Resp Flashcards
What 5 resp structures are lined by stratified squamous epithelium instead of pseudostratified ciliated columnar cells?
True vocal cords, oropharynx, laryngopharynx, anterior epiglottis, upper half of posterior epiglottis
Tracheal pO2 = 150 mm Hg
Alveolar pO2 = 140 mm Hg
Alveolar pCO2 = 5 mm Hg
What’s the problem?
Poor alveolar perfusion (perfusion-limited gas exchanged)
Know this because tracheal pO2 is normal, alveolar pO2 is increased (normal should be 104 mm Hg), and alveolar pCO2 is decreased (normal should be 40 mm Hg).
If the problem had been related to diffusion-limited gas exchange (such as emphysema or fibrosis), you would see relatively normal alveolar pCO2 compared to pO2 because CO2’s diffusion capacity is much higher than O2 (CO2 is not a diffusion-limited gas)
If the problem had been poor alveolar ventilation, you would see alveolar gas composition close to venous blood (pO2 = 40 mm Hg and pCO2 = 45 mm Hg) because your problem isn’t that you don’t have enough time or perfusion to equilibrate, you just don’t have gas in to equilibrate with
Pt w/ COPD. Resp rate decreases after supplementing w/ cannular oxygen. This is because what stimulation is decreased?
Carotid bodies (main stimulation is hypoxemia, unlike central chemoreceptors in medulla whose main stimulation is increased CO2 -> main resp drive in HEALTHY ppl)
Pt w/ dyspnea, bibasillar crackles, and S3 w/ a recent hx of MI. What property of the lungs is responsible for dyspnea?
Pt is having classic sx of left HF -> fluid backs up -> fluid in pulm interstitium
So the property would be decreased lung compliance
How does panic attack cause dizziness, weakness, and blurred vision?
Hyperventilation leads to reduced PaCO2 in brain -> reduced blood flow to brain (think of central chemoreceptors detecting mainly PaCO2 level)
Has nothing to do w/ O2
Sign of cor pulmonale?
It’s right HF due to pulmonary HTN
so will see RV wall thickening w/ eventual dilation of RV chamber as pumping begins to fail
Give 3 changes in vessels when you have pulm HTN
Vasoconstriction (due to pulm venous congestion -> endothelial damage and leakage -> decreased NO synthesis and increased endothelin synthesis -> increased vascular tone)
Intimal thickening
Medial hypertrophy
What happens to the pulmonary artery flow in the setting of left HF?
Normal or decreased
NOT increased, b/c the problem would be backed up to LA -> pulm veins -> pulm congestion -> so the worse the condition, the lower the flow
Pulm arterial PRESSURE increases in left HF tho
Give formula for calculating PAO2 and the normal values for A-a gradient
PAO2 = 150 - PaCO2/0.8
Normal A-a gradient is PAO2 - PaO2 = 10-15 mmHg
(if increased, consider shunting, V/Q mismatch, fibrosis, R-to-L shunt, cyanotic congenital heart defects)
What 2 circumstances would you have increased tissue CO2 production?
Exercise
Severe infection
What 2 circumstances would you have increased mixed venous O2 content?
Conditions obstructing O2 unloading -> abnormal Hb binding O2 w/ greater affinity
Conditions where oxidative metabolism is affected -> cyanide toxicity
How does silicosis increase susceptibility to TB?
It impairs macrophage killing by disrupting phagolysosomes
Give lung primary main of defense against diff sizes of particles
Large (10-15 uM): trapped in upper resp tract
Medium (2.5-10 uM): mucociliary clearance (trapped in trachea and up to proximal portion of resp bronchioles)
Small (< 2.5 uM): macrophages (distal to terminal bronchioles)
AA w/ hilar adenopathy + pulm infiltrates + noncaseating granuloma + elevated ACE + hypercalcemia. Dx?
Sarcoidosis (granuloma produce ACE and active vit D)
Will see constitutional sx! Will also see liver granulomas (like portal triads) as well. Don’t let that distract you.
Paroxysmal episodes of breathlessness + wheezing w/ no hx of aspirin, pulm infection, inhaled irritants, stress, exercise. What should you suspect?
Extrinsic allergic asthma
Granule-containing cells and crystalloid masses in sputum. What are you thinking?
Eosinophils and Carcot-Leyden crystals (containing eosinophil membrane protein) -> think IL-5 role
Extrinsic allergic asthma
Severe SOB + prolong expiration + prominent wheezing + pulsus paradoxus. Dx? Tx?
Severe asthmatic episode
Give B-blocker acutely. Corticosteroids (which works by inhibiting eosinophil degranulation) are useful for asthma but take too long to take effects, and mast cell stabilizer is only useful for prophylaxis
3 risk factors of OSA?
Obesity
Tonsillar hypertrophy
Hypothyroidism
CD4+/CD8+ ratio in sarcoidosis and hypersensitivity pneumonitis? What are their similarity?
CD4+/CD8+ ratio > 2:1 (so CD4+ predominance) in sarcoidosis
CD8+ predominance in hypersensitivity pneumonitis
Both sarcoidosis and hypersensitivity pneumonitis have noncaseating granulomas
Where does aspirated content go if it happens when you’re lying down? Standing up?
POS. segment of RIGHT UPPER lobe or SUP. segment of LOWER lobe
NOT middle lobe, because middle lobe is actually situated anteriorly
If standing up, it’ll go to basilar segment of lower lobe
What lecithin-sphingomyelin ratio means lung has matured? What hormone has the greatest effect on lung development?
> 1.9
Cortisol
2 mediators in atopic asthma that can actually be effectively targeted by pharmacotherapeutic agents
- Leukotrienes: LTD4, LTE4, LTC4 -> montelukast and zafirlukast
- ACh -> ipratropium
Finding expected from pt who died from sudden death after being on appetite suppressant
“-fenfluramine” and phentermine for more than 3 months -> secondary pulm HTN -> cor pulmonale and RV hypertrophy
What is sudden death from PE due to?
Electromechanical dissociation (heart is pumping but blood can’t go any further)
What’s koilonychia and what is it a sign of?
Spoon-shaped nail
One of the signs of iron deficiency anemia
2 conditions where you see elevated FEP (free erythrocyte protoporphyrin)
Heme = Fe (defects) + Protoporphyrin (more float unbound) -> so find in
Iron deficiency anemia
Anemia of chronic disease (iron locked up by hepcidin)
2 ways that hepcidin sequesters iron in storage
- limits iron transfer from macrophages to erythroid precursors
- suppresses EPO production
PE signs and sx of airway obstruction?
Rhonchi, wheezing -> turbulent airflow 2ndary to obstruction
Most common cause of acute small airway obstruction in infants? What’s the tx?
RSV bronchiolitis
Ribavirin only if severe
Steps leading to adaptation when living in high altitude?
High alt means lower PO2 -> lower PaO2 -> carotid and aortic bodies tell your body to hyperventilate -> PaCO2 goes down (resp alkalosis) ->
48 hrs later: renal compensation (so now gets low HCO3-)
10-14 days: increased production of EPO -> so now PaO2 is almost restored (compensation only effective up to about 4000 m)
What kinds of things will be present in lung hamartoma?
Aka pulmonary chondroma -> most common benign lung tumor
Will see mature islands of hyaline cartilage, fat, smooth muscle and clefts lined by resp epithelium
Well-defined lesion w/ popcorn calcification
Where are club cells (Clara cells) and what is their fx?
Bronchioles (starts replacing goblet cells as the secretory cells from this level onward)
Regenerative source of ciliated cells in the bronchioles, helps detoxify inhaled substance by cytochrome P450 mechanism, prevents BRONCHIOLAR collapse (more upstream stuff)
A person w/ lung mass complains of shoulder pain, persistent hiccups, and dyspnea. What nerve roots are affected?
C3-5 -> think phrenic n. whenever you have pain at shoulder
Don’t think about pancoast tumor affecting brachial plexus (if that’s the case, C8-T2 would be affected and sx would be different)
What lung cancer is assc. w/ SVC syndrome?
Small cell lung cancer
Lung infiltrates w/ dry cough on a pt who was on cruise ship (or exposed to some kind of contaminated water like spas, hospitals, A/C hotels)?
Legionnaire’s disease -> so will see hyponatremia, high fever w/ relative bradycardia, transaminitis -> gram stain will show many neutrophils but no org (intracellular)
Pulmonary infiltrates + eosinophilia?
Loffler -> suspect helminthic infections
What are 2 upper resp sx of CF?
Bilateral sinusitis and nasal polyps
Why does blood arriving in the LA have lower O2 content than blood in the pulmonary capillaries (that just freshly picked up O2 from alveoli)?
Venous admixture -> b/c only a little of blood in bronchial arteries (2nd blood supply to lungs) goes back in bronchial veins; most actually gets carried back in bronchial arteries which are then mixed w/ pulmonary veins (the freshly oxygenated) before returning to LA -> so really bronchial blood gets to bypass the right side of the heart
What should you always assc. insufficient surfactant production w/?
Patchy atelectasis! (think of neonatal resp distress syndrome)
NOT pulm HTN (hypoxic pulm vasoconstriction created from this condition alone is not enough to cause pulm HTN)
URI followed 2 days later by brassy cough and difficulty breathing. What’s the org?
Parainfluenza (paramyxoviridae)
Brassy cough = croup
Major cause of spontaneous pneumothorax?
Rupture of apical blebs
Differences in distribution of 2 types of emphysema
Centriacinar (smoking): likes upper lobe
Panacinar (A1AT def): likes lower lobe
How is bronchial hyperreactivity (BHR) quantified?
Conc of bronchoconstrictive substance (ie methacholine) required to produce > 20% reduction in FEV1
Law of Laplace and its implication?
Distending pressure = T/2r
So smaller radius sphere -> more pressure -> so will collapse into larger radius sphere b/c air flows from high pressure to low pressure
Surfactant decreases surface tension as the sphere decreases in size -> so you get proportional reduction in T as you go down in r -> keep distending pressure operable
Differences bet. Lambert-Eaton myasthenic syndrome (LEMS) assc. w/ small cell lung cancer and ocular myasthenia gravis?
Both have ocular stuff
but LEMS pts have hypo/areflexia, autonomic sx, classic incremental response to repetitive stimulation
What does graph of work of breathing (y) vs. respiratory rate (x) tell you?
Looking at the RR at which the graph takes the most dip can tell you whether it’s restrictive or obstructive lung disease!
Normal dip is at RR = 15 breaths/min
In restrictive lung diseases (increased elastic resistance) -> the optimum RR is higher -> meaning pt will take rapid and shallow breaths b/c the work of breathing is minimum with high RR and low tidal volume -> think of stiff elastic band swinging back and forth quickly for increased elastic resistance
In obstructive lung disease (increased airflow resistance) -> optimum RR is lower -> meaning pt will take slow, deep breaths b/c the work of breathing is minimum w/ low RR and high tidal volume
What 2 cells play a role in centriacinar emphysema?
Neutrophils -> secretes elastase, which is inhibited by serum a1 antitrypsin
Macrophages -> secretes elastase, which is inhibited by TIMPs (tissue inhibitors of metalloproteinases) -> so unaffected by A1AT!
2 mechanisms behind pulm and CNS sx of fat embolism?
- Platelets coat fat emboli and release mediators
2. Systemic activation of LPL and intravascular release of oleic acid
What levels do you perform thoracentesis if you do it mid-clavicular, mid-axillary, and paravertebral?
All performed in top margin of rib (if do it on inf margin -> risks striking subcostal neurovascular bundle)
Mid-clavicular: above 7th rib (bet. 5th-7th)
Mid-axillary: above 9th rib (bet. 7th-9th)
Paravertebral: above 11th rib (bet. 9th-11th)
If do it lower than the levels indicated -> risk puncturing liver (assuming right side)
If do it higher -> risk puncturing lungs (levels given are borders of pleura)
What do you give in asthma resistant to steroids?
Omalizumab (anti-IgE Ab subQ injection) -> useful in moderate-severe allergic asthma
What’s tachyphylaxis and what do you do when this happens?
Tachyphylaxis = decrease in effect due to negative feedback
Example 1: using a1 antagonist nasal decongestants decreases NE release from nerve terminal due to neg feedback -> rebond rinorrhea (rhinitis medicamentosa) when using it past >3 days
Stop the drug when this happens
Example 2: nitroglycerine -> maintain drug-free interval of 8-10 hrs to prevent this