Resp- Lecture 1&2 Flashcards
What do we mean by respiration?
Transport of osygen from ambient air to cells in the tissues and transport of CO2 out of tissues to ambient air
Why do we need a respiratory system?
Surface to volume ratio
The bigger you get, bigger problem of getting oxygen in and co2 out
What is Stage 1 of respiration?
Ventilation
Moving of air in and out.
What is 2nd stage respiration?
Pulmonary gas exchange from alveoli into pulmonary capillaries (diffusion)
What is 3rd stage respiration?
Gas transport form pulmonary capillaries to peripheral
What is 4th phase of respiration?
Peripheral gas exchange form tissue capillaries into cells
Stage 5 respiration?
CO2 back again, but not considered one of the stages
Job of lung?
- Conduciton of air
- diffusion of gas
- transport
- metabolism
- defense
What is the conducting zone?
Upper airway until generation 17
What is the transitional and respiratory zones?
Beyond generation 17
How does strucutre of airway change down to alveoli?
Thicker, stiffer airways at upper aiways
Thinner, more flexible airways as you go down
Each generation, the airway gets smaller but cross sectional area increases greatly
As gas moves down the airway, cross secitonla area _____ significantly and pressure therefore _____ which lead to a _____ in velocity of flow
increases; decreases; reduction
The decrease velocity of flow of air provides what?
Milieu for gas exchange (environment for gas exchange)
Flow=
volume/time
The whole respiratory system is driven by ____ ____
pressure gradient (gas or air flow)
Flow also =
change in pressure/resistance
Pressure=
force/area
Flow is ____ in conducting zone (Trachea and bronchi)
fast
Bigger the delta P does what to flow?
Higher propensity to flow
What is diffusion?
passive mvmt of particles from high to low concentration gradient
What is fick’s law?
Rate of diffusion of gas across permeable membrane depends on:
Vgas ≈ A/T . D . (P1-P2)
A= surface area
T-thickness of membrane
D= diffusion coefficient
P1 and P2= Pressure on either side of membrane
What is the conducting zone of the lung?
Comprises of trachea, bronchi and teminal bronchioles (smallest airways without alveoli)
- Conduct inspired air into gas exchanging regions of the lung
- Take no part in gas exchange
- constitute the anatomical dead space
- volume of 150 mL in each breath
What is the respiratory zone?
Comprised of respiratory bronchioles (which have occasional alveoli budding from walls) and alveolar ducts (completely lined with alveoli)
- Makes up most of lung
- 2.5-3 L at rest
Gas exchange occurs predominantly during ____
expiration
How thick is the alveolocapillary membrane? What does it consist of?
0.5 um thick
- Consists of alveolar epithelium on air side
- Endothlium on capillary side
- Interstitium lies between 2 membranes
What is distance of barrier between blood and air?
1um
Alveoli are “bathed in blood”
What is type 1 pneumocytes?
Flat avleoli cells
Make up majority of SA of alveolus
What are type II pneumocytes
Biochemistry center of alveoli (SEcrete surfactant)
Which diffusion limitation do you see first?
O2. 20X less able to diffuse
What is diffusion coefficient dependant on?
D= Sol/√MW
D= diffusion coefficient
Sol- solubility coeffeicient of gas
MW= molecular weight
The lung is a ____ for blood
reservoir
Why can pressures be lower in lung?
Becaues resistance is lower, so doesn’t need as much pressure to create flow
What happens to extraalveolar vessels as lung volume increases?
- Traction of the extraalveolar vessels as lung volume increases causes distention of extraalveolar vessels
- This reduces resistance within them
- Extra alveolar vessel resistance increases with decreased lung volume
What happens to alveolar vessels as lung volume increases
- Alveolar vessels are compressed by inflation of alveoli
- Therefore, capillary (alveolar vessel) resistance increases with increased lung volume
What happento lung resistance as lung volume increases?
- From very low lung volume, resistance slowly falls as result of effects on extraalveolar vessels, but as inflation continues, resistance begins to rise as alveolar vessels are compressed
What is significance of low point on resistance curve?
Functional residual capacity
Extra alveolar blood vessels have ___ resistance at high lung volumes and ___ resistance at low lung volumes
Low;
high
Alveolar blood vessels have ___ resistance at low lung volumes and ____ resistance at high lung volumes.
low; high
What is pulmonary vascular resistance?
Sum of resistance in both alveolar and extra alveolar vessels
Do we utilize all capillaries in lungs all the time?
No
What happens to capillaries in lung in order to increase blood flow?
Recruitment of unused capillaries; This allows decreased resistance to increase flow during high CO states (i.e. exercise)
Hypoxemia cauess ______ in lungs
Vasoconstriction
What does nitric oxide do in lungs?
Vasodilate
What does alkalemia do to lungs?
Pulmonary vasodilator
Why don’t alveoli collapse at low lung volume?
Surfactant- this decreases surface tension so that alveoli don’t collapse upon themselves (from water inside alveoli)
Surfactant is most effective at ____ lung volumes
low
What does nitric oxide do for newborn persistent pulmonary hypertension?
- Diffuses into pulmonary vascular bed relaxing pulmonary arteries
- Binds to hemoglobin and is inactivated
- effects lmited to pulmonary vasculature
What is ACE?
Angiotensin converting enzyme. ACE is produced by lungs to generate vasoconstrictor angiotensin II
What are the roles lungs play in metabolism?
- ACE- located in small pits on capillary endothelial cells
- convert angiotensin 1 to angiotensin II
- also inactivates bradykinin, a powerful vasodilator generated during allergic responses
- Metabolizes bronchoactive substances such as leukotrienes (cause bronchospasm)
- Important resrvoir of several Cytochrome P450 enzymes (CYPS) and plays a role in metabolism of xenobiotics (foreign substances)
- 3rd most concentrated region of cyp450 (liver and gut first 2)
- Contain mast cells which produce the anticoagulant heparin
Pulmonary vascular resistance ___ with alveolar hypoxia
Increases
this is due to constriction of small pulmonary arteries
What are some structural adaptations for defense in the respiratory system?
- Nose has cilia which filter large particles and generate a sneeze. Particles over 25 mm are filtered out in nose and nasopharynx
- Cough and gag reflex prevent us from inhaling/aspirating nasopharyngeal secretion or food particles
- ciliated columnar epithelium of bronchial tree have mucous glands and goblet cells which secrete mucous
- the cilia beat to propel mucous towards oral cavity, like an escalater
- this allow particles to be carried up to be coughed up or swallowed. particles grater than 25 mm are cleared in this way
- Particles reaching alveoli are removed by macrophages and end up in regional lymph nodes
- cellular immune responses unique to lung exist. When over activated, these cause asthma
What is boyle’s law?
PV @ constant (K)
As pressure decreases, volume increases
What causes air to move as we breath?
Boyle’s law
Inspiration is ____
Active
- Diaphragm moves down, ribs move forward upward and outward
- V in chest increases
- P in chest decrease
- Air flows into lung down a pressure gradient
Expiration is _____
Passive
- Due to elastic recoil of chest
- V in chest decreases so P increases
- Air flows out passively down the pressure gradient
Can expiration be active?
Yes
Wind instrument, asthma, uses the muscles of abdomen and internal intercostal muscles
What are principle muscles of inspiration
- External intercostals (elevate ribs)
- Interchondral part of internal intercostals (elevate ribs)
- Diaphragm )domes descend increasing longitudinal dimension of chest and elevating lower ribs
What are accessory muscles used in inspiration?
- Sternoclediomastoid (elevate sternum)
- scalenes anterior middle and posterior (elevate and fix upper libs)
What muscles contribute to active breathing?
- Internal intercostals except interchondral part
- Abdominal muscles
- Rectus abdominis
- external oblique
- internal oblique
- transversus abdominis
What does bulk flow depend on?
Pressure gradient
size and resistance of conduit
nature of the fluid
Most flow of air in lungs most of the time is _____
transitional (combination of laminar and tubulent)
Pouiseuill’s law?
Resistance =? Based off of which law?
Q=∆Pπr4/(“η” 8L)
Resistance=(“η” 8L)/πr4
Based on Ohm’s law (flow= change P/Resistance)
Halving the radius increases resistance by how much?
16-fold
How can we influence airway resistance?
Reduce gas density
- Heliox He: O2 - 80:20
- Heliox reduces the pressure gradient needed to sustain flow by making the gas less dense
- this helps to decrease work of breathing in pathological conditions where flow is turbulent
Where does turbulent flow occur in lungs?
At branch points in the lung
How do we calculate reynold’s number? What does it signify?
REYNOLD’S NUMBER = 2rvd
h
r = radius
v = velocity
d = density
h = viscosity
- Reynolds >2000= turublent
- Reynolds <2000= laminar
What happens in turbulent flow?
- Less axial velocity than laminar flow
- more work to drive flow
- Reducing density of gas can reduce work
- heliox helps convert turbulent flow to laminar flow
- used to treat upper airway obstruction
Where does most resistance occur in airways?
Most resistance occurs up to 7th generation
What factors affect airway resistance?
- Lung volume
- Greater volume, lower resistance. As long volume decreases, lung callapses and airway resistance increases
- Bronchial smooth muscle
- contraction increases resistance (parasympathetic activity)
- B2 andrenergic causes smooth muscle relaxation
- Density and viscosity of inspired gas
- as gas density increases, airway resistance increases
- Dynamic compression of airways- forced expiration
- choke point- increaed intrathoracic pressure during forced expiration makes expiration effort independent. Your compressing airways, therefore there is increased resistance, and no matter what effort you make, there’s no increase in flow out of lungs
What is dynamic compression of airway?
- With forceful expriation, flow is determined by aleveolar pressure- plural pressure and so is independent of effort
- function of quality of airways, not effort
Aiway resistnace is ____ during expiration at the choke point
maximum
What is compliance?
- Measure of distensibility of lung and is inverse of lung elastance
- How easily can the tissue expand
- Change in volume for a given change in pressure
- Compliance= change V/ change in P
What is elastance?
Ability of lung to recoil back to previous shape after distended
What conditions cause increased compliance?
Aging
Emphysema
What conditions cause decreased compliance?
Pulmonary fibrosis
Alveolar edema
Hypoventilated lung
increased pulmonary venous pressure
What happens in pneumothorax?
Air into pleural space, loss of negative pressure
- loss of mechanical linkage between chest and lung
- lung collapses
- lung cannot be inflated by forced respiration
- air need to be let out via chest tube and vacuum
What is functional residual capacity?
- Volume of lung at which elastic recoil of lung pulling inwards and tendnecy for chest wall to spring out (elastic recoil of thoracic rib cage) are at equilibrium
- Volume in lung stays there, keeps lung open and acts as bank to supply o2 when needed
- keeps lungs open and intrapleural pressure negative
What is hysteresis?
- Slope of line differs between inspiration and expiration
- At given pressure, volume is lower durign inflation than during deflation
- Due in part to presence of surfactant
What are type 1 pneumocytes?
- Large, flattened non replicating
- Involved in gas exchange
- Diffuse alveolar disease seen in SARS epdiemic
Type II pneumocytes can _______ into Type I but not vice versa
Differentiate
What are regional difference in ventilation?
- Apex volume is large
- Apex pressure is low
- Not much room for expansion
- Base pressure is high
- Base volume is decreased
Thus ventilation/unit volume is increased at the base vs apex
Apex is ____ better at baseline as surrounding intrapleural pressure is more ___ at apex
aerated; negative
Apex’s ____ is greater compared to compressed base due to effect of gravity
volume
What are factors that affect resistance to airflow?
- The dimensions and content of the airways
- The structure and quality of tissue
- The degree of vascular distension
- The composition (viscosity and density) of the inspired air
- The mechanical properties of the chest wall
What are factors that affect lung compliance?
- Volume: compliance increases with decreasing lung volume
- Hysteresis: lung demonstrates different complicance curves during inspiration and expiration. Lung volume at any given pressure is higher during deflation than during inflation
- Elasticity of lung
- Surfactant
- increases compliance of lung
- promotes stability of alveoli
- keep alveoli dry
- prevent redution in hydrostatic pressure in tusse around capillaries
- also contribues to hysteresis
- Vascular distention: engorgement of lung causes increased stiffness, decreased compliance
How is chest wall compliance different than lung compliance?
- Chest wall is much more compliant at high lung volumes than the lung
- resting volume of thorax is much higher than the lung
At very low lung volumes, there is reduced recoil at base of lung and pleural pressure may even be positive. In this situation, the ___ ventilates better
apex
At normal lung volumes, ventilation (change in volume iwth inspiration) is greater at the ____
base
