RPFT cheat sheet

Pre-test assessment covers the indication, contraindications, current medications, recent respiratory illness, smoking status, and the patient's ability to perform forced maneuvers.

Withhold short-acting beta-agonists for 4–6 hours, long-acting beta-agonists for 12–24 hours, and short-acting anticholinergics for 6–8 hours unless testing is intended to assess current bronchodilator therapy.

Record age, sex, standing height without shoes, weight, and race/ethnicity; these variables are inputs to reference equations for predicted values and lower limits of normal.

Absolute contraindications include recent myocardial infarction, unstable angina, pneumothorax, active hemoptysis, and recent thoracic or abdominal surgery.

Relative contraindications include resting tachycardia, marked hypertension, recent respiratory infection, and inability to cooperate; document the risk-benefit decision.

Avoid vigorous exercise for at least 30 minutes and smoking for at least 1 hour before testing because either can alter airway caliber and test results.

Explain and demonstrate the forced maneuver; use a sitting position, nose clip, and tight mouth seal to prevent air leak.

Document supplemental oxygen use, recent hospitalization, and baseline dyspnea so results can be interpreted in clinical context.

Daily spirometer volume check: use a calibrated 3-L syringe; measured volume should be within ±3.5% of the syringe volume and the result logged.

Convert spirometry volumes from ATPS to BTPS using ambient temperature, barometric pressure, and water-vapor pressure.

Perform daily leak and occlusion checks; a leak falsely lowers measured volumes and flows and can invalidate results.

Calibrate DLCO gas analyzers daily with zero and span gases and verify linearity before patient testing.

Calibrate plethysmograph pressure transducers and box volume daily using known pressure and volume signals.

Record date, device, calibrator identity, expected value, measured value, and corrective action in the quality-control log.

Biological control testing by a healthy staff member helps detect system drift that syringe checks may not reveal; compare results with established limits.

Verify gas cylinder identity and expiration dates and confirm carbon monoxide and tracer gas concentrations before use.

An acceptable FVC trial has a rapid start, no cough in the first second, no glottic closure or leak, and a complete exhalation without early termination.

Back-extrapolated volume should be less than 5% of FVC or 150 mL, whichever is greater, indicating a satisfactory rapid start.

End-of-test criteria: a plateau with less than 25 mL change in the final second, or an exhalation lasting at least 6 seconds and generally no more than 15 seconds.

Reproducibility: the two largest FVC values and the two largest FEV1 values should agree within 150 mL; obtain at least three acceptable trials.

Bronchodilator response testing: repeat spirometry 10–15 minutes after a short-acting beta-agonist; a significant response is an increase in FEV1 or FVC of at least 12% and 200 mL.

Single-breath DLCO: exhale to residual volume, inhale test gas rapidly to total lung capacity, hold about 10 seconds, then exhale smoothly while discarding dead-space gas.

Plethysmography: with the shutter closed, the patient pants at about 1 Hz while box pressure changes are recorded to calculate thoracic gas volume.

MVV: the patient breathes maximally and rapidly for 12–15 seconds; the measured volume is extrapolated to liters per minute.

Obstruction is identified by an FEV1/FVC ratio below the lower limit of normal, or below 0.70 when the fixed criterion is used.

Restriction is suggested by reduced FVC with a normal or high FEV1/FVC ratio and is confirmed by total lung capacity below the lower limit of normal.

A mixed defect shows both a reduced FEV1/FVC ratio and a reduced total lung capacity.

In COPD, FEV1 percent predicted defines mild (>70%), moderate (60–69%), moderately severe (50–59%), severe (35–49%), and very severe (<35%) airflow limitation.

Bronchodilator responsiveness is an increase in FEV1 or FVC of at least 12% and at least 200 mL from baseline.

A low DLCO suggests emphysema, interstitial lung disease, pulmonary vascular disease, or anemia; an elevated DLCO may occur with polycythemia or pulmonary hemorrhage.

Use the lower limit of normal, typically the fifth percentile of the reference population, rather than a fixed percent predicted cutoff when reference equations permit.

Flow-volume loop: obstructive disease produces a concave expiratory limb, while restriction produces a narrow loop with a preserved shape.

Perform hand hygiene before and after patient contact and after handling mouthpieces or filters; wear gloves when contact with respiratory secretions is anticipated.

Use a disposable mouthpiece and a bacterial/viral filter for each patient; never reuse single-use items.

Clean and disinfect reusable spirometry and plethysmography components according to manufacturer instructions, including adequate contact time and drying before reuse.

For suspected tuberculosis, use a bacterial/viral filter, schedule testing in a separate room, and follow airborne infection isolation and local public health guidance.

For blood or body-fluid spills, absorb the material, disinfect with an EPA-registered agent, and discard waste according to facility policy.

Secure oxygen cylinders and keep them away from heat or open flames; prohibit smoking in testing areas because oxygen-enriched environments increase fire risk.

Dispose of sharps in puncture-resistant containers and biohazard waste in labeled containers according to facility policy.

Clean and disinfect surfaces between patients and follow posted infection-control policies for equipment and environmental cleaning.