What’s next? As the calendar turns to 2011, tech-savvy respiratory therapists and sleep technologists want to know which innovations are going to aid their future practice. While there are not any robotic RTs on our top five list, there are vibration response imaging, acoustic monitoring for asthma, contactless sleep and breathing monitoring, hypoglossal nerve stimulation systems, and a neurally adjusted ventilatory assist mode for noninvasive ventilation.
Lights, camera, lungs
Clinicians evaluating emergency department patients with shortness of breath now can watch a moving picture of the lung to distinguish pulmonary problems from congestive heart failure.
Vibration response imaging uses piezoelectric sensors placed on the patient’s back to capture the body’s natural vibration energy and convert the data into a series of images that show the lung in action. In patients with chronic obstructive pulmonary disease, the lung often appears to be popping back and forth and may be elongated or string-bean shaped. Dynamic image results are produced in 15 minutes, which far outstrips the 45 minute wait-time for brain natriuretic peptide tests typically used in differentiating COPD from heart failure. Objective data on breath sound progression, maximal sound energy shape, intensity, and distribution also is produced.
“It really gives me a better sense of how the patient is doing, particularly if I check it again after I have initiated treatment and can start to see the improvement in airflow,” said Charles V. Pollack, MD, who has studied the technology for three years and is chairman of the emergency medicine department at Pennsylvania Hospital, Philadelphia.
But clinicians less practiced in interpreting results may not see the full benefit. One study of intra-rater reliability of evaluation showed that clinicians viewing the same image multiple times consistently interpreted decreased signal in the left lower zone of the lung only 87 percent of the time. “The most plausible explanation might be the interference of the heart in the left lung fields which might make the interpretation of VRI more difficult,” the study authors speculated.1
New algorithms to assist clinicians in diagnosis will be commercially available in February. The Food and Drug Administration approved the imaging technology for use in hospitals in March, and the manufacturer expects a current procedural terminology (CPT) category III reimbursement code in 2012.
Eliminating guesswork
Some patients who cannot or will not cooperate with traditional pulmonary function testing maneuvers are using acoustic monitoring technology to manage asthma. A pocket-size device is commercially available that can be held against the patient’s throat for 30 seconds to record breath sounds and quantify the percentage of wheezing in the respiratory cycle. A patented algorithm correlates that number with an action: A patient wheezing 5 percent to 10 percent of the time should take a breathing treatment; greater than 10 percent should call his physician.
“It is kind of like an asthma thermometer,” said Larry Murdock, RRT, a California therapist employed by the manufacturer.
Long-term monitoring of problems such as nocturnal asthma or cough and occupational exposure-induced issues can be measured by a 24-hour trending device. It archives and retrieves patient data in order to track symptom trends.
A clinical version of this technology separates wheezing into internal and external wheeze rate, which may assist clinicians in differentiating between asthma and upper airway problems such as vocal cord dysfunction. In a study of 11 pediatric patients presenting to the intensive care unit, the technology was significantly more sensitive to the presence of wheeze than a physician, nurses, and respiratory therapists, and could determine the type of wheeze with equal specificity.
However, analysis was limited to breath sounds from the right lung base, and the study only included three patients who were mechanically ventilated.2
Four additional studies are planned to evaluate the technology’s use in cystic fibrosis and severe and poorly controlled asthma.
The American Medical Association has approved two CPT III codes related to acoustic monitoring: 0243T for intermittent monitoring of wheeze rate and 0244T for continuous monitoring.
Simply sleep
Electrode application and head measurements are synonymous with full, overnight polysomnography. But what if a non-contact device could eliminate all the headbands, chestbands, wires, and electrodes that patients struggle with during the night?
A cassette tape-sized contactless sleep and breathing monitoring device has been cleared for investigational use in the U.S. It uses radio frequency sensing technology to reflect a 5.8 GHz signal off the patient from a nightstand or table within 5 feet of the bed. The echo carries back biomotion information that specialized software separates into breathing and body movement channels. Its measurement of apnea-hypopnea index shows a 91 percent correlation with polysomnography, with 81 percent of subjects showing an error rate less than 10 events per hour.3 However, the device tends to underestimate AHI levels above 30.
Several weeks of data can be stored on the device’s standard 4GB SD card. “It makes multi-night studies more convenient,” said Conor Henegan, PhD, the manufacturer’s chief scientific officer and former professor at the University College Dublin’s School of Electrical, Electronic and Mechanical Engineering. “We see this being used in a broader range of sleep monitoring applications.” For example, patients with mandibular advancement devices or continuous positive airway pressure therapy could be monitored at home to assess treatment.
An ongoing study is assessing the device’s ability to provide long-term monitoring of respiratory track patterns that could indicate when a patient’s COPD, CHF, or asthma is deteriorating and they need to visit their pulmonary specialist. In the future, the manufacturer may add pulse oximetry and airflow channels for the device to be considered for reimbursement by the Centers for Medicare & Medicaid Services for sleep apnea diagnosis.
New developments are making home sleep testing devices more practical for forward-thinking sleep centers. Features such as color-coded sensors and auto-start testing, which begins recording as soon as the patient puts on the device, are simplifying set-up. Lock-in lead connectors and immediate cellular transfer of patient heart rate and oxygen saturation ensure that the test runs smoothly throughout the night. Manufacturers also are testing new channels, including one for carbon dioxide levels that would help diagnose nocturnal hyperventilation common in patients with neuromuscular disease.
“Sleep labs will always be the place for those other types of disorders that are more elusive,” said Kimberly Trotter, MA, RPSGT, practice manager for University of California-San Francisco Sleep Disorders Center. Narcolepsy, parasomnias, and leg movement disorders require detailed monitoring of PSG and the presence of a sleep technologist.
Targeting the tongue
Sleep professionals may remember an implantable device developed in the 1990s that reduced AHI and opened the airway by stimulating the genioglossus muscle under the tongue. Patients’ symptom improvement was dramatic but inconsistent. “Some people didn’t respond at all, some people responded completely,” recalls Eric Kezirian, MD, MPH, director of the sleep surgery at University of California-San Francisco’s otolaryngology-head and neck surgery department.
Three U.S. manufacturers are developing hypoglossal nerve stimulation (HGNS) systems that excite several muscles to more consistently flatten the tongue, stiffen the sides of the airway, and slide forward the genioglossus. A small battery-powered device is surgically implanted in the upper chest wall or under the clavicle, and a multi-contact electrode is wrapped around the hypoglossal nerve. A wireless remote control activates either constant stimulation of various muscles or a sensor that arouses the hypoglossal muscles only during patient breath attempts during sleep.
“It is without question the most exciting and biggest innovation that could possibly be coming down the pike,” said Terrance Davidson, MD, FACS, chief medical officer for one of the manufacturers and professor of head and neck surgery at the University of California-San Diego School of Medicine. “We already have early evidence that if we successfully start stimulating the nerve and moving the tongue that the tongue actually changes its muscle fibers and may require less stimulation.”
A small study assessing the outcomes of 18 patients at three months post-implant showed that AHI was halved in nearly 70 percent of patients, and 92 percent of patients were adherent with the therapy.4
Two slightly larger ongoing clinical trials will assess 60 patients’ outcomes at six months after implantation.5,6
Researchers are determining the best candidates for HGNS. Those most likely to benefit include patients whose tongue plays a large role in their apnea, according to Kezirian, a scientific adviser for one of the HGNS device manufacturers. The HGNS system needs to be replaced when the battery wears out, and patients cannot undergo magnetic resonance imaging tests, so continuous positive airway pressure therapy remains the first line treatment. However, HGNS systems could help patients who cannot tolerate CPAP or could be used in combination with the treatment.
“There are always patients who just can’t tolerate it and are always looking for something else,” said Trotter, who has studied the technology for the last six months. “You have to find the right patient who is willing to go through the surgery and have an implantable device.”
Breathing harmony
Inefficient breathing and delayed ventilator cycling caused by mask leaks is common among patients using noninvasive ventilation. Until now, clinicians lacked a state-of-the-art tool to counter asynchrony. Neurally adjusted ventilatory assist mode, already commercially available for invasive ventilation, was introduced this fall for noninvasive modes.
“The mode senses when to start (when the triggering would be), how much the patient wants to breathe, then it senses the most important part: when he wants to stop the breath,” explained Sylvia G”thberg, MD, PhD, of Queen Silvia Children’s Hospital in Gothenburg, Sweden, and medical adviser for NIV NAVA’s manufacturer. Unlike conventional NIV, which relies on the airway pressure and flow to detect patient effort, NIV NAVA’s breath triggering and cycle-off are not artificially triggered by air leaks around the patient’s mask.
Several ongoing trials will compare synchrony in NIV NAVA and conventional modes and assess the potential physiological benefit.8
With NIV NAVA, Dr. G”thberg predicts that the improved synchrony could decrease the need for invasive ventilation and thus minimize lung injury. “It is a paradigm shift between the old way of listening to the patient and the new way of listening to the patient.”
Not every patient will need NAVA NIV. “It is not a panacea,” said Felix Khusid, RRT-NPS, RPFT, administrative director for respiratory therapy and pulmonary physiology center at New York Methodist Hospital in Brooklyn. He finds the mode most valuable in difficult-to-synchronize and difficult-to-wean patients, such as select patients recovering from open-heart surgery or who have COPD.
The new mode also may not be intuitive for clinicians accustomed to working with the delayed triggering of conventional ventilation, according to Khusid.
“The education of physicians and respiratory therapists is essential for this technology to take off,” he said.
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Contact Kristen Ziegler at [email protected].
