FFP2 induced breathing resistance does not affect gas exchange, metabolism and well-being during brisk walking and stair climbing - A randomized controlled trial

doi:10.21203/rs.3.rs-3837525/v1

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Research Article

FFP2 induced breathing resistance does not affect gas exchange, metabolism and well-being during brisk walking and stair climbing - A randomized controlled trial

https://doi.org/10.21203/rs.3.rs-3837525/v1

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Journal Publication

published 29 Jul, 2024

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Objectives

N95 or Type II filtering face pieces (FFP2) are often worn during work hours or on public transportation to prevent airborne infection. The aim of this randomized controlled crossover study is to assess the impact of FFP2 induced breathing resistance on pulmonary function, blood gas values and discomfort during walking and stair climbing.

Methods

N=16 healthy adults (24.8 ± 2.2 years; 10 females,) participated. Interventions included 1) six minutes of walking in a 16-meter-long hallway (612 meters) and 2) eight minutes of stair climbing in a two-story staircase (420 stairs), both with and without a FFP2 (>48 hour wash-out).

Spiroergometric data (Ventilation, breathing frequency, tidal volume, oxygen uptake and carbon dioxide exhalation (primary outcome), end tidal carbon dioxide- and oxygen pressure) and self-reported response (Perceived exertion, dyspnoea and pain) were assessed during activities. Blood gas analysis (capillary carbon dioxide- (pCO₂) (primary outcome) and oxygen partial pressure (pO₂), pH, lactate and base excess) was measured after cessation of activities. Manipulation effects (FFP2 versus no mask) were tested using repeated measures analyses of variance.

Results

Analysis showed no effect of FFP2 on pCO₂or other blood-gas parametersbut on carbon dioxide exhalation during walking: (mean 1067, SD 209 ml/min) and stair climbing (mean 1908, SD 426 ml/min) (F(15)=19.5; p<0.001; η_p²=0.566 and F(15)=14.3; p=0.002; η_p²=0.489) compared to no mask wearing (mean 1237, SD 173 ml/min; mean 1908, SD 426 ml/min). Ventilation was decreased and dyspnoea was increased by FFP2 during activities. FFP2 led to lower oxygen uptake and end tidal oxygen but higher end tidal carbon dioxide during stair climbing.

Conclusions

FFP2 decreased ventilation based on slower breathing patterns and led to limitations in pulmonary gas exchange and increased subjective dyspnoea. However, invasive diagnostics revealed no signs of clinically relevant metabolic effects during common everyday physical activities.

deadspace

hypercapnia

hypoxia

carbon dioxide

blood gas analysis

spiroergometry

aerosol

infection

Due to the Covid-19 pandemic, tight-fitting face masks such as N95 or Type II filtering face pieces (FFP2) are worn during work hours or on public transportation by a large portion of the population. Although recent evidence indicates that other mouth and nose protection such as surgical masks might have comparable effectiveness in filterin particle emission, FFP2 are increasingly preferred due to their closer fit to the face and clearly defined filter properties. Just as there is a growing body of evidence supporting the efficacy of face mask wear in limiting the risk of airborne infections [1, 2], there is an ongoing debate about potential side effects of mask-induced adaptations in respiratory function [3–5].

Mounting evidence indicates that masks might alter breathing mechanics[6]. Current meta-analyses on the effect of face masks report that increased breathing resistance indeed leads to a decrease in pulmonary function (breathing frequency, tidal volume and ventilation) during progressive exercise tests at the point of maximal exhaustion [7–9]. In contrast, the effect on pulmonary function during steady state exercise might depend on factors such as intensity or duration of the activity [7, 8]. Beyond the breathing resistance approach, exhaled air, which is trapped between face and mask, could be re-inhaled and thus leads to an increase in dead space [10]. The volume of air behind the mask contains less oxygen (17%) and more carbon dioxide (3.0%) compared to the ambient air [11]. This added fraction of dead space could lead to changes in the composition of the alveolar air especially at lower levels of energy expenditure [12].

Although meta-analyses evaluated the alterations of pulmonary gas exchange and function on a rapidly growing number of experimental studies [7–9, 13], only a small number of trials included blood gas analysis to investigate metabolic consequences. So far five studies reported no alterations of invasive measures including oxygen partial pressure (pO₂), carbon dioxide (pCO₂), pH, base excess and lactate concentration in healthy subjects [14–17] and patients with stable chronic heart failure [18] during rest. During this metabolic state adaptations in breathing patterns such as increased tidal volume are thus likely to compensate the influences of increased breathing resistance and additional dead space [7, 14–16]. Four studies report an effect on capillary blood pCO₂ during steady state ergometer cycling with vigorous intensity [14] and during maximal workload [19–21]. Contrastingly two studies on healthy subjects [17] and patients chronic heart failure [18] showed no effects during maximal workload. Two randomized controlled studies assessed the effect of surgical masks and FFP2 during low intensity exercise [22, 23]. Whereas Michalik and colleagues reported an effect of mask wearing on lactate concentrations [22], Vinettis group detected increased pCO2 levels during ergometer cycling with a mask but no changes in lactate concentration [23]. Most studies investigating the effect of mask wearing on blood gases in realistic settings have not used randomized controlled designs. Whereas two studies reported increased blood pCO2 during healthcare work [24, 25], other studies were not able to confirm these effects [26, 27]. One randomized controlled study assessed the effect of masks on blood gases during office and laboratory work and detected no effect [21].

Due to the limited evidence concerning the effect of FFP2 during activities of daily living and the contradictory results concerning ergometer and treadmill exercise, it is unclear if the aforementioned limitations in respiratory function lead to decreased blood oxygenation, elevated carbon dioxide or other clinically relevant metabolic effects during habitual activities in realistic settings.

The relevance of investigating this intensity spectrum is given by the fact that many everyday scenarios, such as occupational settings or even public transport, involve at least brief bouts of low to moderate intensity physical activity. To evaluate not only ventilation and pulmonary gas exchange but also the effects on metabolism and discomfort, both invasive and non-invasive outcomes are relevant. Furthermore, additional studies are necessary to examine a possible association between the frequently mentioned negative subjective consequences of mask-wearing [8, 28] and questionable metabolic changes.

To address the sketched gap of knowledge, we conducted an experimental study on the effects of wearing a FFP2/N95 during walking and stair climbing on spiroergometric data, blood gas analysis outcomes and self-reported response.

We hypothesized that the FFP2/N95 respirators have a detrimental effect on (1) carbon dioxide exhalation which (2) leads to increased blood pCO₂ during both ground walking and stair climbing. Furthermore, we hypothesized that FFP2 wearing had (3) a detrimental effect on other spiroergometric and blood gas analysis outcomes and (4) an effect on subjective response when compared to no mask wearing during walking or stair climbing.

Study Design and Ethical Aspects

This study has a randomized controlled cross-over design and is approved by the ethics committee of the Department of Psychology and Sports Sciences of the Goethe University (2022-55, approved 30/08/2022). The trial was registered a priori (German Register for Clinical Trials, DRKS-ID: DRKS00030085, date of first trial registration 25/08/2022) and conducted in accordance with the ethical standards set down by the declaration of Helsinki with its recent modification of 2013 (Fortaleza)[29].

Participants

Participants were recruited between August and October 2022 in a university in Germany. Eligibility criteria included being between 18 and 50 years of age with no (medical or psychosocial) contraindication against vigorous physical activity. Due to the experimental design, authors had direct contact to the participants and thus could identify individual participants during data collection. During analysis data was anonymized. Exclusion criteria were cardiovascular-, pulmonary-, or advanced degenerative musculoskeletal diseases, pregnancy and not completely healed musculoskeletal injury (that affect subjective quality of life or physical performance during walking and stair climbing).

Sample size calculations were performed based on an earlier study comparing CO2 kinetics during steady state exercise with a FFP2 and a surgical mask against a no mask control [14]. A calculation based on an effect size of Cohen’s d = 0.39 (Partial η² 0.136) a significance level of 5% and an 80% power resulted in a sample size of at least 11 participants adopting a crossover design with 4 measurements in repeated measures analysis of variance (rmANOVA). Calculating with a drop-out rate of 20%, a minimum of 13 participants needed to be included in this study.

Before study participation, participants were informed on voluntary participation and signed a written informed consent. Eligibility, exclusion and randomization scheme of the protocol is shown in the flow diagram in Fig. 1.

Interventions

All participants performed two interventions (walking and stair climbing), each once with and once without a fold-flat type FFP2 (IMSTec GmbH, Klein-Winternheim, Germany) on two different trial days separated by a minimum of 48 hours. The manipulation (FFP2 or no mask) order was randomized (simple balanced randomization using www.randomizer.org).

Each trial day consisted of a six-minute walking phase, followed by an eight-minute stair climbing phase with ten minutes resting time without wearing a mask in-between. Order allocation was done blinded, the participants were blinded to the respective manipulation until the beginning of each intervention.

Each session was performed at a comparable time of the day (± 2 h) and at days with comparable routines (i.e. working days). Participants had to avoid vigorous physical activities in the 48 hours preceding each test and to maintain their habitual diet behaviour during the timeframe of all three interventions. Furthermore, participants were requested not to take any food or drinks (except for water) in the period of 2 hours prior to each examination.

At each session, participants first rested for five minutes in a seated position without wearing a FFP2 mask. During this time baseline data for spiroergometric outcomes, blood gas analysis and subjective response were assessed. After that the 6 minutes ground level walking phase was rolled out in a hallway. The walking speed was standardized and Participants walked 612 meters (1,7 meters per second). Between the walking and stair climbing intervention, a resting period of ten minutes was held during which the participants were not manipulated (did not wear a mask). Afterwards, the 8 minutes stair climbing was performed in on in a two-story staircase. Again, the speed was standardized and all participants completed 24 floors upstairs and downstairs on a standard stairway (stair height 16.5 centimeters, 69.3 meters of elevation).

Outcomes

During baseline testing at each trial day and during the thorough interventions, spiroergometric data and heart rate were measured continuously. Participants self-reported perception was asked every two minutes using standardized scales. The capillary drawings for blood gas analysis were done at the end of baseline testing and immediately after both interventions at the ear lobe with participants in a seated position.

Baseline examination including standard anthropometrical values, educational status (school and study years), habitual physical activity and sedentary behaviour (International Physical Activity Questionnaire IPAQ) [30, 31] took place before the first intervention. Furthermore, participants underwent a step incremental exercise test (7 or 8 km/h at the start depending on individual fitness; 7° inclination; 0,5 km/h increment every 30 seconds) on a treadmill until volitional exhaustion to assess maximal oxygen uptake (VO₂max), maximal heart rate and maximal respiratory exchange ratio. For spiroergometric measures during VO₂max, baseline and intervention testing a valid and reliable portable analyser was applied (K5, Cosmed, Werneck, Germany) [32].

Baseline data for spiroergometric outcomes, blood gas analysis and subjective response were assessed after 5 minutes of sitting without a FFP2 at the start of both trial days. Spiroergometric measures during baseline and interventions included ventilation (in litres per minute, l/min), breathing frequency (breaths per minute), tidal volume (in litres, l), oxygen uptake (VO2 in millilitres per minute, ml/min), carbon dioxide exhalation (VCO2 in millilitres per minute, ml/min), respiratory exchange ratio, end tidal carbon dioxide (PetCO2 in millimetres of mercury, mmHg) and end tidal oxygen pressure (PetO2 in millimetres of mercury, mmHg). For blood gas analysis, capillary blood (100 µl) was drawn from an earlobe of the participant and analysed using a validated on-site device (epoc® Blood Analysis System, Epocal Inc., Ottawa, Ontario, Canada) [33]. Outcomes included pH, carbon dioxide partial pressure (pCO2 in millimetres mercury, mmHg), oxygen partial pressure (pO2 in mm/Hg), lactate (mmol per litre, mmol/l) and base excess (BE in mmHg). Subjective response included perceived exertion, based on a 15-point Borg Scale ranging from “very very light” (lowest rating 6) to “very very hard” (highest rating 20) [34], and dyspnoea based on a modified Borg Scale with the same range [35]. Participants were furthermore asked to rate their perception of pain based on a numeric rating scale ranging from “no pain” (lowest rating 0) to “most severe pain imaginable (highest rating 10) [36].

Data Analysis and Statistics

We applied Microsoft Excel (Version 16.68) for data processing, Jamovi (Version 2.3.19) for data analysis, and Prism (Version 9) for data presentation. Descriptive data were reported as means and standard deviations (baseline values and post intervention values) or 95% confidence intervals.

Repeated measures analyses of variance (rmANOVA) were applied to analyse the effect of the manipulation (FFP2 versus no mask) on all outcomes and differences between baseline values of both trial days. In a second step, the impact of potential confounders including sex, age, weight, BMI, physical activity and maximal oxygen uptake capacity was assessed using analysis of covariance (ANCOVA). Pearson correlation was applied to detect associations between subjective measures and spiroergometric or blood gas analysis which were affected by FFP2 application. We considered p ≤ 0.05 as statistically significant and applied Bonferroni corrections for multiple comparisons. Due to 34 between-manipulations-comparisons p ≤ 0.002 is considered statistically significant.

Demographic and Baseline Data

Sixteen (16) humans (24.8 ± 2.2 years; 10 females, 6 males) were recruited, participated in this study and completed the study protocol without any adverse event (Fig. 1). 9 participants started without a mask and 7 with the FFP2 condition. Demographics, including anthropometric, physical activity and physical performance data, are shown in Table 1.

Baseline data of spiroergometric, blood gas and subjective parameters for trials with and without a manipulation (FFP2 and no mask control) are listed in Table 2. No differences between baseline data occurred.

Table 1

Demographics, self-reported exercise amounts and exercise capacity of our sample.
Outcome / Dimension	Unit	Mean, Standard Deviation
Anthropometric Data
Age	Years	24.8, 2.32
Weight	kg	70.1, 13.4
Height	cm	172, 10.2
Body mass index	kg/m²	23.4, 2.13
Physical activity via International Physical Activity Questionnaire
Vigorous physical activity	h/week	1.31, 0.54
Moderate physical activity	h/week	1.05, 0.88
Walking	h/week	1.31, 0.76
Sedentary behaviour	h/week	5.06, 2.37
Incremental exercise test
Maximal running speed	kg/h	11.6, 1.44
Maximal heart rate	Beats per minute	191, 8.67
Maximal oxygen uptake	ml/min*kg bodyweight	55.0, 9.04
Respiratory exchange ratio		1.20, 0.13

Table 2

Descriptive data and Analyses of Variance (ANOVAs) results of baseline values (FFP2 vs. no mask) for spiroergometric data (Ventilatory outcomes, pulmonary gas exchange measures and heart rate), blood gas analysis measures and subjective outcomes during walking and stair climbing
Baseline Data on both trial days
Outcomes (Units)	Mean, Standard Deviation		ANOVA
Outcomes (Units)	Trial 1 (Walk NM)	Trial 2 (Walk FFP2)	ANOVA
Breathing frequency (Breaths per minute)	16, 4	16, 3	p = 0.891, n² = 0.001, F(15) = 0.019
Tidal volume (Liter)	0.70, 0.19	0.74, 0.23	p = 0.539, n² = 0.026, F(15) = 0.395
Ventilation (Liter per minute)	10.70, 2.81	11.10, 2.18	p = 0.561, n² = 0.023, F(15) = 0.354
Heart rate (beats per minute)	79, 15	77, 14	p = 0.459, n² = 0.037, F(15) = 0.577
Oxygen uptake (Milliliters per minute)	356, 92	375, 90	p = 0.530, n² = 0.027, F(15) = 0.413
Carbon dioxide exhalation (Milliliters per minute)	297, 72	305, 60	p = 0.734, n² = 0.008, F(15) = 0.120
Respiratory exchange ratio	0.84, 0.07	0.83, 0.07	p = 0.483, n² = 0.033, F(15) = 0.516
End tidal oxygen pressure (Millimeters of mercury)	110, 3.97	110, 3.79	p = 0.708, n² = 0.010, F(15) = 0.146
End tidal carbon dioxide pressure (Millimeters of mercury)	33.8, 3.17	32.9, 2.82	p = 0.283, n² = 0.076, F(15) = 1.24
Oxygen partial pressure (Millimeters of mercury)	73.8, 5.85	76.7, 8.89	p = 0.166, n² = 0.124, F(15) = 2.12
Carbon dioxide partial pressure (Millimeters of mercury)	37.6, 3.18	37.1, 4.01	p = 0.439, n² = 0.040, F(15) = 0.633
pH value	7.42, 0.0148	7.43, 0.0151	p = 0.297, n² = 0.072, F(15) = 1.17
Base Excess (Millimoles per liter)	0.200, 2.01	0.231, 2.04	p = 0.894, n² = 0.001, F(15) = 0.019
Laktate (Millimoles per liter)	0.969, 0.311	0.999, 0.286	p = 0.686, n² = 0.011, F(15) = 0.170
Perceived exertion (Range 6–20)	6.56, 1.09	6.69, 0.79	p = 0.633, n² = 0.016, F(15) = 0.238
Perceived dyspnoea (Range 6–20)	7.19, 1.33	7.50, 1.51	p = 0.484, n² = 0.033, F(15) = 0.516
Perceived pain (Range 1–10)	1.25, 1.00	1.31, 0.70	p = 0.849, n² = 0.003, F(15) = 0.038

Table 3 Descriptive data and Analyses of Variance (ANOVAs) results for between-manipulations-comparisons (FFP2 vs. no mask) for spiroergometric data (Ventilatory outcomes, pulmonary gas exchange measures and heart rate), blood gas analysis measures and subjective outcomes during walking and stair climbing. *indicates significant between-manipulations-effects.

Between-Manipulations-Comparisons

Outcomes

(Units)

Walking

Stair Climbing

Mean,

Standard Deviation

ANOVA

Mean,

Standard Deviation

ANOVA

No mask

FFP2

No mask

FFP2

Breathing frequency

(Breaths per minute)

29.0,

5.60

24.8,

4.77

p < .001*

n² = 0.658

F(15) = 28.9

35.9,

4.63

32.3,

6.34

p = 0.04

n² = 0.429

F(15) = 11.2

Tidal volume (Liter)

1.28,

0.24

1.22,

0.17

p = 0.22

n² = 0.1

F(15) = 1.65

1.66,

0.281

1.56,

0.384

p = 0.078

n² = 0.192

F(15) = 3.57

Ventilation

(Liter per minute)

35.1,

3.77

28.9,

5.88

p < 0.001*

n² = 0.714

F(15) = 37.4

57.3,

9.13

48.0,

9.35

p < 0.001*

n² = 0.88

F(15) = 110

Heart rate

(Beats per minute)

117,

18.8

116,

15.0

p = 0.488

n²= 0.033

F(15) = 0.51

150,

16.3

155,

18.3

p = 0.065

n²= 0.209

F(15) = 3.96

Oxygen uptake

(Milliliters per minute)

1522,

211

1347,

313

p = 0.013

n² = 0.348

F(15) = 8.02

2405,

501

2148,

450

p < .001*

n² = 0.685

F(15) = 32.6

Carbon dioxide exhalation

(Milliliters per minute)

1237,

173

1067,

209

p < .001*

n² = 0.566

F(15) = 19.5

2087,

376

1908,

426

p = 0.002*

n² = 0.489

F(15) = 14.3

Respiratory exchange ratio

0.82,

0.05

0.8,

0.05

p = 0.381

n² = 0.051

F(15) = 0.814

0.88,

0.06

0.89,

0.06

p = 0.538

n² = 0.026

F(15) = 0.397

End tidal oxygen pressure

(Millimeters of mercury)

103,

4.73

100,

5.58

p = 0.024

n²= 0.297

F(15) = 6.33

104,

4.01

101,

4.27

p < .001*

n²= 0.817

F(15) = 67.2

End tidal carbon dioxide pressure

(Millimeters of mercury)

39.5,

3.78

40.9,

3.81

p = 0.0511

n² = 0.230

F(15) = 4.49

39.8,

3.79

43.2,

4.25

p < .001*

n² = 0.569

F(15) = 19.8

Oxygen partial pressure

(Millimeters of mercury)

83.5,

9.26

(n=16)

81.0,

7.68

(n=14)

p = 0.179

n² = 0.125

F(14) = 2.00

80.4,

10.7

(n=14)

80.2,

7.95

(n=14)

p = 0.994

n² = 0.000

F(13) = 0.00006

Carbon dioxide partial pressure

(Millimeters of mercury)

37.4,

3.25

(n=16)

37.7,

3.48

(n=14)

p = 0.575

n² = 0.025

F(13) = 0.330

37.3,

3.35

(n=14)

37.2,

4.10

(n=16)

p = 0.4111

n² = 0.053

F(13) = 0.721

pH value

7.43,

0.0113

(n=16)

7.43,

0.0128

(n=14)

p = 0.973

n²= 0.000

F(13) = 0.001

7.42,

0.0170

(n=14)

7.41,

0.0306

(n=16)

P = 0.148

n²= 0.156

F(13) = 2.27

Base Excess

(Millimoles per liter)

0.163,

1.98

(n=16)

0.507,

1.98

(n=14)

p = 0.609

n² = 0.021

F(13) = 0.274

-0.121,

2.56

(n=14)

-0.888,

2.42

(n=16)

p = 0.114

n² = 0.181

F(13) = 2.88

Lactate

(Millimoles per liter)

0.906,

0.329

(n=16)

0.988,

0.318

(n=14)

p = 0.346

n² = 0.069

F(13) = 0.958

1.68,

1.08

(n=14)

1.71,

1.02

(n=16)

p = 0.787

n² = 0.006

F(13) = 0.076

Perceived exertion

(Range 6-20)

8.45,

1.21

9.23,

1.60

p = 0.074

n² = 0.197

F(15) = 3.68

11.2,

1.56

11.8,

1.63

p = 0.142

n² = 0.138

F(15) = 2.40

Perceived dyspnoea

(Range 6-20)

8.69,

1.20

11.0,

1.48

p < .001

n²= 0.605

F(15) = 22.9

11.2,

1.85

12.9,

1.58

P = 0.003

n²= 0.462

F(15) = 12.9

Perceived pain

(Range 1-10)

1.34,

0.74

1.63,

1.06

p = 0.191

n² = 0.111

F(15) = 1.88

2.33,

1.45

1.93,

1.16

p = 0.120

n² = 0.153

F(15) = 2.71

Spiroergometric data

Descriptive data and the detailed results of the between-manipulations-comparisons for the spiroergometric data of the walking and stair climbing phase are depicted in Table 3. Wearing a FFP2 decreased breathing frequency, ventilation and carbon dioxide exhalation during walking. During stair climbing, ventilation, oxygen uptake, carbon dioxide exhalation and end tidal pressures for oxygen and carbon dioxide were affected by FFP2. Furthermore, FFP2 wearing led to a tendency for lower oxygen uptake and end tidal oxygen pressure during walking and a tendency for decreased breathing frequency during stair climbing. Heart rate and tidal volume during both activities were not affected by mask wearing. Figure 2 shows 95% confidence intervals of spiroergometric outcomes. Analysis of covariance revealed a significant interaction between VO₂max and the effect of FFP2 wearing on oxygen uptake and carbon dioxide exhalation during stair climbing. Other covariates (sex, age, weight, BMI, physical activity) showed no significant interaction with between-manipulations effects.

Blood gas analysis

Descriptive data and the detailed results of the between-manipulations-comparisons for blood gas analysis outcomes of the walking and stair climbing phase are depicted in Table 3. Figure 3 shows 95% confidence intervals of blood gas analysis outcomes. Although there were notable differences between baseline and post intervention values for base excess and lactate, blood gas analysis outcomes after physical activities with and without a mask were in a comparable range and ANOVAs showed no significant between-manipulations-differences.

Self-reported outcomes

Descriptive data and the detailed results of the between-manipulations-comparisons for all subjective outcomes of the walking and stair climbing phase are depicted in Table 3. Participants perceived more dyspnoea during walking when a FFP2 was applied. Figure 3 shows 95% confidence intervals of self-report outcomes. No significant interaction with any tested covariates occurred. Mean values of perceived exertion were higher during stair climbing than during walking but ANOVAs indicated no effect of FFP2 wearing on exertion or pain during both physical activities. Pearson correlation of perceived dyspnoea with spiroergometric outcomes and covariates showed no significant associations.

Hypotheses verification

We found a decrease in ventilation and breathing frequency but comparable tidal volume during walking and stair climbing when an FFP2 mask is worn. These alterations seem to effect carbon dioxide exhalation during both activities and oxygen uptake during stair climbing. Our first hypothesis thus can be verified. However, our data showed no impact of FFP2 wearing on blood carbon dioxide or oxygen levels immediately after both exercise interventions which leads to a rejection of our second hypothesis. Against our third hypothesis, other invasive markers of clinically relevant metabolic effects remained unaffected as well. Participants perceived comparable activity-related exertion but more dyspnoea when a FFP2 was worn during walking. Hypothesis four thus can partly be verified. Increased dyspnoea was not directly associated with the mask induced decrease in ventilatory performance or pulmonary gas exchange.

Mechanisms and effect discussion

The most relevant novelty of our study is the combination of spiroergometric measurements and invasive blood gas analysis during low to moderate intensity physical activity. So far only two studies combined breathing gas- and blood gas analyses and compared the effect of surgical masks and FFP2 to a no-mask control condition at the point of maximal exhaustion during a incremental exercise test [17, 18]. In both studies, Fikenzer and colleagues reported significant effects on ventilation and oxygen uptake whereas blood gas analyses revealed no resulting alterations in capillary pO₂, pCO₂ or pH in healthy participants [17] and patients with heart failure [18]. We extend these findings not only by assessing low to moderate intensity but also by analysing carbon dioxide exhalation and end tidal O₂ and CO₂ pressure. Using this approach, we are able to confirm that decreased ventilation leads to differences in end tidal pressure and gas exchange even during low to moderate intensity physical activity. Furthermore, our data indicates that physical fitness has an impact on FFP2 induced alterations of oxygen uptake and carbon dioxide exhalation during moderate intensity physical activity. In line with earlier research on exhaustive exercise [17, 18] and physical rest [14–17, 23], we confirm that the limitations in pulmonary gas exchange during exercise seem to be rather small and do not affect capillary pCO₂ and pO₂ immediately after exercise cessation. In contrast to these findings one study on vigorous intensity steady state exercise in healthy subjects [14] and one study on progressive exercise until exhaustion in patients with coronary artery diseases or hypertension [19] included blood gas analysis during exercise but no breathing gas measurements and were able to detect significant effects on pCO₂ and corresponding differences in pH, base excess and hydrogen carbonate [14, 19]. Overall, current evidence indicates that these metabolic effects might be associated with higher exercise intensity. Although the differences in methodology between studies with [17, 18] and without [14, 19] spiroergometric testing seem obvious, it is unclear if a tighter fit of FFP2 masks due to the combination with rubber masks or discrepancies of the blood sampling time points could have influenced the results.

Limitations and methodological considerations

Some frequently discussed limitations of studies which applied spiroergometry to measure the impact of face masks on ventilation and gas exchange relate to methodological short comings. The tight fit of the rubber mask over the FFP2 might lead to increased breathing resistance and could reduce the space between FFP2 and face. Another problem is a potential air-leakage between facial skin, protective mask and rubber-spiroergometry. In a direct response letter to the first experiment of Fikenzer and colleagues [17], a group of experts discusses that, based on the assumption of linear relationships between power output, oxygen consumption and cardiac output, gross ventilation might has been underestimated due to air leakage during expiration [37]. Within our study, the power output between the masked and unmasked exercise condition was matched and the mean heart rate was in a comparable range. Anyhow, our data also show significantly lower ventilation, oxygen uptake and carbon dioxide exhalation. These changes might be overestimated due to the described limitations. In order to control potential problems with ventilation-based measures (tidal volume and ventilation), we additionally analysed end tidal concentrations of oxygen and carbon dioxide and were able to detect significant effects of FFP2 application on both outcomes. Even assuming an undetected measurement error due to leakage, the changes in oxygen and carbon dioxide content in the exhaled air imply a decrease in ventilation in the masked exercise condition. Our data indicates that these changes in pulmonary gas exchange during low to moderate intensity physical activity have no effect on blood gases or other metabolic outcomes if the sampling was done immediately after exercise cessation. Looking at the origin and magnitude of the observed changes, it thus can be concluded that it is rather a limitation of CO₂ elimination than an increased production due to alterations in energy metabolism.

In line with current evidence [8], participants in our experiment perceived increased dyspnoea during walking and stair climbing when a FFP2 was worn. Our results confirm meta-analytic data which evaluated the effects of different mask types and indicated that although surgical masks have an effect on perceived exertion, a similar effect does not occur with FFP2 [8]. It is discussed, that the materials and construction of surgical masks might induce more discomfort due to mask suction and deformation during intense breathing [19]. Against earlier findings on a linear relation of perceived exertion with breathing frequency and heart rate [38], we found no association between the subjective and objective effects of FFP2 wearing.

Practical implications for everyday life and research

FFP2 can be applied during habitual physical activities such as climbing multiple flights of stairs or walking a few hundred meters indoors without risking harm. Public information campaigns should highlight that perceived discomfort or dyspnoea is not necessarily linked to negative or even harmful metabolic effects of protective masks.

Future studies need to evaluate if higher carbon dioxide levels, higher cardiac output or increased breathing resistance during more intense physical activities such as structured exercise or physical labour could lead to a detrimental metabolic response or counteract beneficial exercise effects.

Face masks such as FFP2 induce small changes in pulmonary function and gas exchange during low to moderate intensity physical activity. Invasive metabolic parameters, blood carbon dioxide and oxygen values were in a physiological range and did not affect subjective wellbeing. Healthy adults thus seem to be able to physiologically compensate the impact of mouth and nose protections masks during physical activities with low to moderate intensity. Consequently, our data underlines that mask wearing in most settings without the option to maintain social distancing over a limited timeframe does not lead to detrimental health consequences. Further studies need to assess the effects of prolonged and repeated mask application especially in real-life settings (shared workspace, long distance public transport). Furthermore, studies need to evaluate the impact of protective masks during habitual physical activity with moderate to vigorous intensity (i.e. physical labour in crowded areas) to further out rule potential effects on well-being and metabolism.

Ethics approval and consent to participate: The study design was approved by the ethics committee of the Department of Psychology and Sports Sciences of the Goethe University (2022-55, Approved 2022/08/30).

Consent for publication: Not applicable

Availability of data and material: Data are available upon reasonable request per institutional policy (Contact: Tobias Engeroff, [email protected]).

Competing interests: None declared.

Funding: This research study was funded through the German „Berufsgenossenschaft für Gesundheitsdienst und Wohlfahrtspflege“ (BGW).

Authors` contributions: Study concept—TE and LV. Study design—TE, LV and NH. Data acquisition—TE and NH. Data analysis—TE, NH and DN. Manuscript preparation—TE. Manuscript editing— TE, NH, DN, AN and DG. All authors read and approved the final manuscript.

Acknowledgements: Not applicable.

Howard J, Huang A, Li Z, Tufekci Z, Zdimal V, van der Westhuizen H-M, et al. An evidence review of face masks against COVID-19. Proc Natl Acad Sci USA. 2021;118:e2014564118.
Abboah-Offei M, Salifu Y, Adewale B, Bayuo J, Ofosu-Poku R, Opare-Lokko EBA. A rapid review of the use of face mask in preventing the spread of COVID-19. International Journal of Nursing Studies Advances. 2021;3:100013.
Elisheva R. Adverse Effects of Prolonged Mask Use among Healthcare Professionals during COVID-19. J Infect Dis Epidemiol [Internet]. 2020 [cited 2021 Nov 29];6. Available from: https://clinmedjournals.org/articles/jide/journal-of-infectious-diseases-and-epidemiology-jide-6-130.php?jid=jide
Scheid JL, Lupien SP, Ford GS, West SL. Commentary: Physiological and Psychological Impact of Face Mask Usage during the COVID-19 Pandemic. IJERPH. 2020;17:6655.
Lazzarino AI, Steptoe A, Hamer M, Michie S. Covid-19: Important potential side effects of wearing face masks that we should bear in mind. BMJ. 2020;m2003.
Lässing J, Falz R, Pökel C, Fikenzer S, Laufs U, Schulze A, et al. Effects of surgical face masks on cardiopulmonary parameters during steady state exercise. Sci Rep. 2020;10:22363.
Engeroff T, Groneberg DA, Niederer D. The Impact of Ubiquitous Face Masks and Filtering Face Piece Application During Rest, Work and Exercise on Gas Exchange, Pulmonary Function and Physical Performance: A Systematic Review with Meta-analysis. Sports Med - Open. 2021;7:92.
Zheng C, Poon ET-C, Wan K, Dai Z, Wong SH-S. Effects of Wearing a Mask During Exercise on Physiological and Psychological Outcomes in Healthy Individuals: A Systematic Review and Meta-Analysis. Sports Med [Internet]. 2022 [cited 2022 Sep 8]; Available from: https://link.springer.com/10.1007/s40279-022-01746-4
Litwinowicz K, Choroszy M, Ornat M, Wróbel A, Waszczuk E. Bayesian network meta-analysis of face masks’ impact on human physiology. Sci Rep. 2022;12:5823.
Roberge RJ, Coca A, Williams WJ, Palmiero AJ, Powell JB. Surgical mask placement over N95 filtering facepiece respirators: Physiological effects on healthcare workers. Respirology. 2010;15:516–21.
Roberge RJ, Coca A, Williams WJ, Powell JB, Palmiero AJ. Physiological impact of the N95 filtering facepiece respirator on healthcare workers. Respir Care. 2010;55:569–77.
Sinkule EJ, Powell JB, Goss FL. Evaluation of N95 respirator use with a surgical mask cover: effects on breathing resistance and inhaled carbon dioxide. Ann Occup Hyg. 2013;57:384–98.
Shaw K, Zello GA, Butcher S, Ko J, Bertrand L, Chilibeck PD. The Impact of Face Masks on Performance and Physiological Outcomes during Exercise: A Systematic Review and Meta-analysis. Appl Physiol Nutr Metab. 2021;
Grimm K, Niederer D, Nienhaus A, Groneberg DA, Engeroff T. Blood gas levels, cardiovascular strain and cognitive performance during surgical mask and filtering face piece application. Sci Rep. 2022;12:9708.
Sammito S, Müller GPJ, Erley OM, Werner A. Impact of in-flight use of FFP2 masks on oxygen saturation: an experimental crossover study. Journal of Travel Medicine. 2021;taab018.
Tamimi A, Dahbour S, Al-Btush A, Al-Qudah A, Masri A, Al-Ghanem S, et al. Facemask wearing does not impact neuro-electrical brain activity. Sci Rep. 2022;12:9056.
Fikenzer S, Uhe T, Lavall D, Rudolph U, Falz R, Busse M, et al. Effects of surgical and FFP2/N95 face masks on cardiopulmonary exercise capacity. Clin Res Cardiol. 2020;109:1522–30.
Kogel A, Hepp P, Stegmann T, Tünnemann-Tarr A, Falz R, Fischer P, et al. Effects of surgical and FFP2 masks on cardiopulmonary exercise capacity in patients with heart failure. Rubino AS, editor. PLoS ONE. 2022;17:e0269470.
Fischer P, Blumenauer D, Egger F, Fikenzer S, Zimmer A, Kulenthiran S, et al. Effects of Medical Face Masks on Physical Performance in Patients With Coronary Artery Disease or Hypertension. The American Journal of Cardiology. 2022;173:1–7.
Rudi W-S, Maier F, Schüttler D, Kellnar A, Strüven AK, Hamm W, et al. Impact of Face Masks on Exercise Capacity and Lactate Thresholds in Healthy Young Adults. International Journal of Sports Physiology and Performance. 2022;17:655–8.
Marek E-M, Van Kampen V, Jettkant B, Kendzia B, Strauß B, Sucker K, et al. Effects of wearing different face masks on cardiopulmonary performance at rest and exercise in a partially double-blinded randomized cross-over study. Sci Rep. 2023;13:6950.
Michalik K, Smolarek M, Borkowski J, Tchorowski M, Korczuk N, Gorczyca P, et al. Changes in Reaction Time, Balance and Neuroplasticity after Exercise with a Face Mask in Male Adults with Mild COVID-19 Symptoms. Healthcare (Basel). 2023;11:2800.
Vinetti G, Micarelli A, Falla M, Randi A, Dal Cappello T, Gatterer H, et al. Surgical masks and filtering facepiece class 2 respirators (FFP2) have no major physiological effects at rest and during moderate exercise at 3000-m altitude: a randomised controlled trial. Journal of Travel Medicine. 2023;30:taad031.
Roeder G, Bilir A, Graf A, Baron DM. Capillary carbon dioxide tension increases in hospital staff wearing filtering facepiece masks: a prospective crossover study. ERJ Open Res. 2023;9:00186–2023.
Patel S, Mohapatra E, Suganthy A, Shah S, Abraham J, Nanda R, et al. A pilot study to evaluate the changes in venous blood gas parameters and hypoxia biomarkers in health care workers using different kinds of masks. Lung India. 2023;40:134.
Pasli S, Imamoglu M, Beser MF, Sahin AS, Ilhan E, Yadigaroglu M. Examination of the Effects of 4-Hour Nonvalved Filtering Facepiece Respirator Use on Blood Gas Values of Health Care Professionals: A Before and After Study. Journal of Emergency Nursing. 2022;48:423-429.e1.
Hussain SY, Khanuja S, Panjiar P, Jain D, Batt KM. Effect of N95 Filtering Facepiece Respirator on Venous Blood Carbon Dioxide Levels and Hemodynamic Changes in Health Care Workers. Indian J Occup Environ Med. 2023;27:38–41.
Glänzel MH, Barbosa IM, Machado E, Prusch SK, Barbosa AR, Lemos LFC, et al. Facial mask acute effects on affective/psychological and exercise performance responses during exercise: A meta-analytical review. Front Physiol. 2022;13:994454.
World Medical Association Declaration of Helsinki: Ethical Principles for Medical Research Involving Human Subjects. JAMA. 2013;310:2191.
Hagströmer M, Oja P, Sjöström M. The International Physical Activity Questionnaire (IPAQ): a study of concurrent and construct validity. Public Health Nutrition [Internet]. 2006 [cited 2018 Oct 23];9. Available from: http://www.journals.cambridge.org/abstract_S1368980006001261
Sjöström M, Ainsworth B, Bauman A, Bull F, Hamilton-Craig C, Sallis J. Guidelines for data processing analysis of the International Physical Activity Questionnaire (IPAQ) - Short and long forms. 2005;
Perez-Suarez I, Martin-Rincon M, Gonzalez-Henriquez JJ, Fezzardi C, Perez-Regalado S, Galvan-Alvarez V, et al. Accuracy and Precision of the COSMED K5 Portable Analyser. Front Physiol. 2018;9:1764.
Nichols JH, Rajadhyaksha A, Rodriguez M. Evaluation of the Enterprise Point-of-Care (EPOC) System for Blood Gas and Electrolyte Analysis. Point of Care: The Journal of Near-Patient Testing & Technology. 2008;7:7–11.
Borg GA. Psychophysical bases of perceived exertion. Med Sci Sports Exerc. 1982;14:377–81.
Wilson RC, Jones PW. A comparison of the visual analogue scale and modified Borg scale for the measurement of dyspnoea during exercise. Clinical Science. 1989;76:277–82.
Ferreira-Valente MA, Pais-Ribeiro JL, Jensen MP. Validity of four pain intensity rating scales. Pain. 2011;152:2399–404.
Hopkins SR, Stickland MK, Schoene RB, Swenson ER, Luks AM. Effects of surgical and FFP2/N95 face masks on cardiopulmonary exercise capacity: the numbers do not add up. Clin Res Cardiol. 2020;109:1605–6.
Georgi C, Haase-Fielitz A, Meretz D, Gäsert L, Butter C. The Impact of Commonly-Worn Face Masks on Physiological Parameters and on Discomfort During Standard Work-Related Physical Effort. Deutsches Ärzteblatt international [Internet]. 2020 [cited 2023 Jan 19]; Available from: https://www.aerzteblatt.de/10.3238/arztebl.2020.0674

No competing interests reported.

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FFP2 induced breathing resistance does not affect gas exchange, metabolism and well-being during brisk walking and stair climbing - A randomized controlled trial

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INTRODUCTION

METHODS

Study Design and Ethical Aspects

Participants

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Outcomes

Data Analysis and Statistics

RESULTS

Demographic and Baseline Data

Spiroergometric data

Blood gas analysis

Self-reported outcomes

DISCUSSION

Hypotheses verification

Mechanisms and effect discussion

Limitations and methodological considerations

Practical implications for everyday life and research

CONCLUSION

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References

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