CAPNOGRAPHY

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ADVANCED CAPNOGRAPHY hosam m atef :

ADVANCED CAPNOGRAPHY hosam m atef

Objectives:

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.

Objectives:

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 CO 2 Partial-Rebreathing method. Describe the set-up used to measure cardiac output via the CO 2 Partial-Rebreathing method. List two additional uses for capnography.

Physiology of Carbon Dioxide:

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

Carbon Dioxide Monitoring Technology:

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

Key Technological Issues:

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

Sidestream vs. Mainstream:

Sidestream vs. Mainstream

The Normal Time Capnogram:

The Normal Time Capnogram

Phases of the Time Capnogram:

Phases of the Time Capnogram Phase I: Inspiration No CO 2 detected (hopefully) Phase II: Appearance of CO 2 in the system. Mixed alveolar and deadspace gas. Phase III: Plateau Constant emptying of alveolar gas. Presence of CO 2 through the end of the breath. Phase IV: Washout of CO 2 from subsequent inspiration.

Abnormal Waveforms:

Abnormal Waveforms Sudden loss of P ET CO 2 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

Abnormal Waveforms:

Abnormal Waveforms Exponential decrease in P ET CO 2 reflects a catastrophic event in the patient’s cardiopulmonary system. Sudden Hypotension/massive blood loss Circulatory arrest with continued ventilation Pulmonary embolism Cardiopulmonary Bypass

Abnormal Waveforms:

Abnormal Waveforms Gradual decrease in P ET CO 2 indicates a decreasing CO 2 production, or decreasing systemic or pulmonary perfusion. Hypothermia Sedation Hyperventilation Hypovolemia Decreasing Cardiac Output

Artifacts with Time-Based Capnograms:

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

End-Tidal CO2:

End-Tidal CO 2

Clinical Uses of Capnography :

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

Volumetric Capnography:

Volumetric Capnography

The Normal Volume-Based Capnogram:

The Normal Volume-Based Capnogram

Checklist for Interpreting a Volume-Based Capnogram:

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 P ET CO 2 . (6) Area under the curve represents the volume of expired CO 2 (VCO 2 ). Exhaled volume (8)

The Normal Volume-Based Capnogram:

The Normal Volume-Based Capnogram V d

Waveform Phases:

Waveform Phases % CO 2 Exhaled Volume I: Deadspace II: Perfusion III: Gas Distribution

Clinical significance:

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

↑ phase 1:

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

Phase 2 assessment:

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

 Phase 2:

 Phase 2 Decreased Perfusion Baseline

 Phase 2:

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

Phase 3 assessment:

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?

Slide29:

↑Phase 3 CO 2 Exhaled Volume increased phase 3

↑ or absent phase 3:

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

Airway - Alveolar Volume:

Airway - Alveolar Volume % CO 2 V D V ALV Exhaled Tidal Volume

Effective Tidal Volume:

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 can indicate on a breath-by-breath basis when PaCO 2 changes will be occurring before they actually rise.

Area X = Vol CO2 Allows determination of VCO2 in one min. (200 mL/min.):

Area X = Vol CO 2 Allows determination of V CO 2 in one min. (200 mL/min.) Exhaled Volume % CO 2 Volume CO 2 (Area X)

VCO2:

VCO 2 VCO 2 represents the volume of CO 2 eliminated. This is usually the same as what is produced. CO 2 balance is dependent on four factors: Production Transportation (cell to blood & blood to lungs) Storage (conversion to CO 2 containing substances in the muscle, fat and bone) Elimination Monitoring V A and VCO 2 allows for evaluation of a successful weaning process.

Waveform Regions Z = anatomic VD; Y = VD Alveolar:

Waveform Regions Z = anatomic V D ; Y = V D Alveolar % CO 2 V D V ALV %CO 2 in Arterial Blood Z X Y Exhaled Tidal Volume

Sum of VDanat (Z) and VDalv (Y) is Physiologic VD:

Sum of V Danat (Z) and V Dalv (Y) is Physiologic V D X Y Z PaCO 2 - PeCO 2 PaCO 2 Y + Z X + Y + Z = Phys V D / V T Alveolar Ventilation Min. Vol. CO 2 ( VCO 2 )

Uses of Volumetric Capnography:

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

Slide38:

EXPECTED

Using Vtalv and VCO2 to Recruit Alveoli in a Postoperative CABG Patient Suffering from Hypoxemia:

Using Vt alv and VCO 2 to Recruit Alveoli in a Postoperative CABG Patient Suffering from Hypoxemia HOSAM M ATEF

Using Vtalv and VCO2 to Recruit Alveoli:

Using V t alv and V CO 2 to Recruit Alveoli Patient Profile 72 yo male, post-op CABG, MV Clinical Challenge Developed a low S p O 2 within 2 hours of arrival into the ICU F I O 2 and PEEP increased, no acceptable change in P a O 2 and S p O 2 Clinical Intervention Lung recruitment

Slide41:

Clinical Course PEEP increased by 2 cm H 2 O every 10 minutes Observed V t alv , V CO 2 and S p O 2 Monitoring Data Red arrows show PEEP increases No deterioration in V CO 2 , V/Q stable V t alv starts to increase at 16 cm H 2 O, alveoli are being recruited S p O 2 responded at 20 cm H 2 O Using V t alv and V CO 2 to Recruit Alveoli

Using Vtalv and VCO2 to Recruit Alveoli:

Summary V t alv is an ideal parameter to show alveolar recruitment V CO 2 indicates V/Q status during the procedure S p O 2 did not show improvement until best PEEP V t alv combined with V CO 2 were best to indicate increased PEEP levels were working Using Vtalv and VCO2 to Recruit Alveoli

Uses of Volumetric Capnography:

Uses of Volumetric Capnography Optimal PEEP Overdistension leads to increased V d anat and reduced perfusion. Increased V d anat 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 V CO 2 .

Increasing PEEP – :

Increasing PEEP – Expanded Airways increase V d anat .(zone Y) Expanded alveoli restrict perfusion so increased V dalv . (Zone Z) Exhaled Volume 0 3 6 9 12 15 cmH 2 O

VCO2 to Determine Optimal PEEP:

V CO 2 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 P a O 2 , S p O 2

VCO2 to Determine Optimal PEEP:

Clinical Intervention Maximize lung recruitment Determine optimal PEEP Without aversely affecting intracranial pressures Clinical Course Monitor V CO 2 and V A Increase PEEP in 2 cm H 2 O increments VCO2 to Determine Optimal PEEP

VCO2 to Determine Optimal PEEP:

Results PEEP increased from 14 to 20 Each step increased V A , V CO 2 initially decreased but recovered At PEEP of 22, V A did not increase, V CO 2 did not recover PEEP reduced to 20, V CO 2 recovered 22 cmH 2 0 Optimal PEEP VCO2 to Determine Optimal PEEP

VCO2 to Determine Optimal PEEP:

Determining Optimal PEEP V A Showed sharp rises after initial PEEP settings A result of alveolar recruitment V CO 2 Initial decrease after PEEP increase, recovered quickly Confirmed that pulmonary perfusion was not compromised VCO2 to Determine Optimal PEEP

Improvement in Distribution of Ventilation in Asthma:

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

Which graph represents ARDS?:

Which graph represents ARDS? Graphs show P E CO 2 vs. Volume (hatched line). V A E represents the “alveolar ejection volume” (true alveolar gas mixing volume).

Uses of Volumetric Capnography:

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 V d /V t P a CO 2 -P ET CO 2 gradient with maximum exhalation. Late deadspace fraction (F d late)

Uses of Volumetric Capnography:

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

Partial Rebreathing Method:

Partial Rebreathing Method If we measure the VCO 2 and arterial CO 2 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 CO 2 and allow for a change the VCO 2 and arterial (end-tidal) CO 2 , we can determine the amount of change in these values. The ratio of the change in VCO 2 to that of arterial CO 2 is equivalent to the Cardiac Output. The difference in venous CO 2 values is ignored as it is determined by the amount of CO 2 that is returned to the lungs, which is constant.

Calculation involved with NICO:

Calculation involved with NICO

Other uses for Capnography:

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 P ET CO 2 >30 had DKA. J Paeditr Child Health Oct 2007, 43(10):677-680 V d /V t ratio and ARDS Mortality Elevated Vd/Vt early in the course of ARDS was correlated with increased mortality. Chest Sep 2007, 132(3): 836-842 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

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