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Disorders of the thoracic cage and diaphragm 

Disorders of the thoracic cage and diaphragm

Chapter:
Disorders of the thoracic cage and diaphragm
Author(s):

John M. Shneerson

DOI:
10.1093/med/9780199204854.003.1818_update_001

May 30, 2013: This chapter has been re-evaluated and remains up-to-date. No changes have been necessary.

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date: 28 April 2017

Disorders of the thoracic skeleton—these can lead to a severe restrictive ventilatory defect, the risk of respiratory failure being highest with (1) scoliosis—particularly if the following characteristics are present: early onset, severe angulation, high in the thorax, respiratory muscle weakness, low vital capacity; (2) kyphosis—but only if of very sharp angulation (gibbus), most commonly seen following tuberculous osteomyelitis; and (3) after thoracoplasty—historically performed as treatment for pulmonary tuberculosis.

Diaphragmatic weakness—unilateral paralysis rarely causes symptoms unless there is coexisting lung disease or weakness of other respiratory muscles. Bilateral weakness usually presents as orthopnoea, which (by contrast to orthopnoea in cardiac failure) is relieved promptly by sitting up, and on examination the abdomen moves paradoxically inwards as the diaphragm ascends during inspiration. Vital capacity in the sitting position is about 50% of that predicted and may fall by a further 50% when supine. Diaphragmatic screening or ultrasound examination reveals paradoxical diaphragmatic movement during sniffing.

Respiratory failure—this occurs initially during sleep, when the respiratory drive is reduced and the work of breathing is increased, and then in wakefulness. Pulmonary hypertension and right heart failure often develop once the arterial Pco2 is elevated during the day. Arterial blood gases and quality of life can both be readily improved with noninvasive ventilation, usually using a nasal or face mask. Survival in most skeletal disorders after starting ventilation is around 80 to 90% at 1 year, 75% at 3 years and 50% at 5 to 10 years.

Other clinical features—some conditions of the thoracic cage, particularly pectus excavatum and the straight back syndrome, can cause cardiac problems due primarily to distortion of the heart and major vessels. Ankylosing spondylitis leads to apical bullae, pleural thickening/effusions, and cricoarytenoid arthritis, but rarely causes respiratory failure.

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