CDU Contributing Editor
ATLANTA, Georgia – While this year's American College of Cardiology (ACC; Bethesda, Maryland) scientific sessions were abuzz with clinical studies on stents and implantable cardioverter defibrillators (ICDs), there was plenty of other interesting news. Automatic external defibrillators (AEDs) were a frequent subject of discussion, and noteworthy research was presented documenting the relationship between heart failure and two other conditions – diabetes and sleep-disturbed breathing (SDB).
Diabetes is a well-known co-morbidity and complicating factor for heart disease patients, but the SDB relationship is less well known or appreciated. SDB includes three subsets: Obstructive sleep apnea, central sleep apnea and mixed sleep apnea (a combination of the above two). Any of these SDB conditions can starve the heart of vital oxygen during sleep. The loss of oxygen caused by SDB can result in heart stress (even though the patient is asleep and apparently resting) leading to arrhythmias and initiating a neuro-hormonal cascade of chemoreceptors and baroreceptors. This obviously can be detrimental to the patient's condition, especially when coupled with other factors such as infections, trauma or heart attack.
While SDB has been recognized and treated as an independent condition by general practitioners and pulmonologists in the home and in alternate site settings with continuous positive airway pressure (CPAP), oxygen and other interventions, it has not been generally recognized as a congestive heart failure (CHF) co-morbidity until recently. Studies reported in Circulation, the American Heart Association (Dallas, Texas) journal, have shown that between 40% and 50% of heart failure patients exhibit SDB, and that the presence of this condition is an indicator associated with higher mortality rates. Fortunately, SDB also is treatable, with treatment resulting in significantly improved clinical outcomes. Treatment with CPAP alone has been shown to reduce heart failure-related mortality by more than 80%, back to levels of patients who do not exhibit SDB. This makes diagnosis of the type of sleep apnea important. Studies show that 60% to 80% of heart failure patients with SDB have central sleep apnea, with the balance having obstructive sleep apnea.
The diagnosis of SDB usually requires tests run overnight in a sleep laboratory. However, these tests can take weeks to arrange in some parts of the country due to backlogs for such testing and are quite expensive, typically $1,200 or more. Clearly, a less-expensive, faster alternative is required, and several companies represented on the cavernous exhibit floor at the World Congress Center were showing products to fill exactly that need. Yet very few suppliers of patient monitors or respiratory treatment devices have put together a diagnostic system that can be used in the home setting.
One that has is Nexan (Atlanta, Georgia) with its Clear Path System. The Clear Path System monitors two leads of ECG (modified CM V5 and modified Lead 2), full respiration by impedance and oxygen saturation – all from a single set of electrodes and sensors. The sensor array plugs into a small transmitter device that sends the data to the Clear Path partner, a data-capture device. Data is then dumped from this device to a conventional PC so that the physician can review it and correlate rate variations, desaturations, breathing anomalies and arrhythmias while the patient was asleep – all the data needed to determine what therapy would be indicated to treat the patient.
Only about 5% of CHF patients currently are tested for SDB. When Nexan's product reaches the U.S. market, cardiologists will be able to manage their patients directly, performing the sleep diagnostic study and keeping the revenues that the procedure generates. Rather than spending a night in a sleep lab, the patient wears the device at home and returns to the physician's office in a day or two with all the data necessary to make the diagnosis. The sleep data has been transmitted to the Nexan Partner, which is able to download the data into a base station when it is docked in the physician's office. The sensor array that the patient wears can prompt the patient to initiate additional measurements of parameters like blood pressure, spirometry and weight. The sensor array lasts for up to 24 hours, according to the company, but we see no reason they should not be able to extend the sensor time to two to three days – except perhaps to sell more sensors. The base station displays ECG and respiratory analysis, data trends, and highlights specific cardiac and pulmonary events.
Nexan has a proof-of-concept product and is looking to be acquired by a U.S. company. Unfortunately, with no revenues, the asking price is well beyond what is likely to be offered, and the Clear Path technology may die on the vine or simply inspire another firm to develop a similar product. One shortcoming of the Nexan base station is that it is proprietary, rather than being built on a consumer computing platform. The product would be stronger if the docking station plugged into a PC that provided waveform and data display. That also would reduce the cost and facilitate sharing the PC with other medical computing tasks when it is not being used for SDB testing and display purposes (which in a busy practice might be most of the time). The system was first shown at the Heart Failure Society meeting in Washington last September. The ACC conference was the second showing of the product to cardiologists. It has received FDA market clearance. There is a workable value equation here. Tests cost about $150 based on the company's price structure, but reimbursement is around $325 at present.
Elsewhere on the ACC exhibit floor, ResMed (Poway, California) was showing its advanced line of devices to treat sleep-disturbed breathing. While simple CPAP blowers are the first reimbursable therapy prescribed for SDB, many patients become non-compliant due to the discomfort of these devices and move onto more advanced bilevel positive airway pressure or demand positive airway pressure machines. The latter two modes provide a higher pressure during inspiration and a lower pressure during expiration and some mode of automatic pressure augmentation when apneas occur. ResMed's newest product is the Autoset CS, a product aimed at heart failure and other patients. The company pointed to studies showing that Autoset was better than either oxygen administered at flow rates of 2 L/min or simple CPAP at reducing the sleep arousal index and increasing slow brain wave and improving REM sleep states, as well as suppressing central sleep apnea.
However, the newest Autoset CS has some drawbacks. First, it is large and quite heavy. For heart failure or any other patients that have to lug such devices through airports, this is going to be a major problem. Second, it is expensive. Third, it lacks a 12V or 24V DC input. For patients vacationing aboard boats where 110 or 220 VAC power is not available, a 12V DC input for connection to an auto or marine battery would have been a nice feature. Finally, it is almost totally automatic, and that precludes any patient/user adjustment of the treatment regimen. While some physicians may see this as an advantage, many long-time users of such devices will see it as a limitation. Many other competitors' units have overcome such limitations. Units are available from Puritan Bennett (Pleasanton, California), Respironics (Pittsburgh, Pennsylvania) and others, several of which also were in attendance at ACC.
It seems clear that there is a trend to begin integrating some monitoring capabilities in the higher end SDB therapy devices. Pulse oximetry is likely to be the first such parameter, supplementing the airway pressure sensors already used on some devices to detect leaks around masks and nasal pillows. The challenge is to keep costs down and not institute monitoring that would itself disturb sleep. This suggests that an ear oximeter might provide a better solution than a finger sensor, although even a finger sensor works well with a bit of cable management. The key will be to keep it simple, so that subjects can disconnect quickly for activities during the night that might require them to leave their beds.
To make the data useful, it needs to reach a computer, either the patient's or his/her care providers. The emergence of low-cost, Bluetooth radio frequency connectivity provides an ideal solution for both needs, as newer computers will certainly begin implementation of Bluetooth in the next couple of years. Bluetooth would be the ideal connection to a bedside telephone appliance that could periodically (or on demand) download accumulated data to caregivers. To date, no supplier of CPAP or more sophisticated sleep therapy devices has incorporated any such link in their products. But the low cost of Bluetooth (about $5 hardware cost) will make that oversight short-lived, even if such manufacturers are not quite sure what to do with the data once the wireless link is available.
In the diagnostic area, Instromedix, now part of CardGuard (San Diego, California), was showing its Disclosure AT combination Holter and cardiac event recorder. This double-duty device provides a full three-lead ECG for 24 hours, which can be easily downloaded into the Instromedix Holter system, but it also morphs into a cardiac event recorder. In this mode it provides 18 minutes of three-lead ECG, or with an alternative lead set can provide a simulated EASI 12-lead ECG recording. The EASI technology is Philips Medical Systems' (Andover, Massachusetts) 12-lead technology, developed originally by Zymed (Oxnard, California), which Philips subsequently acquired. The ability to provide both Holter or cardiac event recording in a single device makes it possible for the cardiologist or internist to have a single pool of devices and the ability to allocate them however their clinical practice requires at any given time. It minimizes the stockpiling of extra medical device inventory and thus reduces costs. However, this unit does lack noninvasive blood pressure (NIBP) monitoring capabilities.
Ambulatory NIBP monitoring is becoming more important due to concerns about "white coat hypertension," a condition in which patients become nervous in physician offices when they are about to be tested and manifest elevated blood pressures. The availability of ambulatory monitors that track NIBP for 24-hours provide an answer to this dilemma. One such device shown at ACC was the Mobilograph, manufactured by IEM (Stolberg, Germany). It uses the oscillometric method to capture up to 300 NIBP readings at regular intervals. Readings can be programmed over a range from one reading every two minutes to one reading per hour. The device is worn by the patient with the aid of a shoulder strap and uses rechargeable AA-size batteries. The data collected can be provided in hard copy via the parallel port to an Epson LX 300-type matrix printer.
The other major device focus at ACC was defibrillation, in all of its many implementations. Biphasic waveform devices are clearly here to stay and replacing older monophasic waveform devices in all care settings. Contrary to positioning by Zoll Medical (Burlington, Massachusetts), one of the four largest providers, the exact characteristics of the biphasic waveform are not proving to be as important as access to the market. Ease of use and other factors are making a particular brand effective in the sector. Other major players in the public access segment include newcomer Cardiac Science (Irvine, California), via its 2001 acquisition of Survivalink, Medtronic (Minneapolis, Minnesota), Philips Medical and Spacelabs/Burdick (Redmond, Washington).
The size of the public access market dwarfs the existing hospital market, which is also upgrading its current installed base from manual to automatic defibrillators in most settings. The hospital segment is wrestling with how to comply with the new AHA guidelines on resuscitation, which call for first shock in 3 minutes or less, no matter where in the hospital a patient arrests. The challenge is to meet that standard on general wards where crash carts are not always readily available. A solution that is gaining momentum is the orientation of first-responder nurses to use AEDs while the hospital's Code Team is on its way. Yet, much more attention is being placed on the public access market due to its size.
AEDs are now becoming standard issue on many airlines. The equipping of trains, buses and other modes of public transportation will follow in the near future. Outfitting public buildings where large numbers of people congregate is in its early stages. These include churches, conference centers, stadiums, theaters, shopping malls, and large office buildings. The number of sites is vast, causing AED companies to salivate in anticipation of the influx of new orders. This market is in many ways a more level playing field than the hospital market, as it is not yet greatly influenced by group purchasing organizations. Philips already has 90,000 defibrillator units installed, and other companies are rapidly penetrating the public access sector. Keys to success are access to sales channels (to get there) and ease of use and support (to convince wary first responders that this is a technology they can be comfortable using).