Discussion
sleepiness, CM, headache
HEAT
According to our partially double-blinded, randomized, cross-over study, wearing SM, CM or especially FFP2 results in subjective discomfort, particularly including difficult breathing and an uncomfortable feeling of humidity and heat underneath the mask. The feeling of discomfort increases with higher physical exertion and to a lesser extent with longer wearing time. Also, in the blinded CPET scenario, the subjects report significantly stronger impairment with FFP2 than without mask. Symptoms not directly affecting the mouth-nose region are reported rather rarely. However, headache and sleepiness occurred occasionally after 4-h workplace examination. No changes in cognitive performance are found as a result of wearing a mask.Although some authors have already reported subjective sensations of wearing a mask, most studies solely surveyed subjects’ perceived exertion using the Borg scale. In studies using additional instruments, subjects were interviewed either at restAs a particular strength of our study, we conducted a subjective assessment of mask wearing during physical exertion in a double-blinded manner (CPET). Even though this did not correspond to normal mask wearing because of the tight-fitting CPET mask, it confirmed the main outcomes of ergometry. Blinding seems to be particularly important in the case of subjective assessments as it is well known that blinding makes it difficult to bias results intentionally or unintentionally and so helps ensure the credibility of study conclusionsAnother advantage of our study is the measurement of temperature and humidity underneath the mask as well as the recording of physiological parameters