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Dear List Re cardiac arrest following asthma (sorry it's a bit long) The underlying reason for the cardiac arrest in the asthmatic patient described by Dave is probably air trapping, it is not consolidation. Searches of clinical trials involving ketamine etc don't address the fundamental problem of cardiac arrest in asthma. In patients with acute exacerbations of asthma/COPD, bronchoconstriction and respiratory mucosal oedema cause airway narrowing which means that gas cannot escape easily from the alveolar space during expiration. This causes alveolar positive pressure at the end of expiration known as intrinsic PEEP(positive end expiratory pressure). As this increases, so does intrathoracic pressure, thus decreasing venous return and, similar to the mechanism of cardiac tamponade cardiac arrest can and does ensue. The increase in iPEEP doesn't affect proximal airway pressure until a critical point is reached, therefore it may be possible to ventilate the patient with only some resistance, and then suddenly it becomes impossible. The management of a patient with deteriorating asthma/COPD who arrests should include consideration of allowing a prolonged exhalation to allow alveolar emptying (up to 20 seconds and applying a physical squeeze to the chest if necessary)-this alone will sometimes restore cardiac output. The same situation occurs in ICU patients with asthma and COPD (suddenly the ventilator won't deliver a tidal volume, blood pressure plummets and patient suffers an EMD arrest), unless hypoventilation strategies are used. Further breathing management should include 100% O2 but only ventilating with very small tidal volumes and a rate of a few breaths (even 1-2) a minute to allow adequate expiration-it doesn't matter what happens to the CO2. Adrenaline is useful for continuing arrest because of bronchodilator effects. Attempted ventilation at 10 breaths a minute and using normal tidal volumes in the arrest situation will guarantee failure. Bilateral pneumothoraces are extremely rare in these patients but airtrapping is commonly not recognised and is far commoner (and fatal if not properly treated). Only after treating airtrapping should pneumothoraces be considered. I'll post up some references on asthma and cardiac arrest in the next few days if anyone wants Francis Andrews ---------------------- Dr Francis J Andrews FFAEM Lecturer in Intensive Care Medicine Department of Medicine University of Liverpool [log in to unmask]