Disorders of Respiratory system

(1) Respiratory quotient (R.Q.) : Respiratory quotient is the ratio of carbon dioxide output to oxygen usage during respiration. It is measured by Ganong’s respirometer.

$\text{R}\text{.Q}\text{.}=\frac{\text{Volume of }C{O}_2\text{ formed}}{\text{Volume of }{O}_2\text{ utilized}}$

The volume of RQ depends upon the type of fuel substance being utilized for energy production.

In an organism utilizing carbohydrates as source of energy anaerobically, the RQ is likely to be infinity. When carbohydrates are substrates for respiration, it is called 𠆏loating respiration’. Diabetic patient shows low R.Q. due to increased dissimilation of fats and the decreased dissimilation of carbohydrate.

(2) Effect of CO : Carbon monoxide is a poisnous gas. Hb has maximum affinity for CO. Carbon monoxide binds with haemoglobin at the same place where $O_2$ binds, but about 250 times more readily than $O_2$. Hence, it readily displaces $O_2$ from haemoglobin and even a 0.4 mm Hg partial pressure of CO in alveolar air is enough to occupy about half of the haemoglobin of pulmonary blood rendering it useless for O₂ transport. A CO pressure of about 0.7 mm Hg (concentration of about 1%) in alveolar air can be lethal. That is why, the atmosphere of industrial areas, being loaded with chimney smoke, is regarded harmful to health. It forms carboxyhaemoglobin with Hb which is most stable. Sudden deep inspiration is due to either increase in concentration of $C{O}_2$ or decrease in concentration of $O_2$. Forced deep breathing for a few minutes by a person sitting at rest may be followed by a temporary cessation of breathing. This is influenced by too much $O_2$ and least $C{O}_2$ in blood. Sudden deep inspiration is due to either increase in concentration of CO₂ or decrease in concentration of O₂.

(3) Regulation at high altitudes : At high altitudes, the composition of air remains almost the same as at sea-level, but the density (barometric pressure) of air gradually decreases. While ascending up a mountain, one inspires thin air, getting less oxygen. Less O₂ level in the blood results in hypoxia. The chemoreceptor simulatory mechanism progressively increases the rate of ventilation. Ventilation ordinarily does not increase significantly until one has ascended to about 2500 metres, because the $P_{C{O}_2}$ and pH remain almost normal.

(4) Disorders of Respiratory system

(i) Hypoxia : Hypoxia is a condition of oxygen shortage in the tissues. It is of two types :

(a) Artificial Hypoxia : It results from shortage of oxygen in the air as at high (over 2400 m.) altitudes. It causes mountain sickness characterised by breathlessness, headache, dizziness, nausea, vomiting, mental fatigue and bluish tinge on the skin and mucous membranes.

(b) Anaemic Hypoxia : It results from the reduced oxygen-carrying capacity of the blood due to anaemia (decreased haemoglobin content in blood) or carbon monoxide poisoning (some haemoglobin occupied by CO). in both cases, less haemoglobin is available for carrying $O_2$.

(ii) Asphyxia (Suffocation) : The $O_2$ content of blood falls and the $C{O}_2$ content rises and paralyses the respiratory centre. Breathing stops and death occurs.

(iii) Bad cold : Disease-causing microbes present in the air attack respiratory tract, producing inflammation of the mucous membrane and caused increased secretion :

(a) Rhinitis in the nasal chambers.

(b) Sinusitis in the sinuses.

(c) Pharyngitis in the pharynx, often called sore throat, and is usually accompanied by tonsillitis (enlargement of tonsils).

(d) Laryngitis in the larynx, causing hoarse voice and difficulty in speaking.

(e) Bronchitis in the bronchioles.

(iv) Emphysema : The air-pollutants that cause chronic bronchitis, may breakdown the alveoli of the lungs, reducing the surface area for gas exchange. The victim becomes permanently short of breath.

(v) Bronchial asthma : It is an allergic attack of breathlessness associated with bronchial obstruction or spasm of smooth muscle (contraction), characterized by coughing difficult breathing and wheezing patient has trouble exhaling.

(vi) Bronchitis : It is caused by the permanent swelling in bronchi. As a result of bronchitis cough is caused and thick mucus with pus cells is spitted out. Dyspnea fever develops. Dyspnea means hunger of air or deficiency of oxygen in the blood or development of hypercapnia i.e., increase of $C{O}_2$ concentration in blood. This disease is accelerated by fatigue, malnutrition, cold etc. the patient experiences difficulty in breathing. Here hypertrophy and hyperplasia of bronchi takes place.

(vii) Pneumonia : Oxygen has difficulty diffusing through the inflammed alveoli and the blood PO₂ may be drastically reduced. Blood PCO₂ usually remain normal because CO₂ diffuses through the alveoli more easily than O₂. In chronic patients of common cold and influenza, the lining epithelium of bronchi and lungs is inflammated. This disease is caused by streptococus pneumoniae, other bacteria, fungi, protozoans, viruses and the patient feels difficulty in breathing. Its prominent symptoms are trembling, pain in chest, fever, cough delirium etc. This disease is prevalent in either children or elderly persons in old age.

(viii) Lung cancer : It is believed that by excess smoking, lung cancer (carcinoma of lungs) is caused. The tissue increases limitlessly, which is called malignancy. This disease is fatal. The frequency of occurrence of this disease in smokers is 20% more. Malignancy of tissues (neoplasia) causes pressure on the cells of other tissues and destroys them. The blood capillaries are ruptured, blood starts flowing and death is caused by excessive bleeding.

(ix) Tuberculosis : This disease is also called T.B. and was considered fatal, but these days its full cure is possible. Thus, disease is called curable, these days. It is caused by bacteria Mycobacterium tuberculosis. These bacteria settle in lungs at different places and convert normal tissue into fibrous tissue. Since the respiratory surface is decreased, the difficulty in breathing is also experienced. If the patients start taking medical advice and the medicines right from the initial stage regularly, the patients can be fully cured of the disease. Now a days a new therapy DOT (Direct observed treatment) is used for tuberculosis treatment, recently launched by Indian Government. Many other drugs like rifampin and isoniazid are successful for the treatment of tuberculosis. Tuberculosis bacteria are spread by inhalation and exhalation.

(x) Coryza : Common cold, due to rhinoviruses in adult.

(xi) Influenza : Flu.

(5) Occupational lung disease : It is caused because of the exposure of potentially harmful substances. Such as gas, fumes or dusts, present in the environment where a person works. Silicosis and asbestosis are the common examples, which occur due to chronic exposure of silica and asbestos dust in the mining industry. It is characterised by fibrosis (proliferation of fibrous connective tissue) of upper part of lung, causing inflammation.

(i) Prevention and cure : Almost all the occupational lung diseases, express symptoms after chronic exposure, i.e., 10-15 years or even more. Not only this, diseases like silicosis and asbestosis are incurable. Hence, the person likely to be exposed to such irritants should adopt all possible preventive measures. These measures include :

(a) Minimizing the exposure of harmful dust at the work place.

(b) Workers should be well informed about the harm of the exposure to such dusts.

(c) Use of protective gears and clothing by the workers at the work place.

(d) Regular health check up.

(e) Holiday from duty at short intervals for the workers in such areas.

(f) The patient may be provided with symptomatic treatment, like bronchodilators and antibiotics, to remove underlying secondary infection.

(6) Special respiratory movements

Cough

(1) It is reflex action stimulation takes place from trachea and lungs.

(2) Centre is medulla oblongata.

(3) Cough is a forcible expiration usually produced after a prolonged inspiration.

(4) When some food particle enters the windpipe instead of oesophagus, it is expelled by a process of coughing.

(5) Air exploded through the mouth.

Sneezing

(1) Reflex action stimulated by olfactory epithelium of nasal chamber.

(2) Sneezing is a forcible expiration, air explodes out through nose and mouth.

Hiccuping

(1) Hiccuping is a noisy inspiration caused by muscular spasm of diaphragm at irregular intervals.

(2) Noise is due to sudden sucking of air through vocal cords.

(3) Stimulation of hiccuping is usually irritation of the sensory nerve endings of the digestive tract.

Yawning : Yawning is a prolonged inspiration. Low oxygen tension in the blood causes yawning.