Capnography Explained: 5 Waveforms Every Anaesthesia Resident Should Know

A flat capnography trace after intubation. A shark-fin waveform. A baseline that never returns to zero. What do they mean—and what should you check next? In this Anaesthesia360 explainer, learn five essential capnography waveforms through physiology, clinical reasoning and practical bedside assessment: • Normal capnogram • Shark-fin pattern • Raised inspiratory baseline • Curare cleft • Abrupt waveform loss We also cover ETCO2 versus PaCO2, pulmonary perfusion, rebreathing, intubation confirmation, capnography during CPR, and a concise postgraduate viva answer. Designed for anaesthesia residents, medical students, trainees and practising clinicians. CHAPTERS 00:00 Flat trace after intubation: what next? 00:36 The CO2 journey: metabolism, perfusion and ventilation 01:12 Waveform 1: the normal capnogram 01:48 ETCO2 versus PaCO2 02:07 Waveform 2: the shark-fin pattern 03:25 Waveform 3: a raised baseline 04:23 Waveform 4: the curare cleft 05:19 Waveform 5: abrupt waveform loss 05:59 Intubation confirmation and PUMA criteria 06:41 Low ETCO2 and pulmonary perfusion 07:01 Capnography during CPR 07:22 Prevention and equipment checks 07:42 A systematic approach to every trace 08:03 30-Second Viva Answer 08:34 Anaesthesia360 Clinical Pearls 08:54 Final summary algorithm Educational content for healthcare professionals. Apply clinical judgement, patient-specific assessment and local protocols. Illustrative waveforms are not patient recordings. For more evidence-based anaesthesia concepts made simple, subscribe to Anaesthesia360. #Capnography #Anaesthesia #Anaesthesia360 References: 1. Chrimes N, Higgs A, Hagberg CA, et al. Preventing unrecognised oesophageal intubation: a consensus guideline from PUMA and international airway societies. Anaesthesia. 2022;77:1395–1415. Full guideline. 2. Royal College of Anaesthetists. Sustained Exhaled CO₂. 3. American Heart Association. Adult Advanced Life Support: 2025 Guidelines. 4. Thilen SR, Weigel WA, Todd MM, et al. 2023 ASA Practice Guidelines for Monitoring and Antagonism of Neuromuscular Blockade. Anesthesiology. 2023;138:13–41. Guideline. 5. Perkins H, Chatterjee D. Capnography — OpenAnesthesia. Updated March 10, 2026. 6. Kodali BS. Curare cleft. Further reading: Snyder A, Binda D, Germany JL, et al. Capnography: Video in Clinical Anesthesia. Anesthesia & Analgesia. 2023;137:943–946. Article.