The LTOT Continuum

• By Patrick J. Dunne
• Apr 15, 2008

Four different situations where LTOT would be prescribed

Beginning in 1967, the use of continuous long-term oxygen therapy (LTOT) for the treatment of chronic arterial hypoxemia secondary to obstructive lung disease has been well-established in numerous peer review scientific publications.

When properly prescribed and administered, LTOT has been shown to prolong life, reduce the incidence acute exacerbations, forestall the onset of co-morbid conditions, (most notably pulmonary hypertension and cor pulmonale), and lead to an overall improvement in the quality of life.

More recent evidence suggests that clinical outcomes are even better when continuous LTOT is used in conjunction with other controller medications and a regular regimen of daily exercise, such as walking with ambulatory oxygen. As the incidence of chronic obstructive pulmonary disease (COPD) continues to increase, the demand for LTOT is sure to increase as well

Uses of LTOT
It is important to realize that when LTOT is prescribed for a patient, the primary clinical objective is to elevate (and maintain) an arterial oxygen tension = 60 mm Hg, or alternatively, SpO2 = 90 percent. It is also important to ensure that these blood oxygen levels are maintained over a 24-hour period, regardless of a patient’s type or level of activity. Whenever a patient desaturates below the aforementioned oxygen levels, whether it be unintentional or otherwise, the clinical advantages of LTOT are compromised.

To reduce the likelihood of unintentional desaturation, it is helpful to think about LTOT use in terms of a continuum: a series of locations where, and conditions under which, LTOT is used. One could argue there are at least four unique situations where prescribed LTOT will be used:
1.    Daily, in-home.
2.    Ambulation beyond the reaches of the stationary system.
3.    During sleep.
4.    At altitude.
Daily in-home use
For daily in-home use, the objective is to provide adequate oxygenation during all domiciliary activities of daily living, such as bathing and dressing, meal preparation, light housework and other domestic pursuits. Typically this need is met with any of the traditional continuous flow stationary systems, commonly used with the 7 foot nasal cannula connected to an extension supply tube.

During ambulation
When LTOT is used during ambulation, patients go beyond the limits of the stationary system. This need is met by providing a lightweight ambulatory or portable delivery system. Patient activities during ambulation would range from casual or extended walking to a program of structured exercise, such as participation in a formal pulmonary rehabilitation program.

For some patients, an increase in activity level may result in an increase in systemic oxygen demand. To prevent activity-induced desaturation in this patient population, it is therefore important that the ambulatory device being used is capable of delivering higher doses of oxygen than what was required during in-home resting use. The use of a pulse oximeter during a particular activity can help establish the required oxygen dose, especially with a continuous flow device.

If the ambulatory device being used incorporates pulsed-dose technology, it is even more essential that a titration study be performed to ensure the device is capable of meeting a patient’s higher oxygen needs. It may be, that even at its highest setting, the oxygen output a given pulse-dose device cannot meet patient demand and another delivery system will need to be substituted.

During Sleep
When LTOT is used during sleep, the objective is to protect the patient from nocturnal desaturation, which in this setting, would be secondary to one or more sleep disorders adversely affecting ventilation. Such disorders could range from mild to very severe. The elderly in general, simply as a function of the aging process, suffer some degree of sleep disruption. Elderly patients with COPD experience even more sleep issues, and the challenges are magnified even more so when obstructive sleep apnea (OSA) exists as a co-morbid condition.

For COPD patients not suffering from OSA, it has always been assumed that the continuous flow stationary system protected against nocturnal desaturation. However, evidence is somewhat sketchy that the oxygen dose used during the waking hours (e.g. 2 LPM) provides the same degree of protection during all stages of sleep. As an additional safeguard, some physicians now instruct their patients to increase their continuous flow setting during sleep.

For those COPD patients with OSA, a sleep study should be performed to determine the level of continuous or bi-level positive airway pressure needed. The positive airway pressure device is then used in conjunction with continuous flow oxygen.

The proliferation of portable oxygen concentrators (POCs) that can only operate in the pulse-dose mode has raised important questions about the effectiveness of these devices during sleep. Skeptics suggest that the alterations in breathing frequency and depth that occur during the various stages of sleep may out-pace the oxygen delivery capabilities of a “pulse-dose only POC” and result in nocturnal desaturation. The questions are sure to intensify as the use of these devices as a single source LTOT delivery system grows. However, in the interest of patient safety and until solid evidence suggests otherwise, continuous flow LTOT is probably best during sleep. At the very least, if a “pulse-dose only POC” is to be used during sleep, patients should have an overnight oximetry study to establish the nighttime setting and to confirm the absence of nocturnal desaturation.

At Altitude
The final step on the LTOT continuum is altitude and these would be patients flying in a commercial airliner or driving to altitude for a brief or extend stay. Until recently, air travel represented a major challenge for LTOT users, but the introduction of the aforementioned POCs changed all of that, and for the better.

The portability and varied power source options that these devices offer now allows LTOT patients the opportunity to travel wherever they want, whenever they want and however they want. However, as mentioned previously, not all “pulse-dose only POCs” have the same oxygen production capabilities, so the effect of altitude on the performance of a given unit must be taken into account. A particular “pulse-dose only POC” may work very well at sea level, but not so at altitude.

Summary
Properly prescribed and dosed LTOT represents an important component for the control and maintenance of COPD symptoms. For best results, the LTOT equipment must have the capabilities to provided sufficient oxygen in all settings and under all conditions where a patient will need protection from desaturation. Newer technology, especially POCs, is making it easier for chronically hypoxemic COPD patients to engage in a wide array of activities in myriad settings.

However, the equipment will only be as good as the efforts expended by the home care provider to achieve optimal interface between patient and the selected technology, and to ensure the patient is protected from desaturation across the entire LTOT continuum.

This article originally appeared in the April 2008 issue of HME Business.