Multi Frequency Phase Fluorimetry (MFPF) for Oxygen Partial Pressure Measurement: Ex Vivo Validation by Polarographic Clark-Type Electrode

BACKGROUND: Measurement of partial pressure of oxygen (P(O2)) at high temporal resolution remains a technological challenge. This study introduces a novel P(O2) sensing technology based on Multi-Frequency Phase Fluorimetry (MFPF). The aim was to validate MFPF against polarographic Clark-type electrode (CTE) P(O2) measurements. METHODOLOGY/PRINCIPAL FINDINGS: MFPF technology was first investigated in N = 8 anaesthetised pigs at F(IO2) of 0.21, 0.4, 0.6, 0.8 and 1.0. At each F(IO2) level, blood samples were withdrawn and P(O2) was measured in vitro with MFPF using two FOXY-AL300 probes immediately followed by CTE measurement. Secondly, MFPF-P(O2) readings were compared to CTE in an artificial circulatory setup (human packed red blood cells, haematocrit of 30%). The impacts of temperature (20, 30, 40°C) and blood flow (0.8, 1.6, 2.4, 3.2, 4.0 L min(−1)) on MFPF-P(O2) measurements were assessed. MFPF response time in the gas- and blood-phase was determined. Porcine MFPF-P(O2) ranged from 63 to 749 mmHg; the corresponding CTE samples from 43 to 712 mmHg. Linear regression: CTE = 15.59+1.18*MFPF (R(2) = 0.93; P<0.0001). Bland Altman analysis: mean(diff) 69.2 mmHg, range(diff) -50.1/215.6 mmHg, 1.96-SD limits -56.3/194.8 mmHg. In artificial circulatory setup, MFPF-P(O2) ranged from 20 to 567 mmHg and CTE samples from 11 to 575 mmHg. Linear regression: CTE = −8.73+1.05*MFPF (R(2) = 0.99; P<0.0001). Bland-Altman analysis: mean(diff) 6.6 mmHg, range(diff) -9.7/20.5 mmHg, 1.96-SD limits -12.7/25.8 mmHg. Differences between MFPF and CTE-P(O2) due to variations of temperature were less than 6 mmHg (range 0–140 mmHg) and less than 35 mmHg (range 140–750 mmHg); differences due to variations in blood flow were less than 15 mmHg (all P-values>0.05). MFPF response-time (monoexponential) was 1.48±0.26 s for the gas-phase and 1.51±0.20 s for the blood-phase. CONCLUSIONS/SIGNIFICANCE: MFPF-derived P(O2) readings were reproducible and showed excellent correlation and good agreement with Clark-type electrode-based P(O2) measurements. There was no relevant impact of temperature and blood flow upon MFPF-P(O2) measurements. The response time of the MFPF FOXY-AL300 probe was adequate for real-time sensing in the blood phase.