Chapter 27 A patient with chronic bronchitis is brought into the emergency room with complaints of sudden-onset chest pain, shortness of breath, and coughing up blood. His lab work shows hypoxemia, respiratory acidosis, and elevated red blood cell (RBC) count, white blood cell count, hemoglobin, and hematocrit. a.            Utilizing your understanding of the process of erythropoiesis, why do you think this patient has elevated RBCs, hemoglobin, and hematocrit? b.            What is the most likely cause of the patient’s acute symptoms? How do you explain this?

a. The patient’s elevated red blood cell count, hemoglobin, and hematocrit can be explained by the process of erythropoiesis. Erythropoiesis refers to the production of red blood cells in the bone marrow. In response to decreased oxygen levels in the blood, the kidney releases a hormone called erythropoietin. This hormone stimulates the bone marrow to produce more red blood cells.

In the case of chronic bronchitis, the patient experiences inflammation and narrowing of the airways, leading to reduced airflow and impaired gas exchange in the lungs. This results in chronic hypoxemia, a condition characterized by low oxygen levels in the blood. In an attempt to compensate for this chronic hypoxemia, the kidney releases an increased amount of erythropoietin, which stimulates the bone marrow to produce more red blood cells. This, in turn, leads to an elevated red blood cell count, hemoglobin, and hematocrit.

The elevated red blood cell count, hemoglobin, and hematocrit can be seen as the body’s adaptive response to chronic hypoxemia. By increasing the production of red blood cells, the body aims to improve oxygen-carrying capacity and ensure that an adequate supply of oxygen reaches various tissues and organs.

b. The most likely cause of the patient’s acute symptoms, including sudden-onset chest pain, shortness of breath, and coughing up blood, is a pulmonary embolism. A pulmonary embolism occurs when a blood clot, usually originating from the deep veins of the leg (deep vein thrombosis), travels through the bloodstream and becomes lodged in one of the arteries supplying the lungs.

In this case, the patient’s chronic bronchitis and associated airway inflammation may contribute to a prothrombotic state, increasing the risk of blood clot formation. The sudden onset of symptoms suggests that a clot has become dislodged and has obstructed one of the pulmonary arteries.

The obstruction of a pulmonary artery by a blood clot leads to a reduction in blood flow to a specific portion of the lung. This results in impaired gas exchange and a decreased supply of oxygen to the affected area, leading to hypoxemia. The decreased oxygen levels trigger a cascade of physiological responses, including vasoconstriction and release of inflammatory mediators, which can cause chest pain.

Additionally, the obstruction of a pulmonary artery can cause mechanical irritation, leading to local inflammation and coughing up blood (hemoptysis). The coughing up of blood occurs due to the rupture of small blood vessels within the lung tissue surrounding the blocked artery.

In summary, the patient’s acute symptoms are most likely due to a pulmonary embolism. This occurs when a blood clot obstructs one of the arteries supplying the lungs, leading to decreased blood flow, hypoxemia, chest pain, and coughing up blood. The chronic bronchitis and associated airway inflammation may contribute to a prothrombotic state, increasing the risk of blood clot formation.

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