C02 detector readings may be inaccurate in which patient group?

C02 detector readings may be inaccurate in which patient group?

• A. Patients with COPD
• B. Patients with cardiac arrest
• C. Pediatric patients
• D. Renal failure

Answer: (B)

Capnography readings depend on delivering CO2 from tissue metabolism through the lungs to the detector, which requires adequate pulmonary blood flow. In cardiac arrest, cardiac output drops to near zero, so CO2 produced by the tissues isn’t carried to the lungs. That makes end-tidal CO2 readings unreliable or falsely low, even though ventilation might be occurring. During CPR, there can be some transient pulmonary perfusion, so readings may change, and a sudden rise in end-tidal CO2 can signal return of spontaneous circulation. Other groups can have factors that affect capnography—for example, COPD increases dead space and ventilation–perfusion mismatch, which can make end-tidal CO2 readings less representative of arterial CO2, but they aren’t as inherently unreliable as in complete circulatory failure. Pediatric and renal failure patients don’t inherently render capnography inaccurate in the same way cardiac arrest does.

Capnography readings depend on delivering CO2 from tissue metabolism through the lungs to the detector, which requires adequate pulmonary blood flow. In cardiac arrest, cardiac output drops to near zero, so CO2 produced by the tissues isn’t carried to the lungs. That makes end-tidal CO2 readings unreliable or falsely low, even though ventilation might be occurring. During CPR, there can be some transient pulmonary perfusion, so readings may change, and a sudden rise in end-tidal CO2 can signal return of spontaneous circulation.

Other groups can have factors that affect capnography—for example, COPD increases dead space and ventilation–perfusion mismatch, which can make end-tidal CO2 readings less representative of arterial CO2, but they aren’t as inherently unreliable as in complete circulatory failure. Pediatric and renal failure patients don’t inherently render capnography inaccurate in the same way cardiac arrest does.