We study the effect of surgical masks on cardiopulmonary function based on a cardiopulmonary exercise test (CPET). This study shows that surgical masks reduce cardiopulmonary exercise capacity and ventilation in healthy young subjects and wearing masks might affect aerobic exercise capacity more in female subjects than in male subjects.
We study the effect of surgical masks on cardiopulmonary function based on a cardiopulmonary exercise test (CPET). This study shows that surgical masks reduce cardiopulmonary exercise capacity and ventilation in healthy young subjects and wearing masks might affect aerobic exercise capacity more in female subjects than in male subjects.
Wearing a face mask in public areas might impede the spread of an infectious disease by preventing both the inhalation of infectious droplets and their subsequent exhalation and dissemination1. Although the effect of reducing the risk of transmission of respiratory viruses remains controversial, wearing masks remains one of the major ways people in the community have chosen to prevent the spread of droplets among individuals in daily life2,3,4.
Different types of masks have different effects on increasing expiratory resistance and inspiratory resistance5. Meanwhile, during a respiratory disease pandemic, people (including healthy people and patients with cardiopulmonary diseases) might need to wear masks for a long time to perform daily activities. However, there are few studies on the effect of wearing a mask on cardiopulmonary function.
Cardiopulmonary exercise testing (CPET) is an important means of cardiovascular rehabilitation risk assessment by reflecting various parameters of the body's cardiopulmonary function during exercise with increasing load and is considered to be the gold standard for cardiopulmonary reserve testing2. We use CPET under different conditions (mask-on and mask-off) to study the changes in cardiopulmonary function parameters of healthy young subjects, to evaluate the interference of masks objectively and quantitatively on cardiorespiratory reserve and exercise endurance from a novel methodological perspective to guide the application of masks in particular respiratory infectious disease pandemic. Although FFP2/N95 has been suggested to be more efficacious than surgical masks at reducing exposure to viral infections, medical-surgical masks are more convenient and common to obtain and use than FFP2/N95 face masks. Thus, this study focuses only on the effects of medical surgical masks on cardiopulmonary function.
The clinical project was approved by the Medical Ethics Association of the Fifth Affiliated Hospital of Guangzhou Medical University (No. KY01-2020-06-06) and has been registered at the China Clinical Trial Registration Center (No. ChiCTR2000033449) and entitled "The effects of masks on cardiopulmonary and lower limb function".
1. Participant recruitment
2. Laboratory settings and equipment preparation
3. Spirometry
4. Cardiopulmonary exercise test (CPET)
5. CPET post testing
6. Statistical analysis
Ten subjects (five males and five females) from the Department of Rehabilitation Medicine at Guangzhou Medical University were recruited in this pilot study. The participants had similar baseline characteristics, such as age (mean age: male 21.00 ± 1.58 years; female 21.20 ± 0.45 years) and physical fitness [sports activity and body mass index (BMI)]. There were no significant differences in age, height, or BMI between the male and female groups. Moreover, for the spirometry, the female group showed lower FVC, lowered forced expiratory volume in 1 s (FEV1), lower MVV, and lowered peak expiratory flow (PEF) compared with the male group (Table 1).
The results of CPET under different conditions (mask-on and mask-off) are depicted in Table 2. For exercise tolerance and cardiac function, compared to the mask-off condition, both male and female groups during the mask-on condition showed a significant decrease in anaerobic threshold per kilogram, i.e., VO2/kg (LT), and oxygen pulse, i.e., O2/HR (peak), whereas no significant differences in oxygen uptake related to work rate, i.e., ΔVO2/ΔWR and HR (rest). Moreover, the male group also showed a significant decrease in HR (rest), and the female group showed a significant decrease in peak oxygen uptake per kilogram, i.e., VO2/kg (peak) during the mask-on condition. For ventilatory function, compared to mask-off condition, both male and female groups during mask-on condition showed a significant decrease in tidal volume, i.e., VT (peak), but no differences were found in the breathing reserve in percentage, i.e., BR%. For gas exchange, compared with the mask-off condition, both male and female groups during the mask-on condition showed a significant decrease in the ventilation, i.e., VE (peak), but no differences were found in VE/VCO2. For the total CPET performance, both male and female groups showed no difference in Loadmax, RPE scale, and Borg's scale.
Figure 1: Diagram for spirometry. Please click here to view a larger version of this figure.
Figure 2: The ECG electrode settings. Please click here to view a larger version of this figure.
Figure 3: Fitting of mask. (A) shows the mask-off condition. (B) shows the mask-on condition. Please click here to view a larger version of this figure.
Figure 4: Diagram for CPET settings. Please click here to view a larger version of this figure.
Parameters | Unit | Male group | Female group | P value | ||
(n=5) | (n=5) | |||||
Age | years | 21.00±1.58 | 21.20±0.45 | 0.792 | ||
Height | cm | 172.60±4.45 | 157.00±3.80 | <0.001 | ||
Weight | kg | 59.40±3.50 | 49.10±2.49 | 0.001 | ||
BMI | kg/m2 | 19.94±0.80 | 19.91±0.41 | 0.955 | ||
Spirometry | ||||||
FVC | L | 4.43±0.26 | 3.13±0.31 | <0.001 | ||
FEV1 | L | 3.70±0.24 | 2.78±0.23 | <0.001 | ||
MVV | L/min | 131.78±12.42 | 76.38±13.57 | <0.001 | ||
PEF | L/s | 8.96±1.11 | 5.95±1.41 | 0.060 | ||
Notes: Significant results are indicated in bold. FVC, forced vital capacity; FEV1, forced expiratory volume in 1 s; MVV, maximum voluntary ventilation. PEF, peak expiratory flow; L, liter; s, second. |
Table 1: Baseline characteristics and spirometry results.
Parameters | Unit | Male group | Female group | |||||
Mask-off | Mask-on | P value | Mask-off | Mask-on | P value | |||
Exercise tolerance and cardiac function | ||||||||
VO2/kg (peak) | (mL/min)/kg | 36.21±3.8 | 28.46±4.96 | 0.063 | 26.86±4.86 | 22.96±5.45 | 0.002 | |
VO2/kg (LT) | (mL/min)/kg | 22.66±2.26 | 19.74±2.23 | <0.001 | 18.48±2.89 | 14.28±2.6 | 0.026 | |
O2/HR (peak) | ratio | 12.14±0.63 | 10.02±1.7 | 0.028 | 7.96±0.87 | 6.9±1.15 | 0.004 | |
ΔVO2/ΔWR | mL/(min*W) | 8.96±0.3 | 7.52±1.4 | 0.083 | 8.66±0.51 | 7.86±1.17 | 0.217 | |
HR (rest) | bpm | 85.2±16.08 | 77.6±7.09 | 0.244 | 84±10.56 | 83.4±5.94 | 1.000 | |
HR (peak) | bpm | 177.6±10.5 | 170.6±11.33 | 0.007 | 162.6±17.67 | 162.6±21.72 | 1.000 | |
Ventilatory function | ||||||||
VT (peak) | L/min | 2.23±0.31 | 1.9±0.4 | 0.004 | 1.33±0.28 | 1.21±0.28 | 0.018 | |
BR% | % | 50.2±8.14 | 56.6±10.53 | 0.086 | 53.6±8.91 | 57.8±10.94 | 0.086 | |
Gas exchange | ||||||||
VE/VCO2 | ratio | 28.64±3.42 | 30.44±5.26 | 0.379 | 32.34±3.63 | 31.54±4.3 | 0.616 | |
VE (peak) | L | 74±13.36 | 62.6±15.35 | 0.022 | 51.8±13.35 | 43.22±11.72 | 0.042 | |
CPET performance | ||||||||
Loadmax | ||||||||
Loadmax (LT) | watts | 98.2±18.38 | 102±11.81 | 0.438 | 56.8±11.48 | 50.8±9.96 | 0.104 | |
Loadmax (RC) | watts | 155.6±22.47 | 159±24.37 | 0.223 | 87.8±18.47 | 86.2±19.6 | 0.816 | |
Loadmax (Peak) | watts | 187±28.15 | 184.8±26.81 | 0.604 | 107.6±29.25 | 105.6±30 | 0.116 | |
RPE scale | scores | 17.8±0.84 | 17±1.73 | 0.371 | 17.4±0.89 | 17.2±1.3 | 1.000 | |
Borg’s scale | scores | 4.2±0.84 | 4.8±1.64 | 0.468 | 4.8±0.45 | 4.8±0.84 | 1.000 | |
Notes: Significant results are indicated in bold. VO2/kg (peak), peak oxygen uptake per kilogram; VO2/kg (LT), anaerobic threshold per kilogram; O2/HR, oxygen pulse; ΔVO2/ΔWR, oxygen uptake related to work rate; BR%, breathing reserve in percentage; VE, ventilation; VT, tidal volume; bpm, beat per minute. RPE scalse, Rating of Perceived Exertion scale; L, liter; min, minute. |
Table 2: Results of the CPET in healthy young subjects wearing a surgical mask (mask-on) and not wearing a surgical mask (mask-off) depicted as mean ± standard deviation.
CPET provides valuable insights into the comprehensive functions of cardiovascular, ventilation, and skeletal muscle systems13. We proposed a CPET protocol on mask-on and mask-off conditions to explore the effect of the surgical mask on the cardiopulmonary function in healthy young subjects.
The design of this protocol was based on three main points. First, we recruited young healthy college students as the subjects for the study due to relatively high intensityof CPET in mask-on condition and similar physical fitness. Second, the subjects should be allocated into a male group and a female group considering the gender as the major factor in pulmonary function based on the spirometry results and previous research14. Third, we randomized the order of conditions (mask-on and mask-off) during CPET to eliminate the potential bias brought by sequencing.
Although the recruited subjects showed no significant difference on subjective sensation between two condition CPETs (mask- on and mask-off condition) based on the RPE scale and Borg’s scale, there were some objective cardiopulmonary parameters that were significantly decreased by wearing a mask, such as in VO2/kg (LT), O2/HR (peak), VT (peak), and VE (peak). Thedecrease in VO2/kg (LT) suggests that wearing a mask might reduce the ability of muscle mitochondria to use oxygen, thereby affecting exercise capacity. The decrease in O2/HR (peak) indicated decreased cardiac output. The increased VE (peak) suggested wearing a mask might affect carbon dioxide emissions. All these affected parameters indicate that the subjects with cardiopulmonary diseases might have a higher risk when they do the aerobic exercise wearing a surgical mask. Moreover, gender differences might also be a factor in the effects of masks on cardiopulmonary function. For example, just the female group showed a significant decrease in VO2/kg (peak) after wearing a mask. Due to VO2/kg (peak) as the major parameter of aerobic exercise capacity evaluation, the result indicated that the influence of wearing a mask might be more obvious for females, especially during vigorous exercise.
This study has two main limitations. First, the sample size was small, although we recruited subjects with similar physical baseline characteristics and the representative results already showed some significant differences. Second, this study only recruited healthy young subjects, although we ensured maximum consistency in this pilot study. In future research, we could recruit more subjects in different age stratification and combined with cardiopulmonary diseases to extend our protocol to the wide population. Such work would help guide mask-wearing during daily life, especially during the epidemic stage of respiratory infectious diseases.
The authors have nothing to disclose.
This study was supported by National Natural Science Foundation for Young Scientists of China (No.81902281); General Guidance Project of Guangzhou Health and Family Planning Commission (No.20191A0011091 and 20201A011108), Guangdong Provincial Department of Education (No. 2019KQNCX119) and Guangzhou Key Laboratory Fund (No.201905010004). This study also thanks Lixin Zhang, Peilin Ruan, Kaihang Ji, and Gulifeiya Tuerxun from Guangzhou Medical University for data collection.
Cardiopulmonary test system | COSMED Srl – Italy | K4b2 | Pulmonary Function Equipment |
Cycle for CPET | COSMED Srl – Italy | ergoline 100P | cycle ergometer 100 P w/BP |
Eectrocardiograph | COSMED Srl – Italy | Quark T12x | 12-Channel ECG Street Test Unit |
Mask | COSMED Srl – Italy | Small,Medium,Large | V2 Mask |
Software | COSMED Srl – Italy | PFT SUITE | PC Software |
Surgical masks |