Effects of Surgical Masks on Cardiopulmonary Function in Healthy Subjects

Summary

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.

Abstract

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.

Introduction

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 life^2,3,4.

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.

Protocol

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

1. Include subjects between 18 and 26 years old: who can pass the PAR-Q test⁶; are physically healthy; without professional sports training experience; and able to understand the experiment and voluntarily cooperate with the whole test process.
2. Exclude subjects: with cardiovascular diseases and respiratory diseases; with lower limb motor dysfunction caused by other diseases; who cannot cooperate with the experiment; and smokers⁷.
3. Obtain written informed consent from each subject before their participation.
4. Inform the subject that strenuous activities are prohibited 48 h before the test and during the test, and that food and beverages (except water) are not allowed 2 h before the test.
5. Collect the subjects' basic information (name, gender, date of birth, height, weight).
6. Randomly allocate the subjects into two groups by SPSS generated digit table. Group 1 first received CPET in the mask-on condition followed by 48 h of washout, and then received CPET in the mask-off condition. Group 2 first received CPET in the mask-off condition followed by 48 h of washout, then received CPET in the mask-on condition.

2. Laboratory settings and equipment preparation

1. Set the laboratory temperature to 25 °C and equip with first aid equipment.
2. Calibrate the cardiopulmonary function analyzer to ensure the accuracy of the CPET test, including flow sensor calibration, indoor air calibration, gas analysis calibration, and respiratory rate calibration.
   ​NOTE: For gas analysis calibration, use 5% CO₂ and 16% O₂ concentrations and N₂ for balance.

3. Spirometry

1. Ask the subject to sit upright without leaning on the back of the chair, with their feet on the ground, but without tilting their feet. Ask them to keep their head at a natural level or slightly tilted upwards, but not to bend their head down or bend over.
2. Forced Vital Capacity (FVC) test: Ask the subject to breathe calmly for 5 s, inhale strongly, and then exhale strongly for 6 s. Finally, inhale back and keep breathing calmly. Perform the whole procedure under the guidance of a doctor or a formally trained exercise physiologist.
3. Maximum Voluntary Ventilation (MVV) test: Ask the subject to breathe calmly four or five times. Then repeat the breath continuously for 12 s or 15 s at the maximum breathing amplitude and the fastest breathing speed after the baseline with expiratory volume is stable (Figure 1).
   ​NOTE: If the subject does not perform well during static lung function test, the subject will be asked to perform the tests one more time after a 3-min rest. If the subject fails the test twice, exclude the subject.

4. Cardiopulmonary exercise test (CPET)

1. Subject preparation for CPET
   1. Briefly introduce the process to the subject.
   2. Scrape the body hair at the position of the electrocardiograph (ECG) electrodes (V1 to V6), and then use 75% alcohol to remove extra dander and grease.
      ​NOTE: V1 is the 4th intercostal space to the right of the sternum. V2 is the 4th intercostal space, to the left of the sternum, V3 is between V2 and V4 electrodes, V4 is the 5th intercostal space on the midclavicular line, V5 is the 5th intercostal space, on the anterior axillary line, and V6 is the 5th intercostal space on the left midaxillary line. Place limb electrodes for the arms in the sub-clavicular areas, and place limb electrodes for the legs placed on the trunk at the level of the bottom rib. The electrode placement should be lateral to avoid excessive movement artifact during cycling.
   3. Place the ECG electrodes and attach them to the 12-lead ECG wires.
   4. Fix the ECG machine to the chest using a strap (Figure 2).
   5. Choose a mask that fits the size of the subject's face and attach it firmly to the face to ensure that there is no gap between the mask and the face (Figure 3).
      NOTE: The tester could use their hand to press gently on the vest and lightly exhale to ensure that there is no gap.
   6. Fix the flow meter on the vent and then fix the K4 device onto the vest (Figure 4).
   7. Sit on the seat and adjust the height of the handlebars to a comfortable position for the subject.
   8. Grab the handlebar with both hands and step on the pedals with bilateral feet to ensure that the right knee joint bends with flexion at 30°.
   9. Place a blood pressure cuff on the upper-right arm for dynamic blood pressure recording. Place a finger pulse oxygen on the left index finger for dynamic recording of blood oxygen.
   10. Calculate the subject's exercise resistance/increased incremental per min (W) parameters and set the progressive resistance plan for the exercise phase⁸.
       NOTE: Exercise resistance (male) = [(height - age) * 20 - (150 + 6 * weight)] / 100
       Exercise resistance (female) = [(height - age) * 14 - (150 + 6 * weight)] / 100
2. CPET executing phase
   ​NOTE: Ask the subject not to speak during the whole procedure to prevent extra exhalation and inhalation during speaking, which might affect the accuracy of the cardiopulmonary data. Ask the subject to please raise their hand to indicate if there is any questions or discomfort that results in the test interruption.
   1. Click on the Start button to activate cycle ergometer by tester.
   2. Keep a static sitting posture for 2 min (Rest stage).
   3. Start cycling for 2 min (Warm-up stage: resistance to 0 W, speed to 60 rpm).
   4. Continue cycling until the time point when the subject could not maintain or show the ending signs (Ramp exercise stage: Incremental resistance, X watt resistance per min, 60 rpm).
      ​NOTE: X watt resistance per min is based on the formulas in step 4.1.10.
   5. Ask the subject to cycle for 3 min (cool-down stage: resistance to 0 W, speed to 40 rpm).
   6. Keep the static sitting posture for 3 min for observation of vital signs (observation stage).
      ​NOTE: Criteria for discontinuing are as follows: Subjects are encouraged to exercise to their maximum endurance or until the practitioners end the exercise due to symptoms such as ischemic ECG changes, complex ectopy, second or third degree heart block, fall in systolic pressure >20 mm Hg from the highest value during the test, hypertension (>250 mm Hg systolic; >120 mm Hg diastolic), severe desaturation (oxyhemoglobin saturation (SpO₂) ≤ 80%), symptoms and signs of severe hypoxemia (sudden pallor, loss of coordination, mental confusion, dizziness, faintness), signs of respiratory failure, or exhaustion (Borg ≥ 17-18 points) failed maintaining the cycling speed (lower than 40 rpm). The test will be terminated immediately if the subjects show extreme verbal or physical fatigue⁷, which is lower than 40 rpm.
   7. Remove data acquisition equipment, face mask, vest, and ECG electrodes.

5. CPET post testing

1. Use the Rating of Perceived Exertion (RPE) scale to measure physical activity intensity levels that are apparently related to the heart rate (HR) during exercise^9,10.
2. Use the Borg's scale (6-20 scale) to evaluate exertion of resistance training ¹¹. A score of 6 represents resting activity with no effort and a score of 20 represents exhaustive exercise.

6. Statistical analysis

1. Analyze the data using SPSS software (version 25) and the methodology referenced in the previous study¹².
2. Present the parametric data as mean and standard deviation (SD) if normally distributed or median if not.
3. Allocate the subjects into male or female groups for statistical analysis, respectively.
4. Use the paired t-test to compare the differences of CPET parameters between subjects in the mask-on condition and mask-off condition. Statistical significance is P < 0.05.

Results

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, th...

Discussion

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 ...

Materials

Name	Company	Catalog Number	Comments
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