Respiratory Flashcards
Anatomic dead space:
Conducting zone (nose, pharynx, trachea, bronchi, bronchioles, terminal bronchioles)
Conducting Zone:
Nose, pharynx, trachea, bronchi, bronchioles, terminal bronchioles
- ->anatomic dead space (no gas exchange here)
- ->warms, humidifies, filters air
Respiratory zone:
Respiratory bronchioles, alveolar ducts, alveoli
–>participates in gas exchange
What parts of the respiratory tree contain cartilage?
–>Trachea and Bronchi
What part of respiratory tree contains goblet cells?
goblet cells extend to the bronchi
Type I vs Type II pneumocytes:
- cell type?
- functions?
- Type I: cover about 97% of alveolar surfaces
- ->line alveoli
- ->squamous cells
- ->thin for optimal gas diffusion
- Type II: only cover about 3% of alveolar surfaces
- ->secrete surfactant (dipalmitoyl phosphatidylcholine)
- ->cuboidal cells
- ->precursors to both type I and other type II pneumocytes
- ->proliferate during lung damage
Dipalmitoyl phosphatidylcholine
= pulmonary surfactant
Clara cells
nonciliated, columnar secretory cells
- ->secrete component of surfactant
- ->degrade toxins
- ->act as reserve cells
Lecithin:Sphingomyelin ratio:
-significance? what’s a significant ratio?
L:C ratio > 2.0 in amniotic fluid –> indicates fetal lung maturity
What forms the Diffusion/Gas-exchange barrier between the capillary lumen and alveolar space?
- Endothelial cells (tight junction)
- Type I epithelial cells
- Basement membrane
How far down respiratory tree are there ciliated cells (pseduostratified ciliated columnar cells)?
–>ciliated cells extend to the respiratory bronchioles
Which lung is more common site for an inhaled foreign body? why?
–>Right lung; b/c right main bronchus is wider and more vertical than left
Which lung has 3 lobes? 2 lobes? lingula?
right lung –> 3 lobes
left lung –> 2 lobes + lingula (homologue of right middle lobe); left lung needs space for the heart!
Which nerve/roots innervate diaphragm?
Phrenic: C3, C4, C5 keep the diaphragm alive!
Pain from diaphragm may be referred to where?
shoulder
Structures that perforate the diaphragm (and the levels at which they do so):
“I (IVC) ate (8) ten (10) eggs (esophagus) at (aorta) twelve (12)
- T8: IVC
- T10: Esophagus + vagus
- T12: Aorta + thoracic duct + azygous vein
***T12: Red, White, and Blue –> Aorta (red), Thoracic duct (white), Azygous vein (blue)
Which part of breathing is passive: inspiration or expiration?
- ->expiration=passive
* inspiration uses the diaphragm!
3 functions of surfactant:
- decrease alveolar surface tension
- increase compliance
- decrease work of inspiration
5 lung products:
1) Surfactant
2) Prostaglandins (relax bronchi)
3) Histamine (increases bronchoconstriction)
4) ACE (ang I–>ang II; and inactivates bradykinin)
5) Kallikrein (activates bradykinin)
Equation for Collapsing Pressure = P =
P= (2 X surface tension) / radius
***smaller radius–> increased tendency to collapse on expiration (law of Laplace)
Kallikrein:
Product of the lungs
–>activates bradykinin (vs ACE, also a product of the lung, which inactivates bradykinin!)
Prostaglandins vs Histamine:
- ->both are products of the lung
- Prostaglandins –> relax bronchi
- Histamine –> stimulates bronchoconstriction
Are alveoli with smaller or larger radii more likely to collapse during expiration, without surfactant?
–>smaller radius–> more likely to collapse without surfactant
Vital Capacity =
VC = TLC - RV = IRV + TV + ERV
–>it’s maximal inspiration and expiration
Inspiratory Capacity =
IC = IRV + TV
–>maximum amount that can be inspired
Functional Residual Capacity =
FRC = ERV + RV
–> amount of air in lungs after a normal, tidal volume, expiration
Total Lung Capacity =
TLC = IRV + TV + ERV + RV
Calculation of Physiologic Dead Space = VD= ?
VD = [VT X (PaCO2 - PeCO2)] / PaCO2
“Taco Paco Peco Paco”
- VD = physiologic dead space = anatomic dead space (conducting zone) + functional dead space in alveoli; it’s the volume of inspired air that doesn’t participate in gas exchange
- VT = Tidal Volume
- PaCO2 = arterial PCO2
- PeCO2 = expired air PCO2
Which part of a healthy lung is the largest contributor to functional dead space?
–>Apex of healthy lung
Natural tendency of lungs and chest wall:
Lungs want to collapse inward
Chest wall wants to spring outward
Lung and Chest wall at FRC:
At FRC (Functional Residual Capacity--> after a normal expiration): inward pull of lung is balanced with outward pull of chest wall; system pressure is atmospheric -->have negative intrapleural pressure at FRC; both airway and alveolar pressure = 0
What is compliance? How does it relate to FRC? What conditions are associated with decreased compliance?
Compliance = Change in lung volume for a given change in pressure
*decreased compliance –> decreased FRC
- Decreased compliance in:
- pulmonary fibrosis
- insufficient surfactant
- pulmonary edema
Adult hemoglobin, Fetal hemoglobin composition?
Adult Hb: 2alpha, 2beta subunits
Fetal Hb: 2alpha, 2gamma subunits
R and T forms of Adult Hb:
- T form = Taut form = “Tissue form” –> has low affinity for O2; so increased O2 unloading into tissues… Right shift of Oxygen-Hb dissociation curve in T form (Increased Oxygen unloading)
- R form = Relaxed form –> high affinity for O2
What conditions favor the T (taut) form of Hb?
- ->anything that shifts Oxygen-Hb curve to right (increased O2 unloading):
- increased temperature
- increased 2,3-BPG
- increased H+ (decreased pH)
- increased Cl-
- increased CO2
How does Fetal Hb differ from adult?
–>Fetal Hb has decreased affinity for 2,3-BPG than adult Hb, so has higher affinity for O2 (less O2 unloading)
Methemoglobin:
= Oxidized form of Hb (Ferric, Fe3+; normally iron in Hb is in a reduced state –> ferrous, Fe2+ (Ferrou2))
*Methemoglobin has increased affinity for Cyanide; decreased affinity for O2
Ferric vs Ferrous state of iron in Hb:
Ferric = Fe3+ –> oxidized form = Methemoglobin
Ferrous = Fe2+ –> reduced form of iron; normal form of Hb; binds O2 well
Treatment for Methemoglobinemia:
- Methylene Blue
- Vitamin C
Treatment for Cyanide Poisioning:
-Nitrites (oxidize Hb to Methemoglobin–> has increased affinity for CN-, so Hb binds cyanide –> allows cytochrome oxidase to fxn)
Then, give:
-Thiosulfate –> binds cyanide forming thiocyanate, which is renally excreted
Carboxyhemoglobin:
- ->Hb bound to CO instead of O2
- decreases oxygen-binding capacity and decreases oxygen unloading to tissues (Left shift in Oxygen-Hb dissociation curve)
***CO has 200X greater affinity than O2 for Hb!!!
Factors that cause a Right shift in the Oxygen-Hb dissociation curve:
“C-BEAT”
- increased CO2
- increased 2,3-BPG
- Exercise
- increased Acidity (increased H+, decreased pH)
- increased Temperature
How does the presence of CO affect Hb saturation?
Have increased Hb saturation at any given PO2 in the presence of CO, b/c of positive cooperativity
Normal resistance and compliance in pulmonary circulation:
Low resistance, High compliance (normally)
Effect of decreased PAO2
Hypoxic VasoCONSTRICTION (shifts blood away from poorly ventilated parts of lung to well-ventilated parts of lung)
Perfusion-limited vs Diffusion-limited Pulmonary circulation:
- Diffusion-limited: based on how much blood is flowing through (increased blood flow –> increased diffusion)
- Diffusion-limited: based on gas exchange (ie in emphysema, fibrosis–> decreased gas exchange)
Equation for Diffusion = Vgas = ?
Vgas = (A/T) X Dk(P1-P2)
A=Area
T=Thickness
Dk(P1-P2) = difference in partial pressures
- **decreased A in emphysema
- **increased T in fibrosis
- ->SO: both of these conditions lead to decreased diffusion
Normal pulmonary artery pressure?
10-14 mmHg
Pulmonary hypertension: pulmonary artery pressure?
> or = 25 mmHg
Results of pulmonary HTN (how does it affect pulmonary arteries?):
- Atherosclerosis
- Medial hypertrophy
- Intimal fibrosis
BMPR2 (Bone Morphogenic Protein Receptor type 2)
genes that is mutated in primary pulmonary hypertension (it is inactivated)
BMPR2 gene normally inhibits vascular smooth muscle proliferation; but, in primary pulmonary HTN it is inactivated… so get excess vascular SM proliferation
–>poor prognosis
Cause of primary pulmonary HTN?
inactivating mutation of BMPR2 gene (get excess vascular smooth muscle proliferation)
Causes of secondary pulmonary HTN?
- COPD (destruction of lung parenchyma)
- Mitral stenosis (increased resistance in left heart –> get increased pressure which backs up into the lungs)
- Recurrent thromboemboli (results in decreased cross-sectional area of pulmonary vascular bed)
- Autoimmune disease (inflammation–> intimal fibrosis –> medial hypertrophy)
- Left to Right shunt in the heart
- sleep apnea or living at high altitudes (hypoxic vasoconstriction)
Course of progression of pulmonary HTN:
severe respiratory distress –> cyanosis and RVH –> decompensated cor pulmonale, resulting in death
Pulmonary Vascular Resistance equation: PVR = ?
PVR = (Ppulm artery - PL atrium) / CO
- Ppulm artery = pressure in the pulmonary artery
- PL atrium = pulmonary wedge pressure
- CO = cardiac output
- **R = delta P/Q
- -> Resistance = change in pressure / Flow
***Resistance is proportional to viscosity and vessel length; inversely proportion to radius^4
Oxygen content of blood = ?
O2 content = (O2 binding capacity to Hb X %saturation of Hb) + dissolved O2
When have decreased Hb (ie anemia), how does it affect:
- O2 content of arterial blood?
- O2 saturation?
- arterial PO2?
- decreased O2 content of arterial blood
- NORMAL O2 saturation and arterial PO2
How does exercise affect PO2?
Exercise decreases venous PO2 (makes sense –> have increased delivery of Oxygen to tissues, so less O2 in VENOUS blood going back to the lungs)
How does chronic lung disease affect PO2?
Have decreased PO2 in arterial blood (makes sense, b/c have decreased diffusion of Oxygen into blood in the lungs, so less oxygen in the arteries…)
Oxygen delivery to tissues = ?
O2 delivery to tissues = CO X O2 content of blood
Alveolar gas equation (approximate): PAO2 =? (know!!! :))
PAO2 = 150 - PaCO2/0.8
*note: this is an approximation (if pt has increased O2 - like an oxygen mask - then >150; if pt has decreased O2 - like high altitude - then <150)
- PAO2 = alveolar PO2
- PaCO2 = arteriolar PCO2
A-a gradient (Alveolar-arterialor gradient) =
A-a gradient = PAO2 - PaO2
*should = 10-15 mmHg
–>Increased A-a gradient is BAD! Get increased A-a gradient in hypoxemia (have oxygen in alveoli, but not making it into arterioles) –> may be d/t a shunt in the heart (so, oxygenated blood sent back to lungs), V/Q mismatch, fibrosis (impairs diffusion), etc…
Hypoxemia vs Hypoxia vs Ischemia:
- Hypoxemia = decreased PaO2 (arterial O2)
- Hypoxia = decreased O2 delivery to tissues
- Ischemia = Loss of blood flow
4 ways to get Hypoxemia (Low PaO2):
1) alveolar hypoventilation (have a normal A-a gradient though, b/c diffusion, etc, is not the problem)
2) V/Q (ventilation/perfusion mismatch)
3) Diffusion impairment
4) Right –> Left shunting in the heart
V/Q (ventilation/perfusion):
- ideal ratio = ?
- ratio at apex of the lung = ?
- ratio at base of the lung = ?
- ideally, V/Q = 1 (matched ventilation and perfusion)
- Apex of the lung: V > Q –> V/Q = 3 (have wasted ventilation; have more air in apex than blood –> why TB looooves it :))
- Base of lung: V < Q –> V/Q = 0.6 (wasted perfusion; have more blood than air; BOTH V and Q are increased at the base; BUT, Q increases more than V, so get lower V/Q ratio)
V/Q ratio during exercise?
V/Q ratio approaches 1 during exercise/increased CO (b/c have vasodilation of apical capillaries, so higher Q/perfusion)
V/Q ratio in airway obstruction/shunt?
V/Q approaches 0
b/c can’t ventilate… even if give 100% O2, won’t help
V/Q ratio in blood flow obstruction/physiologic dead space?
V/Q approaches infinity
(b/c very little perfusion, low Q; is helped if given 100% O2, if there is some part of the lung that can undergo diffusion/is perfused)
Form in which most blood CO2 is transported?
CO2 is carried as bicarbonate in the plasma
3 forms that CO2 is transported from tissues to lungs:
1) Bicarbonate (90% is transported this way! carried in the plasma)
2) CO2 bound to hemoglobin at N-terminus; CO2 binding to Hb favors the Taut formation of Hb (favoring O2 unloading) (about 5%)
3) Dissolved CO2 (about 5%)