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Nicholas Wanstall Group

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Mark Komarov
Mark Komarov

Crackles Lung Sounds Causes

Auscultation is the term for listening to the internal sounds of the body, usually using a stethoscope. Auscultation is performed for the purposes of examining the circulatory system and respiratory system (heart sounds and breath sounds), as well as the gastrointestinal system (bowel sounds). It is an integral part of physical examination of a patient and is routinely used to provide strong evidence in including or excluding different pathological conditions that are manifested clinically in the patient.

Crackles Lung Sounds Causes

The stethoscope comprises a bell and a diaphragm. The bell is most effective at transmitting lower frequency sounds, while the diaphragm is most effective at transmitting higher frequency sounds[1]. In other words, the bell is designed to hear low pitched sounds and the diaphragm is designed to hear high pitched sounds. They are connected via rubber tubing to the ear pieces. These should be worn facing forward as the ear canals run anteriorly.

Vesicular - are usually quiet, mostly inspiratory, with a distinctive pause before a quieter expiratory phase. They are soft and low pitched with a rustling quality during inspiration and are even softer during expiration. These are the most commonly auscultated breath sounds, normally heard over the most of the lung surface. They have an inspiration/expiratory ratio of 3 to 1 or I:E of 3:1.

These are heard over the 1st and 2nd intercostal spaces and the interscapular area. The inspiratory and expiratory phases are roughly equal in length. They reflect a mixture of the pitch of the bronchial breath sounds heard near the trachea and the alveoli with the vesicular sound.

Wheezes are an expiratory sound caused by forced airflow through collapsed airways. Due to the collapsed or abnormally narrow airway, the velocity of air in the lungs is elevated[9]. Wheezes are continuous high pitched hissing sounds. They are heard more frequently on expiration than on inspiration. If they are monophonic it us due to an obstruction in one airway only but if they are polyphonic than the cause is a more general obstruction of airways[10]. Where the wheeze occurs in the respiratory cycle depends on the obstructions location[11], if wheezing occurs in the expiratory phase of respiration it is usually connected to broncholiar disease[12]. If the wheezing is in the inspiratory phase, it is an indicator of stiff stenosis whose causes range from tumours to scarring. One of the main causes of wheezing is asthma[12] other causes could be pulmonary edema, interstitial lung disease and chronic bronchitis.

Rhonchi are caused by obstruction or secretions in the bronchial airways. They are coarse, continuous low pitched rattlings sounds that are heard on inspiration and expiration that sound very much like snoring. They can be heard in patients with pneumonia, bronchiectasis, chronic obstructive pulmonary disease (COPD), chronic bronchitis or cystic fibrosis.

Pleural Rub produces a creaking or brushing sound. These occur when the pleural surfaces are inflamed and as a result rub against one another. They are heard during both inspiratory and expiratory phases of the lung cycle and can be both continuous and discontinuous. Pleural rub can suggest pleurisy, pneumothorax or pleural effusion.

The four pericardial areas relate to the heart sounds and can detect various abnormalities in the heart such as the valve stenosis or incompetence which are diagnostic for many diseases in the cardiovascular system. However, there are specific manoeuvres done for further investigation, and some of these would include[13]

Blood flowing across the heart valves is laminar flow so that no sound is produced. The sounds heard on auscultation are the sound of the valve cusps snapping shut at the end of diastole (when the AV valves shut producing the 1st heart sound) and at the end of systole (when the Aortic Pulmonary valves shut producing the 2nd heart sound).

These sounds are conducted to the surface of the body and can be heard with the aid of a stethoscope. There are specific places on the anterior chest wall where the sound from each of the 4 valves can best be heard. These are not the surface markings of the valves but rather the points where the sounds are best conducted to. They are as follows:

These consist of two sharp sounds, S1 and S2, which differentiate systole from diastole and no other significant sounds will be heard. A systole occurs when the ventricles fill with blood and the heart contracts. The sudden closure of the tricuspid valves and AV valves is caused by a decrease in pressure in the atria and a sharp increase in the intraventricular pressure which exceeds the pressure of the atria. This is the S1 sound. The ventricles continue to contract throughout systole forcing blood through the aortic and pulmonary semilunar valves. S2 is formed at the end of systole when the ventricles begin to relax and the pressure in the aorta and pulmonary artery begin to exceed the intraventricular pressure. When this happens there is a slight back-flow of blood into the heart which causes the semilunar valves to snap shut, producing S2. These two sounds are to be considered single and instantaneous, indicating a normal healthy heart.

This is a systolic murmur that indicates a physiological defect. The word stenosis refers to the abnormal turbulent flow of blood due to a narrow damaged blood vessel. Stenosis in the aorta results in this murmuring sound which occurs between S1 and S2. In addition to this other sounds may be heard such as S4 which results from the heavy work required by the left ventricle to pump the blood though the stenotic valve. Also because S2 is caused by the sudden closing of the aortic valve, a weaken poorly functioning stenotic valve may cause S2 to be very discreet or even inaudible. This murmur is usually best heard over the aortic is important to note that this is a sharp murmur with notable start and finishing points within a systole. We can usually tell how serious the stenosis is by listening to the timing of the murmur. An early peaking murmur is usually a less serious case of stenosis, while a late peaking murmur indicates more serious stenosis, because the stenotic valve is quite weak and the ventricle takes a lot more time to build the strength to pump the blood out of the heart.

These low-pitched wheezing sounds sound like snoring and usually happen when you breathe out. They can be a sign that your bronchial tubes (the tubes that connect your trachea to your lungs) are thickening because of mucus.

These crunching sounds can sometimes mean you have a collapsed lung, especially if you also have chest pain and shortness of breath. They also can be a sign of lung disease like COPD, pneumonia, or cystic fibrosis.

Your doctor can get important information about the health of your lungs by listening closely as you breathe. The easiest and most common way to do this is to hold a stethoscope to the skin on your back and chest. This is called auscultation.

The pulmonary exam includes multiple components, including inspection, palpation, percussion, and auscultation. In this article, we will focus on auscultation of lung sounds, which are useful in predicting chest pathology when considered alongside the clinical context. The lungs produce three categories of sounds that clinicians appreciate during auscultation: breath sounds, adventitious sounds, and vocal resonance.

For the purpose of this article, we refer to breath sounds as the normal lung sounds heard through the chest wall with the use of a stethoscope, rather than audible breathing through the mouth. Normal breath sounds are classified as bronchial, vesicular, or bronchovesicular, which have different acoustic properties based on anatomical characteristics of the location where you are auscultating. Bronchial sounds (also called tubular sounds) normally arise from the tracheobronchial tree and vesicular sounds normally arise from the finer lung parenchyma. Loud, harsh, and high pitched bronchial sounds are typically heard over the trachea or at the right apex. They are predominantly heard during expiration. If heard in other areas of the lung, bronchial sounds are abnormal. In contrast, vesicular breath sounds are soft, low pitched, predominantly inspiratory, and appreciated especially well at the posterior lung bases. Bronchovesicular sounds can be heard during inspiration and expiration and have a mid-range pitch and intensity. They are commonly heard over the upper third of the anterior chest. Note that the terms high and low pitch are defined by the American Thoracic Society Committee as 400hz or greater and 200hz or less, respectively, although the actual frequencies of these sounds may violate that official rule.[1][2]

Adventitious sounds refer to sounds that are heard in addition to the expected breath sounds mentioned above. The most commonly heard adventitious sounds include crackles, rhonchi, and wheezes. Stridor and rubs will also be discussed here. There are many other terms that are used to describe adventitious sounds, which are too numerous to cover. These terms are generally redundant with, or sub-categories of, the ones noted below. For instance, crackles and rales refer to the same finding; many terms are used interchangeably and vary by the clinician and geographic location of the practice.

The first trait that assists in the classification of adventitious sounds is whether the sounds are continuous or intermittent. For example, rhonchi and wheezes are continuous sounds whereas crackles are not. Crackles could be counted by the examiner as discrete acoustic events [250ms, constant, like the whirring of a fan]. The next thing to note is the pitch: wheezes and fine crackles are high pitched, whereas rhonchi and coarse crackles are low pitched.

Crackles are generated by small airways snapping open on inspiration.[2] Therefore, they are predominantly inspiratory. The difference between the course and fine crackles is believed to come from the size of the airway snapping open (larger airways, deeper pitched, courser crackles). Some have compared to separating hook-and-loop fasteners (e.g., velcro). 041b061a72


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