Hemoglobin Mass and Blood Volume at Moderate Altitude: Establishing Lean-Body-Mass-Adjusted Reference Values for...

Area of Science:

• Physiology
• Altitude Medicine

Background:

• High altitude living alters blood composition, increasing red blood cell volume (RBCV) and decreasing plasma volume (PV).
• These changes complicate the interpretation of hemoglobin (Hb) and hematocrit (Hct) levels.
• Accurate assessment of blood volume (BV) and hemoglobin mass (Hbmass) is crucial for clinical practice in moderate-altitude populations.

Purpose of the Study:

• To assess blood volume (BV), red blood cell volume (RBCV), plasma volume (PV), and hemoglobin mass (Hbmass) in moderate-altitude residents.
• To derive reference ranges for these parameters, adjusted for lean body mass (LBM), for clinical application.
• To understand the physiological adaptations to moderate altitude.

Main Methods:

• Recruited 158 moderate-altitude residents (2250 m) and 40 sea-level controls.
• Determined blood volumes and Hbmass using carbon monoxide rebreathing.
• Quantified lean body mass (LBM) via dual-energy X-ray absorptiometry.

Main Results:

• Moderate-altitude men showed significantly increased BV, RBCV, and Hbmass compared to controls when normalized to LBM.
• Gender differences in RBCV and Hbmass disappeared when adjusted for LBM, while women had higher BV due to increased PV.
• Altitude residents exhibited higher RBCV and lower PV per body weight compared to controls.

Conclusions:

• Moderate altitude is associated with increased blood volume primarily due to higher red blood cell volume.
• Elevated RBCV in moderate-altitude dwellers explains higher hemoglobin levels.
• Proposed reference ranges for blood volumes and Hbmass, adjusted for LBM, are recommended for clinical use.