Jad. Spencer et al., MATERNAL-FETAL ARGON TRANSFER USING SKIN-SURFACE MASS-SPECTROMETRY DURING HUMAN LABOR, Journal of maternal-fetal investigation, 4(4), 1994, pp. 215-219
Objective: Feasibility study of a potential means to assess placental
function by measurement of maternal-fetal inert gas transfer during hu
man labor using skin-surface mass spectrometry. Methods: Skin-surface
mass spectrometer probes were attached to the maternal forearm and fet
al scalp (after rupture of the membranes) of six women during labor. M
easurements of maternal and fetal argon were made before, during, and
after the inhalation of 75% argon in oxygen for 2 min. Results: Argon
was first measured from the maternal skin after a median time of 44.5
sec (range 33.0-45.8) and the level rose steadily to reach a median pe
ak partial pressure of 94.3 mm Hg (range 68.4-103.7) at a median time
of 160 sec (range 138.3-175.0). The maternal level then fell steadily
at an exponential rate. Argon was first measured from the fetal scalp
after a median interval of 90 sec (range 60.0-123.3) and rose more slo
wly to a median peak partial pressure of 24.3 mm Hg (range 17.0-38.9)
at a median time of 288.5 sec (range 256-390). The median (range) feta
l/maternal (F/M) ratio of skin-surface argon peak values was 0.26 (0.2
2-0.39) and showed good reproducibility within each case. The overall
coefficient of variation of mean values from the six women was 9%. Mat
ernal and fetal curves were smooth and showed no influence of uterine
contractions while the probes remained in good contact with the skin.
Dislodgement of the fetal probe was not a problem in the absence of ma
ternal movement but was likely during the second stage of labor. This
was readily apparent from the irregular fetal record which showed alte
rations with uterine contractions. Conclusions: Continuous assessment
of maternal-fetal inert gas transfer, with its potential for investiga
ting placental function during labor, is possible. However, the practi
cal application of this idea awaits development of less expensive and
simpler technology, which can then be evaluated in pregnancies complic
ated by placental dysfunction.