Reviewing a Clinical Revelation
Page 14
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Reviewing a Clinical Revelation
Advanced Applications of Transtracheal Oxygen Therapy
One crisp October morning in 1991, Dr. Kent Christopher and John Goodman, RRT, were making their usual morning rounds in Denver’s Presbyterian-St. Luke’s Hospital. As medical director and clinical coordinator respectively at the affiliated Institute for Trans-tracheal Oxygen Therapy, their morning would include the usual assessment and treatment of patients receiving oxygen via a transtracheal catheter. While this morning began much like any other in their daily routine, it would end with a clinical revelation for a nontraditional application of the transtracheal oxygen therapy (TTOT) process that is gaining popularity today.
The Defining Moment
On their rounds, Dr. Christopher and Goodman stopped to visit a longtime TTOT patient suffering from end-stage COPD. The consequential organ systems failure that accompanies severe lung disease had taken its toll, and the patient was admitted to the hospital to spend her last days.
The patient and family had decided previously that only palliative support be given. Physicians provided morphine for comfort and increased her TTOT to 6 Lpm to maintain acceptable oxyhemoglobin levels. She had been comatose for several days, and each day that passed was one more in excess of clinical expectations.
As Dr. Christopher and Goodman approached the bedside, they began to observe the patient’s ventilatory effort. They had received reports from respiratory therapists and nurses that for the past several days the patient had experienced extended periods of central apneas. Their observations confirmed the reports. The patient’s respiratory rate was 3 bpm to 4 bpm with minimal chest excursion.
Despite the lack of ventilation, she continued to have a normal sinus rhythm, normal skin color and oxygen saturations greater than 90 percent. Out of clinical interest, they drew an arterial blood gas.
Defying Clinical Logic
Dr. Christopher and Goodman speculated as to what the ABG results would be. Clinical logic would dictate that the markedly depressed ventilatory effort should result in a PCO2 significantly higher than the patient’s normal chronically compensated level. But how then could one explain the stability of the other vital signs? The results revealed one of the best blood gases seen on this patient in years. The debate that followed entailed a classic review of respiratory physiology.
Studies done in the late 1980s and early 1990s proved that patients using TTOT at flow rates of 5 Lpm to 8 Lpm had reductions in inspired minute ventilation, physiologic dead space and the oxygen cost of breathing.1,2,3 Dr. Christopher and Goodman were keenly aware of the literature and anecdotal evidence from their own patients of improved dyspnea and sleep following transtracheal catheter placement. They concluded that the 6 Lpm flow of oxygen through the catheter not only maintained oxygenation, but also provided most of the necessary minute ventilation required to eliminate CO2 for this patient. For all practical purposes, she had been receiving ventilatory support since admission.
The brief experience with this patient prompted further clinical studies by Dr. Christopher and Goodman, their colleagues and other investigators. Their work validated the conclusions about the previous patient as well as confirmed and quantified all the clinical observations and other subjective data regarding the effects of high flow transtracheal oxygen. The result was an advanced application of standard transtracheal oxygen therapy.
TTAV
Transtracheal augmented ventilation (TTAV) is a form of therapy in which flow rates of
6 Lpm to 15 Lpm of heated humidified gas at a specific FiO2 is utilized to provide ventilatory assistance to patients suffering from chronic ventilatory insufficiency from COPD. The internal part of the catheter lies inside the trachea just above the carina and allows the flow of gas to bypass the upper airway, enhancing oxygen delivery and CO2 removal. Patients already on standard TTOT are converted easily to the therapy because they already use the delivery device.
The goal is to rest the muscles of ventilation by facilitating the removal of expired gas and thus augment the resting minute ventilation. The oxygen consumption of the muscles of the thoracic cage is increased in these patients, and TTAV allows for a decrease in the energy expenditure of breathing.4 Patients utilizing this therapy are generally prescribed for nocturnal use. Some also may use TTAV for short periods of time during the day to rest before continuing activities of daily living. This rest is critical to their health and maintenance, enabling them to function without significant alterations in their lifestyles.
Delivering gas through a transtracheal catheter at higher flow rates calls for the same protocols for heating and humidifying as in traditional mechanical ventilation. The original technology used for TTAV home use comprised a hodgepodge of pieces of equipment that had to be precisely integrated to accomplish the desired results. This would typically include a 50 psi liquid oxygen reservoir and an air compressor run through a blender to achieve the desired FiO2 and flow rates. The flow of gas would then be directed through a servo-controlled humidifier and out the inspiratory limb of a heated wire neonatal ventilator circuit connected to the transtracheal delivery tubing.
While this system worked well, there were too many idiosyncrasies associated with maintaining and troubleshooting all the integrated pieces of equipment in the home setting.
The demand for the technology to provide this therapy was sufficient enough to prompt the development of an oxygen concentrator with specific intrinsic modifications to allow for flow rates up to 15 Lpm with FiO2 settings from 35 percent to 77 percent. The servo-controlled humidifier and heated wire circuit remain as integral parts. This new system replaces the cumbersome tandem of the previous gas delivery devices and is more user-friendly system for patients at home.
When compared to noninvasive positive pressure ventilation, TTAV has a distinct advantage in that clinical outcomes are almost always positive with the TTAV due to the difference in patient compliance in the two therapies. The disadvantage is that it requires a mildly invasive surgical procedure.
Weaning From MV
Because the concept of TTAV originated in the hospital, it’s only fitting that a further application be applied to the same setting. Studies of patients receiving TTAV in the home documented reductions of more than 50 percent in inspired minute ventilation.3 The minimized work of breathing is a desired element when weaning from mechanical ventilation and most importantly does not require the surgical insertion of a TTOT catheter.
TTAV can be easily administered through a trach tube. By drilling a 5/32 inch hole in a Shiley tracheostomy button, the button can be placed over a standard tracheostomy tube and SCOOP catheter inserted and secured on the outside.
Denver’s Vencor Hospital incorporates the TTAV weaning procedure as a part of their daily routine. According to Doreen Siegwarth, RRT, clinical manager of respiratory care, approximately 50 percent of patients undergoing weans at the facility are on TTAV. Specific protocols are in place for identifying patients, and policies and procedures are followed accordingly. Patients weaned by TTAV who will require continuous oxygen at discharge have the option of allowing the stoma to close around the TTOT catheter and can be safely discharged home on this therapy.
Treating OSA
Another clinical application of TTAV is for obstructive sleep apnea (OSA) treatment. Patient reports of improvement in quality of sleep with TTAV were initially attributed to the reduced work of breathing experienced with the therapy. Studies later determined that there were additional physiologic elements that also contributed to this phenomenon.
In OSA, delivering oxygen directly into the trachea more reliably prevents hypoxemia and increases mean airway pressure below the site of obstruction much like CPAP does above the site.5,6 While nasal CPAP continues to be the most appropriate mode of therapy, patients who require CPAP and oxygen may consider TTAV as a viable modality in the treatment of OSA.
Reimbursement
TTOT is a proven therapeutic modality, however, the major barrier to its popularity is reimbursement. Because the vast majority of patients who seem to benefit from it are over 65, Medicare is the primary payer for their Part B benefits. Currently, no reimbursement exists for
the catheter, as the Health Care Financing Administration con-siders it a delivery device that falls in the category of the nasal cannula. The same is true for the TTAV technology.
With the support of physician groups, lobbying efforts are under way for a revision in procedural terminology and fee schedule coding for reimbursement for the TTOT catheter and the TTAV system. Hopefully, we will see the fruits of their labor in the near future, and more patients will benefit from the technology.
REFERENCES
1. Couser JI, Make BJ. Transtracheal oxygen decreases inspired minute ventilation. Am Rev Respir Dis. 1989;139:627-31.
2. Bergofsky EH, Hurewitz AN. Airway insufflation; physiologic effects and use in patients with chronic CO2 retention. Am Rev Respir Dis. 1989;140:885-90.
3. Hurewitz AN, Bergofsky EH, Vomero E. Airway insufflation; increasing flow rates progressively reduces dead space in ventilatory failure. Am Rev Respir Dis. 1991;144:1229-33.
4. Yager ES. Transtracheal Augmentation of Ventilation. ADVANCE for MRC. 1996;110:44-6.
5. Farney RJ, Walker JM, Elmer JC. Transtracheal oxygen, nasal CPAP, and nasal oxygen in five patients with obstructive sleep apnea. Chest. 1992;101:128-35.
6. Spofford BT, Christopher KL, Hoddes E. Transtracheal oxygen for obstructive sleep apnea. Chest. 1986;89:458.
McDonald is regional vice president of operations at Pediatric Services of America Inc., Denver.
Historical Overview
The Nocturnal Oxygen Therapy Trials study of the late 1970s was the first to document the beneficial effects of compliance with oxygen therapy.1
The study confirmed that chronically hypoxemic patients using the nasal cannula as a delivery device only received an average of 18 hours a day on oxygen. Patients complained of discomfort, which caused them to remove it for periods of time during the day, and dislodging of the cannula from the nares during sleep. Even though these patients never achieved 24-hour compliance with therapy, they had better outcomes than those who used oxygen 12 hours or less.
In an effort to circumvent some of the inherent problems associated with the design of the nasal cannula, Dr. Henry Heimlich developed in 1982 a procedure that involved the insertion of a 16 gauge Teflon™ IV catheter directly into the tracheal interspace between the second and third tracheal rings.2 The external end of the catheter was connected to an oxygen supply hose allowing oxygen to be delivered directly into the trachea. Transtracheal oxygen therapy (TTOT) was born.
Patients who had the procedure experienced relatively few complications, achieved true 24-hour-a-day compliance, and were noted to have reduced oxygen flow rates by as much as 50 percent of that with a nasal cannula. Other anecdotal reports noting improvements in shortness of breath and exercise tolerance prompted numerous other clinical investigators to perform studies that validated Heimlich’s work.
In 1986, Dr. Kent Christopher, a pulmonologist, teamed with Dr. Brian Spofford, an ear, nose and throat physician also at Denver Presbyterian-St. Luke’s Hospital, and the two developed a new TTOT catheter that would subsequently be used in their studies. The Spofford Christopher Oxygen Optimizing Program (SCOOP™) ultimately became the commercial name for the procedure, a comprehensive clinical program, and the transtracheal catheter as well.
The SCOOP catheter is now used on an estimated 14,000 patients in the United States and more than 600 patients throughout 10 countries in Great Britain and Europe.
REFERENCES
1. Nocturnal Oxygen Therapy Trial Group. Continuous or nocturnal oxygen therapy in hypoxemic chronic obstructive disease. Ann Intern Med. 1980;
93:391-8.
2. Heimlich HJ. Respiratory rehabilitation with a transtracheal oxygen system. Ann Otol Rhinol Laryngol. 1982;91:643-7.
–Mike McDonald, BS, RRT
