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Bhavani Shankar Kodali MD

severe kyphoscoliosis.

Encyclopedia of capnograms

Bhavani Shankar Kodali MD

Biphasic carbon dioxide waveform in severe kyphoscoliosis

Image1

 

       Carbon dioxide waveform recorded in a patient with severe kypho-scoliosis. The CO2 waveform has two humps. Kyphoscoliosis resulted in a compression of the right lung. The compressed right lung had a relatively high airway resistance, was poorly ventilated, and was relatively hypercapnic,  whereas the left lung had a relatively low airway resistance, was hyperventilated, and was relatively hypocapnic. Under these circumstances, relatively hypocapnic gas from well ventilated, low airway resistance lung reached the CO2 analyzer first causing first distinct low peak, and relatively hypercapnic gas from poorly ventilated, high airway resistance lung reached the CO2 analyzer last causing second distinct high peak.


Reference

Nichols K, Benumof, JL. Biphasic carbon dioxide excretion from a patient with severe kyphoscoliosis. Anesthesiology 1989;71:986-7 (with permission).

 

 

endobronchial intubation Details

Encyclopedia of capnograms

Bhavani Shankar Kodali MD

Endobronchial intubation 

 Right mainstem intubation                         
 Endotracheal tube pulled back into the trachea
 Image1 Image2
  
    A biphasic carbon dioxide elimination waveform recorded in a patient with no known lung disease who was found to have a right main-stem bronchial intubation.

   This capnogram probably occurred as the tip of the endotracheal tube changed moved in out of right main bronchus during respiratory cycle. This resulted in partial obstruction to gases from left lung thereby prolonging  expiratory time from left lung. The initial peak is due to the carbon dioxide  from well ventilated right lung. The second peak is most likely due to prolonged expiratory time of poorly ventilated left lung.


Reference

Gilbert D, Benumof JL. Biphasic carbon dioxide elimination waveform with right mainstem bronchial intubation.  Anesth Analg 1989;69:829-32 (with permission).

 

breaks in the water filter of the carbon dioxide analyzer

Encyclopedia of capnograms

Bhavani Shankar Kodali MD

Dual Plateau capnogram caused by cracked sample filter 

 Image1

 

    A dual plateau capnogram was observed by Body  et al during anesthesia and IPPV. They found that the cause of the abnormality was due a microscopic crack in the filter membrane separator  cartridge of the Ohmeda RGM 5250 gas analyzer. The authors hypothesized that, during the initial phase of expiration, aspiration of the gas sample by the analyzer produced a negative pressure at the cracked sample filter that aspirated room air.  With the commencement of inspiration, positive pressure in the anesthesia circuit reduced the negative pressure at the sample filter and eliminated or reduced the aspiration of the ambient air, thus allowing, a second plateau more accurately reflected alveolar PCO2.
 
 
Image2

 

(Provided by Simon Body and James Philips)


Body et al. Dual Plateau capnogram caused by cracked sample filter. Anesth Analg 2000;Jan:233-34 (with permission).

Zuspan J, Martin M, Benumof JL. End-tidal CO2 excretion waveform and error with gas sampling line leak. Anesth Analg 1988;67:81.

 

 

transplanted lung details

Encyclopedia of capnograms

Bhavani Shankar Kodali MD

Lung transplant

Image1

 

     Biphasic capnogram recorded in a patient after single lung transplantation. This is due to different populations of alveoli.  The first peak represents expired carbon dioxide from allografted lung, which has normal compliance, good perfusion, and good ventilation-perfusion ratios (V/Q).  The second peak most likely reflects expired carbon dioxide from the native lung, because of slanted upstroke or steeper plateau is characteristic  of the mismatched V/Q ratios and differing alveolar time constants in emphysema. Independent of the perfusion characteristics of the two lungs, the differences in their compliance alone could account for the observed biphasic capnogram, with the transplanted lung emptying more rapidly than the native lung.


Reference

Williams EL, Jellish WS, Modica PA, Eng CC, Templehoff  R.  Capnography in a patient after single lung transplantation. Anesthesiology 1991;74:621-2 (with permission).

Biphasic capnograms can occur during sampling tube leaks, endobronchial intubation, and in severe kyphoscoliosis.

 

Slit Sampling tube (tail-up capnogram) Details

Encyclopedia of capnograms

Bhavani Shankar Kodali MD
 
 
Image1
 

Dual waveform capnogram


This capnogram occurs due to sampling leaks in the sampling tube cracks, or a loose connection between sampling tubes and the monitor. It has also been reported due to breaks in the water filter of the carbon dioxide analyzer.
 
 
Image2
 
(Provided by Simon Body and James Philips)

This shape of a capnogram can result in differential lung emptying of the lungs. For example one may be a normal lung (transplanted lung) and other, a diseased lung. The normal lung has greater carbon dioxide to expire than the diseased lung.

In addition, a dual capnogram can result during endobronchial intubation and in patients with severe kyphoscoliosis.

 

   Tripati et al have described another capnogram with a "tail up" as shown below during the use of an accidentally crushed sampling tube with a slit-like hole.
 
 Image3


   The authors investigated the mechanics involved in 40 consenting ASA I patients undergoing general anesthesia. They observed the "tail up" capnogram with lower end-tidal CO2 values with slit the sampling tubes as compared to the intact sampling tubes during IPPV. However, during spontaneous ventilation no such deformity was observed, although end-tidal CO2 was lower than the normal.

     A similar mechanism as described above may be operative during IPPV. However, during spontaneous ventilation, there is no positive pressure (infact, there is slight negative pressure) and therefore, the dilution of sampling gases through the leak continue in both phases of respiratory cycle. This gives a normal shape to the capnograms, but with lower end-tidal CO2 values as compared to intact or undamaged sampling tubes.

 

Reference:

Tripati M, Pandey M. Atypical "tails up" capnogram due to breach in the sampling tube of side-stream capnometer. J Clin Monit 2000;16:17-20.