Respiratory SystemRespiratory system provides the exchange of gases between blood and the atmospheric air, which is important for the functioning of all cells inside the body. The system can be divided into two parts which consist of the upper and the lower respiratory tract. The upper tract includes nostrils, nasal cavity, pharynx, and larynx which are responsible for trapping the dust in the air and its conduction into the lower respiratory tract. Besides, there are number of reflexes protecting the other part of the system as well as organism within the upper respiratory tract. They include sniffing and sneezing to remove foreign particles from the nasal cavity, aspiration reflex of pharynx and expiration reflex of larynx to prevent large objects from entering and blocking the trachea (Widdicombe, 2011). Therefore, the major reflexes of the upper respiratory tract meet the function of this part of the system to conduct air and to prevent blockage in lower tract.The lower respiratory tract consists of trachea, bronchi, and lungs. The trachea is a C-shaped tube formed by cartilage rings connecting to the esophagus to allows for the passage of food along it. The lining of trachea is represented by ciliated epithelial cells and goblet cells that produces mucus. The continuous beating of cilia allows efficient removal of foreign particles trapped by the mucus (Hall & Guyton, 2016). The importance of this mechanism is underlined by pathological condition known as ‘cystic fibrosis’. This is caused when there is abnormality in chlorine channels within the tracheal lining which prevents water from moving in by osmosis.. As a result, the trapped particles cannot be effectively removed by the beating of cilia because of the sticky mucus, and rather move into the bronchi and lungs, leading to increased frequency of respiratory infections in the patients. Bronchi are formed by bifurcation of the trachea and gradually divided into smaller tubules called bronchioles as they enter the lungs. The diameter of these structures can change accordingly to the conditions of the internal and external environment (Hall & Guyton, 2016). Therefore, both trachea and bronchi are mainly responsible for the conduction of air to the lungs, which is the organ participating in gas exchange directly.The lungs are paired organs containing two lobes at the left side of the body and three lobes at the right side. This difference is explained by the location of the heart within the thoracic cavity (Hall & Guyton, 2016). The structural and functional unit of lungs is the alveolus. It is a tiny sac with a one cell thick wall. Such organisation contributes to the efficient exchange of gases by means of diffusion, because the thickness of membrane is the minimum, while the surface area is high. In addition, the inner surface of the alveoli is covered with surfactant, which lubricates them to prevent alveolar walls from collapsing, and dissolves gases for more efficient diffusion. The flow of air into and out of the lungs is directed by changes in volume and pressure of the thoracic cavity. During inspiration, the diaphragm contracts and moves downwards, while internal intercostal muscles contract to expand the rib cage. The increase in volume of the thoracic cavity leads to decrease in pulmonary pressure, which allows the lungs to expand and fill with the air. Due to concentration gradient, oxygen from the atmospheric air diffuses into the blood, while carbon dioxide diffuses into the alveoli to be exhaled. During expiration, the diaphragm relaxes and moves upwards, while gravity force causes the rib cage to move down. This leads to decrease in volume, which in turn causes increase in pressure forcing the air out of the lungs. However, in horizontal position, gravity cannot provide the movement of rib cage in the proper direction for expiration, and thus, external intercostal muscles have to contract. During intense physical activity, the assessor muscles of neck, back, and abdomen also participate in breathing movements to make them more intense and frequent (Hall & Guyton, 2016). Therefore, the lungs, alveoli, and breathing mechanisms are properly adapted to their functions.The functioning of tracheobronchial tree and lungs is regulated by respiratory centers of medulla oblongata and pons, as well as local reflexes. The ability of respiratory centers to regulate the frequency of breathing is based on the concentration of hydrogen ions in blood, which is an indicator of carbon dioxide concentration, by central chemoreceptors (Hall & Guyton, 2016). An example of local regulation is Herring-Breuer reflex, which prevents over-inflating of lungs during inspiration. The increased in stretching of bronchioles and lungs leads to inhibition of inspiration and expiration. There are also peripheral chemoreceptors, associated with C-fibers that detect concentration of carbon dioxide and other substances, and change the breathing rate accordingly (Coleridge & Coleridge, 2011). Therefore, most reflexes of the tracheobronchial tree and lungs are directed for regulation of breathing rate and maintenance of lung integrity.The functioning of the respiratory system can be evaluated for the detection of pathological states. Diseases in this system are usually associated with changes in the state of alveoli or efficiency of air flow into them due to blockage of airways, which in turn affects the volume of air present in the lungs or entering them. In addition, the measured values could be used as an indicator of disease progression and efficiency of the treatment process (Hall & Guyton, 2016). Therefore, several measurements and related instrumentation have been developed. They include Vitalograph, spirometry (Flesch & Dine, 2012), Peak flow meter (WebMD, 2018), and breath-holding abilities. Tidal volume, vital capacity, inspiratory and expiratory reserve volumes can be measured with the help of spirometry, while Vitalograph is used for the estimation of forced vital capacity and forced respiratory volume (Flesch & Dine, 2012). These parameters of lung functioning can be estimated for early diagnosis of chronic obstructive pulmonary disease, which can be hardly identified at the beginning. However, application of vitalograph ensures 100% sensitivity (Banka et al., 2015). Spirometry can be applied to differentiate between this condition and bronchiectasis, which has similar symptoms (Özkaya, Dirican, & Tuna, 2016). Peak flow meter is the irreplaceable device for people suffering from asthma, because it allows for easy identification of how well air enters the lungs (WebMD, 2018). Therefore, application of various measurements of respiratory system functioning is relevant for the modern clinical practice. The aim of the current paper was to master the mentioned methods and to identify patterns and correlations associated with them. MethodsFirst, general information was collected about the participants which includes height, age, weight, and gender. Then, estimation of respiratory system functioning was conducted. During measurements, the nose of the participant was closed with a clip to prevent from air leakage through it during expiration. Then the participant would breathe normally before the start of measurement. The lips of the participant were tightly wrapped around the mouthpiece of the device and followed the instructions of each experimenter. In case of spirometry, it was required to make a common exhalation, then maximum possible inhalation after the typical one. These allowed for the estimation of tidal volume, vital capacity, inspiratory and expiratory reserve volumes. In addition, the respiratory rate of the participant was calculated. During vitalograph, forced expiratory volume and forced vital capacity were measured while peak flow meter was used to estimate the force of air in liters per minute, which moves through the respiratory system. The mentioned devices indicate the volume of air passing through them and show it in the specific liters. The mouthpiece of the applied devices was cleaned after each participant. In addition, the breath holding exercise was performed, when the participants were asked to hold breath after expiration and inspiration under the normal state, as well as after hyperventilation. ResultsIn total, (46% females) took part in the study. The basic demographic characteristics measured for these persons included age, height, and weight. Table 1 represents the measures of central tendency and measures of spread for these variables among the studied sample. Table 2 shows the measures of central tendency and measures of spread for the variables recorded with the help of pneumotachograph, which include inspiratory and expiratory reserve volume, tidal volume, vital capacity, and respiration rate. Table 3 shows the measures of central tendency and measures of spread for the variables recorded with the help of vitalograph, which include forced expiratory volume and forced vital capacity, and with peak flow meter. Table 4 shows the measures of central tendency and measures of spread for the variables recorded during breath holding under rest and after hyperventilation.Table 1Measures of Central Tendency and Spread for Basic Demographic CharacteristicsMeasureAgeHeightWeightMean 18.62174.466.8Median19173.568.5Mode1816960Range18-20153-19542-97Standard Deviation0.6310.313.2Variance0.4106.39174.2Table 2Measures of Central Tendency and Spread for Variables Recorded with PneumotachographMeasureInspiratory ReserveVolume(L)Expiratory ReserveVolume(L)Tidal Volume(L)Vital Capacity(L)Respiration Rate (breaths per minute)Mean 188.8.131.52.318.1Median184.108.40.206.018Mode2.521.13.518Range0.48-40.56-4.60.5-2.182.2-8.610-30Standard Deviation0.70.70.41.35.2Variance0.50.50.21.827Table 3Measures of Central Tendency and Spread for Variables Recorded with Vitalograph and Peak Flow MeterMeasureExpiratory Volume(L)Forced Vital Capacity(L)Peak Flow(L)Mean 3.84.6509.9Median3.84.6506.2Mode4.35550Range2.1-6.22.5-6.9345-750Standard Deviation0.91.199.1Variance0.71.19815.1Then, analysis of correlation or difference between certain groups of data was performed. First, correlation between peak flow and weight was assessed with the help of Pearson correlation test. It was identified that weight shows relatively strong statistically relationship with peak flow at t=5.2, p<0.001, and r=0.66. Fig.1 represents the obtained regression line at slope=0.09, intercept=22.1, and R^2=0.43. Analysis of correlation between tidal volume and respiration rate was also performed. The obtained results indicate that tidal volume is not related with respiration rate at t=0.03, p=0.97, and r=0.006. Fig.2 represents the obtained regression line at slope=0.07, and intercept=18, R^2=3.6x10^-5.Fig.1. Correlation for Weight and Peak Flow.Fig.2. Correlation for Respiration Rate and Tidal Volume.Comparison was performed for vital capacity of lungs between males and females Student's t-test showed statistically significant difference between vital capacity of lungs between males and females at t= -4.2 and p<0.001. Fig.3 shows the difference between the stated groups. Fig.3. Difference in Vital Capacity of Lungs between Males and Females.DiscussionThe conducted analysis shows that peak flow is directly related with weight and height of the person with p<0.001. This result is in due to the prediction, as each additional unit of body requires the same amount of energy. Body cells obtain energy during aerobic respiration, which is performed with the presence of oxygen. In turn, oxygen enters the human organism through the respiratory system. The more air is used by the person per minute, the more oxygen can potentially be consumed. As larger body needs more energy, it should require more oxygen, and thus, more air should be inhaled to meet the current needs. Therefore, the peak flow increased with heavier weight and taller height of the person.The same reasoning was suggested, when relationship between tidal volume and breathing rate was studied. At rest, the body requires the specific amount of oxygen to supply all cells with sufficient energy. Increase in tidal volume indicates the increase in the amount of oxygen delivered to body tissues per single breath. Therefore, it is reasonable that the number of breaths will decrease, as tidal volume increases. However, correlation analysis between these parameters did not reveal the predicted results. In fact, there was no relationship between tidal volume and respiration rate (p=0.97). There are two possible explanations for the difference between the expected and obtained data. Firstly, tidal volume should be about 0.5 L (Hall & Guyton, 2016) for a healthy person, while data ranged from 0.5 to 2.18 L, which indicates that measurement was very inaccurate. Secondly, people with different weight and height took part in the study, and these two variables could have the significant impact on both studied variables. Therefore, it would be reasonable to repeat measurements more accurately and for the persons with similar characteristics.Difference between vital capacity of lungs between males and females appeared statistically significant as expected (p<0.001). Generally, men are larger than women, and thus, they simply have larger volume of lungs (Hall & Guyton, 2016). In addition, males have more muscle tissue, while female bodies accumulate more fat. Muscle tissue is the major consumer of oxygen, and thus, male bodies are adapted to meet this requirement by having larger lungs. In contrast, adipose tissue is not metabolically active and does not need high oxygen supply (Hall & Guyton, 2016). Therefore, the size of lungs in females is smaller than in males. In general, the individual results were consistent with the pattern recorded for group data. Neither of the participants was suffering from respiratory diseases, however one person was a smoker. Smoking has a number of negative effects on different body systems, including lungs. It may lead to chronic bronchitis, emphysema, and pulmonary obstructive disease (Hall & Guyton, 2016). Carbon monoxide present in cigarette smoke reduces the oxygen-binding capacity of blood, which leads to starvation of tissues. Indeed, the smoker participating in the experiment had elevated peak flow, which indicates that his body experiences oxygen deficiency and tries to compensate for it by inhaling higher volumes of air. The main findings of the conducted experiment indicate that the human respiratory system responds to changes in factors of the internal and external environment as expected and in accordance to the body needs. Therefore, it is possible to use the major measurements in order to identify pathologies, confirm diagnoses, or monitor the treatment progress. ConclusionMost of the expected relationships and differences between variables appeared correct, as they were supported by results of statistical analysis. It was shown that the amount of consumed air is proportional to weight of the person. Difference was identified in vital capacity of lungs between men and women. However, inverse relationship, which was expected for the respiration rate and tidal volume, was not supported by the obtained data. It could be explained by inaccurate measurements, as well as effect of side factors, including weight and height of the person. These results indicate that the respiratory system responds in accordance with body needs, and measurements of its parameters can be useful during diagnosis of diseases.