C/ · PDF file3 Some Typical Normal Values for Some Key Pulmonary Parameters FRC 2.6 L RV 1.5...

17
1 Trachea (Generation #1) Primary Bronchi (Generation #2) Conducting Airways Generations 1-16 2 o Bronchi (Generation #3) Respiratory Zone Generations ~17-23 Alveoli Respiratory Bronchioles O 2 CO 2 venous arterial P B =0 P A <0 Atmospheric Air High O 2 (150 mmHg) CO 2 ~ 0 Inspiration O 2 CO 2 venous arterial P B =0 P A >0 Alveolar Air O 2 ~100 mmHg CO 2 ~ 40 mmHg Expiration Fick’s law J = DA (ΔC/ ΔX) Lung Chest Wall Stuck Together Lung Air leak Pneumothorax Lung collapses & Chest expands Hemoglobin-O 2 Binding Curve 0 20 40 60 80 100 0 20 40 60 80 100 0 5 10 15 20 Venous Arterial CO 2 P aO2 (mm Hg) % Hb Saturation HbO 2 content (ml O 2 /dl)

Transcript of C/ · PDF file3 Some Typical Normal Values for Some Key Pulmonary Parameters FRC 2.6 L RV 1.5...

Page 1: C/ · PDF file3 Some Typical Normal Values for Some Key Pulmonary Parameters FRC 2.6 L RV 1.5 L TLC 6.0 L VT 500 ml FVC 4.5 L P FEV1.0 / FVC >75% Frequency 10-12/min

1

Trachea(Generation #1)

Primary Bronchi (Generation #2)

Conducting Airways Generations 1-16

2o Bronchi (Generation #3)

Respiratory ZoneGenerations ~17-23

Alveoli

Respiratory Bronchioles

O2

CO2

venous arterial

PB=0

PA<0

Atmospheric AirHigh O2 (150 mmHg)

CO2 ~ 0

Inspiration

O2

CO2

venous arterial

PB=0

PA>0

Alveolar AirO2 ~100 mmHgCO2 ~ 40 mmHg

Expiration

Fick’s lawJ = DA (ΔC/ ΔX)

LungChest Wall

StuckTogether

Lung

Air leakPneumothoraxLung collapses& Chest expands

Hemoglobin-O2 Binding Curve

0 20 40 60 80 1000

20

40

60

80

100

0

5

10

15

20

Venous

Arterial

↑CO2

PaO2 (mm Hg)

% H

b Sa

tura

tion

HbO

2 content (ml O

2 /dl)

Page 2: C/ · PDF file3 Some Typical Normal Values for Some Key Pulmonary Parameters FRC 2.6 L RV 1.5 L TLC 6.0 L VT 500 ml FVC 4.5 L P FEV1.0 / FVC >75% Frequency 10-12/min

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PO2=100 mm Hg14 ml O2/dL

PO2=100 mm Hg0.3 ml O2/dL

O2

O2

PO2=100 mm Hg14 ml O2/dL

PO2=100 mm Hg0.3 ml O2/dL dissolved20 ml O2/dL HB-O2

O2

O2

VT

Tota

l Lun

g C

apac

it y

ExpiratoryReserve

InspiratoryReserve

FRC

InspiratoryCapacity

ResidualVolume

VitalCapacity

1 s

FEV1.0

VT

Tota

l Lun

g C

apac

it y

ExpiratoryReserve

InspiratoryReserve

FRC

InspiratoryCapacity

ResidualVolume

VitalCapacity

500 ml

2.6 L

1.5 L

4.5 L

~6 L

Forced Vital CapacityTLC

FEV1.0 FVC

1 secFEV1.0 = 4 LFVC = 5 L

% = 80%

RV

TLC RV

Exp

irato

ry F

low

Rat

eLung Volume

Flow-Volume Curves

V. A Few Terms (for Your Convenience) Eupnia - Normal breathing. Apnea - cessation of respiration (at FRC). Apneusis - cessation of respiration (in the inspiratory phase). Apneustic breathing – Apneusis interrupted by by periodic exhalation. Hyperpnea – increased breathing (usual ↑VT). Tachypnea – increased frequency of respiration. Hyperventilation – increased alveolar ventilation (PACO2 <37 mm Hg). Hypoventilation – decreased alveolar ventilation (PACO2 >43 mm Hg). Atelectasis – closed off alveoli, typically at end exhalation. Cheyne-Stokes Respiration – Cycles of gradually increasing and decreasing VT. Dyspnea- Feeling of difficulty in breathing. Orthopnea- Discomfort in breathing unless standing or sitting upright. PIP - Intrapleural pressure (pressure in space between visceral and parietal plurae) PTP - Transpulmonary pressure (distending pressure of airway) PACO2 - Alveolar PCO2 (partial pressure of CO2). PaCO2 - arterial PCO2. PvCO2 - venous PCO2 PAO2 - Alveolar PO2 PaO2 - arterial PO2 PvO2 - venous PO2 PECO2 - PCO2 of exhaled air FECO2 – fraction of exhaled air which is CO2 (i.e. A= Alveolar, a= arterial, v= venous, E = exhaled, I = inspired) VE – Expired volume (liters) V•E – ventilation (liters/min) (V

• = dV/dt)

V•A – Alveolar ventilation (liters/min)

Q•

– Blood Flow (liters/min)

Page 3: C/ · PDF file3 Some Typical Normal Values for Some Key Pulmonary Parameters FRC 2.6 L RV 1.5 L TLC 6.0 L VT 500 ml FVC 4.5 L P FEV1.0 / FVC >75% Frequency 10-12/min

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Some Typical Normal Values for Some Key Pulmonary Parameters FRC 2.6 L RV 1.5 L TLC 6.0 L VT 500 ml FVC 4.5 L

FEV1.0 / FVC >75% Frequency 10-12/min V•A (norm) 5 ± 0.5 L/min

V•E (norm) 7 ± 0.7 L/min

V•E (max) 120-150 L/min

Max. insp flow 7-10 L/sec

Max. exp flow 6-9 L/sec Compliance 60-100 mL/cm H20 PAO2 100 mm Hg PaO2 (21% O2) 90-95 mm Hg PaO2 (100% O2) >500 mm Hg PaCO2 40 ± 3 mm Hg Arterial pH 7.37-7.43 PvO2 40 mm Hg PvCO2 46 mm Hg [Hb] 14-15 g/dL

ChestWall

RecoilForce

Lung Wall

RecoilForce

Normal

Balance of Forces Determines FRCHooke’s Law: F = -kx

Fibrosis↑ lung recoil

Ppl= -8

Intrapleuralspace

Ppl = -2

Emphysema↓ lung recoil

Incr

easi

ngvo

lum

eD

ecre

asin

gvo

lum

e

Ppl = 0

Pneumo-thorax

NormalFRC

Ppl = -5

LungChest Wall

StuckTogether

Lung

As we remove airfrom pleural spacethe lung expands& the chest wallgets pulled in.

ChestWall

RecoilForce

Lung Wall

RecoilForce

NormalFRC

Ppl = -5

Normal

Balance of Forces Determines FRCHooke’s Law: F = -kx

Intrapleuralspace In

crea

sing

volu

me

Dec

reas

ing

volu

me

Ppl = 0

Ppl = -2

Emphysema↓ lung recoil

Fibrosis↑ lung recoil

Pneumo-thorax

Ppl= -8

Page 4: C/ · PDF file3 Some Typical Normal Values for Some Key Pulmonary Parameters FRC 2.6 L RV 1.5 L TLC 6.0 L VT 500 ml FVC 4.5 L P FEV1.0 / FVC >75% Frequency 10-12/min

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Sur

face

Are

a (r

elat

ive)

Surface Tension (dynes/cm)30 60

WaterDetergent

LungSurfactant Plasma

80

↑Surface Area ∝ ↑Surface Tension

Surfactant40% Dipalmitoyl Lecithin25% Unsaturated Lecithins

8% Cholesterol27% Apoproteins, other

phospholipids, glycerides,fatty acids

Hystere

sis

Sur

face

Are

a (r

elat

ive)

Surface Tension (dynes/cm)30 60

WaterDetergent

LungSurfactant

80

↑Surface Area ∝ ↑Surface Tension

1. Reduces Work of Breathing2. Increases Alveolar Stability

(different sizes coexist)3. Keeps Alveoli Dry

-18-16-14-12-10-8-6-4-202

Normal

VTFRCN

PIP (cm H2O)

Lung

Vol

ume

Expiration

Inspiration

Hysteresis Occurs During Dynamic Air FlowDue to Surfactant reorientation & Airway Resistance

Static Lung Compliance Curve

Static Compliance Curves

-18-16-14-12-10-8-6-4-202

Fibrosis(low compliance)

Normal

Emphysema(high compliance)

VT

FRCN VTFRCF

VT

FRCE

Intrapleural Pressure, PIP (cm H2O)

Lung

Vol

ume

ChestWall

RecoilForce

Lung Wall

RecoilForce

NormalFRC

PIP = -5

Normal

Balance of Forces Determines FRCHooke’s Law: F = -kx

Intrapleuralspace In

crea

sing

volu

me

Dec

reas

ing

volu

me

PIP = 0

PIP = -2

Emphysema↓ lung recoil

Fibrosis↑ lung recoil

Pneumo-thorax

PIP= -8

Page 5: C/ · PDF file3 Some Typical Normal Values for Some Key Pulmonary Parameters FRC 2.6 L RV 1.5 L TLC 6.0 L VT 500 ml FVC 4.5 L P FEV1.0 / FVC >75% Frequency 10-12/min

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Lung has weight

-8

PIP = -2

-5

Apex

Base

Chest Wall

Regional- Apex to Base Differences

-14-12-10-8-6-4-202

Apex

Base

Norm Lung Volume

Alveolar VolumeAlve Ventilation

Apex Base

++ ++

Inspiration

Inspiration

PIP (cm H2O)

Lung

Vol

ume

Regional- Apex to Base Differences

-14-12-10-8-6-4-202

ApexΔV

Base

Low Lung Volume(shifts to lower V)

Alveolar VolumeAlve Ventilation

Apex Base++++

PIP (cm H2O)

Lung

Vol

ume

Apex to Base Differences

-14-12-10-8-6-4-202

ApexΔV

Base

Low Lung V

Normal Lung V

PIP (cm H2O)

Lung

Vol

ume

The dashed trace is the PIPrequired to overcome recoil forces(ot PTP taken from compliance curve).More PIP (solid curve) is required toovercome airway resistance to flow.N.B. ΔP = PA-PB ∝ Resist•Flow.

Air Flow (L/s)

+1

-1

0

+0.6

-0.6

0

PA(cm H2O)

1 2 3 4time (sec)

-5

-8

cmH

2O

VT (L)0.4

0

0.2

Respiratory Cycle

Inspiration Expiration

PTP

PIP

PTP

PIPPB=0

-5

-7

-8

-6

-5

Rest FRC

Inspiration

End Inspiration

+

0

0

-AirFlow

PA= 0

PIP

End Expi-ration-FRC

Expiration

time

Respiratory CycleSingle VT Breath

Static Compliance Curves

-18-16-14-12-10-8-6-4-202

Normal

VT

FRCN

Pleural Pressure, Ppl (cm H2O)

Lung

Vol

ume

Expiration

Inspiration

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PA (cm H2O)+1

-1

0

+0.5

-0.5

0

Air Flow (L/s)

1 2 3 4time (sec)

-5

-8

Ppl (cm H2O)

Case of ZERO Resistance

VT (L)0.4

0

0.2

Respiratory Cycle

Inspiration Expiration

-5

-8

-8

-6

-5

Rest FRC

Inspiration

End Inspiration

+

0

0

-Air

Flow

PA= 0

Ppl

End Expi-ration-FRC

Expiration

time

Respiratory CycleSingle VT Breath

PB=0

PA (cm H2O)+1

-1

0

+0.5

-0.5

0

Air Flow (L/s)

1 2 3 4time (sec)

-5

-8

Ppl (cm H2O)

The linear Dashed trace is the Pplrequired to overcome recoil forces.More Ppl (solid curve) is required toovercome airway resistance to flow.N.B. ΔP = PA-PB ∝ Resist•Flow.

VT (L)0.4

0

0.2

Respiratory Cycle

Inspiration Expiration

-5

-8

-8

-6

-5

Rest FRC

Inspiration

End Inspiration

+

0

0

-Air

Flow

PA= 0

Ppl

End Expi-ration-FRC

Expiration

time

Respiratory CycleSingle VT Breath

PB=0

PA (cm H2O)+1

-1

0

+0.5

-0.5

0

Air Flow (L/s)

1 2 3 4time (sec)

-5

-8

Ppl (cm H2O)

VT (L)0.4

0

0.2

Respiratory Cycle

Inspiration Expiration

-5

-8

-8

-6

-5

Rest FRC

Inspiration

End Inspiration

+

0

0

-Air

Flow

PA= 0

Ppl

End Expi-ration-FRC

Expiration

time

Respiratory CycleSingle VT Breath

PB=0

Case of HIGH Resistance

Airway Generation5 1 0 15

Tota

l Cro

ss S

ectio

nal A

rea

ConductingZone

RespZone

v = Flow/A

NR= ρDv/ηρ=densityD= diameterv= velocityη= viscosity

Airway Generation

Res

ista

nce

SubsegmentalBronchi

5 1 0 15

Resistance

8ηlR= ———

πr4

k•numberR= —————

A2

N.B. this is total x-sectional area (AT

2 =n2An2)

Lung Volume

Airw

ay R

esis

tanc

e

Normal↓RecoilEmphysema

Fibrosis

Mild Expiratory Effort (P+13)

0

Normal at FRC-5

0

Dynamic Compression of Airways

PTP=+5PPl - PA= -5

Page 7: C/ · PDF file3 Some Typical Normal Values for Some Key Pulmonary Parameters FRC 2.6 L RV 1.5 L TLC 6.0 L VT 500 ml FVC 4.5 L P FEV1.0 / FVC >75% Frequency 10-12/min

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+28

30 25 20 15 10 5 0

EPP

Emphysema

in unsupported airways

Dynamic Compression of Airways

EPPEqual Pressure Point(in supported airways)

Low VL&Basal Alv

also like this

+13

Mild Expiratory Effort (P+13)

+8

8 4 0

Normal at FRC-5

0

+13

+13

PTP=+5PPl - PA= -5

+8

13 10 8 6 4 2 0

EPP

Emphysema+11

PPl-PA=-2

-2

0+11

Strong Expiratory Effort (P+30)

+25

30 25 20 15 10 5 0

EPP

Normal

+25

13 10 8 6 4 2 0

EPP

Emphysema+11

PPl-PA=-2

-2

0

Dynamic Compression of Airways

EPPEqual Pressure Point(in supported airways)

+13

Mild Expiratory Effort (P+13)

+8

8 4 0

Normal at FRC-5

0

+13

+13

PTP=+5PPl - PA= -5

Low VL&Basal Alv

also like this

Strong Expiratory Effort (P+30)

+25

30 25 20 15 10 5 0

EPP

Normal

+25

+28 Emphysema

30 29 28 27 25 20 0

Pursed-lipsHi Resist

EPPMoves toward the mouth

& supported airways

Normal

↑ResistanceObstructive

↑ RecoilRestrictive

time (sec)

Vol

ume

FRC

InspirationForced Vital Capacity

TLC

FEV1.0 FVC

1 sec

FEV1.0 = 4 LFVC = 5 L

% = 80%

RV

NormalTLC

FEV1.0

FVC

1 sec

FEV1.0 = 1.2 LFVC = 3.0 L

% = 40%

RV

Obstructive↑airway resist

Restrictive↑lung recoil

TLCFEV1.0 FVC

1 sec

FEV1.0 = 2.7 LFVC = 3.0 L

% = 90%

RV

Effort Independent limbin forced expiration.

TLC RV

Exp

irato

ry F

low

Lung Volume

Flow-Volume Curves

Due to Dynamic Airway Compression and airway collapse.

Inverted Inspiration

RV

Exp

irato

ry F

low Forced expiration

Inspiration

Insp

irato

ry F

low

TLC Lung Volume

Page 8: C/ · PDF file3 Some Typical Normal Values for Some Key Pulmonary Parameters FRC 2.6 L RV 1.5 L TLC 6.0 L VT 500 ml FVC 4.5 L P FEV1.0 / FVC >75% Frequency 10-12/min

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Normal

Obstructive

Restrictive

9 8 7 6 5 4 3 2 1 Lung Volume (L)

Flow

Rat

e (L

/sec

)

9TLC RV

Lung Volume (L)

6 5 4 3 2 1

3. Alveolar Plateau

1. 2. Dead Space Washout

4.

N2

Con

cent

ratio

n (%

)

20

40

Critical Closing Volume Test

ClosingVolume

Apex to Base Differences

-14-12-10-8-6-4-202

ApexΔV

Base

Pleural Pressure, Ppl (cm H2O)

Lung

Vol

ume

Low Lung V

Normal Lung V

TLC RV

Lung Volume (L)

6 5 4 3 2 1

3. Alveolar Plateau

1. 2. Dead Space Washout

4.N

2C

once

ntra

tion

(%)

20

40

Critical Closing Volume Test

ClosingVolume

IncreasedClosingVolume

Hemoglobin-O2 Binding Curve

0 20 40 60 80 1000

20

40

60

80

100

0

5

10

15

20

26

50

75

9097.5

PaO2 (mm Hg)

% S

atur

atio

n of

Hem

oglo

bin

Hb-O

2 content(m

l O2 /100 m

l blood)

Hemoglobin-O2 Binding Curve

0 20 40 60 80 1000

20

40

60

80

100

0

5

10

15

20

26

50

75

9097.5

PaO2 (mm Hg)

% S

atur

atio

n of

Hem

oglo

bin

Hb-O

2 content(m

l O2 /100 m

l blood)

0 20 40 60 80 1000

1

2

3

Dissolved O2

HbO2

PaO2 (mm Hg)

Hb-O

2 content(m

l O2 /100 m

l blood)

Page 9: C/ · PDF file3 Some Typical Normal Values for Some Key Pulmonary Parameters FRC 2.6 L RV 1.5 L TLC 6.0 L VT 500 ml FVC 4.5 L P FEV1.0 / FVC >75% Frequency 10-12/min

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PO2=100 mm Hg14 ml O2/dL

PO2=100 mm Hg0.3 ml O2/dL

O2

O2

PO2=100 mm Hg14 ml O2/dL

PO2=100 mm Hg0.3 ml O2/dL dissolved20 ml O2/dL HB-O2

O2

O2

Bohr Shift Hb-02 Curve

0 20 40 60 80 1000

20

40

60

80

100

Normal Hb

Bohr Shift↑[H+], ↑CO2, ↑Temp or DPG

↓[H+],↓CO2

↓Temp

PaO2 (mm Hg)

% S

atur

atio

n of

Hem

oglo

bin

0 20 40 60 80 1000

5

10

15

20Myoglobin

Normal Hb

Anemia

Carbon Monoxide

PaO2 (mm Hg)

Hb-

O2

cont

ent

(ml O

2 /1

00 m

l blo

od)

Capillary Wall

CO2 + H2O —→ H2CO3 → H+ + HCO3-

O2CO2

CO2Cl-

H+ + HbO2 → HHb + O2

CarbaminoHHb-CO2

O2

TissueCO2 Loading & O2 Unloading

c.a.

Alveolar Wall

O2CO2

CO2

Cl-

H+ + HbO2 ← HHb + O2

CarbaminoHHb-CO2

O2

LungsCO2 Unloading & O2 Loading

c.a.

HCO3-

CO2 + H2O ←— H2CO3 ← H+ + HCO3-

O2 curve

Who

le blo

od to

tal C

O 2Co

ntent

(ml C

O 2/dl)

Page 10: C/ · PDF file3 Some Typical Normal Values for Some Key Pulmonary Parameters FRC 2.6 L RV 1.5 L TLC 6.0 L VT 500 ml FVC 4.5 L P FEV1.0 / FVC >75% Frequency 10-12/min

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↑O2 helps CO2 unloading

Arterial (↑O2)

37 40 43 46 49 52

46

48

50

52

54

Rest Venous

PCO2(mm Hg)

CO

2C

onte

nt(m

l CO

2/1

00 m

l blo

od)

HALDANE SHIFT

↑O2 helps CO2 unloading

Arterial (↑O2)

Exercise Venous

37 40 43 46 49 52

46

48

50

52

54

Rest Venous

PCO2(mm Hg)

CO

2C

onte

nt(m

l CO

2/1

00 m

l blo

od)

HALDANE SHIFT

XIV. RESPIRATORY GAS CASCADEPO2 PCO2mm Hg mm Hg

⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯Air (dry) 760 × 0.21 160 0Trachea (humidified; 760-47) 713 × 0.21 150 0Alveolus (some O2 absorbed by blood) 100 40Arterial (R-L Shunt) 90 40+Mixed venous (O2 absorbed by tissues) 40 46

CO is Diffusion Limited (soaked up by Hb immediately)Uptake depends on Diffusing Capacity

CO+Hb=Hb-CO [CO]=“0”

NO2 is Perfusion Limited (Blood is quickly “saturated”)Uptake depends on how much blood goes by

NO2 doesn’t bind [NO2]i= [NO2]o

Measuring Diffusion capacity, DL ( or Transfer capacity) with COJCO = DCOA ΔP/ Δx ΔP = PACO – PaCO and PaCO=0 and DCO, A & Δx are lumped into DL

DL = JCO /PACO (where JCO is the rate of CO uptake measured)

Distance along Capillary (%)

33% 67% 100%

Cap

illary

PX

(% a

lveo

lar)

20

40

60

80

100

Diffusion in Pulmonary Capillaries

O2

CO

N2O

Diffusion Limited

Perfusion Limited

time in Capillary (sec)

0.25 0.5 0.75

PO

2m

m H

g

20

40

60

80

100

NormalTransit TimeExercise

ShortensTransit

time

Thickened Alveolar

Membrane

O2 Diffusion in Pulmonary Capillaries(transit time)

Page 11: C/ · PDF file3 Some Typical Normal Values for Some Key Pulmonary Parameters FRC 2.6 L RV 1.5 L TLC 6.0 L VT 500 ml FVC 4.5 L P FEV1.0 / FVC >75% Frequency 10-12/min

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Expired Lung Volume (L)0 0.2 0. 4 0.6 0.8

Alveolar Plateau

Inspired O2 dilutedby alveolar N2

N2

Con

cent

ratio

n (%

)

20

40

A

B

Fowler’s Test Area A = Area B

Vd

The Bohr Equation VD1 (PACO2 – PECO2) ⎯⎯⎯ = ⎯⎯⎯⎯⎯⎯⎯⎯ VT PACO2

PCO2 values are measured by a CO2 electrode. Sometimes PaCO2 is used. VD2 (PaCO2 – PECO2) ⎯⎯⎯ = ⎯⎯⎯⎯⎯⎯⎯⎯

VT PaCO2

D. Sample Calculation VT = 600 ml PACO2 = 38 mmHg PECO2 = 28 mmHg PaCO2 = 40 mmHg VD1 = 600(38 – 28)/38 = 158 ml VD2 = 600(40 – 28)/40 = 180 ml E. Alveolar Ventilation

V•E = V

•D + V

•A = VT × frequency

V•A = V

•E – V

•D

1. For VT = 500 ml, f = 10/min, VD = 150 ml, what is V•A?

V•A = 5000 - 1500

= 3500 ml/min 2. If V

•E is doubled by increasing VT what is V

•A?

= 10,000 - 1500 = 8500 ml/min 3. If the same V

•E is obtained by doubling frequency, what is V

•A?

= 10,000 - 3000 = 7000 ml/min Thus increasing VT rather than frequency is more effective for ↑ V

•E.

F. Alveolar Ventilation and CO2 production

V•CO2 = Expired CO2 - Inspired CO2

= V•A × FACO2

V•A × PACO2

= ⎯⎯⎯⎯⎯⎯ PA

V

•CO2 × k

V•A = ⎯⎯⎯⎯⎯⎯⎯

PACO2 Where k= 863 mmHg or 0.863 (mmHg•L/ml)

So, for a given rate of CO2 production, steady state PACO2 is inversely related to V

•A.

Thus, if V•A is decreased by 1/2, PACO2 is doubled.

XIX. RESPIRATORY EXCHANGE RATIO RQ = V•CO2/V

•O2

The relative amounts of O2 consumed and CO2 produced depends upon the fuel. Carbohydrate RQ = 1 Fat RQ = 0.7 Protein RQ = 0.8 A typical "normal" RQ is 0.8 The partial pressures of O2 and CO2 are also affected.

V•CO2 PACO2 40

RQ = ⎯⎯⎯ = ⎯⎯⎯⎯⎯ = ⎯⎯⎯ V

• O2 PIO2 - PEO2 50

Study Questions/ Exercises

Q: Why does this ratio necessarily reflect the RQ? Alveolar Gas Equation – Allows you to estimate PAO2 – PaO2 gradient. PAO2 = FIO2 (PATM – PH2O) – PaCO2/RQ + K PAO2 = PIO2 – PaCO2/RQ e.g. = 150 – 40/0.8 = 100 mmHg K = PACO2 •FIO2 • ({1-RQ}/RQ) a small correction (2 mmHg) usually ignored

Page 12: C/ · PDF file3 Some Typical Normal Values for Some Key Pulmonary Parameters FRC 2.6 L RV 1.5 L TLC 6.0 L VT 500 ml FVC 4.5 L P FEV1.0 / FVC >75% Frequency 10-12/min

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Zone 1PA>Pa>PvLow Flow

PAPa Pv

PAPa Pv

Zone 2Pa>PA>PvWaterfall

Zone 3Pa>Pv>PAHi Flow

PAPa Pv

PAPa Pv Zone 4Same, but

Hi extra-Alv-R

Flow

of B

lood

or A

ir

Bottom TopDistance up Lung

Ventilation

Perfusion

1

2

3

VA/Q. .

VA /Q

R

atio

.

.PO2 = 40PCO2 = 45

Normal VA/QLow VA/Q High VA/QCO2 = 45

PO2 = 150PCO2 = 0

PO2 = 100PCO2 = 40

PO2 = 150PCO2 = 0

. . .

Ventilation Perfusion Ratios

No flow

. . .

PO2 = 40PCO2 = 45

Low VA/Q.

Normal VA/Q.

PO2 = 100PCO2 = 40

High VA/Q.

PO2 = 150PCO2 = 0

PO2 (mm Hg)

PC

O2

(mm

Hg)

50 100 150

50

Base

Apex

Flow

of B

lood

orA

ir

Bottom TopDistance up Lung

Ventilation

Perfusion

1

2

3

VA /Q

R

atio

.

.

VA/Q. .

Region VA V•A Q• V•A/Q• PCO2 PO2 ⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯ Apex + + + Base + ++ + ⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯

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13

Mechanisms of HypoxemiaA. HypoventilationB. Diffusion AbnormalitiesC.Right to Left ShuntD.Ventilation/Perfusion MismatchE. Low inspired PO2

Mechanisms of Hypoxemia

PaO2 PaCO2 PO2 (A-a) PaO2 with 100% O2⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯Hypoventilation low High Norm >550

Diffusion low norm-low high >550

R-L Shunt low norm-low high <550.

VA/Q Imbalance low norm-lo-hi high >550

Other Hypoxemias (without low PaO2)a. Anemiab. Carbon Monoxidec. Hypoperfusion (CV problem)

Local Controla. Low PAO2 → vasoconstrictionb. Low PVCO2 → bronchoconstriction

Hemoglobin-O2 Binding Curve

0 20 40 60 80 100 120 1400

20

40

60

80

100

0

5

10

15

20

26

50

75

100

(100+75)/2=87.5(20+15)/2 =17.5

PaO2 (mm Hg)

% S

atur

atio

n of

Hem

oglo

bin

Hb-O

2 content(m

l O2 /100 m

l blood)

High

VA/Q.

.

Low

V A/Q..

Study Questions/ Exercises: Consider ½ of pulmonary blood flow going to regions where PAO2 is 150 mm Hg and the other ½ to a region of PAO2 = 40 mm Hg. Assume PACO2 is 30 and 50 mm Hg in these respective regions. How does PaO2 become less than normal while PaCO2 is normal?.

Hemoglobin-O2 Binding Curve

0 20 40 60 80 100 120 1400

20

40

60

80

100

0

5

10

15

20

26

50

75

100

(100+75)/2=87.5(20+15)/2 =17.5

87.5

54 m

mH

g

PaO2 (mm Hg)

% S

atur

atio

n of

Hem

oglo

bin

Hb-O

2 content(m

l O2 /100 m

l blood)

High

VA/Q.

.

Low

V A/Q.. High VA/Q

can’t compensateFor Low VA/Q

. .

. .

37 40 43 46 49 52

46

48

50

52

54

PCO2(mm Hg)

CO

2C

onte

nt(m

l CO

2/1

00 m

l blo

od)

30

High VA/Q. .

Low VA/Q. .

44

High VA/Q Compensates For Low VA/Q

. .

. .

Integratorin CNS

(Medulla)

SensorsChemoreceptors

Central &Peripheral

Control VariablesPO2, PCO2, pH

AfferentSensory

info

Efferentto motorneurons

EffectorsRespiratory Muscles

(e.g. Diaphragm)

Simple Negative Feedback System

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14

Arterial PO2 (mm Hg)

% m

axim

al fi

ring

rate

50 100 500

50

75

25

Peripheral Chemoreceptor ResponsivenessBBB CSFPlasma

CO2

HCO3

+

H+

CO2 ←→ HCO3 + H+

RespiratoryAcidosis (↑PaCO2)

Pumped

CNS Acidosis then HCO3 is pumped in(& restores pHCNS faster than kidneys can restore pHsystemic)

BBB CSFPlasma

CO2

HCO3

+

H+

CO2 ←→ HCO3 + H+

Metabolic Acidosis

Hyperventilation& ↓PaCO2

CNSAlkalosis !!!!

(then pump HCO3 out)

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15

ExpirDRGInspir

Higher Brain CentersPneumotaxic Center

Apneustic Center

Periph &CentralChemo-receptors

RespiratoryMuscles

VagusStretch

+

Toni

c In

spD

rive

Cut-off

ThreshAdjust

Cut

-off

+/–

Expiratory effort

+/–

30 60 900

10

20

30

40

50

60

PCO2 = 40 mm Hg

PCO2 = 45 mm Hg

PCO2 = 20 mm Hg

PaO2 (mm Hg)

Vent

ilatio

n (L

/min

)

Ventilatory Response to O2

35 40 45 50 550

20

40

60

PaO2 ≥ 200 mm Hg

PaCO2 (mm Hg)

Vent

ilatio

n (L

/min

)PaO2 ~100 mm Hg

PaO2 ~ 60 mm Hg

Ventilatory Response to CO2

35 40 45 50 550

10

20

30

40

50

NormalMetabolic Alkalosis

Metabolic Acidosis

PaCO2 (mm Hg)

Vent

ilatio

n (L

/min

)

Ventilatory Response to CO2

18,000 32,000 65,000 98,000Altitude (ft)0 10,000 20,000 30,000

0255075

100125150

PIO2

(PB -47)(0.21) -50

Altitude (ft)

P IO

2 (m

mH

g)

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16

EFFECTS OF HIGH ALTITUDE A. At 10,000 ft PB=525 mmHg inspired PO2 is ~100 mmHg ⇒PAO2 is ~50 mmHg. At 15,000 ft PB=380 mmHg inspired PO2 is ~70 mmHg ⇒PAO2 is ~20 mmHg. At Mt Everest PB=250 mmHg, inspired PO2 is ~42 mmHg ⇒PAO2 is ~0 mmHg. At 63,000 ft PB=47 mmHg, inspired PO2 is ~0 mmHg ⇒ tissues boils, H2O vapor. B. Acclimatization and hyperventilation at 10,000 ft Time at High Alt. PaO2 PaCO2 pH blood pH CSF VE [HCO3]

⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯ 1 Hr low low high high ↑ - Hypoxic drive is restrained by low PaCO2 and high pH. 1-2 day. low low high Norm. ↑↑ - CSF chemoreceptors no longer limiting hyperventilation. 2-4 days low low Norm. Norm. ↑↑↑ ↓ Peripheral alkalosis no longer restraining hyperventilation. 30 Yrs. low Norm. Norm. Norm. - - Hypoxic response of chemoreceptors lost.

BBB CSFPlasma

CO2

HCO3

+

H+

CO2 ←→ HCO3 + H+

RespiratoryAlkalosis

high pHCSF limits Hypoxic

Hyperventilation

When pHCNSreturns to norm (HCO3 pumped out)VE is less restrained.

EFFECTS OF HIGH ALTITUDE B. Acclimatization and hyperventilation at 10,000 ft Time at High Alt. PaO2 PaCO2 pH blood pH CSF VE [HCO3]

⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯ 1 Hr low low high high ↑ Normal Hypoxic drive is restrained by low PaCO2 and high pH. 1-2 day. low low high Norm. ↑↑ ↓[HCO3]CSF CSF chemoreceptors no longer limiting hyperventilation. 2-4 days low low Norm. Norm. ↑↑↑ ↓[HCO3]Syst Peripheral alkalosis no longer restraining hyperventilation. 30 Yrs. low Norm. Norm. Norm. - - Hypoxic response of chemoreceptors lost.

C. Other adjustments1, Polycythemia2. Enhanced Diffusing Capacity3. Imcreased Capillary Density4. Right shift of HbO2 curve

LA

LVRV

RA

Lung

Tissue

Placenta

SVC

IVC

FO

Aorta

DA

Lung

25

15

30

14

19

22

26

Low O2Hi Resist PA

PVPV

0 20 40 60 80 1000

5

10

15

20Myoglobin

Normal Hb

Anemia

Carbon Monoxide

PaO2 (mm Hg)

Hb-

O2

cont

ent

(ml O

2 /1

00 m

l blo

od)

LA

LVRV

RA

Lung

Tissue

Placenta

SVC

IVC

FO

Aorta

DA

Lung

25

15

30

14

19

2226

Hi O2Lo Resist

PVPV

95

95

95

40

40

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17

Equations Old ones you already knew ΔP=QR Ohm’s Law J=DA(ΔC/Δx) Fick’s Law JCO=DL-COPCO PV=nRT Universal Gas Law (Boyle’s & Charles’ Laws) Px= P Fx Dalton’s Law of Partial Pressures Cx = Px kSolubility Henry’s Law P=2T/r Law of LaPlace F= –kx Hooke’s Law R = 8ηl/πr4 Tubular resistance NR= ρDv/η Reynold’s Number CO2 + H2O ↔ H2CO3 ↔ HCO3

– + H+

RQ = V•CO2/V•O2 Respiratory Quotient

PTP= PAirway – PIP Transpulmonary P (Transmural) Derivable (simple algebra word problem) VL = VS([He]in – [He]fin)/[He]fin Helium Dilution VL = VS FEN2/FN2-air Nitrogen Washout New Ones! VD2 (PaCO2 – PECO2) ⎯⎯ = ⎯⎯⎯⎯⎯⎯⎯⎯ Bohr Eqn VT PaCO2 V•A = V•CO2 × k / PACO2 Alveolar Ventilation-PACO2 PAO2 = PIO2 – PaCO2/RQ Alveolar Gas Eqn