Any docs out there who could tell us - first put a sedative in his last meal, then local in the area of his chest, then a needle directly to his heart with the fatal drug. The thing is, there has to be one person willing to plunge that needle. Up to know the device is not seen nor the person pushing the plunger known in most executions.
Put a breathing mask on him, give him nitrous oxide (laughing gas) until he passes out, then slowly increase the percentage of nitrous oxide to 100%, and maintain until he dies.