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Comparison of Two Demand Oxygen Delivery Devices for Administration of Oxygen in COPD
Comparison of Two Demand Oxygen Delivery Devices for Administration of Oxygen in COPD* Stefan Langenhof, MD; and Joachim Fichter, MD, PhD
Aim: Demand oxygen delivery systems (DODSs) were developed to secure the mobility of patients requiring oxygen therapy. The aim of the present study was to compare the efficacy of two currently available DODS with continuous oxygen administration (CONT). Patients: Thirteen patients with COPD (mean [ⴞ SD] FEV1, 28 ⴞ 5.2% predicted; mean PO2, 56.4 ⴞ 8.1 mm Hg [breathing room air]). Intervention: Treatment for 30 min with CONT at a flow rate of 2 L/min, with the DODSs Oxytron 3 (Weinmann; Hamburg, Germany) or DeVilbiss EX 3000 (Somerset, PA) in random sequence. Arterialized blood samples were obtained from a hyperaemized ear lobe after 15 and 30 min. Results: After 15 min, no significant differences in PO2 or arterial oxygen saturation (SaO2) were observed. In comparison with CONT (mean PO2, 70.5 ⴞ 10.4 mm Hg; mean SaO2, 94.8 ⴞ 2.13%), oxygenation with the Oxytron 3 (mean PO2, 66.3 ⴞ 10.3 mm Hg; mean SaO2, 93.5 ⴞ 2.6%) was significantly less after 30 min when measured independently by blood gas analysis and pulse oximetry. The DeVilbiss EX 3000 (mean PO2, 69.1 ⴞ 12.0 mm Hg; mean SaO2, 94.5 ⴞ 3.2%) and CONT showed no differences. Conclusions: PO2 did not reach equilibrium after 15 min of treatment with the DODSs. The titration of a patient to a DODS is recommended, since simply accepting the manufacturer’s information on oxygen equivalent does not guarantee an adequate supply of oxygen. (CHEST 2005; 128:2082–2087) Key words: COPD; oxygen delivery and consumption; oxygen therapy Abbreviations: CONT ⫽ continuous oxygen administration; DODS ⫽ demand oxygen delivery system; Sao2 ⫽ arterial oxygen saturation
long-term oxygen therapy was proT hevidedbasisbyforstudies from the Nocturnal Oxygen Therapy Trial Group1 and the Medical Research Council Working Party,2 published in 1980 and 1981, respectively, which demonstrated that the duration of the daily application of oxygen is associated with a survival advantage for chronically hypoxemic COPD patients who were receiving long-term oxygen therapy. With continuous long-term oxygen therapy via nasal prongs appreciably more oxygen is used up than is actually needed, since only a portion of the oxygen delivered reaches the patient’s alveoli. In view of the widespread application of long-term *From the Paracelsus Hospital, Osnabrueck, Germany. Manuscript received June 2, 2004; revision accepted March 9, 2005. Reproduction of this article is prohibited without written permission from the American College of Chest Physicians (www.chestjournal. org/misc/reprints.shtml). Correspondence to: Joachim Fichter, MD, PhD, Paracelsus Hospital, Am Natruper Holz 69, 49076 Osnabrueck, Germany; e-mail: [email protected] 2082
oxygen therapy, oxygen is a substantial cost factor. With regard to the mobile oxygen option, more effective utilization of the limited amount of oxygen available is of significance for the range of the device, and thus for patient mobility.3– 6 This requirement prompted the development of oxygen conservation methods and resulted in demand oxygen systems (DODSs) that, triggered by the patient’s inspiration, deliver oxygen only in the inspiratory phase. Further optimization of such DODSs can be achieved with the aid of pulse systems. These systems deliver an oxygen bolus only in the early part of the inspiratory effort. Since this bolus is delivered at high speed, the portion of the breath that actually reaches the alveoli contains a higher concentration of oxygen than the fraction filling the anatomic dead space. From the numerous DODS devices that are available, most of which had never been clinically tested, we selected two different types that are in widespread use. They were selected to investigate the exemplary validity of the manufacturers’ recommendations in comparison with continuous oxygen adClinical Investigations
Figure 1. Po2 (from arterialized blood) after 15 min of treatment with CONT, the Oxytron 3, and the DeVilbis EX 3000 in comparison with breathing room air.
ministration (CONT). Thus, the study aimed to answer the following questions: are the oxygenconserving devices equally as effective as CONT in COPD patients?; and are the manufacturers’ recommendations valid? Materials and Methods Patients Thirteen patients with COPD who were receiving long-term oxygen therapy were investigated. Oxygen was applied via nasal prongs. The group of patients comprised 10 men and 3 women between the ages of 53 and 81 years, with a mean (⫾ SD) age of 65.2 ⫾ 8.3 years (mean FEV1, 28 ⫾ 5.2% predicted; mean FEV1/ FVC ratio, 49.33 ⫾ 8.33%; mean height, 166.5 ⫾ 7.4 cm; mean weight, 69.5 ⫾ 8.3 kg). Inclusion criteria were COPD treated with long-term oxygen and a stable COPD phase (ie, no exacerbations within the last 4 weeks). Exclusion criteria were severe cardiovascular disease or other clinical findings that could possibly affect oxygen tolerance. Oxygen-Conserving Devices The Oxytron 3 DODS (Weinmann; Hamburg, Germany) measures 75 ⫻ 136 ⫻ 45 mm and weighs approximately 330 g. Oxygen bolus delivery can be selected via seven settings, ranging from 10 to 70 mL. Thus, setting 1, for example, provides a bolus of 10 mL of oxygen per breath. The oxygen is applied in the early phase of inspiration and requires 50 ms for the delivery of each 10 mL of oxygen, which corresponds to a flow rate of 12 L/min. According to the manufacturer’s handbook, 1 L of CONT is www.chestjournal.org
equivalent to settings 1 to 2 on the device, while settings 2 to 3 are said to correspond to 2 L of CONT. The DeVilbiss EX 3000 (Somerset, PA) is a DODS measuring 107 ⫻ 65 ⫻ 28 mm and weighing 225 g. Oxygen delivery can be regulated in 11 steps, ranging from 0.5 to 6 L/min. According to the manufacturer’s handbook, the flow setting of 2 L/min corresponds to a bolus of 33 mL of oxygen per breath. The maximum pulse volume of the Devilbiss EX 3000 was 100 mL at a flow rate of 10 L/min, compared with 70 mL at a flow rate of 12 L/min for the Oxytron 3 device. Both manufacturers claim that the maximum pulse of the DODS is equivalent to 6 L/min of CONT. Accordingly, different pulse volumes of 20 mL (Oxytron 3) and 33 mL (DeVilbiss EX 3000) were chosen as the equivalent to 2 L/min of CONT. The oxygen source was a liquid oxygen container. Arterialized blood gas samples taken from the hyperaemized ear lobe by experienced staff were analyzed (ABL 700; Radiometer; Copenhagen, Denmark). All measurements were carried out under conditions of rest, and all measurements in the respective patients were made on the same day. At the same time, arterial oxygen saturation (Sao2) [model N-3000; Nellcor; Pleasanton, CA] was measured using continuous pulse oximetry and was recorded at each blood gas determination. The following measurements were performed: blood gas levels at rest without oxygen delivery; and blood gas levels after 15 and 30 min of treatment with 2 L/min CONT, with the Oxytron 3 set to 2 and the DeVilbiss EX 3000 set to 2, in random sequence. Between CONT and the use of the respective oxygen-conserving device, oxygen delivery was interrupted for 10 min. With the aid of the Kolmogorov-Smirnov test for continuous data, the results were tested for normal distribution. Since the data were bound parametric and normally distributed data, for which repeated measurement of identical parameters under differing experimental conditions were investigated, the variance analysis for repeated measurements was applied. CHEST / 128 / 4 / OCTOBER, 2005
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Table 1—PO2 of Arterialized Blood after 15 min of Treatment With CONT, the Oxytron 3, and the DeVilbiss EX 3000 in Comparison With Room Air in Individual Patients Po2, mm Hg Patient No. 1 2 3 4 5 6 7 8 9 10 11 12 13 Mean SD
Without Oxygen
2 L/min CONT
Oxytron 3
Devilbiss EX 3000
70.8 46.2 65.1 54.0 45.7 52.3 49.0 58.7 48.7 68.0 58.1 59.7 57.2 56.4 8.1
86.8 57.2 83.5 79.5 58.7 62.8 61.8 54.0 61.5 84.9 99.9 76.3 66.5 71.8 14.2
76.1 49.3 71.7 73.3 54.4 68.7 58.3 64.8 55.1 74.1 66.7 81.1 64.0 66.0 9.5
82.4 45.3 72.9 77.2 49.2 67.0 61.5 55.2 66.1 74.3 72.4 80.4 64.4 66.8 11.6
Results The mean Po2 on initiating measurements at rest without oxygen administration was 56.4 ⫾ 8.1 mm Hg. The mean Sao2 was 89.9 ⫾ 4.1%, as measured by blood gas analysis, and 90.2 ⫾ 3.5%, as determined by pulse oximetry.
After 15 min of CONT, the mean Po2 was 71.8 ⫾ 14.2 mm Hg. After 15 min of oxygen administration via both the Oxytron 3 (mean Po2, 66.0 ⫾ 9.5 mm Hg) and the DeVilbiss EX 3000 (mean Po2, 66.8 ⫾ 11.6 mm Hg), the Po2 was lower (Fig 1, Table 1), but the differences were not significant. A comparison of the two DODSs revealed no trend or significant difference after 15 min. The mean Sao2 by blood gas analysis was 94.3 ⫾ 2.7% (by pulse oximetry, 94.5 ⫾ 2.6%) for CONT, 93.5 ⫾ 2.9% (by pulse oximetry, 93.8 ⫾ 2.7%) with the Oxytron 3, and 93.2 ⫾ 4.0% (by pulse oximetry, 94.1 ⫾ 3.0%) with the DeVilbiss EX 3000 (Fig 2, Table 2). The differences were not significant. After 30 min of CONT, the mean Po2 was 70.5 ⫾ 10.4 mm Hg. The Oxytron 3 was associated with a Po2 of 66.3 ⫾ 10.3 mm Hg, and the DeVilbiss EX 3000 with a Po2 of 69.1 ⫾ 12.0 mm Hg (Fig 3, Table 3). Thus, with CONT of 2 L in comparison with the Oxytron 3 at setting 2, a significantly higher oxygen Po2 (p ⬍ 0.05) was to be found, which after 15 min presented only as a trend. A comparison between CONT at a flow of 2 L/min and oxygen delivery via the DeVilbiss EX 3000 at setting 2 revealed no significant difference. However, a significant difference (p ⬍ 0.05) was to be seen between the two oxygen-conserving devices in terms of Po2, with a higher Po2 seen for oxygen delivery via the
Figure 2. Sao2 (from pulse oximetry) after 15 min of treatment with CONT, the Oxytron 3, and the DeVilbis EX 3000 in comparison with breathing room air. 2084
Clinical Investigations
Table 2—SaO2 (by Pulse Oximetry) After 15 min of Treatment with CONT, the Oxytron 3, and the DeVilbiss EX 3000 in Comparison With Room Air in Individual Patients
Table 3—PO2 of Arterialized Blood After 30 min of Treatment With CONT, the Oxytron 3, and the DeVilbiss EX 3000 in Comparison With Room Air in Individual Patients
Sao2, % Patient No. 1 2 3 4 5 6 7 8 9 10 11 12 13 Mean SD
Po2, mm Hg
Without Oxygen
2 L/min CONT
Oxytron 3
Devilbiss EX 3000
94 86 94 90 82 89 90 94 89 94 90 92 89 90.2 3.5
95 92 98 98 90 92 95 91 96 96 97 96 93 94.5 2.7
93 88 96 96 89 95 93 96 93 96 94 97 93 93.8 2.7
97 86 96 95 91 92 93 93 96 96 95 96 95 94,0 3.0
DeVilbiss EX 3000. The mean Sao2 with blood gases (Fig 4, Table 4) was 94.4 ⫾ 2.4% (by pulse oximetry, 94.8 ⫾ 2.13%) for CONT, 93.3 ⫾ 2.8% (by pulse oximetry, 93.5 ⫾ 2.6%) with the Oxytron 3, and 93.8 ⫾ 4.0% (by pulse oximetry, 94.5 ⫾ 3.2%) with the DeVilbiss EX 3000. A significant difference
Patient No. 1 2 3 4 5 6 7 8 9 10 11 12 13 Mean SD
Without Oxygen
2 L/min CONT
Oxytron 3
Devilbiss EX 3000
70.8 46.2 65.1 54.0 45.7 52.3 49.0 58.7 48.7 68.0 58.1 59.7 57.2 56.4 8.1
81.7 54.4 70.8 73.0 59.2 61.7 61.1 63.4 66.9 82.0 89.0 78.5 74.2 70.5 10.4
78.9 50.7 72.3 77.3 54.6 64.0 56.4 60.1 56.0 74.7 71.3 81.7 63.8 66.3 10.3
84.8 46.9 73.6 83.1 51.4 65.1 62.6 63 64.3 75.1 81.4 80.9 66.2 69.1 12.0
(p ⬍ 0.05) was shown, both by blood gas analysis and pulse oximetry, between treatment with CONT and the Oxytron 3 device. After 15 and 30 min of oxygen administration, no significant difference or trend was to be seen with regard to Pco2. With CONT, the mean Pco2 was
Figure 3. Po2 (from arterialized blood) after 30 min of treatment with CONT, the Oxytron 3, and the DeVilbis EX 3000 in comparison with breathing room air. There was a significantly lower Po2 with the Oxytron 3 in comparison with CONT and the DeVilbiss EX 3000. www.chestjournal.org
CHEST / 128 / 4 / OCTOBER, 2005
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Figure 4. Sao2 (from pulse oximetry) after 30 min of treatment with CONT, the Oxytron 3, and the DeVilbiss EX 3000 in comparison with breathing room air. There was a significantly lower Sao2 with the Oxytron 3 in comparison with CONT.
51.8 ⫾ 8.7 mm Hg (Oxytron 3, 52.8 ⫾ 8.1 mm Hg; DeVilbiss EX 3000, 52.3 ⫾ 8.5 mm Hg). With CONT and with the DeVilbiss EX 3000, the recommended target Po2 of ⬎ 60 mm Hg with long-term oxygen therapy7 was achieved in 11 of 13
Table 4 —SaO2 (by Pulse Oximetry) After 30 min of Treatment With CONT, the Oxytron 3, and the DeVilbiss EX 3000 in Comparison With Room Air in Individual Patients Sao2, % Patient No. 1 2 3 4 5 6 7 8 9 10 11 12 13 Mean SD
2086
Without Oxygen
2 L/min CONT
Oxytron 3
Devilbiss EX 3000
94 86 94 90 82 89 90 94 89 94 90 92 89 90.2 3.5
97 91 95 95 92 91 95 95 96 96 97 97 95 94.8 2.1
94 88 95 96 89 93 94 93 93 96 94 97 93 93.5 2.6
97 85 96 97 92 93 95 95 96 96 96 96 94 94,5 3.2
patients (84.6%). With the Oxytron 3, a Po2 of ⬎ 60 mm Hg was achieved in only 9 of 13 patients (69.2%). Discussion For an assessment of the efficacy of the DODSs in COPD patients, two devices were compared with CONT by blood gas analysis and pulse oximetry. It was found that, on average, arterial Po2 and Sao2 were elevated to a desirable level. Oxygen treatment with the DeVilbiss EX 3000 achieved the same Po2 as with CONT at an oxygen flow rate of 2 L/min at 15 and 30 min. In comparison with CONT, oxygenation achieved with the Oxytron 3 after 30 min was significantly less, as measured independently with blood gas analysis and pulse oximetry. Decisive features of practical importance for the application of a DODS are adequate oxygen delivery, equipment reliability, patient tolerability and acceptance, ease of use, and mobility range. A DODS does indeed provide the patient with an adequate supply of oxygen. With the DeVilbiss EX 3000, the provision of oxygen was comparable with that achieved with CONT. With the Oxytron 3, fewer patients were adequately provided with oxygen (Po2, ⬎ 60 mm Hg). This might be due to the lower pulse volume selected on the Oxytron 3. The flow rate with Clinical Investigations
the Oxytron 3 was, however, higher. Oxygenation depends not only on the size of the oxygen pulse volume, but also on the speed of the bolus delivery and the triggering latency.8 The faster the bolus is delivered, the more efficiently is the oxygen made available for gas exchange in the alveoli.9 The maximum range of the pulse volumes of the two devices differed. According to the manufacturers, the maximum pulse equivalent to 6 L/min CONT was 100 mL in the Devilbiss EX 3000 and 70 mL in the Oxytron 3. Therefore, we chose different pulse volumes on account of the different technical features of the devices and the different recommendations of the manufacturers to provide a maximum range of mobility for the patient. In practice, a DODS is unlikely to supply the patient with too little oxygen if, prior to prescribing such a device, the oxygen delivery is titrated. When a DODS is being titrated, oxygen should be administered for ⬎ 15 min before a blood gas analysis is performed, since the Po2 continues to increase between the 15 and 30 min of use. This is also in conformity with the results of other publications,7,10 in which oxygen equilibrium was established only after 30 min. In other studies, measurements were carried out after only 10 min11 or 15 min.12 In this study, we have been able to show that oxygen-conserving devices can provide hypoxemic patients with an adequate supply of oxygen at rest. The manufacturer’s data on flow equivalency cannot always be translated to the individual patient, with the result that the patient may not receive sufficient oxygen. In the case of the DeVilbiss EX 3000, setting 2 at rest corresponds to CONT of 2 L/min. With the Oxytron 3, the present data suggest that for the equivalency of 2 L/min CONT a higher setting must be selected more often. Measurements should be obtained after ⬎ 15 min of oxygen administration by the DODSs to appropriately assess the effectiveness of the settings. We are aware that the differences we found were obtained under resting conditions, although DODSs are used mainly under exercise conditions. Under
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exercise conditions, these differences might be even more pronounced, but under exercise conditions the results are not predictable from data obtained at rest, due to, for example, different breathing frequencies in COPD patients. Further studies of these widely used DODSs for severe patients COPD should therefore be performed under exercise conditions. In conclusion, we found differences even under resting conditions between two of the numerous types of DODS devices that are available.
References 1 Nocturnal Oxygen Therapy Trial Group. Continuous or nocturnal oxygen therapy in hypoxemic chronic obstructive lung disease: a clinical trial. Ann Intern Med 1980; 93:391–398 2 Medical Research Council Working Party. Long term domiciliary oxygen therapy in chronic hypoxic cor pulmonale complicating chronic bronchitis and emphysema. Lancet 1981; 1: 681– 868 3 Leach RM, Davidson AC, Chinin S, et al. Portable liquid oxygen and exercise ability in severe respiratory disability. Thorax 1992; 47:781–789 4 Tiep BL, Lewis MI. Oxygen conservation and oxygen-conserving devices in chronic lung disease. Chest 1987; 92:263– 272 5 Carter R, Tashin D, Djahed B, et al. Demand oxygen delivery for patients with restrictive lung disease. Chest 1989; 96: 1307–1311 6 Rinow ME, Saltzman AR. Effectiveness of a new oxygen demand valve in chronic hypoxemia. Chest 1986; 90:204 –207 7 American Thoracic Society and European Respiratory Society. Standards for the diagnosis and management of patients with COPD. Available at: www.thoracic.org/copd. Accessed February 8, 2004 8 Fichter J, Johann U, Sybrecht GW. Efficacy of demand oxygen delivery systems in patients with chronic obstructive lung disease. Pneumologie 2001; 55:306 –310 9 Tiep BL, Christopher KL, Spofford BT, et al. Pulsed nasal and transtracheal oxygen delivery. Chest 1990; 97:364 –368 10 Bowner JS, Brook CJ, Zimmer K, et al. Performance of a demand oxygen saver system during rest, exercise, and sleep in hypoxemic patients. Chest 1988; 94:77– 80 11 Tiep BL, Carter R, Nicotra MB, et al. Demand oxygen delivery during exercise. Chest 1987; 91:15–20 12 Tiep BL, Nicotra MB, Carter R, et al. B. Low-concentration oxygen therapy via a demand oxygen delivery system. Chest 1985; 87:636 – 638
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Aim: Demand oxygen delivery systems (DODSs) were developed to secure the mobility of patients requiring oxygen therapy. The aim of the present study was to compare the efficacy of two currently available DODS with continuous oxygen administration (CONT). Patients: Thirteen patients with COPD (mean [ⴞ SD] FEV1, 28 ⴞ 5.2% predicted; mean PO2, 56.4 ⴞ 8.1 mm Hg [breathing room air]). Intervention: Treatment for 30 min with CONT at a flow rate of 2 L/min, with the DODSs Oxytron 3 (Weinmann; Hamburg, Germany) or DeVilbiss EX 3000 (Somerset, PA) in random sequence. Arterialized blood samples were obtained from a hyperaemized ear lobe after 15 and 30 min. Results: After 15 min, no significant differences in PO2 or arterial oxygen saturation (SaO2) were observed. In comparison with CONT (mean PO2, 70.5 ⴞ 10.4 mm Hg; mean SaO2, 94.8 ⴞ 2.13%), oxygenation with the Oxytron 3 (mean PO2, 66.3 ⴞ 10.3 mm Hg; mean SaO2, 93.5 ⴞ 2.6%) was significantly less after 30 min when measured independently by blood gas analysis and pulse oximetry. The DeVilbiss EX 3000 (mean PO2, 69.1 ⴞ 12.0 mm Hg; mean SaO2, 94.5 ⴞ 3.2%) and CONT showed no differences. Conclusions: PO2 did not reach equilibrium after 15 min of treatment with the DODSs. The titration of a patient to a DODS is recommended, since simply accepting the manufacturer’s information on oxygen equivalent does not guarantee an adequate supply of oxygen. (CHEST 2005; 128:2082–2087) Key words: COPD; oxygen delivery and consumption; oxygen therapy Abbreviations: CONT ⫽ continuous oxygen administration; DODS ⫽ demand oxygen delivery system; Sao2 ⫽ arterial oxygen saturation
long-term oxygen therapy was proT hevidedbasisbyforstudies from the Nocturnal Oxygen Therapy Trial Group1 and the Medical Research Council Working Party,2 published in 1980 and 1981, respectively, which demonstrated that the duration of the daily application of oxygen is associated with a survival advantage for chronically hypoxemic COPD patients who were receiving long-term oxygen therapy. With continuous long-term oxygen therapy via nasal prongs appreciably more oxygen is used up than is actually needed, since only a portion of the oxygen delivered reaches the patient’s alveoli. In view of the widespread application of long-term *From the Paracelsus Hospital, Osnabrueck, Germany. Manuscript received June 2, 2004; revision accepted March 9, 2005. Reproduction of this article is prohibited without written permission from the American College of Chest Physicians (www.chestjournal. org/misc/reprints.shtml). Correspondence to: Joachim Fichter, MD, PhD, Paracelsus Hospital, Am Natruper Holz 69, 49076 Osnabrueck, Germany; e-mail: [email protected] 2082
oxygen therapy, oxygen is a substantial cost factor. With regard to the mobile oxygen option, more effective utilization of the limited amount of oxygen available is of significance for the range of the device, and thus for patient mobility.3– 6 This requirement prompted the development of oxygen conservation methods and resulted in demand oxygen systems (DODSs) that, triggered by the patient’s inspiration, deliver oxygen only in the inspiratory phase. Further optimization of such DODSs can be achieved with the aid of pulse systems. These systems deliver an oxygen bolus only in the early part of the inspiratory effort. Since this bolus is delivered at high speed, the portion of the breath that actually reaches the alveoli contains a higher concentration of oxygen than the fraction filling the anatomic dead space. From the numerous DODS devices that are available, most of which had never been clinically tested, we selected two different types that are in widespread use. They were selected to investigate the exemplary validity of the manufacturers’ recommendations in comparison with continuous oxygen adClinical Investigations
Figure 1. Po2 (from arterialized blood) after 15 min of treatment with CONT, the Oxytron 3, and the DeVilbis EX 3000 in comparison with breathing room air.
ministration (CONT). Thus, the study aimed to answer the following questions: are the oxygenconserving devices equally as effective as CONT in COPD patients?; and are the manufacturers’ recommendations valid? Materials and Methods Patients Thirteen patients with COPD who were receiving long-term oxygen therapy were investigated. Oxygen was applied via nasal prongs. The group of patients comprised 10 men and 3 women between the ages of 53 and 81 years, with a mean (⫾ SD) age of 65.2 ⫾ 8.3 years (mean FEV1, 28 ⫾ 5.2% predicted; mean FEV1/ FVC ratio, 49.33 ⫾ 8.33%; mean height, 166.5 ⫾ 7.4 cm; mean weight, 69.5 ⫾ 8.3 kg). Inclusion criteria were COPD treated with long-term oxygen and a stable COPD phase (ie, no exacerbations within the last 4 weeks). Exclusion criteria were severe cardiovascular disease or other clinical findings that could possibly affect oxygen tolerance. Oxygen-Conserving Devices The Oxytron 3 DODS (Weinmann; Hamburg, Germany) measures 75 ⫻ 136 ⫻ 45 mm and weighs approximately 330 g. Oxygen bolus delivery can be selected via seven settings, ranging from 10 to 70 mL. Thus, setting 1, for example, provides a bolus of 10 mL of oxygen per breath. The oxygen is applied in the early phase of inspiration and requires 50 ms for the delivery of each 10 mL of oxygen, which corresponds to a flow rate of 12 L/min. According to the manufacturer’s handbook, 1 L of CONT is www.chestjournal.org
equivalent to settings 1 to 2 on the device, while settings 2 to 3 are said to correspond to 2 L of CONT. The DeVilbiss EX 3000 (Somerset, PA) is a DODS measuring 107 ⫻ 65 ⫻ 28 mm and weighing 225 g. Oxygen delivery can be regulated in 11 steps, ranging from 0.5 to 6 L/min. According to the manufacturer’s handbook, the flow setting of 2 L/min corresponds to a bolus of 33 mL of oxygen per breath. The maximum pulse volume of the Devilbiss EX 3000 was 100 mL at a flow rate of 10 L/min, compared with 70 mL at a flow rate of 12 L/min for the Oxytron 3 device. Both manufacturers claim that the maximum pulse of the DODS is equivalent to 6 L/min of CONT. Accordingly, different pulse volumes of 20 mL (Oxytron 3) and 33 mL (DeVilbiss EX 3000) were chosen as the equivalent to 2 L/min of CONT. The oxygen source was a liquid oxygen container. Arterialized blood gas samples taken from the hyperaemized ear lobe by experienced staff were analyzed (ABL 700; Radiometer; Copenhagen, Denmark). All measurements were carried out under conditions of rest, and all measurements in the respective patients were made on the same day. At the same time, arterial oxygen saturation (Sao2) [model N-3000; Nellcor; Pleasanton, CA] was measured using continuous pulse oximetry and was recorded at each blood gas determination. The following measurements were performed: blood gas levels at rest without oxygen delivery; and blood gas levels after 15 and 30 min of treatment with 2 L/min CONT, with the Oxytron 3 set to 2 and the DeVilbiss EX 3000 set to 2, in random sequence. Between CONT and the use of the respective oxygen-conserving device, oxygen delivery was interrupted for 10 min. With the aid of the Kolmogorov-Smirnov test for continuous data, the results were tested for normal distribution. Since the data were bound parametric and normally distributed data, for which repeated measurement of identical parameters under differing experimental conditions were investigated, the variance analysis for repeated measurements was applied. CHEST / 128 / 4 / OCTOBER, 2005
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Table 1—PO2 of Arterialized Blood after 15 min of Treatment With CONT, the Oxytron 3, and the DeVilbiss EX 3000 in Comparison With Room Air in Individual Patients Po2, mm Hg Patient No. 1 2 3 4 5 6 7 8 9 10 11 12 13 Mean SD
Without Oxygen
2 L/min CONT
Oxytron 3
Devilbiss EX 3000
70.8 46.2 65.1 54.0 45.7 52.3 49.0 58.7 48.7 68.0 58.1 59.7 57.2 56.4 8.1
86.8 57.2 83.5 79.5 58.7 62.8 61.8 54.0 61.5 84.9 99.9 76.3 66.5 71.8 14.2
76.1 49.3 71.7 73.3 54.4 68.7 58.3 64.8 55.1 74.1 66.7 81.1 64.0 66.0 9.5
82.4 45.3 72.9 77.2 49.2 67.0 61.5 55.2 66.1 74.3 72.4 80.4 64.4 66.8 11.6
Results The mean Po2 on initiating measurements at rest without oxygen administration was 56.4 ⫾ 8.1 mm Hg. The mean Sao2 was 89.9 ⫾ 4.1%, as measured by blood gas analysis, and 90.2 ⫾ 3.5%, as determined by pulse oximetry.
After 15 min of CONT, the mean Po2 was 71.8 ⫾ 14.2 mm Hg. After 15 min of oxygen administration via both the Oxytron 3 (mean Po2, 66.0 ⫾ 9.5 mm Hg) and the DeVilbiss EX 3000 (mean Po2, 66.8 ⫾ 11.6 mm Hg), the Po2 was lower (Fig 1, Table 1), but the differences were not significant. A comparison of the two DODSs revealed no trend or significant difference after 15 min. The mean Sao2 by blood gas analysis was 94.3 ⫾ 2.7% (by pulse oximetry, 94.5 ⫾ 2.6%) for CONT, 93.5 ⫾ 2.9% (by pulse oximetry, 93.8 ⫾ 2.7%) with the Oxytron 3, and 93.2 ⫾ 4.0% (by pulse oximetry, 94.1 ⫾ 3.0%) with the DeVilbiss EX 3000 (Fig 2, Table 2). The differences were not significant. After 30 min of CONT, the mean Po2 was 70.5 ⫾ 10.4 mm Hg. The Oxytron 3 was associated with a Po2 of 66.3 ⫾ 10.3 mm Hg, and the DeVilbiss EX 3000 with a Po2 of 69.1 ⫾ 12.0 mm Hg (Fig 3, Table 3). Thus, with CONT of 2 L in comparison with the Oxytron 3 at setting 2, a significantly higher oxygen Po2 (p ⬍ 0.05) was to be found, which after 15 min presented only as a trend. A comparison between CONT at a flow of 2 L/min and oxygen delivery via the DeVilbiss EX 3000 at setting 2 revealed no significant difference. However, a significant difference (p ⬍ 0.05) was to be seen between the two oxygen-conserving devices in terms of Po2, with a higher Po2 seen for oxygen delivery via the
Figure 2. Sao2 (from pulse oximetry) after 15 min of treatment with CONT, the Oxytron 3, and the DeVilbis EX 3000 in comparison with breathing room air. 2084
Clinical Investigations
Table 2—SaO2 (by Pulse Oximetry) After 15 min of Treatment with CONT, the Oxytron 3, and the DeVilbiss EX 3000 in Comparison With Room Air in Individual Patients
Table 3—PO2 of Arterialized Blood After 30 min of Treatment With CONT, the Oxytron 3, and the DeVilbiss EX 3000 in Comparison With Room Air in Individual Patients
Sao2, % Patient No. 1 2 3 4 5 6 7 8 9 10 11 12 13 Mean SD
Po2, mm Hg
Without Oxygen
2 L/min CONT
Oxytron 3
Devilbiss EX 3000
94 86 94 90 82 89 90 94 89 94 90 92 89 90.2 3.5
95 92 98 98 90 92 95 91 96 96 97 96 93 94.5 2.7
93 88 96 96 89 95 93 96 93 96 94 97 93 93.8 2.7
97 86 96 95 91 92 93 93 96 96 95 96 95 94,0 3.0
DeVilbiss EX 3000. The mean Sao2 with blood gases (Fig 4, Table 4) was 94.4 ⫾ 2.4% (by pulse oximetry, 94.8 ⫾ 2.13%) for CONT, 93.3 ⫾ 2.8% (by pulse oximetry, 93.5 ⫾ 2.6%) with the Oxytron 3, and 93.8 ⫾ 4.0% (by pulse oximetry, 94.5 ⫾ 3.2%) with the DeVilbiss EX 3000. A significant difference
Patient No. 1 2 3 4 5 6 7 8 9 10 11 12 13 Mean SD
Without Oxygen
2 L/min CONT
Oxytron 3
Devilbiss EX 3000
70.8 46.2 65.1 54.0 45.7 52.3 49.0 58.7 48.7 68.0 58.1 59.7 57.2 56.4 8.1
81.7 54.4 70.8 73.0 59.2 61.7 61.1 63.4 66.9 82.0 89.0 78.5 74.2 70.5 10.4
78.9 50.7 72.3 77.3 54.6 64.0 56.4 60.1 56.0 74.7 71.3 81.7 63.8 66.3 10.3
84.8 46.9 73.6 83.1 51.4 65.1 62.6 63 64.3 75.1 81.4 80.9 66.2 69.1 12.0
(p ⬍ 0.05) was shown, both by blood gas analysis and pulse oximetry, between treatment with CONT and the Oxytron 3 device. After 15 and 30 min of oxygen administration, no significant difference or trend was to be seen with regard to Pco2. With CONT, the mean Pco2 was
Figure 3. Po2 (from arterialized blood) after 30 min of treatment with CONT, the Oxytron 3, and the DeVilbis EX 3000 in comparison with breathing room air. There was a significantly lower Po2 with the Oxytron 3 in comparison with CONT and the DeVilbiss EX 3000. www.chestjournal.org
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Figure 4. Sao2 (from pulse oximetry) after 30 min of treatment with CONT, the Oxytron 3, and the DeVilbiss EX 3000 in comparison with breathing room air. There was a significantly lower Sao2 with the Oxytron 3 in comparison with CONT.
51.8 ⫾ 8.7 mm Hg (Oxytron 3, 52.8 ⫾ 8.1 mm Hg; DeVilbiss EX 3000, 52.3 ⫾ 8.5 mm Hg). With CONT and with the DeVilbiss EX 3000, the recommended target Po2 of ⬎ 60 mm Hg with long-term oxygen therapy7 was achieved in 11 of 13
Table 4 —SaO2 (by Pulse Oximetry) After 30 min of Treatment With CONT, the Oxytron 3, and the DeVilbiss EX 3000 in Comparison With Room Air in Individual Patients Sao2, % Patient No. 1 2 3 4 5 6 7 8 9 10 11 12 13 Mean SD
2086
Without Oxygen
2 L/min CONT
Oxytron 3
Devilbiss EX 3000
94 86 94 90 82 89 90 94 89 94 90 92 89 90.2 3.5
97 91 95 95 92 91 95 95 96 96 97 97 95 94.8 2.1
94 88 95 96 89 93 94 93 93 96 94 97 93 93.5 2.6
97 85 96 97 92 93 95 95 96 96 96 96 94 94,5 3.2
patients (84.6%). With the Oxytron 3, a Po2 of ⬎ 60 mm Hg was achieved in only 9 of 13 patients (69.2%). Discussion For an assessment of the efficacy of the DODSs in COPD patients, two devices were compared with CONT by blood gas analysis and pulse oximetry. It was found that, on average, arterial Po2 and Sao2 were elevated to a desirable level. Oxygen treatment with the DeVilbiss EX 3000 achieved the same Po2 as with CONT at an oxygen flow rate of 2 L/min at 15 and 30 min. In comparison with CONT, oxygenation achieved with the Oxytron 3 after 30 min was significantly less, as measured independently with blood gas analysis and pulse oximetry. Decisive features of practical importance for the application of a DODS are adequate oxygen delivery, equipment reliability, patient tolerability and acceptance, ease of use, and mobility range. A DODS does indeed provide the patient with an adequate supply of oxygen. With the DeVilbiss EX 3000, the provision of oxygen was comparable with that achieved with CONT. With the Oxytron 3, fewer patients were adequately provided with oxygen (Po2, ⬎ 60 mm Hg). This might be due to the lower pulse volume selected on the Oxytron 3. The flow rate with Clinical Investigations
the Oxytron 3 was, however, higher. Oxygenation depends not only on the size of the oxygen pulse volume, but also on the speed of the bolus delivery and the triggering latency.8 The faster the bolus is delivered, the more efficiently is the oxygen made available for gas exchange in the alveoli.9 The maximum range of the pulse volumes of the two devices differed. According to the manufacturers, the maximum pulse equivalent to 6 L/min CONT was 100 mL in the Devilbiss EX 3000 and 70 mL in the Oxytron 3. Therefore, we chose different pulse volumes on account of the different technical features of the devices and the different recommendations of the manufacturers to provide a maximum range of mobility for the patient. In practice, a DODS is unlikely to supply the patient with too little oxygen if, prior to prescribing such a device, the oxygen delivery is titrated. When a DODS is being titrated, oxygen should be administered for ⬎ 15 min before a blood gas analysis is performed, since the Po2 continues to increase between the 15 and 30 min of use. This is also in conformity with the results of other publications,7,10 in which oxygen equilibrium was established only after 30 min. In other studies, measurements were carried out after only 10 min11 or 15 min.12 In this study, we have been able to show that oxygen-conserving devices can provide hypoxemic patients with an adequate supply of oxygen at rest. The manufacturer’s data on flow equivalency cannot always be translated to the individual patient, with the result that the patient may not receive sufficient oxygen. In the case of the DeVilbiss EX 3000, setting 2 at rest corresponds to CONT of 2 L/min. With the Oxytron 3, the present data suggest that for the equivalency of 2 L/min CONT a higher setting must be selected more often. Measurements should be obtained after ⬎ 15 min of oxygen administration by the DODSs to appropriately assess the effectiveness of the settings. We are aware that the differences we found were obtained under resting conditions, although DODSs are used mainly under exercise conditions. Under
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exercise conditions, these differences might be even more pronounced, but under exercise conditions the results are not predictable from data obtained at rest, due to, for example, different breathing frequencies in COPD patients. Further studies of these widely used DODSs for severe patients COPD should therefore be performed under exercise conditions. In conclusion, we found differences even under resting conditions between two of the numerous types of DODS devices that are available.
References 1 Nocturnal Oxygen Therapy Trial Group. Continuous or nocturnal oxygen therapy in hypoxemic chronic obstructive lung disease: a clinical trial. Ann Intern Med 1980; 93:391–398 2 Medical Research Council Working Party. Long term domiciliary oxygen therapy in chronic hypoxic cor pulmonale complicating chronic bronchitis and emphysema. Lancet 1981; 1: 681– 868 3 Leach RM, Davidson AC, Chinin S, et al. Portable liquid oxygen and exercise ability in severe respiratory disability. Thorax 1992; 47:781–789 4 Tiep BL, Lewis MI. Oxygen conservation and oxygen-conserving devices in chronic lung disease. Chest 1987; 92:263– 272 5 Carter R, Tashin D, Djahed B, et al. Demand oxygen delivery for patients with restrictive lung disease. Chest 1989; 96: 1307–1311 6 Rinow ME, Saltzman AR. Effectiveness of a new oxygen demand valve in chronic hypoxemia. Chest 1986; 90:204 –207 7 American Thoracic Society and European Respiratory Society. Standards for the diagnosis and management of patients with COPD. Available at: www.thoracic.org/copd. Accessed February 8, 2004 8 Fichter J, Johann U, Sybrecht GW. Efficacy of demand oxygen delivery systems in patients with chronic obstructive lung disease. Pneumologie 2001; 55:306 –310 9 Tiep BL, Christopher KL, Spofford BT, et al. Pulsed nasal and transtracheal oxygen delivery. Chest 1990; 97:364 –368 10 Bowner JS, Brook CJ, Zimmer K, et al. Performance of a demand oxygen saver system during rest, exercise, and sleep in hypoxemic patients. Chest 1988; 94:77– 80 11 Tiep BL, Carter R, Nicotra MB, et al. Demand oxygen delivery during exercise. Chest 1987; 91:15–20 12 Tiep BL, Nicotra MB, Carter R, et al. B. Low-concentration oxygen therapy via a demand oxygen delivery system. Chest 1985; 87:636 – 638
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