2680 PFT Review Flashcards
Pack years eqn
# packs/day x # years (Usually 20 cig/pack)
PFT process/ order of steps
1) spiro pre-bronchodilator
2) administer bronchodilator
3) DLCO
4) spiro post-bronchodilator
Most common symptom/complication during spirometry
Fainting
absolute contraindications for PF testing (pre-read pckg)
MI within 1 month
3 primary factors req’d for determining the predicted value (re: reference elms/normals)
Age, height, sex
Age when peak lung function reached
20-25 y.o.
How do lung mechanics and volumes change with age?
Lungs become more compliant while chest wall more rigid…
- RV & FRC increases w age (harder to fully exhale)
- VC decreases
- TLC remains same
- PEF decreases
- DLCO decreases
describe FVC test via spirometry and how to coach
Effort dependent test to measure volume forcefully exhaled from max inspiration
Steps: calibrate + enter pt data, nose clip on, mouth sealed on mouthpiece, good positioning; relaxed normal breaths, then on cue pt quickly breathes in until full then forcefully out until completely empty, then another breath in until full
coaching: “Purpose: how much volume you can exhale and how quickly you can do it (FVC, FEV1, PEF) = speed and volume
Big breath in and fast breath out as fast as you can; keep pushing even if you think you are empty; when i see that you’re empty, as big a breath as you can “
What type of patient may a SVC (slow vital capacity) be suitable for? What steps are generally preferred to do the test and why?
COPD Pt/emphysema bc forced vital capacity could collapse the airways during forced exhalation. SVC will give same volume but not the peak flows.
Steps:
Prefer to do a max expiration then max inspiration (VC) bc they will have a stronger drive to breathe when starting empty
critical value for a VC
<15ml/kg is resp concern; means their Vt will be way too small and won’t keep alveoli recruited
define the EPP
equal pressure point - Where pressure outside airway = pressure inside airway = critical point called equal pressure point (EPP)
-Further downstream from EPP, pressure outside airway can then exceed pressure inside airway
-lead to airway collapse (if lung tissue integrity is disrupted due to emphysema, obstructive lung disease)
-EPP is reached in everyone at some point, but it happens much easier/earlier with ‘floppy’ or weak airways
E.g. emphysema or COPD
normal proportion of lung volume exhaled in FEV1
75 - 85% = most people exhale this amount of lung volume in the 1st second of FORCED exhalation; represents large + medium airways +/- small airways
how to use FEV1/FVC to determine if obstruction is present
obstruction likely present if FEV1/FVC is <70%
what forced flowrate is independent of Pt effort?
FEF 25 - 75%; reflects smaller airways and is independent of Pt effort
Describe the ATS criteria for BEV (back extrapolated volume)
BEV should be =100ml or =5% of FVC whichever is greater; if Pt delays the start of the maneuver, they can “cheat” by leaking out some volume before the maneuver starts. We want to minimize this.
3 ways to meet the EFE (end of forced effort) ATS criteria
1) after 15 seconds of exhaling the test ends
2) Pt plateaus (< 25mL change in volume for) 1 second during exhalation
3) If Pt cannot achieve a plateau, FVC is within repeatability criteria or a larger than any previous FVC (VC needs to be within 150mL of a previous FVC, or a larger than a previous FVC = repeatability criteria)
describe ATS repeatability criteria for > 6 yrs old
If >6 years old,
-minimum 3 successful attempts with the top 2 FEV1 and FVC being within <150ml difference
FIVC ATS criteria
if FIVC > FVC, must be within 5% of FVC or within <100mL (whichever greater)
max # attempts to try according to ATS spirometry criteria
8
List the ATS criteria final reported values
Of the 3 successful tests, report Largest FVC Largest FEV1 Largest FEV1/FVC% -----> doesnt have to be from the same attempt! Largest PEF Largest FIVC
All other values come from best single test (e.g. FEF50%, FEF25-75%)
Best test = largest combined FEV1 + FVC
how to identify variable vs. fixed obstruction
variable FEF will not = FIF;
-intrathoracic: FEF < FIF
-extrathoracic: FEF > FIF
fixed FEF/FIF = 1 (they are the same)
List the bronchodilator given for spirometry and onset action
Ventolin (SABA) Salbutamol; onset action 5 - 15 mintues (so given in MDI after the pre-bronchodilator spiro, then do DLCO test ~10 minutes, then ready to do post-bronchodilator test)
describe repeatability criteria for < 6 yrs old
minimum 3 successful FEV1 and FVC, difference between top 2 FEV1 must be = 100mL or within 10% of largest FEV1 whichever is larger; and top 2 FVC must be = 100mL or within 10% of largest FVC whichever is larger
indications for spirometry (6 - overall)
pre-reading pckg
1) discover presence/absence of lung disease
2) assess amount of lung function impairment present in a known lung disease
3) assess effects of environmental or occupational exposure (hazardous work environments, smoking)
4) determine if therapy is beneficial to patient
5) determine surgical risk for thoracic, abdominal or lung resection procedures
6) evaluate impairments or disabilities for insurance/legal, social security/compensation, pulm rehab
what other information would be used to discover presence/absence of lung disease to indicate the need for spirometry
(pre-reading pckg)
S&S Hx: dyspnea, orthopnea, wheeze, cough, mucus production, chest pain
Physical exam: diminished br/s, chest wall abnormalities
Lab data: CXR, ABG
List the lung diseases that may be indication for spirometry when you want to assess the amount of lung function impairment
(pre-reading pckg)
pulm diseases: asthma, COPD, interstitial lung disease, cystic fibrosis
NMD: Guillain Barre
Cardiac: CHF
What type of therapies may indicate the need for spirometry? (pre-reading pckg)
bronchodilators, cardiac drugs, pulm rehabilitation, resection/reduction/transplant of lung
6 indications for determining lung volume (pre-reading pckg)
1) aid in diagnosis of restrictive lung disease
2) distinguish b/w obstruction or restrictive lung disease
3) determine severity of restrictive lung disease
4) assess response to therapy (from steroid/bronchodilator, lung reduction/resection/transplant, radiation/chemotherapy)
5) determine if pre-surgical pt have compromised lung fx
6) evaluate or determine level of disability
6 indications for DLCO
pre-reading pckg
1) determine if systemic disease is compromising pulm system
2) assess/quantify extent of parenchymal lung disease due to dust, drugs, organic agents
3) evaluate obstructive lung diseases + predict exercise induced arterial desaturation
4) evaluate CV diseases: pulm HTN, pulm edema, CHF, acute/recurrent pulmonary thromboembolism
5) evaluate polycythemia, L-R shunt, pulm hemorrhage
6) determine extent of severity associated with ILD
What 5 systemic diseases could be compromising the pulm system and indicate need for DLCO?
(pre-read pckg)
sarcoidosis, rheumatoid arthritis, sclerosis, systemic lupus erythematosus, mixed connective tissue disease
List the obstructive lung diseases that DLCO would help distinguish between
(pre-read pckg)
asthma, emphysema, chronic bronchitis
which obstructive diseases would DLCO help follow the progress of
(pre-read pckg)
CF, emphysema
conditions where suboptimal lung fx results are likely (pre-read pckg)
chest/abdominal pain from any cause, oral/facial pain exacerbated by mouthpiece, stress incontinence, dementia/confusional state
relative contraindications for PF testing (pre-read pckg)
poses relative danger or affects validity of performance:
- hemoptysis of unknown origin
- pneumothorax
- unstable CV status (angina, BP)
- recent MI
- recent PE
- thoracic/abdominal/cerebral aneurysms
- recent eye surgery
- acute disorders affecting test performance like nausea/vomiting
- recent thoracic/abdominal procedures
compare flow-volume graph to volume-time graphs
flow-volume loops can be used to identify disease process, Pt effort, errors like early stop or excessive BEV but NO indication of time
volume-time graphs show time, can identify errors such as leaks, and volume plateaus, but cant show disease process or Pt effort
describe the approach to detect testing errors for spirometry
1) on expiration see quick rise up
2) sharp PEF = strong effort and blasting out
3) linear rate downward or SLIGHT concave as flow decelerates is good
4) see zero flow is reached = complete emptying
5) big breath in until hit plateau for 1 sec
6) PEF50 should = PIF50
7) FVC should have same volume as FIVC
what is the shoulder/knee on the FV loop?
frequently seen in adolescents/young adults but is NOT abnormal for this population. It is due to airways pinching during the forced maneuver causing flow to flatten for a bit
describe location and phase of breath affected by upper airway obstruction
trachea, vocal cords, mainstem bronchi
fixed = affects both inspiration + expiration flows consistently (e.g. vocal cords stiff; FEF50% = FIF50%)
variable = inconsistent flow limitation during inspo or expo
distinguish variable extrathoracic obstruction vs. intrathoracic obstruction
extrathoracic = occurs in neck/trachea + amplified narrowing + lower flows on inspiration intrathoracic = occurs in bronchi within pleural cavity + amplified narrowing + lower flows on expiration
define vocal cord dysfunction
hard to diagnose; often appears as an asthma attack
- severe dyspnea due to vocal cord paradoxically closing on inspiration
- often affects younger high performing individuals
ATS criteria for responsiveness/reversibility + formula to calculate (to bronchodilator)
for post-bronchodilator, still need min 3 successful attempts with top 2 FVC and FEV1 within 150mL
responsive if:
pre + post FEV1 increases min 200mL or more AND at least 12% more
OR
pre + post FVC increases min 200mL or more AND at least 12% more
formula for % change= (pre - post) / pre
What medications should Pts STOP taking before coming in for PF testing? What medications should they KEEP taking before the test?
STOP: SABAs, SAMAs, LABAs, LAMAs
KEEP: ICS bc it takes days/weeks to get full anti-inflammatory effects, they’d have to stop for a full week
how long to refrain from taking a SABA vs. SAMA vs. LABA vs. LAMA before PFT?
SABA = 4 - 6hr SAMA = 12 hr LABA = 24 hr LAMA = 36 - 48hr
describe the approach to interpret spirometry results
1) scan Pt info to make sure reading results of the intended person
2) scan FV loops and vol-time graphs for errors
3) FEV1/FVC < 70%? If yes = obstructive likely, if low FEV1 and FVC but ratio is normal = restrictive likely
4) if FEV1/FVC, FEV1, and FVC values normal = normal lung function
5) compare any differences between phases
6) look at post-bronchodilator results for responsiveness
Purpose of lung volume tests
Helps identify all volumes and capacities not identified via spirometry = RV, FRC, TLC
+ helps create more specific interpretation (e.g. obstruction with airtrapping)
List the 4 lung volumes and 4 capacities measured with lung volume test
volumes = IRV, RV, Vt, ERV capacities = FRC, IC, VC, TLC
define IRV
max able to inspire on top of a normal tidal inspiration
define ERV
volume that can still be forcefully exhaled following a normal tidal exhalation; can help diagnose NMD
define RV
volume left in lungs that cannot be exhaled; normal ~ 20 - 35% of TLC
2 main types of lung volume tests
plethysmography, gas dilution: He Dilution or N2 Washout
what gas law does plethysmography/body box employ? What does each parameter represent?
Boyle’s Law: constant T, P1V1 = P2V2
P1 = pressure at mouth when shutter closes
P2 = pressure of box due to panting
V2 = volume of box due to panting
solve for V1 = FRC
Body box then also uses the Vt, ERV, and VC measured to calculate TLC
describe general steps of plethysmography
Pt sits in closed box for ~30 seconds to stabilize temp, begin relaxed breathing for at least 3 Vt to establish FRC, at END of Vt the RT closes the shutter and Pt begins to slowly pant, after 3 seconds shutter opens and Pt breathes fully out until empty / RV, then fully in until full / VC
difference between linked vs. unlinked pleth
linked is when VC is done right away after shutter opens = ideal
unlinked = after shutter opens, Pt takes a few normal breaths before doing a VC or they do the VC separately = done for Pts who have bad obstructions and need a break