The assessment of respiratory functions is mandatory in the diagnosis of lung diseases and related disorders. These functions are assessed by measuring the lung volumes and capacities. In the present experiment, we learnt the use and operation of BIOPAC airflow transducer for measuring the lung volumes. We understood the rationale behind the precautions taken while experimentation. We could successfully correlate the obtained results with the physiological conditions of the subjects of the study.
Experiment on Respiratory Volumes
Respiratory system is a vital system of human physiology. It is involved with the gaseous exchange wherein oxygen is inhaled and carbon dioxide is exhaled from the body. This gas exchange takes place in the lungs (smallest functional unit is called alveoli) and can be correlated with the body’s ability to detoxify itself from carbon dioxide (Shier, 2004, p.731).
Different phases of the respiratory cycle are presented by lung volumes and lung capacities. These volumes and capacities serve as standards with which the functioning of the lungs can be estimated. This assessment of respiratory function is useful in the diagnosis of lung diseases and related disorders (Wanger, 2005, p. 511). The lung volumes may vary depending on the sex, age, ethnicity and profession of a person (Needham, 1954, p. 313). In a study conducted on white and black subjects, the lung volumes of black subjects were found to be significantly lower than whites (Lapp, 1974, p. 185). Measurement of lung volumes can be accomplished using an instrument called spirometer and this technique is known as spirometry. Chart 1 presents the details of lung/respiratory volume measurements.
Respiratory volume description and measurements (Wanger, 2005, p. 511)
The present experiment aimed at the measurement of lung volumes and estimation of lung capacities. The experiment was conducted on two healthy individuals (coded as A and B) differing in their body-mass indices. The results were correlated to the physiological differences of the two subjects.
Materials and Methods
BIOPAC airflow transducer was used to study the respiratory volumes.
Step 1: Setting up the instrument
The BIOPAC unit was connected to the computer and the computer was turned ‘ON’. The BIOPAC data acquisition unit and airflow transducer were plugged in and turned ‘ON’. A clean bacteriological filter was placed at the end of BIOPAC calibration syringe. The calibration syringe and filter assembly were inserted to the airflow transducer through the ‘Inlet’. BIOPAC Student Lab Program was started by clicking on the computer screen. Lesson L2-Lung-1 was selected and ‘OK’ button was clicked. A filename was typed and the data file was saved on a hardware drive of the computer.
Step 2: Calibration of the instrument
The plunger of the calibration syringe was pulled out while the syringe was held in a stable and horizontal position parallel to the ground. ‘Calibrate’ button was pressed followed by ‘OK’. Five breathing cycles were conducted using the calibration syringe. ‘Yes’ button was clicked once the system was ready for second step of calibration. Once the five cycles were completed, the ‘End Calibration’ button was clicked.
Step 3: Recording the results
The air filter was inserted and breathing was done through ‘Inlet’ of the transducer. The airflow transducer was kept upright throughout the recording and the subject was not allowed to look at the computer screen while the recording was done. The code of each subject was written on the filter and mouth piece. The nose of the subject was plugged and lips were tightly sealing the inhalation and then exhalation. Again the subject was asked to take five normal breaths. As the subject proceeded for the first five normal breaths, the ‘Record’ button was pressed. Once the complete cycle was over, the ‘Stop’ button was clicked, recording was finished by clicking on ‘Done’.
Step 4: Analysis of the data
The saved data file was reviewed and CH-1 and CH-2 were observed. Average tidal volume was calculated by p-p values. I-beam cursor was used to measure IRV and ERV by recording the Delta values (Δ). Finally, vital capacity was measured through the I-beam cursor by observing the p-p value.
Once the measurements were over, the ‘Exit’ button was clicked.
This experiment was done the measure the lung volumes using BIOPAC airflow transducer. Two healthy subjects (A and B) were chosen for the conducting the experiments. A comparison of the pulmonary measurements of the two subjects is given in Table 1 and pulmonary capacities are given in Table 2. Figure 1 presents the snapshot of pulmonary data (for subject A) recorded in this experiment.
Figure 1. Snapshot of pulmonary data taken in the laboratory.
The tidal volume of subject A was 0.5 L and that of subject B was 0.55 L. The inspiratory and expiratory reserve volumes of both the subjects were similar. Vital capacity of B was higher that A.
Calculated pulmonary capacities
The inspiratory capacity of A was lower as compared to B. However, the functional residual capacities for both a and B were equal. The total lung capacity of B was considerably higher than that of A.
It is a well known fact that the vital capacity of the lungs of a person is directly proportional to his/her body surface area. We may interpret this statement as ‘obese people have higher vital capacity than skinny people’. During our experiment, we could estimate a correlation between the body surface areas of both the subjects with their vital capacities (VC of B was more).
Tidal volumes decrease in the restrictive lung diseases (like alveolitis). It is also dependant on the sex, age and ethnicity of a person (Lapp, 1974, p. 185). Both the subjects in the present study had different tidal volumes.
We learnt the basics of respiratory volumes and capacities in this experiment. We also learnt the working and operation of the BIOPAC airflow transducer. We could correlate our results of respiratory functions of the two subjects with their body masses.
Lapp, N. L., Amandus, H. E., Hall, R, & Morgan W. K. C. (1974). Lung volumes and flow rates in black and white subjects. Thorax. 29, 185-188.
Needham, C. D., Rogan, M. C. & McDonald, I. (1954). Normal standards for lung volumes, intrapulmonary gas mixing, and maximum breathing capacity. Thorax. 9, 313-325.
Shier, D., Butler, J. & Lewis, R. (2004). Holes Human Anatomy and Physiology. New York: Mc Graw Hill.
Wanger, J., Clausen, J. L., Coates, A., Pedersen, O. F., Brusasco, V., Burgos, F., Casaburi, R., Crapo, R., Enright, P., van der Grinten, C. P. M., Gustafsson, P., Hankinson, J., Jensen, R., Johnson, D., MacIntyre, N. McKay, R., Miller, M. R., Navajas, D., Pellegrino, R. & Viegi, G. Standardization of the measurement of lung volumes. European Respiratory Journal. 26, 511-522.