USES OF LONG SAMPLING PROBES IN RESPIRATORY MASS-SPECTROMETRY

The results of gas analysis by respiratory mass spectrometry using long (30 m) sampling probes were compared with those obtained using conventional short (1.3 m) probes, examining both static gas mixtures and respired gas at the mouth during maneuvers designed to make the concentrations of inspired marker gases change in a complex way within a breath. No important errors were introduced by using the long probes, both for estimates of gas tensions and for derived physiological variables. A slight reduction in signal for a water-soluble component was noted when sampling a moist gas mixture with a long probe, but this was of no practical significance.