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      Letter to the editor: “Nasal high-flow versus non-invasive ventilation in patients with chronic hypercapnic COPD” [Letter]

      1 , 2 , 1 , 2

      International Journal of Chronic Obstructive Pulmonary Disease

      Dove

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          Abstract

          Dear editor We read with interest the recent article by Bräunlich et al entitled ‘Nasal high-flow versus non-invasive ventilation in patients with chronic hypercapnic COPD’ recently published in the International Journal of COPD.1 It covers an important topic, as this is the first study comparing non-invasive ventilation (NIV) and nasal high flow (NHF) therapy in stable hypercapnic COPD patients. Nevertheless we would like to stress some important issues with regard to the interpretation of the results. Firstly, we would like to address the non-inferiority analysis of this trial. A non-inferior trial should be considered when there is a clear advantage in any area other than effectiveness, like lower costs or fewer side effects.2 This study shows that NHF is similarly effective in reducing PaCO2 in stable hypercapnic patients, but the exact advantage of NHF over NIV is unexplained. The authors suggest that comfort may be increased by NHF since NIV is not tolerated in some patients, however, this is not represented by the results. The amount of drop-outs is comparable between groups, just like the assessment of the devices and quality of life scores. Furthermore, no data is presented about the patient’s decision on which device he or she wants to use after the study period. Therefore, based on these results, it is unclear to us why the authors conclude that NHF may be an alternative to NIV. Secondly, we have reservations about the adequate application of both treatments. The authors state that NIV pressure settings were adjusted to achieve optimal tolerability and pCO2 reduction. However, compliance during NIV is very limited with an average of 3.9±2.5 hrs/day questioning optimal tolerability, and the effect in PaCO2 reduction is moderate. Therefore, we doubt whether NIV was adequately administered. An exclusion criterion was prior therapy with NIV in the last 14 days. However, no data is given about the experience with NIV at all, which could greatly influence both compliance and drop-out rate. Also the treatment of NHF was probably not optimal. The flow rate was limited to 20 L/min due to technical aspects. However, multiple studies show that the CO2 washout effect is flow-dependent where higher flow leads to more CO2 washout.3,4 The flow rate of 20 L/min is likely to be inadequate for sufficient CO2 reduction; although the exact optimal flow in chronic care resulting in optimal effect with good compliance is unknown. A randomized controlled trial with adequate treatment settings and data with regard to optimal nHFT titration is needed to show whether NHF is a (superior) alternative to NIV in reducing hypercapnia and, more importantly, in achieving improvement in patient-related outcomes.

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          Effectiveness of nasal highflow in hypercapnic COPD patients is flow and leakage dependent

          Background Nasal Highflow (NHF) delivers a humidified and heated airflow via nasal prongs. Current data provide evidence for efficacy of NHF in patients with hypoxemic respiratory failure. Preliminary data suggest that NHF may decrease hypercapnia in hypercapnic respiratory failure. The aim of this study was to evaluate the mechanism of NHF mediated PCO2 reduction in patients with chronic obstructive pulmonary disease (COPD). Methods In 36 hypercapnic COPD patients (PCO2 > 45 mmHg), hypercapnia was evaluated by capillary gas sampling 1 h after NHF breathing under four conditions A to D with different flow rates and different degrees of leakage (A = 20 L/min, low leakage, two prongs, both inside; B = 40 L/min, low leakage, two prongs, both inside; C = 40 L/min, high leakage, two prongs, one outside and open; D = 40 L/min, high leakage, two prongs, one outside and closed). Under identical conditions, mean airway pressure was measured in the hypopharynx of 10 COPD patients. Results Hypercapnia significantly decreased in all patients. In patients with capillary PCO2 > 55 mmHg (n = 26), PCO2 additionally decreased significantly by increased leakage and/or flow rate in comparison to lower leakage/ flow rate conditions (A = 94.2 ± 8.2%; B = 93.5 ± 4.4%; C = 90.5 ± 7.2%; D = 86.8 ± 3.8%). The highest mean airway pressure was observed in patients breathing under condition B (2.3 ± 1.6 mbar; p < 0.05). Conclusions This study demonstrates effective PCO2 reduction with NHF therapy in stable hypercapnic COPD patients. This effect does not correlate with an increase in mean airway pressure but with increased leakage and airflow, indicating airway wash out and reduction of functional dead space as important mechanisms of NHF therapy. These results may be useful when considering NHF treatment in hypercapnic COPD patients. Trial registration Clinical Trials: NCT02504814; First posted July 22, 2015.
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            Nasal high-flow versus noninvasive ventilation in patients with chronic hypercapnic COPD

            Background Despite the encouraging results of noninvasive ventilation (NIV) in chronic hypercapnic COPD patients, it is also evident that some patients do not tolerate NIV or do not benefit from it. We conducted a study in which COPD patients with stable, chronic hypercapnia were treated with NIV and nasal high-flow (NHF) to compare effectiveness. Methods In a multi-centered, randomized, controlled, cross-over design, patients received 6 weeks of NHF ventilation followed by 6 weeks of NIV ventilation or vice-versa (TIBICO) between 2011 and 2016. COPD patients with stable daytime hypercapnia (pCO2≥50 mmHg) were recruited from 13 German centers. The primary endpoint was pCO2 changes from baseline blood gas, lung function, quality of life (QoL), the 6 min walking test, and duration of device use were secondary endpoints. Results A total of 102 patients (mean±SD) age 65.3±9.3 years, 61% females, body mass index 23.1±4.8 kg/m2, 90% GOLD D, pCO2 56.5±5.4 mmHg were randomized. PCO2 levels decreased by 4.7% (n=94; full analysis set; 95% CI 1.8–7.5, P=0.002) using NHF and 7.1% (95% CI 4.1–10.1, P<0.001) from baseline using NIV (indistinguishable to intention-to-treat analysis). The difference of pCO2 changes between the two devices was −1.4 mmHg (95% CI −3.1–0.4, P=0.12). Both devices had positive impact on blood gases and respiratory scores (St. George’s Respiratory Questionnaire, Severe Respiratory Insufficiency Questionnaire). Conclusions NHF may constitute an alternative to NIV in COPD patients with stable chronic hypercapnia, eg, those not tolerating or rejecting NIV with respect to pCO2 reduction and improvement in QoL.
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              Nasal high flow therapy and PtCO2in stable COPD: A randomized controlled cross-over trial

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                Author and article information

                Journal
                Int J Chron Obstruct Pulmon Dis
                Int J Chron Obstruct Pulmon Dis
                COPD
                copd
                International Journal of Chronic Obstructive Pulmonary Disease
                Dove
                1176-9106
                1178-2005
                06 September 2019
                2019
                : 14
                : 2117-2118
                Affiliations
                [1 ]Department of Pulmonary Diseases/Home Mechanical Ventilation, University Medical Center Groningen, University of Groningen , Groningen, The Netherlands
                [2 ]Groningen Research Institute for Asthma and COPD (GRIAC), University of Groningen , Groningen, The Netherlands
                Author notes
                Correspondence: J ElshofDepartment of Pulmonary Diseases/Home Mechanical Ventilation, University Medical Center Groningen, University of Groningen , Groningen, The NetherlandsEmail j.elshof@umcg.nl
                Article
                226697
                10.2147/COPD.S226697
                6735658
                © 2019 Elshof and Duiverman.

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                Page count
                References: 4, Pages: 2
                Categories
                Letter

                Respiratory medicine

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