Underwater Anesthesia Machines? Well, Almost. Closed-Circuit Rebreathers and The Leap Forward for Advanced Diving, Exploration, and Discovery.

Abstract

Anesthesia machines are complex multi-component systems that control the delivery of specific concentrations of gases and allow vigilant monitoring of the patient. There are many variations in design and function, but they generally consist of a breathing circuit, ventilator, anesthetic vaporizer, scavenging system, carbon dioxide (CO2) absorbent, and multiple physiologic monitoring systems. Classification of the breathing systems range from open and semi-open systems, where gases are not rebreathed, to closed and semiclosed systems in which gases are rebreathed. The closed and semi-closed designs, which are collectively known as circle breathing systems, consist of a circuit where exhaled gases enter a loop to be reused, fresh gas is added, and excess gas is expelled through a waste valve. The gas in the circuit is filtered through scrubbers that remove CO 2 through chemical absorption and monitor levels of CO2. Fresh oxygen is added to the circuit, and galvanic oxygen sensors analyze the fraction of inspired oxygen, or FiO2.[1] Similar in design and function to these anesthesia systems, closed circuit rebreathers (CCRs) are becoming increasingly prevalent in the recreational scuba diving community. Once relegated to only military pursuits and a few advanced civilian divers, the popularity of CCRs has increased sharply in the past two decades. This rise in CCR use is due to an increasing number of manufacturers, decreased production costs, and the increasingly recognized benefits of CCRs compared with traditional open-circuit (OC) scuba diving equipment. CCRs offer numerous advantages compared to traditional OC equipment. First, CCRs provide divers with warm, humidified breathing gas due to its passage through the respiratory