Effect of cigarette smoking on lung function – history gas and supply

The effect of cigarette smoking on lung function was studied in fifty males and females including twenty five smokers who served as test group and twenty five smokers who served as test. Group and twenty five non-smokers that served as control group. The results obtained in this study showed and decrease in lung function with increasing age. This is in conformity with the findings of Beck et al in 1974. There was a correlation between mean FEVI, mean FEVI/VC%, and mean PEFR and smoking and there was a decrease in all of these parameters after cigarette smoking. A decrease in any of these parameters indications loss of lung function.

The lung is the organ of external respiration whereby oxygen and carbon dioxide are exchanged between the body and the surrounding air. It is an elastic structure and this structure enables it to perform its function of respiration. The lung, as an elastic structure, expand in response to respiratory movements. The expansibility of the lungs and thorax is called compliance. Compliance is a static measure of lung and chest recoil.

Gaseous exchange is the cardinal function of the lungs and the exchange of gases occurs in the terminal portions of the lungs. The portion of the lungs where there is no gaseous exchange is called anatomical dead space. The lung is the seat of pulmonary circulation. Pulmonary circulation is the circulation of blood between the lungs and the heart. Pulmonary blood flwo at rest averages 5.5 litres per minute. The entire pulmonary vascular system is a distensible low-pressure system. The lung also filter out small blood clots with the aid of the pulmonary circulation. The lung has defence mechanisms that help resist infections and maintain the integrity of the bronchial mucosa. Some of its components are actively phagocytic and ingest inhaled foreign materials and other operates to prevent foreign materials and others operate to prevent foreign matter from reaching the alveoli. The lung has anabolic and catabolic functions and it contain APUD cells which contain biologically active peptides. These include substance P, bombesin, vasoactive intestinal peptide, and opiod peptides. 1.2 LUNG VOLUMES: Lung volumes are recorded when somebody is breathing in and out during respiration. The volume of air inspired or expired with each breath is called the tidal volume. The average tidal volume amounts to about 500 ml. the air inspired with a maximal inspiratory effort in excess of the tidal volume is the inspiratory reserve volume. The amount of air that can be expired by forceful expiration after the end of a normal tidal expiration is called the expiratory reserve volume. The volume of air left in the lung after a maximal expiratory effort is the residual volume.

The maximum amount of air that a person can expel from the lungs after a maximal inspiratory effort is called the vital capacity. The vital capacity is frequently measured clinically as an index of pulmonary function. It averages 4.6 litres in young adult males and 3.1 litres in young adult females. These values are much greater in some persons of the same weight than in others. A tall, thin person usually has a higher vital capacity than an obese person, and a well-developed athlete may have a vital capacity as great as 30 to 40 percent above normal. Paralysis of the respiratory muscles can cause a great decrease in vital capacity. Diminished pulmonary compliance also cause a decrease in vital capacity. The fraction of the vital capacity expired in one second is called the forced expiratory volume in one second and this also gives additional valuable information about the state of the lung. The vital capacity may not change in volume but the forced expiratory volume in one second will reduce ion a situation is where there is an increased airway resistance owing to bronchial constriction. In the normal person, the percentage of the vital capacity that is expired in the first second is about 80. However, in an airway obstruction, this value will decrease to about 47 percent. In serious airway obstruction, as often occurs in acute skhma, this can sometimes decrease to less than 20 percent. The peak expiratory flow rate is the maximum flow ate attainable at any time during a FEV. It is recorded in litres per second or litres per minute. It may exceed 600 1 per minute (10L/sec) in healthy young men; thee range is 400