20 CAPNOGRAPHY ppt 3.pptx and various conditions

anesthesia

1. CAPNOGRAPHY Dr. Somasekharam .P Prof & HOD MVJ Medical College, Hoskote , Bangalore

2. Q what is a capnogram ?

3. Ans : Monitoring the CO 2 concentration in the expired air continuously as a function of time resulting in a graphic display of the wave form is called capnography the devise used to get the graph is called a capnograph . Tracing of the graph/ wave form, on a paper is called a capnogram . A Capnometer is a device which measures CO 2 concentration in a mixture of gasses and displays numerically. No wave form. The Process is called capnometery  

4. Q.What are the principles used in capnography?

5. Ans: A) Infrared light spectroscopy B) Mass spectroscopy C) Raman Scattering D) Photoacoustic spectroscopy

6. Infrared spectroscopy: When infrared light is passed through a mixture of gasses, certain gasses including co 2 absorb I.R. light of particular wave lengths. Maximum absorption of I.R light by CO 2 occurs at a wave length of 430nm. So this wave length of I.R light is passed through the expired air containing unknown concentration of CO 2 .CO 2 molecules absorb some IR light. The remaining is transmitted. The intensity of transmitted light is compared with that of a reference beam and calculated. IR Spectroscopy is reliable, cheap, and so routinely used in our day to day monitors

7. What are the types of analysers available in infrared spectroscopy ? Two types – 1) Side stream analyser 2) Main stream analyser

8. 1) Side stream analyser - The gas is sampled close to the patient at the E.T.T connector and aspirated through a small diameter tube to the I R analyser . The sampling flow rate should be around150ml/min, The range being 50 to 250ml/min Advantages: reliable, cheap . Disadvantages: Clogging and condensation by moisture. it can be reduced by traps and filters. Water vapour absorbs infra IR light.

9. 2) Main stream analyser - Measures directly from the airway through a sensor placed at the ETT connector with a special adapter. The sensor is connected to the analyser by a cable. Advantages: Fast reading Disadvantages: Increased size, weight, high cost and fragility.

10. Wave forms

11. Q.Describe the normal capnogram during controlled mechanical ventilation?

12. A normal capnogram during controlled mechanical ventilation is a square one. It is divided into four phases. Phase I: Inspiratory base line, CO 2 is normally Zero during this phase with circle absorber. With bain’s it is a little above zero. Phase II: Expiratory Upstroke, It is produced by the beginning of emptying of alveoli, contains a mixture of dead space gas & alveolar gasses. Phase III: Produced by the alveolar gas, The slope continues to rise gently because of uneven emptying of alveoli. Usually the CO 2 concentration at the end of expiration is the peak value and is referred to as end tidal CO 2 expressed as P ET CO 2 Phase IV: Inspiratory down stroke. This becomes less steep and more slanting with rebreathing. The angle between phase II and III is called α, and normally it is between 100 to 110 degrees. The angle between phase III and the descending limb is called β, normally it is 90 degrees.

13. Q.What type of wave form do you get in bronchospasm, COPD, partially obstructed ETT?

14. In COPD exhalation is slow and obstructed the curves show progressive slanting and prolongation of expiratory upstroke, This happens in obstructed ETT and bronchospasm also.

15. Q.What does this type of wave form indicate ?

16. This indicates beginning of spontaneous breathing while on controlled ventilation. The patient is attempting to breathe. Deflections are called curare clefts .They normally appear at the last one third of the Plateau, They indicate the need to repeat muscle relaxant to continue surgery

17. Q How can you make out hypopharyngeal dislodgement during ventilation?  

18. Irregular plateau and baseline may result from displacement of tracheal tube in to the hypopharynx. It causes only small volume of gas to move in and out of lungs

19. Q. How does a normal capnogram during spontaneous breathing look like?  

20. In spontaneous respiration Phase III appears as a peak rather than plateau .the graph would be like what is shown above

21. Q. What are cardiogenic oscillations in capnograph ?

22. Cardiogenic oscillations occur at the end of exhalation as flow decreases to zero , and the beating heart causes emptying of different lung regions and back and forth motion between exhaled and fresh gas due to motion of the heartbeat. It is very common in pediatric patients because of the relative size of the infant’s heart and thorax.  

23. Q. How do you recognize oesophageal intubation through capnography?

24. In oesophageal intubation, in the beginning there will be gastric wash out of residual CO 2 present in the stomach. Subsequently it will be zero.

25. Q. What type of graph you find in low cardiac output?

26. In case of low cardiac output there will be reduction in pulmonary blood flow and hence there will be drop in ETCO 2 . Sudden drop in ETCO 2 represents reduction in pulmonary blood flow as in pulmonary embolus.

27. Q. What does this type of graph in capnograph indicate?

28. This type of capnograph indicates return to spontaneous ventilation after the muscle relaxant effect wears of, the first breath is typically of small volume

29. Q. What type of graph you get in rebreathing of CO 2 ?

30. In rebreathing of CO 2 the baseline is elevated and the wave form is normal in shape. There will be presence of CO 2 in the gas that is inspired .This occurs if the CO 2 absorber in the circle system is exhausted or if there is deliberate addition of CO 2 to fresh gas, or incompetent expiratory or inspiratory valve .

31. Q. What happens to capnograph wave form in hypo ventilation?

32. In hypoventilation we will find increase end tidal CO 2 .This happens whenever there is increase CO 2 delivery to the lungs as in malignant hyperthermia,CO 2 insufflation of peritoneum during laparoscopic surgeries. A similar curve may be seen in increased temperature, shivering. Release of tourniquet etc .

33. Q. What type of graph we get in hyper ventilation?

34. In hyper ventilation we get low end tidal CO 2 . This due to increase dead space ventilation.

35.   Q. What is trend capnogram how is it helpful in CPR?

36. Regular or high speed capnogram is what we have seen all the time. It gives detailed information about each breath. Where as the overall trend as in CPR can be followed by slow speed or trend capnogram , in the above picture we can see progressive fall in ETCO 2 because of fall in cardiac output leading to cardiac arrest. Immediate chest compressions and increase in cardiac output is noted by increase ETCO 2

37. Some factors which increase ETCO2 Due to increase co2 production Malignant hyperthermia Thyroid storm or hyperthyroidism Malignant neuroleptic syndrome Sepsis Fever, shivering, etc Extraneous Co2- laparscopy Due to decrease in co2elimination Hypoventilation Rebreathing Due to technical failure Improper calibration Malfunction or contamination of measuring system Some factors which decrease ETCO2 Due to decrease in co2 production Hypothermia Hypothyroidism General Anaesthesia Due to increase in co2 elimination Hyperventilation 3. Due to decrease in alveolar delivery of co2 Decrease cardiac output states Pulmonary embolism Pulmonary odema Intrapulmonary of intra cardiac shunts Due to technical failure Sampling tube leak or block Disconnection of breathing system

38. Thank you