NEW TECHNOLOGY The latest anesthesia machines improve efficiency and patient safety.

Anesthesia machines have come a long way from the manual valves and dials of years past. The latest options have features designed to streamline workflow, reduce anesthetic waste and improve patient safety. If you're in the market for a new unit, here are a few of the biggest updates to look for in the machine's basic components.

1. Flow meters
Flow meters set the levels of nitrous oxide, oxygen and air, as well as the percentage of inspired oxygen and total gas flow for the patient. In older models, this was regulated with manual flow control valves that set gas distribution based on a provider's manual calculations. New machines, though, do all of this electronically.

The latest models include a system that acts like a computer to automatically determine relative gas flows. You use a digital screen to select the amount and mixture of gas you want and let the machine do the heavy lifting. For example, if you want to achieve 50% inspired oxygen in the fresh gas mixture, you input that into the system. The machine then determines how much of the second gas (either air or nitrous oxide) must be mixed in to reach that 50% concentration.

There are other benefits to electronic flow meters. Compared to mechanical valves, new electronic machines require less maintenance or calibration, and can be integrated into your EHR system. Importantly, new machines have mechanical backup valves that can continue the delivery of oxygen to patients if power is lost.

2. Vaporizer
The machine's vaporizer adds exact amounts of volatile anesthetic to the fresh gas flow. Fresh gas is divided as it enters the machine. Part of it enters the vaporizer, which mixes the gas with the anesthetic vapor. This mixture then joins back with the other part of the fresh gas flow before entering the patient's breathing circuit. Previously, anesthesia providers manually controlled this splitting ratio using a dial to adjust the amount of anesthetic a patient would get. Now, sensors inside the electronic vaporizer determine the splitting ratio automatically based on the provider's desired amount and report that electronically. Some of the latest vaporizers can even precisely inject liquid volatile anesthetic into the fresh gas flow, much like the fuel injection system in your car.

Compared to older models, these electronic vaporizers are extremely accurate and easy to use, since you just select your desired anesthetic mixture using a digital screen. There's a downside to that, however. If your machine's screen breaks or you lose power, it could eliminate your control or supply of the volatile anesthetic. To fight this, many machines have a backup battery, though it must be regularly inspected to ensure it's charged enough to provide a minimum of 30 minutes of operation, if needed.

SEDASYS SYSTEM
Computerized Propofol Sedation Arrives in Some ORs

INTO THE FUTURE The new Sedasys system delivers sedation to patients without need of an anesthesia provider.

Being sedated by a computer? It seems like something out of a sci-fi movie, but Ethicon's Sedasys System — the first computer-assisted personalized propofol sedation machine — is making it a reality.

Sedasys is used for the IV administration of 1% propofol for select procedures, including colonoscopies and upper endoscopy screenings. The machine places patients under minimal-to-moderate sedation while monitoring vitals — all without an anesthesia provider in the room.

Instead, a clinician — either nurse or doctor — can operate the machine. Sedasys monitors the patient's oxygen, heart rate, respiration rate, blood pressure and responsiveness, and features several alarms and safety locks designed to prevent complications.

Users say that using propofol for these procedures — instead of the traditional combination of midazolam and fentanyl — shortens patient recovery time and increases efficiency.

"Before we started using Sedasys, my patients would spend upwards of an hour in the recovery area following a procedure that only took 20 to 30 minutes to complete," says Michael Basista, MD, MBA, a gastroenterologist with ProMedica Toledo Hospital, 1 of the 5 hospitals in the country using the system.

But there are limitations. The FDA originally rejected the system in 2010 due to safety concerns, only granting approval in 2013 after Ethicon agreed to require that facilities have an on-call anesthesia provider on hand and to limit the procedures for which it's used.

Anesthesia providers have also expressed concerns. "Removing the human factor from anesthesia is not logical," says William Landess, CRNA, MS, JD, corporate director of anesthesia services at Palmetto Health in Columbia, S.C. Jay Horowitz, CRNA, owner of Quality Anesthesia Care Corp. in Sarasota, Fla., notes that while Sedasys could be "a very appropriate and helpful tool," he prefers "an actual professional at the helm who has interviewed and assessed [the patient]."

— Kendal Gapinski

3. Breathing circuit
The fresh gas and anesthetic enters the breathing circuit, which connects the patient to the machine to deliver the necessary oxygen and anesthetic gases while eliminating the exhaled carbon dioxide.

One of the big advances in new anesthesia machines is fresh gas decoupling (FGD), which ensures constant tidal volume delivery to the patient. Computer systems track the amount of fresh gas flowing or requested per second. The software can then divert or limit the excess fresh gas — or limit the ventilator breath — to give the patient only what the provider requested. For example, if you want to give 500 ml of gas per breath, but the computer sees that there's an additional 68 ml coming from the fresh gas flow, it will recalculate and only give the patient the needed 432 ml from the ventilator. Alternatively, it could redirect that 68 ml or shut it off during inspiration.

Most modern machines also have compliance compensation as part of the breathing circuit. When the machine pumps gas into the patient, some of it is lost in the stretchable breathing tube. This is called compliance. Usually about 2 to 3 ml/cm is lost, so if your desired volume is set to 500 ml, you could lose between 40 and 60 ml in each breath.

New machines fight this by automatically checking for compliance in the circuit and then compensating for that. So if you want a 500 ml volume, and the machine detects 60 ml are lost due to compliance, the ventilator will instead give the patient 560 ml.

Updated breathing circuits are smaller and more compact, plus many can detect, report and even compensate for leaks. Another new feature is the warming of the breathing circuit itself, which helps avoid moisture in the machine due to the increased humidity from the patient's expiration.

ANESTHESIA AIDS
User-Friendly Features Worth Having

INNOVATIVE IMPROVEMENT Modern machines are designed with the anesthesia provider in mind.

Here are a few other updates on most modern machines that you need to check out:

• Electronic checkouts walk the provider through a daily check to look for problems such as leaks, compliance issues and electronic software malfunctions.
• Work surfaces in new models are larger, providing ample space to house charts and supplies.
• Bright LED lights help providers see in darkened ORs. Other updates include foot brakes and automatic cord controls that make cart maneuvering easier.
• Regulated auxiliary oxygen lets clinicians limit the concentration of open-delivered oxygen to minimize risk of fire.
• Low gas consumption allows for a near metabolic, very low flow of fresh gas that conserves expensive volatile agents.

— Michael A. Olympio, MD

4. Ventilator
The machine's ventilator keeps the patient breathing as close to normal as possible. Newer machines deliver each breath through pressure-controlled ventilation, which lets the provider choose the pressure of the air being pushed into the lungs, resulting in a variable volume. This method allows for better gas distribution, especially for heavier or sick patients, and for those undergoing laparoscopic surgery.

Now you can get the best of both worlds with volume-guarantee pressure-controlled ventilation. If a provider wants a square wave or constant pressure for each breath, but also a guarantee of 600 ml of volume, the ventilator can determine the safest way to hit both of the those targets while limiting excessive breaths. In turn, this allows for a safer, more even and reliable distribution of gas throughout the patient's lungs.

Ventilation has gone through other changes as well. Instead of a pneumatic bellows system (think of an accordion), some machines now use a finely tuned piston that cuts medical gas use. An even more recent update has transformed that large piston into a quarter-sized turbine that spins ultra-rapidly to push gas into the lung. Additionally, modern machines also come with many support modes to accommodate older, sicker and heavier patients, or patients who are breathing on their own.