Disturbances of Respiration Physiology Notes

Disturbances of Respiration

 Introduction

Eupnea refers to normal respiration. Following are the terms used for some of the altered patterns of respiration:

1. Tachypnea: The increase in the rate of respiration
2. Bradypnea: The decrease in the rate of respiration
3. Polypnea: Rapid, shallow breathing resembling panting in dogs.  In this type of breathing, only the rate of respiration increases but the force does not increase significantly
4. Apnea: Temporary arrest of breathing
5. Hyperpnea: Increase in pulmonary ventilation due to an increase in rate or force of respiration.  An increase in the rate and force of respiration occurs after exercise. It also occurs in abnormal conditions like fever or other disorders
6. Hyperventilation: Abnormal increase in rate and force of respiration which often leads to dizziness and sometimes chest pain
7. Hypoventilation: Decrease in rate and force of respiration
8. Dyspnea: Difficulty in breathing
9. Periodic breathing: The abnormal respiratory rhythm.

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Apnea

Apnea Definition:

• Apnea is defined as a temporary cessation of breathing, f Literally, apnea means the absence of breathing. Apnea can also be maintained voluntarily which is called breath-holding or voluntary apnea.

Apnea Time: The breath-holding time is known as apnea time. It is about 40-60 seconds in a normal person, after a deep inspiration.

Conditions When Apnea Occurs:

1. Voluntary effort
2. Apnea after hyperventilation
3. Deglutition apnea
4. Vagal apnea
5. Adrenaline apnea.

Voluntary Effort:

• Arrest of breathing by voluntary effort is known as voluntary apnea or breath holding.
• Though the breath holding time is 40-60 seconds, it can be increased by practice, exercise willpower, and yoga.
• At the end of voluntary apnea, the subject is forced to breathe, which is called the breaking point.
• It is because of the accumulation of carbon dioxide in the blood, which stimulates the respiratory centers resulting.
• Besides increased carbon dioxide content in blood, hypoxia and increased hydrogen ion concentration are also responsible for the stimulation of respiratory centers. Apnea is always followed by hyperventilation.

Apnea after Hyperventilation:

• Apnea occurs after hyperventilation. It is due to the lack of carbon dioxide. During hyperventilation, more carbon dioxide is washed out.
• So, the partial pressure of carbon dioxide in the blood decreases and the number of stimuli to the respiratory centers also decreases leading to apnea.
• During apnea, carbon dioxide accumulates in the blood. When the partial pressure of carbon dioxide increases, the respiratory centers are stimulated and respiration starts.

Deglutition Apnea:

•  The arrest of breathing during deglutition is known as deglutition (swallowing) apnea. It occurs reflexly during a pharyngeal stage of deglutition.
• When the bolus is pushed into the esophagus from the pharynx during a pharyngeal stage of deglutition, there is a possibility for the bolus to enter the respiratory passage through the larynx, causing serious consequences like choking.
• This is prevented by deglutition apnea during which the larynx is closed by the backward movement of the epiglottis.

Vagal Apnea:

• It is an experimental apnea, which is produced by the stimulation of the vagus nerve in animals. Stimulation of the vagus nerve causes apnea by inhibiting the inspiratory center

Adrenaline Apnea:

• It is the apnea that occurs after the injection of adrenaline. Administration of adrenaline produces a marked increase in arterial blood pressure.
• It stimulates the baroreceptors, which in turn reflexly inhibit the vasomotor center, and the respiratory centers causing a fall in blood pressure and apnea.

Clinical Classification Of Apnea:

Clinically, apnea is classified into three types:

1. Obstructive apnea
2. Central apnea
3. Mixed Apnea.

Obstructive Apnea:

• Obstructive apnea occurs because of obstruction in the respiratory tract. Respiratory tract obstruction is mainly due to excess tissue growth like tonsils and adenoids.
• The most common obstructive apnea is sleep apnea.

Sleep apnea:

• Sleep apnea is the temporary stoppage of breathing that occurs repeatedly during sleep. It is also called sleep-disordered breathing (SDB). It commonly affects overweight people.
• The major cause of sleep apnea is obstruction of the upper respiratory tract by excess tissue growth in airways like enlarged tonsils and large tongue.
• The characteristic feature of sleep apnea is loud snoring. Snoring without sleep apnea is called simple or primary snoring.
• But snoring with sleep apnea is serious and it may become life threatening. If left unnoticed, it may lead to hypertension, heart failure, and stroke .

Central Apnea:

• Central apnea occurs due to brain disorders, especially when the respiratory centers are affected.
• It is seen in premature babies. The typical feature of central apnea is a short pause between breathing.

Mixed Apnea:

• Mixed apnea is a combination of central and obstructive apnea. It is usually seen in premature babies and in full-term born infants.
• The main reason for mixed apnea is the abnormal control of breathing due to an immature or underdeveloped brain or respiratory system.

Hyperventilation

Hyperventilation Definition:

• Hyperventilation means increased pulmonary ventilation due to forced breathing. It is also called over-ventilation.
• In hyperventilation, both rate and force of breathing are increased, and a large amount of air moves in and out of the lungs.
• Thus, pulmonary ventilation is increased to a great extent. Very often hyperventilation leads to dizziness, discomfort, and chest pain.

Conditions When Hyperventilation Occurs:

• Hyperventilation mostly occurs in conditions like exercise when the partial pressure of carbon dioxide is increased. Excess carbon dioxide stimulates the respiratory centers.
• Voluntarily also, hyperventilation can be produced. It is called voluntary hyperventilation.

Effects Of Hyperventilation:

• During hyperventilation, excessive carbon dioxide is washed out. And, in blood, the partial pressure of carbon dioxide is reduced.
• It causes suppression of respiratory centers resulting in apnea. Apnea is followed by Cheyne- Stokes type of periodic breathing. After a period of Cheyne-Stokes breathing, normal respiration is restored.

Hypoventilation

Hypoventilation Definition:

• Hypoventilation is the decrease in pulmonary ventilation caused by a decrease in the rate or force of breathing. Thus, the amount of air moving in and out of the lungs is reduced.

Conditions When Hypoventilation Occurs:

• Hypoventilation occurs when respiratory centers are suppressed or by administration of some drugs. It occurs during partial paralysis of respiratory muscles also.

Effects Of Hypoventilation:

• Hypoventilation results in the development of hypoxia along with hypercapnia. It increases the rate and force of respiration leading to dyspnea. Severe conditions result in lethargy, coma, and death.

Hypoxia

Hypoxia Definition:

• Hypoxia is defined as the reduced availability of oxygen to the tissues. The term anoxia refers to an absence of oxygen.
• In the olden days, the term anoxia was in use. Since there is no possibility of total absence of oxygen in living conditions, the use of this term is abandoned.

Classification And Causes Of Hypoxia:

Four important factors which lead to hypoxia are:

1. Oxygen tension in arterial blood
2. Oxygen-carrying capacity of blood
3. Velocity of blood flow
4. Utilization of oxygen by the cells.

On me basis of these factors, hypoxia is classified tiro four types:

• Hypoxic hypoxia
• Anemic hypoxia
• Stagnant hypoxia
• Histotoxic hypoxia.

Each type of hypoxia may be acute or chronic. Simultaneously, two or more types of hypoxia may be present.

Hypoxic Hypoxia: Hypoxic hypoxia means the decreased oxygen content in the blood. It is also called arterial hypoxia.

Causes for hypoxic hypoxia:

Hypoxic hypoxia is caused by four factors.

• Low oxygen tension in inspired (atmospheric) air which does not provide enough oxygen
• Respiratory disorders associated with decreased pulmonary ventilation which does not allow intake of enough oxygen
• Respiratory disorders associated with inadequate oxygenation in lungs which does not allow diffusion of enough oxygen
• Cardiac disorders in which enough blood is not pumped to transport oxygen.

Low oxygen tension in inspired air:

The oxygen tension in inspired air is reduced in the following conditions:

1. High altitude
2. While breathing air in a closed space
3. While breathing a gas mixture containing low partial pressure of oxygen.
4. Because of these conditions, required quantity of oxygen cannot enter the lungs.

Respiratory disorders associated with decreased pulmonary ventilation

Pulmonary ventilation decreases in the following conditions:

1. Obstruction of respiratory passage as in asthma
2. Nervous and mechanical hindrance to respiratory movements as in poliomyelitis
3. Depression of respiratory centers as in brain tumors
4. Pneumothorax.
5. In these conditions, even though enough oxygen is available in the atmosphere, it cannot reach the lungs.

Respiratory disorders associated with inadequate oxygenation of blood in lungs
Oxygenation of blood in lungs reduces by the following conditions:

1. Impaired alveolar diffusion as in emphysema
2. Presence of nonfunctioning alveoli as in fibrosis
3. Filling of alveoli with fluid as in pulmonary edema, pneumonia, pulmonary hemorrhage
4. Collapse of lungs as in bronchiolar obstruction
5. Lack of surfactant.
6. Abnormal pleural cavity such as pneumothorax, hydrothorax, hemothorax and pyothorax.
7. Increased venous admixture as in the case of bronchiectasis.
8. In these conditions, in spite of oxygen availability and entrance of oxygen into the alveoli, it cannot diffuse into the blood.

Cardiac disorders:

• Congestive heart failure: In this condition, oxygen availability and diffusion are normal but the blood cannot be pumped from heart properly.
• Characteristic features of hypoxic hypoxia
  The only problem is the reduced oxygen tension in arterial blood. All other features remain normal.

Anemic Hypoxia:

• Anemic hypoxia is a condition characterized by the inability of blood to carry enough amount of oxygen.
• The oxygen availability is normal. But the blood is not able to take up a sufficient amount of oxygen due to an anemic condition.

Causes of anemic hypoxia:

Any condition that causes anemia can cause anemic hypoxia.

It occurs because of the following conditions:

1. Decreased number of RBCs
2. Decreased hemoglobin content in the blood
3. Formation of altered hemoglobin
4. Combination of hemoglobin with gases other than oxygen and carbon dioxide.

Characteristic features of different types of hypoxia.

Decreased number of RBCs: Red cell count decreases in conditions like bone marrow diseases, hemorrhage, etc.

Decreased hemoglobin content in the blood:

• The conditions which decrease the number of RBC or change the structure, shape and size of RBC (microcytes, macrocytes, spherocytes, sickle cells, poikilocytes, etc.) can decrease hemoglobin content in blood.

Formation of altered hemoglobin:

• Poisoning with chlorates, nitrates, ferricyanides, etc. causes oxidation of iron into ferric form, and the hemoglobin is known as methemoglobin.
• Methemoglobin cannot combine with oxygen. Thus, the quantity of hemoglobin available for oxygen transport is decreased.
• Combination of hemoglobin with gases other than oxygen and carbon dioxide When hemoglobin combines with carbon monoxide, hydrogen sulfide or nitrous oxide it looses the capacity to transport oxygen.

Characteristic features of anemic hypoxia:

• The only problem in this type of hypoxia is that the blood cannot carry sufficient oxygen. All other features remain normal.

Stagnant Hypoxia:

It is the hypoxia caused by decreased velocity of blood flow. It is otherwise called hypokinetic hypoxia.

Causes of stagnant hypoxia: Stagnant hypoxia occurs mainly due to reduction in velocity of blood flow.

The velocity of blood flow decreases in the following conditions:

1. Congestive cardiac failure
2. Hemorrhage
3. Surgical shock
4. Vasospasm
5. Thrombosis
6. Embolism.

Characteristic features of stagnant hypoxia: Here, the only problem is decreased velocity of blood flow. All other features remain normal.

Histotoxic Hypoxia: It is the type of hypoxia produced by the inability of tissues to utilize oxygen.

Causes for histotoxic hypoxia:

• Histotoxic hypoxia occurs due to cyanide or sulfide poisoning. These poisonous substances destroy the cellular oxidative enzymes and there is complete paralysis of cytochrome oxidase system.
• So, even if oxygen is supplied, the tissues are not in a position to utilize it.

Characteristic features of histotoxic hypoxia:

• Here, the only problem is the tissues are not able to use the oxygen even if it is delivered. All other features remain normal.

Effects Of Hypoxia: Acute and severe hypoxia leads to unconsciousness. If not treated immediately, brain death occurs.

Chronic hypoxia produces various symptoms in the body. Generally, the effects of hypoxia are of two types.

1. Immediate effects
2. Delayed effects.

Immediate Effects:

Effects on blood:

• Hypoxia stimulates juxtaglomerular apparatus of kidneys and increases the secretion of erythropoietin.
• Erythropoietin in turn stimulates the red bone marrow. So, the RBC count increases with an increase in reticulocyte count.
• Thus, the oxygen-carrying capacity of blood is improved by increase in RBC count and hemoglobin content.

Effects on cardiovascular system:

• Initially, due to the reflex stimulation of cardiac and vasomotor centers, there is increase in rate and force of contraction of heart, cardiac output and blood pressure.
• Later, there is reduction in the rate and force of contraction of heart. Cardiac output and blood pressure are also decreased.

Effects on respiration:

• Initially, the respiratory rate is increased due to chemoreceptor reflex.
• Because of this large amount of carbon dioxide is washed out leading to alkalemia Later, the respiration tends to be shallow and periodic.
• Finally, the rate and force of breathing are reduced to a great extent due to the failure of respiratory centers.

Effects on digestive system:

• Hypoxia is associated with loss of appetite, nausea, and vomiting. Mouth becomes dry and there is a feeling of thirst.

Effects on kidney:

• Hypoxia causes increased secretion of erythropoietin from the juxtaglomerular apparatus. And, alkaline urine is excreted.

Effects on central nervous system:

• In mild hypoxia, the symptoms are similar to those of alcoholic intoxication.
• The individual is depressed, apalhic with general loss of self control. The person becomes talkative, quarrelsome, ill tempered and rude. The subject starts shouting, singing or crying.
• There is disorientation, and loss of discriminative ability and loss of power of judgment. Memory is impaired. Weakness, lack of coordination and fatigue of muscles are common in hypoxia.
• If hypoxia is acute and severe, there is sudden loss of consciousness. If not treated immediately, coma occurs which leads to death.

Delayed Effects of Hypoxia:

• The delayed effects appear depending upon the length and severity of the exposure to hypoxia.
• The person becomes highly irritable, and the symptoms of mountain sickness appear. The symptoms are nausea, vomiting, depression, weakness and fatigue.

Treatment For Hypoxia-Oxygen Therapy:

• The best treatment for hypoxia is oxygen therapy, i.e. treating the affected person with oxygen. Pure oxygen or oxygen combined with another gas is administered.

Oxygen therapy is carried out by two methods:

• By placing the patient’s head in a ‘tent’ containing oxygen
• By allowing the patient to breathe oxygen either from a mask or an intranasal tube.
• Depending upon the situation, oxygen therapy can be given either under normal atmospheric pressure or under high pressure (hyperbaric oxygen).

In Normal Atmospheric Pressure:

• With normal atmospheric pressure, i.e. at one atmosphere (760 mm Hg), administration of pure oxygen is well tolerated by the patient for long hours.
• However, after 8 hours or more, lung tissues show fluid effusion and edema.
• The other tissues are not affected very much because of hemoglobin – oxygen buffer system.

In High Atmospheric Pressure – Hyperbaric Oxygen:

• Hyperbaric oxygen is the pure oxygen with high atmospheric pressure of two or more than two atmospheres. Hyperbaric oxygen therapy with 2-3 atmospheres is tolerated by the patient for about 5 hours.
• During this period, the dissolved form of oxygen increases in arterial blood because the oxygen carrying capacity of hemoglobin is limited. At this level, tissue oxygen tension also increases to about 200 mm Hg.
• However, tissues tolerate the high partial pressure of oxygen without much adverse effects. But, oxygen toxicity develops when pure oxygen is administered for long periods Refer oxygen toxicity below.

Efficacy of Oxygen Therapy in Different Types of Hypoxia:

• Oxygen therapy is the best treatment for hypoxia. But it is not effective equally in all types of hypoxia. The value of oxygen therapy depends upon the type of hypoxia.
• So, before deciding the oxygen therapy, one should recall the physiological basis of different types of hypoxia.
• In hypoxic hypoxia, the oxygen therapy is 100% useful. In anemic hypoxia, oxygen therapy is moderately effective to about 70%. In stagnant hypoxia, the effectiveness of oxygen therapy is less than 50%.
• In histotoxic hypoxia, the oxygen therapy is not useful at all. It is because, even if oxygen is delivered, the cells cannot utilize oxygen.

Oxygen Toxicity (Poisoning)

Definition And Cause:

• Oxygen toxicity is the increased oxygen content in tissues beyond certain critical level.
• It is also called oxygen poisoning. It occurs because of breathing pure oxygen with high pressure of 2-3 atmospheres (hyperbaric oxygen).
• In this condition, an excess amount of oxygen is transported in plasma as dissolved form because the oxygen carrying capacity of hemo-globin is limited to 1.34 mL/g.

Effects Of Oxygen Toxicity:

1. Lung tissues are affected first with tracheobronchial irritation and pulmonary edema
2. The metabolic rate increases in all the body tissues and the tissues are burnt out by excess heat. The heat also destroys cytochrome system leading to damage of tissues
3. When brain is affected, first hyperirritability occurs. Later, it is followed by increased muscular twitching, ringing in ears and dizziness
4. Finally, the toxicity results in convulsions, coma and death.

Hypercapnea

Hypercapnea Definition: Hypercapnea is the increased carbon dioxide content of blood.

Conditions When Hypercapnea Occurs:

Hypercapnea occurs in conditions, which leads to blockage of respiratory pathway such as asphyxia, it also occurs while breathing air containing excess carbon dioxide content.

Effects Of Hypercapnea:

Effects on Respiration: During hypercapnia, the respiratory centers are stimulated excessively. It leads to dyspnea.

Effects on Blood: The pH of blood reduces and, the blood becomes acidic.

Effects on Cardiovascular System:

• Hypercapnia is associated with tachycardia and increased blood pressure.
• There is flushing of the skin due to peripheral vasodilatation.

Effects on Central Nervous System:

• During hypercapnia, the nervous system is also affected resulting in headaches, depression, and laziness.
• These symptoms are followed by muscular rigidity, fine tremors, and generalized convulsions. Finally, giddiness and loss of consciousness occur.

Hypocapnea

Hypocapnea Definition: Hypocapnea is the decreased carbon dioxide content in the blood.

Conditions When Hypocapnea Occurs: Hypocapnea occurs in conditions associated with hypo-ventilation.  It also occurs after prolonged hyperventilation because of washing out of excess carbon dioxide.

Effects Of Hypocapnea:

1. Effects on Respiration: The respiratory centers are depressed leading to decreased rate and force of respiration.

2. Effects on Blood:

• The pH of blood increases leading to respiratory alkalosis. Calcium concentration decreases.
• It causes tetany, which is characterized by neuromuscular hyperexcitability and carpopedal spasm.

3. Effects on Central Nervous System: Dizziness, mental confusion, muscular twitching, and loss of consciousness are the common features of hypo-apnea.

 Asphyxia

 Asphyxia Definition:

• Asphyxia is a condition characterized by a combination of hypoxia and hypercapnia due to obstruction of the air passage.

Conditions When Asphyxia Occurs:

Axphyxia develops in conditions characterized by acute obstruction of air passage such as:

1. Strangulation
2. Hanging
3. Drowning, etc.

1. Effects Of Asphyxia:

The effects of asphyxia develop in three stages:

1. Stage of hyperpnea
2. Stage of convulsions
3. Stage of collapse.

2. Stage of Hyperpnea:

• Hyperpnea is the first stage of asphyxia. It extends for about 1 minute. In this stage, breathing becomes deep and rapid.
• It is due to the powerful stimulation of respiratory centers by excess of carbon dioxide.
• Hyperpnea is followed by dyspnea and cyanosis. The eyes become more prominent.

3. Stage of Convulsions: This stage is characterized mainly by convulsions (uncontrolled involuntary muscular contractions).

The duration of this stage is less than one minute. The following effects develop in this stage due to the effect of hypercapnia on other centers in the brain and spinal cord:

1. Expiratory efforts become more violent
2. Generalized convulsions appear
3. Heart rate increases
4. Arterial blood pressure greatly increases
5. Consciousness is lost.

Stage of Collapse:

This stage lasts for about three minutes. The effects of this stage are:

1. Depression of centers in brain due to lack of oxygen. So, the convulsions disappear
2. Respiratory gasping occurs. During respiratory gasping, there is stretching of the body with the opening of mouth as if gasping for breath
3. Pupils are dilated
4. Heart rate is reduced
5. All the reflexes are abolished
6. The duration between the gasps gradually increased
7. Finally, death occurs.
8. Altogether, asphyxia extends only for 5 minutes. The person can be saved by timely help such as resivir^ the respiratory obstruction, good aeration, etc. Otherwise, death occurs.

Dyspnea

Dyspnea Definition:

• Dyspnea means difficulty in breathing. It is otherwise called air hunger.
• Normally, breathing goes on without consciousness.
• When breathing enters the consciousness and produces discomfort, it is called dyspnea.
• Dyspnea is also defined as “a consciousness of the necessity for increased respiratory effort”.

Dyspnea Point:

• Dyspnea point is the level at which there is increased ventilation with severe breathing discomfort.
• The normal person is not aware of any increase in breathing until the pulmonary ventilation is doubled.
• The real discomfort develops when the ventilation increases by 4 or 5 times.

Conditions When Dyspnea Occurs:

Physiologically, dyspnea occurs during severe muscular exercise.

The pathological conditions when dyspnea occurs are:

1. Respiratory Disorders: Dyspnea occurs in respiratory disorders characterized by mechanical or nervous hindrance to respiratory movements and obstruction in any part of the respiratory tract.

Thus, dyspnea occurs in:

1. Pneumonia
2. Pulmonary edema
3. Pulmonary effusion
4. Poliomyelitis
5. Pneumothorax
6. Severe asthma, etc.

2. Cardiac Disorders: Dyspnea is common in left ventricular failure and decompensated mitral stenosis.

3. Metabolic Disorders: The metabolic disorders which cause dyspnea are diabetic acidosis, uremia, and increased hydrogen ion concentration.

Dyspneic Index

• Dyspneic index is the index between breathing reserve and maximum breathing capacity.
• Breathing reserve is -be balanced (difference) between maximum breathing capacity (MBC) and respiratory minute volume (RMV).

For example, in a normal subject, MBC =116 liters and RMV = 6 liters.

Dyspnea develops when the dyspneic index decreases below 60%.

Periodic Breathing

Definition And Types:

Periodic breathing is the abnormal or uneven respiratory rhythm. It is of two types:

1. Cheyne-Stokes breathing
2. Biot’s breathing.

Cheyne-Stokes Breathing:

Features of Cheyne-Stokes Breathing Cheyne-Stokes breathing is periodic breathing characterized by rhythmic hyperpnea and apnea. It is the most common type of periodic breathing.

It is marked by two alternate patterns of respiration:

1. Hyperpneic period
2. Apneic period

1. Hyperpneic period – waxing and waning of breathing:

• To begin with, the breathing is shallow. The force of respiration increases gradually and reaches the maximum (hyperpnea).
• Then, it decreases gradually reaches the minimum, and is followed by apnea.
• The gradual increase followed by a gradual decrease in the force of respiration is called the waxing and waning of breathing.

2. Apneic period:

• When the force of breathing is reduced to a minimum, cessation of breathing occurs for a short period.
• It is again followed by a hyperpneic period and the cycle is repeated. The duration of one cycle is about one minute. Sometimes waxing and waning of breathing occurs without apnea.

3. Causes for Waxing and Waning:

• Initially, during forced breathing, a large quantity of carbon dioxide is washed out from the blood. When carbon dioxide tension becomes low, the respiratory centers become inactive.
• It causes apnea. During apnea, there is an accumulation of carbon dioxide and a reduction in oxygen tension.
• Now, the respiratory centers are activated resulting in a gradual increase in the force of breathing. And when the force of breathing reaches a maximum, the cycle is repeated.
• Conditions when Cheyne-Stokes Breathing Occurs
• Cheyne-Stokes breathing occurs in both physiological and pathological conditions.

Physiological conditions when Cheyne-Stokes breathing occurs:

1. During deep sleep
2. In high altitude
3. After prolonged voluntary hyperventilation
4. During hibernation in animals
5. In newborn babies
6. After severe muscular exercise.

Pathological conditions when Cheyne-Stokes breathing occurs

1. During increased intracranial pressure
2. During advanced cardiac diseases leading to cardiac failure
3. During advanced renal diseases leading to uremia
4. Poisoning by narcotics
5. In premature infants.

Biots Breathing:

1. Features of Biot’s Breathing:

• It is another form of periodic breathing characterized by periods of apnea and hyperpnea.
• There is no waxing and waning of breathing. After an apneic period, hyperpnea occurs abruptly.

2. Causes of Abrupt Apnea and Hyperpnea:

• Due to apnea, carbon dioxide accumulates and it stimulates the respiratory centers leading to hyper-ventilation.
• During hyperventilation, a lot of carbon dioxide is washed out. So, the respiratory centers are not stimulated and apnea occurs.

3. Conditions when Biot’s Breathing Occurs:

• Biot’s breathing does not occur in physiological conditions.
• It occurs only in pathological conditions. It occurs in conditions involving nervous disorders, due to lesions or injuries to the brain.

Cyanosis

Cyanosis Definition:

• Cyanosis is defined as the diffused bluish coloration of skin and mucus membranes. It is due to the presence of a large amount of reduced hemoglobin in the blood.
• The quantity of reduced hemoglobin should be at least 5-7 g/dL in the blood to cause cyanosis.

1. Distribution Of Cyanosis:

• When it occurs, cyanosis is distributed all over the body.
• But, it is more marked in certain regions where the skin is thin.
• These areas are the lips, cheeks, ear lobes, nose, and fingertips above the base of the nail.

2. Conditions When Cyanosis Occurs:

• Any condition which leads to arterial hypoxia and stagnant hypoxia. Cyanosis does not occur in anemic hypoxia because the hemoglobin content itself is less.
• It does not occur in histotoxic hypoxia because of tissue damage.
• Conditions when altered hemoglobin is formed. Due to poisoning, hemoglobin is altered into methe- myoglobin or sulfhemoglobin, which causes cyanosis.
• The cyanotic discoloration is due to the dark color of these compounds only and not due to reduced hemoglobin
• Conditions like polycythemia when blood flow is slow. During polycythemia, because of increased RBC count, the viscosity of blood is increased.
• And, It leads to the sluggishness of blood flow. So the quantity of deoxygenated blood increases which causes bluish discoloration of the skin.

Cyanosis And Anemia:

• Cyanosis usually occurs only when the quantity of reduced hemoglobin is about 5-7 g/dL.
• But, in anemia, the hemoglobin content itself is less. So, cyanosis cannot occur in anemia.

Carbon Monoxide Poisoning

Carbon Monoxide Poisoning Introduction: Carbon monoxide is a dangerous gas since it causes death. This gas was used by Greeks and Romans for the execution of criminals. Carbon monoxide causes more deaths than any other gases.

Sources Of Carbon Monoxide: The most common sources of carbon monoxide are exhaust from gasoline engines, coal mines, gases from guns, deep wells, and underground drainage systems.

Toxic Effects Of Carbon Monoxide:

• Carbon monoxide is a dangerous gas because it displaces oxygen from hemoglobin by binding with the same site in hemoglobin for oxygen.
• So, oxygen transport and oxygen carrying capacity of the blood are decreased.
• Hemoglobin has got 200 times more affinity for carbon monoxide than for oxygen.
• So, even with a low partial pressure of 0.4 mm Hg of carbon monoxide in alveoli, 50% of hemoglobin is saturated with it.
• It can be dangerous if the partial pressure increases to 0.6.mm, Hg, (1/1000 of volume concentration in air).
• The presence of carboxyhemoglobin decreases the release of oxygen from hemoglobin and the oxygen hemoglobin dissociation curve shifts to the left.
• It is still more dangerous because, during carbon monoxide poisoning, the partial pressure of oxygen in the blood may be normal in spite of the low oxygen content of the blood.
• So the regular feedback stimulation of respiratory centers by hypoxia does not take place because of normal partial pressure of oxygen.
• However, low oxygen content in blood affects the brain resulting in unconsciousness.
• The condition becomes fatal if immediate treatment is not given.
• Carbon monoxide is toxic to the cytochrome system in cells also.

Symptoms Of Carbon Monoxide Poisoning:

The symptoms of carbon monoxide poisoning depend upon the concentration of this gas:

1. While breathing air with 1% of carbon monoxide, saturation of hemoglobin with carbon monoxide becomes 15-20%.  Mild symptoms like headache and nausea appear
2. While breathing air containing carbon monoxide above 1%, the saturation becomes 30-40%.
3. It causes convulsions, cardiorespiratory arrest, loss of consciousness, and coma.
4. When hemoglobin saturation is above 50%, death occurs.

Treatment For Carbon Monoxide Poisoning:

The following procedure is adopted for the treatment of carbon monoxide poisoning.

• Immediate termination of exposure to carbon monoxide
• Providing adequate ventilation and artificial respiration
• Administration of 100% oxygen if possible. It is to replace carbon monoxide
• Administration of air with a few percent of carbon dioxide, if possible . It is done to stimulate the respiratory centers.

Atelectasis

Atelectasis Definition:

Atelectasis refers to a partial or complete collapse of lungs. When a large portion of lung is collapsed, the partial pressure of oxygen is reduced in the blood leading to respiratory disturbances.

Atelectasis Causes:

1. Deficiency or inactivation of surfactant. It causes the collapse of the lungs due to increased surface tension, which leads to respiratory distress syndrome
2. Obstruction of a bronchus or a bronchiole. In this condition, the alveoli attached to the bronchus or bronchiole are collapsed
3. Presence of air (pneumothorax), fluid (hydrothorax), blood (hemothorax) or pus (pyothorax) in the pleural space.

Atelectasis Effects: The effects of atelectasis are decreased partial pressure of oxygen leading to dyspnea.

Pneumothorax

Pneumothorax Definition:

Pneumothorax is the presence of air in pleural space.  The intrapleural pressure, which is always negative, becomes positive in pneumothorax and it causes the collapse of the lungs.

Pneumothorax Causes:

• Air enters the pleural cavity.
• Because of damage to the chest wall or lungs during accidents, bullet injury, or stab injury.

Pneumothorax Types And Effects: Pneumothorax is of three types:

1. Open pneumothorax
2. Closed pneumothorax
3. Tension pneumothorax.

Pneumothorax Open:

• After the injury, open communication is developed between the pleural cavity and the exterior. It is known as open pneumothorax.
• The air enters the pleural cavity during inspiration and comes out during expiration.
• The collapse of the lungs causes hypoxia, hypercapnia, dyspnea, cyanosis, and asphyxia.

Pneumothorax Closed :

• During a mild injury, air enters into the pleural cavity and then the hole in the pleura is sealed and closed.
• It is called the closed pneumothorax. It does not produce hypoxia.
• The air from the pleural cavity is absorbed slowly.

Tension Pneumothorax:

• During injuries, sometimes the tissues over the hole in the chest wall or the lungs behave like a fluttering valve.
• It permits the entrance of air into the pleural cavity during inspiration but prevents the exit of air during expiration due to its valvular nature.
• Because of this, the intrapleural pressure increases above atmospheric pressure.
• This condition is very fatal since it results in the collapse of the whole lung.

Pneumonia

Pneumonia Definition:

Pneumonia is the inflammation of lung tissues followed by the accumulation of blood cells, fibrin, and exudates in the alveoli. The affected part of the lungs becomes consolidated.

Pneumonia  Causes:

The inflammation of the lung is caused by:

1. Bacterial or viral infection
2. inhaling noxious chemical substances.

Pneumonia   Types:

• Pneumonia is of two types namely, lobar pneumonia and lobular pneumonia.
• When it is lobular and associated with inflammation of the bronchi, it is known as broncho-pneumonia.

Pneumonia  Effects:

Following are the effects of pneumonia:

1. Fever
2. Compression of chest and chest pain
3. Shallow breathing
4. Cyanosis
5. Sleeplessness (insomnia)
6. Delirium.

Delirium:

Delirium is an extreme mental condition that is caused by cerebral hypoxia.

The features of delirium are:

1. Confused mental state – confused way of thought and speech
2. Illusion – misinterpretation of a sensory stimulus
3. Hallucination – the feeling of a sensation such as touch, pain, taste, smell, etc. without any stimulus
4. Disorientation – loss of ability to recognize place, time, and other persons
5. Hyperexcitability
6. Loss of memory.

Bronchial Asthma

Bronchial Asthma Definition:

• Bronchial asthma is a respiratory disease characterized by difficulty breathing with wheezing.
• Wheezing refers to a whistling type of respiration.
• It is due to bronchiolar constriction caused by spastic contraction of smooth muscles in bronchioles leading to obstruction of air passage.
• The obstruction is further exaggerated by the edema of the mucous membrane and accumulation of mucus in the lumen of bronchioles.

Bronchial Asthma Causes:

• Inflammation of air passage: The leucine released from eosinophils and mast cells during inflammation cause bronchospasm
• Hypersensitivity of afferent glossopharyngeal »and vagal ending in the larynx and afferent trigeminal endings in the nose:
• Hypersensitivity of these nerve endings is produced by some allergic substances like foreign proteins
• Pulmonary edema and congestion of lungs caused by left ventricular failure: The asthma developed due to this condition is called cardiac asthma.

Bronchial Asthma  Features:

• Asthma is a paroxysmal (sudden) disorder because the attack commences and ends abruptly.
• During the attack, the difficulty is felt both during inspiration and expiration.
• Bronchioles have an inherent tendency to dilate during inspiration and constrict during expiration.
• So, more difficulty is experienced during expiration.
• During expiration, great effort is exerted by all the expiratory muscles causing compression of the chest.
• There is severe contraction of abdominal muscles also.
• So, air from the lungs is pushed through the constricted bronchioles producing a whistling sound.
• Because of difficulty during expiration, the lungs are not deflated completely so that, the residual volume and functional residual capacity are increased.

There is reduction in:

1. Tidal volume
2. Vital capacity
3. FEV,
4. Alveolar ventilation
5. The partial pressure of oxygen in the blood.
6. Carbon dioxide accumulates resulting in acidosis, dyspnea, and cyanosis.

Pulmonary Edema

Pulmonary Edema Definition: Pulmonary edema is the accumulation of serous fluid in the alveoli and the interstitial tissue of lungs.

Pulmonary Edema Causes:

1. Increased pulmonary capillary pressure due to left ventricular failure or mitral valve disease
2. Pneumonia
3. Breathing harmful chemicals like chlorine or sulfur dioxide.

Pulmonary Edema Effects:

• The effects of pulmonary edema are severe dyspnea, cough with frothy bloodstained expectoration, cyanosis cold extremities.
• Chronic interstitial edema leads to asthma. Alveolar edema is fatal and causes sudden death due to suffocation.

Pleural Effusion

Pleural Effusion Definition: Pleural effusion is the accumulation of a large amount of fluid in the pleural cavity.

Pleural Effusion Causes:

1. Blockage of lymphatic drainage
2. Excessive transudation of fluid from pulmonary capillaries due to increased pulmonary capillary pressure caused by left ventricular failure
3. Inflammation of the pleural membrane which damages the capillary membrane allows leakage of fluid and plasma proteins into the pleural cavity.

Pleural Effusion Features: Pleural effusion causes atelectasis leading to dyspnea and other respiratory disturbances.

Pulmonary Tuberculosis

Pulmonary Tuberculosis Definition:

• Tuberculosis is the disease caused by tubercle bacilli. This disease can affect any organ in the body. However, the lungs are affected more commonly.
• The infected tissue is invaded by macrophages and later it becomes fibrous. The affected tissue is called a tubercle.

Pulmonary Tuberculosis Features:

• Initially, the alveoli in the affected part become non-functioning due to the thickness of the respiratory membrane.
• If a large part of the lungs is involved, the diffusing capacity is very much reduced. In severe conditions, the destruction of the lung tissue is followed by the formation of large abscess cavities.

Emphysema

Emphysema Definition And Causes:

• Emphysema is one of the obstructive respiratory diseases in which the lung tissues are extensively damaged.
• The damage to lung tissues results in the loss of alveolar walls.
• Because of this, the elastic recoil of the lungs is also lost.

Emphysema is caused by any of the following factors:

1. Cigarette smoking
2. Exposure to oxidant gases
3. Untreated bronchitis.

Development Of Emphysema:

1. Smoke or oxidant gases irritate the bronchi and bronchioles leading to chronic infection
2. It increases the mucus secretion from the respiratory epithelial cells causing obstruction of air passage
3. The cilia of the respiratory epithelial cells are partially paralyzed and the movement is very much reduced.
4. Because of this, the mucus cannot be removed from the respiratory passage
5. The destruction of the alveolar mucous membrane
6. Destruction of elastic tissues occurs. Normally, there is a loss of some elastic tissues because of the proteolytic enzyme called elastase.
7. But, that is very much negligible. Moreover, the liver produces elastase inhibitors especially antitrypsin which prevent the destruction of elastic tissues.
8. But, due to heavy smoking or because of constant exposure to oxidant gases, the pulmonary alveolar macrophages increase in number.
9. The macrophages release a chemical substance, which attracts a large number of leukocytes.
10. The leukocytes release proteases including elastase, which destroy the lung elastic tissues.

Effects Of Emphysema:

1. The airway resistance increases several times due to the bronchiolar obstruction.
2. So, the movement of air through the respiratory passage becomes very difficult. It is more pronounced during expiration
3. Due to the destruction of the alveolar membrane and elastic tissues, the lungs become loose and floppy.
4. So. the diffusing capacity reduces to a great extent. However, lung compliance increases.
5. And the aeration of blood is impaired. Enough oxygen cannot diffuse into the blood and carbon dioxide cannot diffuse out
6. The obstruction also affects the ventilation-perfusion ratio resulting in poor aeration of the blood
7. Due to the destruction of lung tissues, the number of pulmonary capillaries also decreases.
8. It increases pulmonary vascular resistance leading to pulmonary hypertension
9. Over the years, chronic emphysema could lead to hypoxia and hypercapnia.
10. It will finally cause prolonged and severe air hunger (dyspnea) leading to death.