Capnography Flashcards
(28 cards)
When was capnography mandated?
- 1989: CO2 indentified in expired gas to confirm ETT or LMA placement and assess ventilation in every GA
- 2011: CO2 monitoring for any patient undergoing moderate or deep sedation
What is capnometry?
Measurement and quantification of inhaled or exhaled CO2 concentrations measured by capnometer
What is capnography?
Method of CO2 measurement and a graphic display over time→ detector of CO2 breath by breath
Best method to confirm endotracheal intubation
How can CO2 be measured?
- Side- stream: aspirated gas sample and analyzes away from airway at a rate or 50-200 mL/min (MOST COMMON- transport time delay and rise time)
- Main-stream: Analyzes gas samples directly in the breathing circuit (No time delay, rise time faster)
What are the effects of hypercarbia?
- Respiratory acidosis
- Increases cerebral blood flow (CBF)
- Increases ICP in susceptible patients
- Increases pulmonary vascular resistance
- Potassium shifts from intracellular to intravascular
What are the effect of hypocarbia?
- Respiratory alkalosis
- Decreases CBF
- Decreases pulmonary vascular resistance
(Good thing unless congenital defect) - Potassium shifts to the intracellular space
- Blunts normal urge to breathe
What are physiologic causes of decreased ETCO2?
- Hypothermia
- Pulmonary hypoperfusion (PE)
- Cardiac arrest
- Hemorrhage
- Hypotension
- Hyperventilation
What are equipment malfunctions that would cause decrease in ETCO2?
- Ventilator disconnect
- Esophageal intubation
- Airway obstruction
- Poor sampling
- ETT cuff leak
What are physiologic causes of increased ETCO2?
- Increased metabolic rate
- Fever
- Sepsis
- Seizures
- Thyrotoxicosis
- Increased cardiac output
- Bicarbonate administration
- Hypoventilation
- COPD
What malfunctions in equipment would cause increase in ETCO2?
- Rebreathing
- Exhausted CO2 absorber (same as dessicated)
- Leak in ventilator circuit
- Faulty inspiratory/expiratory valves
What is the normal difference in PaCO2 and ETCO2?
5mmHg (EX: arterial 40mmHg, ETCO2 35mmHg)
What problems can change the difference between PaCO2 and ETCO2?
- VQ mismatching increases difference (PE, Endobronchial intubation)
- Breathing patterns that don’t deliver alveolar gas to sampling line (COPD, bronchospasm)
- Capnograph problems (sampling leaks, slow sampling response time)
How does the chemical indicator work to measure if ETT is tracheal?
- Color change of litmus paper
- purple= no CO2
- Yellow- CO2
How do IR light absorption detectors measure CO2?
The greater the CO2 in the sample the less IR light reaches the detector
What are monitor requirements for capnography machines?
- CO2 reading +/- 12% of actual value
- Manufacturers must disclose interference cause by ethanol, acetone, halogenated volatiles
- Must have high CO2 alarm for inhales and exhales CO2
- Must have alarm for low exhales CO2
What are the phases of a normal capnograph?
- Phase 1: inspiration ends; lungs recoil; gas in circuit and anatomic dead space exits
- Phase 2:CO2 rich alveolar gas; normally steep
- Alpha angle: emptying of the alveoli and transition to dead space; normally 100-110 degrees
- Phase 3: Uneven emptying of last alveoli; slope should rise gently; Greater slope with airflow obstruction
- Beta Angle: 90 degrees; begins inspiratory phase; angle increases with inspiratory valve malfunction or rebreathing
- Phase 0: inspiration; CO2 falls abruptly to zero
What part of the capnograph is ETCO2 measured?
B angle
What is happening in the capnograph?
Normal- Every time you inhale CO2 return back to 0
What might be happening with this capnograph?
Inadequate seal→ LMA not in place, ETT cuff leaking, something in circuit is loose
Increased ETCO2→ hypoventilation, insufflation of abd
need to increase minute volume to blow off CO2 (increase Vt or RR)
What might be happening with this capnograph?
Hyperventilation ETCO2 decreasing
What might be happening with this capnograph?
Esophageal intubation→ could be severe laryngospasm if you 100% went through cords
use laryngoscope to check where you are at (likely esophageal)
What might be happening with this capnograph?
Early loss of paralysis→ little depression is a small inspiration occurring because part of muscle relaxer has worn off (can redose paralytic of give narcotic depending on whats going on with the surgery time frame)
What might be happening with this capnograph?
Pt overbreathing→ either give more paralytic/narcotic so the pt stops overbreathing OR decrease vent and let the patient have more spontaneous breaths less mandatory breaths
