1. UTHSCSA Pediatric Resident Curriculum for the PICU CAPNOGRAPHY and PULSE OXIMETRY

2. UTHSCSA Pediatric Resident Curriculum for the PICU CAPNOGRAPHIC DEVICES Infrared Absorption Photometry Infrared Absorption Photometry Colorimetric Devices Colorimetric Devices Mass Spectrometry Mass Spectrometry Raman Scattering Raman Scattering

3. UTHSCSA Pediatric Resident Curriculum for the PICU INFRARED First developed in 1859. First developed in 1859. Based on Beer-Lambert law: Pa = 1 - e -  DC Based on Beer-Lambert law: Pa = 1 - e -  DC – Pa is fraction of light absorbed –  is absorption coefficient – D is distance light travels though the gas – C is molar gas concentration The higher the CO 2 concentration, the higher the absorption. The higher the CO 2 concentration, the higher the absorption. CO 2 absorption takes place at 4.25 µm CO 2 absorption takes place at 4.25 µm N 2 O, H 2 O, and CO can also absorb at this wavelength N 2 O, H 2 O, and CO can also absorb at this wavelength Two types: side port and mainstream Two types: side port and mainstream

4. UTHSCSA Pediatric Resident Curriculum for the PICU ABSORPTION BANDS

5. UTHSCSA Pediatric Resident Curriculum for the PICU SIDE PORT Gas is sampled through a small tube Gas is sampled through a small tube Analysis is performed in a separate chamber Analysis is performed in a separate chamber Very reliable Very reliable Time delay of 1-60 seconds Time delay of 1-60 seconds Less accurate at higher respiratory rates Less accurate at higher respiratory rates Prone to plugging by water and secretions Prone to plugging by water and secretions Ambient air leaks Ambient air leaks

6. UTHSCSA Pediatric Resident Curriculum for the PICU MAINSTREAM Sensor is located in the airway Sensor is located in the airway Response time as little as 40msec Response time as little as 40msec Very accurate Very accurate Difficult to calibrate without disconnecting (makes it hard to detect rebreathing) Difficult to calibrate without disconnecting (makes it hard to detect rebreathing) More prone to the reading being affected by moisture More prone to the reading being affected by moisture Larger, can kink the tube. Larger, can kink the tube. Adds dead space to the airway Adds dead space to the airway Bigger chance of being damaged by mishandling Bigger chance of being damaged by mishandling

7. UTHSCSA Pediatric Resident Curriculum for the PICU COLORIMETRIC Contains a pH sensitive dye which undergoes a color change in the presence of CO 2 Contains a pH sensitive dye which undergoes a color change in the presence of CO 2 The dye is usually metacresol purple and it changes to yellow in the presence of CO 2 The dye is usually metacresol purple and it changes to yellow in the presence of CO 2 Portable and lightweight. Portable and lightweight. Low false positive rate Low false positive rate Higher false negative rate Higher false negative rate Acidic solutions, e.g., epi, atropine, lidocaine, will permanently change the color Acidic solutions, e.g., epi, atropine, lidocaine, will permanently change the color Dead space relatively high for neonates, so don’t use for long periods of time on those patients. Dead space relatively high for neonates, so don’t use for long periods of time on those patients.

8. UTHSCSA Pediatric Resident Curriculum for the PICU NORMAL CAPNOGRAM

9. UTHSCSA Pediatric Resident Curriculum for the PICU NORMAL CAPNOGRAM Phase I is the beginning of exhalation Phase I is the beginning of exhalation Phase I represents most of the anatomical dead space Phase I represents most of the anatomical dead space Phase II is where the alveolar gas begins to mix with the dead space gas and the CO 2 begins to rapidly rise Phase II is where the alveolar gas begins to mix with the dead space gas and the CO 2 begins to rapidly rise The anatomic dead space can be calculated using Phase I and II The anatomic dead space can be calculated using Phase I and II Alveolar dead space can be calculated on the basis of : V D = V Danat + V Dalv Alveolar dead space can be calculated on the basis of : V D = V Danat + V Dalv Significant increase in the alveolar dead space signifies V/Q mismatch Significant increase in the alveolar dead space signifies V/Q mismatch

10. UTHSCSA Pediatric Resident Curriculum for the PICU NORMAL CAPNOGRAM Phase III corresponds to the elimination of CO 2 from the alveoli Phase III corresponds to the elimination of CO 2 from the alveoli Phase III usually has a slight increase in the slope as “slow” alveoli empty Phase III usually has a slight increase in the slope as “slow” alveoli empty The “slow” alveoli have a lower V/Q ratio and therefore have higher CO 2 concentrations The “slow” alveoli have a lower V/Q ratio and therefore have higher CO 2 concentrations In addition, diffusion of CO 2 into the alveoli is greater during expiration. More pronounced in infants In addition, diffusion of CO 2 into the alveoli is greater during expiration. More pronounced in infants ET CO 2 is measured at the maximal point of Phase III. ET CO 2 is measured at the maximal point of Phase III. Phase IV is the inspirational phase Phase IV is the inspirational phase

11. UTHSCSA Pediatric Resident Curriculum for the PICU ABNORMALITIES Increased Phase III slope Increased Phase III slope – Obstructive lung disease Phase III dip Phase III dip – Spontaneous resp Horizontal Phase III with large ET-art CO 2 change Horizontal Phase III with large ET-art CO 2 change – Pulmonary embolism –  cardiac output – Hypovolemia Sudden  in ETCO 2 to 0 – Dislodged tube – Vent malfunction – ET obstruction Sudden  in ETCO 2 – Partial obstruction – Air leak Exponential  – Severe hyperventilation – Cardiopulmonary event

12. UTHSCSA Pediatric Resident Curriculum for the PICU ABNORMALITIES Gradual  Gradual  – Hyperventilation – Decreasing temp – Gradual  in volume Sudden increase in ETCO 2 Sudden increase in ETCO 2 – Sodium bicarb administration – Release of limb tourniquet Gradual increase – Fever – Hypoventilation Increased baseline – Rebreathing – Exhausted CO 2 absorber

13. UTHSCSA Pediatric Resident Curriculum for the PICU PaCO 2 -PetCO 2 gradient Usually <6mm Hg Usually <6mm Hg PetCO 2 is usually less PetCO 2 is usually less Difference depends on the number of underperfused alveoli Difference depends on the number of underperfused alveoli Tend to mirror each other if the slope of Phase III is horizontal or has a minimal slope Tend to mirror each other if the slope of Phase III is horizontal or has a minimal slope Decreased cardiac output will increase the gradient Decreased cardiac output will increase the gradient The gradient can be negative when healthy lungs are ventilated with high TV and low rate The gradient can be negative when healthy lungs are ventilated with high TV and low rate Decreased FRC also gives a negative gradient by increasing the number of slow alveoli Decreased FRC also gives a negative gradient by increasing the number of slow alveoli

14. UTHSCSA Pediatric Resident Curriculum for the PICU LIMITATIONS Critically ill patients often have rapidly changing dead space and V/Q mismatch Critically ill patients often have rapidly changing dead space and V/Q mismatch Higher rates and smaller TV can increase the amount of dead space ventilation Higher rates and smaller TV can increase the amount of dead space ventilation High mean airway pressures and PEEP restrict alveolar perfusion, leading to falsely decreased readings High mean airway pressures and PEEP restrict alveolar perfusion, leading to falsely decreased readings Low cardiac output will decrease the reading Low cardiac output will decrease the reading

15. UTHSCSA Pediatric Resident Curriculum for the PICU USES Metabolic Metabolic – Assess energy expenditure Cardiovascular Cardiovascular – Monitor trend in cardiac output – Can use as an indirect Fick method, but actual numbers are hard to quantify – Measure of effectiveness in CPR – Diagnosis of pulmonary embolism: measure gradient

16. UTHSCSA Pediatric Resident Curriculum for the PICU PULMONARY USES Effectiveness of therapy in bronchospasm Effectiveness of therapy in bronchospasm – Monitor PaCO 2 -PetCO 2 gradient – Worsening indicated by rising Phase III without plateau Find optimal PEEP by following the gradient. Should be lowest at optimal PEEP. Find optimal PEEP by following the gradient. Should be lowest at optimal PEEP. Can predict successful extubation. Can predict successful extubation. – Dead space ratio to tidal volume ratio of >0.6 predicts failure. Normal is 0.33-0.45 Limited usefulness in weaning the vent when patient is unstable from cardiovascular or pulmonary standpoint Limited usefulness in weaning the vent when patient is unstable from cardiovascular or pulmonary standpoint Confirm ET tube placement Confirm ET tube placement

17. UTHSCSA Pediatric Resident Curriculum for the PICU CAPNOGRAM #1 J Int Care Med, 12(1): 18-32, 1997

18. UTHSCSA Pediatric Resident Curriculum for the PICU CAPNOGRAM #2 J Int Care Med, 12(1): 18-32, 1997

19. UTHSCSA Pediatric Resident Curriculum for the PICU CAPNOGRAM #3 J Int Care Med, 12(1): 18-32, 1997

20. UTHSCSA Pediatric Resident Curriculum for the PICU CAPNOGRAM #4 J Int Care Med, 12(1): 18-32, 1997

21. UTHSCSA Pediatric Resident Curriculum for the PICU CAPNOGRAM #5 J Int Care Med, 12(1): 18-32, 1997

22. UTHSCSA Pediatric Resident Curriculum for the PICU CAPNOGRAM #6 J Int Care Med, 12(1): 18-32, 1997

23. UTHSCSA Pediatric Resident Curriculum for the PICU CAPNOGRAM #7 J Int Care Med, 12(1): 18-32, 1997

24. UTHSCSA Pediatric Resident Curriculum for the PICU CAPNOGRAM #8 J Int Care Med, 12(1): 18-32, 1997

25. UTHSCSA Pediatric Resident Curriculum for the PICU PULSE OXIMETRY Uses spectrophotometry based on the Beer- Lambert law Uses spectrophotometry based on the Beer- Lambert law Differentiates oxy- from deoxyhemoglobin by the differences in absorption at 660nm and 940nm Differentiates oxy- from deoxyhemoglobin by the differences in absorption at 660nm and 940nm Minimizes tissue interference by separating out the pulsatile signal Minimizes tissue interference by separating out the pulsatile signal Estimates heart rate by measuring cyclic changes in light transmission Estimates heart rate by measuring cyclic changes in light transmission Measures 4 types of hemoglobin: deoxy, oxy, carboxy, and met Measures 4 types of hemoglobin: deoxy, oxy, carboxy, and met Estimates functional hemoglobin saturation: oxyhemoglobin/deoxy + oxy Estimates functional hemoglobin saturation: oxyhemoglobin/deoxy + oxy

26. UTHSCSA Pediatric Resident Curriculum for the PICU ABSORPTION SPECTRA

27. UTHSCSA Pediatric Resident Curriculum for the PICU SOURCES OF ERROR Sensitive to motion Sensitive to motion Standard deviation is certified to 4% down to 70% saturation Standard deviation is certified to 4% down to 70% saturation Sats below 85% increase the importance of error in the reading Sats below 85% increase the importance of error in the reading Calibration is performed by company on normal patients breathing various gas mixtures, so calibration is certain only down to 80% Calibration is performed by company on normal patients breathing various gas mixtures, so calibration is certain only down to 80%

28. UTHSCSA Pediatric Resident Curriculum for the PICU SOURCES OF ERROR Skin Pigmentation Skin Pigmentation – Darker color may make the reading more variable due to optical shunting. – Dark nail polish has same effect: blue, black, and green polishes underestimate saturations, while red and purple have no effect – Hyperbilirubinemia has no effect Low perfusion state Low perfusion state Ambient Light Ambient Light Delay in reading of about 12 seconds Delay in reading of about 12 seconds

29. UTHSCSA Pediatric Resident Curriculum for the PICU SOURCES OF ERROR Methylene blue and indigo carmine underestimate the saturation Methylene blue and indigo carmine underestimate the saturation Dysfunctional hemoglobin Dysfunctional hemoglobin – Carboxyhgb leads to overestimation of sats because it absorbs at 660nm with an absorption coefficient nearly identical to oxyhgb – Methgb can mask the true saturation by absorbing too much light at both 660nm and 940nm. Saturations are overestimated, but drop no further than 85%, which occurs when methgb reaches 35%.

30. UTHSCSA Pediatric Resident Curriculum for the PICU SOURCES OF ERROR Affect of anemia is debated Affect of anemia is debated Oxygen-Hemoglobin Dissociation Curve Oxygen-Hemoglobin Dissociation Curve – Shifts in the curve can affect the reading – Oximetry reading of 95% could correspond to a P a O 2 of 60mmHg (91% saturation) or 160mmHg (99% saturation)