Capnography During Anaesthesia Monitoring

Capnography during anaesthesia is not optional. It is a mandatory monitor for every patient under general anaesthesia, and for good reason. From the moment the airway is secured until the patient wakes, it is the fastest, clearest signal of whether ventilation is working.

It confirms the tube, tracks every breath, and is often the first sign of an emergency. This guide covers what it monitors, the crises it catches first, and what the standards require.

Key takeaways

• Capnography is a mandatory monitor for every patient under general anaesthesia.
• It confirms the airway and tracks ventilation continuously, from induction to recovery.
• It is often the first sign of an emergency, from a disconnection to malignant hyperthermia.
• FiCO₂ and a rising baseline warn of rebreathing, such as exhausted soda lime.
• Global standards now push for affordable capnography in every operating theatre.

Why capnography is mandatory in anaesthesia

Every major anaesthesia body requires it.

The American Society of Anesthesiologists makes continuous monitoring of expired carbon dioxide a standard for every patient receiving general anaesthesia, unless invalidated by the patient, procedure or equipment. The Association of Anaesthetists lists capnography alongside ECG, pulse oximetry and blood pressure as the minimum monitoring for general anaesthesia, to begin before induction and continue through to recovery. It is essential at all times for patients with a tracheal tube or a supraglottic airway.

The point is simple. Under anaesthesia, a patient cannot tell you they have stopped breathing. The capnograph tells you instead, within one breath.

What capnography monitors during anaesthesia

Across the case, capnography does several jobs at once.

It confirms the tube or airway is correctly placed. It monitors the adequacy of ventilation, breath by breath, whether the patient is ventilated or breathing spontaneously. It shows the effect of every change you make to the ventilator. And it keeps watching through transfer and recovery, until the airway is removed and the patient responds. To read the trace, see capnography waveforms, and for the values, the normal EtCO₂ range.

The emergencies capnography catches first

This is where capnography earns its mandatory status. It is often the earliest sign of a crisis in theatre.

Each of these shows on the capnograph before it shows anywhere else. In malignant hyperthermia, a rising EtCO₂ that outpaces ventilation is a classic early warning. In an air embolism during laparoscopy or a sitting-position case, a sudden drop can be the first clue. The monitor buys time to act.

FiCO₂ and rebreathing

One role deserves its own section, because it is specific to the anaesthesia circuit.

FiCO₂ is the fraction of inspired carbon dioxide, the CO₂ the patient breathes back in. In a healthy circuit it should be near zero. When it rises, the patient is rebreathing carbon dioxide, most often because the soda lime is exhausted or a valve has failed. A monitor that displays FiCO₂ catches this directly, before the patient is harmed. See how this appears in soda lime and the capnograph.

Not every capnograph measures FiCO₂. In an anaesthesia setting, one that does gives you an extra layer of safety.

Reading the number and the waveform

The value and the shape work together.

A normal EtCO₂ with a square waveform is reassuring. A changing number, or a normal number with an abnormal shape, is where the information is. During anaesthesia, watch the trend. A slow rise may be rebreathing or rising CO₂ production. A slow fall may be hyperventilation or falling cardiac output. The waveform tells you which. For the airway side of this, see endotracheal tube confirmation.

What the standards require

The direction of global guidance is clear, and it matters for India.

The ASA and the Association of Anaesthetists make capnography a minimum standard for general anaesthesia. The World Health Organization and the World Federation of Societies of Anaesthesiologists, in their International Standards for a Safe Practice of Anesthesia, make continuous waveform capnography highly recommended, which is their term for essential, once robust and suitably priced devices are available. They have gone further and published minimum capnometer specifications, precisely so that affordable devices can bring capnography to every theatre, including in lower-resource settings. Affordability is not a compromise here. It is the stated route to universal safety.

Where RespiCOz fits

RespiCOz is designed for anaesthesia, and it fits the setting on the merits.

Anaesthesia patients are intubated or ventilated on a circuit, so the mainstream sensor sits exactly where it should, at the airway, for a fast and direct reading. It monitors FiCO₂ as well as EtCO₂, so rebreathing from exhausted soda lime is caught directly. It is portable, which suits anaesthesia delivered away from the main theatre, in imaging, endoscopy and day-care, and it works as a ready backup. And at ₹60,000 to ₹1,00,000, it answers the WFSA call for robust, suitably priced capnography rather than a device a hospital can only afford in one room.

It is CDSCO-approved and made in India, with a two-year warranty and local support. For how it compares with other portable units, see the best handheld EtCO₂ monitor.

Ready to buy? Request a quote for your hospital here.

Frequently asked questions

Is capnography mandatory during general anaesthesia? Yes. The ASA and the Association of Anaesthetists make continuous capnography a minimum monitoring standard for every patient under general anaesthesia, alongside ECG, pulse oximetry and blood pressure.

What does capnography detect during anaesthesia? It confirms the airway and monitors ventilation, and it is often the first sign of circuit disconnection, a misplaced tube, malignant hyperthermia, air embolism, rebreathing and bronchospasm.

What is FiCO₂ and why does it matter in anaesthesia? FiCO₂ is the inspired carbon dioxide the patient breathes back in. It should be near zero. A rising FiCO₂ warns of rebreathing, most often from exhausted soda lime or a failed valve.

How does capnography detect malignant hyperthermia? A rising EtCO₂ that outpaces ventilation is one of the earliest and most sensitive signs of malignant hyperthermia. Capnography often flags it before other signs appear.

When should capnography be used during anaesthesia? From before induction until the airway is removed and the patient responds, continuing through transfer and recovery. It should never be interrupted while an artificial airway is in place.

Conclusion

Capnography during anaesthesia is mandatory because it answers, continuously, the one question that matters most under anaesthesia: is the patient being ventilated. It confirms the airway, tracks every breath, and warns of emergencies before anything else does.

Use it from induction to recovery, watch the number and the waveform together, and choose a device that also shows FiCO₂ so rebreathing does not go unseen.

To see the wider clinical picture, start with our five capnography use cases.

To order RespiCOz or ask for a quote for your setting, get a quote here.