27, 6, 2, 32
The canonical physiological review of extracorporeal gas exchange, by the field's founding investigator. The anchor external source for Chapter 27.
Rated flow — the flow of standardised venous blood exiting a membrane lung at 95% saturation; if outlet saturation is below 95% at a flow below rated flow, oxygenator function is reduced, usually from clot in the blood path. The paper defines 'standardised venous blood' TWICE AND DIFFERENTLY: Hb 12 g/dL with 70% saturation in the body, Hb 12 g/dL with 75% saturation in the summary. Chapter 6 had already recorded a 70-versus-75 discrepancy between textbooks; Chapter 27 shows it exists inside this paper, and the 2026 ISO 7199 standardisation document adds a third value of 65 ± 5%.
Gas transfer. Sweep gas flow is normally matched 1:1 to blood flow (V/Q 1:1); at that ratio outlet PCO2 is typically 35–40 mmHg and CO2 removal roughly equals oxygen delivery. Raising the ratio to 2, 3 or 10 can drive outlet PCO2 to 5–10 mmHg with NO change in oxygenation. Complete removal of a resting adult's CO2 production is achievable at blood flows as low as 500 mL/min, against roughly 6 L/min for full oxygenation. Sweep gas flow has no effect on oxygenation because the sweep is essentially always 100% oxygen.
Two membrane failure modes, presenting differently: clot in the blood phase (rising resistance, falling oxygenation, replace the device) and water in the gas phase (blocks CO2 transfer specifically, treated by increasing gas flow).
Oxygen kinetics. Normal delivery is homeostatically held at 5 times consumption, with about 20% extracted at rest. Worked example: an 80 kg adult needing 240 mL/min, venous saturation 60%, Hb 11 g/dL requires 4.1 L/min of blood flow; the circuit must have a rated flow over 5 L/min. Target arterial saturation 80–90%, titrated by ECMO flow and haemoglobin.
The contested recommendation, quoted verbatim in Chapter 27 Controversy 1: "The risks of transfusion (mismatch, hepatitis) are rare and minimal compared to the risk of high flow... Therefore, if the patient is anemic, transfusion is favored over high flow when optimizing oxygen delivery." This book declines to adopt it as written; the stated harms are a generation out of date.
TERMINOLOGY DISCREPANCY FLAGGED: the retrieved text names haemoglobin-bound CO2 'carboxyhemoglobin' where the correct term is carbamino-haemoglobin. Possibly an indexing artefact; the substantive claim (most CO2 removed comes from the bicarbonate pool) is unaffected and used.
Read as indexed full-text passages. DOI not independently resolved.