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  1. #1
    Cortez is offline Junior Member
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    hyperventilating

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    A healthy, 37-year-old, recently divorced woman loses her job at the auto factory. She picks up her three young children from the factory day care center and gets into an automobile accident on the way home. Her 5-year-old son, who was not wearing a seat belt, sustains a severe head injury. The woman was not hurt in the accident, but is hyperventilating as she sits in the waiting room at the hospital. She complains of feeling faint and has blurred vision. Which of the following is decreased in this woman?

    A. Arterial oxygen content
    B. Arterial oxygen tension (PO2)
    C. Arterial pH
    D. Cerebral blood flow
    E. Cerebrovascular resistance

  2. #2
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    Asclepius1 is offline Ultimate Member 537 points
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    Re: hyperventilating

    Quote Originally Posted by Cortez
    A healthy, 37-year-old, recently divorced woman loses her job at the auto factory. She picks up her three young children from the factory day care center and gets into an automobile accident on the way home. Her 5-year-old son, who was not wearing a seat belt, sustains a severe head injury. The woman was not hurt in the accident, but is hyperventilating as she sits in the waiting room at the hospital. She complains of feeling faint and has blurred vision. Which of the following is decreased in this woman?

    A. Arterial oxygen content
    B. Arterial oxygen tension (PO2)
    C. Arterial pH
    D. Cerebral blood flow
    E. Cerebrovascular resistance
    A. is incorrect.

    Hyperventilation substantially increases the arterial oxygen saturation. Increased ventilation also leads to "wash out" of carbon dioxide in the blood. Therefore, uncompensated respiratory alkalosis (higher pH) may develop. This respiratory alkalosis can cause a "left shift" of the oxygen-hemoglobin dissociation curve resulting in a higher arterial oxygen saturation, a second compensatory mechanism.

  3. #3
    Asclepius1's Avatar
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    C. is incorrect because hyperventilation cause an increase in arterial pH, not decrease!

  4. #4
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    I think ans is E

  5. #5
    Cortez is offline Junior Member
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    The correct answer is D. The key symptom is hyperventilation. Hyperventilation results in hypocapnia, alkalosis, increased cerebrovascular resistance, and decreased cerebral blood flow. Carbon dioxide plays an important role in the control of cerebral blood flow. An increase in arterial PCO2 dilates blood vessels in the brain and a decrease in PCO2 causes vasoconstriction. The anxious, hyperventilating woman is "blowing off" carbon dioxide, which lowers her arterial PCO2. This decrease in PCO2 has caused the cerebrovascular resistance (choice E) to increase, thereby decreasing cerebral blood flow. The decrease in cerebral blood flow has caused the woman to feel faint and to have blurred vision. Other symptoms commonly associated with the hyperventilation of anxiety states are feelings of tightness in the chest and a sense of suffocation.

    Hyperventilation increases the arterial oxygen content (choice A) and PO2(choice B) in a normal person.

    A decrease in arterial PCO2 causes the arterial pH (choice C) to increase, i.e., the patient becomes alkalotic.

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