Respiratory pathophysiology Flashcards
Are there sympathetic nerve endings in airway smooth muscle?
No, but beta -2 receptors are well represented.
What are the beta-2 receptors in the airway smooth muscle activated by?
catecholamines circulating in the systemic circulation
The beta -2 receptors in the airway smooth muscle is coupled to what proteins?
Gs protein
activation of the B2 receptors turns on the Gs protein, and this activates what?
adenylate cyclase
what does adenylate cyclase activate?
cAMP
What type of messenger is cAMP?
2nd messenger
along with protein kinase A, cAMP reduces what?
Ca+2 release from the sarcoplasmic reticulum
What does a reduction in Ca+2 from the SR ultimately cause?
reduction in muscle contraction and promotion of bronchodilation
when is the bronchodilation pathway by catecholamines turned off?
when phosphodiesterase 3 deactivates cAMP by converting it to AMP
What does NO do to smooth muscle?
it is a potent smooth muscle relaxant
Phospholipase C
Leukotrienes
Inositol triphosphate
These are all chemicals that do what to the airway?
increased airway resistance
Beta 2 agonists MOA?
B2 stimulation which increases cAMP and causes a decrease in Ca+2 (leading to bronchodilation)
name some Beta 2 agonists?
albuterol
salmeterol
metaproterenol
Anticholinergics MOA?
M3 antagonism leading to decreased IP3 which causes decreased Ca+2 (bronchodilation)
Name some anticholinergics?
atropine
glycopyrrolate
ipratropium
Corticosteroids (inhaled) MOA?
stimulates intracellular steroid receptors and regulates inflammatory protein synthesis which causes a decrease in airway inflammation and a decrease in airway hyper responsiveness
Cromolyn MOA?
Stabilizes mast cell membranes which decreases mediator release and provides prophylaxis for 1-2 hours
Leukotriene Modifiers MOA?
Inhibits 5 lipoxygenase enzyme which decreases leukotriene synthesis
Examples of Leukotriene modifiers?
zileuton
Montelukast
pranlukast
zafirlukast
Methylaxanthines MOA?
Inhibits phosphodiesterase leading to a decrease in cAMP
Releases endogenous catecholamines
Inhibits adenosine receptors
What volumes do pulmonary function tests measure?
static lung volumes
dynamic lung volumes
diffusing capacity
What is static lung volume?
how much the air the lungs can hold at a single point in time
what is dynamic lung volumes?
how quickly air can be moved in and out of the lungs over time
what is diffusing capacity?
How well the lungs can transfer gas across the alveolocapillary membrane
What are the static lung volumes?
How much air the lungs can hold at a single point in time
TLC FRC IRV ERV RV IC Vt VC
Which lung volumes provide an assessment of airway resistance and lung recoil?
dynamic lung volumes
What is FEV1?
Forced expiratory volume in 1 second.
volume of air that can be exhaled in one second.
What is the normal value for FEV1
> 80% predicted value
Which dynamic lung volumes are effort dependent?
FEV1
FVC
This dynamic volume takes age into account and it declines with age?
FEV1
What is forced vital capacity (FVC)?
Volume of air that can be exhaled after a deep inhalation
What is the normal value of FVC for male and female?
Male = 4.8 L Female = 3.7 L
What is the normal value of FEVI to FVC?
75 - 80%
Which dynamic volume measures airflow in the middle of expiration?
Forced expiratory flow at 25-75% vital capacity
Which pulmonary function test is the best test of airflow in the small airways?
Forced expiratory flow at 25-75% vital capacity
What is a normal value for forced expiratory flow at 25-75% vital capacity?
100 +/- 25% predicted value
What is Maximum voluntary ventilation (MVV)?
Maximum amount of air that can be inhaled and exhaled over 1 minute
which pulmonary function test is the best test of endurance?
MVV
What is the normal value of MVV for males and females?
Males = 140-180 L Females = 80-120 L
What is the abbreviation for Diffusing capacity for carbon monoxide?
DLCO or Dlco
Which test tests the lung’s ability to exchange gas?
Diffusing capacity for carbon monoxide test
Volume of carbon monoxide that can transverse the aleveolarcapillary membrane per a given alveolar partial pressure of CO describes?
Diffusing capacity for carbon monoxide
What do flow volume loops allow you to do?
differentiate between obstructive and restrictive respiratory disease
On a flow-volume loop between what two points does inhalation occur?
inhalation occurs between residual volume and lung capacity
on a flow volume loop where is flow zero?
flow is zero at the line that traverses the loop which is also at end inspiration.
When does flow occur on a flow volume loop?
flow occurs at inspiration and expiration
on a flow volume loop in what direction does volume become more positive?
volume becomes more positive from right to left
Why does the flow volume loop never get to zero?
Residual volume is greater than zero, so the loop never gets to zero (the x axis)
What is the max volume the lungs can hold on the flow volume loop (and real life)?
Total lung capacity
What lung volume represents the width of the flow volume loop (x axis)
Vital capacity
Factors that have NOT been shown to increase the risk of postoperative pulmonary complications for non thoracic surgery are? (3)
mild / moderate asthma
arterial blood gas analysis
pulmonary function testing
What are the is the best way to reverse anesthesia induced atelectasis?
Alveolar recruitment maneuvers (ARM’s)
This includes increasing peak airway pressure to 30 cm H20 for initial reopening, and increasing the PIP to 40 cm H20 for eight seconds which appears to reverse anesthesia-induced atelectasis almost completely
Does the application of PEEP reverse atelectasis?
Yes, but only partially
When should you apply PEEP to reverse atelectasis?
only after ARM have been used in an effort to prevent open airways from collapsing again, then apply PEEP
What can help prevent atelectasis that is not ARM or PEEP?
Mixing air with oxygen also helps prevent atelectasis
Lower than normal values for DLCO tell you what?
lower values correlate with a significant reduction in diffusing capacity
Does asthma affect tests of gas exchange such as DLCO?
NO, asthma affects airway diameter, but not alveolocapillary interface itself. This would affect tests of pulmonary mechanics (FEV1, MMF, etc), but not DLCO.
Explain the pathophysiology of chronic bronchitis?
Caused by inflammation and mucus production that reduces airway diameter
Explain the pathophysiology of emphysema?
caused by a reduction in the surface area of the alveolocapillary interface and loss of elastic recoil
Who are the pink puffers?
patient with emphysema
Who are the blue bloaters?
patient with chronic bronchitis
Tell me about the blood gases/labs of a person with chronic bronchitis?
Chronically low Pa02
They tend to retain CO2
They have polycythemia as their RBC have increased to try and compensate for the chronically low PaCO2
Tell me about the blood gases/labs of a person with emphysema?
Generally has a normal (or slightly reduced) Pa02. The PaCO2 is usually normal or decreased due to hyperventilation.
As a result of pulmonary hypertension the patient with chronic bronchitis may have this complication?
Cor Pulmonale
If a patient has Cor pulmonale then you want to avoid any anesthetic management that would increase PVR, this would include avoiding what?
hypoxia
acidosis
hypercarbia (any drug that causes respiratory depression can cause hypercarbia)
hypothermia
nitrous oxide
vasoconstrictors
conditions that increase SNS tone
ketamine (maybe)
If you have a fixed PVR what can cause profound hypotension?
A decrease in SVR
Cor pulmonale is right sided heart failure that results from pulmonary hypertension. This creates a back pressure on the venous circulation that leads to?
jugular venous distension
hepatomegaly
lower extremity edema
Is increased PAOP consistent with RV failure?
NO, it is consistent with LV failure
If an area is ventilated but not perfused this increases what?
dead space
If an area is perfused but not ventilated this increases what?
shunt
If a patient has a pulmonary embolism will their EtCO2 increase or decrease?
Decrease (because it is diluted from a mixture of gas from perfused alveoli and alveoli lacking perfusion)
Why do you apply positive end-expiratory pressure for a patient who has just aspirated gastric contents?
Atelectasis increases pulmonary shunt, PEEP is indicated to reduce shunt
(hypoxemia is the hallmark sign of aspiration pneumonitis)
What drug reduces free radical production, inhibits neutrophil chemotaxis, minimizes reperfusion injury, and improves outcomes in patients with aspiration pneumonitis?
Lidocaine
What is the best ventilatory strategy for restrictive lung diseases?
You want to reduce the risk of barotrauma, you accomplish this with small tidal volumes (6ml/kg IBW) and faster respiratory rate (14-18).
Maintain PIP of less than 30 cm H20.
What are the five causes of hypoxemia?
high altitude hypoventilation diffusion defect V/Q mismatch Right to left shunt
High-altitude:
A-a gradient?
02 helpful?
Examples?
Normal
Yes
low barometric pressure
Hypoventilation:
A-a gradient?
02 helpful?
Examples?
normal
yes
low PA02, opioid overdose
Diffusion defect:
A-a gradient?
02 helpful?
Examples?
Increased
Yes
Pulmonary fibrosis,
V/Q mismatch:
A-a gradient?
02 helpful?
Examples?
increased
yes
dead space, shunt
Right to left shunt:
A-a gradient?
02 helpful?
Examples?
increased
no (if shunt > apprx. 30%)
VSD, TOF, Eisenmenger syndrome
Negative pressure pulmonary edema is an example of which type of restrictive lung dz?
acute intrinsic
example of chronic intrinsic restrictive lung dz?
pulmonary fibrosis
What percentage of cisatracurium and atracurium are metabolized by Hofmann elimination?
100% of Nimbex
33% atracurium
What effect does acidosis have on NMB?
Acidosis impairs the ability of the body’s enzymatic systems to function properly.
Acidosis perpetuates NMB and decreases the efficacy of anticholinesterase.
Hypoxemia during OLV is the result of what?
intrapulmonary shunt
Strategies for reversing hypoxemia during OLV?
Increase FI02 100%
Check DLT position with FOB
Apply CPAP 10 H20 to the non-dependent lung
Apply PEEP 5-10 cm H20 to the dependent lung
Ligate or clamp the pulmonary artery or the non-dependent lung (not always possible)
Resume two-lung ventilation
EtCO2 capnography is typically a reliable indicator of Tracheal intubation but what times can it give you a false-negative result?
cardiac arrest
severe bronchospasm
complete ETT obstruction
equipment malfunction
