This cardiopulmonary definition of death was the operative standard, and it was considered largely reliable by the medical community of the era.

The concern about premature burial that had animated the nineteenth century had been substantially addressed by improvements in medical practice, including the routine use of stethoscopes for auscultation and the development of better examination protocols.

The complications of the cardiopulmonary definition of death became more apparent in the twentieth century, as resuscitation techniques improved and as the medical community encountered situations in which heart function had ceased but patients could be revived — first through external cardiac massage and mouth-to-mouth resuscitation, and later through more sophisticated resuscitation techniques.

The development of intensive care medicine and the recognition that patients could be maintained by mechanical support in states that would previously have been considered death eventually led to the development of the concept of brain death as a separate and complementary definition of death.