A 46-year-old man with kyphoscoliosis comes to the office due to fatigue and progressive shortness of breath over the last year. He has no other medical problems and does not use tobacco.
On examination, the angle of scoliosis is 67 degrees, and kyphosis deformity is above the level of T10.
Which of the following is the main mechanism of respiratory compensation in this patient?

Question

A 46-year-old man with kyphoscoliosis comes to the office due to fatigue and progressive shortness of breath over the last year.  He has no other medical problems and does not use tobacco.
On examination, the angle of scoliosis is 67 degrees, and kyphosis deformity is above the level of T10.
Which of the following is the main mechanism of respiratory compensation in this patient?

Quizplus · Accepted Answer

Abnormal curvature of the spine in both the anterior-posterior (kyphosis) and lateral (scoliosis) directions results in a stiffer rib cage (reduced chest wall compliance) (Choice C). Angles of scoliosis >65 degrees and kyphotic deformities above the level of T10 pose the greatest risk for impairment. Reduced expansion of the chest wall results in low tidal volume breathing, thereby decreasing alveolar ventilation (Choice A). To maintain normal minute ventilation, the respiratory rate increases, and this in turn increases the work of breathing. The structural abnormality of the chest wall also causes underventilation of some regions of the lung. This, in combination with reduced alveolar ventilation, results in micro-atelectasis and ventilation/perfusion mismatch (Choice B). Patients develop hypoxemia and hypercapnia, which worsen with age due to deteriorating chest wall compliance. A restrictive pattern is seen in kyphoscoliosis on pulmonary function testing. Children and young adults should be evaluated for possible surgical correction. Supportive treatment includes pulmonary rehabilitation and noninvasive positive pressure ventilation, particularly at night. This improves micro-atelectasis and reduces work of breathing and daytime respiratory muscle fatigue. (Choice E) Prolonged expiration is an adaptive mechanism seen in obstructive lung disease. Educational objective: Kyphoscoliosis causes a progressive decline in chest wall compliance, resulting in a restrictive defect. The respiratory rate increases to compensate for low tidal volume ventilation. Younger patients may undergo surgical correction. Supportive therapy includes pulmonary rehabilitation and noninvasive positive pressure ventilation. __________ References: Congenital kypho-scoliosis: a case of thoracic insufficiency syndrome and the limitations of treatment. (http://www.ncbi.nlm.nih.gov/pubmed/22048403) Restrictive chest wall disorders. (http://www.ncbi.nlm.nih.gov/pubmed/19452388) Respiratory mechanics in kyphoscoliosis. (http://www.ncbi.nlm.nih.gov/pubmed/8472069)

A 46-Year-Old Man with Kyphoscoliosis Comes to the Office Due