dr andreas lecture 12 re-upload

3/18/2013

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Respiratory Physiology

Lecture 2

Andreas W. Henkel, Ph.D.

Diagnosis of lung malfunction

Inhale

L/sec

Exhale

L/sec

Inspiratoryreserve vol.

Tidal vol.

Exspiratoryreserve vol.

Residual vol.

Respiration speed

Respiration

volume

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Diagnose stenoses with spirometer:

� No change in any volume

� Slower inhalation speed

� Slower exhalation speed


Inspiratoryreserve

Tidal

Exspiratoryreserve

residual

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Diagnose obstruction with spirometer:

� Residual volume is slightly increased

� Expiratory reserve volume is slightly

increased

� Inspiratory reserve volume is slightly

decreased

� Little slower inhalation speed

� Slower exhalation speed


Inspiratoryreserve

Tidal

Exspiratoryreserve

residual

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Diagnose Emphysema with spirometer:

� Residual volume is largely increased

� Expiratory reserve volume is slightly

increased

� Inspiratory reserve volume is largely

decreased


� Much slower exhalation speed


Inspiratoryreserve

Tidal

Exspiratoryreserve

residual

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Diagnose Restriction with spirometer:

� Expiratory reserve volume is decreased

� Inspiratory reserve volume is decreased


� Little slower exhalation speed

Gas partial pressure

Atmospheric pressure at sea level :

760 mm Hg (Mercury) = 760 torr

= 1013 millibar

Dalton’s law:

Pressure is sum of partial pressures

Partial pressure O2 =760 * 0.21 = 159

100 % water saturation at 37 C

= 47 mm Hg

The colder the water, the more gas can be

dissolved

Solubility depends on gas type

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Gas partial pressure

� Nitrogen (N2) 78.1%

� Oxygen (O2) 20.9%

� Argon (Ar) 0.9%

� Carbon dioxide (CO2) 0.038%

� Neon (Ne) 0.002%

� Helium (He) (0.000524%) Methane (CH4) 1.79 (0.000179%) , Krypton

(Kr) (0.000114%) , Hydrogen (H2) (0.000055%) ,Nitrous oxide (N2O)

(0.00003%), Xenon (Xe) (9 × 10−6%), Ozone (O3) (0% to 7 × 10−6%)

,Nitrogen dioxide (NO2) (2 × 10−6%), Iodine (I) (1 × 10−6%), Carbon

monoxide (CO) ,Ammonia (NH3) trace

Pressure distribution in

the atmosphere

human live zone

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Respiratory zone anatomy

Alveolar air

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Calculation of alveolar O2

Quantity Description Sample value

pAO2 The alveolar partial pressure of oxygen (pO2) 107 mmHg

FIO2

The fraction of inspired gas that is oxygen

(expressed as a decimal).0.21

PATM The prevailing atmospheric pressure 760 mmHg

pH2O

The saturated vapour pressure of water at

body temperature and the prevailing

atmospheric pressure

47 mmHg

paCO2

The arterial partial pressure of carbon

dioxide (pCO2)36 mmHg

RQ The respiratory quotient (CO 2/O2) 0.8

Sample values given for air at sea level at 37°C.

Calculation of alveolar O2

� The respiratory quotient (RQ) is

calculated from the ratio:

RQ = CO2 eliminated / O2 consumed

� carbon dioxide (CO2) removed

"eliminated“ from the body.

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Calculation of alveolar O2 in La Paz

Calculation of alveolar O2 in La Paz

� Air pressure at 3640 m = 484 torr

� Water vapor in alveoli = 100 % = 47 torr

� CO2 - pressure in air ~ 0 torr

� CO2 - pressure in alveoli = 42 torr

� Fraction of O2 in air = 0.21 = 21 %

� Respiratory quotient = 0.8

� PalveolarO2 = 0.21 *(484 – 47) – (42/0.8)

= 39.27 torr

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Respiratory zone

Alveolar airBlood

Gas exchange across this surface takes place driven entirely by DIFFUSION.R

esp

ira

tory

mem

bra

ne

Diffusion and respiratory function

Gas exchange across

respiratory membranes

-Differences in partial

pressure

-Small diffusion distance

-Lipid-soluble gases

-Large surface area of all

alveoli

-Coordination of blood flow

and airflow

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Blood gas transport

� O2 is carried in the blood as:

� 1. Dissolved gas (in plasma)

� 2. Bound to hemoglobin as oxyhemoglobin (Hb O2).

Blood

Alveoli

Heme-group contains Fe2+

Hemoglobin

Hemoglobin is composed of protein (globin)

and heme-groups

4 globins and 4 hemes = 1 hemoglobin molecule

Remember!

1 O2 binds to 1 Fe

O2

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Oxygen binding to hemoglobin

changes its structure

Blood O2 transport by

hemoglobin

Cooperative binding of O2

to hemoglobin1st O2

2nd O2

3rd O2

4th O2

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O2 content in blood

� Calculation:

Concentration of Hb in blood 110 -180 g

Normal Hb-saturation = 97%

1 g Hb can bind max. 1.34 ml O2

� Total O2 in blood = Hb-bound + free O2

= Hb max * saturation [%] + free O2

Gas transport control

� pH

� CO2

� Temperature

� DPG (2,3-Bisphosphoglyceric acid)makes it harder for oxygen to bind hemoglobin

and more likely to be released to adjacent tissues

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Control of O2 in the blood

Cyanosis

� How can you get blue blood ?

Inhibit hemoglobin binding capacity by carbon

monoxid (250 times better binding to Hb)

� Central cyanosis ventilatory problem slowing down of circulation

� Peripheral cyanosispoor circulation in the small vessels

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Oxygen Delivery

� Oxygen Delivery (DO2)

- Cardiac output (Qt)

- Hb content of blood

- Ability of the lung to oxygenate the blood

Total O2 delivered = Qt * O2 in arterial blood.

� Qt = 5 L / minute, alveoloar O2 = 20 %;

Lungs deliver 1 L of O2 to our tissues each minute.

CO2 transport in blood

CO2 is transported in blood…

as HCO3- ion = bicarbonate (90 %)

as dissolved CO2 (5 %)

as carbamino protein complexes (5 %)

Predominant transport mechanism of

CO2 is as HCO3- within the red blood cells

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CO2 transport in blood

� CO2 is transported as carbonate ion

� CO2 + H2O H2CO3 H+ + HCO3-

� Enzyme is Carbonic Anhydrase in RBC

� Chloride shift to compensate for

bicarbonate moving in and out of RBC

Enzymatic conversion of CO2

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Regulation of breathing

� Two major descending pathways from

the Medulla oblongata:

� 1. voluntary breathing

� 2. involuntary breathing

Controls of respiration

Medulla oblongata

in the brainstem

(integrator)

Input 1

Input 2 Input 3

Output

(via phrenic nerve)

Respiratory muscles

Input consists of 3 components:

1.The central & peripheral chemo receptors (input 1)

2.The pulmonary mechanoreceptors (input 2)

3. Input from reticular activation system, cerebral cortex, thalamus (input 3)

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Brain stem breathing centers

Rhythmic center in formatio

reticularis of medulla oblongata

I-neurons (inspiration) stimulate

spinal motoneurons

E-neurons (expiration) inhibit

I-neurons

Apneustic centre stimulates

I-neurons

Pneumotactic centre inhibits

apneustic centre

Chemo receptors provide

sensory input

1. Central chemo receptors

in Medulla oblongata

2. Peripheral chemo

receptors (aortic und

carotid bodies) provide

indirect input to Medulla

oblongata

O2, CO2 and pH are monitored

Arterial CO2 is the most

important!

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Motoric innervations of muscles

Cortical input (voluntary)

Ventilation, regulated by pH & CO2

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Blood gas abnormalities

� Oxygen toxicity:

100 % oxygen at 760 – 1500 mm Hg OK!

higher pressure > 1800 mm Hg enzyme and nerve damage

� Nitrogen narcosis (rapture of the deep):

long term exposure to high pressure >2500 mm Hg for > 1 h

like alcohol intoxication


� Decompression sickness

Only happens after prolonged stay at

high pressure.

Nitrogen forms bubbles, when a diver

ascents to fast.

Obey decompression tables

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� Stagnant hypoxia: intravascular stasis.

Decreased venous outflow of blood from

tissue.

� Anemic hypoxia: decreased concentration

of functional hemoglobin or low RBC count

� Hypoxic hypoxia: defective mechanism of

oxygenation in the lungs


� Arterial hypoxemia : arterial PaO2 is to low. An arterial PaO2 less than 80 mm Hg is abnormal

� Hypoxia: insufficient oxygen to carry out normal metabolic functions. Thus, hypoxia and hypoxemia are frequently used interchangeably.

� Hypercapnia : increase in arterial PaCO2 above 40 ±2 mm Hg

� Hypocapnia : abnormally low arterial PaCO2 (less than 35 mm Hg).

dr andreas lecture 12 re-upload

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