Table 2.
Studies showing that HMEs attenuate exercise-induced bronchoconstriction.
| References | Temperature (°C) | Humidity | Duration (minutes) |
Exercise intensity/ ventilation rate |
Main finding |
|---|---|---|---|---|---|
| Beuther and Martin (2006) | −15 to −25 Isolated breathing of sub-zero air |
Not reported | 10 | 85% O2max | Placebo: ΔFEV1 = −19 ± 4.9% HME: ΔFEV1 = −4.3 ± 1.6% fall in FEV1 |
| Nisar et al. (1992) | −13 Isolated breathing of sub-zero air |
Not reported | 6 | 75% O2max | No HME: ΔFEV1 = −22% (−13 to −51%) HME: ΔFEV1 = −10% (0 to −26%) |
| Millqvist et al. (1995) | −10 Whole body exposure |
Not reported | 3 ×6 | 50–150 W | Study A, n = 9 No HME: ΔFEV1 = −36% HME: ΔFEV1 = −11% HME “protective effect” = 70% (range 19–100%) Two women could not complete protocol without HME Study B n = 5 HME “protective effect” = 74% Placebo mask with one-directional filters (no heat-moisture exchange), protective effect = 14% |
| Millqvist et al. (2000) | −10 Nasal clips to prevent nasal breathing |
Not reported | 3 ×6 | Incremental 30–150 W | No HME: ΔFEV1 = −27% HME: ΔFEV1 = −12% Beta-2-agonist: ΔFEV1 = −7% HME+beta-2-agonist: ΔFEV1 = None |
| Jackson et al. (2018)* | 8 Whole body exposure |
20% RH | 6 | 80% PPO | HME: ΔFEV1 = −6.0%, SHAM: ΔFEV1 = −9.5%, No HME: ΔFEV1 = −13.0%, p = 0.03 between HME and No HME. |
| Gravelyn et al. (1987) | 22 | 0 mg H2O·L−1 | 5 | 60–70 L·min−1 | No HME: 300% increase in sRaw after hyperpnea with dry air HME: 7% increase in sRaw after hyperpnea |
| Brenner et al. (1980) | 23 | 26% RH | 6 | 90% HRmax | No HME: FEV1 = 66 ± 6 of individuals' (pre-exercise) baseline, 6 min after exercise HME: FEV1 = 91 ± 3% of individuals' baseline |
| Frischhut et al. (2020) | −20 Whole body exposure |
46.2% RH | 8 | 90–95% HRmax | Winter athletes without asthma No HME: FVC −5.9%, FEV1 −4.2% vs. pre-exercise baseline HME: FVC no reduction FEV1 no reduction |
*Conference proceedings.
FEV1, Forced expiratory volume in 1 s; HME, Heat and moisture-exchanging breathing mask; HR, Heart rate; PPO, Peak power output; RH, Relative humidity; sRaw, Specific airways resistance; O2max, Maximum oxygen uptake; W, Watts.