Free RPFT Exam Flashcards

The device must be within +/-2.5% when tested with a 3-L syringe using the ISO 26782 profiles. The syringe itself is allowed +/-0.5%, so the combined daily verification tolerance you apply is +/-3%. On a 3-L syringe that means 2.91 to 3.09 L. The older +/-3% device figure came from the 2005 standard.

Accuracy must be +/-0.015 L or +/-0.5% of full scale, verified by the manufacturer on delivery and at the recommended intervals. The syringe must sit at room temperature. Holding the barrel to steady it warms the trapped gas, expands it, and adds measurement error, so support the syringe rather than wrapping your hand around it.

They remove water vapor, and CO2 absorbers remove carbon dioxide, before sample gas reaches the analyzer. Infrared and thermal conductivity analyzers read water vapor and CO2 as interfering gases, so a saturated or CO2-rich sample gives a falsely shifted reading. Exhausted absorber (Drierite turns from blue to pink) is a routine cause of analyzer drift.

Use arm span or ulnar length and convert to an estimated standing height. Reference equations are driven by height, so using a compressed standing height would inflate the percent predicted and hide a restrictive defect. Record on the report that height was estimated and by which method, because it changes every predicted value.

Before calibration, before every calibration verification, and before patient tests, with the spirometer blocked so no gas moves. If flow varies during the procedure or the zero level has shifted noticeably, repeat it. A drifting zero adds a false baseline flow that accumulates into volume error across the whole maneuver.

A linearity or flow-dependence problem rather than a simple gain error. Suspect a partially occluded or damaged flow sensor, debris or condensate on a screen, or a filter that was fitted for verification but not for patient testing. This is exactly why the daily check cycles the syringe at least three times across a range of flows instead of once.

A leak. Expired N2 should fall smoothly breath by breath. A sudden large rise, or any change in the inspired tracer concentration, means room air is entering the circuit, usually at the mouthpiece seal, the nose clip, or a valve, and the 2023 ERS/ATS standard says to stop the test. The leak dilutes the washout and falsely raises the calculated FRC. Reseal and wait at least twice the washout time before repeating.

A system leak is admitting room air, which dilutes the helium further. Because FRC is calculated from how far the helium was diluted, the extra dilution makes FRC read falsely high. Contrast this with the classic dilution error in obstruction, where poorly ventilated units are never reached and FRC reads falsely low.

One-point calibration sets the offset using a single known gas or buffer. Two-point calibration also sets the slope, using a second value at the other end of the range. Passing one point but failing two means the electrode responds but its gain has drifted, which typically signals an aging membrane or depleted electrolyte rather than a simple zero shift.

Thermal disequilibrium. Body heat and warm expired gas raise cabin temperature until the box is equilibrated with the door closed, and the resulting pressure drift corrupts the volume signal. Allow the stabilization period with the patient seated and the door shut, and confirm a stable end-expiratory level over several breaths before closing the shutter.

A two-wavelength pulse oximeter cannot distinguish carboxyhemoglobin from oxyhemoglobin, so COHb is counted as saturated and SpO2 reads falsely high. Only multi-wavelength CO-oximetry (hemoximetry) on a blood sample reports the true oxyhemoglobin fraction along with COHb and methemoglobin.

Run a serial dilution check: deliver known fractions of the test gas, plot analyzer output against the expected concentration, and look for departure from a straight line. The 2017 ERS/ATS DLCO standard calls for this linearity check monthly, separately from the daily zero and span. Nonlinearity biases DLCO in a concentration-dependent way, so an analyzer can pass a single-point check and still misreport patients.

Use a 3-L syringe cycled at least three times to give flows spanning roughly 0.5 to 12 L/s, which corresponds to 3-L injection times of 0.5 to 6 seconds. The measured volume at each flow must be within +/-3%, for both inspiration and expiration on flow-based devices. Verification is required daily even on factory-calibrated devices that cannot be field-adjusted.

A syringe tests only volume accuracy on a rigid, dry, room-temperature signal. A biological control is a healthy repeat subject with known stable values, so it also exercises BTPS correction, software, reference equation setup, sensor hygiene, and operator technique end to end. Track the subject's results on a chart and investigate when a value falls outside the established range.

It verifies the body plethysmograph, not the DLCO system. A rigid container of known volume (ideally two sizes) packed with copper wool keeps the gas isothermal; pumped at 0.5 to 1 Hz to mimic panting, the box must recover the known volume, corrected to ambient saturated conditions rather than BTPS. Check it monthly, after software updates, and when a problem is suspected (2023 ERS/ATS). DLCO systems are checked with a 3-L syringe (VA 3 +/- 0.3 L, DLCO under 0.5) or a DLCO simulator instead.

Inspect it daily for a displaced piston stop and for smooth travel with no sticking or catching, and perform a leak test monthly. A syringe that no longer delivers a true 3 L, or that leaks past the seal, will quietly certify a spirometer as accurate when it is not, so the reference standard has to be verified as well as the device.

The same filter must be in place during recalibration and verification. Filters add resistance and a small dead space, so verifying without one certifies a configuration you never actually use on patients. Filters are the main engineering control against cross-contamination in the PFT lab, alongside hand hygiene, single-patient mouthpieces, and surface disinfection between subjects.

When diaphragm weakness is suspected: neuromuscular disease, phrenic nerve injury, or unexplained orthopnea. Lying flat lets the abdominal contents push against a weak diaphragm. Healthy adults lose under about 10% of VC supine. A fall greater than 25% is the usual threshold for diaphragm dysfunction (about 79% sensitivity and 90% specificity); unilateral weakness typically drops VC a further 10 to 30% and bilateral weakness 30 to 50%.

Body plethysmography. It measures all compressible thoracic gas, including gas in bullae and poorly communicating units, because it works from Boyle's law rather than from washing a tracer in or out. Gas dilution and washout only reach ventilated lung, so they systematically underestimate FRC and TLC in severe obstruction.

Methacholine acts directly by stimulating muscarinic receptors on smooth muscle. Exercise, eucapnic voluntary hyperventilation, and mannitol act indirectly by provoking mediator release from airway cells. Indirect challenges are less sensitive but more specific for active airway inflammation, so they map better onto a clinical asthma diagnosis.

When you need to separate weak respiratory muscles from stiff lungs or chest wall, as in suspected neuromuscular disease, unexplained restriction with a normal TLC pattern, or before decisions about ventilatory support. MIP reflects inspiratory strength, MEP expiratory strength, and cough peak flow the ability to clear secretions.

The 6MWT is self-paced, so the patient sets an intensity they can sustain and it reflects functional capacity in daily life. The shuttle walk is externally paced by an audio signal that speeds up in stages, so it pushes toward a symptom-limited maximum and behaves more like a graded exercise test. Neither replaces a monitored cardiopulmonary exercise test when you need to explain why exercise is limited.

Residual drug blunts the measured response and can turn a truly responsive patient into a negative result, or push a methacholine PC20 falsely high. Withholding intervals follow the drug's duration of action, so short-acting agents need the shortest hold and long-acting agents the longest. Always record what the patient actually took and when, because that determines whether the study is interpretable.

Chest pain suggestive of ischemia or ischemic ECG changes; complex ectopy or second- or third-degree heart block; a systolic pressure fall of more than 20 mmHg from the highest value reached; hypertension above 250 systolic or 120 diastolic; SpO2 of 80% or less with signs of severe hypoxemia; sudden pallor, loss of coordination, dizziness, confusion, or signs of respiratory failure (ATS/ACCP CPET statement). Fatigue and dyspnea are normal end points, not termination criteria.

BEV is the volume already exhaled before the extrapolated true start of the forced effort, and it quantifies a hesitant or slow start. It must be no more than 5% of the FVC or 0.100 L, whichever is greater. An excessive BEV means the timing zero is wrong, which inflates FEV1 because the first, fastest part of the breath is not counted against the clock.

First, a plateau: less than 0.025 L change in volume over at least 1 second. Second, the patient has tried to exhale for at least 15 seconds. Third, the measured FVC is within the repeatability tolerance of, or exceeds, the largest FVC already observed in that testing set, which covers patients who cannot sustain exhalation. The 2019 standard renamed the old end-of-test criteria to EOFE.

The patient must inhale at least 90% of the largest VC from the same session, fast enough that 85% of the test gas is in within 4 seconds, and the calculated breath-hold must last 10 seconds plus or minus 2 (8 to 12 s) with no Valsalva or Mueller effort. A shallower inspiration, between 85 and 90% of VC, can still be accepted only when its alveolar volume matches the largest VA from acceptable trials to within 200 mL or 5%, whichever is larger.

Sample collection must be completed within 4 seconds of the start of exhalation; on rapid gas analyzer systems the virtual sample starts once dead-space washout is complete. Allow at least 4 minutes between trials on classical systems so test gas clears the lungs, or on RGA systems until end-exhalation tracer is at most 2% of the test gas concentration. Retained CO from the prior trial lowers the next DLCO.

When the end-tidal tracer gas concentration falls below one fortieth of its starting concentration, roughly 2% N2, for at least three consecutive tidal breaths. The patient then performs a linked maneuver, an inspiratory capacity followed by an expiratory vital capacity, so RV and TLC are derived from the same continuous recording as FRC rather than from a separate spirometry session.

Support the cheeks and floor of the mouth with both hands, breathe quietly until a stable end-expiratory level is reached (usually 3 to 10 breaths), then close the shutter and pant at 0.5 to 1.0 Hz, that is 30 to 60 per minute. Up to about 1.5 Hz (90 per minute) is acceptable when spirometry shows no or minimal obstruction. Unsupported cheeks act as a compliant chamber and cause overestimation.

A flat, straight hard-surfaced course of fixed length with turnaround markers, the patient walking alone at their own pace while the technologist stays put and uses only scripted encouragement at set intervals, and recording of baseline and end SpO2, heart rate, and Borg dyspnea and fatigue scores. Walking beside or ahead of the patient paces them and invalidates comparison with prior tests.

Before: adequate collateral circulation, traditionally with a modified Allen test, plus anticoagulant status and site condition. Use a dry heparinized syringe, because liquid heparin dilutes the sample and lowers PCO2. After: apply firm direct pressure for several minutes, longer if the patient is anticoagulated, expel air bubbles immediately, and analyze promptly or ice the sample.

The difference between the largest and next largest FVC must be no more than 0.150 L, and the same for FEV1. An adequate test needs a minimum of three acceptable maneuvers with two of them meeting repeatability. Report the largest FVC, largest FEV1, and largest peak flow, taken from any acceptable maneuvers, not necessarily the same one.

Repeatability loosens to 0.100 L or 10% of the highest value, whichever is greater, for both FVC and FEV1. Cough and glottic closure are judged over the first 0.75 seconds rather than the first second, because FEV0.75 is often the reportable index when a preschool child cannot sustain a full second of forced expiration.

No. The 2017 criterion is two acceptable measurements within 2 mL/min/mmHg (0.67 mmol/min/kPa) of each other, an absolute limit only. This pair differs by 3.0 and fails. The 2005 alternative of 3 units or 10% was dropped, so applying a percentage rule would wrongly pass these and report an average built from discordant data.

At least three acceptable TGV (FRCpleth) values agreeing within 5%, calculated as the difference between the highest and lowest divided by the mean. Report the average of those values, not the best single effort. Airway resistance must not be measured during the same maneuver as lung volumes, because the two require different panting frequencies.

Aim for at least two technically acceptable trials whose FRC values agree within 10% of their mean (highest minus lowest, divided by the mean, no more than 0.10), and report the mean. The tolerance is wider than the 5% used for plethysmography because a steady tidal breathing pattern is harder to sustain than a short panting maneuver. Wait at least twice the washout or dilution time between attempts.

After the forced expiration the patient should inhale rapidly back to full inflation. This inspiratory limb is strongly recommended, though its absence alone does not make the maneuver unacceptable. If the FIVC exceeds the FVC, FIVC minus FVC must be no more than 0.100 L or 5% of FVC, whichever is greater. A larger gap means the patient did not start the forced expiration from full inflation, so the FVC and FEV1 are understated.

A cough in the first second makes FEV1 unacceptable but leaves FVC usable. Glottic closure in the first second invalidates both FEV1 and FVC. Glottic closure, early inspiration, or coming off the mouthpiece after the first second invalidates FVC but leaves FEV1 usable. Since 2019, FEV1 and FVC are graded separately, so you may report a graded FVC from a maneuver whose FEV1 you rejected, and the reverse.

GLI-2012 are all-age multi-ethnic spirometry reference equations built with the LMS method, giving a predicted value and a z-score for each index. The LLN is the fifth percentile, which is a z-score of about -1.645. Values above that z-score are normal. Because the LLN adjusts for age, height, and sex, it avoids the age bias that a flat 80% of predicted introduces.

Body temperature, ambient pressure, saturated with water vapor. Gas leaving the lungs cools and loses water vapor in the circuit, so it occupies less volume at the sensor than it did in the chest. The BTPS factor scales measured volume back to conditions inside the patient. Skipping it, or using a wrong ambient temperature, systematically understates every reported volume and flow.

Consider adjusting for hemoglobin, carboxyhemoglobin, and altitude or inspired oxygen tension, since each changes how much CO the blood can take up independently of the alveolar-capillary membrane. KCO is DLCO divided by alveolar volume, the transfer coefficient. Reporting KCO alongside DLCO separates a small accessible lung from genuinely impaired gas transfer per unit of lung.

Take post-bronchodilator minus pre-bronchodilator, divide by the predicted value, and multiply by 100. A change greater than 10% of predicted in FEV1 or FVC is a significant response. Expressing the change against predicted rather than against the patient's own baseline removes the bias that made the older 12% plus 200 mL rule easier to meet in small people with low baselines.

About 1.7 L of trapped or poorly communicating gas. Plethysmography measures all compressible thoracic gas while dilution only reaches units the tracer can enter, so the difference estimates trapped volume and is a hallmark of severe obstruction and bullous disease. A large gap validates both numbers rather than invalidating either; report the method with every volume.

The measurement method, the equipment, and the reference equation set, and ideally the operator and time of day. Changing from dilution to plethysmography, or from one reference set to another, shifts values on its own. A real change must also exceed the combined biological and measurement variability for that index, which is wider for DLCO than for FEV1.

They are suspect and cannot be released as valid. Document the failure, correct or recalibrate the device, repeat the verification, and recall affected patients for retesting. This is why the quality control log must record findings, repairs, adjustments, and software updates with dates: it defines exactly which window of patient data is in question.

FEV1 divided by the largest vital capacity below the fifth percentile, that is below its LLN. A fixed ratio such as 0.70 is not the recommended criterion: it over-diagnoses obstruction in older adults, whose ratio falls normally with age, and under-diagnoses it in young adults. Confirm hyperinflation or air trapping with lung volumes rather than inferring it from the ratio.

Not from spirometry alone; that pattern is only possible restriction. Restriction requires TLC below the fifth percentile with a normal FEV1/VC. When both FEV1/VC and TLC fall below the fifth percentile the pattern is mixed. A low FVC with normal TLC is instead the non-specific pattern, often seen with poor effort, obesity, or air trapping.

Grade by z-score, applied to the relevant index. Above -1.645 is normal, -1.65 to -2.5 is mild, -2.51 to -4.0 is moderate, and below -4.1 is severe (the standard's own cut points). This replaced the five-level scheme built on percent-predicted FEV1 cut points of 70, 60, 50, and 35 percent, which graded the same physiology differently at different ages.

Impaired gas transfer without a ventilatory defect. Consider pulmonary vascular disease such as pulmonary hypertension or chronic thromboembolic disease, early interstitial lung disease, or early emphysema before airflow obstruction appears. Also rule out the non-pulmonary causes first: anemia lowers DLCO and a raised carboxyhemoglobin level lowers it too, and both are correctable on the report.