Experiment 26Lung Volumes and Capacities

IntroductionPulmonary function tests are a broad range of tests that measure lung volumes and

capacities that are usually done in a health care provider's office or a specialized facility. In other words, they measure how well the lungs take in and exhale air and how efficiently they transfer oxygen into the blood. Lung volumes and capacities are related to a person’s age, weight, gender and body position. In fact, vital capacity decreases with age, in supine position as compared with erect (sitting or standing posture) and with restrictive and obstructive lung diseases. On the other hand, residual volume increases with age and with obstructive lung diseases such as emphysema.

Perhaps the oldest device and the most commonly used lung function screening study is spirometry. Spirometry measures how well the lungs exhale. The information gathered during this test is useful in diagnosing certain types of lung disorders, but is most useful when assessing for obstructive lung diseases (especially asthma and chronic obstructive pulmonary disease, COPD).

A wet spirometer measures lung volumes based on the simple mechanical principle that air, exhaled from the lungs, will cause displacement of a closed chamber that is partially submerged in water. The spirometer consists of two chambers: (1) a larger chamber which is filled with water and has a breathing hose attached to it, and (2) a smaller chamber which is inverted inside the first and "suspended" in water. A counterweight and indicator are attached to the inverted chamber. Air blown into the inverted chamber causes it to rise and move an indicator along a scale. The scale is calibrated in liters to give lung volume measurements (Figure 1). The various lung volumes are defined below and illustrated in Figure 2.

Figure 1: Wet spirometer

Figure 2: Principle of using a wet spirometer to measure lung volumes

Relation to the Case

In the case, we have a patient who has symptoms of cough and shortness of breath. His chest x-ray showed symptoms of infiltrates and pneumonia which will definitely affect his breathing. Thus, it is important to perform pulmonary function tests such as spirometry to measure the patient’s lung volume and capacities. This can help determine the degree of difficulty the lungs are going through. It can also be used after the administration of medications to assess their effect, and to measure progress in disease treatment.

Objectives of the Experiment1. To define and measure the various lung volumes and capacities2. To compare the values obtained between a female and a male subject.

MethodologyThe different lung volumes and capacities were measured with the use of a wet

spirometer taken with the subject standing.The various lung volumes and capacities were done in three trials and the average

of each was taken. The ones measured were as follows:Tidal Volume – The subject was asked to inhale a normal breath. After which,

he/she was asked to place the mouthpiece of the spirometer between the lips and then exhale normally into the spirometer.

Expiratory Reserve Volume (ERV) – After exhaling normally, the mouthpiece is placed between the lips and the subject was asked to exhale forcefully all the additional air possible.

Inspiratory Reserve Volume (IRV) – The subject was asked to breathe in deeply as much as he/she can. Then place the mouthpiece and exhale normally. The value recorded here is subtracted from the tidal volume to get the IRV.

Vital Capacity – Breathe in maximally, place the mouthpiece and then forcibly exhale all the air possible.

Inspiratory Capacity (IC) – After exhaling normally, breathe in as deeply as possible, place the mouthpiece and exhale normally.

Figure 3: Testing of the subjects involved

ResultsMarco Trial 1 Trial 2 Trial 3 Average

TV 0.4 0.5 0.7 0.53 LERV 0.7 0.7 1.0 0.80 LIRV 1.1 – 0.4 = 0.7 1.4 – 0.5 = 0.9 1.2 – 0.7 = 0.5 0.70 LVC 3.0 3.5 4.5 3.66 LIC 1.1 1.4 1.2 1.23 L

Figure 4: Tabulated result of the male subject’s different lung volume and capacities

Isay Trial 1 Trial 2 Trial 3 AverageTV 0.3 0.2 0.2 0.23 L

ERV 0.6 1.0 0.8 0.80 LIRV 0.5 – 0.3 = 0.2 0.4 – 0.2 = 0.2 0.4 – 0.2 = 0.2 0.20 LVC 1.4 1.4 1.2 1.33 LIC 0.5 0.4 0.4 0.43 L

Figure 5: Tabulated result of the female subject’s different lung volume and capacities

DiscussionThe measurement of the different lung volumes and capacities by the use of a wet

spirometer was done with the subject standing so that the abdominal organs do not interfere with the diaphragm as it contracts and moves downward, pushing out the abdomen and creating suction which draws in the air and expands the lungs.

The various lung volumes and capacities that were measured using the spirometer are the tidal volume, expiratory reserve volume, inspiratory reserve volume, vital

capacity and inspiratory capacity. The tidal volume or the resting tidal volume is the volume of air entering the lungs during a single inspiration which is approximately equal to the volume leaving the lungs on the subsequent expiration. The normal value of which is 500ml/0.5L. The expiratory reserve volume is the additional volume of air that can be expired after the resting tidal volume which amounts to 1500 ml. Meanwhile, the amount of air than can still be inspired after the resting tidal volume is termed inspiratory reserve volume which is about 3000 ml. On the other hand, the capacities are the sums of the two or more lung volumes. Inspiratory capacity is the maximum volume of air that can be inspired from end expiratory position. It is called a capacity because it is the sum of tidal volume and inspiratory reserve volume. The vital capacity is the maximal volume of air that a person can expire, regardless of the time required, after a maximal inspiration. In other words, it is the sum of the three volumes: tidal volume, inspiratory reserve volume and expiratory reserve volume.. A variant on this method is the forced vital capacity (FVC), in which the person takes a maximal inspiration and then exhales maximally as fast as possible. The apparatus that measures this also measures the volume expired after 1 second. This is the forced expiratory volume in 1 second or the FEV1 of which normal persons can expire approximately 80 percent of the FVC in 1 second. These measurements are useful diagnostic tools for patients with obstructive lung disorders in which they cannot expire a normal fraction of the FVC in 1 second because of their narrowed airways. On the contrary, patients with restrictive lung diseases are characterized by a reduced vital capacity but a normal FEV1/FVC ratio.

Based on the tabulated results above, we can see that there is a difference in the lung volume and capacities recorded between the male and female. Usually the lung volumes and capacities of males are larger than the lung volumes and capacities of females. Even when males and females are matched for height and weight, males have larger lungs than females. Because of this gender-dependent lung size difference, different normal tables must be used for males and females.

Also as noted on the tables above, the female subject’s lung volume results was considerably lower than normal. This could probably be that the subject had coughs and colds during experimentation that affected her breathing, and in turn affected the different lung volumes.

We can note in this experiment that a spirometer can only measure the different lung volumes and capacities mentioned above. The total lung capacity and residual volume cannot be measured directly with a spirometer. In the case of the residual volume, it is not possible for us to expire this since this volume of air remains in the lungs even after we forcibly expire. Meanwhile, since the total lung capacity is the sum of the four distinct lung volumes including here is the residual volume, it also cannot be measured.

ConclusionIn this experiment, we were able to define and measure the various lung volumes

and capacities with the use of a wet spirometer. However, the residual volume and the total lung capacity were not measured since the residual volume, which is one of the components of the total lung capacity, is the volume of air remaining in lungs even after forceful expiration. We also observed that the lung volumes and capacities between males and females vary. Males usually exhibit larger lung volumes and capacities than females because of the gender-dependent lung size difference.

References:Kisner, C. and Colby, L. (1996). Therapeutic Exercise Foundations and Techniques, 3rd ed. F. A. Davis Company.http://csm.jmu.edu/biology/danie2jc/respiration.htmhttp://www2.nau.edu/~daa/lecture/pft.htm