This diagram from www.capnography.com illustrates the oxygen and carbon dioxide pathway during anesthesia. The site is maintained by Bhavani Shankar Kodali, M.D., associate professor, Department of Anesthesia at Brigham and Womens Hospital and Harvard Medical School.
Pulse oximetry, which directly monitors the patient's oxygenation, came into its own as standard medical practice 20 years ago. It was about that time that its companion application, capnography, was first introduced to the medical community in the U.S.
Capnography continually and instantaneously monitors a patient's carbon dioxide concentrations in respiratory gases and is an indirect monitor of oxygenation that helps in the diagnosis of hypoxia so that corrective measures can be taken.
Yet despite its acceptance as a proven, life-saving medical application and that it is firmly endorsed by major medical associations, capnography is still not a required standard of care outside of the operating room. Proponents are pushing for it to become standard practice in all cases in which drugs are administered to ease pain or anxiety for any procedure both in and outside the OR.
“Capnography should be a requirement any time respiratory depression is a possibility,” said Debra Ford, marketing manager for Respiratory Monitoring with Respironics Novametrix LLC.
Mike Dashefsky, vice president of the patient monitoring division of Nihon Kohden, agrees.
“Capnography has many applications and is very under utilized,” he said. The company has been putting on seminars at various professional conferences to educate clients on its importance. “The feedback has been great,” Dashefsky said.
Bhavani Shankar Kodali, M.D., department of Anesthesiology at Brigham and Women's Hospital, Boston, says capnography has been the standard of care in OR but clinicians are now realizing its application outside of the OR in outpatient care centers. Dr. Kodali is an expert in capnography and has a Web site, www.capnography.com, devoted solely to the subject.
“It has been realized that capnography has so many applications,” Dr. Kodali said. “Slowly capnography is going outside of OR and awareness is growing.”
That awareness has translated into increased sales for equipment manufacturers.
“Sales have shown marketed increase,” said Rich Swenson, product manager for Nihon Kohden.
Respironics is also seeing increased sales “in anticipation of [capnography] being a required procedure,” said Ford.
Some examples of when the application should routinely be used in outpatient procedures include upper GI endoscopy, MRI (especially with children), cardiac cath labs, laparoscopies and even oral surgeries. Dr. Kodali has a whole section on his Web site devoted to educating paramedics. Two states, Massachusetts and California, are pushing for capnographs to be required on ambulances, he said.
Two Analyzers
A capnograph uses one of two types of analyzers, mainstream or sidestream. Mainstream units are used on intubated patients and have an analyzer connected to a tracheal tube for “real-time” monitoring of CO2 concentrations. Sidestream units are used on nonintubated patients using a sampling pump with a line connecting from the patient to the monitor.
Most equipment manufactures offer both devices, but technology is developing in such a way that capnographs are becoming more and more portable.
Respironics sells its own capnography equipment but also partners with original equipment manufacturers such as GE Healthcare, Philips, Zoll, Spacelabs and Draeger to sell capnographs along with their defibrillators, ECGs and ventilators.
“They all get their CO2 technology from us,” Ford said.
Capnostat is Respironics’ mainstream application equipment and LoFlo is for sidestream application. The company’s bedside equipment is called the C02SMO, which monitors both pulse oximetry and capnography. The Capnogard is strictly for capnography.
Respironics also has a hand-held unit that comes in four models as part of its Tidal Wave line. The company offers wave-form technology, which Ford says offers a more definitive profile of the quality of the patient's breathing patterns, not just a number value.
“It indicates how well the CO2 is coming out of the patient's body,” said Ford. “It gives you an actual picture of it coming out and you can see if there is an obstruction or if there is a problem with the ventilator.”
All of Respironics' equipment is solid-state design and requires no calibration.
Nihon Kohden's Cap-ONE line also is solid-state technology and requires no calibration. Such advanced technology allows for a warm-up time “of about 10 seconds,” said Swenson, as opposed to the 20 minutes that was the industry standard just 10 to 15 years ago.
The Cap-ONE line offers devices for mainstream application on both intubated and nonintubated patients. The piece is placed directly on the patient's oral/nasal adaptor and measures the CO2 expired both through the mouth and nose. This device gives a more accurate reading because it captures the natural flow of the patient's breathing, according to Nihon Kohden.
“We believe Cap-ONE is the newest evolution in capnography monitoring and we expect sales to dramatically increase,” Dashefsky said.
Oridion offers the technology of Microstream portable capnographs, Microcap (EtCO2) and MicrocapPlus (EtCO2 and SpO2), which provides an accurate, reliable and easy to use assessment of the patient's breathing quality, whether intubated or nonintubated, in any clinical setting. Microstream capnography delivers effective, proven airway management by providing the earliest indication of airway compromise.
The Smart CapnoLine Plus EtCO2 sampling line offers unique, precise measurements with improved performance for CO2 monitoring for the nonintubated patient, according to Oridion's Web site. It offers versatility for a variety of extended and deep sedation situations.
Still Not Required
As technology makes the equipment and application easier to use and more reliable, experts say the push for more routine use of capnography will gain more momentum.
“We have been waiting for capnography to become a standard of care at all [non-OR settings] for quite awhile,” said Ford. “The language is getting stronger but it is still not required.”
Still, great strides have been made, Dr. Kodali said. Twenty years ago, the rate of accidental deaths caused by anesthesia was much higher than today — one in 5,000 compared to one in 250,000 — he said, and the difference is the application of capnography.
“Capnography can monitor the airway, breathing and circulation” he said. “It gives you a full picture of how a patient is breathing, the overall quality of his respiration,” Dr. Kodali said.
One of the most essential applications of capnography, he said, is following the OR and recovery stage, when a patient is moved to his own room. The patient will be on pain medication then and that can depress respiration. Problems can go undetected without the CO2 being monitored, Dr. Kodali said.
In addition to technological advances, increased concerns about liability and lawsuits should spur pressure for capnography to become standard of care.
“Now the majority of people realize its importance,” Dr. Kodali said. “The awareness is growing.”
