Test 2: 20 +21 Flashcards
respiratory arrest happen at — MAC
2-3 x increase
MAC at 1=
50% of patients will be properaly anesthetized
resp arrest at 2-3 MAC
cardiac arrest at 4-5 MAC
— coordinates the transition between inhalation and exhalation; it also prevents overinflation of the lungs by always sending inhibitory impulses to the inspiratory center
pneumotaxic center
the pneumotaxic center prevents — of the lungs by always sending — impulses to the inspiratory center
overinflation
inhibitory
— coordinates the transition between inhalation and exhalation by fine-tuning the medullary respiratory centers; does this by sending — impulses to the inspiratory center which result in a slower, deeper inhalation; this is necessary when you choose to —
apneustic center
stimulatory
hold your breath
two major centers of the pons
pneumotaxic center: this is the regulator; it coordinates the transition between inhalation and exhalation; it also prevents overinflation of the lungs by always sending inhibitory impulses to the inspiratory center
apneustic center: coordinates the transition between inhalation and exhalation by fine-tuning the medullary respiratory centers; does this by sending stimulatory impulses to the inspiratory center which result in a slower, deeper inhalation; this is necessary when you choose to hold your breath
what groups are in the medullary respiratory center
Dorsal respiratory group
ventral respiratory group
ventral respiratory group does
only activated when demand is high and is involved in forced inspiration and expiration.
medullary respiratory center: dorsal and ventral respiratory groups →control the phrenic nerve and the intercostal nerves.
Dorsal respiratory group does
responsible for stimulating inhalation, thought to set by basic rhythm “pacemaking” and exciting the inspiratory muscles
medullary respiratory center: dorsal and ventral respiratory groups →control the phrenic nerve and the intercostal nerves.
—: dorsal and ventral respiratory groups →control the phrenic nerve and the intercostal nerves.
medullary respiratory center
If anesthesia impairs the ventilator centers and the ventilation, this can lead to a — in oxygen uptake and an — of CO2 due to reduced exhalation
reduction
accumulation
CO2 and O2 receptors in the aorta trigger signal to the — that cause —
↑CO2 causes decrease in pH of blood
brain (pons and medulla)
triggers signal to the diaphragm and intercostal muscle to contract and inhale
reduced oxygen uptake can cause
hypoxemia
hypoxia
reduced CO2 exhalation will cause what
acid base disturbances → ↑CO2 will cause ↓ in pH of blood (respiratory acidosis)
central damping
how to calculate minute ventilation
tidal volume x RR
during anesthesia tidal volume may decrease and RR will increase to compensate
The most accurate way of measuring respiratory volumes is using a —.
spirometer
what is a spirometer
This is an apparatus for measuring the volume of air inspired and expired by the lungs
most accurate way of measuring respiratory volumes
rarely used in hospital setting
in general tidal volume equation
10 ml/kg
10x (30 kg dog)= 300 ml tidal volume
average bag size for animal
weight in kg/10
10 kg pt/10= 1 L bag
bags only go up to 30L used for horses >500kg
pitot tube
spirometer: measures the volume of air inspired and expired by the lungs by measuring the pressure gradient
wrights spirometer
spirometer: measures the volume of expired air by the lungs by counting spins
ETCO2 is a measure of
expiratory CO2 concentration which is an indicator for the arterial CO2 concentration
capnography measures
expiratory CO2 concentration which is an indicator for arterial CO2 concentration
Science behind capnography
Capnographs usually work on the principle that CO2 absorbs infrared radiation. A beam of infrared light is passed across the gas sample to fall on a sensor. The presence of CO2 in the gas leads to a reduction in the amount of light falling on the sensor, which changes the voltage in a circuit. The analysis is rapid and accurate.
measure expiratory CO2 concentration
main stream vs side stream capnography
main stream: directly from the airway, very accurate, breaks easily, $$, human sized
side stream: analysis done away from pt, delay (12-15sec), only sample small amount of air- not as accurate
measure CO2 levels
The ETCO2 should be maintained between — mmHg.
35 and 45
An ETCO2 — mmHg is considered hyperventilation and an ETCO2 — mmHg is considered hypoventilation
below 30
greater 60
should be kept 35-45 mmHg
capnography but pt breathing
tube in esophagus
need to take out and reintubate
slow inspiration with cardiogenic ripples
very light animals-
slow RR
high muscle tone
pumping of heart pushes on lungs and cause tiny exhales of CO2
leak
valve defect
water in system
CO2 rebreathing
CO2 scrubber (sodalime) not working- old- needs to be replaced
very slow exhale- do not get to platuea before pt inhales
Obstruction (Tube, Bronchus)
lung not well profused, getting less O2= less CO2 transfer
cardiac arrest
Hypoventilation leading to — ETCO2-values is relatively common during general anesthesia because of the respiratory depressant effects of most anesthetics.
high (>60mmHg)
Positive effects of hypoventilation induced — are stimulation of ventilation through both central and peripheral chemoreceptors, stimulation of the sympathetic nervous system resulting in an — in heart rate and blood pressure, and peripheral — by direct effect on vessels.
hypercapnia
increase
vasodilation
severe hypercapnia can lead to cerebral — increasing cerebral blood flow and intracranial pressure (only a problem with patients with high ICP) but also to central depression at very — levels of PaCO2 leading to prolong and unpredictable recovery periods.
vasodilation
high
The best and most accurate way of assessing ventilation
blood gas analysis
arterial partial pressure of carbon dioxide (PaCO2)
can only use a few times, need bigger pt, can be expensive to test
E TCO2 < 30 mmHg means
Hyperventilation
* Rare under anesthesia when spontaneously ventilating
* Uncommon, but feasible when mechanically ventilating
Low cardiac output
* Decrease in CO2 production
* Decrease in blood flow
E TCO2 > 60 mmHg is caused by
Hypoventilation
* Very common with inhalant anesthetic
need to mechanically or hand ventilate pt
why do you need to address hypercapnea
- can cause acid-base imbalance (↑CO2= ↓ph)
- high levels can effect mental status (central depression)
- can cause hypoxemia, too much CO2 in alveoli →no room for O2 to come in
- ↑ SYM= ↑HR and HTN
- peripheral vasodilation
- cerebral vasodilation → ↑ ICP
3 ways to assess ventilation
count RR and estimate tidal volume to calculate minute ventilation
capnography- EtCO2
arterial blood gas- PaCO2
cardiac output is — to the respiratory ventilation
=
blood comes in at a rate = to the rate of gas exchange in the lungs
