Exam 1 Capnography (6/11/24) Flashcards
What are the effects of hypercarbia?
- Respiratory Acidosis
- ↑ CBF
- ↑ PVR
- K⁺ shift intravascularly
What are the effects of hypocarbia?
- Respiratory alkalosis
- ↓ CBF
- ↓ PVR
- K⁺ shift intracellulary
- Blunts respiratory drive
What is the Bohr equation?
What is it used for?
Used to calculate physiologic dead space
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
This is the Measurement and quantification of inhaled or exhaled CO2 concentrations:
Capnometry
What is the best method to confirm endotracheal tube placement?
Capnography
Differentiate high-speed (real-time) and low speed (trend capnography).
High-speed – user can interpret information about each breath
Slow-speed – appreciation of the expired and inspired trend
How much gas do side-stream analyzers utilize?
50-200 mL/min sample rate
What is the most common method for capnographic sampling, side-stream or main-stream sampling?
Side-stream
Which type of sampling analyzes the gas sample directly in the breathing circuit?
Main-Stream
What are the benefits of main-stream sampling?
- No time delay
- quicker rise time
At what “Phase” do we measure ETCO2?
End-point of phase 3
Why might the patient’s Phase 1 not be 0mmHg?
Rebreathing CO2
Increased or Decreased ETCO2?
Hypothermia
Hypotension
Bicarb Administration
Hemorrhage
Sepsis
CPR
Cardiac Arrest
Seizures
Hypothermia: Decreased
Hypotension: Decreased
Bicarb Administration: Increased
Hemorrhage: Decreased
Sepsis: Increased
CPR: Increased
Cardiac Arrest: Decreased
Seizures: Increased
What approximate difference is there between PaCO₂ and EtCO₂ ?
5 mmHg
ex. PaCO₂ will be 40 mmHg vs EtCO₂ at 35 mmHg
True or False:
The greater the CO2 in the sample, the more IR light that reaches the detector?
False:
The greater the CO2 in the sample, the LESS IR light that reaches the detector
What color is the CO₂ chemical indicator?
What color does it change to in the presence of CO₂ ?
purple → yellow
When using a capnograph, how close must a CO₂ reading be to the actual value?
+/- 12%
What are the inspiratory phases of the capnograph?
Phase 0
What are the expiratory phases of the capnograph?
Phases I, II, and III
When would the CO₂ reading of a capnograph be 0 mmHg ?
Phase I
Which phase of the capnograph represents the beginning of expiration?
Phase II
What is a phase IV in the capnograph? Why does it occur?
Upstroke at the end of Phase III resulting from collapse of alveoli.
What patient populations might exhibit a Phase IV on their capnograph?
Why?
- Obese
- Pregnant
Decreased FRC and TLC
What phases are separated by the β angle?
Phase III and 0
What degree should the α angle have?
What occurs with increase to the angle’s degree?
- 100 - 110°
- Increased angle occurs with expiratory airflow obstruction (COPD, ETT, bronchospasm, etc)
What degree should the β angle have?
90°
What situations/conditions would cause an increase in the β angle?
- Bad inspiratory valve
- Rebreathing
- Low VT w/ tachypnea
What type of capnograph is depicted below?
Mechanical Ventilation
What type of capnograph is depicted below?
Spontaneous Ventilation
What is occurring with the capnograph below?
Inadequate ETT seal
What might be occurring based on the two capnographs below?
Faulty Inspiratory Valve
What is occurring with the capnograph below?
Sample line leak
What is occurring with the capnograph below?
Hyperventilation (resulting in a ↓ EtCO₂)
What is occurring with the capnograph below?
Hypoventilation (resulting in steady ↑ EtCO₂)
What is occurring with the capnograph below?
Airway obstruction or breathing circuit obstruction
What is occurring with the capnograph below?
Cardiac oscillations
What is occurring with the capnograph below?
Rebreathing (note the increasing baseline)
What is occurring with the capnograph below?
Curare Cleft (NMBDs are wearing off)
What is occurring with the capnograph below?
Ventilator overbreathing
What is occurring with the capnograph below?
Esophageal Intubation (You tubed the goose ya dummy)
