Compared with mainstream (inline) capnography, a key disadvantage of sidestream capnography is:

• A It adds dead weight and bulk to the airway connection, risking disconnection
• B There is a transit delay of several seconds due to gas aspiration through the sampling tube ✓
• C It cannot measure carbon dioxide during low-flow anaesthesia
• D Its sensor must be heated to prevent water condensation on the windows

Explanation

Sidestream analysers aspirate gas continuously through a sampling line into a distant analyser, producing a transit delay of several seconds between the event and its display, and small leaks or dilution with fresh gas can distort the waveform. Mainstream sensors sit directly on the airway with negligible delay, but they add weight and heat at the connection and need heated windows to prevent condensation. Both types work during low-flow anaesthesia.

Reference: Morgan and Mikhail's Clinical Anesthesiology, 7th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.