Air-leak – Loose connection between sampling tube
and capnograph / broken connection or filter.

Details
Following one lung transplantation.
If the tip of the endotracheal tube is too close to the carina, thereby resulting in differential lung ventilation due to partial obstruction. (see 15 and 23)

Rebreathing capnogram of Mapleson D circuit.
Bain circuit.

Details
Exhausted CO₂ absorber. See below ()

Cardiogenic oscillations – Ripple effect – Seen during low-frequency ventilation.

Details

Bronchospasm / COPD / Emphysema/ obstructed endotracheal tube -Slanting and prolonged phase 2 and increased slope of phase 3 (see 14)

Contamination of capnograph
Trend showing abrupt elevation of baseline and capnogram. See 43

Trend capnogram during cardiac arrest/resuscitation.

Upward slanting of phase 4. A normal variant in pregnant women during anesthesia.

Details

Trend showing gradual elevation of baseline.
Rebreathing

Curare cleft (see 10)

Resembling curare cleft due to an artifact created by a surgeon leaning on the chest or pushing against the diaphragm during expiration.
The partial disconnect of main stream capnometer

Details

Dilution of expiratory gases by the forward flow of fresh gases during the later part of expiration when the expiratory flow rate decreases below the forward gas flow rate.

Elevation of baseline- A classic representation of rebreathing.

Exhausted CO₂ absorber

A gradual decrease in end-tidal carbon dioxide can occur during reduced metabolism, hypothermia, hyperventilation, small tidal volume ventilation due to inadequate alveolar sampling, and leaks in the sampling system, decrease in cardiac output see 13

Occasionally, there can be a reverse phase 3 slope seen in patients with emphysema. Most like this may be due to destruction of alveolar capillary system in emphysematous lungs resulting in the delivery of carbon dioxide to expired gases.

Endobronchial intubation may not result in a characteristic waveform. However, occasionally, it may be like the one seen in COPD or the above. Read the 3 sections.

Details  see (15)

The CO₂ waveform has two humps. Kyphoscoliosis resulted in a compression of the right lung. Differential lung emptying. Details

Esophageal intubation.

Esophageal intubation: Small CO₂ spikes. Esophageal or gastric CO₂ due to mask ventilation

Warming up CO₂ analyzer is necessary before it begins recording CO₂ waveforms.

The monitor will zero periodically. Will show CO₂ numerical value with no waveform.

Ventilator IMV breath during spontaneous ventilation.

Sticking inspiratory valve – Inspiratory flip – Red indicates possible rebreathing

Air leak due to a broken connection between sampling tube and capnograph Details see (1)

Lung transplant – Dual capnogram Details see 1, 15 and 23

Increased CO₂ due to hypoventilation, hypermetabolic states, and rebreathing. See 8, 39

Capnogram during spontaneous ventilation in adults (see 27)

These capnograms can occur in children and neonates. Variations are normal and due to faster respiratory rates, smaller tidal volumes, and relatively longer response time of the capnographs. Recent technological advances such as micro-stream analyzers are reducing artifacts due to faster response time, producing normal-looking capnograms even in children and neonates.

Sampling problems such air or oxygen dilution during nasal or mask sampling of carbon dioxide in spontaneously breathing patients.

Slit sampling tube can result in a pigtail capnogram. A variation of 23 Details

A terminal upswing at the end of phase 3, known as phase 4, can occur in pregnant subjects, obese subjects and low compliance states. Details see also physiology section-phase 4.

Expiratory valve malfunction can result in prolonged abnormal phase 2 and phase 0.Details

Inspiratory valve malfunction predominantly results in abnormal phase 0. Details

Esophageal intubation resulting few abnormal capnograms with relatively normal initial CO₂ numerical values. Details

Hyperventilation gradually results in the lowering of ETCO₂ values. see 13

Hypoventilation gradually increases CO₂ values with a normal baseline. see 8 and 25

Rebreathing produces gradual elevation of baseline and ETCO₂ values. See 8

Carbonated beverages in the stomach can result in abnormal capnograms with progressively decreasing CO₂ values following esophageal intubation. See other variations 17, 18, 37

Unrecognized exhaustion of CO₂ absorber resulted in substantial rebreathing and rising ETCO₂ values. The closed circuit without a functioning absorber mimicked the Mapleson D circuit.   Details

Contamination of the capnometer results in the sudden elevation of baseline as well as ETCO₂ values. See 5