Porth's Essentials of Pathophysiology, 4e

538

Respiratory Function

U N I T 6

A. Determine the tidal volume and respiratory rate of the minute volume B. Participate in the cough reflex C. Contribute to the breathlessness that accompanies intensive exercise and the dyspnea that accompanies lung disease.

SUMMARY CONCEPTS (continued)

R E V I EW E X E R C I S E S 1. Relate the efficiency and work of breathing to changes in the tidal volume and respiratory rate observed in persons with: A. Decreased lung compliance in fibrotic lung disease B. Increased airway resistance in emphysema. 2. Use the solubility coefficient for oxygen and the oxygen-hemoglobin dissociation curve depicted in Figure 22-17 to answer the following questions: A. What is the hemoglobin saturation at a high altitude in which the barometric pressure is 500 mm Hg (consider oxygen to represent 21% of the total gases)? B. It is usually recommended that the hemoglobin saturation of persons with chronic lung disease be maintained at about 89% when they are receiving supplemental low-flow oxygen. What would their PO 2 be at this level of hemoglobin saturation, and what is the rationale for keeping the PO 2 at this level? C. Why are measures of hemoglobin saturation not necessarily a good measure of the oxygen- carrying capacity of blood? D. What is the oxygen content of a person with carbon monoxide poisoning who is receiving 100% oxygen at 3 atmospheres pressure in a hyperbaric chamber? Consider that most of the person’s hemoglobin is saturated with carbon dioxide. 3. Describe the receptor/s (peripheral and central), afferent pathways, central integration, and efferent neural pathways that: ■■ The cough reflex protects the lungs from the accumulation of secretions and from the entry of irritating and destructive substances; it is one of the primary defense mechanisms of the respiratory tract. ■■ Dyspnea is a subjective sensation of difficulty in breathing that is seen in cardiac, pulmonary, and neuromuscular disorders. It can present as air hunger brought about by inadequate ventilation, labored or difficulty breathing due to weakened respiratory muscles, or chest tightness that occurs with bronchoconstriction.

B I B L I O G R A P H Y

Burke NK, Lu-Yuan L. Mechanisms of dyspnea. Chest. 2010;135(5):1196–1201.

Canning BJ. Afferent nerves regulating the cough reflex: mechanisms and mediators of cough in disease. Otolaryngol Clin North Am. 2010;43(1):1–14. Chroneos ZC, Zvezdana S-C, Shepard VL. Pulmonary surfactant: an immunological perspective. Cell Physiol Biochem. 2010;25:13–26. Crapo RO. Pulmonary function testing. N Engl J Med. 1994;331:25–30. DeTroyer A, Kirkwood PA, Wilson TA. Respiratory action of inspiratory muscles. Physiol Rev. 2005;85:717–756. Hall JE. Guyton and Hall Textbook of Medical Physiology . 12th ed. Philadelphia, PA: Saunders Elsevier; 2011:465–523. Koeppen BM, Stanton BA. Berne and Levy Physiology . 6th ed. Philadelphia, PA: Mosby Elsevier; 2010:417–444. Lansing RW, Gracely RH, Banzett RD. The multiple dimensions of dyspnea: review and hypothesis. Respir Physiol Neurobiol. 2009;167(1):53–60. Moore KL, Dalley AF, Agur AMR. Clinically Oriented Anatomy . 6th ed. Philadelphia, PA: Wolters Kluwer Health/Lippincott Williams & Wilkins; 2009:107–127. O’Donnell DE, Banzett RB, Carrieri-Kohlman V, et al. Pathophysiology of dyspnea in chronic obstructive lung disease: a roundtable. Proc Am Thorac Soc. 2007;4(2):145–168. Prabhakar NR, Peng Y-J. Peripheral chemoreceptors in health and disease. J Applied Physiol. 2004;96:359–366. Rhoades RA, Bell DR. Medical Physiology: Principles of Clinical Medicine . 4th ed. Philadelphia, PA: Wolters Kluwer Health/ Lippincott Williams & Wilkins; 2013: 326–398. Ross MH, Pawlina W. Histology: A Text and Atlas . 6th ed. Philadelphia, PA: Wolters Kluwer Health/Lippincott Williams & Wilkins; 2011:664–684. West JB. Respiratory Physiology: The Essentials . 8th ed. Philadelphia, PA: Wolters Kluwer Health/Lippincott Williams & Wilkins; 2008.

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