Simple Rapid Methods of Estimating Arterial and Mixed Venous pCO2

MEDICAL JOURNAL over into the absorber and back 10-15 times; allow the mercury to fall until KOH level returns to zero (this is accomplished by using the cock (C) to regulate rate of fall and the screw clip (S) for final fine adjustment) ; read the % CO, off the burette; repeat passage to check that absorption is complete. The analysis takes less than two minutes from start to finish. Accuracy. -Serialanalyses are reproducible to within L 0. 05%. Several comparisons both with the standard Haldane and with Lloyd's modification (Lloyd, 1958) gave agreement which was usually within ±0. 05% and never outside 0. 1 %. This degree of accuracy is more than adequate for the purpose for which the instrument is intended. Modified Instrument The insert shows an alternative arrangement which, at the expense of the complexity of two taps instead of one, slightly speeds up the analyses and facilitates servicing. The calibrated volume includes the bores of the two taps and the connecting tube. The instrument is left with tap 1 (T) and tap 2 (1) ; turn tap 2 (F-o) and adjust KOH level to zero. Tap 2 is then turned (J) ; the mercury is forced up into the stem of tap 1 and the sample of air is flushed through both taps; tap 1 is turned (³) and the sample is introduced to 0 (10 ml. ) ; tap 1 is turned (H) ; tap 2 is turned (<-) ; the zero level is checked, and absorption carried out as described above, Cleaning through with acid can be done with tap 2 (I) without needing to empty the KOH from the absorption pipette. I am grateful to Dr.