Lab 14 - Respiratory Physiology Flashcards
What is tidal volume (VT):
The volume breathed in each minute
- Normal breath
What is Expiratory Reserve Volume (ERV)
The maximal amount of air that can be exhaled from the lungs after a normal expiration.
- Amount of air that can be expired forcibly beyond the tidal volume
What is residual volume (RV)
The volume of gas left in the respiratory system after exhaling maximally.
- Air that cannot be expelled
What is Vital Capacity (VC):
Measure of the maximum volume of gas in the respiratory system that can be exchanged with each breath.
- Biggest possible breath
What is Total Lung Capacity ( TLC)
Measure of the volume of gas in the respiratory system at the end of a maximal inspiration.
What is major difference between volume and capacity in the respiratory system
A capacity is the sum of at least two volumes.
What is Forced Expired Volume ( FEV1)
Provides a measure of the resistance of the airways to flow.
What happens during normal resting respiration in the same breath
The volume of the exhaled gas exceeds that of the inhaled gas.
What is spirometry used for
Recording respiratory variables
Where does gas exchange between air and blood occur
In the alveolar air sacs
What is the efficiency of gas exchange dependent on
Ventilation; cyclical breathing movements alternately inflate and deflate the alveolar air sacs
What does inspiration do
Provides the alveoli with some fresh atmospheric ai
What does expiration do
Removes some of the stale air, which has reduced oxygen and increased carbon dioxide concentrations.
Why is spirometry becoming more important
- As respiratory dieseases are increasing world wide
- Spirometry is the method of choice for a fast and reliable screening of patients suspected of having Chronic Obstructive Pulmonary Disease (COPD).
What is COPD
- The 12th leading cause of death worldwide and the 5th leading cause in Western countries.
- Studies suggest COPD could climb to be the 3rd leading killer by 2020.
- Most COPD cases are completely avoidable; 85-90% of cases are caused by tobacco smoking.
How can important aspects of lung function be determined
By measuring airflow and the corresponding changes in lung volume
How was airflow measured in the past
By breathing into a bell spirometer, in which the level of a floating bell tank gave a measure of changes in lung volume. Flow, F, was then calculated from the slope (rate of change) of the volume, V:
What is the more convenient way too measure airflow
Directly with a pneumotachometer - breath speed measuring device
What was used in the lab
- Flow head - ‘ Lilly ‘ type that measures the difference in pressure either side of a mesh membrane with known resistance
- This resistance gives rise to a small pressure difference proportional to flow rate
- Two small plastic tubes transmit this pressure difference to the Spirometer Pod, where a transducer converts the pressure signal into a changing voltage
- The volume, V, is then calculated as the integral of flow:
What is a complication in the volume measurement caused by
The difference in air temperature between the Spirometer Pod (at ambient temperature) and the air exhaled from the lungs (at body temperature).
What does respiration consist of
- Repeated cycles of inspiration followed by expiration.
- During the respiratory cycle, a specific volume of air is drawn into and then expired from the lungs; this volume is the Tidal Volume (VT)
What happens in normal ventilation
The breathing frequency (ƒ) is approximately 15 respiratory cycles per minute.
How does breathing frequency vary
With the level of activity
What is the Expired Minute Volume ( VE)
- The product of ƒ and VT
- The amount of air exhaled in one minute of breathing.
- Also changes according to level of activity
What is residual volume ( RV)
The volume of air remaining in the lungs after a full expiration, residual
Why cant residual volume be measured by spirometry
A volunteer is unable to exhale any further (lungs may stick together!).
Terms and units
- Respiratory Rate -breaths / min (BPM)
- Expired Minute Volume - L/min
- Tidal Volume - L
- Inspiratory Reserve Volume - L
- Expiratory Reserve Volume - L
-Residual Volume- L - Inspiratory Capacity - L
- Expiratory Capacity - L
- Vital Capacity - L
- Functional Residual Capacity - L
Total Lung Capacity - L - Peak Inspiratory Flow - L/min
- Peak Expiratory Flow - L/min
- Forced Vital Capacity - L
Forced Expired Volume in one second- L
What is inspiratory reserve volume
Amount of air that can be inspired forcibly beyond the tidal volume
Comment on the differences between the experimental and predicted values for VC, FRC and TLC in the table
above. What could cause these differences, if any
VC, FRC and TLC values are higher than experimental
Differences are due to individual varitation.
Predicted values are based on large scale population studies and are averages. If the experimental values are consistenly lower than the predicted it may be due to poor tecnique on behalf of the volunteer i.e. insufficient inspiratory and/or expiratory effort
In quiet breathing, muscular effort is used mainly in inspiration, and expiration is largely passive, due to elastic
recoil of the lung. Can you relate this fact to the pattern of expiratory and inspiratory flow?
Normal pattern of breathing is efficient that it requires muscular effort for only a short time
- Inspiration is shorter to make it more efficient as it requires muscular effort
- Normal pattern of inspiration and expiration should shows a quiet period prior to each inspiration. Muscles must contract before inspiration can begin.
- There is a latency associated with this contraction
Why RV cannot be determined by ordinary spirometry
You never fully exhale the gas you have, RV is the amount of gas inside your body remaining
- Its the volume of air that remains in the lungs after a full expiration
Describe the physiological significance of the FEV1/FVC ratio?
Shows how much resistance there is of the airways to flow
Indication of airways diameter. The higher this value, the faster air can flow through the airway so the lower the resistance and the wider the airway.
Were your results for forced breathing consistent across all three trials? If not, why not?
It wasnt consistent but showed similar trends, inhaled different amounts = the amount exhaled was different
AND measuring same person - lung capacity should not change in a person during measurement period
Physiological events that occurred during this simulated asthma attack.
Harder to breathe in, more muscle force needed
Diameter of airways shrink due to swelling and inflammation. This decrease in diameter gives a sensation of extreme difficulty in inhalation and exhalation.
Physical activity becomes difficult because of this obstruction
What factors contribute to differences in pulmonary parameters between the volunteers
Age, sex, body size and health condition
What values have been affected by stimulated airway obstruction and why
An obstructed ( narrowed ) airway is unable to inhale or exhale as fast as those with normal diameter, due to increased resistance to flow. The total volume able to flow should be the same ( FVC unchanged ) but the rate at which air flows is slower leading to a lower ration.
