Notching in ETCO2 Waveform: Causes and Clinical Significance

Malfunctioning unidirectional valves in circle breathing systems can lead to rebreathing and create irregular CO2 waveforms, which should be detected during the two-bag test performed before each case 1, 2
Inadequate fresh gas flow in certain breathing systems can lead to rebreathing and waveform abnormalities 3, 4

Critical Differential Diagnosis

Rapidly rising ETCO2 values that are resistant to increased minute ventilation strongly suggest malignant hyperthermia, especially with recent exposure to triggering agents 5, 6
Progressive increase in ETCO2 accompanied by tachycardia is the cardinal early feature of malignant hyperthermia, appearing before temperature elevation 6
Immediate discontinuation of volatile anesthetics and administration of dantrolene is required if malignant hyperthermia is suspected, as delayed treatment increases mortality 5, 6

Verify circuit integrity by performing visual inspection and checking all connections are secured with "push and twist" technique 1, 2
Assess ventilator function by confirming adequate pressure generation during inspiration and proper alarm configuration 1
Evaluate patient factors including auscultation for bronchospasm, checking neuromuscular blockade depth, and assessing for spontaneous breathing efforts 7
Check sampling line patency as obstruction or water accumulation can distort waveforms 8

Inspect the CO2 absorber for exhaustion or channeling, which can affect breathing system function 9, 1
Verify proper vaporizer function and ensure no tilting has occurred, as this can affect gas delivery and circuit dynamics 9, 2
Confirm correct breathing system configuration, particularly for Bain-type and circle co-axial systems where inner tube occlusion can cause problems 1

Continuous waveform capnography is the most reliable method for monitoring ventilation and detecting circuit problems during anesthesia 10, 7
During cardiac arrest or low cardiac output states, ETCO2 values may be falsely low despite correct tube placement due to decreased pulmonary blood flow 10

Assuming equipment is functioning properly without systematic checking leads to delayed recognition of circuit problems 1, 2
Failing to perform the two-bag test before each case misses opportunities to detect breathing system leaks or obstructions 1