Lung Assessment Distinguishing Normal from Abnormal Breath Sounds
Both inspection and auscultation are a part of respiratory assessment. As you inspect, look for signs of labored breathing, including the use of accessory muscles and nasal flaring. Also observe the anteroposterior (AP) and transverse chest diameters. Normally, the transverse diameter is roughly twice the AP diameter. A large AP diameter could be found in a person with chronic lung disease. A large AP diameter could be a normal finding in an elderly patient or in one who is a professional singer. Watch also to see if chest movements are symmetrical.
As you auscultate the lungs, try to discern normal breath sounds and abnormal, adventitious sounds. Remember that to attain any degree of skill you must practice frequently.
Auscultation should be done both anteriorly and posteriorly in a systematic manner, comparing one side with the other. The lower lobes are heard only in a very small area on the anterior chest; conversely. The upper lobes are heard only in a small area of the posterior chest.
Breath sounds are created by the movement of air in the trachea, bronchi, and alveoli. Normally, the expiratory phase is twice as long as the inspiratory phase. On auscultation, however, you do not hear all of the expiratory phase, so that it seems shorter than the inspiratory phase. In cases of bronchial obstruction, chronic lung disease, or shallow breathing, breath sounds may be absent or decreased. In a condition that causes consolidation of lung tissue, such as pneumonia, breath sounds may be louder or increased.
You may hear many abnormal sounds superimposed on the breath sounds. Among these are crackles, gurgles, wheezes, and friction rubs. In most facilities, current practice is to describe what you hear or to describe all abnormal sounds as “adventitious sounds.”
Crackles result from air passing through moisture in the respiratory passages. They are usually heard on inspiration. Crackles may be fine or coarse. Fine crackles have a high-pitched sound; coarse crackles are louder and tend to have a bubbling quality. If you hear crackles, ask the patient to cough and listen again. Typically, patients who have been lying quietly have some crackles in the bases that clear when they cough. You may occasionally hear crackles referred to as rales; this is an older term that is no longer recommended.
Gurgles are caused by air passing through respiratory passages that have narrowed or been partially obstructed by secretions, edema, tumors, and so on. Gurgles are usually low pitched and loud and often alter in quality after the patient coughs. They may be heard on both inspiration and expiration. Rhonchi is the older term for gurgles.
Like gurgles, wheezes are caused by air passing through partially obstructed respiratory passages, but they are higher-pitched because they originate in smaller passages. Wheezes have a whistle-like tone. Although they are more commonly heard during expiration, wheezes can be heard during any phase of respiration.
Pleural friction rubs are caused by the rubbing together of inflamed and roughened pleural surfaces. The sound is harsh and scratchy, somewhat like two pieces of sandpaper being rubbed together. Friction rubs are heard on both inspiration and expiration. If this sound correlates with the rate and rhythm of the heartbeat, not the respirations, it is a pericardial friction rub.