Chronic obstructive pulmonary disease (COPD) is a heterogeneous disorder characterised by dysfunction of the small and large airways as well as by destruction of the lung parenchyma in highly variable combinations [
1]. Dyspnoea and exercise intolerance are the most common symptoms in COPD and progress relentlessly as the disease advances. Increased dyspnoea leads to inactivity and consequent peripheral muscle deconditioning, resulting in a vicious cycle leading to further inactivity, social isolation, anxiety, depression and reduced quality of life [
2‐
5]. Pulmonary rehabilitation (PR), with aerobic exercise training as a core component, is proposed in severe and very severe COPD, and has been shown to improve exercise capacity and quality of life [
6]. The effectiveness of PR on exercise tolerance, dyspnoea and quality of life has already been demonstrated in patients with chronic respiratory failure (CRF) [
7]. Nevertheless, these patients are frequently unable to sustain a workload high enough to obtain full benefit from the training programme [
8]. CRF patients, in fact, are characterised by an unbearable exercise-induced dyspnoea, mainly due to an imbalance between ventilatory capacity and ventilatory demand [
9], wherein ventilation during effort shows an out-of-proportion increase and so they prematurely reach the ventilatory reserve and are thus forced to stop exercising. The increase of dead space is the mechanism underlying this phenomenon [
10]. Optimisation of drug therapy [
11] along with non-pharmacological strategies can be useful to enhance exercise tolerance by reducing dyspnoea and work of breathing in advanced COPD with CRF. Among these techniques, oxygen supplementation delivered by nasal probes [
12] and several different types of non-invasive ventilation (NIV) have been proposed [
5]. In particular, NIV has the potential to reduce exercise dyspnoea by unloading respiratory muscles, allowing for higher levels of exercise intensity [
5], but it is not always tolerated during exercise due to a variety of side effects such as claustrophobia, skin rash or eye irritation; furthermore, its use requires high expertise and is time-consuming for health professionals during exercise sessions [
13]. High-flow nasal therapy (HFNT) is an emerging technique that may also be used to enhance ventilation and simultaneously provide an extended range of oxygen concentrations. It can deliver up to 60 L/min of heated, humidified air via nasal cannula, with or without additional oxygen. Above a flow of 20 L/min, HFNT can generate a positive pressure in the upper airways proportional to the set flow [
14]. At rest, HFNT has been demonstrated to increase alveolar ventilation and reduce respiratory rate and tissue carbon dioxide while increasing tidal end-expiratory lung volumes and gas exchange, and reducing work of breathing in patients with COPD [
15,
16].