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Respiration is a vital process for the survival of every organism. This processincludes the passage of air into and out of the lungs and a result of skeletal musclecontraction, otherwise known as ventilation, and the transport of oxygen and carbondioxide by the blood between the lungs and tissues. This important exchange of gases

in the body is taken part by the respiratory system through working cooperatively withthe circulatory system.The primary role of the heart is the pumping of deoxygenated blood to pulmonary

capillaries. As the blood enters the pulmonary circuit, gas exchange occurs between the

blood and the alveoli, hence, oxygenation of the blood happens. The oxygenated blood

is then pumped by the heart to the tissues that are actively metabolizing. In connection

to, the main product of metabolism, which is CO2 is continuously diffusing into the

blood and returns to the heart for another cycle of oxygenation.

There are two processes involved during respiration, inspiratory and expiratory

processes, both of which can be further classified as quiet and forced. These two

processes involve several muscles such as diaphragm, external intercostal muscles,

internal intercostal muscles, and abdominal muscles. Diaphragm is a dome-shaped

muscle which divides the thoracic and abdominal cavities. During inspiration, the

diaphragm descends and the external intercostal muscles contract, thereby increasing

the volume of air in the thoracic cavity, which in turn reduces the pressure in the

thoracic cavity. This active process allows atmospheric gas to enter the lungs and

usually requires expenditure of energy in the form of ATP.

On the contrary, expiration is a passive process wherein it involves the relaxation

of the muscles. During this process, the diaphragm and the external intercostal muscles

relax, thereby increasing the pressure in the thoracic cavity as the volume of air

decreases. This process facilitates forcing air out of the lungs. However, during

activities like running, expiration turns to be an active process involving the contraction

of internal intercostal muscles and abdominal muscles.

One important parameter to measure the efficiency of the respiratory process is

the minute ventilation which measures the amount of air that flows into and out of the

lungs in a span of a minute. It can be obtained by using the formula,

Minute ventilation= frequency of breathing (bpm) x tidal volume (500mL)

This activity aims to understand the basic principles in the mechanics and

regulation of the respiratory system. Also, to understand the different concepts in a

simulated lung so as to understand how the respiratory system works and adapts to

these different simulations.

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ACTIVITY 1: MEASURING RESPIRATORY VOLUMES AND CALCULATING

CAPACITIES

The objectives of this activity include, first, to understand the concepts underlyingthe process of ventilation, phases of respiration, the muscles involved in the respiratory

process, respiratory volumes, and capacities. Second, is to identify the roles of skeletal

muscles in the mechanics of breathing. Third, is to understand the changes in volume

and pressure in the thoracic cavity during the breathing process. Lastly, is to understand

the effects of airway radius on resistance, and their coupled effect on airflow.

Breathing involves two phases namely, inspiration and expiration respectively.

Both inspiration and expiration are classified either quiet or forced. In quiet inspiration,

the inspiratory muscles relax and the diaphragm ascends superiorly as the chest wall

moves inward, the thorax returns to its normal shape as given by its elastic properties.This process normally moves approximately 0.5 L of air into and out of the lungs and

this value varies with sex, age, physical condition, and respiratory needs.

Table 1. Muscles involve during respiration

Inspiration Expiration (Active)

Diaphragm Abdominal Muscles

External Intercostal Muscles Internal Intercostal Muscles

There are different respiratory volumes and capacities that are set as parametersin the evaluation of the respiratory process. Tidal volume (TV) is the amount of air

inspired and expired with each breath during quiet respiration and is approximately

equal to 500 ml. Inspiratory reserve volume (IRV) is the amount of air that can be

forcefully inspired and is approximately 3100 mL in male and 1900 in female.

Expiratory reserve volume (ERV) is the amount of air that can be forcefully expired

and is approximately 1200 mL in male and 700 mL in female. Residual volume (RV) is

the amount of air remaining in the lungs after forceful and complete expiration and is

approximately 1200 mL in male and 1100 mL in female. Total lung capacity (TLC) is

the maximum amount of air contained in lungs after a maximum inspiratory effort and be

calculated using the formula,

TLC= TV + IRV + ERV + RV and is approximately 6000 mL in male and 4200 mL

in female.

Vital capacity (VC) is the maximum amount of air that can be inspired and expired

through maximal effort and can be calculated using the formula,

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VC= TV + IRV + ERV and is approximately 4800 in male and 3100 in female.

Forced vital capacity (FVC) is the amount of air that can be expelled after taking the

deepest possible inspiration and forcefully doing expiration completely and rapidly.

Forced expiratory volume (FEV1) is a measure of the percentage of the vital capacity

that is expired in one second and usually ranges from 75-85% of the vital capacity.

Results:

Radius Flow(L/min

)

TV ERV IRV RV VC FEV1 TLC BreathRate

5.00 7,485 499 --- --- --- --- --- --- 15

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Radius Flow(L/min

)

TV ERV IRV RV VC FEV1 TLC BreathRate

5.00 7,500 500 1,200 3,091 1,200 4,791 3,541 5,991 15

Radius Flow(L/min

)

TV ERV IRV RV VC FEV1 TLC BreathRate

4.50 4,920 328 787 2,028 1,613 3,143 2,303 4,756 15

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Radius Flow(L/min

)

TV ERV IRV RV VC FEV1 TLC BreathRate

4.00 3,075 205 492 1,266 1,908 1,962 1,422 3,871 15

Radius Flow(L/min

)

TV ERV IRV RV VC FEV1 TLC BreathRate

3.50 1,800 120 288 742 2,112 1,150 822 3,262 15

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Radius Flow(L/min

)

TV ERV IRV RV VC FEV1 TLC BreathRate

3.00 975 65 156 401 2,244 621 436 2865 15

Table 2: Summary of results

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As seen in the results, as the radius of the airway is gradually reduced from 5.00,the flow rate also decreases. This can be explained by the increased resistance insmaller radius. A reduction in the airway radius would mean an increased resistance.This resistance will tend to constrict the airway thereby, limiting and reducing theamount of air that can flow in the airway, as seen in the reduced flow rate.

Consequently, all of the measured parameters also decreased with thedecreasing radius except for the residual volume. As seen on table 2, as the radius ofthe airway is reduced, the residual volume increases. The residual volume is known tobe the amount of air that remains in the lungs after forceful and complete expiration, asthe airway constricts because of the decreased radius and increased resistance, thepassage of air is limited and most of the inspired air remains in the lungs and isexhibited by increased residual volume. In addition to, the breath rate remainedconstant all throughout since there is no need for compensatory increase or decrease inrespiratory rate.

In summary, it can be concluded that the radius is inversely proportional to

resistance but is directly proportional in the flow rate. And such relationship is exactlyexemplified in a decrease in TV, ERV, IRV, VC, FEV1, and TLC and an increase in RV.

ACTIVITY 2: Comparative Spirometry

The objectives of this activity include, first, to understand the terms spirometry,spirogram, emphysema, asthma, inhaler, moderate exercise, and heavy exercise.Second, is to observe and compare spirograms collected from healthy patients to that ofemphysema patients. Third, is to observe and compare spirograms collected fromhealthy patients to those of suffering from asthma attacks. Fourth, is to observe and

compare the spirogram collected from an asthmatic patient while suffering an acuteasthma attack to that taken after the patient uses an inhaler for relief. And lastly, toobserve and compare spirograms collected from volunteers who had undergonemoderate to heavy exercise.

In evaluation of the volume inspired and expired over a specified period of time, adevice known as spirometer is usually used. In doing so, there are differentclassifications of breathing that had been identified. First is emphysema breathing, it isdue to loss of elastic recoil in the lung tissue, increased airway resistance, andcharacteristic changes in the lungs such as it is more flimsy, exerts less anchoring onsurrounding airways, over compliance, expands easily, and inability to passively recoiland deflate. In patients suffering from emphysema, they exemplify the followingcharacteristics: a greater effort required to expel air, a noticeable exhausting musculareffort in expiration, and a slow expiration.

Another classification would be acute asthma attack breathing which is primarilydue to bronchiole smooth muscle spasms which result in the airway constriction. Inaddition to, it may also be caused by clogged airway with thick mucus secretions andincreased airway resistance. The inflammatory response may be triggered by allergens,

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extreme temperature changes, and exercise. The most commonly used form of relief isthe use of an inhaler which contains a smooth muscle relaxant that consists of 2agonist and acetylcholine antagonist. This results in a relieved bronchospasms andbronchiole dilation. Moreover, it may also contain corticosteroid which is an anti-inflammatory agent that reduces airway resistance.

And the last classification is breathing during exercise. In moderate aerobicexercise, there is an increased metabolic demand and is compensated by an increasein the rate of breathing and increased tidal volume. Consequently, during heavyexercise, there is also increase in the metabolic demand and is also compensated by anincrease in the rate of breathing and increased tidal volume up to the maximumtolerable units.

Results:

Patient

Type

TV ERV IRV RV FVC TLC FEV1 FEV1

(%)Normal 500 1,500 3,000 1,000 5,000 6,000 4,000 80%

PatientType

TV ERV IRV RV FVC TLC FEV1 FEV1(%)

Emphysema 500 750 2,000 2,750 3,250 6,000 1,625 50%

Patient TV ERV IRV RV FVC TLC FEV1 FEV1

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Type (%)

AcuteAsthmaAttack

300 750 2,700 2,250 3,750 6,000 1,500 40%

PatientType

TV ERV IRV RV FVC TLC FEV1 FEV1(%)

Asthma

AttackPlus

Inhaler

500 1,500 2,800 1,200 4,800 6,000 3,840 80%

PatientType

TV ERV IRV RV FVC TLC FEV1 FEV1(%)

ModerateExercise

1,875 1,125 2,000 1,000 ND 6,000 ND ND

PatientType

TV ERV IRV RV FVC TLC FEV1 FEV1(%)

HeavyExercise

3,650 750 600 1,000 ND 6,000 ND ND

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Table 3: Summary of results on the classification of breathing and their

parameters.

As compared to the normal patient, the tidal volume of the patient with an acuteasthma attack is lower. Apparently, the patient suffering from emphysema and acuteasthma attack plus inhaler has the same tidal volume to that of the normal patient while

those who had done exercise has greater tidal volume.

In the expiratory reserve volume, all of the patients had shown a lesser ERVcompared to the normal patient. Interestingly, the lowest ERV is exemplified by thepatients who did a heavy exercise, those with acute asthma attack and emphysema.This may be due to the airway constriction that they experience when experiencingemphysema and acute asthma attack. As for the exercise, during heavy exercising,there is a greater need for ventilation, thus, it is compensated by increased respiratoryrate and reduction in the expulsion of air from the body.

In the inspiratory reserve volume, all of the patients had shown a lesser IRV

compared to the normal patient. The lowest IRV was seen on patients who hadundergone heavy exercise because there is a need for an increased respiratory rate sotherefore, the amount of air remaining in the lungs will be reduced.

The residual volume of the patients who had done exercise is comparably thesame to that of the normal patient. That is, the amount of air that remains in the lungsafter complete expiration would be the same for patients not experiencing pulmonaryproblems. On the contrary, in patients with acute asthma attack, it is greater, and morenoticeably higher in patients with emphysema. This is due to the airway constriction inthese patients that resists the flow of air from the lungs. Consequently, it is also in thesepatients who had lesser FVC and FEV1 compared to normal, and is again due to samereasons. However, the RV of patients who used inhaler gradually decreased due torelief in clogged airway.

The total lung capacity remained the same in all patients, that is, 6000 mL. Thismeant that all of the patients used and examined were males.

In summary, it can be concluded that different breathing classification amongpatients have a varied values for their respiratory volumes and capacities that deviate

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as compared to that of the normal patient. This is primarily due to obstructed passage ofair from the lungs due to airway constriction. And that, in cases like acute asthmaattack, an inhaler can provide a relief for the airway.

ACTIVITY 3: Effect of Surfactant and Intrapleural Pressure on Respiration

The objectives of this experiment include, first, is to understand the termssurfactant, surface tension, intrapleural space, intrapleural pressure, pneumothorax,and atelectasis. Second, is to understand the effect of surfactant on surface tension andlung function. And lastly, to understand how negative intrapleural pressure preventscollapse.

An important force that can be accounted during respiration is the surfacetension. It is a tension produced by unequal attraction in a gas-liquid boundary. Thisforce resists any force that tends to increase surface area of the gas-liquid boundaryand acts to decrease the size of hollow spaces such as those in alveoli and microscopic

air spaces. In lungs, there is a surfactant which is a detergent-like mixture of lipids andproteins that reduces the attraction between water molecules, thereby, decreasingsurface tension. It is contained in the aqueous film covering the alveolar surfaces

The negative intrapleural pressure is crucial in preventing the collapse of theairway. This pressure can be caused by two different forces dependently. First is by thetendency of the lung to recoil because of its elastic properties and the surface tension ofthe alveolar fluid. Second, the tendency of the compressed chest wall to recoil andexpand outward. The combined action of these force pull the lungs away from thethoracic wall resulting to a partial vacuum in the pleural cavity.

Intrapleural space is lower than atmospheric pressure , hence, any openinggenerated in the pleural membranes equalizes the intrapleural pressure withatmospheric pressure resulting to a condition known as Pneumothorax. When thiscondition further results to a lung collapse, it is otherwise termed as atelectasis.

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Results:

Radius Breath

Rate

Surfactan

t

Pressure

Left

Pressure

Right

Flow

Left

Flow

Right

Total

Flow5 15 0 -4 -4 49.69 49.69 99.38

Radius BreathRate Surfactant PressureLeft PressureRight FlowLeft FlowRight TotalFlow

5 15 2 -4 -4 69.56 69.56 139.13

Radius BreathRate

Surfactant

PressureLeft

PressureRight

FlowLeft

FlowRight

TotalFlow

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5 15 4 -4 -4 89.44 89.44 178.88

Radius BreathRate

Surfactant

PressureLeft

PressureRight

FlowLeft

FlowRight

TotalFlow

5 15 0 -4 -4 49.69 49.69 99.38

Radius BreathRate

Surfactant

PressureLeft

PressureRight

FlowLeft

FlowRight

TotalFlow

5 15 0 0.00 -4 0.00 49.69 49.69

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Table 4: Summary of results

Based on the results, it can be seen the effect of a surfactant on the maintenanceof a negative intrapleural pressure. As the surfactant was applied to the lungs, the

pressure on the left and right lung was maintained like that of the start of the exercise.Furthermore, it increased the flow rate on each lung, also the total flow as comparedwhen the surfactant was absent.

In summary, it can be concluded that pulmonary surfactant is not just important inpreventing the collapse of the lungs as in the maintenance of negative intrapleuralpressure, but also in enhancing the efficacy of each lung by increasing the flow of air.

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Literatures Cited:

Griff, Edwin, et al.(2012). Physio Ex (9.0) Laboratory Simulations in Physiology.Pearson Education, Inc.: San Fransisco

Guyton, A. and Hall, J., (1994). Textbook of Medical Physiology. 9 th edition. W.B.Saunders Company:

Pennsylvania.