Methods
thirst
HEART
Ethical approval was obtained from the Imperial College Research Ethics Committee (20IC6445). Participants approached the study team after viewing poster advertisements at Imperial College London. After reading the participant information sheet, potential participants were given the opportunity to ask questions. Participants who fulfilled the inclusion and exclusion criteria and were happy to participate signed an informed consent form. Inclusion criteria: age 18–30 years; body mass index (BMI) 18–30 kg·mExperiments were conducted in a human performance laboratory. Participants performed an exercise protocol on two occasions: once wearing aerosol PPE (PPE group) and once wearing standard surgical attire (control group). Aerosol PPE consisted of surgical scrubs, coverall, FFP3 respirator, visor and nitrile gloves; standard surgical attire consisted of surgical scrubs, type IIR face mask and surgical cap (The exercise protocol consisted of 30-min acclimatization, 2-h walking on a treadmill (ZR11, Reebok, Boston, MA, USA), and 30-min rest. During the rest period participants consumed a 500-ml bottle of an electrolyte rehydration drink (Powerade, Coca-Cola, Atlanta, GA, USA). The treadmill speed was adjusted on the first visit during the first 5-min walking to elicit a heart rate that was 50% of the participant’s predicted maximum (maximum heart rate = 220 − age). This treadmill speed was maintained throughout the protocol and during the subsequent visit. This exercise intensity is equivalent to three metabolic equivalents and is the metabolic expenditure associated with healthcare-related activities [Core temperature was recorded with an ingestible pill telemetry system (CorTemp, HQ Inc., Palmetto, FL, USA). Participants swallowed the pill 2 h prior to arrival at the laboratory. Heart rate was recorded using an optical heart rate sensor (Polar OH1, Polar Electro, Kempele, FI). Participants rated temperature sensation (perceived body temperature), thermal pleasantness (perceived pleasantness of their thermal environment), sweat and thirst with 100-mm visual analogue scales (VASs) [The components of the Intubation of a Manikin taskETT, endotracheal tube; MAC, Mackintosh blade. Each component may be awarded 0, 1 or 2 points and thus the maximum achievable score is 28.Given the exploratory nature of this physiological study, a sample size of 16 was chosen based on previous investigations of thermoregulation and PPE, where 6–18 participants were studied [