Respiratory system

Diagnosis and treatment of most respiratory disorders

Diagnosis and treatment of most respiratory disorders depend heavily on understanding the basic physiologic principles of respiration and gasexchange.

Study of Blood Gases and Blood pH

Blood Po2, CO2, and pH measurements is often important in determining appropriate therapy for acute respiratory distress or acute abnormalities of acid-base balance. This is called blood gas analysis .

Measurement of Maximum Expiratory Flow (MEF)

When a person expires with great force, the expiratory airflow reaches a maximum flow beyond which the flow cannot be increased any more even with greatly increased additional force. In asthma, the resistance to airflow becomes especially great during expiration


Two types of lung diseases: Constricted (restrictive) lungs and airway obstruction. - The constricted lungs have both reduced total lung capacity (TLC) and reduced residual volume (RV). Constricted lung diseases include fibrotic diseases of the lung itself, such as tuberculosis ,silicosis, and diseases that constrict the chest cage, kyphosis, scoliosis. - In diseases with airway obstruction, it is usually much more difficult to expire than to inspire ,disease that causes severe airway obstruction is asthma& emphysema.

Forced Vital Capacity (FVC) andForced Expiratory Volume (FEV)

In performing the FVC maneuver, the person first inspires maximally to the total lung capacity, then exhales into the spirometer with maximum expiratory effort as rapidly and as completely as possible. (FEV1) forced expiratory volume in the first second (FEV1/FVC%): the percentage of the FVC that is expired in the first second divided by the total FVC (FEV1/FVC%) normally is 80 %.


Hypoxia :decrease O2 concentration in the body fluid Effects of Hypoxia on the Body: Hypoxia caused by:* too little oxygen in the air,* too little hemoglobin, *or poisoning of the oxidative enzymes Hypoxia, if severe enough, can cause death of cells throughout the body, but in less severe degrees it causes principally (1) depressed mental activity, sometimes coma, and (2) reduced work capacity of the muscles.


Cyanosis: means blueness of the skin, caused by excessive amounts of deoxygenated hemoglobin in the skin blood vessels, especially in the capillaries. This deoxygenated hemoglobin has an intense dark blue-purple color that is transmitted through the skin.


Cyanosis appears whenever the arterial blood contains more than 5 g of deoxygenated hemoglobin in each 100 ml of blood. A person with anemia almost never becomes cyanotic because there is not enough hemoglobin . Conversely, in a person with excess red blood cells (polycythemia ), the great excess of available hemoglobin that can become deoxygenated leads frequently to cyanosis.


Hypercapnia: means excess CO2 in the body fluids. hypercapnia is not aconcomitant of hypoxia. Except when hypoxia is caused by hypoventilation or circulatory deficiency. When the alveolar PCO2 ↑↑ above 60 -75 mm Hg, the breathing become rapid and deep. If the PCO2 ↑↑ above 75 mm Hg, the person becomes lethargic and sometimes even semicomatose.


Dyspnea (air hunger) :Dyspnea means mental anguish associated with inability to ventilate enough to satisfy the demand for air. The dyspnea either Neurogenic dyspnea or emotional dyspnea. Anyone momentarily thinking about the act of breathing may suddenly start taking breaths a little more deeply than ordinarily because of a feeling of mild dyspnea. This feeling is greatly enhanced in people who have a psychological fear of not being able to receive a sufficient quantity of air, such as on entering small or crowded rooms.