2011 BioE 210 Lab Report April 20, 2011Section 013Peter Sords

Lesson 13: Pulmonary Function II

INTRODUCTION:The measurement of lung volumes and the rate of air movement (inflow) are important tools in

assessing the health and capacities of a person. In this experiment, we will measure a subject’s Forced Vital Capacity (FVC), which is the maximal amount of air that person can forcibly exhale after a maximal inhalation, along with Forced Expiratory Volume (FEV) and Maximal Voluntary Ventilation (MVV).

Forced Expiratory Volume (FEV):Forced Expiratory Volume (also refered to as forced vital capacity or timed vital capacity) is a

test in which limit is placed on the length of time a Subject has to expel vital capacity air. FEV 1, FEV2, and FEV3 are defined as the percentage of vital capacity that can be forcibly expelled after a maximal inhalation in the period of 1, 2, and 3 seconds, respectively. The normal adult is able, with maximal effort, to expire about 66-83% of his/her viatal capacity in one second (FEV1), 75-94% of their vital capacity in the second second (FEV2), and 78-97% of their vital capacity in the third second (FEV3). We expect that the results for FEV values obtained during this experiment are close to these ranges.

Maximal Voluntary Ventilation (MVV):Maximal Voluntary Ventilation (also known as maximal breathing capacity) measures peak

performance of the lungs and respiratory muscles. MVV is calculated as the volume of air moved through the pulmonary system in one minute while breathing as quickly and deeply as possible (hyperventilation). In performing this test, Subject inspires and expires as deeply and as rapidly as possible (> 1 breath/sec) while the tidal volume and the respiratory rate are measured. Because the maximal breathing rate is difficult to maintain, Subjects hyperventilates for a maximum of 15 seconds. Then, to calculate MVV, the average volume per respiratory cycle 9liters) is multiplied by the number of cycles per minute (liter/min). Normal values vary with sex, age, and body size. MVV is a measure of how much your pulmonary system limits your capacity to work or exercise. After conducting the tests in this experiment, we also expect to get a close to normal result for our MVV measurement.

RESULTS:Graph 1:

Graph 2:

Comparison of FEVx %to Normal Values:

Time Interval

(sec)

Forced Expiratory Volume (L)

Vital Capacity (VC)

FEV/VC (FEV/VC)x 100

FEVx

Averages for

reference

0-1 2.425 4.412 0.5496374

55% FEV1 83%

0-2 3.950 4.412 0.8952856

90% FEV2 94%

0-3 4.388 4.412 0.9945603

99% FEV3 97%

MVV Measurements:

1) Number of cycles in 12-second interval: 152) Calculate the number of respiratory cycles per minute (RR):

RR = Cycles/min = Number of cycles in 12-second interval x 5 = 75

3) Measure each cycle:

Cycle Number

Measurement (L)

Cycle Number

Measurement (L)

1 1.203 9 1.4372 1.238 10 1.2033 1.219 11 1.2564 2.141 12 1.4085 1.366 13 1.226 1.289 14 1.1837 1.363 15 1.1838 1.242 16

4) Calculate the average volume per cycle (AVPC):

AVPC = Sum/ # cycles = 18.850/15 = 1.257

5) Calculate the MVVest

MVV = AVPC x RR = 1.256 x 75 = 94.249

QUESTIONS:

E. How do Subject’s FEVx values compare to the average?FEV1 is less than averageFEV2 is less than averageFEV3 is greater than average

F. Is it possible for a Subject to have a vital capacity (single stage) within normal range but a value for FEV1 below normal range? Explain.Yes, if the subject

H. How does the Subject’s MVV compare to others in the class?Same as.

I. Maximal voluntary ventilation decreases with age? Why?As a person ages, the natural elasticity of the lungs decreases, this translates into smaller and

smaller lung volumes and capacities as we age. When determining whether or not your patient has normal PFT findings, it would be important to compare the patient with the PFT results of a normal person of the same age and gender.

J. Asthmatics tend to have their smaller airways narrowed by smooth muscle constriction, thickening of the walls, and mucous secretion, how would this affect vital capacity, FEV1 and MVV?

When an asthmatic exhales vital capacity with maximal effort, FEV and MVV measurements are all reduced due to the mucus secretion and smooth muscle action which reduces airway diameter and making it take longer to completely exhale vital capacity against the increased airway resistance.

K. Bronchodilator drugs open up airways and clear mucous. How would this affect the FEV and MVV measurements?This would increase values for FEV and MVV and for patients with asthma, bring measurements of FEV and MVV closer to normal.

L. Would a smaller person tend to have less or more vital capacity than a larger person?A smaller person would have a lesser vital capacity than a larger person. This follows from the equation for prediction vital capacity,

V.C. = .052H - .022A – 3.60Where H is height and A is age; predicted vital capacity varies with height because a taller person has a larger chest and therefore larger chest capacity and vice versa for a smaller person

M. How would an asthmatic person’s measurement of FEV1 and MVV compare to an athlete? Explain.The FEV1 and MVV measurements for a person with asthma would be significantly lower than those of an athlete. This is because as stated early an person with asthma would have less than normal measurements and an athlete, with a larger lung capacity and more efficient lung s, would have higher than normal measurements.

SUMMARY:The respiratory or pulmonary system performs the important functions of supply oxygen during

inhalation, removing carbon dioxide during exhalation, and adjusting the acid-base balance of the body by removing acid-forming CO2. Because oxygen is necessary for cellular metabolism, the amount of air that the pulmonary system provides is important in setting the upper limits on work capacities or metabolism. Therefore, the measurements that we obtained during this lab, such as forced vital capacity (FEV) and maximal voluntary ventilation (MVV) are measurements that can be used to assess the health capacity of a person.

Using an airflow transducer and a method similar to that done in lesson 12 of the Biopac, we were able to get graphs and extrapolate measurements that led to the calculation of values of FEV 1, FEV2, FEV3 and MVV. All of our values fell within the normal ranges except for FEV 1, which was below the normal range. The data we obtained from the experiment gave us important insight into the subject’s pulmonary function and the methods we used can be an important pulmonary function test for the following reasons:

Screening for the presence of obstructive and restrictive diseases Evaluating the patient prior to surgery - this is especially true of patients who are old, are known

to have a pulmonary disease, are obese, have a history of smoking, or are going to be under anesthesia for a long period of time

Documenting the progression of a pulmonary disease Documenting the effectiveness of therapeutic intervention