Density measurement are reported for bilayer dispersions of a series of saturated lecithins. For chain lengths with, respectively, 14, 15, 16, 17, and 18 carbons per chain, the values for the volume changes at the main transition are 0.027, 0.031, 0.037, 0.040 and 0.045 ml/g. The main transition temperature extrapolates with increasing chain length to the melting temperature of polyethylene. Volume changes at the lower transition are an order of magnitude smaller than the main transition. Single phase thermal expansion coefficients are also reported. The combination of X-ray data and density data indicated that the volume changes are predominantly due to the hydrocarbon chains, thus enabling the volume vCH2 of the methylene groups to be computed as a function of temperature. From this and knowledge of intermolecular interactions in hydrocarbon chains, the change in the interchain van der Waals energy, delta UvdW, at the main transition is computed for the lecithins and also for the alkanes and polyethylene at the melting transition. Using the experimental enthalpies of transition and delta UvdW, the energy equation is consistently balanced for all three systems. This yields estimates of the change in the number of gauche rotamers in the lecithins at the main transition. The consistency of these calculations supports the conclusion that the most important molecular energies for the main transition in lecithin bilayers are the hydrocarbon chain interactions and the rotational isomeric energies, and the conclusion that the main phase transition is analogous to the melting transition in the alkanes from the hexagonal phase to the liquid phase, but with some modifications.

There is insufficient evidence to establish the safety or effectiveness of HFNC as a form of respiratory support in preterm infants. When used following extubation, HFNC may be associated with a higher rate of reintubation than nasal CPAP. Further adequately powered randomised controlled trials should be undertaken in preterm infants comparing HFNC with nasal CPAP and with other means of respiratory support; or of support following extubation. These trials should measure clinically important outcomes.

Objective: The aim of this study was to measure pharyngeal pressures in preterm infants receiving high-flow nasal cannulae.Study Design: A total of 18 infants were studied (median gestational age 34 weeks, weight 1.619 kg). A catheter-tip pressure transducer was introduced into the nasopharynx. Flow was sequentially increased to a maximum of 8 l min À1 and decreased to a minimum of 2 l min À1 .Result: There was a strong association between pharyngeal pressure and both flow rate and infant weight (P<0.001, r 2 ¼ 0.61), but not mouth closure. This relationship could be expressed as pharyngeal pressure (cmConclusion: High-flow nasal cannulae at flow rates of 2 to 8 l min À1 can lead to clinically significant elevations in pharyngeal pressure in preterm infants. Flow rate and weight but not mouth closure are important determinants of the pressure transmitted.

There are no egalitarians in a pandemic. The scale of the challenge for health systems and public policy means that there is an ineluctable need to prioritize the needs of the many. It is impossible to treat all citizens equally, and a failure to carefully consider the consequences of actions could lead to massive preventable loss of life. In a pandemic there is a strong ethical need to consider how to do most good overall. Utilitarianism is an influential moral theory that states that the right action is the action that is expected to produce the greatest good. It offers clear operationalizable principles. In this paper we provide a summary of how utilitarianism could inform two challenging questions that have been important in the early phase of the pandemic: (a) Triage: which patients should receive access to a ventilator if there is overwhelming demand outstripping supply? (b) Lockdown: how should countries decide when to implement stringent social restrictions, balancing preventing deaths from COVID‐19 with causing deaths and reductions in well‐being from other causes? Our aim is not to argue that utilitarianism is the only relevant ethical theory, or in favour of a purely utilitarian approach. However, clearly considering which options will do the most good overall will help societies identify and consider the necessary cost of other values. Societies may choose either to embrace or not to embrace the utilitarian course, but with a clear understanding of the values involved and the price they are willing to pay.

Purpose of the review-Decisions to withdraw or withhold potentially life-sustaining treatment are common in intensive care and precede the majority of deaths. Where families resist or oppose doctors' suggestions that it is time to stop treatment it is often unclear what should be done. This review will summarize recent literature around futility judgements in intensive care emphasising ethical and practical questions.Recent findings-There has been a shift in the language of futility. Patients' families often do not believe medical assessments that further treatment would be unsuccessful. Attempts to determine through data collection which patients have a low or zero chance of survival have been largely unsuccessful, and are hampered by varying definitions of futility. A due-process model for adjudicating futility disputes has been developed in Texas, and may provide a better solution to futility disputes than previous futility statutes.Summary-Specific criteria for unilateral withdrawal of treatment have proved hard to define or defend. However, it is ethical for doctors to decline to provide treatment that is medically inappropriate or futile. Understanding the justification for a futility judgement may be relevant to deciding the most appropriate way to resolve futility disputes.

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Predictions of poor prognosis for critically ill patients may become self-fulfilling if life-sustaining treatment or resuscitation is subsequently withheld on the basis of that prediction. This paper outlines the epistemic and normative problems raised by self-fulfilling prophecies (SFPs) in intensive care. Where predictions affect outcome, it can be extremely difficult to ascertain the mortality rate for patients if all treatment were provided. SFPs may lead to an increase in mortality for cohorts of patients predicted to have poor prognosis, they may lead doctors to feel causally responsible for the deaths of their patients, and they may compromise honest communication with patients and families about prognosis. However, I argue that the self-fulfilling prophecy is inevitable when life-sustaining treatment is withheld or withdrawn in the face of uncertainty. SFPs do not necessarily make treatment limitation decisions problematic. To minimize the effects of SFPs, it is essential to carefully collect and appraise evidence about prognosis. Doctors need to be honest with themselves and with patients and their families about uncertainty and the limits of knowledge.

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