welcome to another MedCam lecture

we’re going to talk about pulmonary function testing and this is going to be

over a couple of lectures we’re going to go over the introduction and give you a

little bit of a primer if you will on pulmonary function testing and then get

into more specifics so that you understand exactly what it is that’s

going on so the whole point of pulmonary function testing is to measure someone’s

lungs and find out whether or not they’re normal or abnormal and if it’s

abnormal find out why now this is kind of akin to getting tests on for instance

your heart with an echocardiogram or an EKG or we’re measuring the heart well

the problem is that the heart is measured on a proportion for instance

the ejection fraction is how much blood on each pump the heart can pump out and

normal is you know approximately 50% ejection fraction and we can measure the

chamber size and we can measure the valve and see if there’s regurgitation

the problem is in taking this issue and taking it over to the lungs is that the

lungs are more of an absolute and people’s lungs can be different based on

their height and other variables so we need to figure out exactly how we’re

gonna figure out what’s normal for somebody’s lung and that can be a little

tricky so are there four things that we need to take into consideration before

we determine what the absolute values are for somebody who can do a pulmonary

function test and the first one is height okay so height makes a difference

let me explain if you’ve got somebody here who is very tall versus somebody

who’s very short obviously a proportion of their body is going to have lungs in

them and the short person’s going to have smaller lungs and the bigger person

is going to have bigger lungs and so obviously the amount of air absolutely

they could be able to breathe in and out is going to be dependent on the size of

their lungs so obviously height has to come into it so that’s the first thing

we’re going to need to know and put into our equation to figure

about what the normal lung volume should be for somebody

number two is good to be age what happens as you hit the age of 25 which

is the best that you’re ever going to be in life in terms of your lung function

is lung function generally is going to decline even if someone has never smoked

and so as you get older the lung function is going to decline and

depending where you are along that axis that x-axis is going to determine where

somebody would be normally for any point along that curve and so age is the

second variable that goes into the equation the third variable is gender

okay male and female are going to have different sized lungs and so that needs

to be taken into consideration this is independent by the way of height so

gender is the third variable that goes into that and number four is race let me

give an example if you’ve got four for sake of argument here you’ve got a white

man and african-american black man in terms of where their proportions are

generally speaking the white man is gonna have his waist or his navel if you

will lower down then an african-american or the black man it should be higher so

given the same exact height black mens going to have smaller lungs than would

white man and similarly you could look at the other way that black men would

have longer legs for a specific height then a white man who would have shorter

legs and this has been looked at and researched in in the literature and so

as a result race also needs to play a role in terms of if you have someone

with a specific height they’re gonna have different sized lungs based on

proportionality okay so the purpose of all of this is to come up with a

customized value for each individual based

hundreds and thousands of patients and research and distributions and curves

and things of that nature so if you put a specific human being okay and the four

variables number one is height number two is age

number three is gender and number four is race and you take all of these

variables of a person and you put it into the computer and turn a crank

outcomes values X in this case and it’s that number that’ll tell you what the

normal distribution should be so there’s going to be a distribution of patients

and it will tell you what the 80% limit is that number there will tell you if

you are below this number okay actually it’ll be down on this side here 80% here

if you are below this number that means you are abnormal these are all normal

patients here okay and if you are below the 80% of predicted of that value then

that means you are abnormal let me tell it to a different way let’s say we plug

in those four values and we come up with a number for the forced vital capacity

and we’ll get into these numbers in a little bit and let’s say that the number

they come up with for the forced vital capacity for argument’s sake is three

point zero zero leaders that means that the 80th or the minimum 80th percent for

three liters or 80 percent of that predicted is good to be 2.4 liters and

so if you are below 2.4 liters that is considered abnormal another way of

saying it is that if your value is greater than 80% of the predicted then

you are normal and there’s no problems okay so the key I want you to get out of

this lecture is specifically the lungs are

a organ of the body that can change in size and you can get different values

for different people all with different distributions based on the four criteria

which is height number two is age number three is gender and number four is race

once you take an individual and you plug those numbers into the computer they

will give you values and it’s those values that you must base your abnormals

on this is different than looking at blood tests for the liver or looking at

an echocardiogram for the heart because in that situation there really you don’t

really have to take into consideration these values so in our next lecture

we’re going to talk about the lung itself and the pathophysiology but this

is kind of an introduction so join us for the next lecture thanks very much you

how do you know so much about everything? honest question