Physiology Respiratory Sukoawsi 1 Flashcards
What are the muscle used for rested inspiration? for forced?
Rested- Diaphragm and External Interncostals
Forced- Accessory muscles in teh neck, thorax, and abdominal cavities
What are the muscles used in rested expriration? Foreced?
rested- None, passive elastic recoil
Forced: Internal Intercostals, neck, and abdominal muscles
Definition of elastic
ability to spring back and resist deformation
Definition of Compliance
ability to yeild and be nonresistant (distensibility)
Definition of recoil
Ability to rebound or spring back
relation of recoil and compliance
The higher the compliance, the lower the recoil (mush ball)- Obstructive disease, emphysema,
The lower the compliance, the higher the recoil (golf ball), Restrictive disease
Examples of Obstructive lung diseases
Increased Resistance
Asthma
Bronchitis
Emphysema
Examples of Restrictive lung disease
Decreased compliance (higher recoil)
Diffuse Interstitial Fibrosis
Pulmonary Edema
Type A vs Type B COPD
Type A- symptoms of Emphysema (man culprit is cigarette smoking, alpha 1 antitrypsin deficiency)
Type B- symptoms of chronic bronchitis
What are clinical features of emphysema
HypoxemiaL milkd (PaO2 = ~80)
(A-a) PO2 = 10-15 (normal is
Hypercapnia: None
Acid-base problems: None as long as PaCO2 is normal
Tissue oxygenation: Normal
What is a “pink puffer”
Type A COPD
PaO2 - slighly reduced (~80)
PaCO2- normal
Acts like dead space
enough O2 in blood (pink)
needs to breathe more to maintain normal O2 and PaCO2 (puffer)
Chronic Bronchitis
Type B COPD
Narrowing of airwasy caused by hypersecretion of mucous and thickening of walls of respiratory tree
Chief culprit is smoking
Clinical Features of Type B COPD (chronic bronchitis)
Peristent, productive cough
Hypoxemia : Significatn to severe (PaO2= 40-70)
A-a PO2 ( 20-50)
Hypercapnia: Moderate (PaCo2=~50)
Acid-Base Disorder: mild to moderate acidosis
What is a blue-bloater
Decreased arteriolar PO2
Increased PCO2
May show signs of fluid retention with dependent edema
Acts like shunt
What potentiates Hypoxic Vasoconstriction
Decreased blood pH
What is the primary diorder in pulmonary blood flow
High V/Q ratio
theoretically, hypoxia shouldn’t develop,but often does
Diffusion impairment in areas with high flows
Pulmonary shunts develop
- Opnieng AV anastomoses
- blood though areas of hemorrhagic atelectasis
Clinical of Pulonary emoblism
PaCO2: Normal or mild hypocapnia
Acid-base disorder: None or mile alkalosis
What is Absorption Atelectasis
Occluded airway ,
Nitrogen is poorly soluble in plasma, and thus remains in high concentration in alveolar gas. If the proximal airways are obstructed, for example by mucus plugs, the gases in the alveoli gradually empty into the blood along the concentration gradient, and are not replenished: the alveoli collapse, a process known as atelectasis. This is limited by the sluggish diffusion of Nitrogen. If nitrogen is replaced by another gas, that is if it is actively “washed out” of the lung by either breathing high concentrations of oxygen, or combining oxygen with more soluble nitrous oxide in anesthesia, the process of absorption atelectasis is accelerated. It is important to realize that alveoli in dependent regions, with low V/Q ratios, are particularly vulnerable to collapse.
How do you treat Absorption Atelectasis
Problem can be minimezed by regularly hyperinflating lungs during anesthesia (a sigh) or by PEEP (positive and expiratory pressure)
What are static characteristics of respiration
Compliance and Recoil
What is equation of compliance
Change in volumepressure
What are two factors of recoil
- Recoil due to surface tension (major part of recoil force of lung)
- reduced by surfactant but not elimated (80%) - Recoil due to tissue elastic elements (Elastin, collagen, etc) 20%
What are the dynamic characterisitcs of respiration
- Resistance to airflow due to airway resistance (AWR) - 80%
- Resistance to airflow due to tissue frictional or viscour resistance (20%)
What detemrines airlow/ AWR
- flow rate
- flow pattern (diameter of airways and branching)
- Density
- Viscosity
What determines Flow rate?
- recoil pressure (determined by lung volume and compliance)
- AWR
What are factors that increase compliance (easier to inflate)
Emphysema
Asthma
Age
Asthma
Decreased Compliance (harder to inflate)
Fibrosis
Edema
High pulmonary venous pressure
Lack of surfactant
Increased recoil
Definition of Ventilation
Movement of flow of air form outside through air passages to terminal respiratory units (alveoli)
What determines the amt of ventilation (
- Distensibility of lungs (compliance)
- Factors that govern air movement
- Muscular effort required to enlarge thorax and lungs, thereby generating a pressure differnce to drive air flow
AWR impedes air flow
What par tof lung receives greatest ventilation? Why?
Bottom of lung receives the greates ventialtion when one spires from FRC
- diferent IP P vertically, with top alveoli experiecning a more negative pressure holding them open before inspritation . Top alveoli has less reserve to enlarge
- Weight of lung compresses lower alveoli. With inspriationa nd lowering dipahram, elastic componens of lung reduces this effect
- Sum of all factors places lower lugn ona more favorable segment of the compliance curve at FRC
What is surface tension
at he air-liquid interphase inside the lung; tends to collapse the lung to a smaller volume
What is LaPlace’s Law
Pressure (inside) = (2xST) / Radius
What is responsible fo tissue elastic recoil?
Geometric arrangement of elastin and collagen fibers
COnsider effects on compliance of lung fibrosis or elastin changes seen with aging
Are alveoli bigger at base or apex of lung? WHy
At apex (top) they are bigger. The alveoli are smaller at the base b/c of gravity
The Bottom of the lung has a higher negative pressure (more positive) than top of lung
Where d you meaures P-V bevavior in a pateint
in teh esophagus!
Place small balloon in esophagus and measure pressure
What is the normal compliance of the lung
1000/5 = 200 ml/cm H20
What needs to happen to intrapleural pressure in ordr for lungs to expand?
Intrapleural pressure needs to decerase so lungs can expand
Which alveoli are more compliant, larger or smaller alveoli?
Smaller alveoli at the bottom! Using LaPlace’s Law , where Presssure is lower with smaller radius (smaller alveoli)
What is responsible for elasticity/ compliance of lung?
- geometry of fibers
2. Surface tension
In a closed thorax, what is responsible for negative IP pressure at FRC
elastic recoil of chest wall outward
Lung recoil inweard
What happens to IP Pressure duing forced expiration? Forced inspriaton?
Forced expiration- IP more positive at FRC
Forced inspiration- IP more negative at FRC
What is the units of measurement used for ST
Dynes/cm
What do pressure-volue curves describe
lugn compliance at different lung volumes and show HYSTERESIS
What does difference in compliance depnd on
level in lung at any one lung volume at FRC (after normal expiration)
what happens to small airways athe base of lung at !0% Vital Capcity or less?
At RV (after forced expiration)
small airways at the base of lung CLOSE b/c of the POSITIV PRESSSURE (intraplural), trapping air in teh distal alveoli
This CLOSING VOLUME increases with age and disease
What is the PRIMARY factor that causes static recoil of lungs?
Surface Tension
What kind of cells produce surfactant
Type II alveolar Cells
What does Surfactant do to surface tension? What molecule?
Reduces ST and stabilizes lung alveoli
Surfactant contains DPP , detegent synthesized by FFAs and other
These cause HYSTERESIS seen in compliance curves
What does impedence of blood flow to a region do to surfactant synthesis
It prevents surfactant synthesis
What are the functions of Surfactant (3)
- Increases Compliance (makes it easier to inflate lungs)
- Surfacatant keeps lung dry/reduces tendency of alveolar edema (reduces forces that “pull” fluid out of capillary”
- Increases Alveolar stability (less likely that smaller alveoli empty into larger alveoli)
How does surfactant reduce tendency of alveolar edema
B/c without surfactant, alveoli with lining layer –> alveolus contracts due to high ST Pressure –> reduces pressure around capillaries of alvelar wall –> edema moves out
Interdependence also increases alveolar stability and eeps pressure low around large BV and airways as sthe lung epands. This ist eh site of early edema
Loss of surfacatnat results in (3)
- Stiff lungs (elevated surface tenson)
- Areas of atelectasis
3 Alveoli filled iwth fluid
How does surfactatn keep lungs dry? Whawt happens without surfactant?
Lack of surfactant increases ST of the alveolus, drawing the alveolar walls inward (recoil)
This causes greater negative interstitial space, overcoming colloid osmotic pressure (COP) of blood, resulting in more fluid filtering out of capillaries into interstiial space and into alveoli
What happens to surfactant in premature inants
Lack of surfactatn resuts in infant respiratory distress syndrome
Similar condition exists in adutls nad is called Adult Respiratory Distress Syndrom (ARDS)
What are factors that increase compliance (easier to inflate)
Emphysema
Age
Asthma
Decreased Compliance (harder to inflate)
Fibrosis
Edema
High pulmonary venous pressure
Lack of surfactant
Definition of Ventilation
Movement of flow of air form outside through air passages to terminal respiratory units (alveoli)
What determines the amt of ventilation (
- Distensibility of lungs (compliance)
- Factors that govern air movement
- Muscular effort required to enlarge thorax and lungs, thereby generating a pressure differnce to drive air flow
AWR impedes air flow
What par tof lung receives greatest ventilation at FRC? Why?
Bottom of lung receives the greates ventialtion when one spires from FRC
- diferent IP P vertically, with top alveoli experiecning a more negative pressure holding them open before inspritation . Top alveoli has less reserve to enlarge
- Weight of lung compresses lower alveoli. With inspriationa nd lowering dipahram, elastic componens of lung reduces this effect
- Sum of all factors places lower lugn ona more favorable segment of the compliance curve at FRC
Which lung gets more ventialtion at RV? Why?
Upper lungs receive greateest venitaltion intiially!
Small airways (Respiratory bronchioles) in teh bottom of lung close as one exhales and approacehs RV
Restuls in air trapping in lower lunga nd greater precetnatge of expired air coming from uper protions of lung at eh end of a forced expiration to RV
With age, lugns more compliant, closure of small aiways occurs at higher lung ovluems (even at FRC)
Chest wall and lungs- relaxation curve
Chest wall and lungs each attempt to recoil to their lowest free energy equilibrium position
What is chest walla and lungs at FRC
outwards at FRC for chest wall
Inward at FRC for lungs
FRC is determined when the two reocil forces balane each other
