Abnormal capnogram waveforms

(A) Prolonged phase II, increased alpha angle, and steeper phase III suggest bronchospasm or airway obstruction.
(B) Expiratory valve malfunction resulting in elevation of the baseline, and the angle between the alveolar plateau and the downstroke of inspiration is increased from 90°. This is due to rebreathing of expiratory gases from the expiratory limb during inspiration.
(C) Inspiratory valve malfunction resulting in rebreathing of expired gases from inspiratory limb during inspiration (reference 1 for details).
(D) Capnogram with normal phase II but with increased slope of phase III. This capnogram is observed in pregnant subjects under general anesthesia (normal physiologic variant and details in reference 2).
(E) Curare cleft: Patient is attempting to breathe during partial muscle paralysis. Surgical movements on the chest and abdomen can also result in the curare cleft.
(F) Baseline is elevated as a result of carbon dioxide rebreathing.
(G) Esophageal intubation resulting in the gastric washout of residual carbon dioxide and subsequent carbon dioxide will be zero.
(H) Spontaneously breathing carbon dioxide waveforms where phase III is not well delineated.
(I) Dual capnogram in one lung transplantation patient. The first peak in phase III is from the transplanted normal lung, whereas the second peak is from the native disease lung. A variation of dual capnogram (steeple sign capnogram – dotted line) is seen if there is a leak around the sidestream sensor port at the monitor. This is because of the dilution of expired PCO₂ with atmospheric air.
(J) Malignant hyperpyrexia where carbon dioxide is raising gradually with zero baseline suggesting increased carbon dioxide production with carbon dioxide absorption by the soda lime.
(K) Classic ripple effect during the expiratory pause showing cardiogenic oscillations. These occur as a result of to-and-for movement of expired gases at the sensor due to motion of the heartbeat during expiratory pause when respiratory frequency of mechanical ventilation is low. Wave forms with a ripple effect also occur when forward flow of fresh gases from a source during expiratory pause intermingles with expiratory gases at the sensor.
(L) Sudden raise of baseline and the end-tidal PCO₂ (PETCO₂) due to contamination of the sensor with secretions or water vapor. Gradual rise of baseline and PETCO₂ occurs when soda lime is exhausted.
(M) Intermittent mechanical ventilation (IMV) breaths in the midst of spontaneously breathing patient. A comparison of the height of spontaneous breaths compared to the mechanical breaths is useful to assess spontaneous ventilation during weaning process.
(N) Cardiopulmonary resuscitation: Capnogram showing positive waveforms during each compression suggesting effective cardiac compression generating pulmonary blood.
(O) Capnogram showing rebreathing during inspiration. This is normal in rebreathing circuits such as Mapleson D or Bain circuit.