REsp Flashcards
What is Resp
: Metabolic processes in which oxygen (O2) is used to oxidize nutrients to produce energy in the form of ATP, generating carbon dioxide (CO2) at the cellular level…
The transport of oxygen from the ambient air to the tissue cells and the transport of CO2 in the opposite direction
a combination of airflow, and gas exchange (followed by blood flow and gas exchange).
Name the stages of resp
- Stage 1 Ventilation from the ambient air into the lung (pulmonary) alveoli
- Stage 2 Pulmonary gas exchange from the alveoli into the pulmonary capillaries
- Stage 3 Gas transport from the pulmonary capillaries to the peripheral (tissue) capillaries
- Stage 4 Peripheral gas exchange from the tissue capillaries into the cells (mitochondria)
- Stage 5 …and CO2 back again, though this is not usually considered to be one of the stages…
What causes gas flow for resp to happen
A pressure gradient is established between the atmosphere and the lung, and gas flows in response to it
What is pressure
Force/Area
What is flow
Flow = Rate of change of volume or Volume/unit time
As Gas moves down the airway what happens to the cross sectional area
It Increases
What happens to pressure and velocity when the cross sectional area increases
pressure reduces and velocity reduces
What factor is necessary for Gas molecules to move
Force
What kind of flow does air flow occur by
Bulk flow
Resistance to air flow is caused by the folloeing properties:
a function of the shape of the conduit (that which it flows through)
the properties of the substance (that which flows).
In gas exchange from the airway to blood, the properties of the interface also affect resistance to flow.
Lung functions
GAS exchange(conduction of air) Diffusion of Gas
Transport
Metabolism
Defense
Filters unwanted substances from circulation
How is the chest wall coupled with the pleural membrane
The movement of the chest wall is mechanically coupled through the plural membranes.
The lung-thorax system has a single orifice at the trachea that functions as a ?
Reciprocal pump.
sucks in air in response to negative pressure generated by the muscle of the chest wall.
How much negative pressure is needed for gas flow to happen in the lungs
2cm of water generates 1L/sec of flow by bulk flow
What happens on inspiration
the diaphragm contracts and descends, and the intercostal muscles raise the ribs and spread them apart. This increases volume of the thoracic cavity and decreases intrathoracic pressure, which ‘sucks’ air into the lungs. The air travels through the conducting apparatus.
What’s the relationship between Vol and Intrathoracic pressure upon inspiration
Increase thoracic cavity volume
Decrease Intrathoracic Pressure
The Conducting Apparatus consists of
trachea, bronchi(Segmental)
bronchioles(Nonrespiratory)
terminal bronchioles (smallest airways without alveoli).
Together, they conduct inspired air into the gas exchanging regions of the lung.
The components of the conducting zone take no part in gas exchange, and constitute the anatomic Dead Space, with a volume of about 150 ml in each breath.
respiratory zone is made up of?
Gas excnahging regions of the lungs.
respiratory bronchioles (which have occasional alveoli budding from their walls)
and
2.alveolar ducts: are completely lined with alveoli.
3.ALveolar Sac.
The respiratory zone makes up most of the lung volume, about 2.5 to 3 liters during rest
where is the narrowest part of the airway and greatest resistance to airflow
Trachea
Whats the relation between velocity of flow and area
this is Inversely related
In the alveolus what happens to air velocity
its so slow that it comes to a standstill.
Whats the benefit of the velocity of air flow slowing down when it reaches the alveolus
Rapid diffusion of gases hapens here.
During which cycle of Respiration does gaseous exchange happen
During Expiration
The airway becomes shorter and numerous as it gets further into the Lungs True or false
T
From 17th generation we have a combined function of transitional and respiratory zones
The alveolocapillary membrane Consist of?
The alveolocapillary membrane is the thin structure dividing air from blood.
It is only 0.5µM thick. It consists
the alveolar epithelium on the ‘air’ side,
the endothelium on the ‘capillary’ side, and
the interstitium which lies between the two membranes
Is the flow fast or slow in conducting Zone?
Fast
The alveolar epithelium has 2 types of cells
: Type 1 cells (sunny side up, or pavement cells), and the
Type 2 pneumocytes which secrete a surface active material (or surfactant) into the alveoli
. The alveolar epithelial cells secrete the Angiotensin Converting Enzyme, which is necessary to convert Angiotensin I to Angiotensin II, an important vasoconstrictor which is necessary for sodium retention and maintenance of intravascular volume in salt and water-depleted states.
How does gas exchange happen
Across the alveolar capillary membrane by diffusion
Ficks Law
The volume of gas that flows across a sheet of tissue is proportional to the area of the sheet, and inversely proportional to its thickness, and pressure gradient across the sheet.
Thus V* (Volume of gas/unit time) is proportional to (Area /Thickness) x (P1-P2), but also depends on the properties of the gas (mainly solubility and molecular mass)
The rate of diffusion of a gas across a permeable membrane depends on:
- The nature of the membrane
- The surface area of the membrane (A)
- The thickness of the membrane (T)
- the partial pressure gradient of the gas across the membrane (DP)
- The diffusion coefficient of the gas (D)
when is diffusion most efficient
It follows that diffusion is most efficient when the blood gas interface has a large surface area, and is very thin.
How does the blood gas interface Surface area get large and thin
This is achieved by wrapping the capillaries around minute air sacs called alveoli. There are 300 million alveoli in the human lung, with a surface area of 85 square meters.
In addition, the pulmonary capillaries are of very small caliber (7µM), squeezing the Red Blood Cells (RBCs) close to the vessel wall, and decreasing the distance for diffusion.
Blood flow in the lungs comprises of
pulmonary circulation and bronchial circulation
Components of alveoli
Type 1 and 2 alveolar cells
surfactant
ALveola macrophage
Respiratory brochiole components
Mucus layer
Ciliated cell
nerve
Bronchiole component
Mucus layer
ciliated cell
Basement membrane
Trachea and Bronchus
Mucus layer
Serous cell
Goblet cells
ciliated cells
Diffusion in the lung
In the normal lung:
300 million alveoli
Barrier between blood and air is less than 1mm
Capillaries are very small so almost all RBC in contact
CO2 diffuses about 20X faster than O2
Diffusion constant
solubility/
square root of MW
The ALveolus has 2 types of cells
Type 1 and type 2 pneumocytes
Relationship between Alveolo capillary membrane and diffusion
Alveolo-capillary membrane is usually very thin (0.3 – 0.5 mm) but can thicken in various disease states which can reduce oxygen diffusion….this may increase with disease.
Interstitial space gets thicker….u have to be sicker to be able to mess this up.
Diffusion of CO2 usually not impacted but can be by very serious disease states.
What are Macrophages used for
Defence in the Lungs
TRansport:
Components of pulmonary circulation
1.The lung is a reservoir for blood
Receives almost all cardiac output
2.Low resistance circuit
Pressure=Flow x resistance and since resistance is low, the pressure gradient can also be low to get good flow (F=(P)/R)
3.The alveoli are essentially “bathed in blood “: efficient gas exchange
Low pressure circuit
Explain blood flow and gas exchage in the capillary
As pulmonary vascular resistance is so low, a mean pulmonary arterial pressure of only 20 cm water (15 mmHg) is needed for a flow of 6L/min, which is the Cardiac Output, and also the RV output into the lung, as the 2 systems are in series. (Fig. 5.)
Blood flows rapidly into the pulmonary capillaries, which form a dense network in the walls of the alveoli. The branches are so short, that they virtually form a pool of blood, bathing the alveoli. This provides a very efficient milieu for gas exchange
Factors affecting the caliber of pulmonary vessels or pulmonary Vascular resistance /pulmonary circulation
1.pressure around them:
As the lung expands extra alveolar vessels are pulled open by the traction of expanding lung parenchyma.
their resistance fall with inflation
2.Alveolar vessels(capillaries)resistance increase at High volume as the lungs expands because they are compressed by the high pressure generated because of the lung expansion.
Increase vol=Inc alveolar vessel Resistance
- At low lung volumes, the extra alveolar vessel resistance increases significantly Because pressure is up.. If a lung is completely collapsed, pulmonary artery pressure has to be raised to several cms. above downstream pressure before any flow will occur; this is called the critical opening pressure.
Pulm vascular resistance is reduced by inc blood flow
During Exercise when CO and pulm blood is increased.
- Pulmonary vascular resistance increases with alveolar hypoxia, due to constriction of small pulmonary arteries
- Pulmonary vascular resistance can be decreased with Nitric Oxide, which is a powerful selective pulmonary vasodilator, and is used to treat pulmonary hypertension. Useful in neonatal pulmonary hypertension due to prematurity
Acid base status: Alkalemia is a pulmonary vasodilator
What is critical opening pressure
. If a lung is completely collapsed, pulmonary artery pressure has to be raised to several cms. above downstream pressure before any flow will occur
PVR maybe reduced by
Increased blood flow.
this is called recruitment
this is occurs because of capillary distention
and opening of capillaries which are normally ‘closed’: no blood flows through them at rest.
At what instances does recruitment occur and what happens
During Exercise when CO and pulm blood is increased.
How does pulmonary veins impact Bronchial Circ
Carries deoxygenated blood away from the lungs
Which pneumocytes produce surfactant
type 2 pneumocytes which line the alveoli
surfactant and function
Surfactant decreases surface tension in less expanded lungs, enhancing alveolar stability, and preventing collapse at low lung vol
Produced by type II pneumocytes Reduces surface tension Effect is greatest at low lung volumes Contributes to hysteresis Lack results in RDS in premature babies
PVR is a sum of Which 2 components and what happen in each components as lung expands
Extra-alveola and alveola resistance.
As the alveoli expand the large extra-alveolar vessels are stretched:
Resistance goes down
As the alveoli expand the thin alveolar blood vessels get thinner: Resistance goes up
What is surface tension
Surface tension: The elastic tendency of a fluid surface which makes it acquire the least surface area possible
Surface tension exerts a force that would tend to collapse the alveoli at low lung volume
Treatment of persistent Pulmonary hypertension of the newborn
nitric oxide diffuses into pulmonary vascular bed relaxing pulmonary arteries,then rapidly binds to hgb and is inactivated .
Effects are thereby limited to the pul vasculature.
Lung metabolism involves
Metabolism of vasoactive substances: Produces Angiotensin Converting Enzyme (ACE), which generates vasoconstrictor Angiotensin II
Metabolizes bronchoactive substances such as leukotrienes (which cause bronchospasm)
Is an important reservoir of several cytochrome P450 enzymes (CYPs) and plays a role in the metabolism of xenobiotics.
Contains mast cells which produce the anticoagulant heparin…stops clots from getting bigger when formed in the lungs
which lung part has most alveoli
Alveolar duct
What happens during inspiration
Diaphragm contract and descend/ribs are raised
Components of resp zone
resp bronchioles.
alveolar duct
alveolar sac
Whats the chief mode of ventilation after velocity of gas becomes small when it gets to the resp zone
Gaseous diffusion
The Whole output of the right heart hoes to the lungs t/f
T
What secretes mucus in the lungs
mucous glands and Globet cells in the bronchial wall and swept away by the cilia.The alveoli have no mucus cells and particles there are engulfed by the macrophages
The foreign material is then removed from the lung via the lymphatics or the blood flow
The mucociliary escalator protects the lung from inhaled particles
Can be overcome as in black lung
Production of IgA – Important first line of defense
What causes air to move
Inspiration is active
The diaphragm moves down, the ribs move forward, upward and outward
Volume in the chest increases
P decreases
Air flows into the lung down a pressure gradient
Is Expiration active or passive
Passive Due to elastic recoil of the chest wall V in the chest decreases so P increases Air flows out passively down the pressure gradient
Examples of Active Expiration
Wind instrument
Asthma
Uses the muscles of the abdomen and internal intercostal muscles
Whats the main factor producing inspiration during normal breathing
Contracttion of the diaphragm
What is characteristics of bulk flow
depends on pressure gradient, size and resistance of the conduit and the nature of the fluid
Characteristics of Laminar flow
Smooth, high velocity, streamlined
Charcateristics of Turbulent flow
: Branch points, increased airway resistance – asthma – velocity is reduced and more pressure is required to drive flow
Transitional flow
Less axial velocity than laminar flow
More work to drive flow
Reducing the density of the gas can reduce work
Heliox: Helium:Oxygen 80:20 can convert turbulent flow to laminar flow
Used to treat upper airway obstruction: Croup and Asthma
This makes the gas less dense
It follows that when velocity of flow is high, as occurs in the trachea during exercise, turbulence increases
Transitional flow
At branch points
When radius is Halved what happens to resistance
Increases 16fold
Flow falls 16 fold if pressure is constant
Reduce gas density
Heliox: He:O2 - 80:20 for a child in croup.
Doubling the lenght does what to the resistance
Doubles the resistance and flow falls one half
What are the factors affecting airway resistance
Lung volume: Greater the volume, the less the AWR
Similar to effect of lung volume on extra-alveolar vessels
Airways pulled open as lung expands.
The greater the volume, the lower is the resistance, as expanding lung parenchyma exert radial traction on the airways, increase radius and thus decrease resistance. Conversely, as the lung collapses, airway resistance increases, and may even close down airways, especially at the base
Airway Generation: Most resistance occurs upto the 7th generation (determined experimentally)(highest resistance in the 7th gen)
Bronchial Smooth Muscle contraction will increase resistance. Contraction occurs in response to β2 adrenergic blockers, parasympathetic activity, acetylcholine and histamine.
b2-adrenergic agonists cause smooth muscle relaxation
b2 receptor agonists treat asthma
Terbutaline, albuterol
Density and viscosity of inspired gas During deep sea diving, the density of the gas increase, and airway resistance at the medium sized bronchi, where flow is turbulent, increases. The reverse occurs with a low density Helium O2 mixture (Heliox)
Pre-inspiration the pressure in the potential space is -5 cmH2O
Pressure difference from the airways to the intra-pleural space is always positive during normal breathing, keeping the airways open
During forced expiration, flow is determined by alveolar pressure-plural pressure (not mouth pressure) and so is independent of effort.
- 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
How does conductance relate to airway resistance
Conductance is inverse of AWR but increases linearly
During forced Expiration what determines the flow
Flow during dynamic compression is determined by the gradient between alveolar pressure and pleural pressure, not mouth pressure, as the airway is compressed
What impacts pulmonary compliance
Compliance of the lung and compliance of the chest wall together impact upon pulmonary compliance.
Whats Lung compliance
The term compliance refers to the distensibility of the lung, or the change in volume for a given change in pressure
also said to be ease with which u can change a volume for a given pressure.
Factors that affect Lung compliance
Volume: Compliance increases with decreasing lung volume.
- Hysteresis: The phenomenon by which the lung demonstrates different compliance curves during inspiration and expiration. Lung volume at any given pressure is higher during deflation than during inflation.
- Elasticity of the lung, or its tendency to return to resting position after inflation, leads to a negative pressure surrounding the lung, compared to atmospheric pressure. This elasticity is attributed to fibers of elastin and collagen in the alveolar walls, around vessels and bronchi.
4
Surfactant reduces surface tension at low lung volumes, keeping the alveoli open.
It increases compliance of the lung, promotes stability of alveoli, keeps alveoli dry. Surfactant prevents reduction of hydrostatic pressure in tissue around capillaries, prevents capillary transudation of fluid into alveoli.
5.
5. Vascular Distension: Engorgement of the lung causes increased stiffness, ie decreased compliance
conditions that increase compliance
Aging
Emphysema
Conditions that decrease compliance
Pulmonary Fibrisis Alveolar Edema Hypoventilated lung Increased pulmonary venous pressure Atelectasis
Pneumothorax characteristics and treatment
Stab wound allowing air to enter
Loss of mechanical linkage between chest and lung
Lung collapses
Lung cannot be inflated by forced respiration
Let air out of the pleural space with a chest tube and vacuum.
Relationship between FRC and and airway pressure.
At volumes above FRC, the airway pressure is positive. The chest wall tends to expand at volumes upto 75% of vital capacity.
At volumes below FRC, airway pressure is negative, and hence air is sucked into the lung, to maintain FRC.
What is FRC and application
The volume of the lung at which the elastic recoil of the lung pulling it inwards, and the tendency for the chest wall to spring out, are balanced
The volume in the lung, which stays there, keeps the lung open and acts as a bank to supply O2 when needed
Keeps the lung ‘open’, keeps intra-pleural pressure negative
Applied : Incentive Spirometry maximizes FRC, prevents lung collapse
Tye 1 pneumocytes and function
Large, flattened, non replicating
Involved in gas exchange
Diffiuse Alveolar Disease (DAD) seen in SARS epidemic
Type II Pneumocytes is the( biochemical engine of the lungs)
can differentiate into Type I but not vice versa
Compare Apex and BAse pressure and volume during ventilation
Apex volume is large
Apex pressure is low
Not much room for expansion
However,
Base pressure is high
Base volume is decreased
Thus ventilation/unit volume is increased at the base vs apex
What happens with Baseline ventilation of Apex
Apex is aerated better at baseline, as surrounding intrapleural pressure is more negative at the apex
Apex at baseline
Its VOLUME is greater, compared to the compressed base (By Boyle’s Law) due to the effect of gravity
bAse volume changes
Per unit volume, ventilation (or CHANGE in volume with inspiration) is greater at the base at normal lung volumes
What happens at low lung vol with ventilation of the apex.
At very low lung volumes, there is reduced recoil at the base of the lung, pleural pressure may even be positive
In this situation, apex ventilates better
whats the vol of air that enters the lungs with each respiration
500ml
What is FRC
The volume of gas in the lung after a normal expiration is the functional residual capacity (FRC).
Residual vol
gas remained in the lung after a maximal expiration; this is the residual volume.
Residual volumes cannot be measured by spirometry t/f?
T
What can be used to measure residual volumes and
Total lung capacity, functional residual capacity, and residual volume
Gas dilution method/with spirometer connected to helium
body plethysmograph
Exhaled vol after taking a max inhalation and max exhalation is called?
Vital capacity
What can be used to measure TV and vital capacity
Simple spirometer
Helium is used to chaeck for residual capacity in blood because of its?
Low solubility in blood
If u have Sickle cell what is the component of your Hgb that causes Reduce affinity for oxygen
Valine. affinity and a shift in the dissociation curve to the right, but, more important, the deoxygenated form is poorly soluble and crystallizes within the red
Normal should have glutamic acid
What is HGB made up of?
Heme is an iron-porphyrin compound Joined to the protein globin, with 4 peptide chains 2 alpha and 2 beta : Adult Hb or HbA HbF Fetal Hb HbS Sickle Cell Hb
Abnormal Hb Met Hb, Sulf Hb do not carry O2
Properties of oxygen dissociation curve
Sigmoidal Shape
Up to P50, steep, so large amounts of O2 are taken up by tissues for a relatively small drop in alveolar / arterial pO2
Flat part at the top , binding of O2 to Hb continues at low alveolar / arterial pO2
Shift to the left : Avid binding, less release
Shift to the right : Less binding, easier release
Left shift characteristics
Alkalosis CO Lower CO2 Lower Temp Lower 2-3 DPG Avid binding, less release
Right shift characteristics
RIGHT SHIFT Acidosis Higher CO2 Higher Temp Higher 2-3 DPG Less binding, easier release
2,3-diphosphoglyceric acid (2,3-DPG) characteristics
Allosteric effector of Hb affinity for oxygen
Binding decreases affinity promoting release
Synthesis of 2,3-DPG is controlled by local pH as part of normal glycolytic pathway
High levels of 2,3-DPG during pregnancy facilitate transfer of oxygen to fetal blood as fetal Hb is much less sensitive
oxygen Dissociation curve applications
Exercising muscle is acid, hypercarbic and hot : shift to the RIGHT, and increased release of O2 to tissues
2-3 DPG increased in hypoxia, shift to the RIGHT
CO binds avidly to Hb, reduces sites available to bind O2.
Interferes with unloading too-shift to the LEFT
Whats the Haldene effect
Formation of reduced Hb (HHb) helps load CO2 in the tissues.
The presence of oxygenated Hb in the lung helps unload CO2, which can be breathed out
Difference between co2 and o2 dissociation curves
CO2 dissociation curve is more linear than the O2 dissociation curve, for a smaller pressure change of CO2, there is a relatively larger change in CO2 concentration
Concentration of hgb determines the level of co2 in the tissue t/f
T, helps load it in the tissue.
oxygen rich blood helps unload or helps dissociation
ANion Gap equation
Anion Gap = Sum of Cations– Sum of Anions
(Na + K ) - ( Bicarb + Chloride)
K inclusion is OPTIONAL
NORMAL ANION GAP = 10 – 15 (8 – 16)
Increased anion gap examples
Diabetic Ketoacidosis
Lactic Acidosis
Uremia
Methyl Alcohol poisoning
Normal Anion Gap
Renal diseases
Abnormal bicarbonate losses
From the gut
Decreased ANion gap
Decreased anion gap
Heavy Metal poisoning ( Lithium
FYI
In addition to pCO2/Bicarb buffering, proteins in the plasma and RBCs contribute to buffering capacity (e.g. Hb)
How does compensation work In Ph imbalance
If problem is Respiratory
Compensation is Metabolic
If problem is Metabolic
Compensation is Respiratory
Significance of the flat part of the Oxy dissociation curve
The flat upper portion means that even if the Po2 in alveolar gas falls somewhat, loading of O2 will be little affected.
The steep lower part of the dissociation curve means that the peripheral tissues can withdraw large amounts of O2 for only a small drop in capillary Po2. This maintenance of blood Po2 assists the diffusion of O2 into the tissue cells.
Transport of CO2 mechanism
CO2 is 20 times more soluble than O2 and 10% of gas is carried as such ..its dissolved in plasma
CO2 + H20——— H2CO3 ——- H+ + HCO3- (60% as bicarb)
Carbamino compounds CO2 + amine groups in blood proteins, including Hb account for 30%
Dissolved Co2/protein bound/bicarb(chemically modified)
what can be used to measure the anatomic dead space and whats the normal physiologic volume of the anatomical dead space
vol is 150ml
Measuring the Nitrogen conc by washout via the fowlers method with 100% oxygen.
Measuring the vol of the conducting airways down to the midpoint of transition from dead space to ALveolar gas.
What is physiologic dead space
Volume of gas that does not participate in gas exchange and does not eliminate CO2
Can be measured by Bohr’s Method
Physiologic dead space does not contribute CO2 t/f
T
What will happen to CO2 if ventilation is HALved
Co2 will double
So, monitoring arterial blood gases, specifically CO2, helps clinicians evaluate the progression of alveolar hypoventilation in impending respiratory failure
In healthy people the anatomic dead space and physiologic dead space should relate to each other as follows
Should be almost the same in healthy people
Increased physiological dead space: Asthma
Measure ANatomic dead space
Volume of air in conducting airways About 150 ml/breath Fowler’s method Individual breaths in O2 N2 in exhaled air monitored Midpoint N2 concentration determined
Alveolar co2 equilibrates with arterial co2 fast because
Alveolar CO2 equilibrates with arterial blood
CO2 is so soluble and diffuses so fast that
pACO2 = paCO2
Based on the fact that co2 is more soluble than oxygen explain what happens with High altitude,Hypoventilation and Hypercabia.
CO2 is much more soluble than O2
Diffusion is 20 times faster
Based on the above, which comes first: Hypoxemia or Hypercarbia: At high altitude?hypoxic With interstitial lung disease? hypoxic During hypoventilation? hypercarbia
CO is a toxic gas because it Binds tightly to Hgb,but it can be used to measure
Useful (in small amounts) to measure diffusion capacity because pCO does not rise since it binds to Hb as soon as it diffuses into the blood.
Transfer is diffusion limited
Used to measure diffusion capacity in cases of intestinal fibrosis, sarcoidosis, or asbestosis
what happens in high altitude with oxygen
- At high altitudes, alveolar pO2 is reduced and the gradient between air and blood is less, so rise in pO2 along the capillary is relatively slow
In relation to Ficks law with disease state what happnes to diffusion
- In diseased states, where the blood-gas barrier is thickened, as in interstitial lung disease, diffusion of O2, and more rarely, CO2 may be impaired
what are the causes of Hypoxemia
Low inspired O2, Hypoventilation
Diffusion limitation (interstitial disease)
Ventilation – perfusion inequality
Shunt
difference between Hypoxemia and Hypoxia
Hypoxemia: Low oxygen in the blood
Hypoxia: Low oxygen in a tissue
What are the the examples that gives rise to Hypoventilation
- Drugs such as Morphine, barbiturates
- Damage to chest wall
- Weakness of respiratory muscles
- Increased resistance to airflow (deep sea diving)
Hypoventilation always increases pACO2 and paCO2
Alveolar O2 = inspired O2 – “pCO2” /”R” p
Whats the relationship between Pco2 and PAo2
So as pCO2 increases alveolar O2 levels fall
Treatment?
Increase inspired pO2
If a patient has ILD and this has affected diffusion,what can we change to combat hypoxemia?
P1-P2 or DP would be the easiest
Increase the pO2 in the alveolus will increase gradient and increase arterial pO2
Explain how V/Q mismatch causes hypoxemia
Shunt refers to blood that enters the arterial system witht out going through ventilated areas of the lung
What increases the difference between Po2 Alveolar gas and P02 arterial gas
the difference can become larger during exercise,
or when the blood-gas barrier is thickened,
or if a low O2 mixture is inhaled (Figure 3-3B).
Shunt
What are the causes of a shunt ?
small amount of coronary venous blood that drains directly into left ventricle through the the besian veins
What are the causes of a shunt ?
small amount of coronary venous blood that drains directly into left ventricle through the thebesian veins
Atrial or ventricular septal defects
Patent ductus arteriosus
AV malformations
Bronchial circulation (conducting zone)
Blood that enters the arterial system without going through ventilated areas of the lung.
Does not exchange gas. No ventilation
Anatomic: Bronchial circulation (conducting zone)
Responsible for the difference between Alveolar (A) and arterial (a) pO2
Know as the A-a gradient
Normally = 5-10 mm Hg
Physiological shunt:
Perfusion of non-ventilated alveoli(airway occlusion)
Pathologic shunt:
Atrial or ventricular septal defects
Patent ductus arteriosus
AV malformations
Can hypoxemia be abolished by giving more oxygen if the patient has a shunt?
No
When 100% O2 is inspired, the arterial PO2 does not rise to the expected level—a useful diagnostic test •
If the shunt is caused by mixed venous blood, its size can be calculated from the shunt equation
What is a shunt
Blood that enters the arterial system without going through ventilated areas of the lung.
Does not exchange gas. No ventilation
What is A-a gradient?
the difference between Alveolar (A) and arterial (a) pO2.
Normally = 5-10 mm Hg
Total dead space is the sum of
Anatomic and Physiological alveolar.
What are the characteristics of VQ ratio
Normal V/Q is 1
V/Q = Infinity with Pulmonary Embolus(Dead space)
150mm oxygen beacuse there is no CO2(inspired gas point beacuase of partial pressure of oxygen same as the air that is coming into the lungs
V/Q = 0 (mixed venous point)…concentration of gases is the same as the venous return to the lungs.
Airway obstruction, Shunt..has not made it to the part of lungs that is ventilated.
V/Q < 1 leads to hypoxemia
If we have hypoxemia but A-a gradient is Normal,state what is going on and what can help
Low Inspired O2….Oxygen will help
Hypoventilation……..oxygen helps
Hypoxemia and A-a is Increased
state what is going on will oxygen help
Diffusion Limitation….oxygen helps
Ventilation-perfusion inequality….oxygen helps
Shunt…..Oxygen helps
What kind of blood do we have in arterial blood?
Arterial blood is a mixture of all the experiences that blood goes through in the heart…dead space,shunt and all that
For west Zones of the lungs what happens with ventilation and blood flow
Lesss blood flow at top/more blood flow at the bottom
For ventilation less flow at top
More ventilation at bottom
size of alveoli is bigger at top,no more room to expand,size of alveoli smaller at the bottom,room to get filled and expand.
SLide 19 lecture 4
Regional differences between ventilation and perfusion
Understand the west zones of the lungs
Apex volume is large Not much room for expansion However, Base volume is decreased More room for expansion Thus ventilation/unit volume is increased at the base vs apex
Ventilation and perfusion relation on graph
Both Blood Flow (Q) and Ventilation (V) go down moving from the Bottom to the Top of the lung
But Q goes down faster than V and Q is the denominator so V/Q goes up
Whats the location of inspiratory and expiratory neurons
Brainstem. and the control by brainstem is involuntary
Example of voluntary breathing is?
Cortical breathing
What are the effects of Intensional hyperventilation
Reduction of co2 ,hence causing…seizures ,tetany,fainting.
What are the effects of Intentional Hypoventilation
Breath holding spells in toddlers- CO2 retention, hypoxemia, syncope, seizures
Central chemoreceptors for Co2
Located in the Medulla
Sense changes in pH of CSF caused by change in pCO2
Chemoreceptors
NOT sensitive to changes in pO2 in blood
What are the respiratory response to changes in Co2
Alveolar ventilation increases with increasing pCO2 due to
Decreased pH in CSF
Whats the effects of Narcotics on MVE/Co2 Curve
Narcotics suppress respiration, and rate of change is blunted also
Reduce the slope of response to changes in pCO2…Flattens curve…
reduces MVE and hence builds up Co2
Peripheral Chemoreceptors responds in what way?
Carotid bodies Aortic Bodies Sensitive to changes in Oxygen AND CO2 Low Oxygen stimulates them Respond to arterial levels of the gas MAx response occur below a pO2 of 50mmhg.
Pulmonary stretch receptors and their characteristics
Lie between airway smooth muscle
Respond to lung distension in a sustained fashion- Slow adapting
The effect is to SLOW Respiratory frequency by
increasing expiratory time
HERING-BRUER REFLEX
Important in newborns
In adults active at HIGH tidal volumes (>1L) as in exercise
Irritant receptors and characteristics are?
Lie between airway epithelial cells
Stimulated by noxious gases, cigarette smoke, inhaled dust, cold air
Vagus- Bronchoconstriction, and Hyperpnea
Rapidly adapting
J receptors and characteristics are?
Juxtacapillary
In alveolar walls close to capillaries
Respond to chemicals in pulmonary circulation
Stimulated by fluid collections- interstitial
Vagus- slow conduction in non myelinated fibres
Rapid shallow breathing
High concentrations can cause apnea
Receptors in the bronchial C fibers
Similar to J fibres
In the bronchial circulation
Chemicals injected into bronchial circulation
Shallow breathing, bronchoconstriction and mucous secretion
Relationship between Po2 and ventilation in the setting of low Paco2
Increase in ventilation increases at a lower pO2 when the pCO2 is low
More sensitive to Hypoxemia when combined with Hypercarbia
Abnormal patterns of breathing
Cheyne stokes breathing characteristics.
Cheyne Stokes Breathing
Apnea for 10-20 seconds separated by equal periods of hyperventilation with waxing and waning tidal volumes
SEVERE HYPOXEMIA
HIGH ALTITUDES
DURING DEEP SLEEPBRAIN INJURY
whats the Response of oxygen,co2, cardiac output, Map co2, and o2, PVR,pulm blood flow, HGB dissociation curve to exercise
Oxygen consumption increases
Oxygen is supplied by increasing ventilation
CO2 production increases, blown off by increased ventilation
Mean arterial pO2 and pCO2 do NOT change during exercise
Cardiac Output and pulmonary blood flow increase.
Recruitment of pulmonary vessels decreases pulmonary vascular resistance and enhances pulmonary blood flow
Hb dissociation curve shifts to the RIGHT enhancing O2 delivery to tissues
With fetal circulation what are the changes that OCCUR At BIRTH
In Utero – Placental circulation is in parallel with peripheral tissues…
.placenta produces…2,3 dpg.
PO2 is low at 30 mm Hg
Ductus arteriosus shunts blood from the PA to the descending aorta
Newborn baby takes its first breath
Dramatic fall in pulmonary vascular resistance —
Lung expansion decreasing extra alveolar resistance
Oxygen
Increased Pulmonary Blood flow
Left atrial pressure rises, valve closes
Adaptation per oxygen to high altitude
Hypoxemia occurs at high altitude
Severe reductions in pO2 of inspired and alveolar air
Pulmonary vasoconstriction due to hypoxemia
High altitude sickness, attributed to hypoxia
Adaptation by hyperventilation in response to hypoxemia leads to respiratory alkalosis
Polycythemia due to hypoxic stimulation of erythropoietin production, and increasing red cell production
Increased 2-3 DPG, shift to the right of O2 dissociation curve, enhancing O2 release
Cheyne stoke breathing is characterized by periods of Hyperapnea to apnea true or false
True
What is Forced expiratory volume (FEV1)
Volume of gas exhaled by a forced expiration after a full inspiration in 1 second. Also called FEV1
what is Vital capacity
Total volume of gas exhaled after a full inspiration
What is Forced vital capacity(FVC)
: used to indicate that expiration is forced. May be slightly less than vital capacity
How many seconds does it take to expire full vital capacity
3 secs
What are the 2 parameters we use for measurement per PFT?
FEV1 and FVC
What does the ratio of FEV1/FVC measure
How quickly you can move air and if there are any issues with the lungs
Whats the normal Fev1/Fec ratio
4/5= 80%
The FEV1/FEC ratio is reduced in obstructive disease and overall volume is reduced
T..takes longer for air to be blown out..cant move air fast
example
asthma, bronchitis…any obstruction
FEV1 is decreased FVC is unchanged or reduced but LESS so Ratio FEV1/FVC is decreased Asthma Chronic Bronchitis Emphysema
what happens to FEV1/FEC ratio in restrictive disease
In Restrictive disease, the FEV1/FEC ratio may actually be increased, but the total volume is down.
FEC is smaller,
they moving less air …weak muscles of the chest and broken ribs
smokers lungs,interstial fibrosis.sarcodiosis.
FVC is decreased Even if FEV1 is reduced Ratio FEV1/FVC is normal or may be increased Interstitial fibrosis Sarcoidosis Scoliosis Weakness
Obstructive curves have what kind of appearance
Scooped out appearance.
chronic bronchitis characteristics
Blue Bloater
Not Dyspneic
Cor pulmonale
Edematous
(Bloated)
Right side HF
Reduced
Drive to
Breath
Severe
Hypoxemia
Elevated
pCO2
polycythemia
Emphysema characteristics are
Pink Puffer
Increased
Drive to
Breath
Mild
Hypoxemia
Normal
pCO2
Normal
RBC mass
Breath so fast co2 is low
Pink
Dyspneic
No Cor
Pulmonale
Not
Edematous
Between inspiration and expiration, when does gas exchange occur in the lungs?
Expiration
Diffusion is most efficient with the following properties of the blood-gas interface.
Thin surface area and large surface area.
When does recruitment of capillary vessels happen
This happens during exercise, when cardiac output, and thus, pulmonary blood flow is increased.
When does pulm vascular resistance increase
with alveolar hypoxia, due to constriction of small pulmonary arteries
The total pressure in arterial blood is what?
713
what happens to airway resistance with increased lung volumes
Decreases
increase radius,decrease in resistance.
When lungs collapse, what happens to the resistance
Airway resistance increases
Whats the effects of bronchial smooth muscle contraction in the lungs per resistance
It increases airway resistance
In relation to Dynamic compression of airways , does the resistance increase or decrease in the airways during expiration?
resistance increases because the airway becomes narrower.
What determines flow during dynamic compression
Flow during dynamic compression is determined by the gradient between alveolar pressure and pleural pressure
Maximal expiratory flow is used to diagnose what condition
Asthma
when is the lung volume higher,during inspiration or exp
Exp
what is Hysteresis
The phenomenon by which the lung demonstrates different compliance curves during inspiration and expiration. Lung volume at any given pressure is higher during deflation than during inflation.
At volume above FRC is the way pressure positive or negative
positive, its negative at volumes below FRC
what does oxygen transfer into pulmonary capillary depend on?
O2 transfer into the pulmonary capillary is dependent on blood flow, and is therefore, mainly perfusion limited.
After steady-state where does the pressure gradient between capillary and alveolar rest in to cause a flow of oxygen
Partial Pressure of O2 in the capillary is 40 mm Hg, and that of alveolar air is 100 mm Hg
O2 flows down this large pressure gradient, and pO2 in the cell rapidly rises.
Is CO uptake diffusion-limited or Perfusion limited
Diffusion limited
The Ratio of Co2 produced and oxygen consumed is called?
Respiratory Quotient (R)
CAuses of hypoventilation are?
- Drugs such as Morphine and barbiturates
- Damage to the chest wall
- Weakness of respiratory muscles
- Decreased flow of air, due to very dense gas, as at great depth underwater
The fall in pO2 due to hypoventilation can be countered by
Exogenous Oxygen Administration
Can a shunt raise Co2 ?
NO
Ventilation perfusion ratiois abnormally hight at the top t/f
True
During exercise alveoli oxygenation is high at the Apex or BAse?
Apex
During Positive pressure ventilation where is alveolar oxygen highest
Apex
In west Zones of the Lungs, what causes increase in blood flow gradient from top to bottom
Gravitational hydrostatic pressure, this results in more distended alveoli at the Apex rather than the base.
Less blood flow at the top compared to the bottom
In West Zone 1, what pressure is the greatest between PA,Pa and Pv and What’s the state of blood flow
PA pressure is the greatest and there is little to no blood flow.
In West Zone 2, what pressure is the greatest between PA,Pa and Pv and What’s the state of blood flow
Pa(arterial) pressure is the greatest,the PA acts as a resistance(Flow limiting segment)
when this resistance is overcome, then flow becomes independent of downstream pressure
In West Zone 3, what pressure is the greatest between PA, Pa or Pv and What’s the state of blood flow.
Flow is higher here because ALveolar pressure is lowest here. Flow depends on the Difference btwn the upstream Pa and downstream Pv.
If a patient has a shunt what will the lab results look like
Po2 and Co2 is Identical to that of Mixed venous Gas
If a patient has an embolism and dead space occurs what will the lab look like
Here O2 rises and CO2 falls, approaching the composition of inspired gas, O2 = 150 and CO2 = 0
What is oxygen capacity
The maximum amount of oxygen that can be combined with Hemoglobin
1 gm of pure Hb can combine with 1.39 ml O2
Normal Blood Hgb concentration is
15 gm/100ml
Characteristics of Co2 dissociation curve
CO2 Dissociation Curve is more linear than the O2 dissociation curve.
The CO2 dissociation curve is also much steeper, so for a smaller pressure change, there is a larger change in CO2 concentration, compared to Oxygen
The central Chemo receptors are located where and what do they respond to?
Central Chemoreceptors are located near the ventral surface of the medulla, and are surrounded by brain extracellular fluid and respond to changes in its H+ concentration. CSF plays an important role. When blood pCO2 rises, CO2 diffuses into CSF, liberates H+ ions, which stimulate chemoreceptors. The resulting hyperventilation reduces pCO2 in blood and CSF
The peripheral chemoreceptors are located where and they respond to what?
in the carotid bodies at the bifurcation of the common carotid arteries, and in the aortic bodies above and below the aortic arch. They respond to decreases in arterial PO2 and pH, and increases in arterial pCO2.
For Co2 ventilatory response, which is faster between peripheral and central response centers
Peripheral
When do we notice hypoxemia
High altitude
during sleep
brain injury
