Accuracy of Medical Oxygen Flowmeters: A Multicentric Field Study

Duprez, Frédéric; Barile, Maria; Bonus, Thierry; Cuvelier, Grégory; Ollieuz, Sandra; Mashayekhi, Shahram; Legrand, Alexandre

doi:10.4236/health.2014.615232

Cited by 11 publications

(11 citation statements)

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“…In practice, use of our prediction formula was difficult because the exact patient V I value was unknown and O 2 flow meters have a low accuracy. [27][28][29] Moreover, in this study, the V I used was continuous (rectangular form). However, the human V I wave is not continuous (waveform).…”

Section: Study Limitationsmentioning

confidence: 99%

A New Formula for Predicting the Fraction of Delivered Oxygen During Low-Flow Oxygen Therapy

et al. 2018

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BACKGROUND: During O 2 therapy at low flow in patients who breathe spontaneously, the fraction of delivered O 2 (F DO 2 ) is unknown. In recent years, F DO 2 prediction formulas have been proposed. However, they do not take into account the effect of inspiratory flow (V I ) on the F DO 2 . The aim of this study was to validate a new F DO 2 prediction formula, which takes into account the V I and compares it with other F DO 2 prediction formulas. METHODS: During a bench study, spontaneous breathing was generated with a mechanical test lung connected to a mechanical ventilator set to volume control mode. O 2 flow from a wall-mounted tube was delivered through a heat-and-moisture exchanger filter. A flow sensor recorded each breath of the V I in ambient temperature and barometric pressure conditions. Three parameters [O 2 flow at 2, 3, 4, 5, 6 L/min; minute ventilation at 5, 10, 15, 20 L/min; and ratio of the inspiratory time (T I ) to the total breathing cycle time (T tot ) (T I /T tot ) of 0.33 (T I /T tot value) and 0.50 (T I /T tot value)] were modified to generate many ventilatory patterns. An O 2 analyzer continuously examined the F DO 2 . RESULTS: When the O 2 flow and/or T I /T tot increased, the F DO 2 increased. When the minute ventilation increased, the F DO 2 decreased. The results of the Bland-Altman method for the F DO 2 , calculated by using our mathematical model and the measured F DO 2 , showed that the mean ؎ SD bias value was equal to 1.49 ؎ 0.84%, and the limits of agreement ranged from ؊0.17% to 3.14%. The intraclass correlation coefficients were 0.991 for T I /T tot ‫؍‬ 0.33 and 0.994 for T I /T tot ‫؍‬ 0.50, and the coefficient of variation was 2.1% for T I /T tot ‫؍‬ 0.33 and 1.3% for T I /T tot ‫؍‬ 0.50. The results of the Bland-Altman method for the F DO 2 calculated by using the Shapiro formula and the F DO 2 measured on the bench indicated that the bias value was 0.075 ؎ 8.66% and the limits of agreement ranged from ؊16.89% to 17.04%. For the Vincent formula, the bias value was 3.08% ؎ 8.56% and the limits of agreement ranged from ؊13.69% to 19.84%. CONCLUSIONS: The V I has a major impact on F DO 2 during O 2 therapy at low flow. F DO 2 comparisons between frequently used prediction formulas and F DO 2 measured on the bench indicated greater differences. Uncritical use of these formulas should be used cautiously to predict F DO 2 . In this study, our prediction formula indicated a good accuracy for predicting F DO 2 during supplemental oxygenation through a heat-and-moisture exchanger in patients who breathe spontaneously.

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Section: Study Limitationsmentioning

confidence: 99%

A New Formula for Predicting the Fraction of Delivered Oxygen During Low-Flow Oxygen Therapy

et al. 2018

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“…Furthermore, the coefficient of variation in the study by Davidson et al (91 Thorpe tubes analyzed) was 0.6 (Ϯ0.5) and 0.11 (Ϯ0.01) for the study by Duprez et al (476 Thorpe tubes analyzed). 7,8 In our study, the coefficient of variation was 0.08 (Ϯ0.02) for single-stage and 0.07 (Ϯ0.01) for dual-stage. These differences of variability between oxygen cylinder flow meters and Thorpe tubes could be due to the red y compact (accuracy Ϯ1% for oxygen flow; range 0.5-20 L/min), which is a very accurate measuring instrument, whereas Davidson et al used a Timeter RT-200 (Allied Healthcare Products, St. Louis, Missouri; accuracy Ϯ4% for oxygen flow; range 0.5-10 L/min).…”

Section: Discussionmentioning

confidence: 46%

“…ϭ 476) showed median values of oxygen flow ranging from 91% to 110% of required flow. 7 The dispersion of the measurements is greater with Thorpe tubes than with oxygen cylinder flow meters. With the single-stage, but not for dual-stage, median values of oxygen flow were lower with low gas pressure than with high gas pressure.…”

Section: Discussionmentioning

confidence: 99%

“…These results are consistent with two previous papers that analyzed the accuracy of the flow of Thorpe tubes in a hospital. 7,8 The conclusion of these studies was that the Thorpe tubes tested showed poor accuracy. On the other hand, our results revealed that oxygen cylinders have less variability of flow than Thorpe tubes, which means that the accuracy of oxygen cylinder flow meters is better than that of Thorpe tubes.…”

Section: Discussionmentioning

confidence: 99%

“…Recent studies have examined the accuracy of Thorpe tubes in clinical situations. 7,8 They observed that the required flow was different from the delivered flow using Thorpe tube. This difference can lead to over-or under-oxygenation of patients, which can be deleterious in various conditions, such as COPD, ischemic disorders, and for premature infants.…”

Section: Introductionmentioning

confidence: 99%

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