What is the immediate cause of death in a patient with severe bronchial asthma?

Immediate Cause of Death in Severe Bronchial Asthma

The most common immediate cause of death in severe bronchial asthma is asphyxia resulting from severe airway obstruction, bronchoconstriction, mucous plugging, and airway inflammation leading to respiratory failure. 1

Pathophysiological Mechanisms Leading to Death

The fatal pathway in severe asthma involves three key pathophysiological abnormalities that culminate in asphyxia:

• Severe bronchoconstriction that prevents adequate airflow 1
• Airway inflammation with eosinophilic and neutrophilic infiltration 1
• Mucous plugging that obstructs airways 1

These mechanisms lead to progressive hypoxemia and hypercarbia, ultimately resulting in cardiopulmonary arrest from asphyxia rather than primary cardiac causes. 1

Life-Threatening Clinical Features Preceding Death

Patients who die from severe asthma typically exhibit specific markers of impending respiratory failure:

• Peak expiratory flow <33% of predicted or personal best 1, 2
• Silent chest, cyanosis, or feeble respiratory effort indicating near-complete airway obstruction 1, 2
• Bradycardia or hypotension from severe hypoxemia and decreased venous return 1
• Exhaustion, confusion, or coma from cerebral hypoxia 1, 2

Arterial Blood Gas Markers of Imminent Death

Critical blood gas abnormalities that predict fatal outcomes include:

• Normal (5-6 kPa) or elevated PaCO2 in a breathless asthmatic patient - this represents ventilatory failure and impending respiratory arrest 1
• Severe hypoxia with PaO2 <8 kPa despite oxygen therapy 1
• Low pH or high H+ concentration indicating severe respiratory acidosis 1

The presence of a normal or elevated CO2 in an acutely breathless asthmatic is particularly ominous, as these patients should be hyperventilating and hypocapnic; normocapnia indicates exhaustion and imminent respiratory arrest. 1

Secondary Causes and Complications

While asphyxia is the primary mechanism, death can also result from:

• Complications of severe asthma including tension pneumothorax, lobar atelectasis, pneumonia, and pulmonary edema 1
• Cerebral anoxia from prolonged hypoxemia 3
• Cardiopulmonary arrest secondary to severe hypoxemia and acidemia 3, 4
• Barotrauma and ventilator-associated complications in mechanically ventilated patients 3

Cardiac causes of death are explicitly noted to be less common than asphyxia. 1

Inflammatory Patterns in Fatal Asthma

Pathological studies reveal distinct inflammatory patterns in patients dying from status asthmaticus:

• Neutrophilic predominance when death occurs within several hours of attack onset, rather than the typical eosinophilic pattern of milder asthma 1
• Persistent eosinophilic/lymphocytic inflammation despite high-dose corticosteroids in some refractory cases 1

Critical Pitfall to Avoid

The severity of acute asthma attacks is often underestimated by patients, relatives, and physicians due to failure to obtain objective measurements (peak flow, blood gases), which directly contributes to preventable deaths. 1, 2 This underestimation delays appropriate aggressive treatment and hospital admission, allowing progression to fatal asphyxia.