A low concentration of nitrous oxide reduces dyspnoea produced by a combination of hypercapnia and severe elastic load.
We have measured how a low concentration of nitrous oxide affected respiratory sensation and ventilation. Severe dyspnoea was induced in nine normal subjects by a combination of hypercapnia and inspiratory elastic load (50 cm H2O litre-1). Subjects were asked to rate their sensation of respiratory discomfort using a visual analogue scale (VAS) while breathing either 20% nitrous oxide or 20% nitrogen gas mixture. We compared the effects of each gas mixture on respiratory sensation and ventilation using steady-state values of ventilatory variables and VAS scores obtained before, during and after inhalation of each gas mixture. Inhalation of 20% nitrous oxide reduced the sensation of respiratory discomfort from a median VAS score of 6.5 (range 5.0-8.1) before inhalation to 3.6 (2.4-5.9) during inhalation (P < 0.05). There was no significant change in minute ventilation but tidal volume increased during inhalation of 20% nitrogen did not alter VAS scores or ventilatory variables. We found that a low concentration of nitrous oxide greatly alleviated the intensity of dyspnoea without changing respiratory load compensation.
D000328:Adult; D018712:Analgesics, Non-Narcotic / Q000008:administration & dosage*; D004334:Drug Administration Schedule; D004417:Dyspnea / Q000188:drug therapy* / Q000209:etiology / Q000503:physiopathology; D005260:Female; D006801:Humans; D006935:Hypercapnia / Q000150:complications; D008297:Male; D009584:Nitrogen / Q000008:administration & dosage; D009609:Nitrous Oxide / Q000008:administration & dosage*; D012119:Respiration / Q000187:drug effects; D012677:Sensation / Q000187:drug effects; D013990:Tidal Volume / Q000187:drug effects