Key Role of Cardiopulmonary System - Essay Example

Cardiopulmonary In-Course Assessment 1. Discuss the effect of ascent to high altitude on ventilation and its control Respiration plays a key role in the well being of human beings. All the cells of the body require oxygen and it is through the process of respiration that oxygen is provided to all these cells. Similarly through the process of respiration carbon dioxide is also excreted to maintain normal body functions. Different mechanisms are taking place in our body which help us to survive in the conditions we are living in. Respiration is mostly associated with the partial pressures of the gases which are needed in the body. However these partial pressures of gases change as per the surroundings of an individual. As an individual ascends to higher areas than the sea level a measured change of the partial pressures of carbon dioxide and oxygen has been noticed. These changes in partial pressures cause the body to react differently to the ascent of an individual. When a person ascends his body tries to overcome the problems of low partial pressure by introducing a phenomena of acclimatization (1-2). As the partial pressure of oxygen is low at altitudes the person is not able to absorb enough oxygen so that his cells are oxygenated. The very first mechanism which gets activated in response to high altitudes is increased pulmonary ventilation. Increased pulmonary ventilation allows the mountain climbers to breathe rapidly and take excess oxygen which is required in the body. It also helps to excrete carbon dioxide which is a poisonous gas and would decrease the pH if it is not ventilated. As a person ascends from the sea level he is exposed to low PO2 and this stimulates specific chemical receptors in the arteries. These are known as chemoreceptors which detect any change in the chemical composition of the blood and gases. These chemoreceptors stimulate the respiratory centre and because of this the person ventilates more than the normal. Similarly, if a person stays at high altitudes for a longer time these chemoreceptors can increase normal pulmonary ventilation by almost 500%. It has also been reported that this increased pulmonary ventilation is due to the imbalance of ions in the cerebrospinal fluid. As CO2 is excreted from the body, the pH of the body decreases to such levels that the bicarbonate ions even decrease in the cerebrospinal fluid. These changes activate the chemosensitive neurons found in the respiratory centre and they further increase the pulmonary ventilation (2, 3, 4) 2. Discuss the blood gas data obtained and the difference between the two sets of data   Altitude is known to have a considerable effect on the partial pressures of gases in the atmosphere, blood and alveoli. It is seen from the case that as PF ascended 5,300 m above sea level, he started having disturbances because of his low acclimitization. The very first blood sample which was taken by the doctor showed that PF had a considerable low partial pressure of oxygen and carbon dioxide. The pH of the blood shows a rise from its normal value because of hyperventilation which is a part of acclimitization. Because of hyperventilation PF excreted a lot of CO2 and the blood has become alkaline (2, 4).   The next day the doctor takes another sample of PF which shows difference of the chemical composition of gases in his blood. The partial pressure of oxygen has lowered even more and the partial pressure of carbon dioxide has also lowered. Along with this the pH of the blood has farther increased because of excess hyperventilation (2, 4). Both the sets of data taken from the blood were taken at different times and in the latter times it was known that PF was suffering from some kind of edema because of low pressures of the gases. When the sample was taken on the first day it was seen that carbon dioxide was quite low in the body because of which the pH increased. Similarly in the other sample it was seen that the partial pressure of carbon dioxide further decreased which gave way to the further increase in pH. Similarly because of some edema in PF the partial pressure of oxygen has further lowered in the blood. This is the very reason that the doctor recommends him an immediate treatment (2, 4). 3. Describe the anatomy of the blood supply to the lungs Every organ in our body needs energy which is obtained from blood. The blood is supplied to every part of our body by the heart. The heart is the main component of our circulatory system. Our heart receives oxygenated blood from the lungs and pumps the oxygenated blood to periphery. The blood vessels which carry oxygenated blood from heart to the peripheral body parts are called arteries. Only one type of the arteries carry deoxygenated blood known as pulmonary arteries. The pulmonary arteries carry deoxygenated blood from heart to the lungs for oxygenation. The veins are the blood vessels which carry deoxygenated blood from the body parts to the heart except pulmonary veins which carry oxygenated blood from lungs to heart to be supplied to the body parts (10, 11). Like every organ lungs need blood supply too. But here the blood supply is not only required for the nutrition of the lungs but also for oxygen supply to the whole body. Each lung has two channels of blood supply: one for nutrition and the other for the oxygenation of the blood. The bronchial vessels are for the nutrition of lungs and pulmonary vessels for the oxygenation of blood (11). The bronchial arteries supply oxygenated blood for nutrition of the lung’s structures including root of the lungs, the supporting tissue of the lungs and the visceral pleura. Right lung is supplied by one bronchial artery. The left lung is supplied by two bronchial arteries. The bronchial artery supplying the right lung may arise either from the third posterior intercostal artery or from the upper left bronchial artery. The two bronchial arteries which supply the left lung are branches of the descending thoracic aorta (10, 11, 12). The bronchial arteries give branches to the upper part of esophagus and pass posterior to main bronchi to give branches up till the respiratory bronchioles. The distal most branches anastomose with branches of pulmonary arteries in the walls of bronchioles. The bronchial veins drain that part of the lung which is supplied by the bronchial artery. The bronchial vein draining the right lung itself drains into azygos vein and left bronchial vein. The bronchial vein draining the left lung drains into accessory hemiazygos vein (10, 11, 12). Each lung has a pulmonary artery which supplies blood too but for the oxygenation of the deoxygenated blood. The pulmonary arteries supplying both right and left lungs arise from pulmonary trunk. Each pulmonary artery after entering the root of lung gives a branch to the superior lobe. Within the lung each artery descends posterior-lateral to the main bronchus and then divides into lobar branches and segmental branches. Thus each lobe and each bronchopulmonary segment is supplied by branch of pulmonary artery (10, 11, 12). Each lung has two pulmonary veins which carry oxygenated blood from lungs to the left atrium of the heart. In the pulmonary capillaries the veins unite into larger and larger vessels. The veins passing between bronchopulmonary segments in the septa separating the segments drain the contiguous bronchopulmonary segments. The pulmonary veins run independently from the arteries as they run in the bronchi till they cross the hilum. The veins draining the visceral pleura also drain in the pulmonary veins (10, 11, 12). 4. Discuss the likely mechanism of the pulmonary oedema in this patient Edema denotes a problem in the capillaries when they are unable to hold the fluid inside them. This leads to abnormal accumulation of the fluid outside the capillaries and hence the space in which the fluid accumulates swells. The causes of edema are mostly related to pressures of the capillaries and the fluid outside them. The permeability of the vessels also determines the rate of edema in an individual. This patient is probably suffering from High Altitude Mountain Edema. The pulmonary edema in this patient is possibly occurring from hypoxia in the patient. Because of hypoxia the patient would not be getting enough oxygen and the vessels would get constricted (2, 3). It is known that the arteries detect the change in the concentration of oxygen and constrict accordingly. The pulmonary arterioles in a similar fashion constrict because of lack of oxygen (5, 6, 7). In lungs some of the pulmonary arterioles get constricted even more whereas some of the pulmonary arterioles don’t get constricted at all. In such a case the blood passes from the constricted arteries into the unconstricted ones and causes a high pressure to be built up. Because of this the capillaries in the lungs develop a very high pressure. This high build up of pressure in the pulmonary capillaries leads to the development of Pulmonary Hypertension. This pulmonary hypertension can lead to a heart attack. This pulmonary hypertension causes the capillaries to force out the fluid inside them to the insterstitium. This is because the pressure at this point in the capillaries is higher than the surrounding interstitial fluid and other forces which help to keep the fluid inside the capillaries. This causes pulmonary edema to develop. This edema at first is localized to a specific area but it can spread further to other areas with the similar process. This process can be reversed if pure oxygen therapy is supplied to the individual. This is the possible disease that PF is having in this case and because of this the doctor has recommended him to go down immediately so that oxygen can be revived to the exact levels in the body (1, 2). 5. Compare and contrast the actions of nifedipine and sildenafil (an alternative option to nifedipine) Nifedipine belongs to dihydropyridine which is essentially a calcium channel antagonist. Calcium Channel antagonists act on the calcium channels to stop the inward flow of calcium. It acts as an allosteric inhibitor to compete with the machinery of the cell through which it stops the flow of calcium. It also is use dependence i.e. it works more on the cells whose calcium channels are more active. The group Nifedipine is basically used on smooth muscles. It helps to cause arteriolar dilation and mostly affects only the arteries and not the veins. This vasodilatation causes the arterial pressure to decrease and hence decrease the pressure developed inside by the fluid. This is used in pulmonary hypertension to decrease the capillary pressure because of which the edema is being caused. Because of the decrease in arterial pressure edema would be avoided (8). On the other hand Sildenafil is a group which is basically used for the purpose of penis erection. Like Sildenafil also has a huge effect on the smooth muscles and can cause vasodilation of the arteries. The mechanism by which it acts is however different than that of Nifedipine. Although both nifedipine and sildenafil act on smooth muscles but they both are used for different purposes. Nifedipine is used in Angina and pulmonary hypertension whereas sildenafil is used in penis erection. cGMP is a nucleotide which helps in several functions inside the body. This cGMP in the body is degraded by an enzyme in the body because of which it is not able to fulfil its function at times. Sildenafil acts for the protection of cGMP from the enzyme known as cGMP specific phosphodiesterase type 5. As cGMP is increases it has the effect of dilating a smooth muscle. Because of this dilatation the arteries can also dilate. In other words sildenafil acts as a cGMP phosphodiesterase type 5 inhibitor whereas nifedipine acts a calcium channel inhibitor. In practical use of penis erection sildenafil helps cGMP to accumulate and cause arteriolar dilatation in the penis and thus help to make it erect (7, 8). In my view Nifedipine is a better drug to be used than Sildenafil because the effect of Sildenafil is best used in penis erections only. Nifedipine helps to relieve pulmonary hypertension and in this case can prove to be useful than any other drug. If PF is further exposed to pure oxygen his pulmonary edema can be cured (7, 8). References 1. 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