When should continuous capnography be used to monitor ventilation in patients at risk for respiratory compromise, such as those undergoing sedation, general anesthesia, mechanical ventilation, or with COPD, asthma, obesity hypoventilation, or neurologic impairment?

When to Use Continuous Capnography for Ventilation Monitoring

Continuous capnography monitoring is essential and should be used in all patients with tracheal tubes, supraglottic airway devices, those undergoing general anesthesia, and whenever verbal contact is lost during sedation. 1

Mandatory Indications for Continuous Capnography

General Anesthesia and Airway Management

• All patients with tracheal tubes or supraglottic airways require uninterrupted capnography from induction through emergence until the airway device is removed 1
• During tracheal intubation: Waveform capnography is the gold standard for confirming correct tube placement with both high sensitivity and specificity 1
• Detecting esophageal intubation: A flat capnogram after intubation indicates esophageal placement until proven otherwise—this applies even during cardiac arrest, where an attenuated trace will still be present if the tube is correctly placed 1
• Monitoring must continue during all transfers and throughout the entire perioperative period 1

Procedural Sedation

The depth of sedation determines capnography requirements:

• Mandatory when verbal contact is lost: Once patients cannot respond verbally, capnography becomes essential 1, 2
• Recommended for lighter sedation levels: Even when patients can still respond, capnography aids in monitoring airway patency, respiratory rate, and breathing patterns 1, 2
• Continual monitoring required: The ASA 2018 guidelines specify "continually monitor ventilatory function with capnography unless precluded or invalidated by the nature of the patient, procedure, or equipment" 2

For uncooperative patients, institute capnography after moderate sedation has been achieved 2.

High-Risk Populations Requiring Capnography

Obesity and Obesity Hypoventilation Syndrome

• Patients with BMI ≥35 kg/m² undergoing general anesthesia should receive continuous capnography in the PACU 3
• Implementation in this population decreased PACU length of stay and provided earlier detection of respiratory depression compared to pulse oximetry alone 3
• Obesity profoundly affects respiratory mechanics by reducing functional residual capacity and altering chest wall compliance, making visual assessment unreliable 4

Patients Receiving Opioids

• Capnography detects opioid-induced respiratory depression earlier than pulse oximetry, particularly in patients receiving supplemental oxygen where desaturation may lag significantly 5
• Being evaluated for monitoring opioid-induced respiratory depression in PACU settings and for patients receiving opioids for primary analgesia 6

Mechanically Ventilated Patients

• Continuous waveform capnography is recommended to confirm and monitor correct endotracheal tube placement 7
• Suggested for guiding ventilator management and optimizing mechanical ventilation 7
• During transport of mechanically ventilated patients, continuous capnometry is recommended 7

Specific Respiratory Conditions

While the guidelines don't differentiate monitoring by underlying disease (COPD, asthma, neurologic impairment), these patients fall under the general indications when they:

• Receive general anesthesia or sedation
• Have an artificial airway
• Lose verbal responsiveness during sedation

Critical Advantages Over Pulse Oximetry Alone

Capnography detects ventilatory compromise earlier than pulse oximetry, particularly when supplemental oxygen is administered:

• In pediatric sedation, capnography detected respiratory depression with a median time advantage of 35 seconds over pulse oximetry 8
• Capnography identified all apnea episodes and 76.9% of hypopneic hypoventilation episodes that pulse oximetry missed 8
• During gastroenterological procedures, adding capnography to pulse oximetry reduced the incidence of hypoxemia, severe hypoxemia, and apnea 6
• The cost of adding capnography is offset by reduction in adverse events and hospital length of stay 6

Additional Monitoring Roles

Beyond detecting respiratory depression, capnography serves multiple critical functions:

• Detecting bronchospasm or other lung pathology 1
• Identifying CO₂ rebreathing 1
• Signaling metabolic alterations such as malignant hyperthermia 1
• Assessing CO₂ elimination and dead space ventilation in mechanically ventilated patients 7

Important Caveats

• Specialized expertise required for safe use and interpretation in very small babies (<1 kg) 1
• Clinicians must be trained in recognizing normal and abnormal capnogram patterns 1
• A designated individual other than the proceduralist should monitor the patient and be trained in recognizing apnea and airway obstruction 2
• Set device alarms appropriately to alert the care team to critical changes 2

Implementation in Practice

The combination of pulse oximetry and capnography represents the current ventilation monitoring system of choice 9. When implementing capnography protocols, adherence rates of 86% have been achieved in PACU settings 3, and PACU nurses can accurately and safely perform this monitoring 10.