Comparison of mild physiological effects of surgical masks and N95 respirators over 60 min at rest.

Dead-space-associated rebreathing of expired air and heat trapping with use of surgical masks and N95 respirators may underlie anecdotal reports of adverse symptoms associated with medical face barriers. Limited data exist directly comparing the physiological effects of masks and respirators at rest. We assessed the short-term physiological effects of both barrier types over 60 min at rest, including face microclimate temperature, end-tidal gases, and venous blood acid-base variables. We recruited 34 participants into two trials: surgical masks (n = 17) and N95 respirators (n = 17). In a seated position, participants underwent a 10-min baseline without a barrier and then wore a standardized surgical mask or dome-shaped N95 respirator for 60 min, followed by a 10-min washout. We instrumented healthy human participants with a peripheral pulse oximeter ([Formula: see text]) and a nasal cannula connected to a dual gas analyzer for measurement of the pressure of end-tidal [Formula: see text] and [Formula: see text], with an associated temperature probe for face microclimate temperature. Venous (v) blood samples were obtained at baseline and following 60-min mask/respirator wearing to assess [Formula: see text], [HCO3-]v and pHv. Compared with baseline during/following 60 min, temperature, [Formula: see text], [Formula: see text], and [HCO3-]v were mildly but significantly higher, and [Formula: see text] and [Formula: see text] were significantly lower, but [Formula: see text] was unaffected. The magnitude of effects was similar between barrier types. Temperature and [Formula: see text] returned to baseline levels within 1-2 min following removal of the barrier. These mild physiological effects may underlie reports of qualitative symptoms while wearing masks or respirators. However, the magnitudes were mild, not physiologically relevant and reversed immediately with the removal of the barrier.NEW & NOTEWORTHY Anecdotal reports suggest mild physiological effects of wearing surgical masks and/or N95 respirators, including heat trapping and rebreathing of expired air. There are limited data directly comparing the physiological effects of wearing medical barriers at rest. We found that the time course and magnitude of changes to face microclimate temperature, end-tidal gases, and venous blood gases and acid-base variables were mild in magnitude, not physiologically relevant, equivalent between barrier types, and immediately reversible on removal.

Burns from illegal cannabis oil manufacturing: a case series.

BACKGROUND: The increasing consideration of cannabis legalization in Canada and the United States has motivated physicians to assess its prospective impact on the health care system. Health care providers in the burns community are concerned about injuries sustained as a result of the illegal manufacturing of cannabis oil because it involves highly flammable reagents. METHODS: We report a retrospective case series of patients with cannabis oil burns (identified by evidence of combustion during cannabis oil manufacturing) treated from April 2012 to March 2014 at the Foothills Medical Centre in Calgary, Alberta, Canada. We compare the characteristics of these patients with those of patients admitted over the same period with any burns. RESULTS: We found that 12 (out of 161 patients) admitted over the review period sustained burns from cannabis oil manufacturing. Compared with patients in the total burn group, patients with cannabis oil burns were younger (75% and 48% were younger than 41 years in the group with cannabis oil burns and the total burn group, respectively), were more likely to be male (83% in the group with cannabis oil burns v. 74% in the total burn group) and sustained burns over a larger percentage of their total body surface area (24% v. 9%). Patients with cannabis oil burns also required extensive surgical management (skin grafting in 75% of cases) and spent a substantial amount of time (mean 32 d) in the burn unit. INTERPRETATION: Burns from illegal cannabis oil manufacturing are large, require extensive management and involve younger patients than burns in general. Given that the frequency of cannabis oil burns may increase in Canada after legalization, Canadian burn centres are encouraged to monitor and report on cases with this injury mechanism.