Dr. Radhika Dhanpal

radhika.dhanpal@rediffmail.com

Professor and Head

Department of Anesthesiology and Critical Care,St. John’s Medical College Hospital

Bangalore

www.anaesthesia.co.in Email: anaesthesia.co.in@gmail.com

ASA House of delegates July 1, 2011 implementation of Oct 2010 decision “Standards for Basic Anesthesia Monitoring”During regional anesthesia (with no sedation ) or local anesthesia (with no sedation ), the adequacy of ventilation shall be evaluated by continual observation of qualitative clinical signs. During moderate or deep sedation, the adequacy of ventilation shall be evaluated by continual observation of qualitative clinical signs and monitoring for the presence of exhaled CO2 unless precluded or invalidated by the nature of the patient, procedure or equipment”

ISA – Desirable standard 1999

Definition : Graphic display of instantaneous CO2 concentration

LuftCollier RamwellHolland in 1978 , was the first country to adopt it as a

standard of monitoring during anaesthesia .

Capnometer The machine Capnography Wave form

Capnometry Numerical Valve

Methods of measurement

Infrared spectrography

Raman spectrography

Mass spectrography

Photoacoustic spectrography

Chemical colorimetric analysis

Raman spectrography

Gas sample is aspirated into the analysing chamber where it is illuminated by a high intensity monochromatic argon laser beam. The light is absorbed by molecules which are then excited to unstablevibrational or rotational energy states, these Raman scattering signals are then measured.

Mass spectrography

It separates gases and vapors of different molecular

weight on the basis of their mass into a spectrum. By

analyzing the spectrum, the composition and relative

abundance of each gas in a sample can be determined .

Infrared method :

Infrared waves at 4.3 mm are absorbed by certain gases producing absorption bands on the infrared electromagnetic

spectrum.

Photoacoustic gas measurements

The gas to be measured is irradiated by modulated light of a pre-selected wavelength . The light beam when chopped, generates an acoustic signal which is detected by two microphones.

Colorimetric method

Chemically treated foam indicator attached to endotracheal tube.

Factors influencing the reading ;

a) Atmospheric pressure : Changes in atmospheric pressure are usually of the order of 20 mm Hg . This results in a change in PaCO2 of less than 0.5 - 0.8 mm Hg

b)PEEP .c) Water vapour : Can condense on the sensor cell and produce falsely

high readings. This may be prevented byHeating sensor above body temperature sampling tube can be made of a semipermeable polymer that allows

water vapour to pass outside.Absorbent filters.

TYPES –IIMain stream capnography

Disadvantages : Heavy Hot Window to be kept clean

Advantages : Faster No gas is removed No uncertainity by rate of gas sampling

Calibration :

Periodically

Gas of known CO2 concentration

Calibration cells with mixtures of CO2 and N2 are available.

Sampling tube should be the same type as the one used on the patient.

Type of capnogram

Time capnogram

Volume capnogram

Fast 7mm/sec

Slow 0.7 mm/sec

Time capnogram

Inspiratory segment Expiratory segment

Alpha angle

Beta angle

Phase I No CO2 Anatomical and apparatus dead space gas Phase II Rising CO2 Mixing of dead space gas and alveolar gas.Phase III Static or

rising CO2Alveolar gas

Phase IV Falling CO2

Beginning of inspiration

α angle - 100-110º ; Airway Obstruction causes larger angle. β angle - 90º ; Rebreathing increases the angle.

Volume capnogram

Advantage s• Volume of CO2 per exhaled breath can be measured • Significant changes in the morphology of the expired wave form can be detected • Dead space can be partitioned Disadvantages • Intubation mandatory • Elaborate equipment• Only monitors expiration

Interpretation of the waveform

Height

Frequency

Rhythm

Baseline

Shape

PaCo2 – PEtCo2-1

Normal 2-5 mmHg

Increased Decreases

Age Large TV

Pulmonary disorders Low Frequency Ventilation

PE Pregnancy

CO Infants

Hypovolemia

Anaesthesia

CO2 insufflation ( peritoneum , Pleura , joint )

Metabolic PaCo2 – PEtCo2-2

Increase DecreaseHyperpyrexia HypothermiaShivering Increased Muscle relaxation ConvulsionsBlood /NaHCO3 administration Release of an arterial clamp/tourniquetDextrose containing fluidsParenteral hyperailmentation

PaCo2 – PEtCo2-3

Circulatory Increase Decrease

Epinephrine injection CO

CPR • Surgical manipulations of the heart, great vessels, wedged PAC, PE• Air Embolism

Uses Anaesthesia

Verification of tracheal intubation Assist in blind oral or nasal intubation Needle cricothyroidotomy Jet stylet introducer Fiberoptic bronchoscopy Double lumen tube placement Monitoring of spontaneous ventilation Curare cleft HFJV Detection of circuit leaks Detection of malfunction of valves or faulty anaesthetic system.

Critical Care

CPCRDetermine the needs during mechanical ventilation WeaningPlacement of NG tube

Others

PACUPatient transferPost operative ward Procedural sedation Apnea test for brain death Emergency Department

REBREATHING WITH ELEVATED BASELINE

ESOPHAGEAL INTUBATION WITH CARBONATED BEVERAGES IN STOMACH

CO2 ABSORBENT EXHAUSTION

ESOPHAGEAL INTUBATION

ESOPHAGEAL INTUBATION FOLLOWING MASK VENTILATION.

EXPIRATORY VALVE MALFUNCTION

SPONTANEOUS BREATHING

NORMAL WAVEFORM

CURARE CLEFT

AIR LEAK

HYPERVENTILATION

CONTAMINATION OF

CO2 SENSOR

CARDIAC ARREST,SUCCESSFUL RESUSCITATION

HYPOVENTILATION

BRONCHOSPASM

IMV WITH INTERPOSED SPONTANEOUS RESPIRATION.

CARDIOGENIC OSCILLATIONS (RIPPLE

EFFECT)

INSPIRATORY VALVE

MALFUNCTION

POST SINGLE LUNG TRANSPLANTATION.

BAIN CIRCUIT/MAPELSON D (SIGNATURE CAPNOGRAM)

Thank You

www.anaesthesia.co.in Email: anaesthesia.co.in@gmail.com