Introduction

The clinical examination of the lungs is part of almost any physical examination. Due to the close relationship with nearby structures such as the heart, great vessels, esophagus, and diaphragm, a careful examination of the lungs can provide clues towards a diagnosis.

The airway is derived from the embryonic foregut and is divided into the trachea, bronchi, bronchioles, and lungs. Although humans have two lungs they are not symmetrical: the right lung is bigger than the left. The right lung is composed of three lobes, and ten segments and the left lung consists of two lobes and nine segments. The segmental division of the lungs is based on their airway supply.[1][2][3]

The physical examination of the chest is composed of inspection, palpation, percussion, and auscultation. Although it is not unheard of clinicians skipping the first three steps of the chest auscultation important information can be derived from a complete lung examination.

Issues of Concern

Inspection

During the inspection, the examiner should pay attention to the pattern of breathing: thoracic breathing, thoracoabdominal breathing, costal markings, and use of accessory breathing muscles. The use of accessory breathing muscles (i.e., scalenes, sternocleidomastoid muscle, intercostal muscles) could point to excessive breathing effort caused by pathologies. The body habitus of the patient could provide information regarding chest compliance, especially in the case of severely obese patients were chest mobility, and compliance are reduced due to added weight from adipose tissue.

The position of the patient should also be noted, patients with extreme pulmonary dysfunction will often sit up-right, and in distress, they assume the tripod position (leaning forward, resting their hands on their knees).

Breathing through pursed lips, often seen in cases of emphysema.

Ability to speak: patients that are unable to speak or become short of breath during the interview are likely to have a worse pulmonary function or reserve. 

Skeletal chest abnormalities should also be noted during the inspection. The most common chest osseous abnormality is pectus excavatum where the sternum is depressed in to the chest cavity. Pectus carinatum is the exact opposite of pectus excavatum: in this anatomical abnormality, the sternum is protruding from the chest wall. Barrel chest could also be present which consists in increased anterior-posterior diameter of the chest wall and is a normal finding in children, but it is suggestive of hyperinflation with chronic obstructive pulmonary disease (COPD) in adults. Thoracic spine abnormalities such as kyphosis and scoliosis could also be noted during physical examination of the chest.

Palpation

Palpation should focus on detecting abnormalities like masses or bony crepitus. During palpation the examiner can evaluate tactile fremitus: the examiner will place both of his hands on the patient's back, medial to the shoulder blades, and ask the patient to say "ninety-nine." An increase in the tactile fremitus points towards an increased intraparenchymal density and a decreased fremitus hints towards a pleural process that separates the pleura from the parenchyma (pleural effusion, pneumothorax). Of note, the fremitus can also be auscultated and can be referred to as vocal fremitus.

Auscultation

Auscultation of the lungs should be systematic and follow a stepwise approach in which the examiner surveys all the lung zones. For practical purposes, the lung can be divided into apical, middle and basilar regions during auscultation. The description of abnormal breathing sounds should be tagged with the location in which it was heard.

The movement of air generates normal breath sounds through the large and small airways. Normal breath sounds have a frequency of approximately 100 Hz. The absence of breath sounds should prompt the health care provider to consider shallow breath, abnormal anatomy or pathologic entities such as airway obstruction, bulla, hyperinflation, pneumothorax, pleural effusion or thickening, and obesity.

Tubular breath sounds are high pitched, bronchial breath sounds, seen in the following conditions: consolidation, pleural effusion, pulmonary fibrosis, distal collapse, and mediastinal tumor over a large patent bronchus.

• Vesicular breath sounds/normal breath sounds: While Laënnec considered normal lung sounds to originate from the flow of air in and out of alveoli, later investigations of the origin of respiratory sounds have not shown lung “vesicles” to participate in sound generation. Therefore, vesicular breath sounds is a misnomer for normal breath sounds.

• Wheezes: High-pitched continuous sounds with a dominant frequency of 400 Hz or more. (ATS) Suggestive of asthma, COPD, airway obstruction, or mucus plug.

• Ronchi: Low-pitched continuous musical sounds with a dominant frequency of about 200 Hz or less (ATS).

• Crackles: A "popping" sound generated by the passage of air through the accumulated secretions within the large and medium-size airways, creating the bubbling sounds (brief, non-musical, “discontinuous” sounds). Seen in COPD, Pneumonia and Heart Failure.

• Pleural Rub: Occurs due to inflamed pleural surface rubbing each other during breathing. It is difficult to differentiate from fine crackles, but the sound is similar to rubbing your stethoscope against cotton.

• Stridor: A loud, high-pitched, musical sound produced by upper respiratory tract obstruction. It indicates an extrathoracic upper airway obstruction (supraglottic lesions like laryngomalacia, vocal cord lesion) when heard on inspiration. It occurs in expiration if associated with intrathoracic tracheobronchial lesions (tracheomalacia, bronchomalacia, and extrinsic compression). It occurs in both phases if a lesion is fixed, for example, stenosis.

Special Maneuvers

• Pectoriloquy - Ask the patient to whisper a word such as “one-two-three” or “ninety-nine” and listen with a stethoscope. Typically, words are heard faintly. In cases of consolidation, the whispered sounds will be heard clearly and distinctly.
• Egophony is elicited by asking the patient to say  "Ee," and it will sound like an "A." Suggestive of consolidation or pleural effusion. 

Clinical Significance

While an array of more elaborate and expensive technologies for the diagnosis of chest diseases has emerged over time, auscultation of the lung still provides valuable, immediate and low-cost information to the experienced clinician. Lung sounds can be divided primarily into continuous sounds "wheezes," and interrupted (discontinuous) sounds  "crackles." Wheezes are musical, and crackles are not. No lung sound is pathognomonic for any specific disease or anatomical site.[4][5]

A good mnemonic to aid in the memorization of the lung exam steps is PIPPA:

• Positioning of the patient
• Inspection
• Palpation
• Percussion
• Auscultation