Understanding Spirometry - Normal, Obstructive vs Restrictive

in this video we're going to look at spirometry and look at the differences between normal obstructive pulmonary disease and also restrictive lung disease it is a good idea to recap the lung volumes and lung capacities before looking into this video so one way to monitor lung function is by using a lung function test such as a spirometry if we breathe in and out normally in this lung volume measurement device we can see our tidal volume which is typically five hundred mils or 0.5 liters the graph here the x-axis you can say is just the time and on the y-axis is the lung volume so going up the y-axis is inspiration the lung volume will increase when we inspire air in and going down the y-axis is expiration the lung volume will decrease when we breathe out obviously so now imagine taking a maximal deep breath in this is the inspiratory reserve volume also known as our RV and now imagine taking a normal breath or normal breaths and then having a maximal expiration this is your expiratory reserve volume or e RV and the air remaining in your lungs after the maximal expiration is the residual volume or RV you just always have that there using these lung volumes you can measure the lung capacities the lung capacities help define functioning lungs the vital on capacity refers to the maximum amount of air expired from a fully inflated lung this means it's the tidal volume tv+ the in spiritual reserve volume plus the expertise or volume the functional residual capacity which should not be mixed up with the residual volume represents the volume of air remaining in the lungs after expiration of a normal breath so it's residual volume plus expiratory reserve volume important is also the total lung capacity which is the sum of all the lung volumes in a typical adult male it's about six liters we will use a typical adult male total lung capacity as an example in the following scenarios so this first graph represents the a normal lung air coming in and carbon dioxide coming out the LV olai are inflating and deflating normally dynamic measurements of lung volumes and capacities have been used to help determine lung dysfunction the violet capacity is really important to remember again it's the tidal volume plus the in spiritual reserve volume plus the experience reserve volume the forced vital capacity is basically the same thing as the vital capacity but by definition it is the largest amount of air that can be expired after a maximal inspiratory effort so you breathe very deep in and then you breathe out fully the forced vital capacity is frequently measured clinically as an index of pulmonary function it gives useful information about the strength of the respiratory muscles and other aspects of pulmonary function let us draw it in a graph of a normal lung here you have the volume on the x-axis and flow through the lung on the y so a normal adult has a total lung capacity of six liters so here is the volume set here at six liters so from zero to six is a total lung capacity the forced vital capacity fvc is again the largest amount of air that can be expired after you take them the the maximal breath in the spirometry helps document and measure all this so imagine taking a deep breath in and then exhaling it out as forcefully as and as quickly as you can we can thus say this is your vital capacity or force develop capacity which in reality is your tidal volume plus your in spiritual reserve volume plus your expertise or volume thus the remaining air in our lungs after a maximal expiration if you remember is your residual volume we can look at the force of our capacity on a different graph by also introducing time when we introduce time we can calculate another component here we are looking at time on the x axis in seconds 1 2 3 4 5 6 7 8 9 10 and then on the y axis is the volume of air in the lungs in liters so 3 liters here and 6 liters remember 6 liters is the total lung capacity in an adult male here is the volume of air expired by a normal adult man during a forced expiration after a deep inspiration which again is your force bottle capacity and here it's about 5 liters and this again is your Forestville capacity thus again the air volume remaining in the lungs after maximal forced expiration is your residual volume now this is important concept see if you can follow the fraction of the vital capacity expired during the first second of a forced expiration is referred to as the forced expiratory volume or fev1 so from the the forced expiratory volume in the first second fev1 to the forced vital capacity FBC ratio can be calculated 4 liters / 5 liters which is 0.8 or 80% and again this is normal we will look at how this changes with certain diseases so let's look at what happens in COPD where we have gas trapping and we have obstruction of the Airways many changes are seen in lung volume and lung capacities in obstructive airway disease straight away we can see an increase in total lung capacity this is why it is common to see features of an enlarged chest in patients with COPD the tidal volume remains the same however the inspiratory reserve volume decreases the expiratory reserve volume increases and the residual volume increases as well thus if we were to calculate the lung capacities the vital capacity or also we can straight away say the force developed capacity is the same or maybe decreased the functional residual capacity is increased and the total lung capacity as mentioned altogether increases the reason behind these changes in lung volume and capacities are two main things firstly the reduction in air flow to the lungs due to obstruction and then you have what's called air trapping the air remains in the lungs at expiration as a consequence you get hyperinflation and consequently an increase in your functional residual capacity now let's see this using a spirometry and compare it to the normal on the left side again here we have the graph with volume in liters on the x-axis and flow of air through the lungs on the y-axis the forced vital capacity fvc again is the largest amount of air that can be expired after maximal inspiratory effort here in the dotted black line is normal forceful capacity normal full inspiration and then normal full expiration and this is obstructive lung disease the whole graph shifts to the left because you have an increase in residual volume and an increase in total lung capacity more than six liters your vital capacity or force about a capacity you can say remains the same but all up your total lung capacity has increased because of the increase in your residual volume or better because of the increase in your functional residual capacity you can see here the characteristic kink in in the obstructive lung disease patient during forced exploration this is because of the obstruction and also the flow decreases slightly because of the obstruction through the Airways let's see what the first second of a forced expiration is using the graph looking at time and volume on the y-axis again to compare this to normal force about capacity this is obstructive lung disease we can see that the forced vital capacity is the same or slightly decreased the forced expiratory volume in the first second has dropped significantly obstructive lung disease can be diagnosed when the ratio between fev1 and fvc is less than 0.7 or 70% and so in this example fev1 is about one liter and the fvc is about five liters and so 1/5 is obviously less than 0.7 or less than 70% and thus this is an example of a person who has obstructive lung disease finally let's look at restrictive lung disease these conditions include pneumoconiosis sarcoidosis amongst many other things in restrictive lung disease you have restriction like fibrosis in the lungs which impair lung compliance so the tidal volume remains the same but you have all this restriction in the lung all this fibrosis and so your inspiratory reserve volume is reduced and your expiratory reserve volume is reduced and your and your residual volume is reduced as well everything is reduced thus your forceful capacity is reduced the functional residual capacity is reduced and surprisingly your total on capacity is reduced the reason for this again is because of pulmonary fibrosis or changes in the lungs that lead to restriction and lung compliance you get stiffness restriction and because of this stiffness you have reduction in lung volumes and lung capacities let's look at your forced vital capacity using a graph again the dotted black line represents a normal force develop capacity which is the largest amount of air that can be expired after a maximal inspiratory effort here in brown is the pattern of force about capacity seen in restrictive lung disease as you can see it has shifted to the right the reason for this shift and change is because firstly your total lung capacity has reduced because of the restrictive lung changes the residual volume has reduced and so it is no surprise your final capacity or force develop capacity is reduced what about the forced expiratory volume in the first second well let's look at the other graph again at time on the x-axis so 1 2 3 4 5 6 7 8 9 10 seconds and lung volume on the Y which I get in a normal adult male goes up to 6 liters a normal person shoots up and the force of all capacity goes up to about 5 liters in restrictive here however in brown you can see that the forced vital capacity has reduced dramatically but the forced expiratory volume in one second is not as affected the forced expiratory volume in one second fev1 in restrictive lung disease is not as affected as seen in patients who have COPD or obstructive lung disease it can be normal actually in these patients who have restrictive lung disease or reduced depending on the severity and if the person has obstructive lung disease to the fev1 to fvc ratio is a useful tool in recognizing severity of airway disease and can help differentiate between COPD and restrictive lung disease in restrictive lung disease the FEV to fvc ratio is not as affected so for example in this scenario of restrictive lung disease the fev1 is about three liters and the forced vital capacity is about four liters so 3/4 is 0.75 or 75% and thus this can constitute restrictive lung disease rather than obstructive airway disease hope this video makes sense and hope it was helpful

Channel: Armando Hasudungan

Views: 1,263,862

Keywords: pulmonary function test, spirometry, lung function, pulmonary function, FEV/FVC, restrictive vs obstructive lung disease, difference between restrictive and obstructive, forced vital capacity, spirometry function, diagnosing COPD, spiromtery test, medicine

Id: YwcNbVnHNAo

Length: 14min 12sec (852 seconds)

Published: Mon Feb 19 2018