Wheezing

Article Author:
Pujan Patel
Article Editor:
Sandeep Sharma
Updated:
3/3/2019 9:44:20 AM
PubMed Link:
Wheezing

Introduction

Wheezing is the symptomatic manifestation of any disease process that causes airway obstruction. Rene Laennec's development of the stethoscope in 1816 has enabled a better appreciation of wheeze at the bedside; in comparison to the previously established practice of ear-to-chest auscultation. Wheeze is a musical, high-pitched, adventitious sound generated anywhere from the larynx to the distal bronchioles during either expiration or inspiration. Modern-day, computerized, waveform analysis has allowed us to characterize wheeze with more precision and given us its definition as a sinusoidal waveform, typically between 100 Hz and 5000 Hz with a dominant frequency of at least 400 Hz, lasting at least 80 milliseconds. Wheeze may be audible without the aid of a stereoscope when the sound is loud, but in most cases, wheezes are auscultated with a stethoscope.

The presence of wheezing does not always mean that the patient has asthma, and a proper history and physical exam are required to make the diagnosis.[1][2][3][4]

Etiology

Wheezing is commonly experienced by people who have asthma; although, it can be heard in people with foreign bodies, congestive heart failure, a malignancy of the airway, or any lesion that causes narrowing of the airways. The presence of wheezing during expiration indicates that the individual’s peak expiratory flow rate is less than fifty percent compared to normal. The quality and duration of wheezing also depend on where in the airways the obstruction is located. In asthma, the wheezing is due to narrowing of the lower airways whereas with malignancies the obstruction is usually in the upper, more proximal airways. In rare cases, wheezing may be heard both during inspiration and expiration. In severe asthma, in fact, no wheeze may be heard as the air flow will be so severely reduced and chest auscultation will be silent. Since any process that reduces airway caliber generates wheeze, below are some of the many of the conditions that can cause wheeze:

  • Respiratory infections (croup, laryngitis)
  • Obstructive airway diseases (asthma, 
  • chronic obstructive pulmonary disease [COPD], anaphylaxis, bronchiolitis)
  • Pulmonary peribronchial edema (congestive heart failure)
  • Vocal cord dysfunction (paradoxical vocal fold motion [PVFM], vocal cord paralysis)
  • Post nasal drip
  • Airway compression: Intrinsic or extrinsic (squamous cell carcinomas, goiter)
  • Hyperdynamic airway collapse (tracheobronchomalacia)
  • Carcinoid tumors
  • Foreign body inhalation
  • Forced exhalation by normal individuals[5][6][7]

Epidemiology

The reported prevalence of wheezing amongst young children between 2 to 3 years of age is reported around 26% in the United States. The global prevalence is lower in the adolescent age range approximately 12%. Global surveys reveal a similar prevalence in adults, with European and Australian surveys reporting the highest prevalence rates, up to 17%.[8]

Pathophysiology

Wheezes are thought to be the product of fluttering vibrations of narrowed airway walls, induced by a diminished air flow velocity. The characteristics of their sound include how loud they are (i.e., the amplitude), how long they last and how intense (i.e., high pitched) they sound. A physiologic trial done in the 1980s identified the determinants of the pitch of a sound that is generated within collapsible tubes. It was determined that the pitch of a wheeze is a reflection of the stiffness, the thickness and longitudinal tension of the airway's wall also. Subsequent clinical studies have shown that the pitch and more so duration of wheeze are the only two characteristics that correlate well with the severity of airway obstruction. The degree of bronchial obstruction is also proportional to the number of airways that are producing wheeze. And so, the amplitude of auscultated wheeze has no bearing on the severity of airway obstruction. At the very severe end of airway obstruction, if there is very little to no air flow, then no wheeze will be heard despite severe airway obstruction.[9][10][11][12]

History and Physical

History should be targetted toward the various etiologies of wheezing listed above. For example, patients who have had head and neck cancer surgery and/or radiation may develop vocal cord paralysis. Additionally, a prior history of endotracheal intubation can alert one to the possibility of tracheal, subglottic stenosis.

Physical examination of the trachea and thorax will identify wheeze. Wheeze associated with asthma is most commonly heard during expiration; however, wheeze is neither sensitive or specific for asthma, so the wheezes can certainly extend into inspiration also. Upper airway obstruction from tonsilar hypertrophy can be evaluated with an oral examination and palpation of the neck could identify a goiter.[13]

Evaluation

When wheezing is heard, some work up is required because it is an abnormal sound. The first imaging test of choice in a patient with wheezing is a chest x-ray to look for a foreign body or a lesion in the central airway. In the non-acute setting, if asthma is suspected, the next step is to obtain baseline pulmonary function tests with bronchodilator administration. Following this, it may be necessary perform an airway challenge test with a bronchoconstrictive agent such as methacholine. If the wheezing resolves with a bronchodilation agent, a tumor or mass as the cause is a much less likely consideration. If there is no resolution after a breathing treatment, and a tumor or mass is suspected, then a CT scan of the chest and bronchoscopy may be required if possible malignancy is suspected on CT.[7]

Treatment / Management

Treatment predominantly revolves around the suspected etiology of the wheezing. The ubiquitous approach to ensuring Airway, Breathing, and Circulation (ABCs) are stable is the priority. Those with signs of impending respiratory failure may require either noninvasive positive pressure ventilation or invasive mechanical ventilation following endotracheal intubation. In cases of anaphylaxis, epinephrine would be required. Nebulized, short-acting, b2 agonist such as albuterol and nebulized short-acting muscarinic antagonists are often administered while further workup is being performed.[7]

Differential Diagnosis

Other lung sounds that can be mistaken for or that overlap with wheezes are rhonchi and stridor. Rhonchi share similar characteristics to wheezes, with the main difference being a lower dominant frequency of fewer than 200 MHz. This lower frequency is described as a snoring-like sound. Stridor is a higher pitched and higher amplitude sound that is due to turbulent air flow around a region of upper airway obstruction. It is typically an inspiratory sound that is far more pronounced when auscultated over the trachea than the thorax.[14]

Enhancing Healthcare Team Outcomes

Wheezing is a common sign encountered in clinical practice by the nurse practitioner, primary care provider, internist, cardiologist and the pulmonologist. When wheezing is heard, some work up is required because it is an abnormal sound. The first imaging test of choice in a patient with wheezing is a chest x-ray to look for a foreign body or a lesion in the central airway. In the non-acute setting, if asthma is suspected, the next step is to obtain baseline pulmonary function tests with bronchodilator administration. Following this, it may be necessary perform an airway challenge test with a bronchoconstrictive agent such as methacholine. If the wheezing resolves with a bronchodilation agent, a tumor or mass as the cause is a much less likely consideration. If there is no resolution after a breathing treatment, and a tumor or mass is suspected, then a CT scan of the chest and bronchoscopy may be required if possible malignancy is suspected on CT.


References

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