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Anatomy and Physiology of Respiratory System

1. Explain how carbon monoxide interferes with oxygen transport. Be sure to include the binding of CO to hemoglobin. If the air is contaminated with 0.1% CO and CO binds with about 200 times more affinity than oxygen (21% O2 in normal air), then what will be the ratio of oxygen versus CO bound?

2. A 65 yo male patient goes to the emergency room complaining of shortness of breath (SOB) and dyspnea on exertion (for the past two years). He is thin with a large chest, smokes two packs of cigarettes/day and is in moderate respiratory distress. What is the problem you suspect (diagnosis and the etiology (cause, include the underlying mechanism and elastase effects))? What would you expect for the value of the Spirometry results (low, normal or high) for TLC, FRC, RV and for FVC and FEV?

3. A woman goes to the emergency room complaining of chest pain. A lung scan reveals an embolus in the lung. He respiratory rate is 24 breaths/minute (hyperventilation, due to panic). Her arterial blood PO2 is low (hypoxia) but her alveolar PO2 is high, Why? Her blood PCO2 is also lower and her blood pH is high. Why, explain?

4. A 43 y.o. woman goes to the Emergency room with acute onset of pain in her right upper quadrant (that radiates down the right shoulder). She reports that the pain is worse after she eats a fatty meal. Ultrasound shows an enlarged gall bladder with multiple gallstones. Explain how gallstones can block the flow of bile and what may cause the pain? Why would a fatty meal make the pain worse? What effect does CCK have on gastric emptying?

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Q: Explain how carbon monoxide interferes with oxygen transport. Be sure to include the binding of CO to hemoglobin. If the air is contaminated with 0.1% CO and CO binds with about 200 times more affinity than oxygen (21% O2 in normal air), then what will be the ratio of oxygen versus CO bound?

The affinity between carbon monoxide and hemoglobin is 230~260 times stronger than the affinity between hemoglobin and oxygen. CO binds to the hemoglobin, producing carboxyhemoglobin (COHb). The binding of carbon monoxide at one of the sites in Hb molecules, increases the oxygen affinity of the remaining three sites. Levels of oxygen available for tissue use are decreased as CO shifting the oxygen dissociation curve to the left, which keeps all the oxygen in the blood, none is being given to the tissues, and this causes tissue hypoxic injury. In addition, CO may diffuse to extravascular compartments,
binding with other molecules, e.g. myoglobin, although all to a lesser extent than Hb. Since air contains 21% oxygen this means that only 0.1% carbon monoxide in the air will eventually lead to 50% of the haemoglobin being combined to form carboxyhaemoglobin.

References:
What is the mechanism of carbon monoxide toxicity?Aviat Space Environ Med. 1975 Oct;46(10):1289-91. Goldbaum LR, Ramirez RG, Absalon KB.

Q: A 65 yo male patient goes to the emergency room complaining of shortness of breath (SOB) and dyspnea on exertion (for the past two years). He is thin with a large chest, smokes two packs of cigarettes/day and is in moderate respiratory ...

Solution Summary

This answer deals with 4 case scenarios involving patients with respiratory problems. It provides explanation of the symptoms, underlying pathology and diagnosis.

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