Table 3.

CPET results of generalized linear mixed model (GLM model) analysis of 40 subjects without mask (NM) and with three different mask types (SM, CM, FFP2).

	Pre (light work)				E1 (moderate work)				E2 (heavy work)				E3 (very heavy work)				Post (light work)
	NM	SM	CM	FFP2	NM	SM	CM	FFP2	NM	SM	CM	FFP2	NM	SM	CM	FFP2	NM	SM	CM	FFP2
	G.M	Δ p value			G.M	Δ p value			G.M	Δ p value			G.M	Δ p value			G.M	Δ p value
Subjects’ perceived physical exertion
BORG (0–10)	0.81	− 0.05	− 0.04	− 0.18	0.96	0.05 0.651	0.22 0.306	0.33 0.022	2.14	0.33 0.384	0.23 0.522	0.89 0.008	3.68	0.59 0.360	0.54 0.419	1.21 0.016	0.88	0.11 0.498	0.14 0.475	0.22 0.064
Pulmonary parameters
Ttot (s)	3.91	− 0.08	− 0.04	0.18	2.95	0.08 0.491	− 0.01 0.707	0.23 0.130	2.53	0.04 0.251	0.00 0.463	0.22 0.333	2.11	0.06 0.171	0.08 0.197	0.23 0.124	2.95	0.03 0.399	− 0.03 0.944	0.11 0.848
RR (min−1)	15.37	0.01	0.17	− 0.85	20.31	− 0.51 0.521	0.14 0.918	− 1.52 0.610	23.71	− 0.38 0.670	0.01 0.794	− 2.04 0.476	28.37	− 0.76 0.450	− 0.97 0.220	− 2.70 0.243	20.43	− 0.38 0.622	0.09 0.869	− 0.85 0.731
VT (L)	0.90	0	− 0.01	− 0.02	1.64	− 0.01 0.948	− 0.04 0.662	− 0.01 0.518	1.98	0 0.922	− 0.03 0.792	0 0.553	2.25	− 0.01 0.938	0 0.720	− 0.03 0.353	1.25	− 0.02 0.709	− 0.05 0.440	0 0.599
VE (L*min−1)	12.03	0.28	0.26	− 0.42	31.26	− 0.40 0.380	− 0.39 0.407	− 1.91 0.506	45.47	− 0.67 0.344	− 0.93 0.293	− 3.95 0.164	62.52	− 1.93 0.187	− 2.51 0.129	− 7.19 0.035	23.3	− 0.88 0.225	− 0.65 0.328	− 0.92 0.937
VO2 (ml*min−1)	301.78	− 27.34	− 21.06	− 36.51	1050.92	− 19.36 0.095	− 36.41 0.367	− 73.39 0.251	1474.55	− 21.65 0.067	− 33.02 0.217	− 92.81 0.168	1910.85	− 38.02 0.076	− 39.58 0.191	− 124.26 0.176	475.16	35.8 0.858	43.45 0.838	43.78 0.621
VCO2 (ml*min−1)	243.71	− 20.26	− 14.02	− 23.12	889.26	− 29.53 0.264	− 32.85 0.649	− 59.74 0.525	1361.39	− 36.30 0.198	− 32.13 0.446	− 94.92 0.555	1850.06	− 42.07 0.184	− 38.13 0.424	− 122.94 0.520	526.86	− 48.50 0.881	− 40.13 0.759	− 36.44 0.668
VE/VO2	39.87	4.96	3.89	3.87	29.74	0.17  < 0.001	0.68 0.014	0.28 0.004	30.83	0  < 0.001	0.07 0.001	− 0.79  < 0.001	32.71	− 0.37  < 0.001	− 0.66  < 0.001	− 1.76  < 0.001	49.03	− 5.17 0.086	− 5.37 0.116	− 5.92 0.096
VE/VCO2	49.36	5.70	4.11	3.24	35.15	0.74  < 0.001	0.88 0.035	0.23 0.030	33.39	0.41  < 0.001	0.11 0.003	− 0.62 0.002	33.78	− 0.27  < 0.001	− 0.67  < 0.001	− 1.69  < 0.001	44.20	2.66 0.094	2.33 0.343	1.43 0.295
EELV (L)	3.98	0.20	0.37	0.02	3.88	0.06 0.413	− 0.01 0.129	0.32 0.920	3.81	0.09 0.758	0.15 0.540	− 0.10 0.698	3.94	− 0.30 0.125	− 0.29 0.064	− 0.43 0.142	4.28	− 0.06 0.458	− 0.38 0.034	− 0.71 0.031
BR (%)	10.85	0.44	0.51	− 0.13	28.15	0.16 0.400	0.40 0.427	− 1.05 0.528	40.93	0.16 0.365	0.27 0.313	− 2.59 0.178	56.28	− 0.70 0.201	− 0.78 0.140	− 5.19 0.039	20.98	− 0.41 0.236	− 0.03 0.343	− 0.31 0.957
Metabolic parameters
pH	7.41	0.00	0.00	0.00	7.40	− 0.01 0.756	− 0.01 0.932	− 0.01 0.930	7.39	− 0.01 0.623	− 0.01 0.967	− 0.01 0.380	7.37	− 0.02 0.252	− 0.01 0.904	− 0.02 0.027	7.38	− 0.01 0.381	− 0.01 0.581	− 0.01 0.428
pCO2 (mmHg)	36.13	0.65	0.67	1.33	37.77	0.83 0.845	0.53 0.802	1.40 0.995	37.80	0.46 0.748	0.31 0.573	1.72 0.663	35.94	1.23 0.397	1.05 0.590	2.39 0.133	33.99	0.50 0.866	0.65 0.985	1.55 0.664
pO2 (mmHg)	90.79	− 3.58	− 1.00	− 2.18	92.17	− 2.82 0.640	− 1.15 0.942	− 2.21 0.994	91.16	− 2.82 0.472	− 1.15 0.712	− 2.21 0.891	89.45	− 2.92 0.701	− 2.70 0.290	− 2.22 0.965	94.03	− 1.00 0.137	− 0.38 0.727	− 0.05 0.230
Lactate (mmol/L)	1.22	0.00	0.01	0.04	1.61	− 0.02 0.774	0.01 0.895	0.10 0.780	2.51	0.04 0.896	0.00 0.860	0.12 0.883	4.58	0.03 0.987	− 0.11 0.616	0.09 0.826	3.79	0.04 0.929	− 0.06 0.698	0.05 0.761
sO2 (%)	97.17	− 0.34	− 0.18	− 0.33	97.27	− 0.32 0.947	− 0.18 0.959	− 0.27 0.730	96.87	− 0.25 0.643	− 0.08 0.603	− 0.21 0.531	96.72	− 0.46 0.528	− 0.35 0.382	− 0.53 0.309	97.17	− 0.12 0.282	− 0.03 0.474	− 0.08 0.209

BORG Borg scale, BR Breathing reserve, CM Community mask, CPET Cardiopulmonary exercise test (spiroergometry), Δ Difference to NM, EELV End-expiratory lung volume, FFP2 Filtering face piece class 2, G.M. Geometric mean, NM No mask, pCO₂ Partial pressure of carbon dioxide, pO₂ Partial pressure of oxygen, pH Potential of hydrogen in blood, RR Respiratory rate, sO₂ Haemoglobin oxygen saturation, SM Surgical mask, Tin Inspiratory time, Tex Expiratory time, Ttot Inspiratory and expiratory time, VCO₂ Carbon dioxide production, VE Minute ventilation, VE/VCO₂ Ventilation per litre of carbon dioxide, VE/VO₂ Ventilation per litre of oxygen, VO₂ Oxygen uptake, VT Tidal volume.

Masks were tested using the mask adapter (details see Methods). The situation without mask in each specific load level (pre, E1, E2, E3, post) was always used as reference. For NM geometric mean (G.M.), for the three mask types (SM, CM, FFP2) differences (Δ) to NM and p values are shown.

Significant values are in bold.