Normal Values Usually come from:
They come from the statistical analysis of healty people
The physical characteristic that most influence pulmonary function include:
- Race or ethnic
- Weight or body surface area
Why Ethnecy influence on laboratory reference values?
Because of people height.
Some groups of people are small or tallest than normal average. forthermore their measurements must be according to them stature.
Most clinical laboratories cosider two standar deviations from the mean as the normal rage and these include:
95% of the healthy people.
- Values bellow 2SD (95%), in the lower limit of normal is consider ABNORMAL.
- Values ABOVE 2SD (95%), in the lower limit is concider ABNORMAL as well. Both LLN are know as 5% percentile
When performing PFT's 3 values are reported:
- % Predicted
On PFT, the Actual Value is:
The Acual Value is what the patient performed
predicted Value on PFT is:
What the the patient should have performed base on Age, Height, Sex, Weight and Ethnicity
PFT % predicted is:
A comparison of actual value to the predicted value.
In clinical medicine the 5% percentile is often difined as:
The LLN, because it represents the segment of helthy subjects farthest bellow the average.
Vital Capacity (VC) is:
VC is the volume of gas measured from slow, complete expiration after a maximun inspiration, whithout effort.
Vital Capacity consist of what lung volumes?
VC consist of three lung volumes:
- IRV= Inpiratory reserve volume.
- Vt= Tidal Volume
- ERV= Expiratory reserve volume.
Lung capacity happen when:
we combine two or more lung volumes
How we calculate RV?
By Subtructing FRC-ERV
ex: RV = FRC-ERV
How we calculate TLC?
BY adding IC+FRC.
ex: TLC= IC + FRC
What are the VC Criteria for Acceptability?
- End-expiratory volume varies by less than 100ml for three preceding breaths.
- Volume Plateau observed at maximun inspiration and expiration
- Two acceptable VC maneuvers should be obtained within 150ml
- The largest value from at least 3 acceptabe maneuvers should be reported
What's left in the lung after end expiration?
(Force Vital Cpacity)
What are the comparment of volumes of the lungs?
On VC criteria for acceptbility, how many manuever we should obtained , within what number and which one we report?
We should obtained two acceptable manuever within 150ml, and we report the LARGEST one out of those two.
On VC criteria for acceptability End Expiratory Volume varies by how many ml?, preciding for how many breaths?
On this criteria EEV varies less than 100ml, for three precing breaths.
On VC criteria for acceptability, when we have an acceptable plateau manuever?
Here we have an acceptable manuever when Plateau line picks and levels off. then we have an acceptable mauever.
What Pathology condition can decrease Lung Volume?
Any condition that causes lost of Lung Volume like:
- Lung Cancer
- Pulmonary Edema
- pulmonary Vascular Congestion
Why Obstructive Lung Disease can cause decrease VC?
Because of the gas trapping, resulting in elevated RV but normal TLC
What does it mean Reduced Chest Wall Excursion? and what condition causes?
Reduced Chest Wall Excursion means that the chest can NOT open mormally as a consecuense reduce Lung Volume or VC.
- Neuromuscular weakness
- Chest Wasll Deformity
- pain. All these contition will decrease VC
If Vital Capacity is less than 80% means?
What additional manuever is require when VC is reduced, and why?
If VC is reduced, we must perform FVC to identify obstruction or restriction.
On VC Significant/Pathology, Obstructive Lung Disease and Reduced Chest Wall Excursion will cause:
Decrease Vital Capacity
If Vital Capacity is less than 80% that is considered:
Maximun Volume of gas that can be exhale as forcefully and rapidly as possible after maximal isnpiration. This is what type of Lung Volume?
Forced Vital Capacity (FVC)
There are three key components to an FVC maneuver:
- Deep Breath
- Blast Out
- Meeting the end to test criteria, keep blowing
FVC criteria for acceptability are:
- Maximal exfort, no cough or glottic closure during the first second; no leak or obstruction to the mough piece.
- Good Start of the test (<5% of FVC or 150ml, whichever is greater)
- Tracing Shows 6 second of Exhalation or obvious Plateau (<0.025L for =>1s).
- Three acceptable Spirograms obtained ( Two largets FVC values within 150ml; two largest FEV1 values within 150ml).
- Report the largest FVC and the Largest FEV1 (even if they do not come from the same curve)
On FVC criteria for acceptability which value we report?
We report the largest FVC and the Largest FEV1 even if they do not come from the same curve.
After how many attempts we should STOP performing and FVC manuever?
After 8 attempts
In patients without Obstruction FVC and VC should be:
In what condition FVC is lower than VC?
In Obstructive condictions (FVC decresed while VC remaind the same)
What pathophysiology significant can reduced FVC?
- Mucus Plagging
- Bronchial Narrowing
- Chronic and Acute Asthma
- Trachea or main Bronchi Obsruction
Healthy adults should exhale their FVC within?
4 - 6 seconds
What type of patient require more than 20 seconds to exhale their FVC?
Patient with severe Obstruction Diseases like Emphysema, however >15 sec. will rarely change clinical decisions.
What decreases FVC?
Everithing that deacreases volume capacity. it can be restrictive or obstructive.
A reduction in FVC when going from sitting to supine has been shown to be a good indicator of:
In what condition FEV1 and FVC are decreased proportionately?
In Restrictive Diseases
IC and ERV are approxumately how much % of VC?
75% - 25%, respectively
Changes in IC and ERV, will usually parallel increase or decrease in the:
Spirometry is contraindicated in
Myocardial infraction within the last month.
condiction that can lead to suboptimal test like:
Chest, abdominal, facial, oral, pain, stress incontinence, dementia, confusion.
Forced Expiratory Volume (FEV1), may be reduced in:
- Poor patient effort
FEV1, in Obstructive disease may be reduced because of:
- Airway narrowing during forced expiration (Emphysema)
- Mucus secretion
- Inflamation (Asthma/Bronchitis)
- Large Airway Obstruction
FEV1 may be reduced in Restrictive Lung precesses like:
- Space ocupying lesions
- Neuromucular diseases
- Chest wall deformity
Is it true that in restrictive diseases the FEV1 and FVC are decresed proportionately?
yes, it's true.
The most widely used parameter, particularly for assesment of Airway Obstruction is;
What is FEF 25% - 75%?
Is the Maximun mid- expiratory flow
This maneuver is measured from a segment of the FVC that includes flow from medium and small airways.
Forced expiratory flow 25% - 75%
When Forced Expiratory Flow (FEF) 25% - 75% may help comfirm airway obstruction?
In the presence of a borderline value for FEV1/FVC
Is the flow that shows flow as the patient exhale from maximal inspiration (TLC) to maximal expiration (RV).
Flow Volume loop
Flow Volume Loop criteria for acceptability
- Rapid rise from maximal inspiration to PEF
- Maximal effort until flow retuns to zero baselin; no glottis closure or abrupt end of flow
- Maximal inspiratotory effort with return of volume to point of maximal inspiration
- At least 3 aceptable loops recored; superimposed or side by side loops should be repeatable, unless Bronchospasm occurs
- Report the FVL from the single best test maneuver (hieght sum of FEV1 and FVC)
Is the maximun flow obtained during a FVC maneuver...
Peak Expiratory Flow (PEF)
Peak Expiratory Flow is measured from?
Flow Volume Loop (FVL)
Minimun maneuver that a laboratory must perform to obtain PEF
3 minimun manuevers
The PEF must be within which numbers and which one should be reported?
PEF must be within 0.67 L/S (40 L/min)
and the largest PEF is reported
The hallmark of obstructive disease is the ratio of:
Any percentage =/<70% will be OBSTRUCTIVE.
Obstructive Lung Disease
Variable Extrathoracic Obstruction