Operational Semantics and Polymorphic Type Inference

Three languages with polymorphic type disciplines are discussed, namely the λ-calculus with Milner's polymorphic type discipline; a language with imperative features (polymorphic references); and a skeletal module language with structures, signatures and functors. In each of the two first cases we show that the type inference system is consistent with an operational dynamic semantics. On the module level, polymorphic types correspond to signatures. There is a notion of principal signature. So-called signature checking is the module level equivalent of type checking. In particular, there exists an algorithm which either fails or produces a principal signature

Co-Induction in Relational Semantics

AbstractAn application of the mathematical theory of maximum fixed points of monotonic set operators to relational semantics is presented. It is shown how an important proof method which we call co-induction, a variant of Park's (1969) principle of fixpoint induction, can be used to prove the consistency of the static and the dynamic relational semantics of a small functional programming language with recursive functions

Increased bystander intervention when volunteer responders attend out-of-hospital cardiac arrest

AIM: The primary aim was to investigate the association between alarm acceptance compared to no-acceptance by volunteer responders, bystander intervention, and survival in out-of-hospital cardiac arrest. MATERIALS AND METHODS: This retrospective observational study included all suspected out-of-hospital cardiac arrests (OHCAs) with activation of volunteer responders in the Capital Region of Denmark (1 November 2018 to 14 May 2019), the Central Denmark Region (1 November 2018 to 31 December 2020), and the Northern Denmark Region (14 February 2020 to 31 December 2020). All OHCAs unwitnessed by Emergency Medical Services (EMS) were analyzed on the basis on alarm acceptance and arrival before EMS. The primary outcomes were bystander cardio-pulmonary resuscitation (CPR), bystander defibrillation and secondary outcome was 30-day survival. A questionnaire sent to all volunteer responders was used with respect to their arrival status. RESULTS: We identified 1,877 OHCAs with volunteer responder activation eligible for inclusion and 1,725 (91.9%) of these had at least one volunteer responder accepting the alarm (accepted). Of these, 1,355 (79%) reported arrival status whereof 883 (65%) arrived before EMS. When volunteer responders accepted the alarm and arrived before EMS, we found increased proportions and adjusted odds ratio for bystander CPR {94 vs. 83%, 4.31 [95% CI (2.43–7.67)] and bystander defibrillation [13 vs. 9%, 3.16 (1.60–6.25)]} compared to cases where no volunteer responders accepted the alarm. CONCLUSION: We observed a fourfold increased odds ratio for bystander CPR and a threefold increased odds ratio for bystander defibrillation when volunteer responders accepted the alarm and arrived before EMS

Immediate psychological impact on citizen responders dispatched through a mobile application to out-of-hospital cardiac arrests

Background: Activating citizen responders may increase survival after out-of-hospital cardiac arrest (OHCA) but could induce significant psychological impact on the citizen responders. We examined psychological impact among citizen responders within the first days following resuscitation attempt. Methods and Results: A mobile phone application to activate citizen responders to perform cardiopulmonary resuscitation (CPR) was implemented in the Capital Region of Denmark. All dispatched citizen responders (September 2017 to May 2019) received a survey 90 minutes after an alarm, including self-rating of perceived psychological impact on a scale of 1–4.Of 5,395 included citizen responders, most (88.6%) completed the survey within 24 hours.The majority reported no psychological impact (68.6%), whereas 24.7%, 5.5% and 1.2% reported low, moderate, or severe impact, respectively. Severe impact was more commonly reported in the following groups: No CPR training (3.8% vs 1.2%, p = 0.02), age < 30 years (2.0% vs 0.9%, p < 0.001), female sex (1.8% vs 0.7%, p < 0.001), provided CPR (2.7% vs 1.0%, p < 0.001), and arrived prior to the emergency medical services (EMS) (2.8% vs 0.7%, p < 0.001) compared to no to moderate impact.Chi square test, Mann-Whitney U test, Fischer’s exact test and a logistic regression model were used to assess differences in psychological impact across groups. Conclusion: Very few citizen responders reported severe psychological impact. Lack of prior CPR training, younger age, female sex, performing CPR and arrival prior to the EMS were associated with greater psychological impact. Though very few citizen responders reported severe impact, the possibility of professional debriefing should be considered in citizen responder programs

Activation of Citizen Responders to Out-of-Hospital Cardiac Arrest During the COVID-19 Outbreak in Denmark 2020

BACKGROUND: Little is known about how COVID‐19 influenced engagement of citizen responders dispatched to out‐of‐hospital cardiac arrest (OHCA) by a smartphone application. The objective was to describe and analyze the Danish Citizen Responder Program and bystander interventions (both citizen responders and nondispatched bystanders) during the first COVID‐19 lockdown in 2020. METHODS AND RESULTS: All OHCAs from January 1, 2020, to June 30, 2020, with citizen responder activation in 2 regions of Denmark were included. We compared citizen responder engagement for OHCA in the nonlockdown period (January 1, 2020, to March 10, 2020, and April 21, 2020, to June 30, 2020) with the lockdown period (March 11, 2020, to April 20, 2020). Data are displayed in the order lockdown versus nonlockdown period. Bystander cardiopulmonary resuscitation rates did not differ in the 2 periods (99% versus 92%; P=0.07). Bystander defibrillation (9% versus 14%; P=0.4) or return‐of‐spontaneous circulation (23% versus 23%; P=1.0) also did not differ. A similar amount of citizen responders accepted alarms during the lockdown (6 per alarm; interquartile range, 6) compared with the nonlockdown period (5 per alarm; interquartile range, 5) (P=0.05). More citizen responders reported performing chest‐compression‐only cardiopulmonary resuscitation during lockdown compared with nonlockdown (79% versus 59%; P=0.0029), whereas fewer performed standardized cardiopulmonary resuscitation, including ventilations (19% versus 38%; P=0.0061). Finally, during lockdown, more citizen responders reported being not psychologically affected by attending an OHCA compared with nonlockdown period (68% versus 56%; P<0.0001). Likewise, fewer reported being mildly affected during lockdown (26%) compared with nonlockdown (35%) (P=0.003). CONCLUSIONS: The COVID‐19 lockdown in Denmark was not associated with decreased bystander‐initiated resuscitation in OHCAs attended by citizen responders

Contemporary levels of cardiopulmonary resuscitation training in Denmark

AIM: Many efforts have been made to train the Danish population in cardiopulmonary resuscitation (CPR) and automated external defibrillator (AED) use. We assessed CPR and AED training levels among the broad Danish population and volunteer responders. METHODS: In November 2018, an electronic cross-sectional survey was sent to (1) a representative sample of the general Danish population (by YouGov) and (2) all volunteer responders in the Capital Region of Denmark. RESULTS: A total of 2,085 people from the general population and 7,768 volunteer responders (response rate 36%) completed the survey. Comparing the general Danish population with volunteer responders, 81.0% (95% CI 79.2–82.7%) vs. 99.2% (95% CI 99.0–99.4%) p < 0.001 reported CPR training, and 54.0% (95% CI 51.8; 56.2) vs. 89.5% (95% CI 88.9–90.2) p < 0.001 reported AED training, at some point in life. In the general population, the unemployed and the self-employed had the lowest proportion of training with CPR training at 71.9% (95% CI 68.3–75.4%) and 65.4% (95% CI 53.8–75.8%) and AED training at 39.0% (95% CI 35.2–42.9%) and 34.6% (95% CI 24.2–46.2%), respectively. Applicable to both populations, the workplace was the most frequent training provider. Among 18–29-year-olds in the general population, most reported training when acquiring a driver's license. CONCLUSIONS: A large majority of the Danish population and volunteer responders reported previous CPR/AED training. Mandatory training when acquiring a driver's license and training through the workplace seems to disseminate CPR/AED training effectively. However, new strategies reaching the unemployed and self-employed are warranted to ensure equal access