The Effect of Nasal Flow on Breathlessness in Patients with Chronic Obstructive Pulmonary Disease

Abstract

Many patients with chronic obstructive pulmonary disease (COPD) receiving supplemental oxygen state that this treatment makes them less short of breath at rest. We postulated that this phenomenon may be related to improved arterial oxygenation, reduced ventilation, or stimulation of nasal receptors caused by the flow of gas. Eight patients who reported this phenomenon were studied in a quiet room. Each patient received zero flow, 2, or 4 L/min of air or oxygen through nasal cannula for 5 min at each level in random order in a single blind manner. At the end of each period, arterial blood gas composition was measured, and breathlessness was assessed with a visual analog scale. The scale was calibrated to read from zero (not at all breathless) to 100 (extremely short of breath). The entire protocol was repeated after application of topical lidocaine to the nasal passages. Results were assessed by analysis of variance. We found no significant effect of inspired oxygen concentration, gas flow, arterial oxygen tension, or arterial carbon dioxide tension on breathlessness. There was, however, a significant increase in breathlessness after nasal anesthesia from 44 +/- 3 SEM to 52 +/- 4 SEM (p less than 0.005). We suggest that the reduction of breathlessness in these patients by nasal oxygen is a placebo effect caused by wearing the nasal cannulas and is unrelated to gas flow or the increased arterial oxygen tension.

Disabling dyspnoea in patients with advanced disease: lack of effect of nebulized morphine

“…Oxygen via nasal prongs was included in the study protocol, as there is a theoretical potential for inhaled morphine to lower oxygen saturation. Although the effect of supplemental oxygen on dyspnoea at rest has been disputed [18], at least two studies have shown that oxygen reduces dyspnoea at rest to a greater extent than air (delivered in similar fashion) in hypoxaemic patients with COPD [19], or with terminal cancer [20]. In the present study, the beneficial effect on dyspnoea cannot be ascribed to oxygen, since an equal efficacy was obtained with 10 mg nebulized morphine, without the addition of oxygen.…”

“…A placebo effect of similar magnitude on dyspnoea at rest has been demonstrated previously following nebulized saline in patients with severe asthma or COPD [7]. Other studies have provided arguments in favour of a nonspecific reduction in dyspnoea related to the use of either nasal prongs [18], or a face mask [21].…”

Short­burst oxygen immediately before and after exercise is ineffective in nonhypoxic COPD patients

“…It is possible that oxygen delivered to hypoxic subjects after exercise may reduce dyspnoea via similar mechanisms to those described during exercise and indeed oxygen delivered after exercise has recently been reported to reduce dynamic hyperinflation [8]. A further study comparing oxygen with air given to hypoxic subjects at rest, demonstrated no difference in dyspnoea but all subjects were significantly more dyspnoeic during administration of both gases when topical anaesthesia had been applied to the nasal passages [24]. This suggests a role for nonspecific stimulation of nasal receptors by gas flow in the modulation of dyspnoea and could explain why oxygen did not reduce dyspnoea more than air in this study.…”

Contributions of a hand-held fan to self-management of chronic breathlessness

“…Airflow and cooling from the fan have been postulated to influence afferent sources for respiratory sensation by stimulating upper airway "flow" receptors or trigeminal skin receptors [5,13,34,35]. The first of these mechanisms would require cooling of nasal or airway mucosa, whereas the second could be achieved by cooling the facial skin.…”