The general principles of inspection, palpation, percussion, and auscultation apply to the examination of the respiratory system. However, the physical examination should be directed not only toward ascertaining abnormalities of the lungs and thorax but also toward recognizing other findings that may reflect underlying lung disease.
On inspection, the rate and pattern of breathing as well as the depth and symmetry of lung expansion are observed. Breathing that is unusually rapid, labored, or associated with the use of accessory muscles of respiration generally indicates either augmented respiratory demands or an increased work of breathing. Asymmetric expansion of the chest is usually due to an asymmetric process affecting the lungs, such as endobronchial obstruction of a large airway, unilateral parenchymal or pleural disease, or unilateral phrenic nerve paralysis. Visible abnormalities of the thoracic cage include kyphoscoliosis and ankylosing spondylitis, either of which can alter compliance of the thorax, increase the work of breathing, and cause dyspnea.
On palpation, the symmetry of lung expansion can be assessed, generally confirming the findings observed by inspection. Vibration produced by spoken sounds is transmitted to the chest wall and is assessed by the presence or absence and symmetry of tactile fremitus. Transmission of vibration is decreased or absent if pleural liquid is interposed between the lung and the chest wall or if an endobronchial obstruction alters sound transmission. In contrast, transmitted vibration may increase over an area of underlying pulmonary consolidation. Palpation may also reveal focal tenderness, as seen with costochondritis or rib fracture.
The relative resonance or dullness of the tissue underlying the chest wall is assessed by percussion. The normal sound of underlying air-containing lung is resonant. In contrast, consolidated lung or a pleural effusion sounds dull, while emphysema or air in the pleural space results in a hyperresonant percussion note.
On auscultation of the lungs, the examiner listens for both the quality and intensity of the breath sounds and for the presence of extra, or adventitious, sounds. Normal breath sounds heard through the stethoscope at the periphery of the lung are described as vesicular breath sounds, in which inspiration is louder and longer than expiration. If sound transmission is impaired by endobronchial obstruction or by air or liquid in the pleural space, breath sounds are diminished in intensity or absent. When sound transmission is improved through consolidated lung, the resulting bronchial breath sounds have a more tubular quality and a more pronounced expiratory phase. Sound transmission can also be assessed by listening to spoken or whispered sounds; when these are transmitted through consolidated lung, bronchophony and whispered pectoriloquy, respectively, are present. The sound of a spoken E becomes more like an A, although with a nasal or bleating quality, a finding that is termed egophony.
The primary adventitious (abnormal) sounds that can be heard include crackles (rales), wheezes, and rhonchi. Crackles are the discontinuous, typically inspiratory sound created when alveoli and small airways open and close with respiration. They are often associated with interstitial lung disease, microatelectasis, or filling of alveoli by liquid. Wheezes, which are generally more prominent during expiration than inspiration, reflect the oscillation of airway walls that occurs when there is airflow limitation, as may be produced by bronchospasm, airway edema or collapse, or intraluminal obstruction by neoplasm or secretions. Rhonchi is the term applied to the sounds created when there is free liquid or mucus in the airway lumen; the viscous interaction between the free liquid and the moving air creates a low-pitched vibratory sound. Other adventitious sounds include pleural friction rubs and stridor. The gritty sound of a pleural friction rub indicates inflamed pleural surfaces rubbing against each other, often during both inspiratory and expiratory phases of the respiratory cycle. Stridor, which occurs primarily during inspiration, represents flow through a narrowed upper airway, as occurs in an infant with croup.
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