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Board Questions

1. Which of the following will lead to an acutely increased EtCO2? 

a) accidental extubation
b) massive pulmonary embolism
c) cardipulmonary arrest
d) mucus plugging

2. Which of the following is the most accurate measure when taking a blood pressure measurement with a oscillometric device (i.e. DinaMAP? 

a) SBP
b) MAP
c) DBP
d) Pulse Pressure

3. Compared to blood pressures measured via cuff, a blood pressure from an arterial line is generally...? 

a) Higher than the cuff pressure
b) Lower than the cuff pressure
c) The same as the cuff pressure
d) Depends on the patient's blood pressure


ANSWERS & EXPLANATIONS

1. D. Mucus plugging can lead to an increased EtCO2 if it leads to decreased tidal volumes and thus decreased ventilation. All of the other choices (accidental extubation, massive pulmonary embolus, and cardipulmonary arrest) lead to decreased EtCO2 due to increased dead space ventilation (or lack of CO2 detection in the case of accidental extubation)

2. B. MAP (mean arterial pressure) is the most accurate value from oscillometric blood pressure measurements. The DBP is the least accurate. With this type of blood pressure measurement, as the cuff is released, increasing oscillations occur with the maximum occurring at MAP. An algorithm is then used to estimate the SBP and DBP. 

3. D. The correlation between a cuff pressure and an arterial line pressure depends on the patient's actual blood pressure. In general, MAP's should be nearly equivalent between the two measurements. However, cuff pressures tend to OVERestimate blood pressure in the setting of hypotension and UNDERestimate blood pressure in the setting of hypertension. In effect, cuff pressures tend to cluster closer towards "normal" and thus can be falsely reassuring. Hence, the arterial line measurement is generally considered the gold standard method of blood pressure measurement in the PICU.

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