Respiratory Pathophysiology Flashcards
What has the most significant effect on airflow resistance?
Airway radius
Does PNS stimulation result in bronchoconstriction or bronchodilation?
Bronchoconstriction via the Vagus
Does mast cell stimulation result in bronchoconstriction or bronchodilation?
Bronchoconstriction
What sympathetic nerve causes bronchodilation?
No nerves. The beta 2 receptors are activated by circulating catecholamines, not nerves.
Cholinergic nerves endings release _____ onto ______ receptors.
Acetylcholine
M3 Receptors
What is the effect of Phospholipase C activation in airway tissues?
Causes an increase in intracellular calcium, resulting in contraction (bronchoconstriction)
What is the effect of Adenylate Cyclase/cAMP activation in airway tissues?
A decrease in intracellular calcium, resulting in dilation (bronchodilation)
What is the effect of vasoactive intestinal peptide in airway tissues?
Increase NO production, which stimulates cGMP and results in bronchodilation
There are three classes of pulmonary medications:
- Direct acting bronchodilators
- Anti-Inflammatories
- Methylxanthines
What are the two types of direct-acting bronchodilators?
Beta-2 Agonists
Anticholinergics
What anti-inflammatory drugs are used for pulmonary disease?
Corticosteroids
Cromolyn
Leukotriene Modifiers
What is the MOA of theophylline?
Its a phosphodiesterase inhibitor, which increases cAMP and decreases intracellular calcium
It also increases endogenous catecholamine release
What is the most sensitive test for small airway obstructive disease?
Forced expiratory flow at 25-75% vital capacity
What is a normal FEV1?
> 80% of predicted value (which changes with age)
What is a forced vital capacity
The volume of air that can be exhaled after a maximal inhalation
What does the FEV1/FVC ratio measure?
Compares the air expired in 1 second to the total volume of air expired.
Helps in deciphering restrictive vs. obstructive disease.
If there’s restriction, they’ll have a normal ratio. There’s less air going out because there’s less air coming in, but everything inhaled is exhaled.
If there’s obstruction, the ratio will be < 70%, meaning they’re getting a normal amount in but not all of that is being exhaled.
What is the MMEF?
Mid Maximal Expiratory Flow Rate… another name for Forced Expiratory Flow at 25-75% of VC
Reduced with obstructive disease
Normal with restrictive disease
What is the best pulmonary test of endurance?
Maximum voluntary ventilation (MVV)
Maximum volume that can be inhaled and exhaled over 1 minute
What does DLCO measure?
The ability of the alveolocapillary membrane to exchange gas
DLCO measurement is based on what law?
Fick’s law of diffusion
What is a normal DLCO?
17-25 ml/min/mmHg
What patient subsets are particularly at risk for postop pulmonary complications?
COPD
Elderly
CHF
Smoking
What procedures carry a higher risk of postop pulmonary complciations?
Surgery > 2 hrs
General Anesthesia
Aortic Surgery
Abdominal Surgery
Neuro and peripheral vascular surgery
How does a patient have to quit smoking in order to have decreased risk of postop pulmonary complications?
At least 6 weeks
Short term cessation will improve P50, but not complication rate
What are some risk reduction strategies to prevent postop pulmonary complications?
Alveolar recruitment maneuvers and PEEP
Bronchodilators/Steroids for obstructive disorders
Treat active infections
Consider not doing a general anesthetic
Teach the patient pulmonary recruitment maneuvers
What lab value indicates a high risk for postop pulmonary problems?
Albumin < 3.5, because it indicates poor nutritional status
What are alveolar recruitment maneuvers?
Peak airway pressure of 30cmH20 is required to reopen atelectic regions
Increase PIP to 40 for 8 seconds
If a patient with asthmas bronchospasms immediately following tracheal intubation, what is the most likely cause?
Vagal stimulation
What is the most common ABG finding during an asthma attack?
Respiratory alkalosis from increased Mv
What are some histamine releasing drugs that should be avoided in patients with asthma?
Morphine
Meperidine
Succinylcholine
Atracurium
What would a chest x ray look like in a patient with an asthma attack?
Hyperinflated lungs with diaphragmatic flattening
Should an HME be used in patients with asthma?
It may benefit patients with exercise-induced asthma
What dose of IV lidocaine suppresses airway reflexes?
1-1.5 mg/kg
Why can’t asthmatics have hemabate?
It mimics the actions of pro-inflammatory prostaglandins
What are the clinical features of chronic bronchitis?
hypertrophied mucus glands
chronic inflammation
What are the clinical features of emphysema?
Enlargement and destruction of the airways DISTAL TO the terminal bronchioles
In patients with severe COPD, what FiO2 should be used?
The least amount required to maintain SpO2 between 88 and 92%
What does alpha 1 antitrypsin do?
Its an enzyme produced by the liver that inhibits alveolar elastase (which breaks down elastic tissue)
Does supplemental oxygen suppress hypoxic drive in patients with COPD?
No - but it can cause oxygen-induced hypercapnea
It can cause inhibition of HPV AND an increase in hypercarbia because of the Haldane effect
Should you use nitrous in patients with COPD?
Meh. It rupture pulmonary blebs and cause a pneumothorax
What are the highest risk factors for aspiration?
Pregnancy
Trauma
Emergency Surgery
GI Obstruction
What is Mendelson’s Syndrome?
Aspiration Pneumonitis
What are the S/S of aspiration pneumonia?
Hypoxemia (hallmark sign)
Dyspnea
Tachypnea
Cyanosis
How long should patients who are suspected of aspiration be watched in PACU?
At least 2 hours. If they look good at that point and have a clean CXR they can go home.
What percentage of people who aspirate get sick?
60% remain asymptomatic
20% require support
15% require ventilation > 6 hours
5% die
What are the most common pathogens responsible for VAP?
Pseudomonas and Staph Aureus
What are the hallmark characteristics of a tension pneumothorax?
Hypoxemia
Increased airway pressures
Tachycardia
Hypotension
Elevated CVP
POCUS on a patient with a Pneumo will show:
absent sliding and absence of comet tails
What causes a closed pneumothorax?
A defect in the pulmonary tree or lung tissue itself, NOT the chest wall
What causes a chylothorax?
The thoracic duct empties lymph into the left subclavian vein. Injury to the duct during CL insertion can cause chylothorax.
What is the treatment for VAE?
Administering 100% FiO2
Flooding the surgical field
Discontinuing insufflation
Employing the durant maneuver
What is the Durant Maneuver?
Left lateral decubitus position
Which drugs notoriously increase PVR?
Nitrous Oxide
Ketamine
Desflurane
What drugs notoriously decrease PVR?
Nitric Oxide
Nitroglycerin
PDEs
PGE1 and PGI2
Ca Channel blockers
ACE Inhibitors
What ventilator settings decrease PVR?
Spontaneous breathing
Preventing coughing/straining
What ventilator setting increase PVR?
PEEP
Any degree of atelectasis
What effect does CO2 have on PVR?
Hypercarbia INCREASES PVR
Hypocarbia DECREASES PVR
Which is better in patients with pHTN: epidural or spinal?
Epidural. They’re very preload dependent.
What is the half life of CO?
4-6 hours on RA
60-90 minutes on 100%
When is hyperbaric oxygen indicated for CO poisoning?
If CoHgb exceeds 25% or the patient is symptomatic
What is the affinity for Hgb in CO vs O2?
200x higher in CO
In patients with CO poisoning, 100% O2 should be continued until:
the CoHgb is less than 5%
What are strong indicators that mechanical ventilation is needed?
- Vital Capacity < 15ml/kg
- Insp Force < 25
- PaO2 < 200 on 100%
- A-a gradient > 450 on 100%
- PaCo2 > 60
- RR > 40 or < 6
Which drugs can be given down the ETT?
NAVEL
Narcan
Atropine
Vasopressin
Epinephrine
Lidocaine
What are the best predictors of postoperative pulmonary complications for patients undergoing OLV?
FEV1 < 40% predicted
DLCO , 40% predicted
VO2 max < 15 ml/kg/min
When should split lung V/Q function testing be performed?
When the predictors for poor postop pulmonary performance are present
What are absolute indications for OLV?
Infection
Massive Hemorrhage
Bronchopleural Fistula
What are relative indications for OLV?
Improved surgical exposure
Pulmonary Edema
Severe hypoxemia due to lung disease
When should a R sided DLT be used?
L Main bronchus has distorted anatomy (tumor, TAA)
L Pneumonectomy, LL transplant, L sleeve resection,
What is the ideal DLT size in women?
In Men?
Female 35-37
Male 39-41
At what age can DLTs be used in children?
Should not be used in children under 8. Should use a bronchial blocker or single lumen tube in children less than 8.
What is the average insertion depth for a DLT in females?
In Males?
Females 27
Males 29
What is the appropriate size of DLT in a child 8-9 years old?
26
What is the appropriate size of DLT in a child 10+?
28 or 32
What structures should you visualize when checking DLT placement fiberoptically?
- The Trachial Lumen
- The blue of the bronchial cuff should just barely be visible
- There should be three take offs on the R bronchus
- There should be two take offs on the L bronchus
What are the steps to evaluating a L sided DLT?
- Inflate both cuffs and clamp the tracheal, then ventilate the bronchial
- Keep both cuffs inflated and clamp the bronchial, then ventilate the tracheal
- Deflate the bronchial cuff and keep in clamped then ventilate the tracheal
What should you do if a patient becomes hypoxemic during OLV?
- Administer 100%
- Check position fiberoptically
- Rule out physiologica causes (CO, mucus, bronchospasm)
- Apply CPAP 2-10 to non-dependent lung OR insufflate oxygen through a suction catheter
- Apply PEEP to the dependent lung and CPAP to non-dependent
- Consider converting to a TIVA
Is hypoxemia more common during OLV on the right or left lung?
Right Lung
The left lung is smaller, so there’s less surface area for gas exchange
What is an absolute contraindication of mediastinoscopy?
A previous mediastinoscopy, due to scarring
What are the most common complications of mediastinoscopy?
Hemorrhage and Pneumothorax
What disease often accompanies oat cell carcinoma?
Eaton-Lambert Syndrome
Trace the vascular anatomy from the heart to the brain
For a mediastinoscopy, where should the art line and SpO2 probe be placed?
RUE, just like for babies
If the innominate artery is compressed, your art line and SpO2 waveform will dampen
For a mediastinoscopy, where should the NIBP cuff be placed?
On the Left. You don’t want to confuse your cuff going off with compression of the innominate artery
What is the ideal placement for large PIV in a mediastinoscopy?
The lower extremities. If it’s in the upper extremities, there’s a good chance blood transfused will pass through one of the damaged vessels
What are the three stages of ARDS?
Exudative
Proliferative
Fibrotic
What are the four pathophysiologic processes of ARDS?
- Protein rich pulmonary edema
- Loss of surfactant
- Hyaline membrane formation
- Possible fibrotic injury
