Better understanding of Capnography by Weaam Abdalla

All the informations that you need to know about capnography and CO2 measurements techniques

1. B y: Weaam Abdalla

2. Capnography : Probably the least understood, non-invasive vital sign.

3. Learning Objectives : History of capnography . CO2 production, transport and elemination. Differentiate ventilation from oxygenation Define capnography . The differences between Mainstream and Side stream capnography . Articulate barriers to capnography technology use .

4. History : Based on a discovery in 1875 by chemist Joseph Black He noted the properties of a gas released during exhalation that he referred to as “fixed air” That fixed air was determined to be carbon dioxide .

5. Oxygenation VS Ventilation Oxygenation : The addition of oxygen to any system, Oxygenation may also refer to the process of treating a patient with oxygen Ventilation : T he movement or exchange of air between the environment and the lungs via inhalation and exhalation. BASICALLY: to take in oxygen (O2 ) and eliminate carbon dioxide (CO2 ).

6. What Is Capnography? Capnography is an objective measurement of exhaled carbon dioxide (CO2 ) levels at the end of each breath . commonly referred to as EtCO2 . The t erm capnography comes from the Greek wor d KAPNOS, meaning smoke . Gives information about ventilation, cardiac output, distribution of pulmonary blood flow and metabolic activity . The other method to measuere CO2 in the body is by arterial and venous blood gas, which is more invasive and costy.

7. Terminology : EtCO2 : C oncentration of CO2 against time

8. C olour change colormetry: has fale +ve results because of high sensetivity.

9. Mechanism: The Beer–Lambert law : chemical analysis measurement to determine the concentration of chemical species that absorb light .

10. EtCO2

11. This gap will increase with decrease in pulmonary blood flow as in PE, COPD, ARDS. A lveolar dead space

12. Types: Mainstream CO2 samples are taken directly from the airway. This method provides a very accurate reading because the sensor is at the actual airway , is widely regarded as the more accurate method of measuring EtCO2 , old version was heavy, can cause skin burn. Side stream : CO2 uses a sensor that is located inside the monitor instead of an external sensor. The patient’s exhalation air is pulled through a small tube, usually 6-8’ long, from the sample site and into the monitor.

13. C auses of abnormal Etco2: High: H ypoventilation. Hyperthermia. NaHCO3. Rebreathing. Low: H yperventilation Hypothermia. Decreased COP. PE. H ypovolemia . Hypotension.

14. Instrument factors: K inking. D isconnection. L eak. O cclustion. M alfunctiong. Expiratory valve malfunction.

15. Advantages: Tube Misplacement/Displacement (unrecognized esophageal intubation) Improved Resuscitation Outcomes . Better CPR, quality of chest compression, and ROSC. Assessment of Pulmonary Circulation and Respiratory Status . Optimization of Mechanical Ventilation , patient-ventilator asynchrony. PCA . P rocedure sedation. T ransfer of critically ill patients. Early detection of apnea or sever airway obstruction. Asthma/OSA .

16. Barriers to Use of Capnography : V ery high RR. Secretions. NaHCO3. ECMO and Dialysis. Know ledge: Differing EtCO2 technologies . Varying features and functions . Initial training of staff/physicians . Expense to hospital .

17. SpO2 EtCO2 : Familiar . easy concept. Easy to use and understand Non-invasive . Pain free W hat dose it tell us: Oxygenation status . Detects hypoxia Quick and reliable indicator… but is it quick enough? 1-2 min delay. Will show an elevated saturation for up to several minutes, as it takes time for existing oxygen saturation to decline. M ay fail to detect respiratory deterioration, particularly if a patient is receiving supplemental oxygen. May not detect left shift in oxy Hb disociation curve. Easy to use. Easy to interpret . Non-invasive, Pain free . W hat dose it tell us: Ventilation status Detects respiratory rate changes . and apnea . Detects ventilation potential changes with each breath. Quick, reliable indicator; changes caught sooner , reflects changes in ventilation within 10 seconds . I mpaired gas exchange is visible 30-60 seconds sooner than with SpO2 .

18. Rebreathing: F alty expiratory valve. I nadeqet inspiratort flow. M alfunction CO2 absorpant. L arg heart

19. We need to challenge our current monitoring practices and no longer believe that: Trusting that intermittent spot checks of vital signs is sufficient . Continuously monitoring only high risk patients . Relying on Pulse Ox alone to detect respiratory depression .

20. Take home messege: Regardless of the future, capnography is an emerging and growing parameter . ca pnography is a life-saving modality as it provides an early indicator of potentially 2 critical conditions . Knowledge is power—educate yourself on capnography!

21. C an EtCO2 replace s SPO2?

22. Test: