Hypoxia may be caused by all the following factors except

Appeared in: NHM UP Staff Nurse-2021 Shift-1st

Explanation

Increased hemoglobin (polycythemia) is a physiological adaptation to chronic hypoxia, not a cause.
In response to long-term low oxygen levels, the body stimulates red blood cell production to enhance the oxygen-carrying capacity of the blood.
This is a compensatory mechanism, making it the exception in a list of causes.

Option A: Decreased hemoglobin reduces the blood's ability to carry oxygen, directly causing anemic hypoxia.
Option B: A respiratory problem impairs gas exchange in the lungs, leading to insufficient oxygenation of the blood, which is known as hypoxic hypoxia.
Option C: A decrease in blood supply to an area, or ischemia, prevents oxygenated blood from reaching the tissues, causing stagnant hypoxia.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Pathophysiology of Hypoxia as background academic context rather than a clinical decision trigger.
Understanding the different causes of hypoxia is critical for nurses to anticipate and implement the correct interventions. For example, anemic hypoxia may require a blood transfusion, while hypoxic hypoxia requires respiratory support.
Recognizing signs of chronic hypoxia, such as clubbing of the fingers and polycythemia (increased hemoglobin), helps in assessing the long-term status of patients with conditions like COPD.
What if? If a patient with a history of heavy smoking and chronic cough presents with high hemoglobin and hematocrit levels, the nurse should suspect chronic hypoxia from COPD. The increased hemoglobin is a compensatory response, not a sign of health, and indicates the body is struggling with long-term oxygen deprivation.

How to Approach the Question

First, identify the negative keyword 'except'. This means you are looking for the option that is NOT a cause of hypoxia.
Evaluate each option one by one. Ask yourself, 'Does this cause hypoxia?'
Recall that decreased hemoglobin, respiratory issues, and poor blood supply all limit oxygen delivery to tissues, thus causing hypoxia.
Consider the final option, 'Increased haemoglobin'. Think about its physiological role. It's a response to a problem, not the problem itself.
Conclude that increased hemoglobin is a compensatory mechanism for chronic hypoxia, making it the correct answer as the exception.

Concept Tested & Keywords

Concept Tested: Pathophysiology of Hypoxia
Stem keywords: Hypoxia, caused by
Lead-in keywords: except
Negative lead-in flag: The question asks for the factor that does NOT cause hypoxia.

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E6 Physiology Guyton 4SAE Part 2A p. 94-96

E6 Medicine Harrison 22e Part 1 p. 318-320

Practise the full NHM UP Staff Nurse-2021 Shift-1st

Attempt every question from this paper in a timed mock, then review the full solution for each one.