American Board of Surgery Qualifying Exam (ABS QE) Practice Test

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Prepare for the ABS QE with flashcards and multiple-choice questions. Each question provides hints and explanations to enhance understanding. Start your journey to becoming a certified surgeon and tackle your exam with confidence!

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During the apnea test, an increase in CO2 of more than how many mmHg is considered positive?

  1. 10 mmHg

  2. 20 mmHg

  3. 30 mmHg

  4. 40 mmHg

The correct answer is: 20 mmHg

The apnea test is a critical component used to determine brain death, specifically assessing the body's response to increasing carbon dioxide levels. In this test, a positive result indicates significant hypoventilation and a lack of respiratory drive, signifying potential irreversible loss of brainstem function. An increase in carbon dioxide (CO2) of more than 20 mmHg during the apnea test is considered positive. This substantial increase demonstrates that the patient's body is unable to initiate a breath in response to elevated carbon dioxide levels, which should typically trigger a respiratory drive in a patient with intact brain function. If the CO2 rises beyond this threshold, it supports the diagnosis of brain death, as it suggests that the medulla oblongata, responsible for regulating breathing, is no longer functioning. Other values are not typically considered indicative of brain death in this context. An increase of 10 mmHg may not be sufficient to demonstrate a complete lack of respiratory response, while 30 mmHg and 40 mmHg represent further elevations that, while indicative of more severe hypoventilation, exceed the threshold necessary for a definitive positive result in the test. Thus, the 20 mmHg increase serves as a critical benchmark in this evaluation process.