Summary consensus statement for simultaneous single-breath measurement of diffusing capacities of the lung for nitric oxide (DLNO) and carbon monoxide (DLCO) in healthy adults

Breath-hold time10 s is desired for better gas mixing
4–6 s is acceptable if using a single electrochemical NO cell that measures in the ppm range
Measured inspired NO concentration40–60 ppm, placed in the inspiratory bag ≤2 min before use
Measured inspired O2 concentrationClose to 21%
Measured expired O2 concentrationUsed to calculate PAO2 and θCO
1/θCO [16](0.0062·PAO2+1.16)·(ideal Hb÷measured Hb)
θNO [14, 29]4.5 mL NO·(mL blood·min·mmHg)−1
θNO/θCO ratioAverage 8.01 (male Hb 14.6 g·dL−1), 8.73 (female Hb 13.4 g·dL−1) at PAO2 of 100 mmHg#
DMCODMNO divided by 1.97#
Presentation of resultsReport DLNO, DLCO, KNO and KCO in absolute numbers and as % predicted from regression equations (at the appropriate breath-hold time), with the corresponding LLN, ULN and z-score (standardised residuals: number of standard deviations above or below the reference value)
Report alveolar volume in L BTPS and as TLC % pred
  • NO: nitric oxide; O2: oxygen; θCO (NO): specific conductance in the blood for carbon monoxide (NO) in mL·(mL blood·min·mmHg)−1; DMCO: alveolar–capillary membrane diffusing capacity for CO; PO2: oxygen tension; PAO2: alveolar oxygen tension; Hb: haemoglobin; DMNO: alveolar–capillary membrane diffusing capacity for NO; KNO: rate of change of NO from alveolar gas; KCO: rate of change of CO from alveolar gas; LLN: lower limit of normal; ULN: upper limit of normal; BTPS: body temperature and pressure, saturated (760 mmHg, 37°C, 100% humidity); TLC: total lung capacity. #: used in tables 1, 2 and 3 and the supplementary appendices.