A Case Study on Human Respiratory Physiology

When Charles returned to his apartment at 5 PM in the
evening, he turned on his old kerosene-fueled space heater. It had been
a cold day in late spring and his third floor apartment was chilly.
After spending an hour fixing dinner, he ate while watching the evening
news on TV. He noticed that his vision became progressively blurred.
When he got up to go to the kitchen, he felt lightheaded and unsteady.
Entering the kitchen, he became very disoriented and passed out. The
next thing he remembered was waking up in the intensive care unit of the
hospital. Some friends who had stopped by about 7 PM
had found Charles unconscious on the kitchen floor. They had called an
ambulance, which had rushed Charles, still unconscious, to the hospital.

An arterial blood sample drawn when he first arrived at the hospital
showed the following values:





Questions

1. The blood gas measurements show abnormalities in the partial
   pressure(s) of what gas(es)?
   
   
   1. N₂, O₂ and CO
      
   2. CO and CO₂
      
   3. CO alone
      
   4. N₂ and CO
      
   5. O₂ and CO
      
   
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2. A measurement of Charles’ blood reveals that the O₂
   content is low (50% of normal) and hemoglobin is 50% saturated with CO
   (50% HbCO).
   
   The oxygen-hemoglobin saturation curve in Charles’ blood (50% HbCO)
   and under normal conditions (2% HbCO) is shown below. CO₂
   binding to hemoglobin is normal in both instances.
   
   
   
   What is the approximate % saturation of hemoglobin by O₂
   in normal arterial blood?
   
   
   
   1. 100%
      
   2. 97%
      
   3. 75%
      
   4. 50%
      
   5. 35%
      
   
   
3. What is the maximum amount of O₂ (ml/ 100 ml
   blood) that can be carried in Charles’ arterial blood?
   
   
   
   1. 2 ml/100 ml
      
   2. 5 ml/100 ml
      
   3. 10 ml/100 ml
      
   4. 15 ml/100 ml
      
   5. 20 ml/100 ml
      
   
   
4. CO enhances the Bohr effect. This means that CO will
   cause a more pronounced shift of the hemoglobin oxygen saturation curve
   to the:
   
   
   
   1. right
      
   2. left
      
   
   
5. If the partial pressure of O₂ in the body
   tissues is 20 mm Hg, what is the best estimate of the amount of O₂
   (ml/100ml) that can be released from Charles’ blood as it circulates in
   his systemic capillaries?
   
   
   
   1. <1 ml /100 ml
      
   2. 1 ml /100 ml
      
   3. 2.5 ml /100 ml
      
   4. 5 ml /100 ml
      
   5. 10 ml /100 ml
      
   
   
6. In Charles’ blood, the partial pressure of CO in the
   blood is far lower than the partial pressure of O₂, yet the
   percent saturation of hemoglobin by each gas is equal. This result
   indicates that the affinity of hemoglobin for CO is approximately how
   many times greater as compared to O₂?
   
   
   
   1. 38
      
   2. 100
      
   3. 238
      
   4. 708
      
   5. 1783
      
   
   
7. Would you expect Charles’ disorder to be accompanied by
   chemoreceptor-mediated hyperventilation?
   
   
   
   1. Yes, since the % oxygen saturation of hemoglobin in his
      blood is decreased
      
   2. Yes, since CO acts as a CNS neurotransmitter and central
      chemoreceptors are located in the brain
      
   3. Yes, since elevated partial pressure of CO is detected by
      peripheral chemoreceptors in carotid and aortic bodies
      
   4. No, since the partial pressure of O₂ in his
      blood is normal
      
   5. No, since CO is unable to diffuse across the blood-brain
      barrier
      
   
   
8. Fundamentally, Charles’ condition is a problem of:
   
   
   
   1. pulmonary ventilation
      
   2. diffusion across the respiratory membrane between the
      alveolar air space and the alveolar capillaries
      
   3. transport of gases between the alveolar capillaries and
      capillary beds in other tissues
      
   4. exchange of dissolved gases between the blood and the
      interstitial fluid in peripheral tissues
      
   5. absorption of oxygen and release of carbon dioxide by
      cells in the peripheral tissues
      
   
   
9. With regard to the physiology of external respiration,
   Charles’ disorder is most analogous to:
   
   
   
   1. barbiturate-induced hypoventilation
      
   2. altitude sickness
      
   3. emphysema
      
   4. acute hemorrhagic anemia
      
   
   
10. Which of the following is NOT an appropriate component
    of an aggressive treatment plan for Charles’ disorder?
    
    
    
    1. administration of a breathing gas mixture with a high
       percentage of oxygen
       
    2. alkalization of the blood (increase the pH)
       
    3. partial blood replacement with normal, compatible whole
       blood
       
    4. administration of a breathing gas mixture with elevated
       levels of carbon dioxide
       
    
    

thank u ....................................