Influence of source parameters on the longitudinal phase-space distribution of a pulsed cryogenic beam of barium fluoride molecules

Recently, we have demonstrated a method to record the longitudinal phase-space distribution of a pulsed cryogenic buffer gas cooled beam of barium fluoride molecules with high resolution. In this paper, we use this method to determine the influence of various source parameters. Besides the expected dependence on temperature and pressure, the forward velocity of the molecules is strongly correlated with the time they exit the cell, revealing the dynamics of the gas inside the cell. Three observations are particularly noteworthy: (1) The velocity of the barium fluoride molecules increases rapidly as a function of time, reaches a maximum 50-200 µs after the ablation pulse and then decreases exponentially. We attribute this to the buffer gas being heated up by the plume of hot atoms released from the target by the ablation pulse and subsequently being cooled down via conduction to the cell walls. (2) The time constant associated with the exponentially decreasing temperature increases when the source is used for a longer period of time, which we attribute to the formation of a layer of isolating dust on the walls of the cell. By thoroughly cleaning the cell, the time constant is reset to its initial value. (3) The velocity of the molecules at the trailing end of the molecular pulse depends on the length of the cell. For short cells, the velocity is significantly higher than expected from the sudden freeze model. We attribute this to the target remaining warm over the duration of the molecular pulse giving rise to a temperature gradient within the cell. Our observations will help to optimize the source parameters for producing the most intense molecular beam at the target velocity.</p

Putting ICU triage guidelines into practice: A simulation study using observations and interviews

Background The COVID-19 pandemic has prompted many countries to formulate guidelines on how to deal with a worst-case scenario in which the number of patients needing intensive care unit (ICU) care exceeds the number of available beds. This study aims to explore the experiences of triage teams when triaging fictitious patients with the Dutch triage guidelines. It provides an overview of the factors that influence decision-making when performing ICU triage with triage guidelines. Methods Eight triage teams from four hospitals were given files of fictitious patients needing intensive care and instructed to triage these patients. Sessions were observed and audio-recorded. Four focus group interviews with triage team members were held to reflect on the sessions and the Dutch guidelines. The results were analyzed by inductive content analysis. Results The Dutch triage guidelines were the main basis for making triage decisions. However, some teams also allowed their own considerations (outside of the guidelines) to play a role when making triage decisions, for example to help avoid using non-medical criteria such as prioritization based on age group. Group processes also played a role in decision-making: triage choices can be influenced by the triagists’ opinion on the guidelines and the carefulness with which they are applied. Intensivists, being most experienced in prognostication of critical illness, often had the most decisive role during triage sessions. Conclusions Using the Dutch triage guidelines is feasible, but there were some inconsistencies in prioritization between teams that may be undesirable. ICU triage guideline writers should consider which aspects of their criteria might, when applied in practice, lead to inconsistencies or ethically questionable prioritization of patients. Practical training of triage team members in applying the guidelines, including explanation of the rationale underlying the triage criteria, might improve the willingness and ability of triage teams to follow the guidelines closely

Putting ICU triage guidelines into practice: A simulation study using observations and interviews.

BackgroundThe COVID-19 pandemic has prompted many countries to formulate guidelines on how to deal with a worst-case scenario in which the number of patients needing intensive care unit (ICU) care exceeds the number of available beds. This study aims to explore the experiences of triage teams when triaging fictitious patients with the Dutch triage guidelines. It provides an overview of the factors that influence decision-making when performing ICU triage with triage guidelines.MethodsEight triage teams from four hospitals were given files of fictitious patients needing intensive care and instructed to triage these patients. Sessions were observed and audio-recorded. Four focus group interviews with triage team members were held to reflect on the sessions and the Dutch guidelines. The results were analyzed by inductive content analysis.ResultsThe Dutch triage guidelines were the main basis for making triage decisions. However, some teams also allowed their own considerations (outside of the guidelines) to play a role when making triage decisions, for example to help avoid using non-medical criteria such as prioritization based on age group. Group processes also played a role in decision-making: triage choices can be influenced by the triagists' opinion on the guidelines and the carefulness with which they are applied. Intensivists, being most experienced in prognostication of critical illness, often had the most decisive role during triage sessions.ConclusionsUsing the Dutch triage guidelines is feasible, but there were some inconsistencies in prioritization between teams that may be undesirable. ICU triage guideline writers should consider which aspects of their criteria might, when applied in practice, lead to inconsistencies or ethically questionable prioritization of patients. Practical training of triage team members in applying the guidelines, including explanation of the rationale underlying the triage criteria, might improve the willingness and ability of triage teams to follow the guidelines closely