2.330 Flashcards
What is PFT?
Pulmonary function tests (PFTs) are noninvasive tests that show how well the lungs are working. The tests measure lung volume, capacity, rates of flow, and gas exchange. This information can help the healthcare provider to diagnose and decide the treatment of certain lung disorders.
TLC
Total lung capacity: the volume in the lungs at maximal inflation, the sum of VC and RV.
TV
Tidal volume: that volume of air moved into or out of the lungs during quiet breathing (TV indicates a subdivision of the lung; when tidal volume is precisely measured, as in gas exchange calculation, the symbol TV or V is used.)
RV
Residual volume: the volume of air remaining in the lungs after a maximal exhalation
Can’t be measured by spirometery.
ERV
Expiratory reserve volume: the maximal volume of air that can be exhaled from the end-expiratory position
IRV
Inspiratory reserve volume: the maximal volume that can be inhaled from the end-inspiratory level
IC
IVC
Inspiratory vital capacity: the maximum volume of air inhaled from the point of maximum expiration
VC
Vital capacity: the volume of air breathed out after the deepest inhalation.
FRC
Functional residual capacity: the volume in the lungs at the end-expiratory position
TLC
3 equation
TLC= IRV + TV + ERV + RV
TLC = IC + FRC
TLC = CV+ RV
VC equation
VC= IRV + ERV
IC equation
IRV + TV
FRC equation
FRC = ERV + RV
There are 2 types of disorders that cause problems with air moving in and out of the lungs:
Obstructive
Restrictive
Obstructive diseases definition
This is when air has trouble flowing out of the lungs due to airway resistance. This causes a decreased flow of air.
Restrictive diseases definition
This is when the lung tissue and/or chest muscles can’t expand enough. This creates problems with air flow, mostly due to lower lung volumes.
Indication of PFT
5 and their meaning
➢Diagnose detect abnormalities in the lung function suggested by patient history, physical examination, or related diagnostic tests such as chest radiograph.
➢Quantify the severity or stage of a known lung disease.
➢Determine Follow the course of a patient’s disease and response to treatment.
➢Assess the risk for perioperative pulmonary complications.
➢Evaluate patients for the presence of pulmonary-related disabilities.
Clinical history and demographics
PFT depends on
5 points and their meaning
- Age - a factor in determining predicted values. Older persons have smaller predicted values.
- Height - also a factor in determining predicted values. Taller persons have larger predicted values.
a. For patients with spinal deformities, i.e. kyphoscoliosis, arm span is measured to derive the Measure from fingertip to fingertip.
b. Measure patient’s height without shoes.
c. To convert inches to centimeters, multiply by 2.54. - Gender/Sex - females have smaller lung volumes than males of equal age and height, therefore this is also a factor in calculating predicted values.
- Race/Ethnicity - A factor that can be used for calculating predicted values.
- Weight - not a major factor in calculating predicted values, but is a consideration in determining the presence of restrictive lung disease resulting from obesity.(Weight is used to estimate static volumes (FRC, RV, TLC, VTG).
There are four distinct phases to the FVC maneuver, as follows:
1) maximal inspiration
2) a ‘‘blast’’ of exhalation
3) continued complete exhalation to the end of test (EOT)
4) Must inspire maximally to close
the loop
Normal people exhale most of the air at the ………. around ……….. of …….
First second
80-85%
inhaled gas
FEV1% (FEV1/FVC) in obstruction and restriction
▪ Obstruction FEV1% < 70% (Check the reversibility)
▪ Reversible if FEV1 improve by at least 200 ml or 12%(post-pre/pre) which ever greater
➢FEV1% increase or normal with restriction
Obstruction and restriction depends on
What is the degrees of obstruction
R: Depends on TLC less than 80%
from 80-120% normal
Ob: depends on FEV1
Degree of Obstruction(ATS-ERS) depends on FEV1:
FEV1 >= 80% predicted — Mild
50% <= FEV1 < 80% predicted — Moderate
30% <= FEV1 < 50% predicted — Severe
FEV1 < 30% predicted — Very severe
