Equipment specifications and performance standards
| DLCO System | Specification | |
| Required | Recommended | |
| Rapid gas analyser systems | ||
| Analyser specification | ||
| 0–90% response time (see figure 2) | ≤150 ms | |
| Maximum nonlinearity | ±1% of full scale | |
| Accuracy | Within ±1% of full scale | |
| Interference from 5% carbon dioxide or 5% water vapour | ≤10 ppm error in [CO] | |
| Drift for carbon monoxide | ≤10 ppm over 30 s | |
| Drift for tracer gas | ≤0.5% of full scale over 30 s | |
| Flow accuracy | Within ±2% over the range of −10 to +10 L·s−1 | |
| Volume accuracy (3-L syringe check) | Within ±75 mL | |
| Barometric pressure sensor accuracy | Within ±2.5% | |
| Ability to perform a QA check (3-L syringe; ATP mode; inhaling ∼2 L test gas) | Calculate total volume (VA) of 3±0.3 L and DLCO of <0.5 mL·min−1·mmHg−1 or <0.166 mmol·min−1·kPa−1 | |
| Sample and store data with adequate resolution | Digitise at ≥100 Hz per channel with ≥14 bit resolution | Digitise at 1000 Hz |
| Monitor and report end-expiratory tracer gas and carbon monoxide concentrations (alert operator if washout is incomplete) | Implemented# | |
| Compensate for end-expiratory gas concentrations prior to test gas inhalation in the calculation of VA and DLCO | Implemented# | |
| Ensure proper alignment of gas concentration signals and the flow signal | Implemented# | |
| Measure anatomic dead-space using the Fowler method (see figure 6) | Implemented# | |
| Display a graph of gas concentration versus expired volume to confirm the point of dead-space washout and report the amount of manual adjustment if done (see figure 4) | Implemented# | |
| Measure VA using all of the tracer gas data from the entire manoeuvre in the mass balance equation | Implemented# | |
| Report the DLCO adjusted for the change in PAO2 due to barometric pressure | Implemented# | |
| Ability to input simulated digital test data and compute DLCO, VA, TLC, VD | Calculate values within 2% of actual values | |
| Report the DLCO adjusted for the change in PAO2 due to PACO2, if the carbon dioxide concentration signal is available | Implemented# | |
| Classical discrete sample systems | ||
| Analyser specification | ||
| Maximum nonlinearity | ±1% of full scale | |
| Accuracy | Within ±1% of full scale | |
| Interference from 5% carbon dioxide or 5% water vapour | ≤10 ppm error in [CO] | |
| Drift for carbon monoxide | ≤10 ppm over 30 s | |
| Drift for tracer gas | ≤0.5% of full scale over 30 s | |
| Flow accuracy | Within ±2% over the range of −10 to +10 L·s−1 | |
| Volume accuracy (3-L syringe check) | Within ±75 mL | |
| Ability to perform a QA check (3-L syringe; ATP mode; inhaling ∼2 L test gas) | Calculate total volume (VA) of 3±0.3 L and DLCO of <0.5 mL·min−1·mmHg−1 or <0.166 mmol·min−1·kPa−1 | |
DLCO: diffusing capacity of the lung for carbon monoxide; [CO]: carbon monoxide concentration; QA: quality assurance; ATP: ambient temperature, pressure and humidity; VA: alveolar volume; PAO2: alveolar oxygen tension; PACO2: alveolar carbon dioxide tension; TLC: total lung capacity; VD: dead-space volume. #: Implemented means that the manufacturer has implemented the designated functionality in the DLCO system.