Table 2– Summary of component recommendations for inert gas washout system characteristics
Component Recommendation
Flow measurement Instantaneous flow accuracy within 5% across the range of flows encountered during clinical testing and volume accuracy within 3% using a precision calibration syringe.
Sample flow Ideally, all side-stream washout systems should correct for sample flow. If not performed or achievable, sample flow should be minimised: <20 mL·min1for paediatric and <40 mL·min−1for adult apparatus where gas sample point is proximal to flow metre.
Volume drift Accurate correction of volume drift is problematic due to difficulty separating technical and physiological components to observed drift. When an excessive drift, beyond the range usually observed, appears, attempts to identify physiological and/or technical causes (e.g.leaks) should be made as part of the routine quality control.
Gas analyser accuracy Linearity within 1% relative of full scale (e.g.0–80% is ±0.8% at 80% N2) to ensure appropriate assessment of starting concentration, and within 5% relative of any lower value (e.g.0.25% at 5% N2) down to 1/40 of the starting concentration. Initial assessment should incorporate both dry and humid conditions. Monitor gas analyser accuracy, stability and linearity annually using at least three reference points of gas concentration.
Gas analyser rise time 增长10 - 90%分析器recommen < 100毫秒的时间ded across all age groups.
Data sampling frequency Data sampling should ideally be≥100 Hz for both flow and inert gas concentration measurement.
Synchronisation of flow and gas signals Alignment accuracy within 10 ms or one sample (whichever is longer).
Equipment-related dead space Total equipment deadspace for young children should be <2 mL·kg−1bodyweight, and ideally <1 mL·kg−1in infants. Recommendations should be adhered to in older subjects, until further evidence is available. An upper limit of 70 mL should be adhered to for adults including hygiene filters if used.
Equipment-related resistance Should be minimised for both inspiration and expiration to avoid effects on breathing pattern and FRC during test.

  • The table is expanded with further explanation in section E2.6 in the online supplementary data. N2: nitrogen gas; FRC: functional residual capacity.