Apex- Respiratory Pathophys Flashcards
Chemicals that contribute to increased airway resistance (select 3):
- nitric oxide
- inositol tirphosphate
- vasoactive intestinal peptide
- phospholiapase C
- leukotrienes
- cyclic AMP
- inositol triphosphate
- phospholiapse C
- leukotrienes
Bronchoconstriction is mediated by what 2 things?
What about bronchodilation?
Bronchoconstriction:
1. PNS:
- CNX >ACH > muscarinic-3 receptor (GQ > phospholipase C > IP3 >CA+ release from SR> Myosin light-chain kinase activation> contraction)
2. The immune response:
- Histamine, leukotrienes, mast cells, ect
Bronchodilation:
1. Circulating catecholamines
- Epi, NE > B2 receptor (GS) > activates adenylate cyclase > cAMP (2nd mes) > DECREASED release of CA+ from SR > bronchodilation
2. VIP receptor (nitric oxide pathway)
- Nitric oxide - potent smooth muscle relaxant
- non-cholinergic PNS nerves release VIP (Vasoactive intestinal peptide) onto airway smooth muscle > increase NO > activates cGMP > smooth muscle relaxation and bronchodilation.
What turns off the adenylate cyclase > cAMP > decreased CA+ release from SR > bronchodilation pathway?
How?
PDE III
*deactivates cAMP by converting it to AMP
What cranial nerve supplies parasympathetic innervation to the airway smooth muscle?
With all other things being equal, what part of the airway has the most significant contribution to airflow resistance?
Radius
(R^4)
T/F: there are NO sympathetic nerve endings in the airway smooth muscle
True
Instead, B2 receptors embedded in the airway smooth muscle are activated by catecholamines in the systemic circulation (ok?)
Match the drug with it’s corresponding drug glass
- Theophylline:
- Zafirlukast:
- Cromolyn:
- Triamcinolone:
Corticosteroid, Leukotriene modifier, Methylxanthine, Mast cell stabilizer
- Theophylline: Methylxanthine
- Zafirlukast: Leukotriene modifier
- Cromolyn: Mast Cell stabilizer
- Triamcinolone: Corticosteroid
2 anesthetic agents with bronchodilating properties
volatile anesthetics and ketamine
Pulmonary medications can be broken down into what 3 classes?
- Direct acting Bronchodilators
-
Beta 2 agonists = albuterol, metaproterenol, salmeterol
- B2 stimulation → increased cAMP → decreased CA+
-
Anticholinergics = atropine, glycopyrrolate, ipratropium
- M3 antagonism = decreased IP3 → decreased CA+
- Anti-inflammatories
-
Inhaled corticosteroids: beclomethasone, fluticasone, triamcinolone
- Stimulates intracellular steroid receptors
- Regulates inflammatory protein synthesis
- Stimulates intracellular steroid receptors
-
Cromolyn
- Mast cell stabilizer → decreased release of mediators
-
Leukotriene modifiers: zileuton, montelukast
- Inhibits 5-Lipoxygenase enzyme → decreased leukotriene synthesis
- Methylxanthines
- Theophylline
- Inhibits phosphodiesterase (PDE) (usually turns off cAMP pathway) → increased cAMP → increased release of endogenous catecholamines to stimulate B2
What PFT is the MOST sensitive indicator of small airway disease?
- Forced expiratory volume in 1 second
- Forced expiratory flow 25-75%
- Forced vital capacity
- diffusion capacity of carbon monixide (DLCO)
-Forced expiratory flow 25-75%
The average forced expiratory flow during the middle half of the FEV measurement.
Normal FEV 1
>80% of predicted value
Normal FEV1/FVC ratio value
>75-80% of the predicted value
What does FEV1 measure
the volume of air that can be exhaled after a maximal inhalation over 1 second
(>80% predicted volume)
What does Forced Vital Capacity (FVC) measure?
Normal volumes for males/females
The volume of air that can be exhaled after a maximal inhalation
Male= 4.8 L
Female = 3.7L
(can we just say 3.8 to make it easier?)
What does the FEV1 to FVC ratio compare?
What is it useful for
the volume of air expired in 1 second and the total volume of air expired
useful in diagnosing obstructive vs restrictive disease
Normal = 75-80% of predicted value
< 70% suggests obstructive disease (have a problem getting air out)
normal in restrictive disease (no problem getting air out, but problem getting it in, but the small amount they take in is the same amount they can exhale)
FEV1/FVC of < 70%
obstructive disease
What does Forced Expiratory Flow at 25-75% vital capacity measure?
(FEF25-75%)
how does it measure in obstructive vs restrictive disease?
Normal Value
AKA
Measures airflow in the middle of FEV
- reduced with obstructive disease (prob getting air out)
- normal with restrictive disease (no prob getting air out)
normal = 100 +/- 25% predicted value (whatever the hell that means)
AKA- Mid-Maximal Expiratory Flow Rate (MMEF)
What does the Maximum Voluntary Ventilation (MMV) Measure?
The maximum volume of air that can be inhaled and exhaled over the course of 1 minute
- Male = 140-180
- Female = 80-120
What is the best test of endurance?
Maximum Voluntary Ventilation (MMV)
max volume of air that can be inhaled and exhaled over the course of 1 minute
What does DLCO (diffusing capacity) measure?
How is it measured?
What law?
Normal Value?
the ability of the alveolocapillary membrane to exchange gas
- CO ususally used to measure this
- Ficks law
- normal value 17-25ml/min/mmHg
How does restrictive disease affect the FEV1/FVCC ratio?
It’s usually normal
What do flow-volume loops allow us to differentiate between?
obstructive and restrictive respiratory diseases
What’s ABC&D
A- Exhalation
B- Inhalation
C- Total Lung capacity
D- Residual volume
All of the following are independent ris kfactors for postop pulmonay complications EXCEPT:
- Age >65yo
- COPD
- CHF
- Asthma
Asthma
What 3 things alone are not shown to be indepedent predictors of postop pulm complications?
- Asthma
- PFTs/ABGs
- Obestiy
What are the 4 C’s and 4 S’s of risk of postop pulmonary complications?
Class 3 ASA
Cigg smoking
CHF
COPD
Sixty or older
Serum albumin <3.5 (malnutrition)
Surgery duration > 2.5 hours
Surgical site: uppder abd/thorax/peripheral vascular
Serum albumin less than what puts patient at risk for postop pulmnary complications?
< 3.5g/dL
How long should patients stop smoking before surgery?
6 weeks
What is the t 1/2 life of carbon monoxide?
4-6 hours
After you stop smoking, how long until P50 returns to normal?
12 hours
(reduction in carboxyhemoglobin > improved P50 [but does not reduce risk of postop pulm complications])
2 ways to reverse anesthesia-induced atelectasis
1. ARMs
*PIP to 40cm H20 for 8 seconds
2. Use the lowest FiO2 the patient will tolerate
(high FiO2 contributes to absorption atelectasis)
What blood test indicates a higher risk of postop pulmonary complications?
Serum Albumin < 3.5
A patient with severe kyphoscoliosis is expected to have a reduced: select 2:
- FEV1/FVC ratio
- FRC
- FEF 25%-75%
- FEV1
-FRC & FEV1
- restrictive lung disease - all volumes are decreased
- since TLC is smaller , there is less volume to exhale , so the FEV1/FVC ratio is usually unchanged (they can get out what they bring in) but the FEV1 will be decreased bc they are taking in decreased volumes
- the FEF 25-75% is sensitive to increased air flow resistance in the small airways; not a problem for those with restrictive lung disease
How does obstructive disease affect the following:
FEV1, FEV, FEV1/FVC ratio
FEV1 & FEV - normal or decreased
FEV1/FVC ratio always decreased (they cant get out what they brought in)
How are the following affected with restrictive disease:
FEV1, FVC, FEV1/FVC ratio
FEV1 and FVC are decreased (taking in and expiring small volumes bc they cant get air in)
FEV1/FVC ratio is NORMAL (they can exhale everything they take in)
T/F- Obstructive disease is characterised by small airway obstruction
True
Small airway obstruction & increased resistance to expiratory flow
Problem = getting air out
How is compliance in someone with restricitive disease?
decreased
Identify each
Blue = obstructive (icream cone, left shift)
- Someone took a bite of my icecream cone (COPD)
Red = fixed (rock)
- Someone smashed my icecream cone; it needs to be fixed
Green = Normal
Purple = Restrictive (narrow, shift right)
- On a restrictive diet, you’ll have to eat a smaller ice cream cone
What kind of obstructions do these loops represent
1. Extrathoracic
- pt inhales, airway colllapses, reduces flow being inhaled
- pt exhales and pushes the obstruction open; flow out is normal
- Inspiratory limb is flat in an Extrathoracic obstruction
2. Intrathoracic
- pt inhales, pulls open the obstruction; flow going in = normal
- pt exhales, airway collapses; flow going out = reduced
- Expiratory limb is flat in the Intrathoracic obstruction
A patient with astham expereinces bronchospasm immediately following tracheal intubation. This is most likely the result of:
- mast cell degranulation
- decreased sympathetic tone
- histamine release
- vagal stimulation
Vagal Stimulation
- Bronchospasm can be due to direct PNS stimulation OR consequence of an immune response (mast cell degranulation)
- intubation does not cause an immune response; however, it can activate vagal afferents leading to bronchospasm
What is defined by an acute, resversible airway obstruction that is accompanied by chronic airway inflammation and bronchial hyperreactivity?
Asthma
What is the greatest risk factor for developing asthma?
Atopy
-the condition of being “hyper-allergic”
What’s to be noted about FEV1, FEV1/FVC ratio, and FEF25-75% in the astmatic?
They are all reduced but will improve following bronchodilator therapy (asthma = reversible)
What is the most common ABG finding in the asthmatic and why?
What would suggest impending respiratory failure?
Resp. Alkalosis with hypocarbia
Hypercarbia would suggest impending respiratory failure due to air trapping and respiratory muscle fatigue
5 Histamine releasing agents that should be avoided in the asthmatic patient (mneumonic)
MMAST
Morphine
Meperidine
Atracurium
Sux
Thiopental
(mast cells implicated in immune response)
What might an EKG show during a severe asthma attack?
Right ventricular strain with right axis devation due to the increased pulm vasc resistance increasing the workload of the right heart
T/F: during an asthma attack, tachypnea and hyperventilation are the result of hypoxemia
FALSE
-result of neural reflexes
(whatever the hell that means)
PFTs are not predictive of postop pulm complications. What is the exception to this?
lung reduction surgery
T/F - a flow volume loop where the inspiratory or expiratory portion of the loop is flat suggests that wheezing is cuased by asthma.
FALSE
-suggesting wheezing is a reslt of uppper airway obstruction (tracheal stenosis or foregin body)
What will an asthma CXR show
hyperinflated lungs with diaphragmatic flattening
How should you adjust vent settings for an asthamatic
-limit inspiratory time, prolong expiratory time
& tolerate moderate permissive hypercapnia
What does stimulation of presynaptic H2 receptors result in?
decreased histamine release
(H2 blockers [famotidine and ranitidine] can allow for unopposed H1 stimulation which can produce bronchospasm) - risk is very low though but hey, why not know it
What’s the problem with giving a beta-2 agonist to an asthmatic pregnant patient?
beta-2 agonists relax the uterus which can slow the progression of labor and lead to post-delivery bleeding .
What drug used to stop uterine bleeding in the OR can cause bronchoconstriction in asthmatics?
By what mechanism?
Carboprost (Hemabate)
-it mimics the action of F2 alpha prostaglandin …. great
Would you want to keep asthmatics on the drier side or hydrated side in terms of giving IV fluids
hydrated side to reduce the viscosity of airway secretions
What 4 things would indicate intraop bronchospasm
- Wheezing
- Decreased breath sounds
- Increased PIPs (increased plats)
- increased alpha angle on ETCO2
Treatment for acute bronchospasm: 6 key steps + 2 more
1. 100% FIO2
2. Deepen anesthetic (crank up gas and give propofol)
3. Albuterol
4. Ipratropium
5. Epi 1mcg/kg IV
6. Hydrocortisone 2-4mg/kg IV
- Aminophylline
- Helium-oxygen gas mixture
Alpha-1 antitrypsin deficiency: (select 2):
- increases risk of bronchospasm
- caues panlobular emphysema
- can be treated with IgG
- is the most common metabolic disease affecting the liver
- increases risk of bronchospasm
-caues panlobular emphysema
-can be treated with IgG
-is the most common metabolic disease affecting the liver
Treatment for Alpha-1 antitrypsin deficiency
liver transplant
What is alpha-1 antitrypsin deficency casue an increase in?
alveolar protease activity > an enzyme that degrades pulmonary connective tissue and leads to the development of panlobular emphysema.
How can you minimize the risk of oxygen-induced hypercapnia in the patient with severe COPD?
Titrate the FiO2 to maintain SaO2 between 88-92%
-Why would you see hypercarbia in a COPD patient receiving O2 therapy? and don’t say because o2 decreases their hypoxic drive to breathe
(How many times have you given o2 to a COPD patient and they stop breathing? never. )
- What does happen is O2 is a very potent pulmonary vasodilator, so if you give them oxygen your going to inhibit their HPV and worsen VQ matching
- your going to have blood going to non-ventilated alveoli which will increase CO2 bc it cant be dropped off at these non-ventilated alveoli to be exhaled
2. Haldane effect- hemoglobin that’s not bound to oxygen will bind hydrogen ions ; so when you give supplemental o2, the hgb kicks off the hydrogen ions and picks up the o2; the excess H+ ions will bind bicarbonate and produce more CO2
How is chronic bronchitis defined?
Cough + sputum production for more than 3 months for 2 consecutive years
What spirometry test is diagnositic of COPD
An FEV1/FVC ratio of < 70% after bronchodilator therapy
If oxygen therapy can cause hypercapneia in the COPD patient, what is the best practice in treating hypoxia?
O2 titrated to maintain a sat of 88-92%
Identify the MOST appropriate stategy for mechanical ventilation in the patient with COPD
- I:E ratio of 1:1
- Fio2 < 50%
- RR 7bpm
- TV 10-12ml/kg
RR 7bpm
Vent setting benificial to COPD:
I:E ratio:
Inspiratory flow:
FiO2:
RR:
TV:
PEEP? - why or why not
I:E ratio: increased (1:2.5-3 to allow more air to be exhaled)
Inspiratory flow: slow (improve VQ matching)
FiO2: adjusted to maintain SpO2 88-92% (avoid oxygen induced hypercapnia)
RR: slow- allows for increased expiratory times between breaths
TV: small (6-8ml/kg) to minimize risk of hyperinflation and PEEP to keep the small airways open instead of collapsing
neuraxial anesthesia should not be considered for COPD patients if a sensory blockade > ____ is required
T6
What block should be avoided in the COPD patient and why
interscalene block bc it causes paralysis of the ipsilateral hemidiaphagm