Exam 1 Capnography [6/11/24] Flashcards
- What is the importance of capnography?
- Who is it required in?
- Standard monitor by AANA/ASA, required for every patient under anesthesia
Provides information regarding:
* Ventilation
* Metabolism
* Cardiovascular
S2
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
S3
What are the effects of hypocarbia?
- Respiratory alkalosis
- Decreases CBF
- Decreases pulmonary vascular resistance
- Potassium shifts to the intracellular space
- Blunts normal urge to breathe
S4
Capnography provides inforomation primarily on ventilation but also on?
- Pulmonary blood flow
- Aerobic metabolism
- Placement of ETT/LMA
- Integrity of breathing circuit
- Estimates the adequacy of cardiac output
S5
capnography is PAPIE
What does the bohr equation calculate?
- Calculates physiological dead space
S5
Volume of each breath inhaled that does not participate in gas exchange is?
Dead space
S6
Conducting zones of the airway (nose, trachea, bronchi) is what type of deadspace?
Anatomical deadspace
S6
airway dead space + alveolar dead space =
Physiological deadspace
S6
Portion of the physiologic dead space that does not take part in gas exchange but is within the alveolar space
Alveolar dead space
S6
What are the conditions that increase alveolar dead space (V/Q mismatching)
- Hypovolemia
- Pulmonary hypotension
- Pulmonary embolus
- Ventilation of nonvascular airspace
- Obstruction of precapillary pulmonary vessels
- Obstruction of the pulmonary circulation by external forces
- Overdistension of the alveoli
S6
What is Capnometry?
How is it measured?
- Measurement and quantification of inhaled or exhaled CO2 concentrations
- Measured by a capnometer
S7
What is capnography?
- Method of CO2 measurement and a graphic display over time
- Detection of CO2 breath-by-breath
- Best method to confirm endotracheal intubation
S7
Time capnography
- Gas Pressure vs time plot; most common representation
- CO2 concentrations digitally reported as ‘inspired’ and ‘end tidal’
S8
What does the term high speed vs slow speed mean?
- High-speed – user can interpret information about each breath
- Slow-speed – appreciation of the expired and inspired trend
S8
- This is the most common gas sampling system. It aspirates gas sample and analyzes away from airway at a rate of 50 to 200 ml/min.
- This can cause a delay in what?
- Side-stream gas analyzer
- Transport time delay and rise time
S10
- this gas sampling system analyzes gas sample directly in the breathing circuit
- does it cause delay in transport time or rise time?
- main stream
- No time delay; rise time is faster
S10
What phase on a capnograph will an ETCO2 be measured at?
- ETCO2 measured at the end-point of phase 3.
- Sometimes varies with manufacturers [Value just before inspiration, Largest value, The average at a specific time]
S11
What can increase ETCO2?
- increased CO2 production and delivery to the lungs
- decreased alveolar ventilation
- equipment malfunction
S12
What are examples of increased CO2 production that causes increased ETCO2?
- increased metabolic rate
- fever
- sepsis
- seizures
- MH
- thryotoxicosis
- increased CO2 [during CPR]
- bicarb administration
S12
What are examples of decreased alveolar ventilation that causes increased ETCO2?
- hypoventilation
- respiratory center depression
- partial muscle paralysis
- neuromuscular disease
- high spinal anesthesia
- COPD
slide 12
What is causing this capnograph?
- Esophageal intubation
S35
What can decrease ETCO2?
- decreased CO2 production and delivery to the lungs
- increased alveolar ventilation
- equipment malfunction
S13
What are the inspiratory and expiratory segments of a normal capnograph?
- Inspiratory – Phase 0
- Expiratory – Phases I, II, and III
S18
Describe Phase I of a normal capnograph.
- Baseline
- Exhalation of anatomic dead space and the apparatus (ETT, LMA)
- Essentially no CO2
- 1/3 of tidal volume is exhaled
S20
Describe Phase II of a normal capnograph.
- Expiratory upstroke begins (CO2-rich alveolar gas)
- Sampling of alveolar gases
- Normally steep uprise
S20
Describe Phase III of a normal capnograph.
- Alveolar Plateau phase
- Normally representative of CO2 in alveolus
- Can be representative of ventilation heterogeneity, slightly increasing slope
S21
Describe Phase 0 of a normal capnograph.
- Sometimes called phase IV
- Inspiration of fresh gas, remaining CO2 washed out
- Downstroke returns to baseline
S21
Describe the Occasional Phase IV (Phase IV Prime) of a capnograph.
- A sharp upstroke in PCO2 at the very end of phase III
- Upstroke probably results from the closure of lung units with lower PCO2
- Allows for regions with higher CO2 to contribute to more of the exhaled gas sample
- Seen in pregnant and obese pts d/t Decreased FRC and lung capacity
S22
Describe the alpha angle of the capnograph.
- Separates phase II and phase III
- 100 – 110 degrees
- Angle increases with an expiratory airflow obstruction
- Ex: COPD, bronchospasm, or kinked ETT
S23
Describe the beta angle of the capnograph.
- Separates phase III and phase 0
- 90 degrees
- Angle increases with malfunctioning inspiratory unidirectional valves, rebreathing, and low tidal volume with rapid respiratory rate
S23
Describe the capnograph
- Normal Capnograph
- Mechanical Ventilation
S24
Describe the capnograph
- Normal Capnograph
- Spontaneous Ventilation
S24
What is the issue with this capnograph?
- Inadequate Seal around ETT
Additional:
* beta angle is widened
* P3 is cut short bc whatever is going out is leaving around the ETT too.
S25
What is causing this capnograph?
- H: faulty inspiratory valve, resulting in a slower downslope, which extends into the inhalation phase (phase 0) as CO2 in the inspiratory limb is rebreathed
- J: faulty inspiratory valve.
S26
Miller pg 1311
What is causing this capnograph?
- Sample line leak
Take note that this a small wave form and that ETCO2 does not even reach 40 mmHg
S27
Miller: dual plateau in phase III, suggesting the presence of a leak in a sidestream sample line. Early portion of phase III abnormally low due to dilution of exhaled gas with ambient air. The sharp increase in CO2 at the end of phase III reflects a diminished leak resulting from the increased circuit pressure at the onset of inspiration
What is causing this capnograph?
- Hyperventilation
- Gradually decreasing waveforms
S28
What is causing this capnograph?
- Hypoventilation
- Gradually increasing waveforms
S29
What is causing this capnograph?
- Airway obstruction
Additional:
* Shark Fin
* Alpha angle: Basically gone
* P2 & P3 are basically one.
S30
Miller: increased upslope of phase III, as may occur during bronchospasm (asthma, chronic obstructive pulmonary disease), or partially obstructed endotracheal tube/breathing circuit
What is causing this capnograph?
- Cardiac oscillation
- Often seen in pediatric patients, the heart is close to the trachea
S31
Millers Definition: cardiogenic oscillations at the end of exhalation as flow decreases to zero and the beating heart causes emptying of different lung regions and back-and-forth motion between exhaled and fresh gas;
What is causing this capnograph?
- Re-breathing soda lime exhaustion
Take note that rebreathing is occurring. The capnograph does not return to baseline.
S32
Millers: rebreathing of CO2, as may occur with faulty expiratory valve or exhausted absorber system
What is causing this capnograph?
- NMBD’s wearing off
- Presence of a “curare cleft”
S33
What is causing this capnograph?
- Over-breathing
- Notice the spontaneous breath between the mechanical breath
S34
