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

Abstract

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.

Keywords: COPD; Hypercapnia; Nasal high flow; Type II respiratory failure; Wash-out.

Conflict of interest statement

Ethics approval and consent to participate

The study was approved (414–14-06102014) and registered (ClinicalTrails NCT02504814) by the ethics committee of the Medical School of Leipzig University. All patients gave written informed consent to participate in the study.

Consent for publication

Not applicable.

Competing interests

JB received travel grants and equipment from TNI medical AG (Wuerzburg, Germany). FM declares that he/she has no competing interests. HW received lecture fees from TNI medical AG.

Publisher’s Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Figures

Fig. 1

Experimental conditions. 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

Fig. 2

Percentage decrease in capillary PCO2 in COPD patients after 1 h of NHF breathing under different experimental conditions. * = p < 0.05 vs. baseline; baseline PCO2 > 55 mmHg, a: n = 14, b: n = 11, c: n = 9, d: n = 9

Fig. 3

Percentage decrease of capillary PO2 in COPD patients after 1 h of NHF breathing under different experimental conditions. ** = p > 0.05 vs. baseline; baseline PCO2 > 55 mmHg, a: n = 14, b: n = 11, c: n = 9, d: n = 9

Fig. 4

Changes in mean airway pressure in COPD patients under different experimental conditions. * = p < 0.05 vs. baseline; n = 10