Crackles are the clicking, rattling, or

crackling noise Crackling noise arises when a system is subject to an external force and it responds via events that appear very scale invariant, similar at many different scales. In a classical system there are usually two states, on and off. However, sometimes ...

s that may be made by one or both

lung The lungs are the primary Organ (biology), organs of the respiratory system in many animals, including humans. In mammals and most other tetrapods, two lungs are located near the Vertebral column, backbone on either side of the heart. Their ...

s of a

human Humans (''Homo sapiens'') or modern humans are the most common and widespread species of primate, and the last surviving species of the genus ''Homo''. They are Hominidae, great apes characterized by their Prehistory of nakedness and clothing ...

animal Animals are multicellular, eukaryotic organisms in the Biology, biological Kingdom (biology), kingdom Animalia (). With few exceptions, animals heterotroph, consume organic material, Cellular respiration#Aerobic respiration, breathe oxygen, ...

with a

respiratory disease Respiratory diseases, or lung diseases, are pathological conditions affecting the organs and tissues that make gas exchange difficult in air-breathing animals. They include conditions of the respiratory tract including the trachea, bronchi, ...

during

inhalation Inhalation (or inspiration) happens when air or other gases enter the lungs. Inhalation of air Inhalation of air, as part of the cycle of breathing, is a vital process for all human life. The process is autonomic (though there are exceptions ...

, and occasionally during exhalation. They are usually heard only with a

stethoscope The stethoscope is a medicine, medical device for auscultation, or listening to internal sounds of an animal or human body. It typically has a small disc-shaped resonator that is placed against the skin, with either one or two tubes connected t ...

("on

auscultation Auscultation (based on the Latin verb ''auscultare'' "to listen") is listening to the internal sounds of the body, usually using a stethoscope. Auscultation is performed for the purposes of examining the circulatory system, circulatory and resp ...

"). Pulmonary crackles are abnormal breath sounds that were formerly referred to as rales. ''Bilateral crackles'' refers to the presence of crackles in both lungs. Basal crackles are crackles apparently originating in or near the base of the lung. ''Bibasal crackles'', also called ''bilateral basal crackles'', are crackles heard at the bases of both the left and right lungs. Crackles are caused by the "popping open" of small airways and alveoli collapsed by fluid,

exudate An exudate is a fluid released by an organism through pores or a wound, a process known as exuding or exudation. ''Exudate'' is derived from ''exude'' 'to ooze' from Latin language, Latin 'to (ooze out) sweat' (' 'out' and ' 'to sweat'). Medi ...

, or lack of aeration during expiration. Crackles can be heard in people or animals who have

pneumonia Pneumonia is an Inflammation, inflammatory condition of the lung primarily affecting the small air sacs known as Pulmonary alveolus, alveoli. Symptoms typically include some combination of Cough#Classification, productive or dry cough, ches ...

atelectasis Atelectasis is the partial collapse or closure of a lung resulting in reduced or absence in gas exchange. It is usually unilateral, affecting part or all of one lung. It is a condition where the Pulmonary alveolus, alveoli are deflated down to l ...

pulmonary fibrosis Pulmonary fibrosis is a condition in which the lungs become scarred over time. Symptoms include shortness of breath, a dry cough, feeling tired, weight loss, and nail clubbing. Complications may include pulmonary hypertension, respiratory ...

, acute

bronchitis Bronchitis is inflammation of the bronchi (large and medium-sized airways) in the lungs that causes coughing. Bronchitis usually begins as an infection in the nose, ears, throat, or sinuses. The infection then makes its way down to the bronchi. ...

bronchiectasis Bronchiectasis is a disease in which there is permanent enlargement of parts of the bronchi, airways of the lung. Symptoms typically include a chronic cough with sputum, mucus production. Other symptoms include shortness of breath, hemoptysis, co ...

acute respiratory distress syndrome Acute respiratory distress syndrome (ARDS) is a type of respiratory failure characterized by rapid onset of widespread inflammation in the lungs. Symptoms include shortness of breath (dyspnea), rapid breathing (tachypnea), and bluish skin co ...

(ARDS),

interstitial lung disease Interstitial lung disease (ILD), or diffuse parenchymal lung disease (DPLD), is a group of respiratory diseases affecting the interstitium (the tissue) and space around the alveoli (air sacs) of the lungs. It concerns alveolar epithelium, pulm ...

or post

thoracotomy A thoracotomy is a surgical procedure that involves cutting open the chest wall to gain access into the pleural cavity, It is mostly performed by specialist cardiothoracic surgeons, although emergency physicians or paramedics occasionally also ...

metastasis Metastasis is a pathogenic agent's spreading from an initial or primary site to a different or secondary site within the host's body; the term is typically used when referring to metastasis by a cancerous tumor. The newly pathological sites, ...

ablation Ablation ( – removal) is the removal or destruction of something from an object by vaporization, chipping, erosion, erosive processes, or by other means. Examples of ablative materials are described below, including spacecraft material for as ...

Pulmonary edema Pulmonary edema (British English: oedema), also known as pulmonary congestion, is excessive fluid accumulation in the tissue or air spaces (usually alveoli) of the lungs. This leads to impaired gas exchange, most often leading to shortness ...

secondary to left-sided

congestive heart failure Heart failure (HF), also known as congestive heart failure (CHF), is a syndrome caused by an impairment in the heart's ability to fill with and pump blood. Although symptoms vary based on which side of the heart is affected, HF typically pr ...

and

high altitude pulmonary edema High-altitude pulmonary edema (HAPE) is a life-threatening form of non-cardiogenic pulmonary edema that occurs in otherwise healthy people at altitudes typically above . HAPE is a severe presentation of altitude sickness. Cases have also been re ...

can also cause crackles.

Terminology

René Laennec René-Théophile-Hyacinthe Laennec (; 17 February 1781 – 13 August 1826) was a French physician and musician. His skill at carving his own wooden flutes led him to invent the stethoscope in 1816, while working at the Hôpital Necker. ...

adopted the existing word '' râles'' (which has been translated as "rattles", "groans" and otherwise) to describe the added breath sounds that are now referred to as "crackles". He described them using unusual daily examples, such as "whistling of little birds", "crackling of salt on a heated dish", "cooing of the woodpidgeon", etc., but he soon realized that he was unable to use the term in front of his patients because it conjured the association of ''le râle de la mort'', which translates to "the death rattle", the noise that people who are about to die make when they can no longer clear secretions. Therefore, at the bedside, he used the Latin word '' rhonchus'', which originally meant a " snore". That was not clearly understood by his translator, John Forbes, and the terminology became very confusing after the publication in the 1830s of Forbes's English translation of Laennec's ''De L'Auscultation Mediate''. The difficulty of translating ''râle'' itself had been remarked upon in a British review of Laennec's work in 1820. The terminology of ''rales'' and ''rhonchi'' in English remained variable until 1977, when a standardization was established by the

American Thoracic Society The American Thoracic Society (ATS) is a nonprofit organization focused on improving care for pulmonary diseases, critical illnesses and sleep-related breathing disorders. It was established in 1905 as the American Sanatorium Association, and ...

and

American College of Chest Physicians The American College of Chest Physicians (CHEST) is a medical association in the United States consisting of physicians and non-physician specialists in the field of chest medicine, which includes pulmonology, critical care medicine Intensiv ...

. As a result, the term ''râles'' was abandoned, and ''crackles'' became its recommended substitute. The term ''rales'' is still common in English-language medical literature, but cognizance of the ATS/CHEST guidelines calls for ''crackles''.

Sound

Crackles are caused by explosive opening of small airways and are discontinuous, nonmusical, and brief. Crackles are more common during the inspiratory than the expiratory phase of breathing, but they may be heard during the expiratory phase. * Crackles are often described as fine, medium, and coarse. They can also be characterized as to their timing: fine crackles are usually late-inspiratory, whereas coarse crackles are early inspiratory. ** Fine crackles are soft, high-pitched, and very brief. This sound can be simulated by rolling a strand of hair between one's fingers near the ears or by moistening one's thumb and index finger and separating them near the ears. Their presence usually indicates an interstitial process, such as

. The sounds from interstitial pulmonary fibrosis have been described as sounding like opening a

Velcro Velcro IP Holdings LLC, trading as Velcro Companies and commonly referred to as Velcro (pronounced ), is a British privately held company, founded by Swiss electrical engineer George de Mestral in the 1950s. It is the original manufacturer of ho ...

fastener. ** Coarse crackles are somewhat louder, lower in pitch, and last longer than fine crackles. Their presence usually indicates an airway disease, such as

. They can also be described as unilateral or bilateral, as well as dry or moist/wet.

Associated diagnoses

Crackles are often associated with inflammation or infection of the small bronchi, bronchioles, and alveoli. Crackles that do not clear after a cough may indicate

pulmonary edema Pulmonary edema (British English: oedema), also known as pulmonary congestion, is excessive fluid accumulation in the tissue or air spaces (usually alveoli) of the lungs. This leads to impaired gas exchange, most often leading to shortness ...

or fluid in the alveoli due to

heart failure Heart failure (HF), also known as congestive heart failure (CHF), is a syndrome caused by an impairment in the heart's ability to Cardiac cycle, fill with and pump blood. Although symptoms vary based on which side of the heart is affected, HF ...

, or

. Crackles that partially clear or change after coughing may indicate

Interobserver consistency

In 2016, the

European Respiratory Society The European Respiratory Society, or ERS, is a non-profit organization with offices in Lausanne, Brussels and Sheffield. It was founded in 1990 in the field of respiratory medicine. The organization was formed with the merger of the Societas Eur ...

reported on a study of various physicians listening to audiovisual recordings of auscultation findings and interobserver variation was analyzed. The study found that broad descriptions agreed better than detailed descriptions.

References

External links