A Harmonic Convergence: Noninvasive Ventilation Meets the Transtracheal Catheter

Clinicians have an alternative to CPAP, bilevel positive airway pressure, and NPPV for treating patients with OSA and COPD.

The benefits of continuous positive airway pressure (CPAP) and bilevel positive airway pressure ventilation for treating nocturnal sleep apnea are well established, and thousands of patients have benefited from the technology, which enjoys a track record spanning more than 30 years. More recently, the benefits have been extended to include noninvasive ventilation (NPPV) for chronic obstructive pulmonary disease (COPD) patients in emergency departments, in ICUs, and at home. Noninvasive ventilation provides the benefits of ventilation support without the need for an artificial airway. It has become a reliable tool in the management of both acute and chronic respiratory failure, while preserving normal speech, cough, and swallowing and circumventing the need for intubation or tracheostomy.

Noninvasive ventilation is a reliable and probably underutilized technology. A Cochrane Review of the topic suggests “NPPV should be the first line intervention in addition to usual medical care to manage respiratory failure secondary to an acute exacerbation of chronic obstructive pulmonary disease in all suitable patients. NPPV should be tried early in the course of respiratory failure and before severe acidosis, to reduce mortality, avoid endotracheal intubation, and decrease treatment failure.” 

The noninvasive patient interface has always presented a challenge, however. To meet that challenge, a mind-boggling array of nasal masks, face masks, nasal pillows, and their associated straps and pads have been developed in an attempt to maintain an adequate seal while minimizing patient discomfort and pressure sores. This has been the Achilles heel for noninvasive ventilation since day one. Mouth leaks, mask leaks, patient discomfort, and pressure sores are not uncommon—in both the hospital and home care setting. A poor interface compromises clinical efficacy and patient compliance.

“Most problems in compliance stem from interface problems with the mask,” says Lorraine Ramos, RRT, RPsgT, day technologist at North Colorado Medical Center’s sleep laboratory. “I would say 90% of our problems are mask related.”

The Transtracheal Option
The clinical advantages of transtracheal oxygen therapy (TTOT) have been well documented in more than 160 articles in the medical literature. Oxygen flow during rest and with increased activity, as well as bulk oxygen monthly use, is decreased 20% to 50%.^3-6 Patients with TTOT report significantly improved comfort, better self-image, and improved ambulation.^5,7-9 This results in very high patient acceptance (96%)³ and improved compliance with their oxygen therapy. Several studies have documented reduced costs associated with fewer hospitalizations,^5,10,11 and there is data to suggest that patients receiving TTOT have improved survival when compared to well-matched patients receiving oxygen via nasal cannula.¹¹

In fact, TTOT has a 20-year track record of success in benefiting patients on long-term oxygen therapy. Studies done in the late 1980s and early 1990s proved that inspired minute ventilation, physiologic dead space, and the oxygen cost of breathing were all reduced when using transtracheal flow rates of 5 to 8 LPM.^18-20 A most curious finding in these studies was that the aforementioned effects were seen whether the patient was receiving transtracheal flow rates of 100% oxygen, or just room air. This led to speculation that in addition to a physiologic effect (better oxygenation), there may well be a mechanical effect (intratracheal gas flow) that accounts for the many patient reports of decreased shortness of breath while receiving low-flow TTOT.

Almost from its inception, there have been anecdotal reports from TTOT patients that they found it easier to breathe after placement of a SCOOP transtracheal catheter. Patients frequently reported that they had more energy, were sleeping better, and had significant improvements in activities of daily living; and, although they still might develop shortness of breath with activity, they recovered faster. As the anecdotal experience grew with the increasing number of TTOT patients, speculation grew that, indeed, if higher flow rates of an air/oxygen blend could be safely and comfortably introduced into the trachea, further improvements in oxygenation and ventilation might be realized. This became even more apparent when treating a subgroup of severely refractory hypoxemic patients requiring 6 to 22 L of oxygen per minute to achieve adequate oxygen saturations. This group of very challenging patients commonly reported improvements in shortness of breath and clinically appeared to have reduced work-of-breathing following transtracheal catheter insertion.⁴

Transtracheal Augmented Ventilation
Transtracheal augmented ventilationTTAV is the transtracheal delivery of high flows of a heated and humidified air/oxygen blend via a transtracheal catheter. TTAV is an advanced application of standard TTOT in which high flow rates (6 to 15 LPM) are delivered to the patient through a standard SCOOP transtracheal catheter. The equipment necessary to provide TTAV in both the hospital and home is kept as simple as possible. Beyond the catheter, they comprise a heated humidifier with heated wire circuit, a compressor or other source of room air, an oxygen source, and a few commonly available parts to provide a simple, secure connection to the patient.

Although much of the rationale for TTAV is based on anecdotal data, three well-defined clinical applications have been studied and a limited number of abstracts or full papers published.  

Each indication will be discussed individually. Because limited information is available in a few peer-reviewed journals, each of the clinical indications still requires significant further research and clinical investigation before TTAV can be added to a toolbox of mainstream therapies available to help our oxygen-dependent patient population.

Respiratory Insufficiency
COPD affects an estimated 16 million people in the United States and is the fourth leading cause of death exceeded only by heart disease, cancer, and stroke.²¹ The various therapies that have been developed to treat patients with COPD are designed to maintain quality of life by optimizing patients’ activities of daily living and preventing respiratory or ventilatory failure.

Patients with chronic hypoxemia due to COPD are at risk for developing hypercarbic ventilatory failure for a variety of reasons.  Much like NPPV, TTAV (while not technically noninvasive) provides substantial respiratory assistance via a transtracheal catheter. Oxygen-dependent patients receiving low flow oxygen via transtracheal catheter can get the full benefit of improved oxygenation during the day and nocturnal resting of respiratory muscles during the night. This may be due to the fact that TTAV has been shown to reduce minute inspired volume by as much as 50% to 60%.²² Since inspiration is active and requires energy expenditure for inspiratory muscles to contract, it can be appreciated that any decrease in inspired minute ventilation will result in reduced oxygen “cost of breathing.” Much like NPPV, the improved nocturnal rest afforded by TTAV usually results in improved energy levels and an improved quality of life. Nightly rest profoundly affects the quality of the following day’s activities.

Several investigators have independently proven that at flow rates up to 6 LPM, TTOT reduced dyspnea, minute inspiratory ventilation, and dead space, and could be used with higher flow rates (10 LPM) to augment ventilation in selected patients with hypercarbic ventilatory failure.^18-22

Subsequent work by Christopher et al confirmed and verified the reduction in work of breathing by the patient during inspiration, as well as clinically significant reductions in arterial carbon dioxide levels in some patients.^22,24,25 It is in these two primary areas that TTAV compares favorably with NPPV. Since patient compliance with TTOT is essentially 100%, TTAV may offer decided advantages over NPPV in the crucial area of patient compliance with prescribed medical therapy. Clearly, future studies must include comparisons of TTAV and NPPV in well-designed, controlled studies to make scientifically defensible comparisons.

A significant percentage (perhaps as high as 30%) of oxygen-dependent COPD patients suffer from intermittent periods of chronic ventilatory insufficiency, and many of these patients are ideal candidates for TTAV. Additionally, patients who have received TTAV in research applications have subjectively appeared to be more fit, have more energy, sleep better, and have improved quality of life compared to other strategies.²⁷

This is often a challenging group of patients because they may have already completed a pulmonary rehabilitation regime, they may not be candidates for lung reduction surgery or transplant, and yet they complain to their physician that they “can’t breathe.” For patients who meet careful selection criteria, TTAV may be the only new form of therapy available and their last chance to attain an enjoyable quality of life.

TTAV and Weaning
Using conventional weaning strategies (IMV, T-Piece, PSV, etc), many patients frequently complain of dyspnea even before there is any physiologic evidence of respiratory compromise. This may be due to a number of influences, including physiological, mechanical, psychological, and emotional factors. TTAV might be useful in augmenting ventilation in difficult-to-wean patients, especially those who have a tracheostomy due to prolonged periods of mechanical ventilation. A patient who has already been “trached” obviously does not require a transtracheal procedure. Compared to other weaning techniques, COPD patients using TTAV regain the use of their glottis as a regulator of expiratory flow. This is similar to pursed lip breathing to splint the airways. It is not unusual to see the patient’s respiratory rate decrease along with their tidal volume. One of the most important yet overlooked benefits of TTAV is that nearly all patients are able to speak effectively and therefore communicate with both clinicians and family members. It seems reasonable to conclude that the weaning process is further accelerated by the improvement in communication, thus motivating the patient to comply more fully with the rest of their care plan.

Since previous studies have shown that patients receiving TTAV have significant reductions in inspired work-of-breathing,²⁶ the liberation of these challenging patients from the ventilator is probably due to both a reduction of dead space and the introduction of an adjunctive flow of gas through the transtracheal catheter.

Until recently, TTAV for weaning required a slight adaptation to the existing tracheostomy tube. A 5/32-inch hole was drilled through the red cap that is normally used to cap the trach tube. This allowed the introduction of a SCOOP transtracheal catheter and subsequent administration of TTAV. Respironics Inc, which has long been involved in development of traditional BiPAP/CPAP systems, has now developed the Cadence™ product, which works with a proprietary transtracheal catheter to provide high flow, oxygen-enriched, heated, and humidified gas for TTAV. It is intended for use by hard-to-wean patients who have a tracheostomy and are candidates for self-breathing trials and eliminates the necessity for drilling the red cap.

An initial TTAV weaning trial normally begins when the patient’s underlying condition is stabilized enough to begin conventional weaning. The initial trial usually takes 1 to 2 hours, while the patient is continuously monitored by pulse oximetry. A respiratory therapist closely monitors the patient’s clinical status, and blood is drawn for analysis (ABGtest) at the conclusion of the TTAV weaning trial. If the patient tolerates this initial attempt, the time on TTAV is gradually increased, and the time on the ventilator is commensurately decreased. There is a great deal of weaning flexibility available when using TTAV; patients can spend varying amounts of time on both the ventilator and on TTAV. As the patient’s condition continues to improve, a smooth transition from the ventilator to TTAV can be realized.

Clinical experience suggests that most patients prefer this form of weaning to other more traditional techniques,²⁸ and TTAV patients commonly prefer to wait as long as possible before returning to full ventilatory support. Once successfully weaned from the ventilator, the patient may be placed on low-flow transtracheal oxygen during the day and, if necessary, return to TTAV flow rates (8-12 LPM) at night.

If the patient subsequently requires home oxygen, the physician has the option of sending the patient home on a SCOOP oxygen catheter by simply downsizing the trach tube to a #6 or #4, if tolerated. The trach tube can then be pulled, and a SCOOP catheter can be inserted into the stoma, allowing the tracheostomy stoma to close down around the catheter. When the transtracheal tract is fully mature, the patient effectively becomes a “routine” TTOT patient, using low flow oxygen during the day to maintain oxygen saturations and, if necessary, TTAV at night for ventilatory assist. This low-flow to high-flow regimen provides resting of the patient’s muscles of ventilation overnight, allowing the patient to have more energy for the next day’s activities of daily living.

Experience with TTAV in the postacute phase of mechanical ventilation indicates that TTAV can be an effective tool for weaning patients who require minimal ventilatory support but who are unable to sustain unsupported ventilation for prolonged periods of time or cannot get over the hurdle of the last few centimeters of pressure support ventilation. “We’ve had a lot of patients that we were able to take off the vents, or were able to prevent them from going on to begin with,” says North Colorado Medical Center’s Ramos. “Coming in [to the hospital] with a TTOT catheter put them ahead of the game because they had another option [to intubation].” TTAV can be a natural “bridge” in moving the patient from the hospital to the home.

TTAV in the Treatment of OSA
Since first described in the 1980s, CPAP and its derivative bilevel PAP have become the first-line treatment for patients with obstructive sleep apnea (OSA). As discussed previously, the patient/mask interface is one of the biggest obstacles to patient compliance. Subjective reports based on patient diaries suggest compliance ranges between 65% and 90%.²³ Actual measurements using timers built into some devices (to measure actual use) showed a much poorer compliance, however. Kribbs et al²³ found that only 46% of patients used their CPAP for at least 4 hours per night, 5 nights per week. There is little difference in compliance rates utilizing various bilevel devices.

A number of surgical and nonsurgical alternative therapies have been developed over the years with varying degrees of success. In spite of advances in surgical techniques, overall success rates for surgical interventions such as uvulopalatopharyngoplasty (UPPP) continue to be at or near 50%. While tracheostomy is 100% effective, it causes a significant decrease in quality of life and presents its own set of complications. Weight loss, position training, pharmacologic interventions, electrical stimulation, and nasal splints have all been tried with variable and generally limited success.

Low-flow transtracheal oxygen therapy in the treatment of OSA was first evaluated by Spofford and Christopher in 1985. Later studies done by Farney and Elmer²⁸ and Chauncey and Aldrich²⁹ presented preliminary findings showing low-flow transtracheal oxygen therapy to be a potentially useful alternative in treating OSA patients who either could not or would not tolerate CPAP therapy as prescribed by their physicians.

The flow of gas into the trachea below the obstruction through a transtracheal catheter presumably increases mean airway pressure, which would increase functional residual capacity, thereby increasing the cross-sectional area of the hypopharynx relieving the obstruction. Instead of delivering a predetermined pressure to a mask, effectively blowing the airway open from above, as with CPAP, a high flow of humidified gas (air, oxygen, or air/oxygen mix) is delivered below the obstruction, reversing the pressure gradient and opening the airway from below. There might also be other neurally transmitted factors yet to be identified that might play a role in regulating the collapsed airway that are positively affected by TTAV. Even if the OSA patient continues to have obstructive episodes, oxygen is continuously delivered through the catheter below the obstruction, maintaining oxygen saturations even during obstructive episodes.³⁰

Anecdotal observations have indicated that OSA patients treated with transtracheal catheters maintain more consistent oxygen saturations throughout the night. It is not unusual for patients treating their OSA with TTAV to have already tried and failed CPAP/bilevel PAP therapy. They commonly report that their daytime symptoms improve in much the same way they did while on CPAP/bilevel PAP, without the discomfort associated with mask therapy. Many of these patients have considered and refused surgical interventions (UPPP), mandibular displacement devices, or full tracheostomy. Titrating an OSA patient for TTAV also requires a sleep study in a hospital setting, and flow rates in excess of 10 LPM are not unusual, depending on the patient’s individual requirements.

“I’ve seen it work on several patients, but some still have snoring and arousals associated with hypopneas,” says Ramos. “But for the patients it worked on, it worked wonderfully.” There were also some challenges for home care providers making the necessary high flows available in the home, she notes. The chief advantage of TTAV over CPAP/bilevel PAP is in greatly improved patient compliance.

Back to the Future
Transtracheal oxygen therapy has been available in the treatment of chronic hypoxemia for more than 20 years, as a valid alternative to the nasal cannula for patients requiring continuous supplemental oxygen. In the past 10 years, a number of investigators have studied the ventilatory effects of transtracheal oxygen, including the use of high transtracheal flow rates (6 to 15 LPM). Other gases such as heliox and nitric oxide have already been delivered through a SCOOP catheter to treat a variety of pathophysiologic conditions or diseases with promising results. Significant further study needs to be performed to evaluate which patients are most likely to benefit from TTAV. Technical application aspects need to be refined, so that commercially available TTAV delivery devices are both patient and clinician friendly, as well as economically viable.

In time, TTAV may prove to be a viable new mode of augmented ventilation that physicians can consider for patients who are easily oxygenated at low oxygen flow rates, yet continue to complain of dyspnea and increased work of breathing.

John A. Wolfe, RRT, CPFT, is a clinical specialist at North Colorado Medical Center, Greeley, Colo, and a member of RT’s editorial advisory board.

References
1. Lightowler JV, Jadwiga AW, Wedzicha A, Elliot MW, Ram FS. Non-invasive positive pressure ventilation to treat respiratory failure resulting from exacerbations of chronic obstructive pulmonary disease: Cochrane systematic review and meta-analysis. BMJ. 2003; 326:185

2. Heimlich, HJ. Respiratory rehabilitation with transtracheal oxygen system.  Ann Otol Rhinol Laryngo. 1982; 91:643-7.

3. Christopher KL, Spofford BT, Petrun MD, McCarty DC, Goodman JR, Petty TL. A program for transtracheal oxygen delivery: assessment of safety and efficacy. Ann Intern Med. 1987; 107:802-8.

4. Christopher KL, Spofford BT, Brannin PK, Petty TL. Transtracheal oxygen therapy for refractory hypoxemia. JAMA. 1986; 256: 494-7.

5. Hoffman LA, Wesmiller SW, Sciurba FC, Johnson JT, Ferson PF Zullo TB, Dauber JH.  Nasal cannula and transtracheal oxygen delivery; a comparison of patient response following 6 months use of each technique.  Am Rev Respir Dis. 1992; 145:827-31.

6. Yaeger ES, Goodman S, Hoddes E, Christopher KL. Oxygen therapy using pulse and continuous flow with a transtracheal catheter and a nasal cannula. Chest. 1994; 106:854-60.