WEEK 7The thoracic cage consists of the sternum, 12 pairs of ribs, 12 thoracic vertebrae, and the diaphragm, which forms the floor.On the anterior thorax, surface landmarks include: The suprasternal notch; The sternum (or breastbone), which has a manubrium, body, and xiphoid process; The sternal angle (or angle of Louis), which is continuous with the second rib; And the costal angle, where the right and left costal margins meet at the xiphoid process.On the posterior thorax, surface landmarks include: The vertebra prominens; The spinous processes; The inferior border of the scapula, usually at the seventh or eighth rib; And the twelfth rib.Use reference lines to pinpoint a finding on the chest. On the anterior chest, use the midsternal and midclavicular lines. On the posterior chest, use the vertebral and scapular lines. And on the lateral chest, use the anterior axillary, posterior axillary, and midaxillary lines.Anteriorly, the apex (or highest point) of the lungs lies 3 or 4 cm above the inner third of the clavicles. The base (or lower border) rests on the diaphragm at about the fifth intercostal space in the right midclavicular line and at the sixth rib in the left midclavicular line. Laterally, the lungs extend from the apex of the axilla to the seventh or eighth rib. Posteriorly, C7 marks the apex, and T10 usually corresponds to the base. On deep inspiration, the base descends to T12.Although the right lung is shorter than the left lung, it has three lobes while the left lung has two. The lobes are stacked in diagonal sloping segments and are separated by fissures that run obliquely. The pleurae form an envelope between the lungs and the chest. The pleural cavity is a potential space that contains a few millilitres of lubricating fluid. The cavity normally has a vacuum (or negative pressure) that holds the lungs tightly against the chest. The lubricating fluid prevents friction as the lungs move during respiration.The trachea lies anterior to the esophagus. It bifurcates just below the sternal angle anteriorly, and at the level of T4 or T5 posteriorly. The right bronchus is shorter, wider, and more vertical than the left. The bronchial tree protects the alveoli from small particulate matter by using mucus and cilia, which sweep particles upward for swallowing or expulsion. The functional unit of the respiratory tract is the acinus.The respiratory system has four major functions: First, it supplies oxygen to the body for energy production. Second, it removes carbon dioxide as a waste product of energy reactions. Third, it maintains homeostasis (or acid-base balance) in arterial blood. And fourth, it maintains heat exchange.The thorax and lungs undergo developmental changes. The respiratory system develops in utero, but does not function until birth. It continues to develop during childhood and reaches adult size by adolescence. During pregnancy, the growing uterus elevates the diaphragm 4 cm. This decrease in the vertical diameter of the thoracic cage is offset by an increase in the horizontal diameter. The fetus increases maternal oxygen demands, which are met by an increased tidal volume. In older adults, the costal cartilages become calcified. Respiratory muscle strength declines after age 50. Lung elasticity decreases, making the lungs less distensible and lessening their tendency to collapse and recoil. These changes lead to decreased vital capacity and increased residual volume. To obtain subjective data, ask questions that investigate these topics: Cough, Shortness of breath, Chest pain with breathing, History of respiratory infections, Smoking history, Environmental exposure, especially on the job, And self-care behaviours, such as pneumonia or influenza immunizations.To obtain objective data, inspect the posterior and anterior chest. Note the shape, configuration, and symmetry of the thoracic cage, including the anteroposterior ratio, placement of the scapulae, angle of the ribs, and development of the neck and trapezius muscles. Assess the quality of the respirations. Also observe the skin colour and condition and the patients position for breathing, facial expression, and level of consciousness.Also palpate the thorax and lungs, assessing the entire chest wall. Palpate the posterior and anterior chest to confirm symmetrical chest expansion, assess tactile (or vocal) fremitus, and detect any lumps, masses, or tenderness.To continue the examination, percuss the posterior and anterior chest. Percuss over the lung fields to determine the predominant note. Also percuss to map out the lower lung border and measure diaphragmatic excursion.Then auscultate the posterior and anterior chest. Systematically evaluate the presence and quality of normal breath sounds, including bronchial, bronchovesicular, and vesicular sounds. If you detect adventitious breath sounds or other abnormal findings, assess for bronchophony, whispered pectoriloquy, and egophony.If indicated, also measure forced expiratory time and assess arterial oxygen saturation with a pulse oximeter.Many provincial and territorial governments have smoke-free legislation. As part of the assessment, include health promotion. For example, discuss exposure to second-hand smoke (or environmental tobacco smoke), which increases the patients risk of adverse health effects.