Spirometry Flashcards
how is a spirometry done?
uses a spirometer to record changes in lung volume
results are plotted on a graph called a spirogram
what are the waves in a spirogram?
inspiration produces an upward waveform deflection
expiration produces a downward deflection
what is a power lab pneumotachometer?
an example of a spirometer
uses Flow rate to measure volume
air is breathed through a fine mesh to create a pressure difference across the mesh
this pressure difference is proportional to the flow rate
volume is then calculated as the integral of flow
what is tidal breathing?
At rest, we breathe in a certain amount of air and expire the same amount of air. This repeats for as long as we’re at rest, and since it mimics the ebb and flow of the tides
what is inspiratory reserve volume (IRV)?
This is the maximum volume above the tidal volume, that we can inspire into our lungs (approximately 3 L).
what is tidal volume (Vt)?
This is the volume we inspire and expire during restful breathing. Normally the rate of breathing is 10–12 respiratory cycles per minute, and in adults VT is approximately 0.5 L.
what is expiratory reserve volume (ERV)?
This is the maximum volume below the tidal volume, that we can expire from our lungs (approximately 1.5 L)
what is residual volume (RV)?
This is the volume of air remaining in the lungs after a full expiration (approximately 1.2 L). We can never empty the lungs completely
what is the inspiratory capacity?
This is all the air breathed in during a maximal inspiration at the end of a normal expiration. It is calculated by IRV + VT
what is the expiratory capacity (EC)?
This is all the air breathed out in a maximal expiration after a normal inspiration. It is calculated by VT + ERV
what is the functional residual capacity (FRC)?
This is the volume of air remaining in the lungs at the end of a normal expiration. It is calculated by ERV + RV [+]
what is vital capacity (VC)?
This is all the air that can be expired from a maximal inspiration. It is calculated by IRV + VT + ERV
what is total lung capacity (TLC)?
This is all the air that it is possible for the lungs to contain. It is calculated by IRV + VT + ERV + RV
what is forced vital capacity?
the maximum volume of air that a person can forcibly expire after a maximal inspiration
how can we calculate the forced expiratory volume in one second (FEV1)
we need both volume and time taken to transfer the volume
what is FEV1?
-volume of air exhaled in the first second using maximal expiratory effort
-it represents more than 80% of the exhaled volume in a healthy young adult
what should a health FEV1/FVC ratio be?
0.8 (80%) or more
what could a low FEV1/FVC ratio indicate?
that an individual may have obstructive lung disease
what are flow volume loops?
flow-volume loops are graphical representations of inspiratory and expiratory flows. They allow airflow to be measured for a specific lung volume. Flow-volume loops are normally plotted when a person expires as rapidly as possible following a maximal inspiration, but the same loop can be plotted for restful breathing or during exercise.
why do we use flow volume loops?
airflow is not the same at every lung volume. To measure this, we plot lung volume against airflow. Doing so produces a flow-volume loop, as breathing is a continuous act
what is an obstructive lung disease?
Individuals with an obstructive lung disease have difficulty breathing, due to narrowing of the airways or damage to the lung tissue. Asthma and chronic obstructive pulmonary disease (COPD) are two examples of obstructive lung diseases
what Is a restrictive lung disorder?
Individuals with restrictive lung disorders have difficulty inspiring enough air. When the cause is a lung disease, the lung tissue is stiffened. This can result from damage to the lung walls, which produces scarring and decreases lung compliance. An example is pulmonary fibrosis
how does a flow volume loop on someone with a restrictive disorder?
volume loop will be smaller but of a normal shape
what can affect pulmonary parameter differences between volunteers?
Age, sex, body size, health, and physical condition can all influence a person’s pulmonary parameters
what is the physiological significance of the FEV1/FVC ratio?
The ratio of FEV1 to FVC is an indication of an airway’s diameter. The higher the value, the faster air can flow through the airway. Therefore, the lower the resistance and the wider the airway
Compared to normal breathing, how are FEV1 values affected by simulating airways obstruction?
For the simulated airways obstruction activity, the expiratory rate is slower. Therefore, FEV1 will be a smaller fraction of the total expired volume than in normal breathing. The decrease in FEV1 will result in a significantly lower FEV1/FVC ratio
what is the criteria for acceptable spirometry?
free from artefacts
-cough
-glottis closure
-early termination or cut off
-effort not maximal throughout
-leak
-obstructive mouthpiece
good starts
-low extrapolated volume
satisfactory exhalation
-duration of at least 6s or a plateau in the volume time curve
between manoeuvre
Three acceptable spirograms should be obtained
The two largest values of FVC and FEV1 must be within 0.15 L of each other
