Secretary: Joy Woodward P O Box 53219, Kenilworth 7745, South Africa. Editorial Team: Mick Dower with Coen Calitz, Johan Schoombee and John Winter (The views expressed in this publication do not necessarily reflect the views of the Cape Cliivia Club) The year end meeting was held at Kirstenbosch, followed by the traditional braai. Over a 100 members attended and enjoyed Johan Scho
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Bioe110s09midtermii_corrWrite your name and SID on the top of each page! If you need extra space, use the back of the sheet. No computers or electronic communications devices allowed. Two double-sided sheets of notes allowed. Please limit all responses to “short answer” questions to 1-2 sentences. 1. (35 pts) Consider a patient with the following physiologic values. Assume all measurements are taken at atmospheric pressure (760 mmHg) and at so-called “body temperature pressure saturated” (BTPS) conditions. Note that the vapor pressure of water at BTPS is 47 mmHg and that the mole fraction of oxygen in inhaled air is ~0.2. Pulmonary function tests: Forced expiratory volume after 1 sec (FEV1) = 2.0 L Partial pressure of CO2 in expired air: 30 mmHg A. Calculate this patient’s inspiratory reserve volume (IRV). (5 pts) B. Calculate this patient’s alveolar ventilation rate (mL/min). (10 pts) C. Calculate the partial pressure of this patient’s alveolar oxygen (PAO2). Assume that the patient is producing carbon dioxide at 0.8 times the rate at which she is consuming oxygen (this value is R, the respiratory exchange ratio). (10 pts) D. Suppose this patient develops an acute case of asthma. What would you expect to happen to her FEV1 and why? (5 pts) E. Suppose instead the patient develops chronic obstructive pulmonary disease (COPD), and you notice she has begun to expire slowly and with pursed lips. Why is she doing this? (5 pts) 2. (20 pts) Consider a patient in an intensive care unit who is placed on positive-pressure ventilation. A. Consider an alveolus of radius 50 µm in this patient’s right lung. If the surface tension in the alveolar membrane is 30 mN/m, calculate how much pressure would be needed to keep the alveolus patent (open). (5 pts) B. Suppose that the patient undergoes a ventilation-perfusion scan (V/Q scan) both prior to and after being placed on the ventilator. These studies reveal that the ventilator has now created an increase in the V/Q ratio at the apices (“tops”) of the lungs. Explain this finding; a simple drawing of an alveolus and capillary may help. (5 pts) C. Suppose that the medical staff decide to significantly increase the positive pressure used during ventilation. Shortly after making this change, they notice the chest wall suddenly expands, the heart rate increases, and the arterial oxygen (PaO2) begins to drop. Upon listening to the patient’s chest with a stethoscope, they find that they can no longer hear any breath sounds on the right side. A chest x-ray reveals a collapsed right lung with no other abnormalities. Explain what likely happened and provide a specific diagnosis, i.e., a name of a medical condition (5 pts) D. Suppose that the patient manages to recover from all of this and is transferred to the inpatient floor, where he seems to be improving but remains largely confined to his bed. Soon, he develops a mysterious red, painful swelling on his left leg. Two days after that, he suddenly complains of severe chest pain and begins rapidly gasping for air. After listening to his chest and ordering a CT scan, the medical staff place him on anticoagulants (blood thinners) and oxygen, which eventually resolves both the leg swelling and the shortness of breath. Explain what likely happened and provide a specific diagnosis, i.e., the name of a medical condition [there is more than one possible correct answer] (5 pts). 3. (20 pts) Consider a healthy 21-year old female with the following arterial blood gas values: PaO2 = 100 mmHg PACO2 = 45 mmHg A. If this young woman is breathing room air at atmospheric pressure and BTPS conditions and her ratio of CO2 eliminated to O2 consumed (R) is 0.8 (see question 1), estimate her alveolar-arterial (A-a) gradient. (10 pts) B. Suppose that 6 months later, she develops a severe case of viral pneumonia that leads to bilateral pulmonary edema. How would you expect her A-a gradient to change? Justify your answer using terms in the A-a gradient equation (5 pts). C. Suppose that as a consequence of her pneumonia, she develops acidemia (reduced blood pH). Sketch her hemoglobin oxygenation curve (% hemoglobin saturated by O2 vs pO2) before and after onset of the acidemia. (5 pts) 4. (35 pts) Consider a patient who receives an IV infusion of inulin and para-aminohippuric acid (PAH), and then 24 hours later is subject to urine and blood collection. Suppose those tests reveal the following values: Urinalysis Urine output over 24-hour period: 1500 ml Urine concentration of PAH: 75 mg/dL Urine concentration of inulin: 400 mg/dL Urine concentration of K+: 45 mEq/L Urine concentration of Na+: 25 mEq/L Urine osmolarity: 800 mOsm/L Blood work Plasma concentration of inulin: 10 mg/dL Plasma concentration of PAH: 0.5 mg/dL Plasma concentration of K+: 4.0 mEq/L Plasma concentration of Na+: 140 mEq/L Plasma concentration of BUN: 17 mg/dL Plasma concentration of Glucose: 90 mg/dL Hematocrit: 0.45 A. Calculate the clearance ratio of Na+. How would you expect this value to change in someone who begins to take furosemide (lasix) and why? (1-2 sentences) (10 pts) B. Determine the filtered load of Na+ (in mEq/hr), the rate of elimination of Na+ through the urine (mEq/hr), and the % of Na+ that is reabsorbed. (10 pts) C. Calculate the osmolarity of this patient’s blood (mOsm/L) and determine the clearance of free water (mL/min). (10 pts) D. If this patient later developed a tumor that secreted renin, how would you expect his plasma Na+ concentration to change and why? (1-2 sentences) (5 pts) 5. (20 pts.) Consider the problem of filtration of solutes in the renal corpuscle (glomerular capillaries and Bowman’s space). A. Suppose you are working at a pharmaceutical company and develop a drug that selectively constricts efferent arterioles while dilating afferent arterioles. How would this drug be expected to affect the glomerular filtration rate (GFR) and why? (5 pts) B. If the plasma concentration of creatinine is 1.0 mg/dl, the urinary concentration of creatinine is 150 mg/dl, and the urinary output is 1 L/day (0.7 ml/min), calculate the GFR in ml/min. (5 pts) C. If the renal plasma flow is 500 ml/min and the hematocrit is 0.45, calculate the filtration fraction and renal blood flow in ml/min (10 pts). 6. Consider potassium and water balance (20 pts). A. Consider a 15 year old boy with type I diabetes who requires daily injections of insulin. One day, he accidentally injects himself twice instead of once. Thinking about his plasma insulin levels, what would you expect to happen to his serum potassium and why? (5 pts) B. Which of these three diuretics is least likely to cause hypokalemia and why: hydrochlorothiazide (HCTZ), furosemide (Lasix), or spironolactone? (5 pts) C. Consider an otherwise healthy patient who presents with acute dehydration after running a marathon. Would you expect her urine osmolarity to be higher or lower than before she ran the marathon, and why? (5 pts) D. Would you expect the free water clearance of the woman in C to be positive, negative, or zero after running the marathon, and why? (5 pts)
August 2011 Allergy and Medical Information All new students are required to submit a Physician's Report form. For returning students, parents are required to inform the school if there is a change in the medical status. Both new and returning students are required to complete the attached form. So that staff members can identify students who might require immediate intervention on sit