Early experience with critically ill patients with COVID-19 in Montreal.

PURPOSE: Montreal has been the epicentre of the coronavirus disease (COVID-19) pandemic in Canada. Given the regional disparities in incidence and mortality in the general population, we aimed to describe local characteristics, treatments, and outcomes of critically ill COVID-19 patients in Montreal. METHODS: A single-centre retrospective cohort of consecutive adult patients admitted to the intensive care unit (ICU) of Hôpital du Sacré-Coeur de Montréal with confirmed COVID-19 were included. RESULTS: Between 20 March and 13 May 2020, 75 patients were admitted, with a median [interquartile range (IQR)] age of 62 [53-72] yr and high rates of obesity (47%), hypertension (67%), and diabetes (37%). Healthcare-related infections were responsible for 35% of cases. The median [IQR] day 1 sequential organ failure assessment score was 6 [3-7]. Invasive mechanical ventilation (IMV) was used in 57% of patients for a median [IQR] of 11 [5-22] days. Patients receiving IMV were characterized by a moderately decreased median [IQR] partial pressure of oxygen:fraction of inspired oxygen (day 1 PaO2:FiO2 = 177 [138-276]; day 10 = 173 [147-227]) and compliance (day 1 = 48 [38-58] mL/cmH2O; day 10 = 34 [28-42] mL/cmH2O) and very elevated estimated dead space fraction (day 1 = 0.60 [0.53-0.67]; day 10 = 0.72 [0.69-0.79]). Overall hospital mortality was 25%, and 21% in the IMV patients. Mortality was 82% in patients ≥ 80 yr old. CONCLUSIONS: Characteristics and outcomes of critically ill patients with COVID-19 in Montreal were similar to those reported in the existing literature. We found an increased physiologic dead space, supporting the hypothesis that pulmonary vascular injury may be central to COVID-19-induced lung damage.

RéSUMé: OBJECTIF: Montréal a été l'épicentre de la pandémie du coronavirus (COVID-19) au Canada. Étant donné les disparités régionales dans l'incidence et la mortalité dans la population générale, nous avons tenté de décrire les caractéristiques locales, les traitements et le devenir des patients atteints de la COVID-19 en état critique à Montréal. MéTHODE: Notre étude de cohorte rétrospective monocentrique a inclus tous les patients adultes admis consécutivement à l'unité de soins intensifs de l'Hôpital du Sacré-Cœur de Montréal avec un diagnostic confirmé de COVID-19. RéSULTATS: Soixante-quinze patients ont été admis entre le 20 mars et le 13 mai 2020. Ceux-ci avaient un âge médian [écart interquartile (ÉIQ)] de 62 [53­72] ans et présentaient une incidence élevée d'obésité (47 %), d'hypertension (67 %) et de diabète (37 %). Les transmissions associées aux soins de santé étaient responsables de 35 % des cas. Au jour 1, le score SOFA (Sequential Organ Failure Assessment ­ évaluation séquentielle de défaillance des organes) médian [ÉIQ] était de 6 [3­7]. La ventilation mécanique invasive (VMI) a été utilisée chez 57 % des patients, pour une durée médiane [ÉIQ] de 11 [5­22] jours. Les patients ayant reçu une VMI étaient caractérisés par une médiane [ÉIQ] modérément réduite de la pression partielle de la fraction d'oxygène inspiré (jour 1 PaO2:FiO2 = 177 [138­276]; jour 10 = 173 [147­227]), de la compliance (jour 1 = 48 [38­58] mL/cmH2O; jour 10 = 34 [28­42] mL/cmH2O), ainsi que par une fraction d'espace mort estimé très élevée (jour 1 = 0,60 [0,53-0,67]; jour 10 = 0,72 [0,69-0,79]). La mortalité hospitalière était de 25 % globalement, et de 21 % chez les patients avec VMI. La mortalité a atteint 82 % chez les patients agés de ≥ 80 ans. CONCLUSION: Les caractéristiques et le devenir des patients en état critique atteints de la COVID-19 à Montréal étaient semblables à ceux rapportés dans la littérature existante. Nous avons observé un espace mort physiologique augmenté, ce qui appuie l'hypothèse que des lésions vasculaires pulmonaires seraient primordiales dans les lésions pulmonaires induites par la COVID-19.

Deep peat warming increases surface methane and carbon dioxide emissions in a black spruce-dominated ombrotrophic bog.

Boreal peatlands contain approximately 500 Pg carbon (C) in the soil, emit globally significant quantities of methane (CH4 ), and are highly sensitive to climate change. Warming associated with global climate change is likely to increase the rate of the temperature-sensitive processes that decompose stored organic carbon and release carbon dioxide (CO2 ) and CH4 . Variation in the temperature sensitivity of CO2 and CH4 production and increased peat aerobicity due to enhanced growing-season evapotranspiration may alter the nature of peatland trace gas emission. As CH4 is a powerful greenhouse gas with 34 times the warming potential of CO2 , it is critical to understand how factors associated with global change will influence surface CO2 and CH4 fluxes. Here, we leverage the Spruce and Peatland Responses Under Changing Environments (SPRUCE) climate change manipulation experiment to understand the impact of a 0-9°C gradient in deep belowground warming ("Deep Peat Heat", DPH) on peat surface CO2 and CH4 fluxes. We find that DPH treatments increased both CO2 and CH4 emission. Methane production was more sensitive to warming than CO2 production, decreasing the C-CO2 :C-CH4 of the respired carbon. Methane production is dominated by hydrogenotrophic methanogenesis but deep peat warming increased the δ13 C of CH4 suggesting an increasing contribution of acetoclastic methanogenesis to total CH4 production with warming. Although the total quantity of C emitted from the SPRUCE Bog as CH4 is <2%, CH4 represents >50% of seasonal C emissions in the highest-warming treatments when adjusted for CO2 equivalents on a 100-year timescale. These results suggest that warming in boreal regions may increase CH4 emissions from peatlands and result in a positive feedback to ongoing warming.