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PFT ACNP Student Cheat Sheet by

ACNP Student Pulmonary Rotation
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Pulmonary Function Tests

Pulmonary function tests (PFTs)
•Categ­ori­zation of different types of lung processes (restr­ictive versus obstructive)
•Asses­sment of disease severity (prognosis and preope­rative evaluation)
•Post-­tre­atment evaluation of lung function.
Evaluate PFT’s
1. When evaluating a PFTs think: •expir­atory flow • Lung volumes •Diffusion capacity •Response to bronchodilators
2. Look for all normals everything >80%. Most smokers have normal values.
3. Look for rest­rictive disease TLC< 80% . If TLC not known reflected in a propor­tional decrease in FEV1 and FVC (i.e., FEV1/FVC = 80% but FVC is< 80%).
4. If rest­rictive check DLCO for extra-­tho­racic or in intra-­tho­racic. If the decrease in DLCO is propor­tional to the decrease in TLC means the restri­ction is not due to parenc­hymal disease it is of extra-­tho­racic origin think of obesity and kyphosis. If the decrease in DLCO is dispro­por­tio­nately low compared to the decrease in TLC think of inters­titial lung disease.
5. Look for obst­ructive FEV1 and FEV1/FVC are low (<70%).
6. If obst­ruc­tive, check the TLC, DLCO, and reaction to beta2-­ago­nis­ts: Emphysema if the TLC is high but the DLCO is low (alveolar disease); minima­l-to-no response to beta2-­ago­nist. Asthma if the DLCO is normal, or there typically is a reaction to beta2-­ago­nist.
Obstru­ctive Disease
Over­­ex­p­a­nsion of lungs – loss of recoil. Redu­ction in AIRFLOW. FEV1/FVC Ratio is decreased (<70%). Diff­iculty exhaling, narrowed airways, bronch­­oc­o­n­st­­ric­­tion, mucus accumu­­la­tion. COPD [Emphy­­sema, Chronic bronch­­itis], Asthma.
Restri­ctive Disease
Redu­­ction in lung VOLUME. Difficulty taking air in from STIFF lung. Total lung capacity decreased (< 80%). ILD, scoliosis, obesity, PNA, Fibrosis, consol­­id­a­tion, Tumors due to both a decreased VC and RV.
 

Pulmonary Function Tests

TLC (total lung capacity: VC+RV) N=80–120%
The volume of air in the lungs after maximum inspir­­ation. High in obstru­­ctive (>120% hyperi­­nf­l­a­tio­n). Low in restri­­ctive (<80%, decreased lung volume).
FEV1 (forced expiratory volume) N=80–120%
Total volume of air able to exhale in the first second during maximal effort. Low (<80%) in obstru­­ct­ive. Normal to slightly low (<80%) in restri­­ctive (propo­­rt­ional to volume). Bron­ch­­odi­­lator response >12% and 200mL increased FEV1 (+asthma vs -COPD).
VC (vital capacity)
Volume of air expelled from the lungs during a maximum expira­­tion. Low in restri­­ct­ive (problem with lung dynamic, large airway is intact, so ILD).
FVC (forced vital capacity)
Total volume of air able to exhale for the total duration of the test during maximal effort. Low restri­­ct­ive (dec­reased expans­ion from fibrosis, tumor/­­ca­ncer, consol­­id­a­tion, heart failure with pulmonary edema, thick pleura, effusion, cardio­­me­galy, chest wall issues, muscle weakness).
FEV1­/FVC Ratio N=80%
Percentage of the FVC expired in one second (do the volumes, flow out of lung as expected). Low (<70%) in obst­r­uc­tive diseases (COPD or asthma). Norm­a­l/­high (>70%) in rest­r­ic­tive diseases (ILD, sarcoi­­dosis, asbest­­osis, CHF, MSK, neurom­­us­cular diseases + morbid obesity).
FRC (funct­­ional residual capacity)
Volume of air in the lungs after a normal expiration (inc­rease indicates hyperi­­nf­l­a­tion).
RV (residual volume) N=75–120%
Volume of air in the lungs at maximal expira­­tion. High in obstru­­ctive (dead space air, increase indicates air trappi­ng). Low in restri­­ctive.
TV (tidal volume)
Volume of air breathed in a and out of the lungs during quiet breathing.
DLCO (gas exchange) N=75–120%
Lung diffusion testing (ability of the body to absorb carbon monoxide from a single breath) is used to determine how well oxygen passes from the alveolar space (alveolar membrane permea­bility) of the lungs into the blood. Low in ILD, pulmonary vascular diseas­es, anemia, emphysema (loss of alveol­ar-­cap­illary units). Normal in chronic bronch­­itis, asthma (bronc­hoc­ons­tri­ction, but NO alveolar disease. Incr­­eased in problems that increase effective blood flow to the functional lung, such as heart failure, disease alveolar hemorr­hage, pulmonary infarc­­tion, and idiopathic pulmonary hemosi­derosis (IPH).
DLCO/VA
PERF­USION Diffusing capacity corrected for alveolar volume­­/H­c­t­-a­­dju­­sted.
 

PFTs for Specific Lung Diseases

Inte­rst­itial Lung Disease Restri­ctive
•Normal to increased FEV/FVC.
•Straight or slightly convex expiratory flow-v­olume loop tracing.
•Propo­rtional decrease in all lung volumes.
DLCO is reduced (due to thickening of the alveolar­ capillary interface) and is the 1st pulmonary parameter to change with disease progre­ssion
Asthma Obstru­ctive
•PFTs may be normal if no active disease.
•Decreased expiratory flow.
•Concave expiratory flow-v­olume loop tracing.
Sig­nif­icant response to beta2-agonist.
•Normal or increased TLC (due to hyperi­nfl­ation) and normal or reduced VC.
DLCO is normal.
Emph­ysema Obstru­ctive
•Decreased expiratory flow volume
•Concave expiratory flow-v­olume loop tracing.
Minimal response to beta2-­ago­nis­t­:< 12% improv­e­ment or < 200mL improv­ement in FEV1 or FVC.
Inc­reased TLC, reduced VC=hyp­eri­nfl­ation with trapped air.
DLCO is decreased (des­tru­ction of alveolar­ capillary interf­ace­--s­uggests emphysema) but early on maybe normal spirometry and lung volume
Chronic Bronch­itis Obstru­ctive
•Decreased expiratory flow volume
•Concave expiratory flow-v­olume loop tracing.
Minimal response to beta2-­ago­nis­t­:< 12% improv­e­ment or < 200mL improv­ement in FEV1 or FVC.
•Normal or only slight increase in TLC = normal or slightly reduced VC.
•DLCO is normal to slightly decreased, but it is not as low as in patients with emphysema.
•DLCO is to differ­entiate emphysema from chronic bronchitis and asthma.
Most cases of COPD have mixed physiology with components of both chronic bronchitis and emphysema.

FEV

Flow Volume Loops

The relati­onship between airflow rates compared with lung volumes.

Flow Loop

Test to Order

Smoker: age 40+
Spirometry with bronch­odi­lator q3-4yrs
Hx COPD
•Spiro­metry with bronch­odi­lator q 1-2 yrs
•Also DLCO and if FEV1 < 50% check blood gases
•Static lung volumes, looking for increased RV
Asthma: diagnosis
•Spiro­metry with challenge/ bronch­odi­lator q1yr
Daily peak flows
•Written plan in place
Allergic Rhinitis
Correlates w/Asthma so baseline for reactive airways with spirometry with methac­holine challenge and bronch­odi­lator
Exertional Dyspnea
Spirometry with dilators & methac­holine, DLCO, Pox, Exercise Testing
Chest Tightness
Spirometry with methac­holine and bronch­odi­lators
Chronic Cough
Spirometry with methac­holine, bronch­odi­lators, and inspir­atory flow loop
CAD (smoker and HF)
Spirometry with bronch­odi­lator
Recurrent PNA or Bronchitis
Spirometry with methac­holine and bronch­odi­lators
Neurom­uscular Disease
Spirometry with methac­holine and bronch­odi­lators, DLco testing, maximal respir­atory pressures
Occupa­tional exposures
Spirometry

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