PT  - JOURNAL ARTICLE
AU  - CL Phillips
AU  - R Simmul
AU  - AI Smith
AU  - N Berend
TI  - The effect of nitrous oxide on the measurement of single-breath transfer factor
AID  - 10.1183/09031936.97.10010200
DP  - 1997 Jan 01
TA  - European Respiratory Journal
PG  - 200--201
VI  - 10
IP  - 1
4099  - http://erj.ersjournals.com/content/10/1/200.short
4100  - http://erj.ersjournals.com/content/10/1/200.full
SO  - Eur Respir J1997 Jan 01; 10
AB  - One hour after a bone marrow biopsy and inhalation of Entonox gas (50% nitrous oxide (N2O) and 50% oxygen), a patient had a markedly reduced transfer factor of the lung for carbon monoxide (TL,CO). Three hours after Entonox, the patient had a normal TL,CO. Since carbon monoxide (CO) and N2O have similar spectral wavelengths, it was proposed that residual N2O in the lungs was interfering with the infra-red analysers used to detect CO concentrations. Experiments were performed to verify the "interference" effect and its duration. Five healthy volunteers performed serial triplicate TL,CO measurements over 3 h on two randomized days (Control vs N2O). The first triplicate TL,CO on each day served as a baseline measurement. Following the baseline measurement on the N2O day, each subject inhaled Entonox for 10 min. To serve as a control for the infrared effect, the identical protocol was repeated using a gas chromatography method for TL,CO determination. The infra-red method showed a marked reduction (> 50%) in TL,CO 30 min after N2O inhalation. This reduction did not return to baseline levels for at least 2 h. In comparison, the gas chromatography method showed no significant reduction in TL,CO. In a group of healthy nonsmoking subjects, N2O markedly affected the measurement of the transfer factor of the lungs for carbon monoxide using infra-red analysers. The time course over which the measurement was reduced was at least 2 h for a 10 min inhalation period. The effect was entirely due to a measurement error associated with infra-red technology.