On arrival at the intensive care unit, a critically ill patient suffers respiratory arrest and is placed on mechanical ventilation. The physician orders pulse oximetry to monitor the patient’s arterial oxygen saturation (SaO₂) noninvasively. Which vital sign abnormality may alter pulse oximetry values?
Tachycardia
Hypotension
Tachypnea
Fever
The Correct Answer is B
Choice A: Tachycardia
Tachycardia, defined as a heart rate exceeding 100 beats per minute, can affect the accuracy of pulse oximetry readings. When the heart beats too quickly, it may not fill with enough blood between beats, leading to reduced perfusion and oxygen delivery to tissues. However, while tachycardia can influence the readings, it is not the most significant factor compared to hypotension.
Choice B: Hypotension
Hypotension, or low blood pressure, significantly impacts pulse oximetry accuracy. When blood pressure is low, there is reduced perfusion to peripheral tissues, including the extremities where pulse oximeters are typically placed. This reduced perfusion can lead to inaccurate readings, as the device may not detect sufficient blood flow to measure oxygen saturation accurately. Hypotension is a critical factor that can alter pulse oximetry values, making it the most relevant choice.
Choice C: Tachypnea
Tachypnea, or rapid breathing, can affect oxygen levels in the blood but does not directly interfere with the pulse oximeter’s ability to measure oxygen saturation. While it indicates respiratory distress and can lead to hypoxemia, the pulse oximeter can still provide accurate readings unless accompanied by other factors like low perfusion.
Choice D: Fever
Fever can cause peripheral vasodilation, which might theoretically affect pulse oximetry readings by altering blood flow to the extremities. However, this effect is generally minimal compared to the impact of hypotension. Fever alone is unlikely to cause significant inaccuracies in pulse oximetry measurements.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is B
Explanation
Choice A reason: An increase in temperature is not a primary indicator of hypovolemic shock. While fever can occur due to infection or inflammation, it is not directly related to hypovolemic shock, which is primarily characterized by a significant loss of blood or fluids leading to decreased perfusion and oxygenation of tissues.
Choice B reason: A decrease in urinary output is a critical sign of hypovolemic shock. When the body loses a significant amount of blood or fluids, the kidneys receive less blood flow, leading to reduced urine production. This is a compensatory mechanism to conserve fluids and maintain blood pressure. Normal urine output is typically around 30 to 50 mL per hour, so a drop below this range is concerning.
Choice C reason: An increase in heart rate is a common response to hypovolemic shock as the body attempts to maintain cardiac output and blood pressure despite the loss of blood volume. Tachycardia (increased heart rate) is one of the early signs of shock, indicating that the heart is working harder to pump blood to vital organs.
Choice D reason: A decrease in respiratory rate is not typical of hypovolemic shock. In fact, hypovolemic shock often leads to an increased respiratory rate (tachypnea) as the body tries to compensate for decreased oxygen delivery to tissues. A decrease in respiratory rate could indicate other issues but is not a hallmark of hypovolemic shock.
Correct Answer is D
Explanation
Choice A Reason:
A decreased thyroxine (T4) level is not expected in a client with Graves’ disease. Graves’ disease is an autoimmune disorder that leads to hyperthyroidism, where the thyroid gland produces excessive amounts of thyroid hormones, including T4. Therefore, the T4 level is typically elevated, not decreased.
Choice B Reason:
Similarly, a decreased triiodothyronine (T3) level is not expected in Graves’ disease. Like T4, T3 levels are usually elevated due to the overactive thyroid gland. T3 is the active form of thyroid hormone and is often increased in hyperthyroid conditions.
Choice C Reason:
Decreased thyroid-stimulating immunoglobulins (TSI) percentage is incorrect. In Graves’ disease, TSI levels are elevated because these antibodies stimulate the thyroid gland to produce more thyroid hormones. TSI mimics the action of TSH, leading to increased production of T3 and T4.
Choice D Reason:
Decreased thyroid-stimulating hormone (TSH) level is the correct answer. In Graves’ disease, the excessive thyroid hormones (T3 and T4) exert negative feedback on the pituitary gland, leading to suppressed TSH production. Therefore, TSH levels are typically low in patients with Graves’ disease.
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