Brs Physiology Respiratory Physiology

Front 1

Describe Tidal Volume

Back 1

It is the volume of inspired or expired with each normal breath

Front 2

Describe Inspiratory Reserve Volume

Back 2

-It is the volume that can be inspired over and above the tidal volume
-It is used during exercise

Front 3

Describe Expiratory Reserve Volume

Back 3

It is the volume that can be expired after the expiration of a tidal volume

Front 4

Describe Residual Volume

Back 4

-It is the volume that remains in the lungs after a maximal expiration
-It cannot be measured by spirometry

Front 5

Describe Anatomic Dead Space

Back 5

-The volume of the conducting airways
-Approximately 150ml

Front 6

Describe Physiologic Dead Space

Back 6

-A functional measurement
-It is defined as the volume of the lungs that does not participate in gas exchange
-It is approximately equal to the anatomic dead space in normal lungs
-It may be greater than the anatomic dead space in lung diseases in which there are ventilation/perfusion (V/Q) defects

Front 7

What is the equation to define physiologic dead space?

Back 7

V_D=V_T* (P_ACO2-P_ECO2)/(P_ACO2)

V_D=Physiologic Dead Space
V_T= Tidal Volume
P_ACO2=P_CO2 of alveolar gas = P_CO2 of arterial blood
P_ECO2=P_CO2 of expired air

Front 8

Describe Minute Ventilation

Back 8

Minute Ventilation = TV*RR

Front 9

Describe Alveolar Ventilation

Back 9

Alveolar Ventilation = (TV-Dead Space)*RR

Front 10

Describe Inspiratory Capacity

Back 10

The sum of Tidal Volume and IRV

Front 11

Describe Functional Residual Capacity

Back 11

-The sum of ERV and Residual Volume
-The volume in the lungs after a tidal volume is expired
-Includes the residual volume so it cannot be measured by spirometer

Front 12

Describe Vital Capacity/Forced Vital Capacity

Back 12

-The sum of Tidal Volume, IRV, and ERV
-The volume of air that can be forcibly expired after a maximal inspiration

Front 13

Describe Total Lung Capacity

Back 13

-The sum of all four lung volumes
-The volume in the lungs after a maximal inspiration
-Includes residual volume, so it cannot be measured by spirometry

Front 14

Describe Forced Expiratory Volume (FEV1)

Back 14

-FEV1 is the volume of air that can be expired in the first second of a forced maximal expiration
-Normally 80% of forced viral capacity

Front 15

Describe how FEV1 is affected by obstructive lung disease

Back 15

In obstructive lung disease, such as asthma, FEV1 is reduced more than FVC so that FEV1/FVC is decreased

Front 16

Describe how FEV1 is affected by restrictive lung disease

Back 16

In restrictive lung disease, such as fibrosis, both FEV1 and FVC are reduced and FEV1/FVC is either normal or is increased

Front 17

What are the muscles of inspiration?

Back 17

-Diaphragm
-External intercostals
-Accessory muscles

Front 18

Describe the Diaphragm

Back 18

-The most important muscle for inspiration
-When the diaphragm contracts, the abdominal contents are pushed downward and the ribs are lifted upward and outward, increasing the volume of the thoracic cavity

Front 19

Describe the external intercostals and accessory muscles

Back 19

-Not used for inspiration during normal quiet breathing
-Used during exercise and in respiratory distress

Front 20

What are the muscles of expiration?

Back 20

-Abdominal muscles
-Internal intercostal muscles

Front 21

Describe the muscles of expiration

Back 21

-Expiration is normally passive
-Because the lung-chest wall system is elastic, it returns to its resting position after inspiration
-Expiratory muscles are used during exercise or when airway resistance is increased because of disease (e.g., asthma)

Front 22

Describe the role of abdominal muscles in expiration

Back 22

Compress the abdominal cavity, push the diaphragm up, and push air out of the lungs

Front 23

Describe the role of internal intercostal muscles in expiration

Back 23

They pull the ribs downward and inward

Front 24

Describe compliance

Back 24

-Describe the distensibility of the lungs and chest
-Is inversely related to elastance, which depends on the amount of elastic tissue
-Inversely related to stiffness
-The slow of the PV curve
-The change in volume for a given change in pressure. Pressure refers to the transmural or transpulmonary pressure (the pressure difference across pulmonary structures)

Front 25

What equation describes compliance?

Back 25

C=V/P

C=Compliance
V=Volume
P=Pressure

Front 26

Describe the compliance of the lungs

Back 26

-Transmural pressure is alveolar pressure minus intrapleural pressure
-When the pressure outside of the lungs (ie intrapleural pressure) is negative, the lungs expand and lung volume increases
-When the pressure outside of the lungs is positive, the lungs collapse and lung volume decreases
-Inflation of the lungs (inspiration) follows a different curve than deflation of the lungs (expiration) (called hysteresis)
-In the middle range of pressures, compliance is greatest and the lungs are most distensible
-At high expanding pressures, complaince is lowest and the lungs are lead distensible ad the curve flattens

Front 27

Describe the compliance of the lung-chest wall system

Back 27

Less than that of the lungs alone or the chest wall alone

Front 28

Describe the complaince of the lung-chest wall system at rest

Back 28

-Lung volume is at FRC and the pressure in the airway and lungs is equal to atmispheric pressure
-Under these equilibrium conditions, there is a collapsing force on the lungs and an expanding force on the chest wallAt FRC, these two forces are equal and opposite and therefore the combined lung-chest wall system neither wants to collapse nor expand

Front 29

Describe the intrapleural pressure at rest

Back 29

Negative due to the lungs collapsing in and the chest expanding out

Front 30

Describe a pneumothorax

Back 30

-Air is introduced into the intrapleural space
-The intrapleural pressure becomes equal to atmospheric pressure
-The lungs will collapse (their natural tendency) and the chest wall will spring outward (its natural tendency)

Front 31

Describe the changes in lung compliance due to emphysema

Back 31

-Lung compliance is increased then the tendency of the lungs to collapse is decreased
-At the original FRC, the tendency of the lungs to collapse is less than the tendency of the chest wall to expand
-The lung-chest wall system will seek a new higher FRC so that the two opposing forces can be balances
-The patient's chest becomes barrel-shaped, reflecting this higher volume

Front 32

Describe the changes in lung compliance due to fibrosis

Back 32

-Lung complaince is decreased and the tendency of the lungs to collapse is increased
-At the original FRC the tendency of the lungs to collapse is greater than the tendency of the chest wall to expand
-The lung-chest wall system will seek a new, lower FRC so that the two opposing forces can be balanced

Front 33

Describe the surface tension of the alveoli

Back 33

-Results from the attractive forces between liquid molecules lining the alveoli
-Creates a collapsing pressure that is directly proportional to surface tension and inversely proportional to alveolar radius

Front 34

Describe the surface tension of large alveoli vs small alveoli

Back 34

Large alveoli (large radius) have a low collapsing pressure and are easy to keep open

Small alveoli have high collapsing pressures and are more difficult to keep open

In the absence of surfactant, the small alveoli have a tendency to collapse

Front 35

What is atelectasis?

Back 35

-Lack of gas exchange within alveoli, due to alveolar collapse or fluid consolidation
-In the absence of surfactant, the small alveoli have a tendency to collapse

Front 36

Describe surfactant

Back 36

-Lines the alveoli
-Reduces surface tension
-Syntehsized by type II alveolar cells and consists primarily of phospholipid dipalmitoyl phosphatidylcholine (DPPC)

Front 37

Describe how surfactant reduces surfact tension

Back 37

-Disrupts the intermolecular forces between liquid molecules
-This reduction in surface tension prevents small alveoli from collapsing and increases compliance

Front 38

Describe surfactant synthesis in the fetus

Back 38

-Variable
-Surfactant may be present as early as gestational week 24 and is almost always present by gestational week 35
-Lecithin:sphingomyelin ratio greater than 2:1 in amniotic fluid reflects mature levels of surfactant

Front 39

Describe neonatal respiratory distress syndrome

Back 39

-Can occur in premature infants because of lack of surfactant
-Infant exhibits atelectasis (lungs collapse), difficulty reinflating the lungs (as a result of decreased compliance), and hypoxemia (as a result of decreased V/Q)