When the cardiovascular pulsation is weak even under cardiopulmonary bypass (CPB), pulse oxygen saturation at finger tip cannot be detected, but tissue oxygenation still can be monitored by NIRS.

• 当心血管搏动微弱甚至使用体外循环时,脉搏血氧计已无读数,但组织血氧参数无损监测仪仍能提供信息。