Respiratory Flashcards – First Aid for the USMLE STEP 1

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  • Large airways consist of what?
    nose pharynx trachea bronchi
  • small airways consist of what?
    bronchioles terminal bronchioles
  • physiological function of the conducting zone in respiratory tree?
    "warms, humidifies, and filters air but does not participate in gas exchange--> anatomic dead space"
  • which structural elements extend to the end of bronchi?
    cartilage goblet cells
  • which structural elements extend to the end of terminal bronchioles?
    pseudostratified ciliated columnar cells - beat mucus up and out of lungs smooth muscle of the airway walls - sparse beyond this point
  • anatomical structures present in the respiratory zone of the respiratory tree?
    "lung parenchyma; consists of respiratory bronchioles, alveolar ducts, alveoli."
  • function of the respiratory zone of the respiratory tree?
    participates in gas exchange
  • histology of the respiratory zone of the respiratory tree?
    "mostly cuboidal cells in respiratory bronchioles, then simple squamous cells up to alveoli. no cilia alveolar macrophages clear debris and participate in immune response"
  • which cells are present on 97% of alveolar surfaces?
    type I pneumocytes
  • features of type I pneumocytes?
    line the alveoli squamous thin for optimal gas diffusion
  • function of type II pneumocytes?
    1. secrete surfactant-->(decrease) alveolar surface tension and prevention of alveolar collapse 2. precursors to type I cells and other type II cells. 3. proliferate during lung damage
  • histology of type II pneumocytes?
    cuboidal and clustered
  • histology of Clara cells?
    noncliliated columnar with secretory granules
  • function of clara cells?
    secrete component of surfactant degrade toxins act as reserve cells
  • equation for alveolar collapsing pressure?
    P= 2T/r
  • alveoli have (increase) tendency to collapse when?
    on expiration as radius (decrease) (law of laplace)
  • what's in pulmonary surfactant?
    complex mix of lecithins most important is dipalmitoylphosphatidylcholine (DPPC)
  • when does surfactant synthesis begin?
    "around week 26 of gestation, but mature levels are not achieved until around week 35"
  • indicator of fetal lung maturity?
    lecithin:sphingomyelin ratio > 2.0
  • how many lobes in the lungs?
    R=3 lobes L= 2 lobes and lingula (homologue of right middle lobe)
  • more common site for inhaled foreign body?
    right lung because right main stem bronchus is wider and more vertical than left
  • where do you look when you aspirate a peanut while upright?
    lower portion of right inferior lobe
  • where do you look when you aspirate a peanut wile supine?
    superior portion of right inferior lobe
  • "instead of a middle lobe, left lung has what?"
    space occupied by the heart
  • relation of the pulmonary artery to the bronchus at each lung hilus is described by what?
    RALS Right anterior Left superior
  • structures perforating the diaphragm at T8?
    IVC
  • structures perforating the diaphragm at T10?
    esophagus vagus (2 trunks)
  • structures perforating the diaphragm at T12?
    "aorta (red) thoracic ducts (white) azygous vein (blue) at T-1-2 it's the red, white, and blue"
  • diaphragm is innervated by what?
    "C3, C4, C5 (phrenic nerve) C3,4,5 keeps the diaphragm alive"
  • pain from the diaphragm can be referred to where?
    "to the shoulder (C5) and the trapezius ridge (C3,4)"
  • mnemonic for the levels of structures perorating the diaphragm?
    I (IVC) ate (8) ten (10) eggs (esophagus) at (aorta) twelve (12)
  • what are the muscles used in quiet breathing?
    inspiration- diaphragm expiration- passive
  • what are the muscles used for breathing during exercise?
    "inspiration- external intercostals, Scalene muscles, SCM expiration- rectus abdominis, internal and external obliques, transversus abdominis, internal intercostals"
  • mnemonic for lung volumes?
    LITER Lungs: IRV TV ERV RV
  • what is inspiratory reserve volume (IRV)?
    air that can still be breathed in after normal inspiration
  • what is tidal volume (TV)?
    "air that moves into lung with each quiet inspiration, typically 500mL"
  • what is expiratory reserve volume (ERV)?
    air that can still be breathed out after normal expiration
  • what is residual volume (RV)?
    air in lung after maximal expiration; cannot be measured on spirometry
  • what is inspiratory capacity (IC)?
    IRV + TV
  • what is functional residual capacity (FRC)?
    RV + ERV (volume in lungs after normal expiration)
  • what is vital capacity (VC)?
    TV + IRV + ERV maximum volume of gas that can be expired after a maximal inspiration
  • what is total lung capacity (TLC)?
    TLC= IRV + TV + ERV + RV Volume of gas present in lungs after a maximal inspiration
  • equation for physiologic deadspace?
    "Vd= Vt x (Paco2 - Peco2)/Paco2 Taco, Paco, Peco, Paco"
  • definition of physiologic dead space?
    anatomic dead space of conducting airways plus functional dead space in alveoli volume of inspired air that does not take part in gas exchange
  • what is the largest contributor of functional dead space?
    apex of healthy lung
  • what is the state of the lung and chest wall at FRC?
    inward pull of lung is balanced by outward pull of chest wall and systemic pressure is atmospheric
  • what are the pressures at FRC?
    "airway and alveolar pressures are 0, and intrapleural pressure is negative (prevents pneumothorax)"
  • what is compliance?
    change in lung volume for a given change in pressure
  • compliance is (decrease) in what?
    "pulmonary fibrosis, pneumonia, and pulmonary edema"
  • compliance is (increase) in what?
    emphysema and normal aging
  • Hb is composed of what?
    4 polypeptide subunits (2alpha and 2 beta )
  • Hb exists in what 2 forms?
    T (taut)- low affinity for O2 R (relaxed)- high affinity for O2 [300x]
  • cooperativity and allostery of Hb?
    Hb exhibits positive cooperativity and negative allostery
  • what favors taut form over relaxed form of Hb?
    "(increase) Cl-, H+, CO2, 2,3-BPG, temperature shifts curve to the right -->(increase) O2 unloading"
  • mnemonic for 2 forms of hemoglobin?
    Taut in Tissues Relaxed in Respiratory
  • how does HbF compare to HbA?
    "HbF (alpha2gamma2) has lower affinity for 2,3-BPG than HbA and thus has a higher affinity for O2"
  • hemoglobin modifications lead to what?
    tissue hypoxia from (decrease) O2 saturation and (decrease) O2 content
  • what is methemoglobin?
    "oxidized form of Hb [ferric, Fe3+] that does not bind O2 as readily, but has (increase) affinity for cyanide"
  • methemoglobinemia can be treated with what?
    methylene blue
  • nitrites cause poisoning how?
    by oxidizing Fe++ to Fe+++
  • iron in Fe is normally in which state?
    reduced state ferrous Fe++
  • treatment for cyanide poisoning?
    "1. use nitrites to oxidize Hb to metHb, which binds cyanide, allowing cytochrome oxidase to function 2. use thiosulfate to bind this cyanide, forming thiocyanate, which is renally excreted"
  • what is carboxyhemoglobin?
    form of hemoglobin bound to CO in place of O2
  • carboxyhemoglobin causes what?
    (decrease) O2 binding capacity with a left shift in the oxygen-hemoglobin dissociation curve (decrease) O2 unloading in tissues
  • difference between CO and O2 Hb binding?
    CO has 200x greater affinity than O2 for Hb
  • sigmoidal shape of O2-Hb dissociation curve due to what?
    positive cooperativity (tetrameric Hb molecule can bind 4 O2 molecules and has higher affinity for each subsequent molecule bound)
  • features of myoglobin oxygen dissociation curve?
    myoglobin is monomeric and thuse does not show positive cooperativity; curve lacks sigmoidal appearance
  • what happens when O2-Hb curve shifts to the right?
    (decrease) affinity of Hb for O2 (facilitates unloading of O2 to tissues)
  • increase in all factors (except pH) causes what shift in O2-Hb curve?
    right
  • (decrease) in all factors (except pH) causes what shift in Hb-O2 curve?
    left
  • difference between HbA and HbF O2 dissociation curves?
    "HbF has a higher affinity for O2 than HbA, so its dissociation curve is shifted left"
  • mnemonic for right shift in Hb-O2 curve?
    C-BEAT CO2 BPG Exercise Acid/Altitude Temperature
  • pulmonary circulation is normally what type of system?
    "low resistance, high compliance system"
  • A (decrease) in PAo2 causes what in pulmonary circulation?
    a hypoxic vasoconstriction that shifts blood away from poorly ventilated regions of lung to well-ventilated regions
  • which substances exhibit perfusion limited equilibration?
    O2 (normal health) CO2 N2O gas equilibrates along the length of the capillary
  • "in perfusion limited exchange, diffusion can (increase) only if what?"
    blood flow (increase)
  • which substances exhibit diffusion limited equilibration?
    "O2 (emphysema, fibrosis) CO gas does not equilibrate by the time blood reaches the end of the capillary"
  • what is a consequence of pulmonary hypertension?
    "cor pulmonale and subsequent right ventricular failure (JVD, edema, hepatomegaly)"
  • what is the equation for diffusion in the pulmonary circulation?
    Vgas= A/T x Dk(P1 - P2) A= area T= thickness Dk(P1-P2)= difference in partial pressures
  • what (decrease) A in pulmonary circulation diffusion equation?
    emphysema
  • what (increase) T in pulmonary circulation diffusion equation?
    pulmonary fibrosis
  • normal pulmonary artery pressure= ?
    10-14 mmHg
  • pulmonary hypertension = what pressure?
    >= 25 mmHg or > 35mmHg during exercise
  • pulmonary hypertension results in what?
    "arteriosclerosis, medial hypertrophy, intimal fibrosis of pulmonary capillaries"
  • primary pulmonary hypertension due to what?
    inactivating mutation in BMPR2 gene (normally functions to inhibit vascular smooth muscle proliferation);
  • prognosis in primary pulmonary hypertension?
    poor
  • secondary pulmonary hypertension due to what?
    COPD mitral stenosis recurrent thromboemboli autoimmune disease left to right shunt sleep apnea or living at high altitude
  • how does COPD --> pulmonary hypertension?
    destruction of lung parenchyma
  • how does mitral stenosis lead to pulmonary hypertension?
    (increase) resistance -->(increase) pressure
  • how do recurrent thromboemboli cause pulmonary hypertension?
    (decrease) cross sectional area of pulmonary vascular bed
  • how does autoimmune disease cause pulmonary hypertension?
    systemic sclerosis inflammation --> intimal fibrosis --> medial hypertrophy
  • how does left to right shunt cause pulmonary hypertension?
    (increase) shear stress --> endothelial injury
  • how does sleep apnea/high altitude cause pulmonary hypertension?
    hypoxic vasoconstriction
  • what is the course of pulmonary hypertension?
    severe respiratory distress --> cyanosis and RVH --> death from decompensated cor pulmonale
  • what is the equation for pulmonary artery resistance?
    "PVR= (Ppulmartery - Pleftatrium)/CO deltaP=Q x R, so R= deltaP/Q R= 8nl/#r^4"
  • equation for oxygen content of blood?
    O2 content = (O2 binding capacity x %sat) + dissolved O2
  • how much O2 can normal Hb bind?
    normally 1 g Hb can bind 1.34 mL O2
  • normal Hb amount in blood is what?
    15/dL
  • cyanosis results when?
    deoxygenated Hb > 5g/dL
  • O2 binding capacity is ~?
    20.1 mL O2/dL
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