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# Indications, Hazards, and Potential Complications of Capnography The American Association for Respiratory Care (AARC) has identified broad categories of indications and potential complications of capnography. Other common indications include use during cardiopulmonary resuscitation for identifyi...

# Indications, Hazards, and Potential Complications of Capnography The American Association for Respiratory Care (AARC) has identified broad categories of indications and potential complications of capnography. Other common indications include use during cardiopulmonary resuscitation for identifying proper airway placement and assessing perfusion. A calibrated monitor and a patent sampling line are crucial for interpreting capnography readings. Estimated $P_{ET}CO_2$ levels can be used as a substitute for actual $PaCO_2$ measurements. ## Box 7-2: Indications, Hazards, and Potential Complications of Capnography ### Indications * Verification of artificial airway placement (ensuring tracheal rather than esophageal intubation). * Assessment of pulmonary circulation and respiratory status. * Improving the matching of the ventilation-perfusion ratio (V/Q). * Measuring carbon dioxide ($CO_2$) elimination to assess metabolic rate or alveolar ventilation. * Optimizing mechanical ventilation. * Improving the $V_T$/$V_D$ ratio. * Continuously monitoring the integrity of the ventilator circuit, including the artificial airway. ### Hazards and Potential Complications * Misinterpreting data, potentially leading to inappropriate treatment. * With mainstream analyzers, excessively large sampling windows can increase the circuit's mechanical dead space. * Sampling windows or lines can put additional weight on the circuit, possibly increasing traction on the airway, primarily in pediatric patients. * With sidestream analyzers, the sampling rate can trigger auto-triggering of mechanical ventilators. **Note:** A significant error can arise when performing assessments or making clinical decisions based on capnography. An arterial blood gas test is necessary to establish the baseline arterial-end tidal $CO_2$ (a-ET $P_{CO_2}$) gradient. Other errors include misinterpreting low or absent cardiac output as a disconnect or possible esophageal intubation, all of which can result in a $P_{CO_2}$ of zero.