Greenland Ice Core Record of Last Glacial Dust Sources and Atmospheric Circulation

Abrupt and large-scale climate changes have occurred repeatedly and within decades during the last glaciation. These events, where dramatic warming occurs over decades, are well represented in both Greenland ice core mineral dust and temperature records, suggesting a causal link. However, the feedbacks between atmospheric dust and climate change during these Dansgaard-Oeschger events are poorly known and the processes driving changes in atmospheric dust emission and transport remain elusive. Constraining dust provenance is key to resolving these gaps. Here, we present a multi-technique analysis of Greenland dust provenance using novel and established, source diagnostic isotopic tracers as well as results from a regional climate model including dust cycle simulations. We show that the existing dominant model for the provenance of Greenland dust as sourced from combined East Asian dust and Pacific volcanics is not supported. Rather, our clay mineralogical and Hf-Sr-Nd and D/H isotopic analyses from last glacial Greenland dust and an extensive range of Northern Hemisphere potential dust sources reveal three most likely scenarios (in order of probability): direct dust sourcing from the Taklimakan Desert in western China, direct sourcing from European glacial sources, or a mix of dust originating from Europe and North Africa. Furthermore, our regional climate modeling demonstrates the plausibility of European or mixed European/North African sources for the first time. We suggest that the origin of dust to Greenland is potentially more complex than previously recognized, demonstrating more uncertainty in our understanding dust climate feedbacks during abrupt events than previously understood.

Respiratory and peripheral muscular ultrasound characteristics in ICU COVID 19 ARDS patients

PURPOSE

Severe cases of coronavirus disease 2019 develop ARDS requiring admission to the ICU. This study aimed to investigate the ultrasound characteristics of respiratory and peripheral muscles of patients affected by COVID19 who require mechanical ventilation.

MATERIALS AND METHODS

This is a prospective observational study. We performed muscle ultrasound at the admission of ICU in 32 intubated patients with ARDS COVID19. The ultrasound was comprehensive of thickness and echogenicity of both parasternal intercostal and diaphragm muscles, and cross-sectional area and echogenicity of the rectus femoris.

RESULTS

Patients who survived showed a significantly lower echogenicity score as compared with those who did not survive for both parasternal intercostal muscles. Similarly, the diaphragmatic echogenicity was significantly different between alive or dead patients. There was a significant correlation between right parasternal intercostal or diaphragm echogenicity and the cumulative fluid balance and urine protein output. Similar results were detected for rectus femoris echogenicity.

CONCLUSIONS

The early changes detected by echogenicity ultrasound suggest a potential benefit of proactive early therapies designed to preserve respiratory and peripheral muscle architecture to reduce days on MV, although what constitutes a clinically significant change in muscle echogenicity remains unknown.

A validation study of a continuous automatic measurement of the mechanical power in ARDS patients

The mechanical power (MP) is the energy delivered into the respiratory system over time. It can be computed as a direct measurement of the inspiratory area of the airway pressure and volume loop during the respiratory cycle or calculated by "power equations". The absence of a bedside computation limited its widespread use. Recently, it has been developed an automatic monitoring system inside of a mechanical ventilator.

PURPOSE

Our aim was to investigate the repeatability and the accuracy of the measured MP at different PEEP values and tidal volume compared with the calculated MP.

MATERIAL AND METHODS

MP was measured and calculated in sedated and paralyzed ARDS patients at low and high tidal volume, at 5-10-15 cmH₂O of PEEP both in volume and pressure-controlled ventilation. The same measurements were performed twice.

RESULTS

Fifty ARDS patients were enrolled. MP was measured and calculated for a total of 300 measurements. The bias and limits of agreement were 0.38 from -1.31 to 2.0 J/min. The measured and calculated MP were similar in each ventilatory condition.

CONCLUSIONS

The mechanical power measured by a new automatic real time system implemented in a mechanical ventilator was repeatable and accurate compared with the computed one.

Lung recruitment: What has computed tomography taught us in the last decade?

Although chest X-ray remains a fundamental lung imaging technique, through the years, CT scan has significantly improved our knowledge of the pathophysiological process and currently is the reference lung imaging tool for both a visual and quantitative computer-based analysis. The application of lung CT in the early phase of ARDS has led to changes in the clinical management in up of thirty percent of the patients. Although CT requires the transportation of the patient to the radiological department and exposes the patient to high dose of radiation, given the several information that CT can offer, it should be applied at least one time, in the early phase in all ARDS patients. CT plays an irreplaceable role to describe and assess the lung recruitability and to help a more physiological setting of mechanical ventilation.

Reliability of transpulmonary pressure-time curve profile to identify tidal recruitment/hyperinflation in experimental unilateral pleural effusion

The stress index (SI) is a parameter that characterizes the shape of the airway pressure-time profile (P/t). It indicates the slope progression of the curve, reflecting both lung and chest wall properties. The presence of pleural effusion alters the mechanical properties of the respiratory system decreasing transpulmonary pressure (Ptp). We investigated whether the SI computed using Ptp tracing would provide reliable insight into tidal recruitment/overdistention during the tidal cycle in the presence of unilateral effusion. Unilateral pleural effusion was simulated in anesthetized, mechanically ventilated pigs. Respiratory system mechanics and thoracic computed tomography (CT) were studied to assess P/t curve shape and changes in global lung aeration. SI derived from airway pressure (Paw) was compared with that calculated by Ptp under the same conditions. These results were themselves compared with quantitative CT analysis as a gold standard for tidal recruitment/hyperinflation. Despite marked changes in tidal recruitment, mean values of SI computed either from Paw or Ptp were remarkably insensitive to variations of PEEP or condition. After the instillation of effusion, SI indicates a preponderant over-distension effect, not detected by CT. After the increment in PEEP level, the extent of CT-determined tidal recruitment suggest a huge recruitment effect of PEEP as reflected by lung compliance. Both SI in this case were unaffected. We showed that the ability of SI to predict tidal recruitment and overdistension was significantly reduced in a model of altered chest wall-lung relationship, even if the parameter was computed from the Ptp curve profile.

Melatonin reduces the need for sedation in ICU patients: a randomized controlled trial

BACKGROUND

Critically ill patients suffer from physiological sleep deprivation and have reduced blood melatonin levels. This study was designed to determine whether nocturnal melatonin supplementation would reduce the need for sedation in patients with critical illness.

METHODS

A single-center, double-blind randomized placebo-controlled trial was carried out from July 2007 to December 2009, in a mixed medical-surgical Intensive Care Unit of a University hospital, without any form of external funding. Of 1158 patients admitted to ICU and treated with conscious enteral sedation, 82 critically-ill with mechanical ventilation >48 hours and Simplified Acute Physiology Score II>32 points were randomized 1:1 to receive, at eight p.m. and midnight, melatonin (3+3mg) or placebo, from the third ICU day until ICU discharge. Primary outcome was total amount of enteral hydroxyzine administered.

RESULTS

Melatonin treated patients received lower amount of enteral hydroxyzine. Other neurological indicators (amount of some neuroactive drugs, pain, agitation, anxiety, sleep observed by nurses, need for restraints, need for extra sedation, nurse evaluation of sedation adequacy) seemed improved, with reduced cost for neuroactive drugs. Post-traumatic stress disorder prevalence did not differ between groups, nor did ICU or hospital mortality. Study limitations include the differences between groups before intervention, the small sample size, and the single-center observation.

CONCLUSION

Long-term enteral melatonin supplementation may result in a decreased need for sedation, with improved neurological indicators and cost reduction. Further multicenter evaluations are required to confirm these results with different sedation protocols.

Pleural effusion in ARDS

Pleural effusion is a fluid collection within the pleural space and is a common finding in mechanically ventilated patients. It is frequently related to fluid overload, hyponcotic states, heart failure, and altered pleural pressure due to atelectasis or pneumonia. Recent literature has shown that its incidence within ARDS is increasing, even if, in most of cases, at least in the early phases, it seems of limited clinical relevance. Most of the knowledge of Pleural Effusion and of its interaction with lung/chest wall mechanics derives from a small number of experimental studies and from some clinical studies, in most of the cases performed with normal lung parenchyma. In ARDS, however, Pleural Effusion seems to have a little effect "per se" on tidal mechanics and oxygenation (increasing elastance and reducing PO2), that are already profoundly affected by the lung injury itself. To sum up all the observations, we can assume that Pleural Effusion alters regional transmural pressure, restricting more the inspiration phase, and creating an opening/closure effect that can be reverted by PEEP application in recruitable lungs. This restores volume and compliance only if the abdomen is normally expansible. Drainage of Pleural Effusion is frequently performed in ICU but the benefits and risks are not well established. Lung ultrasound is an effective technique with high sensitivity and specificity for both bedside diagnosis and drainage guidance. It may help to quantify and qualify the effusion and at the same time the grade of aeration of underling parenchyma. Aim of this review is to summarize the current evidence and opinions about the interaction between Pleural Effusion and positive pressure ventilation in the presence of ARDS, its impact on gas exchange and tidal mechanics, trying to figure out the best bedside management that is not available yet. The estimation of both lung and chest wall elastance may help in the clinical decision making whether to drain or not in order to improve respiratory mechanics and oxygenation. Further research is still needed to determine the effect of drainage on clinical outcome and to evaluate its application in the weaning strategies.

Performance assessment of a glucose control protocol in septic patients with an automated intermittent plasma glucose monitoring device

BACKGROUND & AIMS

The optimal level and modality of glucose control in critically ill patients is still debated. A protocolized approach and the use of nearly-continuous technologies are recommended to manage hyperglycemia, hypoglycemia and glycemic variability. We recently proposed a pato-physiology-based glucose control protocol which takes into account patient glucose/carbohydrate intake and insulin resistance. Aim of the present investigation was to assess the performance of our protocol with an automated intermittent plasma glucose monitoring device (OptiScanner™ 5000).

METHODS

OptiScanner™ was used in 6 septic patients, providing glucose measurement every 15' from a side-port of an indwelling central venous catheter. Target level of glucose was 80-150 mg/dL. Insulin infusion and kcal with nutritional support were also recorded.

RESULTS

6 septic patients were studied for 319 h (1277 measurements); 58 [45-65] hours for each patient (measurements/patient: 231 [172-265]). Blood glucose was at target for 93 [90-98]% of study time. Mean plasma glucose was 126 ± 11 mg/dL. Only 3 hypoglycemic episodes (78, 78, 69 mg/dL) were recorded. Glucose variability was limited: plasma glucose coefficient of variation was 11.7 ± 4.0% and plasma glucose standard deviation was 14.3 ± 5.5 mg/dL.

CONCLUSIONS

The local glucose control protocol achieved satisfactory glucose control in septic patients along with a high degree of safeness. Automated intermittent plasma glucose monitoring seemed useful to assess the performance of the protocol.