Abstract
BACKGROUND: It is difficult to apply noninvasive ventilation (NIV) simultaneously with pulsed-dose oxygen delivery. We evaluated the feasibility and efficacy of pulsed-dose oxygen delivery during NIV.
METHODS: A bench study was conducted using a simulated lung during NIV, with a breathing frequency of 10 or 20 breaths/min and 3 oxygen injection sites (site A on face mask, site B proximal to face mask, and site C at the ventilator outlet) with continuous flow oxygen delivery of 1, 3, or 5 L/min) or pulsed-dose oxygen delivery (numerical settings of 1, 3, or 5 representing the oxygen pulse characteristics). under different experimental conditions and the influence of mode of oxygen delivery on NIV (compared to baseline and continuous flow oxygen delivery vs pulsed-dose oxygen delivery) were compared. In the clinical study, we enrolled 10 subjects with COPD exacerbation who received NIV with either continuous flow oxygen delivery or pulsed-dose oxygen delivery. Under the same targeted pulse oxygen saturation (88–92%), the numerical settings of different modes of oxygen delivery were titrated, and the clinical parameters during the different modes of oxygen delivery were compared.
RESULTS: In the bench study, the ratio of the with pulsed-dose oxygen delivery to the with continuous flow oxygen delivery at the same numerical setting was 0.94 ± 0.15. The oxygen injection site had a significant influence on in pulsed-dose oxygen delivery or continuous flow oxygen delivery mode (P < .05). Pulsed-dose oxygen delivery worked effectively with the ventilator, as demonstrated by the fine synchronization in the breathing cycle of the ventilator, the simulated lung, and the pulsed-dose oxygen delivery. When compared with each other or compared to the baseline individually, pulsed-dose oxygen delivery and continuous flow oxygen delivery showed no clinically important effects on NIV (all P > .05 or changes < 10%). In the clinical study, the mean numerical settings for pulsed-dose oxygen delivery and continuous flow oxygen delivery modes after titration were 2.68 ± 0.32 and 2.31 ± 0.56 L/min, respectively. There was no significant difference between continuous flow oxygen delivery and pulsed-dose oxygen delivery (P > .05).
CONCLUSIONS: Integration of pulsed-dose oxygen delivery into NIV could achieve efficacy similar to that achieved with continuous flow oxygen delivery.
- noninvasive ventilation
- pulsed-dose oxygen delivery
- continuous flow oxygen delivery
- respiratory simulation system
Introduction
Recent studies have reported that an increasing number of patients with chronic respiratory failure receive home noninvasive ventilation (NIV); further, home NIV has been shown to improve clinical symptoms, enhance the quality of life, and reduce mortality.1–3 A number of studies have demonstrated the beneficial effects of home oxygen therapy as well.4–6 Oxygen concentrators are widely used for patients in the home or are coupled with a noninvasive ventilator due to its portability and cost savings compared to oxygen tanks (gaseous or liquid), especially in resource-constrained settings.7 To improve the efficacy of oxygen delivery, most portable oxygen concentrators employ pulsed-dose oxygen delivery technology.8 The efficacy of both home oxygen therapy and home NIV is directly proportional to the duration of daily use. Currently many available types of portable noninvasive ventilators or oxygen concentrators can meet the needs of patients who receive home NIV or home oxygen therapy, respectively, whether at home, in the out-patient setting, or during transport.9
An estimated 30% patients with chronic respiratory failure need simultaneous home oxygen therapy and home NIV.9 These patients require a portable oxygen concentrator that can simultaneously work with a portable ventilator. The technology can reduce the financial costs compared to other oxygen sources such as oxygen tanks (gaseous or liquid); in addition, this enables patients to continue simultaneous oxygen therapy and ventilation support during ambulation, travel, and outdoor activities, which improves treatment adherence. In additional, this technology is useful in specific conditions such as in remote areas and during military operations or air travel.
An anecdotal report suggests that portable oxygen concentrators and portable noninvasive ventilators are incompatible for concomitant use as the function of the oxygen concentrator is affected by interference from the portable noninvasive ventilator with pulsed trigger signal to the oxygen concentrator.9 However, other studies indicate that pulsed-dose oxygen delivery may work effectively with ambulant ventilators after modification of the trigger mechanism.7,10,11 Additionally, a new ventilator (VOCSN, Ventec LifeSystems, Bothell, Washington), which has a single-limb circuit with an active valve and works with the built-in pulse-dosed setting of the concentrator, has been approved in the United States. However, it is not clear whether pulsed-dose oxygen delivery can be integrated with a noninvasive ventilator with a passive valve after adjusting the trigger mechanism to meet the requirements of patients on both NIV and oxygen therapies.
In this study, we performed both a bench study and a clinical study to investigate the feasibility and efficacy of integration of pulsed-dose oxygen delivery into a portable noninvasive ventilator after adjusting the trigger mechanism through a data wire to transmit trigger signals between the 2 devices.
QUICK LOOK
Current knowledge
Chronic respiratory failure is a common health problem. Affected patients frequently require both noninvasive ventilation and oxygen therapy. Previous studies have suggested that it might be difficult to apply noninvasive ventilation and pulsed-dose oxygen delivery simultaneously.
What this paper contributes to our knowledge
Results from both a bench study and a clinical study indicate that pulsed-dose oxygen supply could be applied to a noninvasive ventilator. Pulsed-dose and continuous-flow oxygen delivery showed similar efficacy.
Methods
This investigation included both a bench study and a clinical study, which both were performed between March 2017 and July 2018.
Bench Study
Simulated Oxygen Delivery During NIV.
The active simulated lung (ASL5000, Ingmar, Pittsburgh, Pennsylvania) is a high-fidelity respiratory simulator that includes a computer-controlled piston that moves inside a chamber to simulate respiratory movements of patients with different lung disorders. Parameters for the COPD setting were adapted from a previous study: compliance = 60 mL/cm H2O; inspiratory resistance = 10 cm/H2O/L/s; expiratory resistance = 15 cm/H2O/L/s; maximum drop in inspiratory pressure = –5 cm H2O.12 To simulate the negative pressure during inspiration, 5% of the respiratory cycle time was set as active inspiration, 3% was set as an end-inspiratory hold, and 15% was set to allow the pressure to return to baseline. The simulated lung was connected through a 20-cm extension tube to the oronasal mask (Comfortfull2, Respironics, Murrysville, Pennsylvania), which was applied tightly to the ManSimface (M-1, Respircare Medical, Shenyang, China). The noninvasive ventilator (BPAP25, Respircare Medical, Shenyang, China) was connected to the oronasal mask through a 150-cm breathing circuit. The oxygen concentrator (A05, Respircare Medical, Shenyang, China) supplied oxygen to the breathing circuit through an extension tube (Fig. 1).
Adjusting the Trigger Mechanism of Pulsed-Dose Oxygen Delivery.
The noninvasive ventilator and the oxygen concentrator were modified. The ventilator could send trigger signals based on a communication protocol to the oxygen concentrator through a data wire. The oxygen concentrator was a customized oxygen concentrator with built-in continuous flow oxygen and pulsed-dose oxygen delivery modes. In the continuous flow oxygen delivery mode, the oxygen concentrator can provide 1–5 L/min oxygen. In the pulsed-dose oxygen delivery mode, the oxygen concentrator cannot be triggered by patient's effort but only by the trigger signals from the noninvasive ventilator. In the preliminary experiment, we verified that the pulsed-dose oxygen delivery mode can work with the ventilator. Pulsed-dose oxygen delivery settings were numerical settings and factory preset values that represent the oxygen pulse characteristics of the oxygen concentrator. In pulsed-dose oxygen delivery setting 1, the oxygen concentrator delivered a pulsed dose of 16 mL oxygen in 80 ms. In setting 3, the oxygen concentrator delivered a pulsed dose of 48 mL oxygen in 160 ms. In setting 5, a pulsed dose of 80 mL oxygen was delivered in 320 ms.
When the oxygen concentrator was set to pulsed-dose oxygen delivery mode, the noninvasive ventilator monitored the changes in the pressure and flow in the breathing circuit to determine whether the patient was performing inhalation efforts. Once a trigger threshold was reached, the noninvasive ventilator immediately started ventilation and at the same time sent inhalation trigger signals to the oxygen concentrator to deliver oxygen into the breathing circuit.
Experimental Protocol.
The spontaneous breathing frequency in the simulated lung was set at 10 and 20 breaths/min. The ventilation mode was set to spontaneous breathing mode with a pressure rise slope of 1, inspiration sensitivity of 1, and expiration sensitivity of 1. The inspiratory and expiratory pressures were set at 16 and 4 cm H2O, respectively. The oxygen injection sites were on the mask (Site A), proximal to the mask (Site B), and at the ventilator outlet (Site C). The oxygen concentrator was set in the continuous flow oxygen delivery mode (oxygen flow = 1, 3, or 5 L/min) or pulsed-dose oxygen delivery (numerical setting = 1, 3, or 5).
Data Collection.
The ASL5000 simulator was calibrated prior to the bench study according to the manufacturer's recommendations. The customized gas analyzer was calibrated using the conventional method (ie, calibration of oxygen concentration at 21% and 100%); in addition, the pressure and flow at zero point were calibrated each time the device was turned on. To calculate the influence of oxygen delivery on NIV, baseline values were recorded before the experiment; for this purpose, NIV was performed without oxygen delivery. The following parameters were recorded for 10 respiratory cycles by the built-in software of the simulated lung: TPmin = time from beginning of the inspiratory effort to the lowest value of airway pressure required to trigger the ventilator; Ttrig = time to trigger; Ptrig = magnitude of airway pressure drop required to trigger; T90% = time from triggering of ventilator until airway pressure achieved 90% of the maximum pressure level during inspiration (Fig. 2); peak inspiratory pressure; peak inspiratory flow; mean flow; inspiratory time; actual tidal volume (VT) = VT displayed on the simulated lung; VT monitored = VT displayed on ventilator; breathing frequency; frequency of auto-triggering and missed triggers; and pulsed-dose oxygen delivery frequency of oxygen concentrator. Three minutes after adjustment of each experimental setting (eg, oxygen delivery mode, oxygen injection sites, and breathing frequency), the parameters mentioned above were re-recorded for 10 respiratory cycles. The flow, pressure, and were measured with a customized gas analyzer to calculate the actual inhaled oxygen concentration, based on a previous report.13
Clinical Study
Subjects.
Ten subjects with COPD exacerbation were included in the clinical study. They were in stable clinical condition after NIV for > 1 d (ie, > 5 h per day; oxygen flow < 3 L/min) and showed good adherence to therapy. The study protocol was approved by the Ethics Committee of the First Affiliated Hospital of the China Medical University (#AF-SOP-07-1.0-01). Written informed consent was obtained from all subjects prior to enrollment.
Study Protocol.
All subjects received NIV with the same face mask and ventilator as those used in the bench study in continuous flow oxygen delivery mode using an oxygen concentrator (ADS, Respircare Medical). The concentrator injected oxygen through an extension tube connected to a small hole in the face mask. was maintained at 90–92% for at least 30 min by titrating the oxygen flow with the oxygen concentrator (0.5 L/min change every time). The subjects continued NIV for 30 min after the continuous flow oxygen delivery mode of the oxygen concentrator was changed to pulsed-dose oxygen delivery. The method for titration of pulsed-dose oxygen delivery settings was identical to that used for titration of the oxygen flow in the continuous flow oxygen delivery mode. The target pulsed-dose oxygen delivery setting was the lowest numerical setting at which was maintained at 88–92% for at least 30 min. The pulsed-dose oxygen delivery numerical setting was increased every 3 min from the initial setting 1, by numerical setting 1 every time, until reached > 92%. The previous pulsed-dose oxygen delivery setting was the target setting. Heart rate, breathing frequency, systolic and diastolic blood pressure, poor triggers (ie, false or automatic triggering), VT, and peak airway pressure were documented in both continuous flow oxygen delivery and pulsed-dose oxygen delivery settings. After the experiment, patients were allowed to continue NIV with continuous flow oxygen delivery delivery.
Statistical Analysis.
Data pertaining to continuous variables are presented as mean ± SD; categorical variables are presented as percentages. In the bench study, one-way analysis of variance was used to assess the differences between the oxygen injection sites across each level of oxygen delivery mode and method of oxygen delivery. Post hoc analyses were performed to compare the differences between each pair of sites if the F test was significant (corrected P < .05, Bonferroni correction for multiple comparisons). The influence of oxygen delivery on NIV was calculated as the rate of difference: [(mean measured value – mean baseline values)/mean baseline value] × 100, and was compared using the independent sample t test. In addition, the differences of the influence of oxygen delivery on NIV between the 2 modes were calculated as the rate of difference: [(mean value of the number of pulsed-dose oxygen delivery – mean value of the oxygen flow of continuous flow oxygen delivery)/mean value of the oxygen flow of continuous flow oxygen delivery] × 100, and was compared using the independent sample t test. A clinically important difference was considered only when both a statistically significant difference (P < .05) and a change of > 10% from baseline were observed, given that small fluctuations in the measured values (ie, within the allowable error range) commonly result in a statistically significant difference.12 Efficacy of the 2 oxygen delivery systems on at the same numerical setting was evaluated with the ratio of equivalent oxygen delivery ( of pulsed-dose oxygen delivery/ of continuous flow oxygen delivery). In the clinical study, the paired t test was used to compare parameters in the continuous flow oxygen delivery and pulsed-dose oxygen delivery mode, and P < .05 was considered statistically significant. All analyses were performed using SPSS 22.0 (IBM, Armonk, New York).
Results
Bench Study
At the same numerical setting, the mean ratio of equivalent oxygen delivery of continuous flow oxygen delivery and pulsed-dose oxygen delivery was 0.94 ± 0.15. Nearly equivalent oxygen delivery (ie, a ratio of 0.9–1.1) was observed in 83.33% of the measurements (Fig. 3). In pulsed-dose oxygen delivery and continuous flow oxygen delivery modes, significant differences in values were observed when oxygen was injected at different sites (ie, sites A, C, and B in descending order; and sites A, C, and B in descending order, respectively; P < .05) (Table 1). was highest at site A in both pulsed-dose oxygen delivery and continuous flow oxygen delivery modes (Fig. 4). At site A in the pulsed-dose oxygen delivery mode, at scale 5, the mean at breathing frequencies of 10 and 20 breaths/min was 0.47 ± 0% and 0.41 ± 0%, respectively. At site A in the continuous flow oxygen delivery mode, at oxygen flow of 5 L/min, the mean at breathing frequencies of 10 and 20 breaths/min were 0.54 ± 0 and 0.48 ± 0, respectively.
Pulsed-dose oxygen delivery worked effectively with the ventilator, as demonstrated by the fine synchronization between the respiratory cycle of the ventilator, the simulated lung, and the pulsed-dose oxygen delivery. No instances of auto-trigger or missed trigger of the ventilator were observed. The mode used (pulsed-dose oxygen delivery or continuous flow oxygen delivery) showed no clinically important effect on trigger performance (eg, TPmin, Ttrig, Ptrig), controlling performance (eg, peak inspiratory pressure, peak inspiratory flow, mean flow, inspiratory time, and inspiratory rising time T90%), acute VT, or the VT monitored under different experimental conditions, regardless of the breathing frequency (ie, 10 or 20 breaths/min) (P > .05 and change of < 10% from baseline in both modes) (Table 2).
Clinical Study
There were 10 subjects (5 female and 5 male); mean age was 61.5 ± 13.3 y. Mean was 56.2 ± 7.3 mm Hg; mean inspiratory pressure was 16.4 ± 2.3 cm H2O, and mean expiratory pressure was 4.6 ± 0.4 cm H2O.
To achieve the same targeted after titration, the mean numerical setting in pulsed-dose oxygen delivery mode was 2.7 ± 0.3, and the mean oxygen flow in continuous flow oxygen delivery mode was 2.3 ± 0.6 L/min; the mean ratio of the numerical setting of pulsed-dose oxygen delivery and continuous flow oxygen delivery was 1.2 ± 0.2. No significant differences were observed between the continuous flow oxygen delivery and pulsed-dose oxygen delivery modes with respect to heart rate, breathing frequency, systolic and diastolic blood pressure, incidence of incorrect triggering (auto-trigger or missed triggers), VT, or peak inspiratory pressure (P > .05) (Table 3).
Discussion
We used a simulated lung to mimic spontaneous respiration in patients with chronic lung disease and simulated oxygen delivery during NIV in vitro. We used a data wire to connect the noninvasive ventilator with the oxygen concentrator to transmit trigger signals, and we compared the effects of continuous flow oxygen delivery and pulsed-dose oxygen delivery on and NIV. We then performed a clinical study wherein we titrated the oxygen flow or the pulsed-dose oxygen delivery numerical setting to maintain the same target under different oxygen delivery modes. Our results indicate that pulsed-dose oxygen delivery can be integrated into NIV to achieve efficacy similar to that achieved with continuous flow oxygen delivery. The oxygen delivery mode (continuous flow oxygen delivery or pulsed-dose oxygen delivery) compared to baseline and with each other showed no clinically important influence on NIV.
Several randomized controlled trials have reported that home oxygen therapy significantly reduced the mortality of subjects with COPD and severe stable hypoxemia, and that home oxygen therapy should be provided for at least 15 h/d.4–6 Despite no significant difference in mortality associated with 24 h and 15 h of oxygen therapy a day during home oxygen therapy,14 the British Thoracic Society guidelines for home oxygen therapy recommend round-the-clock oxygen therapy in adults.15 A study conducted in the United States noted that 60% of subjects on home oxygen therapy used oxygen 24 h/d.16 A study of subjects with obstructive sleep apnea on home NIV reported a dose-response relationship between daily use time and clinical efficacy. Prolonged use was associated with significant improvement in clinical symptoms and lower incidence of cardiovascular and metabolic complications.17 A meta-analysis reported that longer home NIV significantly reduced the level in subjects.18 Therefore, the efficacy of both home oxygen therapy and home NIV is directly proportional to the duration of daily use.
Currently, many available types of portable noninvasive ventilators or oxygen concentrators can meet the requirements of patients who receive home NIV or home oxygen therapy, respectively, at home or during ambulatory and transport settings. However, approximately 30% patients on home NIV may require concomitant home oxygen therapy.9 There are 4 main reasons that the portable oxygen concentrator must work effectively with a portable ventilator for patients who are simultaneously using home oxygen therapy and home NIV. First, with the development of pulsed-dose oxygen delivery technology, portable oxygen concentrators enabled patients to ambulate more easily and more economically compared to those using tanks or stationary concentrators. Second, some patients who require simultaneous home NIV and home oxygen therapy may not tolerate the disruption of oxygen therapy and ventilation support even for a short time in ambulatory and transport settings. Third, the portability of devices may improve adherence and prolong the usage time during outdoor activities, such as during exercise or long-distance travel. Fourth, the technology is invaluable in some specific settings such as in remote areas, during military operations, and during air travel.
Currently available portable concentrators are not directly compatible for use with a ventilator. For example, a case report illustrated the typical problems caused by the incompatibility between 2 devices.9 However, other studies have shown that portable oxygen concentrators may efficiently provide oxygen to the ambulant ventilator after modification of the trigger mechanism by the manufacturer (eg, use of positive pressure rather than negative pressure as a trigger).10,11 A recent animal study reported that the portable ventilator and concentrator with pulsed-dose oxygen delivery mode connected via a USB cable may work together. This may even achieve autonomous closed-loop control of oxygen delivery.7 Additionally, a new ventilator that has a single-limb circuit with an active valve and works with the pulse-dosed setting of the concentrator built into the device has been approved in the United States.
However, noninvasive ventilators have a single-limb circuit with a passive valve, which is different from the double-limb circuit used in the ambulant ventilator or the single-limb circuit with an active valve. It is not a closed circuit and intentionally allows air leak.19 Therefore, merely changing the trigger signal of the portable oxygen concentrator from negative pressure to positive pressure cannot ensure simultaneous triggering of the oxygen concentrator and the noninvasive ventilator. Besides, although the pulse trigger technology used in the portable oxygen concentrator is relatively mature, pulsed-dose oxygen delivery is mainly used in conscious patients and for emergency transportation of patients.20 Chatburn et al8 reported that some patients who receive oxygen therapy through a pulsed-dose oxygen system may have multiple episodes of low at night due to poor triggers in the oxygen concentrator.
Due to the concerns pertaining to the trigger of pulsed-dose oxygen delivery in complex clinical situations and NIV, we used a data cable to connect a noninvasive ventilator with an oxygen concentrator with pulsed-dose oxygen delivery mode and used the noninvasive ventilator to control the trigger of pulsed-dose oxygen delivery. In the bench study, the breathing frequency displayed on ventilator, the pulsed-dose oxygen delivery frequency of the oxygen concentrator, and the spontaneous breathing frequency displayed on the simulated lung were coordinated under different experimental conditions. Similarly, we coordinated the breathing frequency displayed on the ventilator, the pulsed-dose oxygen delivery frequency, and the breathing frequency of the subjects in the clinical study. Our data indicate that a modified oxygen concentrator with pulsed-dose oxygen delivery mode can effectively work with a noninvasive ventilator.
Continuous flow oxygen delivery is still the most commonly used mode of oxygen delivery. Although the oxygen flow is constant during the entire respiratory phase, the actual inhaled oxygen volume for effective gas exchange is uncertain. Most of the oxygen does not enter the alveoli during the entire expiratory phase and in the early inspiratory phase. As a result, the effective oxygen utilization rate is < 20%.21 Pulsed-dose oxygen delivery senses the patient's inspiratory effort through a high-sensitivity pressure sensor located at the end of the oxygen concentrator outlet and supplies a preset oxygen volume in a pulsed manner during the patient's inhalation phase through control of electromagnetic valve at the oxygen concentrator outlet. This mode improves the efficacy of oxygen utilization to 98%. It is not clear which oxygen delivery mode is preferable for long-term domiciliary oxygen therapy. Oxygen tanks and liquid oxygen systems are bulky and expensive, and they require frequent replacement.22 Almost all portable oxygen concentrators can only be used in the pulsed-dose oxygen delivery mode to improve oxygen utilization efficacy due to limited volume and weight, which is more suitable for ambulatory oxygen therapy.8
Several studies have reported that, at any given numerical setting, continuous oxygen delivery and pulsed-dose oxygen delivery exhibit equivalent efficacy.23–25 Animal studies also indicate that use of an emergency ambulatory ventilator with a compatible portable oxygen concentrator can achieve similar efficacy with continuous flow oxygen delivery and pulsed-dose oxygen delivery modes. Moreover, under volume control ventilation, pulsed-dose oxygen delivery was superior to continuous flow oxygen delivery.10 In our study, the efficacy of pulsed-dose oxygen delivery was similar to that of continuous flow oxygen delivery, although we did not use a precise conversion formula between the modes. In pulsed-dose oxygen delivery, was shown to be affected by oxygen purity, trigger mechanism, pulsed dose, duration of the pulse, pulsed flow curve, ventilation rate, VT, and inspiratory peak flow.26–28 In clinical settings, it is important to monitor pulse oximetry because it is difficult to determine which oxygen delivery mode achieves higher and superior efficacy. The results of our clinical study also suggest that pulsed-dose oxygen delivery can maintain satisfactory target , similar to continuous flow oxygen delivery.
Oxygen concentrators provide pulsed oxygen delivery with 16–80 mL of single-dose oxygen volume at different scales. At the initial phase of inspiration, the pulsed oxygen concentrator injects oxygen into the breathing circuit at 80–320 ms, which produces gas flow of 12–15 L/min. This may lead to fluctuation of pressure and flow in the breathing circuit and affect the performance of the noninvasive ventilator. In our bench and clinical studies, we did not observe any auto-triggering or missed triggers. In the bench study, we evaluated the effects of different oxygen delivery modes on NIV using multiple indicators of respiratory mechanics. We observed no significant effects of the oxygen delivery mode on NIV. This is likely attributable to the ability of the noninvasive ventilator to automatically recalibrate in response to fluctuations of pressure and flow.
We did not measure the actual in the clinical study, which is a limitation of our study. is known to be higher in in vitro studies and does not reflect clinical situations because the simulated lung does not utilize oxygen. In this study, we used the simulated lung to mimic patients with COPD. The purpose of our study was to investigate whether pulsed-dose oxygen delivery can effectively provide oxygen delivery for NIV. Most portable oxygen concentrators cannot deliver > 2 L of oxygen/min. Therefore, the oxygen concentrator used in the experiment was not a commercially available portable oxygen concentrator, but a customized oxygen concentrator with continuous flow oxygen delivery and pulsed-dose oxygen delivery modes for the convenience of the experiment. Further studies are needed to assess whether commercially available portable oxygen concentrators can be modified and used simultaneously with a noninvasive ventilator.
Conclusions
Once the pulsed trigger signal was transmitted through the ventilator to the oxygen concentrator through a data wire, pulsed-dose oxygen delivery could be integrated with NIV to achieve an efficacy very similar to that of continuous flow oxygen delivery. Both oxygen delivery modes had no significant influence on NIV. This technology may enable patients with chronic respiratory failure to receive better ambulatory respiratory support with increased efficiency of oxygen delivery during NIV, which may improve the quality of life of these patients.
Footnotes
- Correspondence: Bing Dai MD, Department of Respiratory Medicine, The First Affiliated Hospital of China Medical University, No. 155, Nanjing North St, Heping district, Shenyang 110001, China. E-mail: dai6206856{at}163.com
This work was supported by the Chinese National Natural Science Foundation (No. 81400061). The authors have disclosed no conflicts of interest.
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