Auscultatory Findings in Chronic Asthma
The primary auscultatory finding in chronic asthma is wheezing during normal breathing or a prolonged phase of forced exhalation, though importantly, the absence of wheezing does not rule out asthma since the disease is variable and signs may be absent between episodes. 1
Key Auscultatory Features
Primary Findings
- Wheezing: The hallmark sound, occurring during normal breathing or particularly during forced exhalation 1
- Prolonged expiratory phase: A critical finding that indicates airflow obstruction 1
- Forced expiratory wheeze (FEW): May be an early sign of airway obstruction in asthmatic patients 2
Important Clinical Context
The physical examination findings that increase the probability of asthma include 1:
- Chest findings:
- Sounds of wheezing during normal breathing
- Prolonged phase of forced exhalation
- Hyperexpansion of the thorax
- Use of accessory muscles
- Appearance of hunched shoulders
- Chest deformity
Critical Pitfalls
The absence of wheezing does NOT exclude asthma. This is a crucial point that clinicians must understand - asthma is highly variable, and physical examination findings may be completely absent between episodes 1. Studies have shown that wheezing may not be as sensitive as changes in basic lung sounds in acute airway narrowing 2, and bronchoprovocation studies demonstrate that increases in frequency and/or intensity of lung sounds correlate better with lung function than wheezing alone 2.
Mechanism of Lung Sound Changes
Research indicates that 2:
- Narrower airways produce higher frequency breathing sounds
- Bronchial sounds (higher than normal breathing sounds) suggest airway narrowing or inflammation
- Both inspiratory and expiratory wheezes likely share the same generation mechanism (flutter/flow limitation), either localized or generalized
- Airway wall oscillation and vortex shedding in central airways are the most likely mechanisms generating expiratory wheezes
Clinical Implications
Because physical examination alone is unreliable for diagnosis, spirometry is essential as an objective measure - the medical history and physical examination are not reliable means of excluding other diagnoses or assessing lung status 1. The variability of asthma means that a patient may have completely normal auscultatory findings during stable periods yet have significant underlying airway inflammation and hyperresponsiveness.