Effects of a helium/oxygen mixture on individuals’ lung function and metabolic cost during submaximal exercise for participants with obstructive lung diseases

Figures & data

Figure 1 Study flowchart.

Notes: ^aA 5-minute initial wash-in for healthy volunteers and patients before performing any evaluation. ^bA 5-minute at rest followed by 5 minutes exercise at 0 Watts and 5 minutes individually adjusted, light adjusted cycling exercise.

Table 1 Baseline characteristics, pulmonary function tests at rest, and pulse oximetry breathing air of the study groups

	Healthy volunteers	Moderate persistent asthmatics	Severe persistent asthmatics	Moderate COPD participants	Severe COPD participants
Sex M/F (n)	3/3	3/3	1/5	4/2	6/0
Age (year)	32 (6.9)	42 (11.1)	64 (7.8)	66 (4.6)	67 (7.4)
BMI (kg/m^2)	21.5 (1.9)	26.1 (5.0)	25.6 (1.3)	23.5 (4.3)	24.7 (3.0)
FEV1/FVC (%)	80 (4)	63 (5)	47 (8)	52 (9)	40 (8)
FEV1 (L)	4.05 (0.91)	2.66 (0.68)	1.29 (0.20)	1.82 (0.52)	1.29 (0.25)
FEV1 (%pred)	105 (11)	76 (5)	54 (7)	66 (11)	42 (5)
IC (L)	3.41 (0.87)	3.29 (0.98)	2.44 (0.50)	2.82 (0.61)	2.35 (0.43)
IC (%pred)	105 (13)	107 (16)	110 (17)	110 (26)	77 (12)
RV/TLC (%)	27.0 (3.9)	37.5 (9.4)	54.0 (4.7)	49.8 (6.9)	56.5 (7.9)
SpO2 (%)	98 (0.5)	98 (0.8)	95 (1.5)	96 (1.6)	95 (2.4)
Symptoms >1/week	NA	3	2	NA	NA
Regular use of β2 agonists	NA	5	6	NA	NA
Frequent cough	NA	NA	NA	3	4
Frequent expectoration	NA	NA	NA	5	4
Breathlessness score ≥3	NA	NA	NA	1	3
Current smokers	NA	NA	NA	6	4

Notes: Data are provided as mean (standard deviation). Grade of breathlessness ≥3 is according to the Modified Medical Research Council Dyspnea Scale.

Abbreviations: BMI, body mass index; F, female; FEV₁, forced expiratory volume in 1 second; FVC, forced vital capacity; IC, inspiratory capacity; M, male; NA, not applicable; RV, residual volume; SpO₂, O₂ saturation measured at fingertip; TLC, total lung capacity; %pred, percent predicted.

Table 2 Physiological response parameters during constant work rate exercise for the different study groups and the two gas mixtures (He/O₂ 78%/22% and Medical air)

	Healthy volunteers (N=6)	Moderate persistent asthmatics (N=6)	Severe persistent asthmatics (N=6)	Moderate COPD participants (N=6)	Severe COPD participants (N=6)
WRmax(pred)	67 (6.1)	62 (6.4)	60 (11.6)	57 (6.8)	41 (3.3)
WR (air), Watts	104 (25)	61 (21)	26 (8)	35 (11)	26 (9)
WR (He/O2), Watts	110 (21)	68 (24)	29 (9)	40 (15)	28 (8)
Metabolic
${V^{\prime }}_{{\mathrm{O}}_2}$ (air), mL/min	1,524 (306)	1,193 (213)	799 (150)	867 (187)	886 (159)
${V^{\prime }}_{{\mathrm{O}}_2}$ (He/O2), mL/min	1,204 (392)	922 (279)**	645 (106)**	800 (248)	835 (219)
${V^{\prime }}_{{\text{co}}_2}$ (Air), mL/min	1,441 (412)	1,062 (223)	699 (157)	785 (184)	745 (132)
${V^{\prime }}_{{\text{co}}_2}$ (He/O2), mL/min	1,014 (333)	810 (226)**	499 (98)**	683 (175)	628 (152)
Cardiovascular
HR (Air), beats/min	135 (20)	110 (10)	92 (12)	104 (12)	106 (20)
HR (He/O2), beats/min	143 (16)	109 (8)	91 (13)	104 (11)	104 (16)
Ventilatory
RR (Air), breaths/min	18 (3)	21 (4)	21 (5)	27 (4)	25 (5)
RR (He/O2), breaths/min	19 (4)	22 (4)	20 (8)	28 (5)	26 (4)
V′E (Air), L/min	8.0 (1.4)	6.0 (1.5)	4.8 (0.8)	6.7 (2.1)	6.0 (1.1)
V′E (He/O2), L/min	7.5 (1.7)	5.5 (1.4)	4.1 (0.5)	6.2 (1.9)	5.5 (0.9)
SpO2 (Air), %	95 (1)	96 (1)	97 (1)	95 (1)	96 (2)
SpO2 (He/O2), %	96 (1)	97 (1)	97 (1)	96 (1)	95 (4)

Notes: Data are provided as mean (standard deviation).

** P<0.05 as compared to the same variable measured with air.

Abbreviations: WR, work rate; WR_max(pred), maximum work rate predicted; HR, heart rate; RR, respiratory rate; SpO₂, O₂ saturation measured at fingertip; V′_E, minute ventilation; ${V^{\prime }}_{{\mathrm{O}}_2}$, oxygen uptake; ${V^{\prime }}_{{\text{co}}_2}$, CO₂ release; min, minute.

Figure 2 Average of normalized oxygen uptake $\mathrm{n}{V^{\prime }}_{{\mathrm{O}}_2}={V^{\prime }}_{{\mathrm{O}}_2}$/(3.5ml/kg/min × weight kg) at rest while breathing air or He/O₂ mixture for the healthy, asthmatic, and COPD groups.

Note: The error bars represent standard deviation.

Abbreviations: COPD, chronic obstructive pulmonary disease; ${{\mathrm{V}}^{\prime }}_{{\mathrm{O}}_2}$, oxygen uptake.

Figure 3 Average MET after submaximal exercise for each subject group.

Note: The error bars represent standard deviation.
Abbreviation: MET, metabolic equivalent.

Figure 4 Individual changes in normalized oxygen uptake $\mathrm{n}{V^{\prime }}_{{\mathrm{O}}_2}={V^{\prime }}_{{\mathrm{O}}_2}$/(3.5 mL/kg/min × weight kg) at rest while breathing air or He/O₂ mixture.

Notes: For the subject groups solid and dashed lines are for moderate and severe cases, respectively. The bars represent the mean values. There were only 30 participants in total who completed the study, but subject numbers were assigned to other initiated patients who later dropped out while the original subject numbers are retained.

Abbreviations: COPD, chronic obstructive pulmonary disease; ${{\mathrm{V}}^{\prime }}_{{\mathrm{O}}_2}$, oxygen uptake.

Figure 5 Individual changes in MET after submaximal exercise while breathing air or He/O₂ for the (A) healthy, (B) asthmatic, and (C) COPD groups.

Notes: MET is based on ${V^{\prime }}_{{\mathrm{O}}_2}$ measure for each subject at rest. For the subject groups, solid and dashed lines are for moderate and severe cases, respectively. The bars represent the mean values. There were only 30 participants in total who completed the study, but subject numbers were assigned to other initiated patients who later dropped out while the original subject numbers are retained.

Abbreviations: MET, metabolic equivalent; COPD, chronic obstructive pulmonary disease; V′_O2, oxygen uptake.

Figure 6 Individual changes in metabolic cost per unit volume of oxygen inspired after submaximal exercise breathing air and He/O₂ mixtures as measured by minute ventilation divided by oxygen uptake $({V^{\prime }}_{\mathrm{E}}={V^{\prime }}_{{\mathrm{O}}_2})$ for the (A) healthy, (B) asthmatic, and (C) COPD groups.

Notes: For the subject groups, solid and dashed lines are for moderate and severe cases, respectively. The bars represent the mean values. There were only 30 participants in total who completed the study, but subject numbers were assigned to other initiated patients who later dropped out while the original subject numbers are retained.
Abbreviations: COPD, chronic obstructive pulmonary disease; min, minute; ${{\mathrm{V}}^{\prime }}_{{\mathrm{O}}_2}$, oxygen uptake.

Figure 7 The change in metabolic cost of breathing from air to He/O₂ for each subject and categorized by subject group plotted as a function of IC% predicted.

Note: The dashed line at 0 is the indicator of no benefit.
Abbreviations: COPD, chronic obstructive pulmonary disease; IC%, inspiratory capacity percent.