1. ADVANCED CAPNOGRAPHY

2. Objectives List three indications for capnography.
Differentiate between mainstream and sidestream capnography.
Given a time-based capnogram, identify and distinguish between the phases.
Given a time-based capnogram, interpret any abnormality present.
Given a volume-based capnogram, identify and distinguish between the phases.
Given a volume-based capnogram, state the significance of each phase.

3. Objectives
Given a volume-based capnogram, interpret any abnormality present.
List two instances where volume-based capnography can lead to improved patient management.
State the formula used for the calculation of non-invasive cardiac output via the CO2 Partial-Rebreathing method.
Describe the set-up used to measure cardiac output via the CO2 Partial-Rebreathing method.
List two additional uses for capnography.

4. Physiology of Carbon Dioxide
ALL THREE ARE IMPORTANT!
METABOLISM
PERFUSION
VENTILATION

5. Carbon Dioxide Monitoring Technology
Mass Spectroscopy
Methods of Sampling
Mainstream
Sidestream
Microstream

7. Key Technological Issues
Calibration
Moisture Control
Sample flow rate
Transit time
Response time

8. Sidestream vs. Mainstream

9. The Normal Time Capnogram

10. Phases of the Time Capnogram
Phase I: Inspiration
No CO2 detected (hopefully)
Phase II: Appearance of CO2 in the system.
Mixed alveolar and deadspace gas.
Phase III: Plateau
Constant emptying of alveolar gas.
Presence of CO2 through the end of the breath.
Phase IV: Washout of CO2 from subsequent inspiration.

11. Abnormal Waveforms
Sudden loss of PETCO2 to zero or near zero indicates immediate danger because no respiration is detected.
Esophageal intubation
Complete airway disconnect from ventilator
Complete ventilator malfunction
Totally obstructed/kinked endotracheal tube

12. Abnormal Waveforms
Exponential decrease in PETCO2 reflects a catastrophic event in the patient’s cardiopulmonary system.
Sudden Hypotension/massive blood loss
Circulatory arrest with continued ventilation
Pulmonary embolism
Cardiopulmonary Bypass

13. Abnormal Waveforms
Gradual decrease in PETCO2 indicates a decreasing CO2 production, or decreasing systemic or pulmonary perfusion.
Hypothermia
Sedation
Hyperventilation
Hypovolemia
Decreasing Cardiac Output

14. Artifacts with Time-Based Capnograms
Patient efforts
“Curare cleft”
Cardiac Oscillations

15. End-Tidal CO2

16. Clinical Uses of Capnography
Weaning
Hyperventilation monitoring
Use in Cardiac Arrest
Intubation verification
Restoration of Spontaneous Circulation
Easy Cap

17. Volumetric Capnography

18. The Normal Volume-Based Capnogram

20. Checklist for Interpreting a Volume-Based Capnogram
Phase I – Deadspace Gas
Rebreathing? (1)
Deadspace seem right?
Phase II – Transitional Phase
Transition from upper to lower airways.
Should be steep. (3)
Represents changes in perfusion.
Phase III – Alveolar Gas Exchange
Changes in gas distribution.
Increased slope = mal-distribution of gas delivery. (5)
End of Phase III is the PETCO2. (6)
Area under the curve represents the volume of expired CO2 (VCO2).
Exhaled volume (8)

21. The Normal Volume-Based CapnogramVd

22. Waveform Phases % CO2 I: Deadspace II: Perfusion III: Gas Distribution
Exhaled
Volume
Summarize the phases

23. Clinical significance
Phase 1
↑ depicts an ↑ in airways dead space.
Phase 2
↓ slope depicts reducing perfusion.
Phase 3
↑ slope depicts mal-distribution of gas.

24. ↑ phase 1
Phase 1 – relatively short
Phase 1 - prolonged

25. Phase 2 assessment If  in phase 2 Assure stable minute ventilation
Assess PEEP level
↑ intrathoracic pressure may cause  venous return
Assess hemodynamic status
Is minute ventilation stable?
Volume resuscitation or vasopressors may be indicated

26.  Phase 2
Baseline
Decreased Perfusion

27.  Phase 2
When minute ventilation is stable, indicative of a  in perfusion.

28. Phase 3 assessment
If ↑ or absent phase 3 mal-distribution of gas at alveolar level exists
Assess for appropriate PEEP level
Inadequate PEEP may be present
Bronchospasm
Bronchodilator tx my be indicated
Structure damage at alveolar level may be present
Pnuemothorax?

29. ↑Phase 3
CO2
increased phase 3
Exhaled Volume

30. ↑ or absent phase 3
Slope of phase 3 present and level
Phase 3 absent

31. Airway - Alveolar Volume
% CO2
…the slope of phase II is eliminated and a clear separation of deadspace is established. VD
VALV
Exhaled Tidal Volume

32. Effective Tidal Volume
The volume of gas between the end of Phase I and the end of Phase III.
Phase I represents the volume of gas being delivered from the ventilator which doesn’t participate in gas exchange.
Monitoring of the effective tidal volume (and A) can indicate on a breath-by-breath basis when PaCO2 changes will be occurring before they actually rise.

33. Area X = Vol CO2 Allows determination of VCO2 in one min. (200 mL/min
Volume CO2
(Area X)
Area under the SBCO2 curve IS the volume of CO2 in a single breath. Sum all the Co2 volumes in a minute and you get the same results as a Douglas Bag collection
Exhaled
Volume

34. CO2 CO2 represents the volume of CO2 eliminated.
This is usually the same as what is produced.
CO2 balance is dependent on four factors:
Production
Transportation (cell to blood & blood to lungs)
Storage (conversion to CO2 containing substances in the muscle, fat and bone)
Elimination
Monitoring A andCO2 allows for evaluation of a successful weaning process.

35. Waveform Regions Z = anatomic VD; Y = VD Alveolar
%CO2 in Arterial Blood
% CO2 Y Z X
If we add a horizontal line representing %CO2 in arterial blood, 4 distinct regions of the curve are established:
1 – Area X represents the actual amount of CO2 exhaled in the breath.
2 – Area Y represents the amount of CO2 that was NOT eliminated because we have some alveolar deadspace
3 – Area Z represents the amount of CO2 that was NOT eliminated because we have a certain anatomic structure
4 – Area X, Y and Z in total represent the maximum volume of CO2 possible to exhale in a single breath IF we have no airway deadspace AND no alveolar deadspace (or shunt). This would represent the perfect situation.
The relationship between the areas (with the added Arterial Blood line) gives us some very important parameters for analysis. VD
VALV
Exhaled Tidal Volume

36. Sum of VDanat (Z) and VDalv (Y) is Physiologic VD
PaCO2 - PeCO2
PaCO2
Phys VD / VT
Alveolar Ventilation
Min. Vol. CO2 ( VCO2 )
Y + Z
X + Y + Z = Y Z
Three very important ventilation assessment parameters emerge and mimic the action of the douglas bag…
The ratios of the areas created in the SBCO2 curve are the same as the relationship seen in the Enghoff modified Bohr equation.
Keep in mind here that the elimination of CO2 volume (VCO2) is necessary to balance CO2 produced in the metabolism process. Alveolar ventilation details how much ventilation is required to eliminate the CO2 volume that is presented to the alveoli by perfusion. X

37. Uses of Volumetric Capnography
Assess work of breathing during weaning trial.

38. EXPECTED

39. Using Vtalv and VCO2 to Recruit Alveoli in a Postoperative CABG Patient Suffering from Hypoxemia
Submitted by
Douglas C. Oberly, MS, RRT
Manager Respiratory Care Department
Hartford Hospital, Hartford, CT

40. Using Vtalv and VCO2 to Recruit Alveoli
Patient Profile
72 yo male, post-op CABG, MV
Clinical Challenge
Developed a low SpO2 within 2 hours of arrival into the ICU
FIO2 and PEEP increased, no acceptable change in PaO2 and SpO2
Clinical Intervention
Lung recruitment
P R O F I L E
This is a 72-year-old male patient, status post open heart surgery for four vessel CABG. The patient was taken to the Open Heart Cardiac Surgery Intensive Care Unit post procedure.
Ventilator settings:
SIMV 12, DP 22 cmH2O, IT 1.1 seconds, FIO2 40%, PEEP 5 cmH2O, PS 5 cmH2O. The ventilator settings were based on protocol
and the anesthesia settings.
Clinical problem:
The patient developed a low SpO2 within two hours of arrival into the ICU. FIO2 was increased to 60%, PEEP increased to 10 cmH2O, DP increased to 28 cmH2O. A subsequent blood gas revealed a PaO2 of 61 mmHg. The patient’s compliance was 41 cmH2O/mL.
Clinical intervention:
The Health Care Team (HCT) decided to utilize the NICO2 monitor to optimize PEEP and maximize lung recruitment.
Advanced Lung Recruitment Technology (ALuRT)

41. Using Vtalv and VCO2 to Recruit Alveoli
Clinical Course
PEEP increased by 2 cm H2O every 10 minutes
Observed Vtalv, VCO2 and SpO2
Monitoring Data
Red arrows show PEEP increases
No deterioration in VCO2,
V/Q stable
Vtalv starts to increase at 16 cm H2O, alveoli are being recruited
SpO2 responded at 20 cm H2O
CLINICAL COURSE
Patient was set up on the NICO2 monitor and baseline Vtalv, VCO2, and SpO2 was measured. PEEP was increased by 2 cmH2O every 10 minutes to observe increases in Vtalv and SpO2. If the lung overdistends, VCO2 will drop significantly (greater than 20%). At a PEEP level of 14 cmH2O, Vtalv, VCO2, and SpO2 did not change significantly. PEEP was increased by 2 cmH2O up to 20 cmH2O. Within 15 minutes, Vtalv, VCO2 and SpO2 increased. Subsequent PaO2 increased to 151 mmHg. Compliance increased to 81 cmH2O/ml. The DP and IT was decreased to maintain the same minute ventilation. FIO2 was decreased to 40%. Over the next hours, the patient’s PEEP was weaned utilizing the Vtalv parameter.

42. Using Vtalv and VCO2 to Recruit Alveoli
Summary
Vtalv is an ideal parameter to show alveolar recruitment
VCO2 indicates V/Q status during the procedure
SpO2 did not show improvement until best PEEP
Vtalv combined with VCO2 were best to indicate increased PEEP levels were working
DISCUSSION
Most patients undergoing heart/lung bypass have adequate lung re-expansion from aggressive manual bagging by the clinician in the operating
room prior to transfer to the ICU. If the procedure is not adequate, the patient can suffer from alveolar collapse and poor ventilation in the hours after the surgery. Using NICO2 to monitor Vtalv, VCO2, and SpO2 served two purposes:
1) increase the PEEP while monitoring for over distension
2) continuous monitoring of Vtalv to demonstrate the alveolar recruitment moment.
In this case, the lung was never “over distended” at anytime, no cardiac compromise was noted.
The reduction in DP, IT, and FIO2 facilitated a minimal support ventilation strategy.
Additional note:
Notice as the PEEP levels increased there was no deterioration in VCO2 indicating that V/Q was maintained. Vtalv was most sensitive to showing that alveoli were being recruited. SpO2 lagged until optimal PEEP was achieved.

43. Uses of Volumetric Capnography
Optimal PEEP
Overdistension leads to increased Vdanat and reduced perfusion.
Increased Vdanat can be assessed by an increase in Phase I volume.
Reduced perfusion can be assessed by a decrease in Phase II slope combined with a decrease in VCO2.

44. Increasing PEEP – Expanded Airways increase Vdanat.(zone Y)
cmH2O
Expanded Airways increase Vdanat.(zone Y)
Expanded alveoli restrict perfusion so increased Vdalv. (Zone Z)
Another example is in this increasing PEEP model…phase II shifts right due to expanding airways (increasing PEEP stints the airways open more). Notice that slope of phase II decreases as well. This is a result of lower CO2 concentration occurring at a identical volume point (in a less/more PEEP setting).
This demonstrates the need to manage alveolar volume in changing PEEP conditions…you must compensate for the loss of gas exchange volume
Exhaled Volume

45. VCO2 to Determine Optimal PEEP
Submitted by
Douglas C. Oberly MS, RRT
Manager, Respiratory Care Department
Hartford Hospital, Hartford, CT

46. VCO2 to Determine Optimal PEEP
Patient Profile
25 yo male, motorcycle accident
Head injury, rib fractures
Pentobarbital induced coma
Clinical Challenge
Developed acute lung injury
Low PaO2, SpO2
P R O F I L E
A 25-year-old male motorcycle operator struck a tree head-on. He sustained a massive head injury requiring ventriculostomy and eventually a pentobarbital-induced coma to control intracranial pressures. Patient rapidly
developed acute lung injury due to multiple rib fractures and bilateral lung contusions. Ventilator settings were PCV-AC, RR of 14 breaths/minute, DP of 25 cmH2O, FIO2 80%, PEEP 14 cmH2O. The patient’s arterial PO2 was 78 mmHg.

47. VCO2 to Determine Optimal PEEP
Clinical Intervention
Maximize lung recruitment
Determine optimal PEEP
Without aversely affecting intracranial pressures
Clinical Course
Monitor VCO2 and VA
Increase PEEP in 2 cm H2O increments
In light of the patient’s lung injury, the Health Care Team sought to maximize lung recruitment and determine the
patient’s optimal PEEP without adversely affecting intracranial pressures.

48. VCO2 to Determine Optimal PEEP
Results
PEEP increased from 14 to 20
Each step increased VA, VCO2 initially decreased but recovered
At PEEP of 22, VA did not increase, VCO2 did not recover
PEEP reduced to 20, VCO2 recovered
Optimal
PEEP
22 cmH20
C L I N I CA L C O U R S E
A baseline VCO2 trend was gathered. The NICO® Monitor was utilized to trend •VCO2 while PEEP was increased in 2 cmH2O increments. VCO2 was monitored for approximately five to seven minutes after each increase in PEEP. A decrease in VCO2 occurred immediately when PEEP was increased to 16 cmH2O. Over the next two minutes, sharp rises in MValv occurred and the VCO2 returned to baseline.
An increase in PEEP to 18 cmH2O resulted in a decrease in VCO2 and no change in MValv. Over the next two minutes, sharp rises in MValv occurred and the VCO2 returned to baseline. The trial continued until the PEEP level reached 22 cmH2O. At this point, VCO2 decreased by over 40 ml/min and did not rise. PEEP was decreased to 20 cmH2O and VCO2 increased. The subsequent blood gas resulted in an arterial PO2 of 120 mmHg. The FIO2 was decreased over the next hour to 50%. The NICO Monitor was utilized over the next 24 to 48 hours to assist in weaning PEEP.

49. VCO2 to Determine Optimal PEEP
Determining Optimal PEEP VA
Showed sharp rises after initial PEEP settings
A result of alveolar recruitment
VCO2
Initial decrease after PEEP increase, recovered quickly
Confirmed that pulmonary perfusion was not compromised
The NICO Monitor was instrumental in determining optimal PEEP. The sharp rises in MValv and VCO2 after the initial two PEEP changes were a result of lung recruitment. Once the patient was receiving 22 cmH2O of PEEP, the alveoli were over-distended and pulmonary capillaries were compressed preventing adequate CO2 diffusion across
the alveolar-capillary membrane. Determining optimal PEEP and fully recruiting the alveoli dramatically reduced
the FIO2 requirement.

50. Improvement in Distribution of Ventilation in Asthma
Asthma – Day 1 (dark) Day 5 (blue)

51. Which graph represents ARDS?
Graphs show PECO2 vs. Volume (hatched line).
VAE represents the “alveolar ejection volume” (true alveolar gas mixing volume).

52. Uses of Volumetric Capnography
Pulmonary Embolism
650,000 cases/year in US
50,000 to 200,000 die.
Most deaths occur within first hour.
Prompt therapy can reduce mortality from 30% to 2.5 to 10%.
70% of deaths from PE identified by autopsy were not identified before death.
Methods of PE detection
Evaluation of Vd/Vt
PaCO2-PETCO2 gradient with maximum exhalation.
Late deadspace fraction (Fdlate)

54. Uses of Volumetric Capnography
Non-Invasive Cardiac Output
Fick Principle (1870) OR

55. Partial Rebreathing Method
If we measure the VCO2 and arterial CO2 contents (substituting in end-tidal values for arterial and applying a solubility coefficient conversion), we can determine the cardiac output.
If we then allow for rebreathing of CO2 and allow for a change the VCO2 and arterial (end-tidal) CO2, we can determine the amount of change in these values.
The ratio of the change in VCO2 to that of arterial CO2 is equivalent to the Cardiac Output.
The difference in venous CO2 values is ignored as it is determined by the amount of CO2 that is returned to the lungs, which is constant.

57. Calculation involved with NICO

59. Other uses for Capnography
During Apnea Testing in Brain-dead patients.
Eur J Anaesthesia Oct 2007, 24(10):868-75
Evaluating DKA in children.
No patients with a PETCO2 >30 had DKA.
J Paeditr Child Health Oct 2007, 43(10):
Vd/Vt ratio and ARDS Mortality
Elevated Vd/Vt early in the course of ARDS was correlated with increased mortality.
Chest Sep 2007, 132(3):
PCA Administration
“Continuous respiratory monitoring is optimal for the safe administration of PCA, because any RD event can progress to respiratory arrest if undetected.”
Anesth Analg Aug 2007, 105(2):412-8