What this case supports, and what it does not

The guided case supports a specific illustrated electrode configuration: pH, PCO2, and PO2 are directly measured through three electrode principles; other configured systems can directly measure additional analytes. Bicarbonate and related values are calculated from those measurements, and co-oximetry is a separate spectrophotometric measurement of hemoglobin fractions.

It does not support a specific numeric magnitude for how much a given bubble size or heparin dilution volume changes a result; that number depends on the analyzer, the bubble size, and the dilution ratio. It does not claim that capillary or venous bicarbonate reliably tracks arterial bicarbonate in adults; the supporting guideline used here covers neonatal and pediatric capillary sampling specifically. It does not teach arterial puncture technique, and it does not make an unbounded claim about capillary PO2; validation for the exact population, perfusion, and configuration is required before systemic-oxygenation use.

Everything method-specific here, the exact measured-versus-calculated parameter list, the co-oximetry wavelength count, and the reference intervals, is analyzer- and configuration-dependent and must be confirmed against the laboratory's current manufacturer instructions for use rather than assumed from any single platform, including the illustrated configuration used here.

When a blood gas result surprises you, work backward through measured values, calculated values, specimen handling, and only then patient physiology, and confirm every threshold you use against your own laboratory's current procedure.