Lung Sounds Made Easy
From the general practice nurse to the ICU nurse, lung sounds tell you a great deal about a patient and their relative health. However, knowing the difference between rales, a crackle, and a wheeze is sometimes still a confusing proposition for many nurses, especially new nurses.
Part of the reason for that is that some of the language is interchangeable. For instance, crackles actually are rales, and the large amount of words can leave anyone’s head spinning. Knowing what to call what you hear on the other end of the stethoscope can tell you – and the doctor – quite a bit about a patient’s condition.
What was once called rhonchi are now called a sonorous wheeze, and this is because they have a snoring, gurgling quality to them. Rhonchi are often a low-pitched moan that is more prominent on exhalation. It differs from wheezes in that wheezes are high and squeaky while these are low and dull. Rhonchi are caused by blockages to the main airways by mucous, lesions, or foreign bodies. Pneumonia, chronic bronchitis, and cystic fibrosis are patient populations that commonly present with rhonchi. Coughing can sometimes clear this breath sound and make it change to a different sound.
Crackles are the sounds you will hear in a lung field that has fluid in the small airways. As stated before, crackles and rales are the same thing, and this can often lead to confusion among health care providers. Crackles come in two flavours: fine and coarse. Fine crackles sound like salt heated on a frying pan or the sound of rolling your hair between your fingers next to your ear. Coarse crackles sound like pouring water out of a bottle or like ripping open Velcro. This lung sound is often a sign of adult respiratory distress syndrome, early congestive heart failure, asthma, and pulmonary oedema.
Wheezes and rhonchi are actually very closely related. They are so closely related that the terminology for them has changed, too. Wheezes are now known as sibilant wheezes to distinguish them from rhonchi. Sibilant wheezes are high-pitched and shrill sounding breath sounds that occur when the airway becomes narrowed. They often have a musical quality to them. These are the typical wheezes heard when listening to an asthmatic patient. Sibilant wheezes are caused by asthma, congestive heart failure, chronic bronchitis, and COPD (see ‘Understanding COPD and the Hypoxic Drive to Breathe‘).
Stridor is an unusual sound that not many adult patients will have, but it bears mentioning. It is a high-pitched, musical sound that is heard over the upper airway. It usually indicated a foreign body obstruction of the larger airways, such as the trachea or a main bronchus, and requires immediate attention. It is also the most common type of breath sound heard in children with croup, though it is important to differentiate between croup and a foreign body airway obstruction.
A pleural friction rub is caused by the inflammation of the visceral and parietal pleurae. These membranes are usually coated in a protective fluid, but when inflamed, they stick together and make a sound like leather creaking against itself. It often causes a great deal of pain, and the patient will splint their chest and resist breathing deeply to help mitigate the pain. A pericardial rub and a pleural rub will often sound similar, and the best way to distinguish between the two is to make the patient hold their breath. If you still hear the rubbing sound, then the patient has a pericardial rub and requires different treatment. Pleural effusion and pneumothorax are two diagnoses that can cause a pleural friction rub.