Question

Capnography basically monitors

• A. Central venous pressure
• B. Blood pressure during anaesthesia
• C. Concentration of exhaled CO2
• D. Concentration of inhaled O2

Hint:

The name of the device is a clue: it graphs a gas you breathe out, not one you breathe in.

Answer 1

The Correct Option is C

Step 1: Understanding the Question:
The question asks what physiological parameter capnography is designed to measure during anaesthesia and critical care monitoring.

Step 2: Key Concept or Approach:
Capnography continuously records the carbon dioxide concentration in respiratory gases across the breathing cycle, displaying it as a waveform (capnogram) and a numerical end-tidal CO2 value. It reflects ventilation, circulation, and metabolism, and is used to confirm correct endotracheal tube placement and to detect airway or circuit problems early.

Step 3: Working Through the Options:
Central venous pressure is measured invasively through a central line and transducer, not by capnography. Blood pressure during anaesthesia is tracked with a cuff or an arterial line, again unrelated to capnography. Concentration of inhaled O2 is monitored by an oxygen analyser in the breathing circuit, not by a capnograph. Concentration of exhaled CO2 is exactly what a capnograph samples and displays breath by breath, making it the parameter capnography basically monitors.

Step 4: Conclusion:
The correct answer is concentration of exhaled CO2.