Exam 1 Capnography (6/11/24) Flashcards
(41 cards)
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
