Development and assessment of the performance of a shared ventilatory system that uses clinically available components to individualize tidal volumes.

OBJECTIVES: To develop and assess a system for shared ventilation using clinically available components to individualize tidal volumes. DESIGN: Evaluation and in vitro validation study SETTING: Ventilator shortage during the SARS-CoV-2 pandemic. PARTICIPANTS: The team consisted of physicians, bioengineers, computer programmers, and medical technology professionals. METHODS: Using clinically available components, a system of ventilation consisting of two ventilatory limbs was assembled and connected to a ventilator. Monitors for each limb were developed using open-source software. Firstly, the effect of altering ventilator settings on tidal volumes delivered to each limb was determined. Secondly, the impact of altering the compliance and resistance of one limb on the tidal volumes delivered to both limbs was analysed. Experiments were repeated three times to determine system variability. RESULTS: The system permitted accurate and reproducible titration of tidal volumes to each limb over a range of ventilator settings and simulated lung conditions. Alteration of ventilator inspiratory pressures, of respiratory rates, and I:E ratio resulted in very similar tidal volumes delivered to each limb. Alteration of compliance and resistance in one limb resulted in reproducible alterations in tidal volume to that test lung, with little change to tidal volumes in the other lung. All tidal volumes delivered were reproducible. CONCLUSIONS: We demonstrate the reliability of a shared ventilation system assembled using commonly available clinical components that allows titration of individual tidal volumes. This system may be useful as a strategy of last resort for Covid-19, or other mass casualty situations, where the need for ventilators exceeds supply.

Modeling Mechanical Ventilation In Silico-Potential and Pitfalls.

Computer simulation offers a fresh approach to traditional medical research that is particularly well suited to investigating issues related to mechanical ventilation. Patients receiving mechanical ventilation are routinely monitored in great detail, providing extensive high-quality data-streams for model design and configuration. Models based on such data can incorporate very complex system dynamics that can be validated against patient responses for use as investigational surrogates. Crucially, simulation offers the potential to "look inside" the patient, allowing unimpeded access to all variables of interest. In contrast to trials on both animal models and human patients, in silico models are completely configurable and reproducible; for example, different ventilator settings can be applied to an identical virtual patient, or the same settings applied to different patients, to understand their mode of action and quantitatively compare their effectiveness. Here, we review progress on the mathematical modeling and computer simulation of human anatomy, physiology, and pathophysiology in the context of mechanical ventilation, with an emphasis on the clinical applications of this approach in various disease states. We present new results highlighting the link between model complexity and predictive capability, using data on the responses of individual patients with acute respiratory distress syndrome to changes in multiple ventilator settings. The current limitations and potential of in silico modeling are discussed from a clinical perspective, and future challenges and research directions highlighted.

The prevalence of pre-operative anaemia and an examination of its effect on transfusion practice between sexes: A multicentre retrospective study.

Pre-operative anaemia affects one third of patients presenting for surgery and is associated with increased peri-operative morbidity and mortality. Most studies on this subject make a distinction in acceptable haemoglobin level between sexes. We analysed data for patients undergoing major elective surgery, with pre-operative anaemia defined as haemoglobin <13 g/dL. Data was collected for 1074 patients, of whom 411 (38.3%) had pre-operative anaemia. The odds of red cell transfusion were significantly higher in patients with pre-operative anaemia, OR = 4.35 [95%CI OR: 3.0- 6.2]. Additional binary logistic regression results identified haemoglobin level, male gender and increasing age as independent predictors for red cell transfusion. The length of post-operative stay was also significantly higher in anaemic patients, those with lower haemoglobin, males and older patients. Women were twice as likely to have a haemoglobin < 13 g/dl as men. Women were also 3.55 times more likely not to be transfused despite being anaemic. This suggests differences in clinician's attitudes to transfusion limits in women, despite Blaudszun et al. 2018 showing that women with borderline anaemia (Hb 12-12.9 g/dL) are: more likely to be transfused; to be transfused more units of red cells; and to have longer lengths of hospital stay than non- anaemic women. A change in attitude to acceptable haemoglobin in women is needed. Increased clinician awareness of the associated morbidity of even a mild reduction in haemoglobin in women is required to result in more pro-active anaemia management pre-operatively and less allogenic red cell transfusion, shorter lengths of hospital stay and overall decreased morbidity.

COMPARISON OF THREE ANALYZERS FOR ASSESSING COMPLETE BLOOD COUNTS IN NONHUMAN PRIMATES.

Diagnostic hematology can prove challenging to the exotic animal practitioner presented with a nonhuman primate patient. Few point-of-care automated cell counters are calibrated for primate samples. Twenty-one samples from 17 nonhuman primates presented to an exotic animal practice were analyzed. Samples were run on both canine and feline settings on each of two veterinary point-of-care analyzers: one that assays by impedance technology, and one that assays by laser flow cytometry. Samples were also sent to a reference laboratory to be assayed on an analyzer that performs simultaneous impedance and laser measurements of blood cells and has been calibrated for use in nonhuman primates. Fourteen analytes were assessed for each sample on each machine. Manual hematocrits and total white blood cell counts were also performed on 16 of the samples. Statistical analysis indicated some variance between individual parameters, but overall correlation was acceptable.

Mycobacterium marinum infection in a blue-fronted Amazon parrot (Amazona aestiva).

A blue-fronted Amazon parrot (Amazona aestiva) was presented with a granuloma involving the proximal rhinotheca and extending into the rostral sinuses. Mycobacterium marinum was diagnosed based on results of biopsy and culture. Treatment was initiated with clarithromycin, rifampin, and ethambutol, but the bird died 4 months after the onset of antimicrobial therapy. Additional granulomas were found in the left lung and liver on postmortem examination. Mycobacterial isolation on postmortem samples was unsuccessful. This is the first report of Mycobacterium marinum in a bird.

A computational cardiopulmonary physiology simulator accurately predicts individual patient responses to changes in mechanical ventilator settings.

We present new results validating the capability of a high-fidelity computational simulator to accurately predict the responses of individual patients with acute respiratory distress syndrome to changes in mechanical ventilator settings. 26 pairs of data-points comprising arterial blood gasses collected before and after changes in inspiratory pressure, PEEP, FiO2, and I:E ratio from six mechanically ventilated patients were used for this study. Parallelized global optimization algorithms running on a high-performance computing cluster were used to match the simulator to each initial data point. Mean absolute percentage errors between the simulator predicted values of PaO2 and PaCO2 and the patient data after changing ventilator parameters were 10.3% and 12.6%, respectively. Decreasing the complexity of the simulator by reducing the number of independent alveolar compartments reduced the accuracy of its predictions. Clinical Relevance- These results provide further evidence that our computational simulator can accurately reproduce patient responses to mechanical ventilation, highlighting its usefulness as a clinical research tool.

Pediatric dysautonomia: Much-maligned, often overmedicated, but not as complex as you think.

Dysautonomia is an increasingly recognized yet still poorly understood disease within the field of pediatrics. Symptoms, including dizziness, headaches, fatigue, joint pain, anxiety, and intolerance of heat or cold, are often significant and difficult to sort, especially in terms of their relation to each other. This often leads to referral to multiple subspecialists, who then proceed to treat seemingly familiar symptoms in kind. In the authors' experience, this leads to more frustration on the part of the patients and their physicians when symptom improvement does not follow (or can even worsen). On the other hand, by understanding the pathophysiology, treatment success is possible by directing therapies toward the root causes and just as importantly, enlisting the patient in a daily treatment plan. In the text that follows, we hope to convey these viewpoints by highlighting an involved case, discussing the pathophysiology, outlining the usual evaluation, and finally describing our approach to treatment.

Absence of thyroid transcription factor-1 expression is associated with poor survival in patients with advanced pulmonary adenocarcinoma treated with pemetrexed-based chemotherapy.

INTRODUCTION: Adenocarcinoma is the commonest histologic subtype of lung cancer and is often identified by immunohistochemical staining for thyroid transcription factor-1 (TTF-1). However, up to 20% of lung adenocarcinomas do not express TTF-1, and there is uncertainty regarding the significance of this. We aimed to evaluate the prognostic effect of TTF-1 expression status on survival in patients treated with pemetrexed-based chemotherapy for advanced adenocarcinoma of the lung. METHODS: This retrospective study included patients treated with pemetrexed-based chemotherapy for stage IIIB/IV lung adenocarcinoma, who had known TTF-1 expression status. Clinical and demographic data were obtained from medical records. Overall survival (OS) was estimated using the Kaplan-Meier method, and differences in survival between groups assessed using the Cox proportional hazards model. RESULTS: Forty-four patients were identified with documented TTF-1 expression: 35 with TTF-1-positive and 9 with TTF-1-negative disease. Patients in the TTF-1-negative group had poorer performance scores than those in the TTF-1-positive group (ECOG 2: 67 vs 20%, p = 0.008), and received less chemotherapy (median cycles 2 vs 4, p = 0.009), and were fewer in treatment with doublet regimens (22 vs 69%, p = 0.013). OS was significantly shorter in the TTF-1-negative group than in the TTF-1-positive group (2.4 vs 11.5 months, HR 8.38, p < 0.0001). CONCLUSIONS: In this group of patients treated with pemetrexed-based chemotherapy for advanced pulmonary adenocarcinoma, absence of TTF-1 expression was associated with an aggressive tumor phenotype, poorer performance status, and poor survival. This subgroup of patients should be recognized as having a distinct clinical course, with limited benefit from standard chemotherapy.

Ambulatory Zoo Practice.

Due to myriad species and their variety of needs, ambulatory zoologic practice can carry many challenges. The practitioner must be appropriately prepared, with the necessary equipment, medications, and supplies, which should either accompany the veterinarian or be available at the site where the work is performed. It is imperative that the veterinarian has proper knowledge of the care and feeding of these animals and knows and understands the legalities of owning and working with them. The ambulatory zoo veterinarian must be able to address the medical and surgical needs of these animals in a field or other nonconventional setting.

Shortened Lung Clearance Index is a repeatable and sensitive test in children and adults with cystic fibrosis.

BACKGROUND: Lung clearance index (LCI) derived from sulfur hexafluoride (SF6) multiple breath washout (MBW) is a sensitive measure of lung disease in people with cystic fibrosis (CF). However, it can be time-consuming, limiting its use clinically. AIM: To compare the repeatability, sensitivity and test duration of LCI derived from washout to 1/30th (LCI1/30), 1/20th (LCI1/20) and 1/10th (LCI1/10) to 'standard' LCI derived from washout to 1/40th initial concentration (LCI1/40). METHODS: Triplicate MBW test results from 30 clinically stable people with CF and 30 healthy controls were analysed retrospectively. MBW tests were performed using 0.2% SF6 and a modified Innocor device. All LCI end points were calculated using SimpleWashout software. Repeatability was assessed using coefficient of variation (CV%). The proportion of people with CF with and without abnormal LCI and forced expiratory volume in 1 s (FEV1) % predicted was compared. Receiver operating characteristic (ROC) curve statistics were calculated. Test duration of all LCI end points was compared using paired t tests. RESULTS: In people with CF, LCI1/40 CV% (p=0.16), LCI1/30 CV%, (p=0.53), LCI1/20 CV% (p=0.14) and LCI1/10 CV% (p=0.25) was not significantly different to controls. The sensitivity of LCI1/40, LCI1/30 and LCI1/20 to the presence of CF was equal (67%). The sensitivity of LCI1/10 and FEV1% predicted was lower (53% and 47% respectively). Area under the ROC curve (95% CI) for LCI1/40, LCI1/30, LCI1/20, LCI1/10 and FEV1% predicted was 0.89 (0.80 to 0.97), 0.87 (0.77 to 0.96), 0.87 (0.78 to 0.96), 0.83 (0.72 to 0.94) and 0.73 (0.60 to 0.86), respectively. Test duration of LCI1/30, LCI1/20 and LCI1/10 was significantly shorter compared with the test duration of LCI1/40 in people with CF (p<0.0001) equating to a 5%, 9% and 15% time saving, respectively. CONCLUSIONS: In this study, LCI1/20 was a repeatable and sensitive measure with equal diagnostic performance to LCI1/40. LCI1/20 was shorter, potentially offering a more feasible research and clinical measure.

Noncoronary sinus of Valsalva rupture into the right atrium with a coexisting perimembranous ventricular septal defect.

Ruptured sinus of Valsalva is very uncommon, and is < 1% of all congenital defects. The incidence ranges from 0.1%-3.5%. There is a male to female predominance of 4:1, with the highest incidence in the Asian population. Higher incidence is also seen in patients with Marfan's syndrome and Ehlers Danlos syndrome. There is a higher association of ruptured sinus of Valsalva with ventricular septal defect (VSD), aortic stenosis, and bicuspid valve defect. While most patients with VSD often have rupture of their right coronary sinus of Valsalva into the right ventricle due to poor structural integrity, we present a rare case of a patient with VSD who had rupture of his noncoronary sinus of Valsalva into the right atrium.

Increased systemic Th17 cytokines are associated with diastolic dysfunction in children and adolescents with diabetic ketoacidosis.

Diastolic dysfunction suggestive of diabetic cardiomyopathy is established in children with T1DM, but its pathogenesis is not well understood. We studied the relationships of systemic inflammatory cytokines/chemokines and cardiac function in 17 children with T1DM during and after correction of diabetic ketoacidosis (DKA). Twenty seven of the 39 measured cytokines/chemokines were elevated at 6-12 hours into treatment of DKA compared to values after DKA resolution. Eight patients displayed at least one parameter of diastolic abnormality (DA) during acute DKA. Significant associations were present between nine of the cytokine/chemokine levels and the DA over time. Interestingly, four of these nine interactive cytokines (GM-CSF, G-CSF, IL-12p40, IL-17) are associated with a Th17 mediated cell response. Both the DA and CCL7 and IL-12p40, had independent associations with African American patients. Thus, we report occurrence of a systemic inflammatory response and the presence of cardiac diastolic dysfunction in a subset of young T1DM patients during acute DKA.