Time and sample site dependency of the optimized co-rebreathing method.

Area of Science:

• Physiology
• Medical Diagnostics

Background:

• Estimating hemoglobin mass (Hbmass) is crucial for assessing red blood cell health.
• A novel 2-minute carbon monoxide (CO) rebreathing method offers a faster alternative to conventional procedures.
• Concerns exist regarding incomplete circulatory mixing of CO potentially affecting the accuracy of the 2-minute method.

Purpose of the Study:

• To investigate if the sampling site (capillary vs. venous blood) impacts carboxyhemoglobin (%HbCO) measurements.
• To evaluate the reliability and accuracy of the 2-minute Hbmass estimation method.
• To compare the 2-minute method against the established 20-minute CO-rebreathing criterion.

Main Methods:

• Compared fingertip capillary and antecubital venous blood samples at various time points (4-12 min) after a 2-minute CO rebreathing period.
• Utilized a 20-minute CO rebreathing procedure with simultaneous capillary and venous blood collection as a reference.
• Assessed the reliability of a modified 2-minute CO rebreathing test with capillary blood sampled at 8 and 10 minutes.

Main Results:

• The 2-minute Hbmass estimation using capillary blood was 4.8% lower than venous blood when compared to the 20-minute method.
• Peak carboxyhemoglobin levels in venous blood occurred at 6 minutes.
• Minimal differences between capillary and venous %HbCO were observed at 8 and 10 minutes, with low typical error (1.1-1.2%) for the modified 2-minute test.

Conclusions:

• A modified 2-minute CO rebreathing test is accurate and reliable for Hbmass estimation.
• Sampling capillary or venous blood 8-10 minutes after initiating CO rebreathing allows for complete circulatory mixing.
• This optimized protocol provides a dependable method for determining hemoglobin mass.