Mean room air oxygen saturation was not significantly different for each delivery method. The mean respiratory rates were 16.2 ± 4.0 at rest and 19.5 ± 5.1 at the end of exercise. Oxygen saturation and the amount of oxygen required to produce adequate saturation each minute for all subjects, from each trial, using both oxygen delivery techniques, are shown in Table 2. All saturation readings were recorded at the end of the three minute exercise session. In most cases, both steady flow and the DODS were able to provide the subjects with enough oxygen to meet their physiologic needs during low-level exercise. However, much more oxygen was required using steady flow delivery than the DODS to achieve adequate oxygen saturation.
The performance curves of steady flow and DODS oxygen delivery are shown in Figure 2. At 90 percent saturation, the oxygen supply requirement was 211.4 ml/min for the DODS as contrasted to steady flow which was 1,610.9 ml/min. Therefore, the mean oxygen savings benefit of the DODS over steady flow delivery is 7.6:1 with a range of 3.95:1 (subject 6) to better than 10:1 (subject 3). These differences are statistically significant (p<.0001). A comparison of oxygen utilization at 90 percent saturation for each delivery method is shown in Figure 3. Again, substantially more oxygen is required using steady flow delivery, as opposed to DODS delivery, to achieve equivalent oxygen saturation.
This study demonstrates that the demand oxygen delivery system can provide adequate oxygenation at a substantially reduced supply during exercise conditions. The oxygen savings using the DODS as compared to steady flow delivery is greater than 7 to 1. These results are consistent with the findings of our earlier study which demonstrated a comparable 7 to 1 savings during resting conditions. The fact that the oxygen savings using the DODS extends to exercise conditions lends support to its use in portable oxygen therapy. To know more about diseases you may here and also about different types of treatment and drugs.
One of the important areas of oxygen therapy, particularly in the home, is portable oxygen therapy. Many of the major problems encountered in oxygen therapy appear to be magnified in portable oxygen therapy. The weight, bulk, appearance, comfort and cost of oxygen therapy take on increasing importance. If less oxygen is required, then the oxygen storage cannister, which the patient must carry, can be less bulky and will weigh less. While portable systems, both gas and liquid, are designed to be carried over the shoulders, patients with chronic lung disease are often too weak and debilitated to carry their oxygen and therefore require the aid of a wheeled cart. These carts increase the weight and decrease the maneuverability of portable oxygen, particularly when the patient must drive. A reduction in oxygen supply needs to Yr the previous requirement could help increase the range of the present systems and reduce the necessary size of the oxygen cannister, thus permitting an increased range of activity.
An important benefit of oxygen conservation is the cost savings afforded by the reduction in oxygen usage over a given time, as shown in Figure 3. A patient who requires 2 L/min of continuous oxygen and is using compressed gas at home will require 12.5 K-cylinders at $30.00 per cylinder each month, (typical for the Los Angeles area). The total monthly charge is $375.00. If that same patient could be treated adequately with Yi as much oxygen, the number of oxygen cylinders per month could be reduced to 1.8. The cost of oxygen would be $54.00. However, the DODS could rent for as much as $50.00 per month which would bring the monthly charge for oxygen to $104.00. Thus, the actual savings would be $271.00 per month, or the proportionate benefit would be 3.6:1 over steady flow. That patient, under portable conditions, would be using compressed gas cylinders. The popular E-cylinder exchanges for about $16.00 per cylinder and lasts about five hours at 2 L/min of steady flow delivery or 35 hours via the DODS.
Liquid oxygen is often more expensive than compressed gas and there are several factors to consider when making cost comparisons. The DODS is designed to operate using liquid oxygen systems with oxygen savings similar to compressed gas delivery.
Patients using oxygen concentrators have no need for oxygen-conserving devices while on low-flow stationary oxygen. However, when such patients use portable oxygen, they usually have backup E-cylinders. If these patients use 14 cylinders per month at $16.00 per cylinder, the cost for the portable oxygen alone would be $224.00. This would have a negative impact on the use of the oxygen concentrator. With the DODS, only two E-cylinders would be required per month which would reduce the cost of portable oxygen to $32.00. Adding the DODS monthly rental charge of $50.00, the cost of portable oxygen in these patients would be $82.00 which improves the financial viability of the combination oxygen concentrator and portable compressed gas cylinders.
With the advent of increased public awareness and scrutiny of health care costs, such a reduction in oxygen requirement should be welcome. The average, per patient, cqst of home oxygen is about $350 per month. When that cost by is multiplied by an estimated 300,000 patients on home oxygen, the cost is $105 million per month or $1.26 billion per year. While there are some fixed costs, the use of oxygen-conserving devices and techniques might make it possible to reduce the cost of oxygen therapy to 30-40 percent of the present level.
The fact that the DODS can provide substantial savings in oxygen utilization as compared to steady flow delivery is predictable. Steady flow oxygen is delivered throughout the respiratory cycle even though a majority of the cycle is spent in exhalation and a substantial portion of inhalation is spent in filling the deadspace. Thus, an estimated 20 percent of the original steady flow oxygen would be expected to contribute to the overall oxygenation of the patients blood. Therefore, in order to maximize the efficiency of oxygen delivery, a reasonable goal is to direct all oxygen delivery exclusively to the earliest part of inhalation so as to avoid wasting oxygen.
An additional factor favoring early inspiratory oxygen delivery in the emphysema patient is the concept of fast space vs slow space ventilation. The fast space, according to the concept, fills during the earliest part of inhalation and is well perfused with pulmonary, circulation. In contrast, the slow space, being last to fill, is also poorly perfused. Early inspiratory oxygen delivery would favor filling the fast space, thus providing more efficient arterial oxygenation. This effect would vary depending upon the ventilation/perfusion matching of the individual patient.
With the DODS, the volume of oxygen delivered is determined by altering the frequency with which breaths are supplemented with oxygen from the supply source. The frequency may vary from setting 1 which provides oxygen for only one of four consecutive breaths, to setting 4 during which each breath is supplemented. If a patient on setting 1 breathed 16 breaths per minute, that patient would receive only four oxygen delivery pulses per minute. Our observations did not reveal any disadvantages in intermittent oxygen delivery in the patient whose oxygen requirements were minimal. On the contrary, their oxygen saturations were equivalent to steady flow saturations at 1 L/min.
Methods of reducing oxygen usage, aside from electronic demand systems, are transtracheal and reservoir cannulas. In both of these techniques, oxygen is introduced early in inspiration and oxygen can be conserved because of the lower supply flows necessary to accomplish adequate oxygen saturation. In the transtracheal method, oxygen is introduced directly into the trachea. Lower oxygen flows provide adequate oxygen saturation because oxygen is stored in the trachea toward the end of exhalation and substantial deadspace is bypassed. Oxygen savings between 2:1 and 3:1 have been reported. A significant advantage of transtracheal oxygen delivery is the fact that the delivery catheter can be hidden from view and thus may be more appealing cosmetically.
Reservoir cannulas save oxygen by storing it in a closely coupled reservoir during exhalation so that the stored oxygen, along with the continuous, but greatly reduced, supply oxygen, can be delivered during inhalation. There are two configurations of reservoir cannulas, one with the reservoir under the nose in the mustache region (Oxymizer) and the other with the reservoir hanging on the front wall of the chest as a sort of pendant (Oxymizer Pendant). Both reservoir cannulas accomplish oxygen savings of between 2:1 and 4:1 as compared to steady flow with the savings extending to exercise conditions.’ Long-term studies suggest that the reservoir cannula is reliable during extended use. The reservoir of the mustache-configured cannula is rather noticeable and some patients find it aesthetically displeasing. The reservoir of the pendant cannula is located on the anterior chest wall which alleviates some of the appearance problem, but is still noticeable.
Since the DODS maintains a high savings ratio during both rest and exercise, it is possible that smaller oxygen systems, lighter in weight and less bulky, could be developed which would further increase the portability and convenience of portable oxygen therapy. Moreover, since the DODS uses a standard steady flow nasal cannula, it does not suffer the cosmetic disadvantage of some of the reservoir cannulas.
Some oxygen-savings devices, particularly the reservoir cannulas, are in widespread use; transtracheal oxygen delivery is seeing greater use as well. Each oxygen conservation approach carries its own set of advantages and drawbacks. Since all of these methods are presently available and are used in patient care, we feel that the clinician should be aware of the advantages and disadvantages of each to best assist the patient in choosing the most appropriate alternative to meet their individual needs. For example, transtracheal delivery is least noticeable, but requires a surgical procedure; reservoir cannulas are the simplest and most reliable, but most noticeable as well; electronic demand systems are most efficacious; however, as mechanical systems are more complicated, one might expect mechanical failure or patient misuse would be more likely, although we had no such problem with our devices.
We conclude that the DODS can save substantial amounts of oxygen during not only resting conditions but exercise conditions as well, lending support to its use in portable oxygen therapy. This oxygen savings can be translated into significant cost savings and, perhaps equally important, the ability to improve the range and portability of oxygen therapy by allowing the use of smaller oxygen cannisters. Increased portability may contribute to improving the quality of life in patients requiring continuous oxygen therapy. We recommend long-term studies to confirm both the reliability and cost savings using the DODS.
|Subj Age||Steady Flow||DODS|
|THal 1||Trial 2||THal 1||THal 2|
Figure 2. Mean oxygen saturations at two oxygen supply settings of steady flow and demand oxygen delivery (DODS). Readings were taken at the end of 3 minutes of equivalent exercise.
Figure 3. Histogram comparison of the mean oxygen supply requirements of demand (DODS) and steady flow oxygen delivery required to achieve an oxygen saturation of 90%. Much less oxygen supply is required to achieve the oxygen saturation of 90% using DODS delivery (p<.0001).