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SummaryManual facemask ventilation, a core component of elective and emergency airway management, is classified as an aerosol generating procedure. This designation is based on a single epidemiological study suggesting an association between facemask ventilation and transmission from the SARS 2003 outbreak. There is no direct evidence to indicate whether facemask ventilation is a high-risk procedure for aerosol generation. We conducted aerosol monitoring during routine facemask ventilation, and facemask ventilation with an intentionally generated leak, in anaesthetised patients with neuromuscular blockade. Recordings were made in ultraclean theatres and compared against the aerosol generated by the patient’s own tidal breathing and coughs. Respiratory aerosol from tidal breathing was reliably detected above the very low background particle concentrations (191 (77-486 [3.8-1313]) versus 2.1 (0.7-4.6 [0-12.9] particles.l-1 median(IQR)[range], n=11, p=0.002). The average aerosol concentration detected during facemask ventilation both without a leak (3.0 particles.l-1 (0 – 9 [0-43])) and with an intentional leak (11 particles.l-1 (7.0 – 26 [1-62])) was 64-fold and 17-fold lower than that of tidal breathing (p=0.001 and p=0.002 respectively). The peak particle concentration during facemask ventilation both without a leak (60 particles.l-1 (0 – 60 [0-120])) and with a leak (120 particles.l-1 (60 – 180 [60-480]) were respectively 20-fold and 10-fold lower than a cough (1260 particles (800 – 3242 [100-3682]), p=0.002 and p=0.001 respectively). This study demonstrates that facemask ventilation, even performed with an intentional leak, does not generate high levels of bioaerosol. On the basis of this evidence, facemask ventilation should not be considered an aerosol generating procedure.

ObjectiveTo determine if oesophago-gastro-duodenoscopy (OGD) generates increased levels of aerosol in conscious patients and identify the source events.DesignA prospective, environmental aerosol monitoring study, undertaken in an ultraclean environment, on patients undergoing OGD. Sampling was performed 20 cm away from the patient’s mouth using an optical particle sizer. Aerosol levels during OGD were compared with tidal breathing and voluntary coughs within subject.ResultsPatients undergoing bariatric surgical assessment were recruited (mean body mass index 44 and mean age 40 years, n=15). A low background particle concentration in theatres (3 L−1) enabled detection of aerosol generation by tidal breathing (mean particle concentration 118 L−1). Aerosol recording during OGD showed an average particle number concentration of 595 L−1with a wide range (3–4320 L−1). Bioaerosol-generating events, namely, coughing or burping, were common. Coughing was evoked in 60% of the endoscopies, with a greater peak concentration and a greater total number of sampled particles than the patient’s reference voluntary coughs (11 710 vs 2320 L−1and 780 vs 191 particles, n=9 and p=0.008). Endoscopies with coughs generated a higher level of aerosol than tidal breathing, whereas those without coughs were not different to the background. Burps also generated increased aerosol concentration, similar to those recorded during voluntary coughs. The insertion and removal of the endoscope were not aerosol generating unless a cough was triggered.ConclusionCoughing evoked during OGD is the main source of the increased aerosol levels, and therefore, OGD should be regarded as a procedure with high risk of producing respiratory aerosols. OGD should be conducted with airborne personal protective equipment and appropriate precautions in those patients who are at risk of having COVID-19 or other respiratory pathogens.

Pulmonary function tests are fundamental to the diagnosis and monitoring of respiratory diseases. There is uncertainty around whether potentially infectious aerosols are produced during testing and there are limited data on mitigation strategies to reduce risk to staff. Healthy volunteers and patients with lung disease underwent standardised spirometry, peak flow and FENO assessments. Aerosol number concentration was sampled using an aerodynamic particle sizer and an optical particle sizer. Measured aerosol concentrations were compared with breathing, speaking and voluntary coughing. Mitigation strategies included a standard viral filter and a full-face mask normally used for exercise testing (to mitigate induced coughing). 147 measures were collected from 33 healthy volunteers and 10 patients with lung disease. The aerosol number concentration was highest in coughs (1.45–1.61 particles/cm3), followed by unfiltered peak flow (0.37–0.76 particles/cm3). Addition of a viral filter to peak flow reduced aerosol emission by a factor of 10 without affecting the results. On average, coughs produced 22 times more aerosols than standard spirometry (with filter) in patients and 56 times more aerosols in healthy volunteers. FENO measurement produced negligible aerosols. Cardiopulmonary exercise test (CPET) masks reduced aerosol emission when breathing, speaking and coughing significantly. Lung function testing produces less aerosols than voluntary coughing. CPET masks may be used to reduce aerosol emission from induced coughing. Standard viral filters are sufficiently effective to allow guidelines to remove lung function testing from the list of aerosol-generating procedures.

Electromagnetic (EM) guided enteral tube placement may reduce lung misplacement to almost zero in expert centres, but more than 60 undetected misplacements had occurred by 2016 resulting in major morbidity or death. Aim: Determine the accuracy of manufacturer guidance in trace interpretation against what is referred to as the ‘GI flexure system’. Methods: The authors prospectively observed the accuracy of the ‘GI flexure system’ of trace interpretation against manufacturer guidance in primary nasointestinal (NI) tube placements. Findings: Contrary to manufacturer guidance, 33% of traces deviated >5 cm from the sagittal midline and 26.5% were oesophageal when entering the lower left quadrant, incorrectly indicating lung and gastric placement, respectively. Conversely, the GI flexure system identified ≥99.4% of GI traces when they reached the gastric body flexure; 100% at the superior duodenal flexure. All lung misplacements were identified by the absence of GI flexures. Conclusion: Current manufacturer guidance should be updated to the GI flexure system of interpretation.

Background: Blind (unguided) feeding tube placement results in 0.5% of patients suffering major complications mainly due to lung misplacement detected prior to feeding. Electromagnet-guided (Cortrak) tube placement could pre-empt such complications but undetected misplacements still occur due to incorrect trace interpretation. By identifying gastrointestinal (GI) flexures from the trace, ‘the GI flexure system’, it has been proposed that tube position can be interpreted. Aims: To audit agreement between standards of interpreting tube position: the Cortrak ‘GI flexure’ system versus X-ray. Methods: In 185 primary nasointestinal tube placements tube position determined by Cortrak trace interpretation (GI flexure) was retrospectively compared with radiological position in a blinded study. Findings: Radiological and Cortrak interpretation agreed in 92.2–98.3% of placements at different GI flexures. Discrepancy mainly occurred because some radiological images were unclear or did not cover all anatomical points. Conclusion: The GI flexure method of Cortrak interpretation appears safe but would necessitate prospective radiological investigation to definitively test equivalence.

Standardized mortality ratios (SMRs), calculated using the Acute Physiology, Age, Chronic Health Evaluation II (APACHE II) and Intensive Care National Audit and Research Centre H-2018 (ICNARCH-2018) risk prediction models, are widely used in UK intensive care units (ICUs) to measure and compare the quality of critical care delivery. Both models incorporate an assumption of Glasgow Coma Score (GCS) if an actual GCS without sedation is not recordable in the first 24 hours after ICU admission. This study assesses the validity of the APACHE II and ICNARCH-2018 models to predict mortality in ICU patients with traumatic brain injury (TBI) or aneurysmal subarachnoid hemorrhage (aSAH) in whom GCS is related to outcomes.In a retrospective analysis, the SMR calculated by the APACHE II and ICNARCH-2018 models for all UK ICU admissions in a 1-year period was compared with calculated SMRs in TBI/aSAH patients and at 3 GCS groups. Data for patients admitted to a single tertiary neurocritical care unit were similarly analyzed.Both models predicted mortality well for the overall TBI/aSAH population; SMR (95% confidence interval) was 1.00 (0.96-1.04) and 0.99 (0.95-1.03) for the APACHE II and ICNARCH-2018 models, respectively. When analyzed by GCS grouping, both models underpredicted mortality in TBI/aSAH patients with GCS ≤8 (SMR, 1.1 [1.05-1.15]) and "unrecordable" GCS (SMR, 1.88 [1.77-1.99]). Similar findings were identified in the local data analysis.The APACHE II and ICNARCH-2018 models predicted mortality well for the overall TBI/aSAH ICU population but underpredicted mortality when GCS was ≤8 or "unrecordable." This raises questions about the accuracy of these risk prediction models in TBI/aSAH patients and their use to evaluate treatments and compare outcomes between centers.

Respiratory particles produced by breathing, coughing, and speaking or generated during medical procedures serve as important routes for disease transmission. Characterising the number of particles generated as well as their size distribution is fundamental for guiding policy on infection control. However, sampling such particles carries inherent challenges. Respiratory particles are polydisperse in size, temporally and spatially variable, and emitted in very low concentrations, usually lower than the pre-existing aerosol concentration in indoor environments. In addition, they are typically emitted in a highly dynamic, warm and humid jet, leading to further rapid processes, such as dispersion and evaporation. Here, we discuss important considerations for sampling respiratory aerosol, focusing on sampling particles < 20 µm in diameter. Instruments capable of counting single-particles within this size range are commercially available. We provide recommendations for experimental protocols and demonstrate the limitations behind such approaches. We highlight the importance of a measurement space with as low a background aerosol concentration as possible, and of sampling for as long as possible to enable accurate quantitation of the size distribution of an aerosol plume. This is particularly important for the larger particles (> 5µm diameter) that are so low in concentration that they may require hours of sampling time to be accurately quantified. We explore the relationship between the flow rates of the exhalation and the sampling instrument and the consequent quantification of particle flux. We also discuss the transport and evaporation dynamics of liquid particles within respiratory jets, and their impacts on conducting aerosol sampling studies.

IntroductionLung function tests are fundamental diagnostic and monitoring tools for patients with respiratory symptoms. There is significant uncertainty around whether potentially infectious aerosol is produced during different lung function testing modalities; and limited data on possible mitigation strategies to reduce risk to staff and limit fallow time.MethodsHealthy volunteers were recruited in an ultraclean, laminar flow theatre and had standardised spirometry as per ERS/ATS guidance, as well as peak flow measurement and FENO assessment of airway inflammation. Aerosol emission was sampled minimum once each second using both an Aerodynamic Particle Sizer (APS) and Optical Particle Sizer (OPS), and compared to breathing, speaking and coughing. Mitigation strategies such as a peak flow viral filter and a CPET facemask (to mitigate induced coughing) were tested.Results33 healthy volunteers were recruited. Aerosol emission was highest in cough (1.61 particles/cm3/sample), followed by unfiltered peak flow (0.76 particles/cm3/sample). Filtered spirometry produced lower peak aerosol emission (0.11 particles/ cm3/sample) than that of a voluntary cough, and addition of a viral filter to the mouthpiece reduced peak flow aerosol emission to similar levels. The filter made little difference to recorded FEV peak flow values. Peak aerosol FENO measurement produced negligible aerosol. Reusable CPET masks with filter reduced aerosol emission when breathing, speaking, and coughing significantly.ConclusionsCompared to voluntary coughing, all lung function testing produced fewer aerosol particles. Filtered spirometry produces lower peak aerosol emission than peak voluntary coughing, and should not be deemed an aerosol generating procedure. The use of viral filters reduces aerosol emission in peak flow by > 10 times, and has little impact on recorded peak flow values. CPET masks are a useful option to reduce aerosol emission from induced coughing while performing spirometry.

BackgroundRisk of aerosolisation of SARS-CoV-2 directly informs organisation of acute healthcare and PPE guidance. Continuous positive airways pressure (CPAP) and high-flow nasal oxygen (HFNO) are widely used modes of oxygen delivery and respiratory support for patients with severe COVID-19, with both considered as high risk aerosol generating procedures. However, there are limited high quality experimental data characterising aerosolisation during oxygen delivery and respiratory support.MethodsHealthy volunteers were recruited to breathe, speak, and cough in ultra-clean, laminar flow theatres followed by using oxygen and respiratory support systems. Aerosol emission was measured using two discrete methodologies, simultaneously. Hospitalised patients with COVID-19 were also recruited and had aerosol emissions measured during breathing, speaking, and coughing.FindingsIn healthy volunteers (n = 25 subjects; 531 measures), CPAP (with exhalation port filter) produced less aerosols than breathing, speaking and coughing (even with large >50L/m facemask leaks). HFNO did emit aerosols, but the majority of these particles were generated from the HFNO machine, not the patient. HFNO-generated particles were small (InterpretationIn healthy volunteers, CPAP is associated with less aerosol emission than breathing, speaking or coughing. Aerosol emission from the respiratory tract does not appear to be increased by HFNO. Although direct comparisons are complex, cough appears to generate significant aerosols in a size range compatible with airborne transmission of SARS-CoV-2. As a consequence, the risk of SARS-CoV-2 aerosolisation is likely to be high in all areas where patients with Covid-19 are coughing. Guidance on personal protective equipment policy should reflect these updated risks.FundingNIHR-UKRI Rapid COVID call (COV003), Wellcome Trust GW4-CAT Doctoral Training Scheme (FH), MRC CARP Fellowship(JD, MR/T005114/1). Natural Environment Research Council grant (BB, NE/P018459/1)Research in contextEvidence before this studyPubMed was searched from inception until 10/1/21 using the terms ‘aerosol’, and variations of ‘non-invasive positive pressure ventilation’ and ‘high-flow nasal oxygen therapy’. Studies were included if they measured aerosol generated from volunteers or patients receiving non-invasive positive pressure ventilation (NIV) or high flow nasal oxygen therapy (HFNO), or provided experimental evidence on a simulated human setting. One study was identified (Gaeckle et al, 2020) which measured aerosol emission with one methodology (APS) but was limited by high background concentration of aerosol and a low number of participants (n = 10).Added value of this studyThis study used multiple methodologies to measure aerosol emission from the respiratory tract before and during CPAP and high-flow nasal oxygen, in an ultra-clean, laminar flow theatre with near-zero background aerosol and recruited patients with COVID-19 to ensure similar aerosol distributions. We conclude that there is negligible aerosol generation with CPAP, that aerosol emission from HFNO is from the machine and not the patient, coughing emits aerosols consistent with airborne transmission of SARS CoV2 and that healthy volunteers are a reasonable proxy for COVID-19 patients.Implications of all the available evidenceCPAP and HFNO should not be considered high risk aerosol generating procedures, based on our study and that of Gaeckle et al. Recorded aerosol emission from HFNO stems from the machine. Cough remains a significant aerosol risk. PPE guidance should be updated to ensure medical staff are protected with appropriate PPE in situations when patients with suspected or proven COVID-19 are likely to cough.

A key controversy in the COVID-19 pandemic has been over staff safety in health and social care settings. Anaesthetists and intensivists were anticipated to be at the highest risk of work-related infection due to involvement in airway management and management of critical illness and therefore wear the highest levels of personal protective equipment (PPE) in the hospital. However, the data clearly show that those working in anaesthesia and critical care settings are at lower risk of infection, harm and death from COVID-19 than colleagues working on the wards. The observed safety of anaesthetists and intensivists and increased risk to those in other patient-facing roles has implications for transmission-based infection control precautions. The precautionary principle supports extending training in and use of airborne precaution PPE to all staff working in patient-facing roles who have close contact with coughing patients. This will both reduce their risk of contracting COVID-19, maintain services and reduce nosocomial transmission to vulnerable patients. The emergence of a new variant of the SARS-CoV-2 virus with significantly higher transmissibility creates urgency to addressing this matter.

The potential aerosolised transmission of severe acute respiratory syndrome coronavirus-2 is of global concern. Airborne precaution personal protective equipment and preventative measures are universally mandated for medical procedures deemed to be aerosol generating. The implementation of these measures is having a huge impact on healthcare provision. There is currently a lack of quantitative evidence on the number and size of airborne particles produced during aerosol-generating procedures to inform risk assessments. To address this evidence gap, we conducted real-time, high-resolution environmental monitoring in ultraclean ventilation operating theatres during tracheal intubation and extubation sequences. Continuous sampling with an optical particle sizer allowed characterisation of aerosol generation within the zone between the patient and anaesthetist. Aerosol monitoring showed a very low background particle count (0.4 particles.l−1) allowing resolution of transient increases in airborne particles associated with airway management. As a positive reference control, we quantitated the aerosol produced in the same setting by a volitional cough (average concentration, 732 (418) particles.l−1, n = 38). Tracheal intubation including facemask ventilation produced very low quantities of aerosolised particles (average concentration, 1.4 (1.4) particles.l−1, n = 14, p < 0.0001 vs. cough). Tracheal extubation, particularly when the patient coughed, produced a detectable aerosol (21 (18) l−1, n = 10) which was 15-fold greater than intubation (p = 0.0004) but 35-fold less than a volitional cough (p < 0.0001). The study does not support the designation of elective tracheal intubation as an aerosol-generating procedure. Extubation generates more detectable aerosol than intubation but falls below the current criterion for designation as a high-risk aerosol-generating procedure. These novel findings from real-time aerosol detection in a routine healthcare setting provide a quantitative methodology for risk assessment that can be extended to other airway management techniques and clinical settings. They also indicate the need for reappraisal of what constitutes an aerosol-generating procedure and the associated precautions for routine anaesthetic airway management.

Background: Transmission of SARS-CoV-2 by bioaerosols is of increasing concern. The enhanced levels of personal protective equipment (PPE) and preventative measures to attenuate viral transmission during aerosol generating procedures (AGPs) are having a huge impact on healthcare provision. There is no quantitative evidence on the number and size of airborne particles produced during AGPs to inform risk assessments. Methods: Real-time, high-resolution environmental monitoring was conducted in ultraclean ventilation operating theatres. Continuous sampling with an optical particle sizer allowed characterisation of aerosol generation within the airway management zone during endotracheal intubation and extubation for urgent orthopaedic trauma or neuro-surgery. Findings: Aerosol monitoring showed a very low background particle count allowing resolution of the transient airborne particle plume produced by reference volitional coughs (maximum concentration, 1,690±140 particles.L‑1,n=38). By comparison, endotracheal intubation including mask ventilation produced negligible quantities of aerosolised particles (maximum concentration, 80±10 L‑1,n=14, P

Many guidelines consider supraglottic airway use to be an aerosol-generating procedure. This status requires increased levels of personal protective equipment, fallow time between cases and results in reduced operating theatre efficiency. Aerosol generation has never been quantitated during supraglottic airway use. To address this evidence gap, we conducted real-time aerosol monitoring (0.3-10-µm diameter) in ultraclean operating theatres during supraglottic airway insertion and removal. This showed very low background particle concentrations (median (IQR [range]) 1.6 (0-3.1 [0-4.0]) particles.l-1 ) against which the patient's tidal breathing produced a higher concentration of aerosol (4.0 (1.3-11.0 [0-44]) particles.l-1 , p = 0.048). The average aerosol concentration detected during supraglottic airway insertion (1.3 (1.0-4.2 [0-6.2]) particles.l-1 , n = 11), and removal (2.1 (0-17.5 [0-26.2]) particles.l-1 , n = 12) was no different to tidal breathing (p = 0.31 and p = 0.84, respectively). Comparison of supraglottic airway insertion and removal with a volitional cough (104 (66-169 [33-326]), n = 27), demonstrated that supraglottic airway insertion/removal sequences produced

Summary Background & aims Delayed gastric emptying (DGE) commonly limits the use of enteral nutrition (EN) and may increase ventilator-associated pneumonia. Nasointestinal feeding has not been tested against dual prokinetic treatment (Metoclopramide and Erythromycin) in DGE refractory to metoclopramide. This trial tests the feasibility of recruiting this ‘treatment-failed’ population and the proof of concept that nasointestinal (NI) feeding can increase the amount of feed tolerated (% goal) when compared to nasogastric (NG) feeding plus metoclopramide and erythromycin treatment. Methods Eligible patients were those who were mechanically ventilated and over 20 years old, with delayed gastric emptying (DGE), defined as a gastric residual volume ≥250 ml or vomiting, and who failed to respond to first-line prokinetic treatment of 3 doses of 10 mg IV metoclopramide over 24 h. When assent was obtained, patients were randomised to receive immediate nasointestinal tube placement and feeding or nasogastric feeding plus metoclopramide and erythromycin (prokinetic) treatment. Results Of 208 patients with DGE, 77 were eligible, 2 refused assent, 25 had contraindications to intervention, almost exclusively prokinetic treatment, and it was feasible to recruit 50. Compared to patients receiving prokinetics (n = 25) those randomised to nasointestinal feeding (n = 25) tolerated more of their feed goal over 5 days (87–95% vs 50–89%) and had a greater area under the curve (median [IQR] 432 [253–464]% vs 350 [213–381]%, p = 0.026) demonstrating proof of concept. However, nasointestinally fed patients also had a larger gastric loss (not feed) associated with the NI route but not with the fluid volume or energy delivered. Conclusions This is first study showing that in DGE refractory to metoclopramide NI feeding can increase the feed goal tolerated when compared to dual prokinetic treatment. Future studies should investigate the effect on clinical outcomes. EU Clinical trials register EudraCT number: 2012-001374-29.

The prescription of intravenous fluids is common in hospitalized patients and is increasingly recognized as a potential source of harm if administered inappropriately. The recently published NICE guideline seeks to provide a simple and consistent approach to assessing, prescribing and re-evaluating fluid status in sick patients. There has been a long-running debate regarding the optimal fluid to prescribe which has shifted in recent years to consider not only which type of fluid to prescribe but also how much and when. This article summarizes the physiology of fluid and electrolyte homeostasis and the latest evidence for each of the common fluids available. We aim to highlight specific circumstances where the choice of fluid may vary from normal practice.

Background Low tidal volume ventilation improves outcomes in acute respiratory distress syndrome. Calculation of this volume requires knowledge of a patient’s gender, and height, which may not be available in emergency admissions, and the subsequent application of a nomogram. The objective of this study was to test the accuracy of a calibrated measuring tape that reads in mL of tidal volume when the ulna is measured. Methods The measuring tape was used to obtain an estimate of a subject’s tidal volume from their ulna length, and standing height was then measured (reference method). Result A total of 100 healthy volunteers were included. Mean tidal volume was 450 mL for males and 372 mL for females when calculated from the height. Comparing tidal volumes from the tape with those from the reference method, Bland Altman analysis showed a bias of −10 mL (limits of agreement (2SD) −74 mL to 54 mL) for males and a bias of −36 mL (limits of agreement (2SD) −88 mL to 16 mL) for females. Predicted mean tidal volumes were 5.7 mL/kg (95% CI: 5.1–6.3 mL/kg) for males and 5.8 mL/kg (95% CI: 5.3–6.2 mL/kg) for females. Conclusions Usage of a calibrated measuring tape produced accurate estimates of tidal volumes required for lung protective ventilation in healthy volunteers.

Recent evidence suggests official statistics greatly underestimate the occurrence of complications from misplaced nasogastric (NG) tubes, even when detected. Current methods of confirming tube position do not provide adequate protection from misplacement. In addition, some tubes are inadequately radio-opaque. We prospectively audited placement of Cortrak polyurethane tubes (PUTs) to determine: accuracy of the electromagnetic (EM) trace in confirming tube position, radio-opacity of PUTs compared with previously placed polyvinylchloride (PVC) Ryles tubes and whether 12 French PUTs can be used to aspirate gastric residual volumes (GRVs). A total of 127 PUTs were placed in 113 patients. EM traces accurately confirmed tube position compared with X-ray (100% agreement). A ‘gastric’ EM trace has been defined for future use by other operators. PUTs were adequately radio-opaque with good agreement between interpreters (>98%) whereas PVC Ryles tubes were insufficiently radio-opaque (57–73%), invisible in 23% of cases and with poor agreement between interpreters leaving risk of error. The alternative of using pH confirmation was not possible in 44%. In these cases subsequent X-ray incurred a 2-hour delay to feed and medicines. In addition, neither post-placement pH testing nor X-ray warn of lung placement and potential trauma, whereas the EM trace warned of lung placement prior to damage in 7% of placements. 12 French, single-port PUTs appear adequate to aspirate large GRVs. EM tracing may be considered a standalone method of confirming NG tube position. Corflo (Cortrak) PUTs are adequately radio-opaque. Use of PVC Ryles and other inadequately radio-opaque tubes should stop.

Delayed gastric emptying (DGE) commonly limits the use of enteral nutrition (EN) and may increase ventilator-associated pneumonia. Nasointestinal feeding has not been tested against dual prokinetic treatment (Metoclopramide and Erythromycin) in DGE refractory to metoclopramide. This trial tests the feasibility of recruiting this 'treatment-failed' population and the proof of concept that nasointestinal (NI) feeding can increase the amount of feed tolerated (% goal) when compared to nasogastric (NG) feeding plus metoclopramide and erythromycin treatment.Eligible patients were those who were mechanically ventilated and over 20 years old, with delayed gastric emptying (DGE), defined as a gastric residual volume ≥250 ml or vomiting, and who failed to respond to first-line prokinetic treatment of 3 doses of 10 mg IV metoclopramide over 24 h. When assent was obtained, patients were randomised to receive immediate nasointestinal tube placement and feeding or nasogastric feeding plus metoclopramide and erythromycin (prokinetic) treatment.Of 208 patients with DGE, 77 were eligible, 2 refused assent, 25 had contraindications to intervention, almost exclusively prokinetic treatment, and it was feasible to recruit 50. Compared to patients receiving prokinetics (n = 25) those randomised to nasointestinal feeding (n = 25) tolerated more of their feed goal over 5 days (87-95% vs 50-89%) and had a greater area under the curve (median [IQR] 432 [253-464]% vs 350 [213-381]%, p = 0.026) demonstrating proof of concept. However, nasointestinally fed patients also had a larger gastric loss (not feed) associated with the NI route but not with the fluid volume or energy delivered.This is first study showing that in DGE refractory to metoclopramide NI feeding can increase the feed goal tolerated when compared to dual prokinetic treatment. Future studies should investigate the effect on clinical outcomes.EudraCT number: 2012-001374-29.

Perioperative fluid therapy remains a controversial topic despite much research. Here, we review the different types of fluids, what to use in different circumstances and some of the controversies associated with fluid use. Crystalloids are fluids with small water-soluble molecules that can easily cross semi-permeable membranes. Saline-based fluids stay mainly within the extracellular compartment. Glucose solutions provide free water that diffuses across all the fluid compartments of the body. Colloids are fluids with larger, more insoluble molecules that do not readily cross membranes. Gelatins, dextrans and hydroxyethyl starches are effective intravascular volume expanders but are associated with numerous complications including anaphylaxis, renal failure and coagulation changes. Balanced solutions have low chloride content to avoid producing hyperchloreamic acidosis with extensive fluid use. Maintenance requirements can be met by providing water, sodium and potassium. Replacement for third space and insensible losses should use a ‘balanced' crystalloid. The type of fluid used for hypovolaemia resuscitation can be crystalloid or colloid, with neither proven to be better than the other. Goal-directed therapy has shown that giving surgical patients the optimal amount of fluid that they require, as guided by cardiac-output monitoring, is associated with better outcomes.

Introductioncontinuous positive airway pressure (CPAP) and high-flow nasal oxygen (HFNO) provide enhanced oxygen delivery and respiratory support for patients with severe COVID-19. CPAP and HFNO are currently designated as aerosol-generating procedures despite limited high-quality experimental data. We aimed to characterise aerosol emission from HFNO and CPAP and compare with breathing, speaking and coughing.Materials and methodsHealthy volunteers were recruited to breathe, speak and cough in ultra-clean, laminar flow theatres followed by using CPAP and HFNO. Aerosol emission was measured using two discrete methodologies, simultaneously. Hospitalised patients with COVID-19 had cough recorded using the same methodology on the infectious diseases ward.ResultsIn healthy volunteers (n=25 subjects; 531 measures), CPAP (with exhalation port filter) produced less aerosol than breathing, speaking and coughing (even with large >50 L/min face mask leaks). Coughing was associated with the highest aerosol emissions of any recorded activity. HFNO was associated with aerosol emission, however, this was from the machine. Generated particles were small (ConclusionsIn healthy volunteers, standard non-humidified CPAP is associated with less aerosol emission than breathing, speaking or coughing. Aerosol emission from the respiratory tract does not appear to be increased by HFNO. Although direct comparisons are complex, cough appears to be the main aerosol-generating risk out of all measured activities.