NIOSH SSS cheat sheet

Indications: detect airflow obstruction, confirm COPD/asthma diagnosis, grade severity, monitor disease progression or treatment response, assess preoperative pulmonary risk, evaluate dyspnea or chronic cough, and screen for impairment in occupational lung-disease surveillance.

Relative contraindications to forced expiratory maneuvers: recent myocardial infarction, thoracic, abdominal, or ocular surgery, pneumothorax, hemoptysis, thoracic or abdominal aneurysm, and unstable cardiovascular status.

Absolute contraindications include acute illness with impaired coordination and conditions where a forced vital capacity could cause harm, such as recent pneumothorax or acute myocardial infarction.

Defer testing when the participant has active pulmonary tuberculosis, hemoptysis of unknown origin, or acute respiratory infection with fever until resolved.

Bronchospasm after a recent bronchial challenge or methacholine test is a reason to delay testing; wait until airway tone has returned to baseline.

Pregnancy is not an absolute contraindication; forced maneuvers are generally acceptable but vigorous effort and Valsalva may warrant caution and clinical judgment.

Document the indication and any contraindication review before testing so the interpretation can be contextualized to the referral question.

Spirometry alone cannot diagnose asthma; a normal baseline does not rule out reversible airway disease, so bronchodilator response or challenge testing may be indicated.

ATS/ERS 2019 accuracy limits: volume accuracy within ±3.5% of reading or ±0.05 L, whichever is greater; flow accuracy within ±5% of reading or ±0.2 L/s, whichever is greater.

Calibration verification with a 3-L syringe is performed daily (at minimum at the start of each testing day) and after cleaning, disinfection, or any sensor or tubing change.

The 3-L syringe check must be within ±3.5% (approximately 2.895–3.105 L) at multiple flow rates (low, medium, high) to confirm linearity across flows.

Record each calibration check with date, time, syringe volume, measured values, percent error, and the initials of the person performing it; retain records per facility policy.

Test the spirometer for leaks before calibration verification; a leak causes low volume readings and invalidates the check.

Verify biological control or a healthy nonsmoking staff member periodically as a longitudinal check on system performance, tracking FEV1 and FVC trends over time.

Use a syringe with a known volume traceable to a national standard; syringes should be checked for accuracy and replaced if damaged.

Time-based checks: confirm the spirometer's clock and sample rate are adequate (volume-time sampling at least 10 Hz recommended for accurate FEV1).

Record age, sex, height (without shoes, to nearest 0.5 cm), and race/ethnicity because reference equations depend on these variables; use measured, not reported, height.

Ask about smoking status, current medications (especially bronchodilators), recent illness, and prior lung disease; note time since last bronchodilator dose.

Withhold short-acting beta-agonists for at least 4 hours, long-acting beta-agonists for 12 hours, and long-acting anticholinergics for 24 hours when bronchodilator response testing is planned.

Explain the maneuver and demonstrate it; use a chair with arms, nose clip, and a seated upright posture with feet flat and head slightly elevated.

Loose clothing should be loosened; dentures should be left in if they are well-fitting and aid mouth seal, but removed if they interfere with the seal.

Screen for contraindications before every test session and document the review; stop testing if the participant reports chest pain, dizziness, or severe dyspnea.

Have a plan for emergencies: oxygen, bronchodilators, and a means to summon help should be available; personnel should be trained in basic life support.

Avoid testing immediately after a large meal or vigorous exercise, which can affect effort and comfort.

Instruct: 'Take a deep breath, seal your lips around the mouthpiece, and blast out as hard and fast as you can, then keep going until I tell you to stop.'

Demonstrate the maneuver yourself and use enthusiastic, specific coaching during the effort; avoid vague encouragement such as 'breathe normally'.

The participant should be seated upright, with the mouthpiece held so the mouth is not obstructed and the head is in a neutral-to-slightly-extended position.

Encourage a maximal inhalation to total lung capacity before the forced exhalation; a submaximal inspiration underestimates FVC.

Continue coaching the exhalation for at least 6 seconds and until the volume-time curve shows a plateau (no volume change for 1 second) or the participant cannot continue.

At least three acceptable maneuvers should be attempted; up to eight may be performed, but stop when reproducibility criteria are met or the participant is fatigued.

Use a nose clip and check for leaks at the mouth; observe the participant for proper lip seal and correct technique during each trial.

For participants who cough or have a poor start, repeat the maneuver with clearer coaching rather than accepting a technically flawed effort.

Acceptable maneuver criteria: free of artifacts, no cough in the first second, no glottic closure or variable effort, no leak, and a satisfactory start with a rapid rise to peak flow.

End-of-test criteria: the volume-time curve shows a plateau (no change for at least 1 second) or the exhalation lasts at least 6 seconds, or the participant cannot continue.

Reproducibility: the two largest FVC values and the two largest FEV1 values should each agree within 0.150 L (150 mL).

A maneuver is acceptable if it meets start, end, and artifact criteria; the best FEV1 and best FVC may come from different acceptable maneuvers.

Back-extrapolated volume (BEV) should be less than 5% of FVC or 0.150 L, whichever is greater; a larger BEV indicates a hesitant start.

Peak expiratory flow should be achieved early; a delayed or rounded peak suggests submaximal effort or a poor start.

Report the largest FEV1 and largest FVC from acceptable maneuvers, and use the associated FEV1/FVC ratio from the same maneuver when possible; do not average values.

If reproducibility is not achieved after eight maneuvers, report the best values and note the limitation in the interpretation.

Use reference equations appropriate to the population and equipment; the Global Lung Function Initiative (GLI) equations are widely used and provide predicted values and lower limits of normal (LLN).

Obstruction is suggested by an FEV1/FVC ratio below the LLN (commonly <0.70 by fixed criterion or below the 5th percentile by GLI) with a reduced FEV1.

Restriction is suggested by a reduced FVC with a preserved or increased FEV1/FVC ratio; confirmation requires lung volumes (TLC), as spirometry alone cannot diagnose restriction.

Severity grading uses FEV1 percent predicted: mild ≥70%, moderate 60–69%, moderately severe 50–59%, severe 35–49%, and very severe <35%.

A bronchodilator response is defined as an increase in FEV1 or FVC of at least 0.200 L and 12% from baseline, meeting both criteria.

Compare results to predicted values and LLN rather than percent predicted alone; the LLN accounts for age, sex, height, and ethnicity-related variability.

A reduced FEV1 with a reduced FVC and a normal ratio may reflect mixed obstruction and restriction; clinical correlation and further testing are needed.

Interpretation should integrate the referral question, symptoms, smoking history, and test quality; a technically poor test should be interpreted with caution.

Record participant identifiers, date, time, technologist, spirometer identification, calibration check results, and all maneuver data (flow-volume and volume-time curves).

Report FVC, FEV1, FEV1/FVC ratio, FEF25–75%, and PEF with predicted values, LLN, and percent predicted; include the best values and the number of acceptable maneuvers.

Document test quality: number of maneuvers attempted, acceptability and reproducibility status, and any deviations from standard technique.

Store raw data and curves so results can be re-reviewed; retain records according to institutional and regulatory requirements (often at least 7 years or per local law).

Communicate results to the ordering clinician with a clear interpretation and any recommendations for follow-up testing, such as full pulmonary function tests or bronchodilator challenge.

Avoid over-interpreting isolated values; report the pattern (obstructive, restrictive, mixed, normal) and severity, and note limitations of the test.

Use standardized reporting templates and consistent units (liters, liters per second, percent predicted) to facilitate comparison over time.

Ensure confidentiality of health information and share results only with authorized parties per privacy regulations.

Perform hand hygiene before and after participant contact and between participants; use gloves when handling contaminated components.

Use a new disposable mouthpiece or filter for each participant; do not reuse single-use items between participants.

Clean and disinfect reusable spirometer components (mouthpieces, tubing, valves) according to manufacturer instructions and facility policy after each use or session.

Use an EPA-registered disinfectant with the appropriate contact time; follow the label for concentration and duration.

Handle bacterial/viral filters according to manufacturer guidance; filters reduce cross-contamination but do not replace cleaning of the spirometer.

Clean surfaces and chairs between participants, and ensure adequate ventilation in the testing area.

Follow standard precautions and transmission-based precautions; participants with known infectious respiratory illness should be rescheduled or tested with appropriate precautions.

Document cleaning and disinfection activities and maintain a log for quality assurance and audit purposes.