Respiratory - Physiology

evolv3's version from 2015-04-28 17:16

Lung volumes

Question Answer
Inspiratory reserve volume (IRV) - Air that can still be breathed in after normal inspiration
Tidal volume (TV)Air that moves into lung with each quiet inspiration . typically 500mL
Expiratory reserve volumeAir that can still be breathed out after normal expiration
Residual volume (RV)Air in lung after maximal expiration; cannot be measure on spirometry
Inspiratory capacity (IC)IRV + TV
Functional residual capacityRV +ERV (volume in lungs after normal expiration)
Vital capacity (VC)TV +IRV +ERV = maximum volume of gas that can expired after a maximal inspiration
Total lung capacity (TLC)TLC = IRV + TV + ERV + RV - volume of gas present in lungs after a maximal inspiration
How is physiologic dead space calculated?VD = VT x (PaCO2 - PeCO2)/PaCO2 ---- Taco,Paco,Peco,Paco

Lung and Chest Wall

Question Answer
What is FRC?Tendency for lungs to collapse inward and chest wall to spring outward - At FRC , inward pull of lungs is balanced by outward pull of chest wall, and system pressure is at atmospheric
What is the pressure of airway and alevoli at FRC?0
What is the intrapleural pressure at FRC?negative
Compliance for pulmonary fibrosis, pneuomnia, and pulmonary edema?Decreases
Compliance for for emphysema and normal agingIncreases


Question Answer
Hemoglobin subunitsis composed of 4 polypeptides subunits 2alpha and 2 beta
Hemoglobin conformations2 forms = T (taut) form has low affinity for O2 and R (relaxed) form has high affinity for O2 (300x).
What special bindings properties does hemoglobin exhibit?Hemoglobin exhibits positive cooperativity and negative allostery
What increases the formation of T form of hemoglobin?increased Cl-, H+, CO2, 2,3,-BPG, and temperature
Fetal hemoglobin (2 alpha and 2 gamma subunits) difference from adult form?has lower affinity for 2,3 BPG than adult hemoglobin and thus has higher affinity for O2.
MethemoglobinOxidized form of hemoglobin (ferric Fe3+) that does not bind O2 as readily , but has increased affinity for cyanide.
What the normal form of iron in hemoglobin?Ferrous Fe2+
What is the treatment for cyanide poisoning?To treat cyanide poisoning , use nitrites to oxidize hemoglobin to methemoglobin, which binds cyanide, allowing cytochrome oxidase to function. Use thiosulfate to bind this cyanide, forming thiocyanate, which is renally excreted.
CarboxyhemoglobinForm of hemoglobin bound to CO in place of O2. Causes decreased in oxygen binding capacity with a left shit in the oxygen hemoglobin dissociation curve. Decreased oxygen unloading in tissues.
Oxygen - Hemoglobin dissociation curve shifts to the right byincreases in CO2, BPG (2,3BPG), Exercise, Acid/Altitude, Temperature C-BEAT
Oxygen - Hemoglobin dissociation curve shifts to right mean?There is decreased affinity of hemoglobin for O2 (faciliatates unloading of O2 to tissue)
What is the oxygen-dissociation curve for fetus?Fetal Hb has higher affinity for oxygen than adult Hb, so its dissociation curve is shifted to the left.

Pulmonary circulation

Question Answer
What does a decrease in PAO2 cause?Hypoxic vasoconstriction that shifts blood away from poorly ventilated regions of lung to well ventilated regions of lung
What does perfusion limited oxygenation mean?Gas equilibrates early along the length of the pulmonary capillary, but diffusion can be increase only if blood flow is increased.
What does diffusion limited oxygenation mean?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 (jugular venous distention, edema, hepatomegaly
What is the equation for diffusion?Vgas = A/T x Dk (P1 - P2) where A = area, T = thickness , and Dk (P1-P2) = difference in partial pressure; A is decreased in emphysema and T is increased in pulmonary fibrosis

Pulmonary hypertension

Question Answer
What the normal pulmonary artery pressure?10-14 mmHg
What is the pulmonary artery pressure in pulmonary hypertension?greater than 25mmHg or greater than 35 mmHg during exercise
What histologic changes occurs in pulmonary hypertension?arteriosclerosis, medial hypertrophy, and intimal fibrosis of pulmonary arteries
What is primary pulmonary hypertension?Due to an inactivating mutation in the BMPR2 gene (normally functions to inhibit the vascular smooth muscle proliferation); poor prognosis
What is secondary pulmonary hypertension?due to COPD (destruction of lung parenchyma) ; mitral stenosis (increases resistance causing increased pressure) ; recurrent thromboemoboli (decreased cross-sectional area of pulmonary vascular bed) ; autoimmune disease ( e.g systemic sclerosis ; inflammation which leads to intimal fibrosis which leads to medial hypetrophy) ; left to right shunt ( leads to increased shear stress leading to endothelial injury); sleep apnea or living at high altitude (hypoxic vasoconstriction)
What is the course of severe respiratory distress?Cyanosis and RVH then death from decompensated cor pulmonale
What is the equation for pulmonary vascular resistance?PVR = (P pulm artery - P L atrium)/(Cardiac Output) ; Pulm artery = pressure in pulmonary artery and P L atrium = pulmonary wedge pressure
Vessel radius, viscosity , and vessel length relationship with resistance?R = 8(viscosity)length / pie*r^4

Oxygen Content of blood

Question Answer
O2 content(O2 binding capacity x % saturation) + dissolved O2
How much can 1 g Hb bind Oxygen?1.34mL O2
What is the normal amount of Hb in blood?15g/dL
At what amount of deoxygenated Hb does cyanosis result?greater than 5g/dL
As Hb falls what happens to O2 content of arterial blood, O2 saturation, and arterial PO2?O2 content of arterial blood falls but O2 saturation and arterial PO2 do not.
How is oxygen delivery to tissues calculated?cardiac output x oxygen content of blood
What is alveolar gas equation?PAO2 = PIO2 - PaCO2/R ; PAO2 = alveolar PO2 (mmHg) ; PIO2 = PO2 in inspired air (mmHg) ; PaCO2 = arterila PCO2 (mmHg) ; R = respiratory quotient - CO2 produced/O2 consumed
What is the equation for A-a gradient?PAO2 = 150 - PaO2/0.8 approximatin

Oxygen Deprivation and V/Q mismatch

Question Answer
hypoxemia with normal A-a gradientHigh altitude, hypovenitilation
hypoxemia with increased A-a gradientV/Q mismatch, diffusion limited, right to left shunt
Hypoxia causescardiac output decreased, hypoxemia, anemia, CO poisoning
What is ideal V/QV/Q - 1
What is the V/Q rations at the apex and base of lungapex = 3 and at the base = 0.6
Which organisms thrive at the apex of lungs?TB
In airway obstruction what is the V/Q ratio?V/Q = zero
In blood flow obstruction what is the V/Q ratio?V/Q = infinite
Does a shunt improve with oxygen?No
Does blood flow obstruction improve with oxygen?yes


Question Answer
What 3 forms is carbon dioxide transported from tissue to the lungs?a. Bicarbonate (90%) b. Carbaminohemoglobin or HbCO2 (5%) c. Dissolved CO2 (5%)
What is the Haldane effect?In lungs, oxygenation of Hb promotes dissociation of H+ from Hb this shifts Equlibrium toward CO2 formation ; there CO2 is released from RBCs
What is the Bohr effect?Increasing H+ from tissue metabolism shifts curve to right, unloading O2 from hemoglobin in peripheral tissue
What is the majority of blood CO2 carried as?bicarbonate


Question Answer
What is the response to high altitudea. Acute increase in ventilation , decreased in PO2 and PCO2 b. Chronicaly there is an increase in ventilation c. Increased in erythropoietin increasing hematocrit and hemoglobin (chronic hypoxia) d. Increases in 2,3-BPG (binds to hemoglobin so that hemoglobin releases more O2) f. Cellular chnages include increases in mitochondria g. Increased renal excretion of bicarbonate ( e.g. can augment by use of acetazolamide) to compensate respiratory alkalosis
What is the responese exercisde?a. Increased CO2 production b. Increased O2 consumption c. Increased ventilation rate to meet O2 demand d. V/Q ratio from apex to base becomes more uniform e. Increased pulmonary blood flow due to increased cardiac output f. decreased pH during strenous exercise secondary to lactic acidosis
What occurs with PaO2 and PaCO2 during exercise?No changes , but increased in venous CO2 content and decreased in venous O2 content are seen