capnography Flashcards
what are the 4 effects of hypercarbia
respiratory acidosis
increased CBF (inc ICP)
increase pulmonary vascular resistance
potassium shifts from intracellular to intravascular
5 effects of hypocarbia
respiratory alkalosis
decreased CBF
decrease pulmonary vascular resistance
potassium shifts to the intracellular space
blunts normal urge to breath
besides providing information on ventilation capnography can also provide information on
pulmonary blood flow
aerobic metabolism
placement of tube
integrity of breathing circuit
estimates the adequacy of cardiac output
what does the bohr equation calculate
physiological dead space
what is dead space
volume of each breath inhaled that does not participate in gas exchange
what is anatomic dead space
conducting zone of the airway
Nose, trachea, bronchi
what is physiologic dead space
airway deadspace and alveolar dead space
high speed time capnography
user can interpret information about each breath
slow speed time capnography
appreciation of the expired and inspired trend
what is side stream
aspirated gas sample and analyzes away from airway at a rate of 50-200mL/min
what is mainstream
analyzes gas sample directly in the breathing circuit
no time delay; rise time is faster
where is end tidal CO2 measured during the waveform
end point of phase III
causes of increased PetCO2; increase CO2 production and delivery to the lungs
increased metabolic rate
fever
sepsis
seizures
malignant hyperthermia
thyrotixicosis
increased CO (due to CPR)
bicarb administration
increased PetCO2; decrease alveolar ventilation
hypoventilation
respiratory center depression
partial muscular paralysis
neuromuscular disease
high spinal anesthesia
COPD
increased PetCO2; equipment malfunction
rebreathing
exhausted CO2 absorber
faulty inspiratory expiratory valve
decrease PetCo2; decrease CO2 production and delivery to the lungs
hypothermia
pulmonary hypo perfusion
cardiac arrest
pulmonary embolism
hemorrhage
hypotension
decreased PetCO2; increase alveolar ventilation
hyperventilation
decrease PetCO2; equipment malfunction
ventilator disconnect
esophageal intubation
complete airway obstruction
poor sampling
leak around endotracheal tube cuff
what is the difference between PaCO2 and ETCO2
5mmHg
3 problem the increase the difference of PaCO2 and ETCO2
V/Q mismatching (PE, endobronchial intubation)
breathing patterns that fail to deliver alveolar gas at the sampling site (neonates, COPD, bronchospasm)
problems with the capnograph (sampling line leak, calibration error, slow response time relative to breathing pattern)
Clinical measurement most commonly relies on
IR light absorption techniques
the greater the CO2 in the sample the _______ IR light that reaches the detector
less
with the chemical indicator, purple color change indicates
Yellow?
no CO2- purple
CO2 - yellow
Phase 1 of the capnograph
baseline
exhalation of anatomical DS and the apparatus
NO CO2
phase 2 capnograph
expiratory upstroke begins, CO2 rich alveolar gas
sampling of alveolar gases
normally steep
phase 3 capnograph
plateau phase
normally representative of CO2 in alveolus
can be representative of ventilation heterogeneity, slight increasing slope
phase 0 capnography
also called phase IV
inspiration of fresh gas remaining CO2 washed out
downstroke returns to baseline
what happens in the occasional phase IV
sharp upstroke in PCO2 at the very end of phase III
results from 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 patients with decreased FRC and lung capacity
alpha angle separates_____?
what is the angle?
when will increase?
separates phase II and III
100-110 degrees
increases with expiratory airflow obstruction (COPD, bronchospasm, kinked ETT)
beta angle separates?
degree?
increases with?
separates phase III and 0
90 degrees
malfunctioning inspiratory unidirectional valves, rebreathing and low tidal volume with rapid respiratory rate
mechanical ventilation
spontaneous ventilation
inadequate seal
faulty inspiratory valve
sample line leak
hyperventilation
hypoventilation
airway obstruction
cardiac oscillations
NMBD wearing off
rebreathing soda lime exhaustion
over breathing
esophageal intubation
