Anesthesia machines haven't changed much over the years in what they do: safely delivering oxygen, air and volatile anesthetics to the patient. However, they've changed in how they do their job. As we'll show you, today's new machines are information centers as well as advanced delivery and ventilation devices that let anesthesia providers do their jobs with more precision than ever before.

Dial in your desired rates and levels
Newer anesthesia machines have a lower volume anesthesia breathing circuit, which has a nice domino effect: Because volatile anesthetics titrate faster, you can lower the fresh gas flow. Lower fresh gas flow can reduce your costs for gases and especially for volatile anesthetics. Fresh gas flow rate through the vaporizer is a large component of usage of volatile anesthetics such as desflurane or sevoflurane.

Glass flow meters have long been standard on anesthesia machines. Traditionally, you'd individually adjust the flow rate of each gas with manual flow control valves at the bottom of tapered glass tubes with a floating bobbin that indicated the flow rate of oxygen, air and nitrous oxide. Newer machines feature electronic flow meters that let you dial in your desired fresh gas flow rate and oxygen level.

With electronic flow meters, the machine automatically proportions the gases to achieve the desired oxygen concentration of the fresh gas mixture. With mechanical flow meters, if you want to deliver a specific oxygen concentration, you must manually calculate the flow rates of pure oxygen and air in order to get 30% oxygen. This is especially important when there is risk of combustion, for example, when using electrocautery near the airway. Some machines have a mechanical flow meter built in as a backup in case of an electronic flow meter failure. This mechanical flow meter still allows for the use of the anesthetic vaporizers and breathing circuit. Some newer machines offer a modular design of the anesthesia breathing circuit, which you can change quickly in case of a contamination or an issue with the function during machine checkout. This can save valuable OR time.

Smart ventilation
Although mechanical ventilators have long been standard on anesthesia machines, modern versions have ventilators with capabilities that were once only found in ICU ventilators. Traditional anesthesia machine ventilators offer 2 standard ventilation modes, volume-control ventilation and pressure-control ventilation, both of which are control modes. Volume-control mode delivers a set volume breath at a selected rate up to a maximum pressure. Pressure-control mode delivers set pressure to the circuit that delivers a volume that may be highly variable based on dynamic patient conditions. Pressure-control mode is most often better, physiologically, for patients. Some newer machines have the option of a ventilation mode that allows a pressure-control mode where a specific volume of breath is set. In a pressure-control mode, the machine measures each breath and adjusts to the effects of changes within the patient such as position changes or abdominal insufflation pressure changes.

Newer ventilators can be set to recognize when the patient is breathing spontaneously and support ventilation to ensure the patient receives the appropriate amount of volume. The machine may also be set to sense when a spontaneously ventilating patient stops breathing and then go automatically into a control mode if the patient needs it. This can be especially helpful when it's time to wean the patient from the mechanical ventilator and resume spontaneously breathing. It also helps prevent coughing when the patient's breath becomes out of sync with the ventilator-generated breath.

For a spontaneously breathing patient under general anesthesia, there is resistance to air flow within the anesthesia breathing system, which can be overcome by different modes of support available on newer anesthesia machine ventilators. This can be beneficial to patients in maintaining the appropriate amount of airflow in an assistive mode. The tidal volume of gas can be delivered by way of a traditional bellows system (like an accordion) or newer piston system. A piston system uses less gas than a bellows system because it doesn't need any "drive gas" to initially fill the bellows.

Greater information generation
Anesthesia machines are becoming information centers. Depending on the system, today's machines monitor the patient's incoming and outgoing concentration of oxygen, nitrous oxide and carbon dioxide. You can also monitor the patient's consumption of volatile anesthetics and other clinical parameters.

With the increased adoption of anesthesia information management systems, you soon may be using your anesthesia machine in generating the anesthesia portion of the patient's electronic medical record. A digital anesthesia record is more accurate than a handwritten record because it's a continuous record and not based on data at specific time points entered by the provider. This digital record can be helpful in reviewing cases, investigating specific events of a case, or supplying information requested by other departments or agencies, since you can see the order of events in the data gathered by the system.

As we electronically monitor more parameters involving patient care, you can set alarms to alert you to changes in patient status. For example, an anesthesia machine alarm can alert providers if a breathing circuit is disconnected, or if airflow is obstructed.

As anesthesia machines do more, it's increasingly important to make sure that every component is working properly during each case. Newer machines automatically check most of the parts you should check at the beginning of each day and between cases, making the process quicker and less cumbersome. This also allows for an electronic record verifying the date and time when each component was checked. In the event of an emergency, you can bypass the machine check.