respiration 4

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3 RESPIRATORY SYSTEM

Structure and Functions of Lungs

Functions of the lungs (Viva)1. Taking in of O2 in the inspired air so as to supply O2 to all the tissues

of the body.

2. Giving away of CO2 which is metabolic waste product of the body &as it is toxic it has to be given out by the expired air.

3. For regulation of Ph of blood (normal Ph of blood is 7.3) This ismaintained at this level by giving out CO2 in expired air because CO2

will combine with water & form carbonic acid which will make the

blood highly acidic.


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Minor Functions4. Secretion of mucus thereby protecting the respiratory tract from dust,

smoke &other particles.

5. Excretion of alcohol & water vapour.6.

Absorption of chloroform & ether which are used as anesthesia beforeoperation.

Surfactant (short note & viva)

Surfactant which is lipoprotein is secreted by multilamellar bodies of the great

alveolar cells as shown in the figure.Surfactant is responsible for maintaining elasticity of the alveoli. Some times

newly born infant dies within a few days because of respiratory difficulty.

This is due to absence of surfactant in the infant therefore this disease is calledas Respiratory Distress Syndrome or Hyaline Disease.

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INTRA PLEURAL SPACE

Lungs are surrounded by 2 layers of pleura, parietal and visceral. Space

between these 2 layers is known as intra pleural space. This space is filledwith lubricating fluid. Pressure in this space is always negative i.e. 3 mm of

water during expiration and 9 mm of water during inspiration. The pressure

is always negative because of elastic reconcile of lung alveoli as shown in the

figure.

Importance of Intra Pleural Space

1. It gives protection to the lungs along with the 2 coverings of thelungs.

2. Because of negative pressure inspiration and expiration becomeseasy.

Pneumothorax (Viva)When there is presence of air in the pleural cavity it is known aspneumothorax.

Pneumothorax is of 3 types

1. Open pneumothorax2. Closed pneumothorax3. Valvular pneumothorax


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Open PneumothoraxAs shown in the diagram when the injury to the chest wall is minor i.e. up to

parietal layer of pleura the condition of the person may be difficult because of

following reason, air will always enter during respiration into intra pleuralspace where the pressure is always negative therefore gradually lung tissue

will retract or collapse because of large amount of air in the intra pleural spacepressing over the lungs.

Treatment: Suture the area and close the opening. This will prevent further

entry of air and the air inside will be gradually absorbed and the patient willrecover.

Closed Pneumothorax:When open pneumothorax is closed for treatment.

Valvular Pneumothorax: When the opening at the site of injury forms avalvular flap air will be going inside but not coming out thereby condition willbe worse within a short time.

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STUDY OF DIFFERENT PULMONARY VOLUMES (Viva)

The different pulmonary volumes are measured by an instrument known as

Spiro meter as follows

.1. Tidal air 500 cc.

It is the amount of air given out or taken in during normal respiration.

2. Inspiratory reserve volume 3000 cc.Maximum amount of air which can be taken in after the end ofnormal inspiration.

3. Expiratory reserve volume 1500 cc. (Half of above)It is the maximum amount of air which can be given out after the end

of normal expiration.

4. Residual air 1500 cc.It is the amount of air left in the lungs as residue after maximum

expiration

5. Dead space 300 cc.The air present in the trachea, bronchi and bronchioles where there is

no exchange of gases.

6. Vital capacity 5000 cc.It is the amount of the air which can be given out forcibly by

expiration after taking as much air as possible with maximuminspiration, this will include inspiratory reserve volume (3000 cc.) +

tidal volume (500 cc.) + expiratory reserve volume (1500 cc.) i.e.

total 5000 cc. (average 3000 to 5000 cc. )

7. Total lung volume 6000 7000 cc. i.e. vital capacity 5000 cc. +residual volume 1500 cc. = 6500 cc.


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VITAL CAPACITY(Short Note)

Definition: As already given above

Physiological Variation:

1. According to age : In children it is less, adults more & old age lessthan adults2. Sex: In females it is always less than male.3. Surface area: Vital capacity is always according to surface area i.e.

3.3 liters/Sq.m of body surface (normal body surface is 1.6 Sq.m in

the adults).4. Exercise: In adults vital capacity will be always more (5000 cc.)

when compare to persons of sedentary habits (3000 cc.).

5. Posture: In lying position vital capacity will be less when comparedwith standing position because in lying position lungs will be pressed

with the intestine thereby lowering the vital capacity.

Pathological Variation:Vital capacity will decrease in any one of the following lung diseases as

follows

1. Pneumonia2. Asthma

3. Collapse of the lungs

4. Oedema of the lungs5. Extensive tuberculosis of the lungs.

In chronic heart failure there will be difficulty of breathing which is due to

oedema of lung and this must be differentiated from lung diseases. Thereforewe see vital capacity is not important from diagnosis point of view because it

will give an idea only of possibility of so many lung diseases, rather it is

important from prognosis point of view. By this we mean whether the personis improving in the disease e.g. T.B. of the lungs when the vital capacity is

very low (2000 cc.) if by proper treatment the condition is improving then we

see that vital capacity is gradually increasing i.e. 3000 cc. then 4000 cc.. If notyour treatment is wrong.


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MECHANISM OF RESPIRATION

Describe the mechanism of respiration in the body?

Introduction:

Normal rate of respiration is 16 18 /min. It consists of inspiration andexpiration and the volume given in and given out (tidal air) = 500 cc.

Respiration is brought about by respiratory center present in the Medulla ofthe brain, with cooperation with inspiratory & expiratory muscles. It should be

remembered that inspiration is active process brought about by contraction of

thoracic cavity & expansion in all direction - Anterior, Anterioposterior,transverse & vertical diameter so that vacuum is created and air is sucked in

producing inspiration while expiration is a passive process brought about by

collapse of the lungs so that air is given out during expiration.The study of subject can be divided into 3 parts

1. Mechanics of respiration2. Study of respiratory center3. Actual mechanism of respiration

1. Mechanics of RespirationA. Mechanics of Inspiration: By this we mean how the expansion of

lungs are brought about to produce inspiration. Respiratory center in

the brain will only originate inspiration by passing impulses downwardto contract the inspiratory muscles (intercostals muscles & diaphragm

) to expand the thoracic cavity in all direction as follows1

st, 2

nd, 3

rd& 4

th ribs of the thorax will be moving upward and

outward thereby expanding in anterioposterior direction.5th

to 10th

ribs will move outward and forward thereby expanding in

transverse direction while diaphragm will move downward thereby

expanding in vertical direction.

Note: In heavy exercise accessory muscles of inspiration will come

into play e.g. pectoralis major, minor, sternocledomastoid muscle &

scalenus muscle. (11th & 12th ribs are floating ribs so no action)


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B. Mechanics of ExpirationAs it is passive process brought about by stoppage of inspirationtherefore collapsing the thoracic cavity so producing expiration.

Accessory muscles of expiration are abdominal muscles (transverse &

oblique) & pelvic muscles.

2. Role of Respiratory CenterThere is respiratory center in the medulla which is not a pin point centerlike the cardiac center & vasomotor center but it is about 1 to 2 cm. long.

There are 2 theories of this center.

1. Pitts theory2. Lums den theory

Pitts Theory: Stimulation of inspiratory center produces inspiration while

stimulation of expiratory center produces expiration but this can not explainactual mechanism of respiration therefore this theory is not accepted.


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3. Actual Mechanism of Respiration

The above figure explains inspiration on the right side and expiration on the

left side as already explained under the heading respiratory center.

One important reflex helping for producing expiration is Hering Breuerreflex which is explained as follows.As the lung alveoli expands during inspiration the sensory nerves ending of

the vagus are stimulated which will inhibit the Apneurtic center therefore by

this double inhibition (vagal, pneumotaxic) inspiration is stopped andexpiration brought about.


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REGULATION OF RESPIRATION

Describe the regulation of respiration in the body?

Introduction: Normal rate of respiration is 16 18 /min. but we have to

increase the rate of respiration more and more as we shall be doing moreexercise or work therefore to supply more O2 to the body. This is done by

several stimulating factors automatically acting directly on the respiratorycenter & acting indirectly or reflexly from the Sino aortic area. This is meant

by regulation of respiration.

Following diagram will explain this regulation of respiration

Explanation of diagram as follows

I. Factors acting directly on respiratory center.1. CO2 excess, O2 lack, high temperature will stimulate the center.

E.g. any muscular work when these two factors are there.


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Similarly high temperature as in fever increases the rate of

respiration.2. Opposite factors such as CO2 lack and low temperature will

inhibit the rate of respiration but this is rare and not important.

II.

Factors acting indirectly from Sino aortic area1. CO2 excess O2 lack & acidemia will be stimulating therespiratory system through chemo receptors of this area e.g.muscular exercise, while low B.P. will stimulate the respiratory

system through pressoreceptors of this area e.g. acute

accidental haemorrhage will increase the rate of respiration2. Opposite factors such as CO2 lack & alkalemia will lower the

respiratory rate through chemo receptors while increase of B.P.

decreases the heart rate through baroreceptors (not important).

III. Reflexes from other regions and from lungs1. Hering Breuer reflex i.e. vagus is inhibiting the respiratory

center but this reflex is only for normal respiration and not forregulation.

2. From joints: As there is more movement of the joints duringexercise or heavy work, this will stimulate respiratory center so

increase the rate of respiration e.g. more muscular exercise.

To understand properly the regulation of respiration : following factors will

help by stimulating the respiratory center therefore increasing the rate of

respiration CO2 excess, O2 lack, higher temperature will be acting andstimulating the respiratory center directly.

CO2 excess, O2 lack acidemia will be acting indirectly and stimulating therespiratory center and thereby increasing the rate of respiration.Movement of joints will also stimulate the respiratory center.

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OXYGEN CARRIAGE

Describe how O2 is carried in the body?

Main function of the lungs is carriage of O2 and carriage of CO2 i.e.O2 is taken

in by the lungs and CO2 is given out by the lungs.By O2 carriage we mean

1. How O2 is taken by the lungs.2. How O2 is given out from the blood to the tissues.

Here we will be describing how O2 is given to the tissues.

The subject can be studied under following.

1. Certain important data2. Forms in which O2 is carried3. Study of O2 dissociation curve.4. Actual O2 carriage

1. Certain important dataa. Composition of different air i.e. inspired air (atmospheric air),

expired air & alveolar air as shown in chart

Inspired Air Expired Air Alveolar Air

O2 20% 16% 14%

CO2 0.04% 4% 6%

N2 80% 80% 80%

b. Pressure and volume of O2 in arterial blood and venous bloodArterial Blood Venous Blood

OP 90mm of Hg 45mm of Hg

OV 19cc/100cc of blood 15cc/100cc of blood

c. Certain laws of gasesI. Pressure of a gas is due to its solution in liquid in physical

form (not in chemical form) i.e. not by HbO2 which is achemical form.


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II. Diffusion of gases takes place from higher pressure to lowerpressure till pressure on both side is equal.

2. Forms in which O2 is carried:It is carried in 2 forms

1.

HbO2 (chemical form) 19cc2. Physical solution 0.3cc3. Study of O2 dissociation curve. (Short note)

By this we mean, we study by the dissociation curve what are the factors

which will increase giving away of CO2 or O2 to the tissues.E.g. rise of temperature of body & rise of CO2 content in blood will

increase the rate of giving away of O2 in the tissue e.g. in muscular

exercise where both the two factors mentioned is present.

Dissociation curve is shown as follows

AO - at room temperature no CO2

BO - body temperature no CO2

CO - body temperature CO2 40mm of hg


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Here we see the curve shifting to the right by increase temperature i.e.

increase CO2 pressure which means more CO2 is given away & this effectis known as Bohr Effect.

4. Actual O2 carriage: This is shown & explained by the followingdiagram

The above figure shows the arterial & venous end of the capillary with O 2

pressure and volume. Pressure of O2 in the tissue is only 45 while O2 pressureon arterial side is 90 therefore O2 will be given away continuously from the

arterial side to the tissues. Like this 4cc of O2 is given out per 100cc of blood.Here one point should be remembered that pressure of O2 is by its physicalsolution which is only 0.3cc so O2 is given away from this physical source i.e.

(A) but the main depot is (B) 19cc as HbO2 . As HbO2 can be easily split this

O2 quickly goes in physical solution and then to the tissues.

Note: The whole process is reversed at the lungs where O2 is taken in

from the alveolar into the blood and this completes the whole carriage of

O2 in the body.


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CARBON DIOXIDE CARRIAGE

Describe the CO2 carriage in body or how CO2 is taken in from tissue into

blood?

IntroductionA large amount of CO2 is produced due to metabolism in the body & as this is

toxic this has to be removed therefore CO2 is taken from tissues to blood &this CO2 is given out by the lungs by expiration.

CO2 carriage can be studied under following.

1. Certain important data2. Form in which co2 is carried3. CO2 dissociation curve4. Actual mechanism of CO2 carriage

1. Certain important dataa. Composition of different air as shown below.Inspired Air Expired Air Alveolar Air

O2 20% 16% 14%

CO2 0.04% 4% 6%

N2 80% 80% 80%

b. Volume & pressure of CO2 in arterial & venous bloodArterial Blood Venous Blood

CO2 v 48 cc 52 ccCO2 p 40 mm of Hg 46 mm of Hg

c. Certain laws of gases Pressure of a gas is due to its solution in liquid in physical

form (not in chemical form).

Diffusion of gases taken place from higher pressure to lowerpressure till pressure on both side is equal.


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d. Enzyme: Here one enzyme called carbonic anhydrase will behelping CO2 carriage because CO2 + H2O H2CO3. This enzymeis mainly present in R.B.C. therefore this reaction taken place

quickly in R.B.C. for CO2 carriage.

e. Permeability of R.B.C. Membrane: - the membrane will allowas shown by arrow Cl & H2CO3 ion but it will not allow k & Naions

2. Forms in which CO2 is carrieda. Physical solution as H2CO3 i.e. solution in H2O - 3ccb. Chemical compound KHCO3 ( in R.B.C. ) - 10cc

CO2 mainly carried as NaHCO3 (in plasma) - 34ccc. Carbamino compound 3cc/50ccd. CO2 directly combine with Hb of R.B.C. and protein of plasma.

3. CO2 dissociation curve: By this dissociation curve of CO2 weunderstand following 2 factors.

1. Effect of temperature i.e. rise of temperature will give awaylarger amount of CO2 and vice versa.

2. Effect of O2 more oxygenation of the blood more CO2 will begiven away as its happens in the lungs.4. Actual mechanism of CO2 carriage:

Following is the diagram which will explain the carriage of CO2.

Here the different actions taking place in R.B.C. & plasma is givenseparately.


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As seen in the figure pressure of CO2 in the tissues is higher i.e. 46thanpressure of CO2 in arterial blood i.e. 40 therefore CO2 will pass from tissues

into the arterial blood till the pressure of CO2 become 46 on the venous side.

Reactions in R.B.C. as follows

1. CO2 combines with H2O to form H2CO3. This reaction begins inR.B.C. only because of presence of enzyme carbonic anhydrase in

R.B.C.

2. This H2CO3 combine with K salt of Hb i.e. KHb to form KHCO3.3. KHCO3 divide into ion form i.e. K & HCO3 & now there will be

exchange of ions between R.B.C. & plasma i.e. HCO3ions will

pass to plasma where it will combine with Na ions to formNaHCO3 equal to 34cc. On the other hand Cl ions from plasmawill pass into R.B.C. and combine with K ions to form KCl. This

whole exchange process is known as chloride shift.

4. CO2 will combine directly with Hb to form HbCO2 (only 3cc).


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Reaction in plasma1. CO2 will combine with H2O to form H2CO3 but very little &

carbonic anhydrase enzyme is absent in plasma.

2. The chloride shift as already explained.3.

CO2 will combine directly with protein of plasma to form PrCO2.

Note: The whole process is reversed in the lungs for giving away CO2from blood to thelungs alveoli.

CHLORIDE SHIFT (Short Note)

Chloride shift is concerned with the CO2 carriage. Here CO2 is taken up from

the tissues into the blood i.e. R.B.C. to form KHCO3 but again HCO3 ions ofKHCO3 will be transferred to plasma to combine with Na to form NaHCO3 in

which form it is carried in maximum quantity i.e. 34cc.

The different reactions are as follow.

Occurring in R.B.C.

1. CO2 + H2O H2CO32. H2CO3 + KHb KHCO3 + HHb

E.g. more exercise more will be formation of CO2.In muscular exercise large amount of CO2 is formed in the tissues. To help

this CO2 to be taken up quickly by the blood O2 will come into play because

there will be more & quick deoxygenation by the arterial blood. This

deoxygenation will help for taking up of CO2 quickly.


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HYPOXIA

What is hypoxia? Describe the effects of hypoxia on different system of

the body.

Hypoxia means when there is lack of O2 in the body due to any differentcauses. The main causes will be different diseases of the lungs. E.g. asthma,

diphtheria, pneumonia.

These will be studied in 3 different types of hypoxia.

1. Sudden & acute hypoxia.2. Moderate hypoxia.3. Slow or gradual hypoxia.

1. Sudden & acute hypoxiaa. This condition is very rare. E.g. when there is explosion in mines

the miners are surrounded by gases other than oxygen.b. In old abundant well where inside it is surrounded by CH4 gas.

Any person going inside will have acute hypoxia. Here the person

becomes unconscious within a minute so that he dies without any

symptom on different system of the body.

2. Moderate hypoxia: This is the most common type of hypoxia whendegree of hypoxia is moderate and not sudden e.g. diseases of the lungs,pneumonia, asthma & diphtheria. This type of hypoxia can also be studied

by inhaling & exhaling atmospheric air in a bag called Douglas bag. Here

gradually the O2 Of the bag will be used up & when the percentage of O2

falls from 20% to 14% there will be no symptom of hypoxia. Below 14%there will be all the symptom of moderate hypoxia described below.

Symptom of moderate hypoxia1. Nervous system: Here all the symptoms occur as if the person has

taken alcohol. His speech is affected i.e. he talks without any

sense. His gait (walking) is affected i.e. staggering gait. There ismental confusion, muscular weakness & headache.


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2. Cardio vascular system: The different cardiac center will bestimulated by hypoxia.a) Stimulation of cardiac center will produce increased rate of

heart increased cardiac output therefore the rise of blood

pressure.

b)

Vasomotor center stimulated therefore vaso constrictionstherefore rise in B.P.

3. Digestive system there will be nausea & vomiting and only liquidfood will be tolerated.

4. Respiratory system hypoxia will stimulate respiratory systemtherefore rate of respiration will increase 2 to 3 times than normal.There will be change in type of respiration which is periodic type

of breathing which is shown as follows.

That is height of respiration goes on rising then it goes on falling

followed by stoppage of respiration (apnea) & this goes onperiodically. This is due to washing away of CO2 in large amount

(more explanation will be given later on)

When O2 percentage is below 10 there will be cyanosis whichmeans hypoxia is extreme and the person may die.

3. Slow and gradual hypoxia (mountain sickness)This slow type of hypoxia occurs while climbing a mountain. There is lack

of O2 at high attitude because of the fact pressure of O2 at high altitude is

less & less therefore diffusion of O2 in the lungs will be less & therefore

hypoxia. Up to 12,000 feet there will be no lack of O2. Here the pressure


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of O2 is 500 mm of Hg (atmospheric pressure is 760 mm of hg). Above

12,000 feet symptoms of moderate hypoxia mentioned above.

All these symptoms appearing are known as mountain sickness.

In some persons it may appear early and in some cases it may appear after5 to 6 hours. Symptoms may be very bad i.e. convulsion of the body,unconsciousness and even paralysis.

After the height of 22,000, without O2 mask the person will have to take

ten times respiration after each step, therefore after 15,000 feet high the

mountaineers always use gas mask

What is hypoxia? Classify hypoxia and describe the different varieties of

hypoxia in detail to understand the different diseases of the lungs.

Hypoxia means lack of O2 in the body due to any causes.

Classification of hypoxia as follows.1. Anoxic hypoxia.2. Anaemic hypoxia.3. Stagnant hypoxia.4. Histotoxic hypoxia.

1. Anoxic hypoxia: The causes of anoxic hypoxia are as follows.Here one point is important to remember the amount of O2 we breathe willbe less so O2 going to the blood from the lungs will be less therefore

pressure of O2 in blood is less so supply of O2 to the tissues is less while in

other 3 varieties of hypoxia, (anaemic, stagnant and histotoxic) thepressure of O2 will be normal in the blood but still tissues will be supplied

less O2.

I. Causes in the air we breathe


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a) High attitude: Here the hypoxia is due to pressure of O2 which isless than atmospheric pressure.

b) Explosion in mines.c) Tear gas.

II.Obstruction in the air passage i.e. mouth, trachea and bronchi.a) Any foreign body in the passage e.g. marble or food particle.b) Asthmatic pressure due to spasm of bronchi.c) Diphtheria or due to enlarged tonsils therefore mechanical

obstruction of the air passage.

III.Diseases of the lungs: Because of the disease of the lungs diffusionof air we breathe through the lungs will be less therefore hypoxia. This

will be the main cause of hypoxia.

i. Pneumonia: Here lungs alveoli become solid due to infectiontherefore diffusion is affected.

ii.

Edema of lungs: Here there is accumulation of water in thelungs e.g. Drowning cases

iii. TuberculosisIV.Heart Disease: Patent foramina ovale: e.g. foramina ovale i.e. the hole

in the interventricular partition which generally closes before birth. In

some cases if it does not close before birth the venous blood of right

ventricle and arterial blood of left ventricle will mix together therefore

there will be hypoxia this is a congenital heart disease.

2. Anaemic hypoxiaExtreme anaemia due to any cause e.g. if the R.B.C. count is 3million/cc (normally 5 million) Hb will be less therefore O2 carried by

Hb will be less so hypoxia for the tissue.

Carbon mono oxide (CO) poisoning HbO2 is converted intoHbCO quickly because CO is 300 times more soluble than O2 with Hb

therefore in place of HbO2 we form HbCO in large amount producing

a condition like extreme anaemia (e.g. the hotel boys found dead in the

morning who were sleeping in a small room in a cold night shutting allthe doors and windows and the fire burning in the room. This fire will


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form large amount of CO & because of the above condition, boys

inhaling CO during sleep were found dead.)

3. Stagnant hypoxia: As the name suggest here there will be slowcirculation therefore less supply of O2 to the tissues producing hypoxia.

The main cause will be as follows.In heart failure when the muscle of the heart is weak therefore cardiac

output is less therefore slow circulation therefore hypoxia as explainedabove.

. Any condition producing shock as follows

a) Surgical shock i.e. after operation in some cases.b) Traumatic shock i.e. due to extensive trauma or extensive burn.c) Hemorrhagic shock e.g. when a large amount of blood is given out

(2 liters) after an accident. In the above cases of shock there is

always fall of B.P. therefore slow circulation and hypoxia.

4.

Histotoxic hypoxia : Here the tissue are poisoned as the name suggest O2supply in the tissues from the blood is by means of an enzyme cytochromeoxidase & if this is destroyed the tissue will not get O2 at all & the person

dies within 10 minutes e.g. taking a pinch of KCN will kill the person

within 10 minutes.

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DISORDERS OF BREATHING OR RESPIRATION(Short Note & Viva)

1. Hyperpnea2. Periodic type of breathing.3. Apnea4. Dyspnea5. Orthopnea

HYPERPNEAIt simply means whenever then is increased rate of respiration therefore

causes of hyperpnea will be all the causes producing hypoxia mainly the first3 i.e. anoxic, anaemic & stagnant hypoxia. They will be in short as follows.

a) High altitudeb) Obstruction in air passage- diphtheria & asthma.c) Diseases of lungs.

1. anoxic type2. Anoxic hypoxia i.e. in extreme anaemia.3. Stagnant hypoxia- when there is heart failure.

Effects of hyperpnea: This can be studied in a person having voluntaryhyperpnea which can be graphically recorded as follows.


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2. Pathological cause.I. Here all the 3 causes of hypoxia i.e. anoxic, anaemic & stagnant

a) anoxiccause in the airE.g. high attitude.

b) cause in air passageE.g. foreign body, diphtheria & asthmac) causes in the lungsE.g. lung disease i.e. pneumonia, collapse of lungs & edema.

II. Anaemic hypoxia e.g. extreme anaemic person while working.III. Stagnant hypoxia e.g. weakness of the heart i.e. heart failure & any

shock condition i.e. surgical shock or hemorrhagic shock.IV. High intracranial pressure e.g. accident when the skull is

damaged.V. Kidney failure i.e. (uremia)

APNEAIt means stoppage of breathing for sometime.

Classification of apnea as follows

1. Voluntary apnea: We can stop our breathing for sometimevoluntarily. There is always apnea after hyperpnea and also there is

apnea during periodic type of breathing.

2. Reflex apnea: Deglutition (swallowing) apneaHere when we swallow the food there is temporary stoppage of

breathing. This is because no food particle should enter the

respiratory passage i.e. trachea.

3. Vagal apnea: It can be seen in animal experiment. Stimulation ofvagus nerve produces reflex apnea i.e. sensory stimulation from the

vagus will reach respiratory center which will inhibit respiration andtherefore stop respiration.

E.g. normally this is required for normal respiration which is

known as Hering Breuer reflex.

4. Adrenaline apnea: in animal experiment it can be shown afterinjecting adrenaline there will be sudden rise of blood pressure due


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to vasoconstriction and this sudden rise of B.P. will inhibit or

depress the respiratory center thereby producing stoppage ofbreathing for apnea as shown in diagram

DYSPNEA

It means difficulty of respiration.Whenever there is lack of O2 to the body due to any cause the person will

have to increase his rate of respiration to get more O2.

Following points should be noted.1. When rate of respiration is normal the person is not aware of it

(16/min).

2. When the rate of respiration is double (32/min) the person becomesaware of his respiration.3. When the rate of respiration is more 3 or 4 times than the normal

(50-60/min) then the person feels difficulty of respiration which isknown as dyspnea.

Causes: We have to know the causes of dyspnea because by knowing thecauses we know the actual disease he is suffering from therefore we will be

able to give the proper treatment.


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Physiological causes:

a. Heavy exerciseb. living at high attitude above 18,000 feetc. hysteria

Pathological causes: all the causes of hypoxia are as follows.1. Anoxic hypoxia:a. Here causes in the air we breathe e.g. high altitude explosion in

mines, tear gas.

b. Causes in air passage producing obstruction e.g. foreign body,asthma and diphtheria.

c. Causes in the lungs: - here all the lung diseases e.g. pneumonia,extreme tuberculosis, collapse of lungs, edema of lungs.

d. Certain heart conditions e.g. congenital lung disease i.e. patentforamina ovale when the blood of right ventricle mixes with theleft ventricle.

2. Anaemic hypoxia :a. Severe anaemia due to any cause (R.B.C. 2-3 million/cc) only

during working.

b. CO poisoning3. Stagnant hypoxia :

a. Heart failure due to weakness of heart muscles.b. Shock due to any causes: here there is vasodilatation therefore

slow circulation and hypoxia e.g. shock after operation, shock after

acute hemorrhage.

(Viva only)

ORTHOPNEA: When the difficulty of respiration is too much the patient has

to sit and then only he feels more comfortable. This is known as orthopnea.

This is because the abdominal contents in sitting position will not hamper the

movement of diaphragm therefore respiration will be free.


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ACCLIMATIZATION

What is meant by acclimatization and how this is brought out by our

body? Or describe the mechanism how our body adjusts for living at high

attitude?

Introduction

Acclimatization means the adjustment of the body by different system forliving at higher attitude (more then 12,000 feet)

At this high attitude there will be hypoxia due to less pressure of O2 though

the percentage of O2 through the lungs is less and therefore hypoxia.Here the main problem is to supply more O2 to the body and this is mainly

done by the different system i.e. respiration C.V.S., kidney and blood. This

adjustment can be divided in 2 partsa. Immediate adjustmentb. Delayed adjustment

Immediate AdjustmentHere one point is important i.e. hypoxia itself will be acting as stimulant in

different centers and therefore helps to supply more O2 to the body.

1. Respiratory system , hypoxia will stimulate the respiratory systemthereby increasing the respiratory rate to supply more O2 but by increase

rate of respiration , it will be given out a large amount of CO 2 from theblood which is acid therefore the blood will become more alkaline and

we know this alkalinity of blood will directly depress or lower the rate of

respiration and this has to be checked, to keep on going increase rate of

respiration which is essential, here now the kidney will come into playas follows.

2. Role of kidney: The kidney will go on excreting large amount ofalkalinity therefore will not allow blood to become more alkalinethereby decreasing the depression effect on respiratory center.

3. Role of C.V.S.: Here hypoxia will stimulate the cardiac center thereforeincreasing the rate of heart therefore more cardiac output thereby morecirculation to the tissues and more O2 supply. Similarly hypoxia will


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80

stimulate vaso-motor center therefore vasoconstriction and rise of little

B.P so better O2 supply.

4. Role of blood: hypoxia will stimulate red bone marrow therefore largeamount of R.B.C. formation (from normal 5 million it will be increased

to 8 million) therefore large amount of Hb and more HbO2 i.e. more

supply of O2 . Also total blood volume increases from normal 5 liters to6 liters so more supply of O2.

Delayed AdjustmentBy these we mean when we live for a longer time at high attitude other

adjustment will also help for getting more O2 as follows.1. The lung volume: the vital capacity of the lung is increased because

of the constant increased rate and depth of respiration so better O2

supply.

2. Because of the constant greater expansion of lung alveoli the wallsof the alveoli becomes thinner therefore diffusion of O2 will be

easier.3. Red bone marrow will increase in quantity due to constantstimulation by hypoxia therefore R.B.C. formation is always larger.

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ASPHYXIA (Short Note)

It will mean lack of O2 together with excess of CO2 e.g. strangulation i.e.

complete chocking of trachea.The aspects of asphyxia can be divided as follows

Local asphyxia e.g. when a finger is tied tightly by thread therefore by

blocking artery as well as vein therefore the O2 supply i.e. hypoxia and CO2accumulating therefore local asphyxia.

General asphyxia: e.g. strangulation here the symptoms can be divided into 3stages. Total time taken for death is 6 minutes as follows.

1st

Stage 1 minute (stage of hyperpnea):Here CO2 excess only is the stimulant which will stimulate the respiratory

center therefore increased rate of respiration.

2nd

stage (stage of central excitation)-2 min.

Here the stimulating factor is both hypoxia & excess of CO2, now the person

becomes unconscious and all the signs of stimulation of sympathetic &

parasympathetic will occur as follows.1. Increased heart rate2. Increased B.P3. Increased saliva secretion4. Increased deep reflex action.

Here the breathing becomes difficult and expiration prolonged.

3

rd

stage stage of central depression (3 min)This is due to lack of O2 and the lack of O2 will damage all the centers of

brain and therefore there will be heart rate decreased, b.p decrease, reflexes

lost. Finally respiration becomes short and gasping and finally death.

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CYANOSIS (Short Note)

It simply means blue colouration of the skin and mucus membrane (Lips &

tongue). This blue colouration is due to the pigment reduced Hb. i.e. When Hbis devoid of oxygen.

Causes of cyanosis i.e. all the causes of hypoxia will produce cyanosis.

1. High altitude.2. Obstruction in air passage (foreign body & diphtheria, or asthma)3. Diseases of the lungs extreme pneumonia & collapse of lungs,

congenital disease of heart in children & congestive heart failure.

For producing cyanosis minimum amount of 5gm of reduced Hb should be

formed therefore an extremely anaemic person having only 4gm percentage ofHb will not be able to produce cyanosis because he can form only 4gms of

reduced Hb, but we require 5gms of reduced Hb for producing cyanosis.

Cyanosis can be of 2 types.1. Local cyanosis e.g. in extreme cold climate finger tips will become blue

or cyanose. This is due to

The peripheral circulation in the tip of finger is slow.

There will be vasoconstriction of the blood vessels therefore it will bestagnant type of hypoxia therefore cyanosis.

2. Generalized cyanosis i.e. when the skin of whole body becomes bluecolour, here all the causes of extreme hypoxia as mentioned above will

produce general cyanosis.

It should be noted in co poisoning i.e. HbCO which is an extreme form of

hypoxia will not produce cyanosis according to definition because thecolour of HbCO is not blue but cherry red.

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CAISONS DISEASE OR DECOMPRESSION SICKNESS

OR

COMPRESSED AIR SICKNESS

This peculiar condition we find in the sea divers who are in search of pearls

and they have to go at the bed of the sea for collecting sea shells.These fishermens were using the head gear called caison in which there was

air under high pressure (4 atm). In these persons when the head gear was

removed quickly they were found to suffer from following symptoms.

Extreme pain all over the body especially in joints, paralysis, unconsciousness& sometimes even death.

Cause of this is as followsBreathing air under high pressure, solubility of O2 in blood also increases

therefore if the pressure is suddenly released solubility of the gases will also

suddenly decreases and O2 & N2 gases will come out in bubbles, O2 bubbles

will be harmless as they will be quickly taken up by tissues & disposed but theN2 bubbles which are more soluble in fatty tissues will surround the nerve

fibers, producing pressure therefore extreme pain & paralysis. The bubblescirculating may also form clot & this clot may block the coronary artery of the

heart therefore severe heart attack and death.

Treatment is easy-you simply release the pressure of the chamber verygradually so that the bubbles of gas also come out very slowly therefore

having no effect.

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respiration 4

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