Respiratory 1

Front 1

Normal Lung Function

Back 1

maintain normal PaO2, PaCO2 and pH w/out excessive cardiac or pulmonary work

Front 2

Adequate gas exchange

Back 2

1. Adequate ventilation
2. Adequate perfusion
3. Distribution of ventilation
4. Diffusion of O2 and CO2 across alveolar cap membrane

Front 3

Most impt cause of gas exchange abnormalities

Back 3

Nonuniform distribution of ventilation

Front 4

Conducting airways (Gen 0-16)

Bronchi

Bronchioles

Back 4

No gas exchange
Flow is turbulent

Bronchi - lare cartilaginous airways caliber depends on bronchial wall smooth muscle tone

Bronchioles- smaller airways whos caliber depend on lung volume

Front 5

Function of conducting airways

Back 5

1. warm and humidify inspired air
2. Distribute inspired air to alveoli for gas exchange
3. remove foreign material from inspired air reaching the alveoli

Front 6

Respiratory bronchioles (Gen 17-23)

Back 6

Gas exchange occurs (thinner walled)
Flow is laminar

Respiratory bronchioles receive nutrients from pulmonary circulation

Front 7

Alveoli

Back 7

site of gas exchange
Spherical shape
300-500 million alveoli
Total SA 75M2 (90 sq yrds/tennis court)--> impt to distribute entire Cardiac output over a surface one erythrocyte thick

Alveolar- cap membrane 1/2-1 u thick

Pulmonary cap sheets of blood surrounding alveolar airspace not tubular blood vesseles

Airflow in alveoli is by diffusion

Front 8

O2 and Co2 transport across alveolar-cap membrane by...

Back 8

Passive diffusion

No active transport

Front 9

Function of pulmonary circulation

Back 9

1. bring unoxygenated blood to alveoli
2. serve as a reservoir
3. serve as a filter
4. metabolize (detoxify) substances as they pass through lungs

High compliance, low resistance circuit

Front 10

Bronchial circulation

Back 10

perfuses conducting airways and arises from systemic circulation

Front 11

O2 transport in blood

Back 11

~5% of O2 carried in blood is dissolved

0.003mL of O2/ dL of blood/ torr of PO2

~95% of O2 carried in blood is bound to hemoglobin

1.34mL O2/ g of 100% saturated Hemoglobin
Saturated O2 to Partial pressure of O2 is non-linear

Front 12

Oxyhemoglobin dissociation curve to R

Back 12

Dec hemoglobin affinity for O2 but improve tissue delivery of O2

1. Acidosis
2. Inc P CO2
3. Inc Temp

Front 13

Oxyhemoglobin dissociation curve to L

Back 13

Inc hemoglobin affinity for O2 but dec tissue delivery of O2

1. Alkalosis
2. Dec P CO2
3. Dec Temp

Front 14

CO2 transport in blood

Back 14

10% is dissolved
30% bound to carbamino compounds in erythrocyte
60% in carbonic acid as HCO3- in plasma

Relationship is linear in physiological range

Front 15

Bohr effect

Back 15

CO2 and acidosis dec affinity of hemoglobin for O2

Front 16

Haldane effect

Back 16

O2 dec affinity of hemoglobin for CO2

Front 17

At rest, When is O2 diffusion complete?

Back 17

before RBC traverse half way thorugh pulmonary cap

PaO2 slightly > PaO2

Normal [PAO2- PaO2]< 10 torr
Alveolar partial pressure - arterial partial pressure

Front 18

Can O2 diffusion be inc by inc diffusion gradient in normal lung (Inc Fraction inspired O2)?

Person is hypoxic?

Back 18

NO,


but Inc fraction inspired O2 can inc O2 diffusion in abnormal lungs if person is hypoxic breathi

Front 19

What limits O2 diffusion?

Back 19

The inability to carry more O2 in blood

Nearly all oxygen is carried in blood on hemoglobin
Oxyhemoglobin dissociation curve is nonlinear and hemoglobin is 100% saturated with O2 at Pa:O2 100torr

Even if more O2 cannot be carried away by blood

Not, physical barriers like alveolar cap membrane

Front 20

Inc O2 diffusion by

Back 20

1. Inc O2 uptake
2. Inc hemoglobin
3. Inc Cardiac output

Front 21

CO2 is more diffusible than O2

Back 21

thus PA CO2= Pa CO2

Front 22

Ventilation/perfusion ratio (V/Q)

What is it in a normal lung?

Back 22

Determines PA O2 and PA CO2

V/Q=1
PA O2= ~100 torr
PA CO2= 40 torr

PAO2 proportional to V/Q
PA CO2 is inversely proportional to V/Q and to VA

Front 23

V/Q >1

Back 23

Partial Alveolar pressure of oxygen PA:O2 is inc (high PA:O2)
close to 1 close PA:O2 --> 100 torr
close to infinite PA:O2 --> 150 torr

Partial alveolar pressure of carbon dioxide PA:CO2 is dec (low PA:CO2)
Closer to 1: PA:CO2--> 40
Closer to infinite: PA:CO2--> 0

Front 24

V/Q <1

Back 24

Partial alveolar pressure oxygen (PAO2) is decreased (Low)
Closer V/Q 1 PA:O2-->100
Closer to 0 PA:O2--> lower PA:O2

Partial pressure of CO2 (PACO2) is increased (High)
Closer to 1 PA:CO2 --> 40
Closer to zero higher PA:CO2 will be

Front 25

VE = VD + VA

Back 25

VA= alveolar ventilation (takes part in gas exchange)

VD= wasted ventilation (does not take part)

Front 26

Calc PA O2 and PA CO2

Back 26

PACO2 = [VCO2/VA] [PB-47]
PB- barometric pressure

PACO2= 40 [V/Q]^-1

PAO2= PIO2 -[PACO2/0.8]

Front 27

Lung structure

Back 27

1. Airways (23 generations /divisions) from trachea to respiratory bronchioles

2. Alveoli

Front 28

Functional Lung unit

Back 28

Largest unit where PO2 and PCO2 are uniform

Occurs at level of respiratory bronchiole

~5000 alveoli

Front 29

Pulmonary artery

Pulmonary vein

Back 29

Artery- enters lung with airway and lymphatic

Vein- leaves lung separately

Front 30

PIO2 (partial inspired air)

Back 30

conster both FIO2 franction inspired oxygen and barometric pressure

Front 31

Hemoglobin

Back 31

O2 bound to hemoglobin 1.34 mL of O2 per gram of fully saturated hemoglobin

Relationship of sat hemoglobin to PO2 --> oxyhemoglobin dissociation curve its non linear

Front 32

P50

Back 32

Defines the position of the oxyhemoglobin dissociation curve

Where hemoglobin is 50% saturated

Normal P50 for hemoglobin A is 26 torr

Diff types of hemoglobin have diff shaped curves and diff p50 values

Front 33

Oxyhemoglobin dissociation curve determined by..

Back 33

1. temperature
2. pH
3. PCO2

Front 34

Calculate O2 content of Blood (C: O2)

Back 34

C:O2= 1.34[Hgb][S:O2]+0.003[P:O2]

Normal Sa:O2 is 100%
thus normal Ca:O2= 20.4mL

Normal Sv: O2 is 75%
thus normal Cv:O2=15.2mL

Front 35

Determinants of C:O2 in arterial blood

Back 35

1. Lung function (P:O2 and S: O2)
2. Hemoglobin (anemia)
3. Substances interfering with O2 binding to hemoglobin (CO)

Front 36

RBC through circulation

In the lungs

Back 36

Lungs:
-Cool Temp causes inc hemoglobin affinity for O2
-Inc O2 affinity on hemoglobin displaces CO2 --> CO2 is exhaled (Haldane effect)
- dec CO2 is alkaline furhter inc affinity for O2

Blood leaving lungs has inc O2 content and dec CO2 content

Front 37

RBC through circulation

In the tissues

Back 37

Tissue:
- High temp dec hemoglobin affinity for O2--> enhances tissue deliver of O2
- dec O2 inc hemoglobin affinity for CO2--> CO2 is removed
- Inc CO2 is acidic further dec hemoglobin affinity for O2 (Bohr Effect)

Systemic venous blood is low in O2 and high in CO2

Front 38

If Ve goes to L and Op goes to R

Back 38

no gas exchange bc they are not meeting together

Front 39

O2 concentration in alveolus is proportional to the amt coming in vs amount going out

Back 39

Amt in is ventiatlation times FI:O2

Minute ventilation (Ve) is measured as amt of exhaled air

Front 40

Minute ventilation (Ve)

Back 40

tidal volume (Vt) times respiratory rate

Amt going out is proportional to perfusion (Qp)

Front 41

Alveolar O2 concentration is an equilibrium determined by

Back 41

ratio Ventilation to perfusion (V/Q)

Front 42

Alveolar CO2 concentration is an equilibrium determined by

Back 42

ratio of amt coming in (proportional to Q) to amoutn going out (V)

Inversely proportional to V/Q

Front 43

PA:CO2

Back 43

CO2 produced at constnat rate by body's metabolic rate

CO2 enters alveolus via perfusion and is removed by ventilation

VA (alveolar ventilation is 70% of VE)

Shortcut
PA:CO2=40* V/Q^-1

Front 44

PA: O2

Back 44

O2 consumed at a constant rate (VO2) O2 enters alveolus by ventilationa dn O2 enter alveolus is = VA X FIO2

Shortcut:
PA:O2=PI:O2 - [PA:CO2/0.08]

Front 45

Arterial blood

Back 45

comes from lungs and reflects lung function

can measure PO2 and PCO2

Front 46

Venous blood

Back 46

comes from tissues and reflects tissue metabolism

Front 47

Cabonic acid

Back 47

CO2 and acid base status are related by carbonic acid in blood

Thus arterial blood gases assess acid base status as well as oxygenation

Front 48

Cyanosis

Back 48

-clinical sign of blue skin coloration
-seen in lips and fingenails
- associated with hypoxia
- when only 5gm/dL of unsaturated hemoglobin

Normal Sv:O2 is 75% for Hgb-14gm/dl only 3.5gm/DL unsat hemoglobin in venous blood --> no cyanosis

Lung disease whos anemic (dec Hgb) may not show cyanosis even if hypoxic

Pts with polycethemia (inc Hgb may show cyanosis even ir normoxic