Summary of studies assessing Heliox and including dyspnoea and exercise parameters as outcome measures
| Author [Ref.] | Participants | Study design | Dyspnoea parameter | Exercise tests | Intervention | Findings relating to dyspnoea | Findings relating to exercise |
| Babb [28] | 10 patients: COPD (FEV1 ∼78%) | RCT, cross-over | 20 point BS | 3 maximal symptom-limited incremental CPETs | Heliox21 and RA | ↔ WOB | ↑ Ventilation and WRmax (Heliox21), ↑ Heliox21# |
| Eves [29] | 10 patients: COPD (FEV1 ∼47%) | RCT, cross-over | 10 point BS | 1 symptom-limited CPET and 4 constant rate CPETs (60% WRmax) | RA, O2 28%, Heliox21 and Heliox28 | ↓ Dyspnoea# and ↓ WOB | ↑↑ Heliox28, ↑ Heliox21 and O2 28%, ↑ Ventilation Heliox21# |
| Johnson [30] | 39 patients: COPD (FEV1 ∼50%) | RCT, open label | PSQ | 3 maximal symptom-limited CPETs (treadmill) pre/post 6-week pulmonary rehabilitation (exercise and education) | Heliox21, RA and NIPPV | ↔ BS, 55% (He group) reported ↑ PROs | ↔ Training benefits Heliox21 and NIPPV |
| Laude [31] | 21 patients: COPD (FEV1 ∼43%) | RCT, cross-over | 10 point BS and VAS | Incremental shuttle walk tests | RA, O2 28%, Heliox21 and Heliox28 | ↓ Dyspnoea (BS and VAS): all gas mixes# | ↑ Endurance: all gas mixes# |
| Marciniuk [32] | 16 patients: COPD (FEV1 ∼48%) | RCT, cross-over | 10 point BS | 1 maximal symptom-limited CPET and 6MWT, and 4 6MWTs on 2 visits | RA, 100% O2 (mask), 100% O2 (nasal cannula) and Heliox30 | ↔ Heliox to RA BS | Significant ↑ in distance on Heliox30# |
| Oelberg [33] | 18 patients: 8 COPD (FEV1 19%); 10 normal (FEV1 93%) | Unblinded comparison study | PROs | 2 incremental CPETs | Heliox21 and RA | ↓ Dyspnoea PROs# | ↔ Change in peak work loads |
| Palange [34] | 12 patients: COPD (FEV1 <50%) | RCT, single blind cross-over | 12 point VAS | 1 maximal symptom-limited CPET and 2 constant rate CPETs | Heliox21 and RA | ↓ Dyspnoea# | ↑ Endurance, non-significant improvements in lung mechanics# |
| Richardson [35] | 10 patients: COPD (FEV1 <40%) | Single blinded cross-over | 10 point BS | 3 incremental maximal CPETs and single knee extensor ergometry testing | Heliox21, 100% O2 and RA | ↔ Dyspnoea | ↑ Peak work, ↑ Ventilation# |
COPD: chronic obstructive pulmonary disease; FEV1: forced expiratory volume in 1 s; RCT: randomised controlled trial; BS: Borg scale; CPET: cardiopulmonary exercise test (cycle ergometry unless stated); RA: room air; WOB: work of breathing; WRmax: maximal work rate; PSQ: Patient Satisfaction Questionnaire; NIPPV: noninvasive positive pressure ventilation; PRO: patient reported outcome; VAS: visual analogue scale; 6MWT: 6-min walk test. #: statistically significant finding; ↔: no significant change; ↓ decreased; ↑ increased.