Ambulatory Long-Term Oxygen Therapy in Patients with Severe COPD: A Randomized Crossover Trial to Compare Constant-Minute-Volume and Constant-Bolus Systems

Figures & data

Table 1 Titration Algorithm for Establishing the Operating Level of Each Oxygen-Conserving Device (OCD)

SpO2 After 6MWT w/o O2 (%)	Recommended Continuous O2 Flow (l/min)°	mL/Breath or mL/min on OCD	Setting for Constant Bolus Device [mL/breath; mL/min]^	Setting for Constant Minute Volume System [mL/breath; mL/min]^
86–89	2	27/667	3 [33; 825]	4 [33,6; 840]
80–85	3	40/1000	4 [42; 1050]	5 [42; 1050]
74–79	4	X	5*	5*
≤73	5	X	5*	5*

Notes: °Modified according to;³ *In cases where SpO₂ was <80% after exercise without supplemental oxygen, but the patient wished to participate further according to protocol, the device was set to the maximum level or titrated to a resting SpO₂ of 92–95%, in line with standard clinical practice; ^adapted to an expected breathing frequency of 25/min.

Abbreviations: SpO₂, peripheral oxygen saturation; w/o, without; OCD, oxygen-conserving device.

Figure 1 Study flow chart according to CONSORT for crossover randomized trials.

Table 2 Patient Characteristics at Baseline

Characteristics	n = 25
Age [years]	67.9 ± 7.8
Female [%]	56%
FEV1 after bronchodilation [%pred]	27.3 ± 8.4
FVC [%pred]	45 ± 11.6
FEV1/FVC ratio [%]	47.1 ± 14.2
TLC [%pred]	114.2 ± 39.7
RV [%pred]	185.9 ± 79.5
KCO [%]	50.4 ± 25.4
TLCO [%]	30.7 ± 12.6
Cumulative smoking dosage [pack years]*	48.8 ± 22.2
BMI [kg/m^2]	25.6 ± 7.7
pH	7.42 ± 0.04
PaO2 at rest without oxygen [mmHg]	50.3 ± 5.9
PaCO2 [mmHg]	48.9 ± 6.2
HCO3^−[mmol/l]	29.8 ± 3.2

Notes: *14 patients were ex-smokers (56%) and 11 patients were current smokers (44%).

Abbreviations: FEV_1, forced expiratory volume in 1 second; FVC, forced vital capacity; RV, residual volume; TLC, total lung capacity; BMI, body mass index; PaO_2, arterial partial pressure of oxygen; PaCO_2, arterial partial pressure of carbon dioxide; HCO₃⁻, standard hydrogen carbonate.

Figure 2 Continued.

Figure 2 (a) mean operating level of investigated devices after exercise. 1: 6MWT with constant bolus device. 2: 6MWT with constant minute volume device. (b) mean walking distance in 6-minute walking test for each device. 1: 6MWT with constant bolus device. 2: 6MWT with constant minute volume device. (c) mean breathing frequency in breaths/minute after exercise. 1: 6MWT with constant bolus device. 2: 6MWT with constant minute volume device. (d) mean difference in dyspnea before and after exercise for each device. 1: pre 6MWT with constant bolus device. 2: post 6MWT with constant bolus device. 3: pre 6MWT with constant minute volume device. 4: post 6MWT with constant minute volume device. (e) mean oxygen saturation in % before and after exercise with each device. 1: pre 6MWT with constant bolus device. 2: post 6MWT with constant bolus device. 3: pre 6MWT with constant minute volume device. 4: post 6MWT with constant minute volume device.

Figure 3 The two devices under investigation (constant-bolus- system and constant-minute-volume system) and their ability to reach success criteria.

Hardinge M, Annandale J, Bourne S, et al. British Thoracic Society guidelines for home oxygen use in adults: accredited by NICE. Thorax. 2015;70(Suppl 1):i1–i43. doi:10.1136/thoraxjnl-2015-206865

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