Introduction Thelungs, which are a major component of the respiratory system, are a very vitalorgan to the human body, having many functions that enable us to sustain life (1).Some of the lungs main functions are breaking down and filtering harmfulsubstances, and acting as a holding site for blood (1). However, thelungs are importantly responsible for the site of the exchange of gases, such asthe movement of oxygen and carbon dioxide from the air into and out of thelungs, which is also known as ventilation, and throughout the respiratorysystem and blood (1). What drivesventilation on a physiological level are chemoreceptors, which ensure that webreathe to maintain proper blood oxygen and carbon dioxide levels, as well aspH (2). Gasexchange of carbon dioxide and oxygen during ventilation relies on a mechanismcalled diffusion, which and depends on the surface area of the membrane of the lung,the pressure difference across the lung, and the thickness of the membrane ofthe lung (1). This is known as Fick’s law of diffusion. Moreover, detrimentalactions on the 3 variables of Fick’s law of diffusion can leave harmful impactson the lungs and respiratory system, and can ultimately inhibit normal lungfunction (1).
Diseases of the lungs would leave this type of negativeeffect on the respiratory system and hinder the 3 variables of Fick’s Law ofdiffusion. Thereare two main categories of diseases that can affect the lungs, which areobstructive diseases and restrictive diseases (3). These lungdiseases can have detrimental effects on the lung because they can result in decreasedairway size, swollen or loss of alveolar sacs, and ultimately reduced gasexchange (3).
Lung diseases, as well as the overall function of thelung can be evaluated using a method known as spirometry (4).Spirometry is a tool used to evaluate the breathing mechanisms of a patient andallow doctors to detect pulmonary diseases in patients displaying abnormal lungfunction (4). Spirometry can consist of static and dynamic tests tomeasure variables such as vital capacity, which is the highest volume of airthat can be exhaled out of the lungs after taking the largest inspirationpossible, as well as forced vital capacity (FVC), which is the amount of gasthat is expelled out of the lungs as fast and hard as possible after thegreatest possible inspiration (3). Themain purpose of this lab is to study pulmonary function through static and dynamictesting such as slow breathing, forced vital capacity and maximum voluntaryventilation, and identify how resting and dynamic lung values may differ undernormal and obstructed breathing circumstances. Moreover, control of ventilationwill be studied as well to determine how the length of breath holding maychange during resting, hyperventilating, and exercise procedures. Wehypothesize that resting and dynamic lung values will be greater under normalbreathing conditions and decreased during obstructed airway conditions sincethe flow of air into and out of the lungs would be altered. We also hypothesizethat breath holding will be the greatest after hyperventilation due todecreased amounts of carbon dioxide in the blood, and the least afterexercising due to the body’s new high demand for oxygen. MethodsSubjectCharacteristics and Environmental ConditionsThere wasa total of four participants in this lab.
For the static and dynamic lungtesting regarding resting lung volumes, forced vital capacity, and maximumvoluntary ventilation, 2 subjects participated in these breathing exercises. Thefirst subject was a 20-year-old moderately active male who was 68 kilograms inweight and 163 centimetres in height. The second subject was a 20-year-old moderatelyactive female who was 50 kilograms in weight and 171 centimetres in height. Subjects3 and 4 that completed the different breath hold procedures were a 20-year-oldfemale and a 20-year-old male respectively. Additionally, the temperature ofthe room was 22.
5 degrees Celsius and the barometric pressure of the room was744 mmHg. It is also noted that subject 2 had a history of recurring bronchitisover the past 5 years. A handheld spirometry system was used to recordbreathing, as well as a software called winspiroPRO to document all spirometrydata.Staticand Dynamic Lung Testing Subject1 started the lab with static lung testing, and began by breathing normallyinto the mouthpiece with a nose clip on, facing away from the computer screento not influence any breathing patterns. Once a normal breathing patternensued, subject 1 inhaled his largest possible breath and exhaled as much airas he could to end the trial. The same trial was repeated an additional twotimes.
Subject 1 then proceeded to complete the dynamic lung testing, the firsttest being forced vital capacity (FVC). For the forced vital capacityprocedure, subject 1 began by breathing normally into the mouthpiece, againwith a nose clip, then inhaled his largest breath possible and held it for onesecond, followed by a forceful and rapid exhale that lasted about 5 seconds.This test was performed a total of three times and all data was recorded. Forthe final dynamic lung test of maximum voluntary ventilation, subject 1 breathedas deeply and as rapidly as possible into the mouthpiece for 15 seconds whilegiving maximal effort. The data was recorded and the test was repeated oncemore, as well as having a break in between the two trials to ensure the subjectdid not feel too light headed. Subject 1 then completed the same static anddynamic tests again, however, this time he completed the same tests as abovewith a flow restricting stopper that was placed in the mouthpiece to simulate anobstructed airway. Once subject 1 completed his tests, subject 2 performed thesame static and dynamic lung tests above; first under normal breathingcircumstances and then under obstructed breathing circumstances. Breath-holdingProcedures Subjects3 and 4 began to prepare for the 3 breath-holding procedures.
In a seatedposition, participants 3 and 4 took their deepest breath and held it for aslong as possible for the resting breath hold procedure. While doing so, theyensured to keep their noses plugged so no ventilation was done whatsoever.Their breath-hold times were recorded.
The second breath-hold procedureconsisted of subjects 3 and 4 voluntarily hyperventilating for 1 minute,followed by holding their breath for as long as possible. Their breath holdtimes were recorded once again. Lastly, participants 3 and 4 cycled for 90 secondsat a cadence between 75 and 85 rpm against a resistance of 200W.
Directly aftercycling, participants 3 and 4 tried to hold their breath as long as they couldonce again, and their breath hold times were recorded. ResultsDuringstatic lung testing, it was observed that normal breathing patterns into thespirometer resulted in higher resting lung volumes (Figure 1). Obstruction inbreathing caused a decrease in all resting lung volumes by roughly 0.15 to 0.5litres in subject 1(Figure 1).
Similar results were seen in subject 2, howeversubject 2 had a slightly higher tidal volume of 1.3 L with obstructed breathingwhen compared to 0.89 L during normal breathing (Figure 2). Subject 1 had aforced vital capacity of 3.
37 litres during normal breathing, and only 3.1litres during obstructed breathing (Figure 3). Subject 2 had a higher forcedvital capacity during normal breathing as well (3.
05 L) compared to 2.85 litresduring obstructed breathing. For the forced expiratory volume at one secondvalues, subject 1 and 2 had nearly identical results, with roughly 3 L expiredat one second during normal breathing, and roughly 2.5 litres expired at onesecond during obstructed breathing (Figure 4) There was a slight reduction inforced expiratory volume percentage from normal breathing to obstructedbreathing in both subjects. However, the percentage values for both subjectsand both breathing conditions remained above 80% (Figure 5).
For subject 1, hispeak expiratory flow decreased from 4.01 L/s during normal breathing, to 2.88L/s during obstructed breathing, and for subject 1, her peak expiratory flowdecreased from 6.48 L/s during normal breathing, down to 2.77 L/s duringobstructed breathing (Figure 6).
Obstruction also reduced FEF25-75 in bothsubjects as well compared to normal breathing conditions (Figure 7). Furthermore,almost identical results were seen during the maximum voluntary ventilationtest between subjects 1 and 2. Both subjects had a MVV of about 112 L/minduring normal breathing, and a drastically lower MVV during obstructed breathingof around 70 L/min (Figure 8). It wasobserved that between both subjects 3 and 4, breath holding lasted the longestafter hyperventilating voluntarily for 1 minute; subject 3 lasted 55 secondsafter hyperventilating and subject 4 lasted 120 seconds after hyperventilating(Figure 9). Breath holding lasted the shorted duration after exercising at 200watts for 90 seconds for both subjects, subject 3 only able to hold theirbreath for 6 seconds and subject 4 able to hold their breath for 7 seconds(Figure 9). Discussion Theresults indicate that the hypotheses made were able to be validated by the datacollected in this experiment. In the static lung volume tests, variables suchas inspiratory and expiratory reserve volumes and vital capacity all decreasedduring obstructed breathing compared to normal breathing in both subjects 1 and2, as to be expected. This is due to the reduction of airflow because of airwayswelling and compression, which alters and limits the flow of air into and outof the lungs (3).
Tidal volume appeared to decrease in obstructedbreathing when compared to normal breathing in subject 1, and increased duringobstructed breathing for subject 2. However, tidal volume is said to not changedrastically in the case of an obstructive lung disease since tidal volumerefers to the air that is inhaled or exhaled during normal shallow breathing,not during maximal effort breathing, therefore having a less noticeable change (3). Moreover, forced vital capacity, adynamic lung test, decreased in both subjects during obstructed breathing whencompared to normal breathing, which again was to be expected due to increasedchallenge to expire entirely. Studies show that in patients who demonstrate anobstructive pulmonary disease, they generate a smaller flow of air upon expirationafter trying to take a maximum exhalation (5). The time it takes forexpiration to occur while breathing with an obstruction is inadequate to emptylung volume due to decreased flow, therefore when an obstruction in breathingis placed, not the entire amount of air will be exhaled out during anexpiration that lasts roughly 5 seconds in a dynamic lung test (5). Additionally,the dynamic lung variable FEF25-75 is expected to decrease as a result of airwayobstruction, which was seem in both subjects 1 and 2 when compared to normalbreathing (4). Lastly, results indicate that maximum voluntaryventilation was seen to decrease during obstructed breathing testing whenlooked at next to normal breathing testing. Frequency of breathing as well asvolume is expected to decrease due to the added challenge of breathing with anobstruction, which results in a decreased flow rate (3).
If flow isdecreased, volume of air that is inhaled per minute will inevitably bedecreased as well (3). This demonstrates that normal and expectedresults were seen in static testing, forced vital capacity and maximumvoluntary ventilation testing. Expectedresults were seen in subjects 3 and 4 during the breath holding procedures. Breathholding duration increased after voluntarily hyperventilating for 1 minute, anddecreased drastically after exercising at 200 watts for 90 seconds. It isexpected for breath holding durations to increase in length almost twice after hyperventilation,due to high oxygen and low carbon dioxide conditions of the body since thedrive for respiration is decreased (7).
However, the opposite istrue for breath-holding after exercise. Ventilation needs to increase during andafter exercise to fulfill the body’s needs for oxygen, which is why subjects 3and 4 were not able to hold for very long after exercising at a relatively highpower output (1). The signals that chemoreceptors send are what isresponsible for our ability to hold our breath for certain periods of time (1).Chemoreceptors respond to changes in blood pH and carbon dioxide levels (1).
When exercising, the body’s need for oxygen increases, and gets fulfilled byincreasing ventilation. Chemoreceptors in the muscle and lung act upon thisneed for oxygen and are activated so this demand is fulfilled (1).During breath holding after hyperventilation, chemoreceptors are inhibited dueto the body’s sufficient oxygen levels, and are activated later to stimulateventilation when the subjects couldn’t hold their breath any longer (1).
Additionally, the role of chemoreceptors is also seen in obstructive lungdiseases as well. In patients with obstructive lung diseases, their partialpressure and saturation of oxygen are typically lower and their carbon dioxideconcentrations are higher due to decreased air flow, so the body stimulateschemoreceptors to try to increase ventilation to increase blood oxygen levels (3). Furthermore,obstructive lung diseases as well as restrictive lung diseases both have anegative impact on gas exchange. When there is an obstruction in the airway,there is a decreased amount of air into the lung and to the alveoli,potentially causing the alveoli to die, which decreases surface area in thelung (3). Alveoli can also become swollen and filled with thickmucus, which causes a greater distance between the alveoli and the blood, aswell as increases thickness of the sheet (3). Additionally, if theairway becomes swollen in a patient with an obstructive pulmonary disease, thepressure difference decreases as well (3). These are all negativeaffects on Fick’s law of diffusion, and therefore resulting in reduceddiffusion and gas exchange. Furthermore, in restrictive lung diseases, there isevidence that alveoli become scarred and lungs become very stiff, making itmore difficult to inhale or exhale a high volume of air at a certain time (6).
This inevitably leads to hypoxia and reduced gas exchange as well (6).Conclusion Overall,the results of this experiment could be supported by the hypotheses that weremade. The purpose of this lab was to study pulmonary function testing and tosee how resting lung values and dynamic lung values may differ under normal andobstructed breathing circumstances. Expected results were seen in static lungtesting, forced vital capacity and maximum voluntary ventilation tests. Normalbreathing always yielded higher resting and dynamic lung values when comparedto obstructed breathing. Moreover, breath holding durations were evaluatedafter 3 different exercises, and it is concluded that hyperventilation canimprove breath holding duration, whereas exercise will decrease breath holdingduration.
To conclude, this lab greatly outlines the importance of thepulmonary system to our health and how detrimental a lung disease can be, butalso how important pulmonary function testing is to detect problems of the lungwhen they arise. · Obstructivelung disease can alter flow into and out of the lungs, interfering with all 3 componentsof Fick’s for diffusion, ultimately hindering diffusion and gas exchange in therespiratory system.· Breathholding can be held for a much longer duration after voluntary hyperventilationdue to the body’s hyperoxic conditions, whereas breath holding can only be heldfor a short duration after exercise due to the body’s need to ventilate tofulfil its needs for oxygen.