The problem could be over-breathing, i.e. exhaling too much CO2. This lowers the blood CO2/bicarbonate levels and inhibits the oxygen release from hemoglobine

The problem could be over-breathing, i.e. exhaling too much CO2. This lowers the blood CO2/bicarbonate levels and inhibits the oxygen release from hemoglobine (https://en.wikipedia.org/wiki/Bohr_effect https://en.wikipedia.org/wiki/Bohr_effect). The remedy is to breath less, both less frequent and less voluminous. Very little breathing is needed to saturate the blood O2 levels, as can be checked with a simple pulse oxymeter. Also see https://en.wikipedia.org/wiki/Buteyko_method https://en.wikipedia.org/wiki/Buteyko_method