension pneumomediastinum developed and was treated with bilateral chest tubes. Secondary to tachypnea and hypoxemia, he was intubated. Pressure Regulated Volume Control (PRVC) and Pressure Control (PC) modes of ventilatory support were used. After 12 days of aggressive ventilation and nitric oxide therapy, the air leak worsened and on PC Inverse Ratio Ventilation with 100% oxygen, the blood gas was 7.37/58/35 resulting in an Oxygenation Index (OI) of 63 [an OI > 40 has been associated with a mortality of 90%]. UHFV was initiated in hopes of reducing the magnitude of air leak and the intrathoracic mean pressure while maintaining acceptable blood gases, i.e., an improved OI. Within 5 minutes of initiating UHFV, the pulse oximeter rose from 56 to 80% and within 24 hours to a mean value of 98% with an OI of 23 (7.44/43/81 on 90% oxygen). Over the next 31 days of UHFV, his respiratory status stabilized, while various infections were treated. The decision to establish a tracheotomy for an airway resulted in returning the patient to conventional ventilation. Following 82 days of aggressive rehabilitation and conventional ventilatory support, the patient weaned to a 2 Lpm oxygen cannula with a blood gas of 7.39/49/72 (D_{L}CO at 22% predicted). Tracheostomy and jejunostomy tubes were removed 14 days later. Following two months of home-based rehabilitation, a repeat pulmonary function test revealed an improved D_{L}CO at 41% of predicted. No untoward results could be associated with UHFV compared to conventional ventilation therapy. Discussion: Reports describing the concentrated inhalation of the contents of a detonated smoke grenade associate a 100% fatality rate with conventional ventilation. Ultra High Frequency Ventilation can be life sustaining in the face of severe respiratory failure unresponsive to aggressive conventional ventilatory support.

Reference: OF-96-170

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