Pulmonary ventilation, spirometry and pulmonary physiology Lab Report

Pulmonary ventilation, spirometry and pulmonary physiology - Lab Report Example Pulmonary ventilation is the exchange of air in and out of the lungs. The average human breathing rate is 30-60/minute at birth, while in adults it falls to 12-20/minute. Normally the amount of air that flows in and out of the lungs per breathe is 500ml (Tidal Volume air). Hence the minute ventilation or maximum respiratory volume is 6 litres considering breathing rate to be 12/minute. Pulmonary ventilation enables the flow oxygen to the lungs, which further helps in oxidative phosphorylation and at the same time causes removal of carbon dioxide from the lungs, helping to maintain the acid base balance in the body. Mechanism of pulmonary ventilation involves three scenarios: quiet inspiration, quiet expiration and forced inhalation or exhalation. During quiet inhalation the diaphragm contracts, the external intercostals muscles contracts, pulling the ribs outward and upward. This causes the volume of the thoracic cavity to increase with adjacent fall in the intrapulmonary pressure. ( George,2005)(Miller,2005) Hence, as the atmospheric pressure is more than the intrapulmonary pressure air flows into the lungs. During quite exhalation, diaphragm and the external intercostals relax and expiration occurs passively. This occurs as the lung volume now decreases causing rise in intrapulmonary pressure above the atmospheric pressure and air is exhaled out. Forced inhalation/exhalation occurs in certain diseased conditions and during exercise. During this condition the accessory inspiratory and expiratory muscles aid in the contraction process to take place faster in order to increase or decrease the intrapulmonary pressure.(George,2005)(Miller,2005) The act of pulmonary ventilation is limited by the elastic recoil of the lungs which is measured by lung compliance. By definition compliance refers to the increase in the pulmonary volume per cm H2O rise in transpulmonary pressure. The intrapleural pressure is held negative with respect to the intrapulmonary pressure by the mechanics as described above. Even after that the lungs may not expand as desired if he elasticity or in other words the compliance is decreased. (George, 2005) (Miller, 2005) Compliance might decrease or increase in various pulmonary diseases limiting pulmonary ventilation. Compliance is ensured by Surfactants which are phospholipids like lecithin that maintains the alveolar stability by reducing or increasing the surface tension in the alveoli. This means when the alveoli try to collapse due to forced expiration, the surface tension is increased but surfactants reduce the tension. On the other hand when alveoli try to expand during forced inspiration the effective surfactant concentration/area of the alveoli decreases and hence surface tension increases causing the alveoli to revert to original position. (George, 2005) (Miller, 2005) Pulmonary ventilation is controlled by neural and chemical pathways that acts as effectors ad sensors to influence the intercostals muscles and diap hragm mechanics as described earlier. Whenever there is increased pCO2 and decreased pO2 in the arterial blood the central and the peripheral chemoreceptors situated in the medulla oblongata and carotid/aortic