What non‑fluid‑overload causes can produce wheezing?

Non-Fluid Overload Causes of Wheezing

Wheezing results from narrowed airways due to bronchospasm, airway inflammation, excessive secretions, structural obstruction, or smooth muscle constriction—not just fluid overload.

Primary Respiratory Causes

Obstructive Airway Diseases

• Asthma produces variable, intermittent wheezing that is typically worse at night and provoked by specific triggers including exercise, allergens, cold air, and respiratory infections 1
• COPD presents with progressive wheezing accompanied by chronic cough and breathlessness, confirmed by spirometry showing FEV1 <80% predicted with FEV1/FVC <0.7 and minimal reversibility 1
• Both conditions demonstrate diffuse, bilateral, polyphonic wheezing that is predominantly expiratory 1

Bronchial Obstruction and Secretions

• Excessive bronchial secretions from any cause narrow the airway lumen and produce wheezing, as seen with cholinergic toxicity or severe bronchorrhea 1
• Bronchospasm from smooth muscle constriction occurs in reactive airways, chemical exposures (including nerve agents), and medication effects 1
• Airway edema from inflammation, infection, or chemical injury causes luminal narrowing and wheeze production 2

Structural and Mechanical Causes

Upper Airway Obstruction

• Laryngeal edema or spasm produces stridor (a loud musical wheeze of constant pitch) rather than typical lower airway wheezing 1, 2
• Foreign body aspiration causes localized airway obstruction with wheezing, particularly in children 3
• Tracheal stenosis (post-intubation, post-tracheostomy, or from intrinsic/extrinsic masses) produces monophonic wheezing loudest over central airways 1

Mass Lesions

• Endobronchial tumors cause fixed airway obstruction with persistent, localized wheezing 1, 2
• Extrinsic compression from mediastinal masses, lymphadenopathy, or vascular structures narrows airways mechanically 2

Infectious and Inflammatory Causes

• Pneumonia with associated bronchospasm or airway inflammation produces wheezing alongside other infectious signs 1
• Acute bronchitis causes temporary airway inflammation and increased secretions leading to wheeze 1
• Bronchiectasis results in chronic airway damage with persistent secretions and recurrent wheezing 1

Pharmacologic and Toxic Causes

• Anticholinesterase agents (including nerve agents and pyridostigmine) increase airway resistance through heightened muscarinic activity causing bronchial smooth muscle contraction 1
• Beta-blocker medications can precipitate bronchospasm in susceptible individuals 1
• Aspirin/NSAID sensitivity triggers bronchospasm in certain asthmatic patients 1

Critical Diagnostic Pitfall

A common and dangerous error is assuming wheezing in a critically ill patient represents only one etiology. In combined casualties (trauma plus chemical exposure) or complex medical patients, wheezing may simultaneously reflect bronchospasm, excessive secretions, AND fluid overload 1. The presence of moist rales, prolonged expiration, and copious secretions alongside wheezing should prompt consideration of multiple concurrent mechanisms rather than a single cause 1.

Mechanism of Wheeze Production

Wheezes are continuous, high-pitched sounds (>400 Hz) produced by oscillation of opposing airway walls when luminal narrowing creates critical airflow velocity 4, 2. The pitch depends on airway wall mass, elasticity, and flow velocity—not the severity of obstruction 4. Importantly, wheeze intensity and pitch do not correlate with degree of airflow obstruction, and severe obstruction may produce a "silent chest" with minimal wheeze 1, 4.