What is inspiratory reserve volume?
air that can still be inspired after normal tidal inspiration
What is tidal volume?
Air that moves into the lung with each quiet inspiration, normally 500 mL
What is exspiratory reserve volume?
air that can still be breathed out after normal expiration
What is residual volume?
The total amount of air remaining in the lung after maximal expiration (cannot be measured on spirometry)
What is inspiratory capacity?
What is functional residual capacity?
RV + ERV (cannot be measured on spirometry because it includes residual volume)
What is vital capacity?
TV + IRV + ERV, or the maximum volume of gas that can be expired after a maximal inspiration
What is total lung capacity?
IRV + TV + ERV+ RV (cannot be measured on spirometry)
What is physiologic dead spead?
Vd= the anatomic dead space of conducting airways plus alveolar dead space, or the volume of inspired air that does not participate in gas exchange
What is the eqn for physiologic dead space?
Vd= Vt *((PaCo2- PECo2)/PaCo2), where
Vt= tidal volume
PaCo2= arterial Co2
PeCo2= expired air Co2
Taco Paco Peco Paco
What part of the lung is the largest contributor of alveolar dead space?
What is the eqn for minute ventilation?
total volume of gas entering the lungs per minute
What is the eqn for alveolar ventilation?
Volume of the gas per unit time that reaches the alveoli
What is a normal physiological dead space volume?
Compliance increases in what kinds of lung disease?
obstructive, such as emphysema, and in normal aging
Compliance decreases in what kinds of lung disease?
Restrictive disease, such as Pulmonary fibrosis, pneumonia, and pulmonary edema
What is hysteresis?
the fact the the lung inflation curve is different than that of the deflation curve due to the need to overcome surfac tension to expand
What is the structure of hemoglobin?
4 polypeptide subunits, 2 alpha, and 2 beta
What are the conformations of hemoglobin?
T (taut) and R (relaxed)
Taut near tissue and
Relaxed near respiratory areas
What are some characteristics of taut hemoglobin?
This form has LOW affinity for O2, thus promoting release/unloading of oxygen (whereas hemoglobin in a relaxed form would be more likely to hold onto oxygen)
What things promote a taut orientation of hemoglobin?
increased Cl-, CO2, H+ (acidotic), 2-3-BPG, and increased temp all favor a RIGHT SHIFT of the dissociation curve for increased o2 unloading
What is the composition of fetal hemoglobin?
2a and 2y subunits that have HIGHER affinity for O2 than adult Hb, driving duffion of oxygen across the palcenta to the fetus
NOTE: a higher affinity for O2 moves the fetal oxygen-hemoglobin dissociation curve to the LEFT
What is methemoglobin?
A modified form of hemoglobin in which the central iron is in a ferric (Fe3+) state that does NOT bind O2 as readily, but has increased affinity for cyanide
NOTE: Iron in normal hemoglobin is an Fe2+ state
How might someone with methemoglobemia present?
cyanosis and chocolate-colored blood
How can methemoglobinemia be treated?
methylene blue and vitamin C
What are some things that cause methemoglobinemia?
nitrates and benzocaine
How can methemoglobinemia be used medically to our advantage?
It can be medically induced using nitrrites followed by thiosulfate to treat cyanide poisoning
How would carboxyhemoglobin be treated?
Describe these curves
Hemoglobin has a sigmodial curve due to positive cooperativity of O2 binding by successive hemoglobin subunits, while myoglobin does not exhibit this property
What happens when the oxygen-hemoglobin dissociation curve shifts to the right?
There is decreased affinity of Hb for O2, which facilitates easier unloading of O2 into tissue
What things cause a right shift of the oxygen-hemoglobin dissociation curve?
Right shift: ACE BATs right
Which shift, right or left, of the oxygen-hemoglobin dissociation curve would cause increased EPO synthesis?
left because O2 is not being unloaded as easily leading to hypoxia
What is the eqn for the oxygen content of blood?
(1.34*Hb*SaO2) + (0.003*PaO2)
Hb= hemoglobin levels
SaO2= arterial O2 saturation
T or F. With decreased hemoglobin, there is decreased O2 content of blood but no change in O2 saturation and PaO2
What is the eqn for O2 delivery to tissue?
CO x O2 content of blood
How does CO poisoning affect Hb concentration? SaO2? PaO2? Total O2 content?
Hb concentration- normal
Total O2 content- decreased
How does anemia affect Hb concentration? SaO2? PaO2? Total O2 content?
Hb concentration- decreased
Total O2 content- decreased
How does polycythemia affect Hb concentration? SaO2? PaO2? Total O2 content?
Hb concentration- increased
Total O2 content- increased
How does hypoxia affect the pulmonary circulation?
Normally it is a low-resistance, high-compliance system but in the absence of adequate oxygen, hypoxic vasoconstriction occurs that helps shift blood away from poorly ventilated regions
What are some situations of gas exchange that are perfusion limited?
O2 in normal states, CO2, N2O
In these states, diffusion can only be increased if blood flow increases
What are some situations of gas exchange that are diffusion limited?
emphysema and fibrosis, CO
In these states, gas does not equilibrate by the time blood reaches the end of a capillary
What is the eqn for diffusion of a gas?
Diffusion= A*Dk*(P1-P2)/T, where
Dk(P1-P2)= difference in partial pressure
T= thickness of wall
What variable of the gas exchange eqn is changed in emphysema?
A is decreases
What variable of the gas exchange eqn is changed in pulmonary fibrosis?
T is increased
What is the eqn for pukmonary vascular resistance?
PVR= (Ppulm a.- Pleft atrium)/CO
What is the eqn for alveolar gas exchange?
pAO2= PIo2- PaCO2/R, where
pA02= alveolar O2
PaCO2= arterial Co2
R= respiratory quotient, or Co2 produced at tissue/O2 consumed
Normal alveolar gas eqn.
PAO2= 150- PaCo2/0.8
What is the A-a gradient?
Normal= ~10 mm Hg
What things can make an A-a gradient increase?
hypoxia caused by shunting, V/Q mismatch, and fibrosis
What is hypoxia?
decreases O2 delivery to tissue
What are some causes of hypoxia?
decreased CO, anemia, CO poisoning, and hypoxemia
What is hypoxemia?
What are some causes of hypoxemia with a NORMAL A-a gradient?
high altitude and hypoventilation (i.e. overdose)
What are some causes of hypoxemia with an INCREASED A-a gradient?
V/Q mismatch, Diffusion limitation (fibrosis), Right-to-left shunt
What are the V/Q ratios in different parts of the lung?
Apex= 3 (wasted ventilation)
Base= 0.6 (wasted blood flow/perfusion)
T or F. Both ventilation and perfusion are greater at the base of the lung compared to the apex
What happens to the V/Q ratio with exercise?
vasodilation of apical capillaries occurs, and the V/Q ratio approaches 1
What kinds of organisms would thrive in the apex of the lung?
Aerobes like TB
A V/Q of/near zero suggests what?
airway obstruction (shunt). I.e. foreign body aspiration
In a shunt, 100% O2 WILL NOT improve PaO2
A V/Q of/near infinity suggests what?
blood flow obstruction (i.e. pulmonary embolism)
In this case 100 O2 WILL improve PaO2
What are the pressure ratios in the apex of the lung?
PA > Pa > Pv
What are the pressure ratios in the middle of the lung?
Pa > PA > Pv
What are the pressure ratios in the base of the lung?
Pa > Pv > PA
How is Co2 transported from tissue?
as HCO3- (90%)
Dissolved CO2 (5%)
Describe venous transport of Co2 via carbaminohemoglobin
In this case Co2 is bound to Hb at the N-terminus of globin (not heme).
How is Co2 converted to HCO3?
. CO2 released from tissue enters RBCs where carbonic anhydrase converts it to H2CO3, which then dissociates to H+ and HCO3-. HCO3- leaves the cell in exchange for Cl-
Study more about Haldane, Bohr, and other effects of Co2, O2 exchnage in hemoglobin
How does the body respond to high altitude?
decreased PiO2 leads to decreased PaO2 leading to increased ventilation, pushing off more PaCO2 leading to a short state of respiratory alkalosis. The kidneys then respond by pushing off HCo3-
Study more from pulm
How else does the body react to altitude?
EPO increases and 2,3-BPG also increases to improve O2 unloading at tissues due to the hypoxia
The lungs respond to hypoxia by vasoconstricting which can lead to pulmonary hypertension
How do the lungs respond to exercise?
CO2 production increases, as does O2 consumption, leading to ventilation increasing and V/Q ratios throughout the lung becoming more uniform
How do PaO2 and PaCo2 change in exercise?
They dont, but there is an increase in venous Co2 content and a decrease in venous O2 content