Pulmonary ventilation, spirometry and pulmonary physiology - Lab Report Example

? Pulmonary ventilation, spirometry and pulmonary physiology BY 409L-Biopac Lab: L12 Pulmonary Function Lab Partner: Angela Ray Abstract Pulmonary ventilation is measured and recorded by a Spirometer, which is an important tool for Pulmonary Function Test. The experiment conducted using 409L-Biopac Student Lab: L12 and a spirometer aimed at recording and analyzing the spirometry values of a subject. The experimental values with respect to tidal volume, vital capacity, inspiratory capacity, inspiratory reserve volume, expiratory reserve volume and the total lung capacity were similar to the personal predicted values. Residual volume and Functional Residual Capacity were much higher as compared to the predicted values. The breathing rate was high and the FEV1/FVC values were low indicating obstructive disease of my subject. Introduction 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 diaphragm 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 bodies respectively are stimulated. This causes the stimulation of the rostral ventrolateral medulla which further stimulates the respiratory pacemaker the pre-bottzinger complex. This leads to stimulation of phrenic nerves causing contraction of the diaphragm. In the medulla the dorsal and ventral respiratory group of neurons is also stimulated causing contraction of external and internal intercostals leading to inspiration. The depth and rate of breathing is controlled by Pneumotaxic centre situated in the pons which inhibits excess inhalation, and expiration occurs passively. (George,2005) (Miller, 2005) The movement of air in and out of the lungs is measured and recorded through an instrument called Spirometer. This instrument helps to evaluate the various pulmonary volumes and capacities of a person indicating the status of his respiratory system. Spirometry is an important tool for Pulmonary Function Test, which provides a complete evaluation to diagnose whether the person is suffering from any pulmonary impairment. Spirometry is also a part of the bronchial challenge test, which is used to determine the hyper-responsiveness to strenuous exercise, inhalation of air of extreme thermal conditions and on exposure to drugs like histamine. The spirometer recording is displayed on graphs called the spirograms. These include a) volume-time curves which plots pulmonary volumes (in litres) along the Y axis and time (in seconds) along the X axis and b) flow-volume loop which depicts the rate of airflow on the Y axis and the total volume inspired and expired on the X axis. The values extrapolated from these spirograms are used for prognostic and diagnostic purposes. Normally a person is asked to take the deepest breathe through the mouthpiece and then exhale as hard as possible into the sensor of the spirometer. During the test soft nose clips are used to prevent escape of air through the noses and the mouthpieces are provided with filters to prevent spread of microorganisms. (George, 2005) (Miller, 2005) a. b. c. Fig 1 a: A Modern Desktop Spirometer with digital turbine and antibacterial filter. b: Spirogram depicting lung volumes c: Flow-Volume loops and other parameters as calculated by software. The major pulmonary volumes and capacities measured by the spirometer and its diagnostic significance are described as follows: a) Tidal Volume (TV) is the amount of air that flows in and out during quiet breathing, b) Residual Volume(RV) is the volume of air remaining in lungs after a maximal expiration, this volume specifies the amount of air that must be present in alveoli to held them open and prevent lungs from collapsing, c) Expiratory Reserve Volume(ERV) is the maximal volume of air that can be exhaled above the tidal volume air, d) Inspiratory Reserve Volume (IRV) is the maximal volume of air that can be inhaled above the tidal volume air. Lung capacities are a combination of various volumes: a) Inspiratory Capacity= IRV+TV, b) Expiratory Capacity=ERV+TV, c) Vital Capacity (VC) is the amount of air breathed out after deepest inhalation, VC=IRV+TV+ERV, d) Functional Residual Capacity(FRV) is the volume of air in the lungs t the end of quiet expiration. FRC is not measured by spirometer. In old age the FRC is nearly equal to Closing Capacity while in young persons FRC is far greater than Closing Capacity. The significance is that if elder persons make voluntary excessive efforts in breathing the air that must remain in the lungs to held it open will be exhaled and the lungs will collapse. (George, 2005) (Miller, 2005) The other measurements that are of value are FEV1/FVC ratio, FEFx, and MVV. FEV1 (Forced Expiratory Volume in first second) is the volume of air breathed out of the lungs forcefully in the first second after a forceful inspiration. FVC (Forced Vital Capacity) is the maximum amount of air that can be breathed out over a span of time. This ratio specifies whether a person is suffering from obstructive or restrictive disease. The ratio for a normal person is around 80%. For an individual suffering from obstructive lung disease, filling the lungs may be easy as compared to emptying them. This has an effect in that an additional amount of air remains trapped into the lungs after exhalation thus Functional Residual Capacity and Residual Volume are increased but the total lung capacity remains normal. Since airflow is decreased by obstruction, the volume of Forced Expository Volume after one second is also reduced but it’s decreased. The effect of this is that the ratio of FEV1/VC is less than the normal value of 80%. Thus obstructive disease means there is obstruction in airways causing a difficulty in exhalation and obviously the volume of air exhaled in the first second will decrease and the ratio will fall. If the ratio falls to around 40-60% it specifies obstructive diseases like asthma, emphysema, rhinitis or chronic obstructive pulmonary disease. (Ciprandi, 2011) On the other hand in restrictive diseases like Tuberculosis there is difficulty in inhalation as the lung tissues are damaged and the total lung capacity will fall. The point is less the air is taken in more easily it comes out and the ratio approaches 90% or above. This happens as the lungs cannot be expanded normally and therefore the vital capacity, inspiratory capacity and total lung capacity are all reduced. This makes the percentage of air to be expired in one second to much greater that the normal 80%. The explanation is as less air is taken in so there is no difficulty in exhaling out that in the first second. When the ratio approaches 90-95% it is wise to evaluate the total lung capacity. (George, 2005) (Miller, 2005) MVV means maximal voluntary ventilation which is the volume of air exhaled after repetitive voluntary exhalations and marks the efficiency of ventilation mechanics. FEF are flow rates and signifies the flow of air in and out of the lungs during different phases of breathing. (George, 2005) (Miller, 2005) Furthermore, the pulmonary ventilation is affected by the type of activity an individual engages himself like for the occasional athletes the rate of pulmonary ventilation is very high as compared to the individual who does not involve himself in any athletic activity. (George, 2005) (Miller, 2005) Finally, individual with health problems like asthma, bronchitis and COPD the breathing rate is greatly affected in the negative direction. The ability of the lungs to diaphragm to contract and relax is reduced since its elasticity and compliance are reduced and hence air exchange is also greatly affected. (George, 2005) (Miller, 2005) Material and Methods Using the spirometer and 409L-Biopac Student Lab the pulmonary function of my subject was assessed by standard procedures. (Minako, 2007) Results Table 1: Results recorded as per instruction 16 of the manual and from figure 3 and 4 in my manual (Minako, 2007) Measurements Values 16a 2.43592L 16b 2.02655L 16c 8.06 sec 16d 3.37288L 16e 2.31929L 16f 1.35486L The tidal volume in this context can be obtained by taking the difference between the values of 16a and 16b. These values were taken for a minimum number of five normal breaths. The value of Delta T is given as 8.06sec for 5 breaths. The total of 16d and 16 f signifies the Forced vital capacity.16e indicates the FEV1. Table 2: Volume and capacities for measuredvalues from figure 5 of the manual (Minako, 2007) Spirometry value Value FVC or VC 4.72 Liters FEV1 2.31 Liters FEV1/FVC 48.9% TLC 6.29 Liters TV 0.409 Liters IRV 2.97 Liters ERV 0.95 Liters IC 3.37 Liters RV 1.97 Liters FRC 2.92 Liters Breathing rate 37 Breaths/min MVR 14.8 L/min AV 4.44 L/min Predicted values as calculated using appropriate formula from manual Males: 0.052(height in cm)-0.022(age in years)-3.6 VCN=0.052(157)-0.022(22yrs)-3.6= 4.168 litres Table 3: Predicted values (Normal values) from figure 6 of the manual (Minako, 2007) Predicted value Male TLCN=VCN/0.75 5.557 VCN (valve from the equation) 4.168 TVN=VCN/10 0.4168 IRN=VCNx0.65 2.709 ERVN=VCNx0.25 1.042 ICN=TVN+IRVN 3.126 RVN=VCN/3 1.389 FRCN=ERVN+RVN 2.431 Normal or predicted values are usually calculated based on the values of age, height and sex of an individual. (Minako,2007) These values are very critical as they are used as a point of reference which was used to compare the measured values with the normal ones. If these values give a very large deviation, then the implication is that, there may be pulmonary problems or rather the experiment was done incorrectly. From the tables 5 and 6 above, we can evaluate the experimental findings, in comparison to the personal predicted values of the lung function parameters. The values with respect to tidal volume, vital capacity, inspiratory capacity, inspiratory reserve volume, expiratory reserve volume and the total lung capacity were more or less similar. The values deviated when considering the residual volume, functional residual capacity were much higher as compared to the predicted values. The breathing rate and frequency of breathing was also quite high and the FEV1/FVC values were also low while compared to literature search. This indicates that the subject is suffering from obstructive diseases because it is only under these conditions the ratio falls to 50% versus the normal value of 80%. This is supported by the fact that due to obstruction in the airways the air inside the alveoli cannot come out easily thus increasing the residual volume and FRC. As this phenomenon occurs the pCO2 levels rises and must have stimulated the respiratory chemoreceptors to fire, and increase the breathing frequency or hyperventilate to wash out the accumulated pCO2. This causes respiratory distress, as in diseases like asthma or COPD. This might be the reason for the breathing rate to be as high as 37/minute, as against the normal values of 12-14/minute. Discussion and Conclusion The process and evaluation of pulmonary ventilation is thus important for the prognosis and diagnosis of respiratory disorders in human beings. The experiment was done to measure and apply the relevance of the spirometer values as a guide to screening of pulmonary disorders. Results were obtained from an individual with specific status, age, health and sex. It was noted that these factors play a very important role when it comes to ventilation. In male individual values of VCN are reported to be high as compared to the female of the same age and health status. This is because the thoracic cavity of males is larger than the females. (George, 2005) (Miller, 2005) Factors like the compliance and elasticity of the lungs also played an important role in this exercise. The ability of the lungs to stretch determined whether the inhalation and /or exhalation will be quiet or forced. If more muscular force is involved then a forced inhalation tends to take place. For quite breathing the inhalation and exhalation takes place normally with the contraction and relaxation of the diaphragm. If an individual is not healthy, then the lungs lose their elasticity or compliance ability and the rate of breathing is severely affected. (George, 2005) (Miller, 2005) In addition, age plays in that as an individual grows the body structure becomes more complex and therefore more force will be required in the process of inspiration and expiration. Men are considered to be more muscular as compared to women and hence can use increased muscular force involved in the process of breathing as ageing occurs. So when women turn elderly they are compromised to breathe due to this anatomical deficit. (George, 2005) (Miller, 2005) Normal or predicted values of lung volumes are usually calculated based on the values of age, height and sex of an individual as described. These values are very critical as they are used as a point of reference which was used to compare the measured values with the normal ones. Since certain values like RV, FRC, FEV1/FVC values deviated in our experiment we inferred certain pulmonary diseases like obstructive diseases might have been responsible. References Ciprandi, G; Cirillo, I (2011). "Forced expiratory flow between 25% and 75% of vital capacity may be a marker of bronchial impairment in allergic rhinitis". Journal of Allergy and Clinical Immunology 127 (2): 549–549. George, R. (2005). Chest medicine: essentials of pulmonary and critical care medicine Lippincott Williams & Wilkins. p. 96 Miller, MR; Crapo R, Hankinson J et al. ( 2005). General considerations for lung function testing" European Respiratory Journal 26 (1): 153–161 Minako, W. T. (2007). Mammalian Physiology BY 409L:Laboratory Manual, 2E. Eden Prairie, MN 55346: Bluedoor,LLC. Read More