Lung Volumes and Capacities
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Exercise 1: Lung Volumes and Capacities
A. TIDAL VOLUME (VT) AND MINUTE VENTILATION (MV)
Attach a labeled copy of your recording obtained during quiet breathing at a scale that shows the gradients of the inspiratory and the expiratory components of individual breaths.
From your recording and associated tabulated results record the respiratory rate and average tidal volume, and calculate minute volume (Minute Ventilation). List these values below, with their correct units.
Respiratory Rate= 19 breaths/minute
Tidal Volume = 0.68 L
Minute Volume= 12.96 l/min
The table of values obtained from this experiment shows values for Respiratory Rate, Tidal Volume, Minute Volume, Inspiratory Reserve Volume, Expiratory Reserve Volume and Residual Volume. Enter your data in column two of the table belowand state in column three whether each variable is obtained from your measured data or byestimation from population data.
Quantity
Observed Value
Measured or Estimated?
Respiratory Rate
19 breaths/min
Measured
Tidal Volume
0.68 L
Measured
Minute Volume
12.96 L/min
Measured
Inspiratory Reserve Volume
2.17 L
Measured
Expiratory Reserve Volume
0.45 L
Measured
Residual Volume
estimated
For any value/s that are estimated from population data, state why they cant be measured directly by spirometry.
The residual volume cannot be measured as the spirometry can only measure the volume of air that
Actively moves in and out of the lungs. The residual volume is the volume of air that is present in the lungs
After forceful expiration.
From the recording of quiet breathing determine the inspiratory and expiratory flow rates by graphical means from the printed image or by using the interpolation features of Lab Tutor. List the values below (with correct units).
Inspiratory Flow Rate – 60L/min
Expiratory Flow Rate faster than inspiratory 50L/min
Are the inspiratory and expiratory flow rates different? If so, how can you explain this?
They values are different. During inhalation the airways are larger and therefore provide little
Resistance to the flow. During expiration, the effect of decreasing volume in the lungs causes the airways
To go back to their original diameter.
Exercise 2: Pulmonary Function Tests: Forced Vital Capacity Test
A. MAXIMUM INSPIRATORY AND EXPIRATORY FLOW RATES
From the recording you obtained in this part of the practical calculate the maximum inspiratory and expiratory flow rates or obtain these from the tabulated data. List the values below (with correct units).
Maximum Inspiratory Flow (PIF) 173L/min
Maximum Expiratory Flow (PEF) 118L/min
Comment on any differences in these flow rates. How do they compare to the flow rates you determined during quiet breathing in Part A?
They are much larger. This could be due to several reasons.
Elasticity of lungs
Elasticity of chest wall
Effort motivation
Airway patency
Potential volume to expire
B. FEV1/FVC Ratio
Record the Value of the FEV1/FVC Ratio
0.29 FEV1/FVC x 100 = 29%
State in your own words what this ratio tells us about lung function.
The FEV1/FVC Ratio is the volume of air exhaled in the first second. It
gives us a diagnostic tool for obstructive and restrictive lung disease. For obstructive diseases, the
ratio expressed as a percentage form is less than 70%. For restrictive disease, this figure is greater
than 80%. A normal ratio should be between 70 and 75%
Were the results obtained on your three trials of the FVC test the same? Commentonthe size and likely reasons forany differences you observed.
The results were not the same. This is a test which requires optimal effort and cooperation on the patients