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      Nasal highflow improves ventilation in patients with COPD

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          Nasal highflow (NHF) provides a warmed and humidified air stream up to 60 L/min. Recent data demonstrated a positive effect in patients with acute hypoxemic respiratory failure, especially when caused by pneumonia. Preliminary data show a decrease in hypercapnia in patients with COPD. Therefore, NHF should be evaluated as a new ventilatory support device. This study was conducted to assess the impact of different flow rates on ventilatory parameters in patients with COPD.

          Materials and methods

          This interventional clinical study was performed with patients suffering from severe COPD. The aim was to characterize flow-dependent changes in mean airway pressure, breathing volumes, breathing frequency, and decrease in partial pressure of CO 2 (pCO 2). Mean airway pressure was measured in the nasopharyngeal space (19 patients). To evaluate breathing volumes, we used a polysomnographic device (18 patients). All patients received 20 L/min, 30 L/min, 40 L/min, and 50 L/min and – to illustrate the effects – nasal continuous positive airway pressure and nasal bilevel positive airway pressure. Capillary blood gas analyses were performed in 54 patients with hypercapnic COPD before and two hours after the use of NHF. We compared the extent of decrease in pCO 2 when using 20 L/min and 30 L/min. Additionally, comfort and dyspnea during the use of NHF were surveyed.


          NHF resulted in a minor flow dependent increase in mean airway pressure. Tidal volume increased, and breathing rate decreased. The calculated minute volume decreased under NHF breathing. In spite of this fact, hypercapnia decreased with increasing flow (20 L/min vs 30 L/min). Additionally, an improvement in dyspnea was observed. The rapid shallow breathing index shows a decrease when using NHF.


          NHF leads to a flow-dependent reduction in pCO 2. This is most likely achieved by a washout of the respiratory tract and a functional reduction in dead space. In summary, NHF enhances effectiveness of breathing in patients with COPD, reduces pCO 2, the work of breathing, and rapid shallow breathing index as an indicator of respiratory work load.

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          Most cited references 24

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          Nasal high-flow versus Venturi mask oxygen therapy after extubation. Effects on oxygenation, comfort, and clinical outcome.

          Oxygen is commonly administered after extubation. Although several devices are available, data about their clinical efficacy are scarce.
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            Beneficial effects of humidified high flow nasal oxygen in critical care patients: a prospective pilot study.

            To evaluate the efficiency, safety and outcome of high flow nasal cannula oxygen (HFNC) in ICU patients with acute respiratory failure. Pilot prospective monocentric study. Thirty-eight patients were included. Baseline demographic and clinical data, as well as respiratory variables at baseline and various times after HFNC initiation during 48 h, were recorded. Arterial blood gases were measured before and after the use of HFNC. Noise and discomfort were monitored along with outcome and need for invasive mechanical ventilation. HFNC significantly reduced the respiratory rate, heart rate, dyspnea score, supraclavicular retraction and thoracoabdominal asynchrony, and increased pulse oxymetry. These improvements were observed as early as 15 min after the beginning of HFNC for respiratory rate and pulse oxymetry. PaO(2) and PaO(2)/FiO(2) increased significantly after 1 h HFNC in comparison with baseline (141 ± 106 vs. 95 ± 40 mmHg, p = 0.009 and 169 ± 108 vs. 102 ± 23, p = 0.036; respectively). These improvements lasted throughout the study period. HFNC was used for a mean duration of 2.8 days and a maximum of 7 days. It was never interrupted for intolerance. No nosocomial pneumonia occurred during HFNC. Nine patients required secondary invasive mechanical ventilation. Absence of a significant decrease in the respiratory rate, lower oxygenation and persistence of thoracoabdominal asynchrony after HFNC initiation were early indicators of HFNC failure. HFNC has a beneficial effect on clinical signs and oxygenation in ICU patients with acute respiratory failure. These favorable results constitute a prerequisite to launching a randomized controlled study to investigate whether HFNC reduces intubation in these patients.
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              High-flow oxygen therapy in acute respiratory failure.

              To compare the comfort of oxygen therapy via high-flow nasal cannula (HFNC) versus via conventional face mask in patients with acute respiratory failure. Acute respiratory failure was defined as blood oxygen saturation or = 0.50 via face mask. Oxygen was first humidified with a bubble humidifier and delivered via face mask for 30 min, and then via HFNC with heated humidifier for another 30 min. At the end of each 30-min period we asked the patient to evaluate dyspnea, mouth dryness, and overall comfort, on a visual analog scale of 0 (lowest) to 10 (highest). The results are expressed as median and interquartile range values. We included 20 patients, with a median age of 57 (40-70) years. The total gas flow administered was higher with the HFNC than with the face mask (30 [21.3-38.7] L/min vs 15 [12-20] L/min, P < .001). The HFNC was associated with less dyspnea (3.8 [1.3-5.8] vs 6.8 [4.1-7.9], P = .001) and mouth dryness (5 [2.3-7] vs 9.5 [8-10], P < .001), and was more comfortable (9 [8-10]) versus 5 [2.3-6.8], P < .001). HFNC was associated with higher P(aO(2)) (127 [83-191] mm Hg vs 77 [64-88] mm Hg, P = .002) and lower respiratory rate (21 [18-27] breaths/min vs 28 [25-32] breaths/min, P < .001), but no difference in P(aCO(2)). HFNC was better tolerated and more comfortable than face mask. HFNC was associated with better oxygenation and lower respiratory rate. HFNC could have an important role in the treatment of patients with acute respiratory failure.

                Author and article information

                Int J Chron Obstruct Pulmon Dis
                Int J Chron Obstruct Pulmon Dis
                International Journal of COPD
                International Journal of Chronic Obstructive Pulmonary Disease
                Dove Medical Press
                25 May 2016
                : 11
                : 1077-1085
                Department of Respiratory Medicine, University of Leipzig, Leipzig, Germany
                Author notes
                Correspondence: Jens Bräunlich, Department of Respiratory Medicine, University of Leipzig, Liebigstrasse 20, 04103 Leipzig, Germany, Tel +49 341 971 2450, Email jens.braeunlich@

                These authors contributed equally to this work

                © 2016 Bräunlich et al. This work is published and licensed by Dove Medical Press Limited

                The full terms of this license are available at and incorporate the Creative Commons Attribution – Non Commercial (unported, v3.0) License ( By accessing the work you hereby accept the Terms. Non-commercial uses of the work are permitted without any further permission from Dove Medical Press Limited, provided the work is properly attributed.

                Original Research

                Respiratory medicine

                ventilation, nhf, hypercapnia, nasal high flow cannula, pco2


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