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Increased ventilator use during the COVID-19 pandemic resurrected persistent questions regarding mechanical ventilation including the difference between physiological and artificial breathing induced by ventilators (i.e., positive- versus negative-pressure ventilation, PPV vs NPV). To address this controversy, we compare murine specimens subjected to PPV and NPV in ex vivo quasi-static loading and quantify pulmonary mechanics via measures of quasi-static and dynamic compliances, transpulmonary pressure, and energetics when varying inflation frequency and volume. Each investigated mechanical parameter yields instance(s) of significant variability between ventilation modes. Most notably, inflation compliance, percent relaxation, and peak pressure are found to be consistently dependent on the ventilation mode. Maximum inflation volume and frequency note varied dependencies contingent on the ventilation mode. Contradictory to limited previous clinical investigations of oxygenation and end-inspiratory measures, the mechanics-focused comprehensive findings presented here indicate lung properties are dependent on loading mode, and importantly, these dependencies differ between smaller versus larger mammalian species despite identical custom-designed PPV/NPV ventilator usage. Results indicate that past contradictory findings regarding ventilation mode comparisons in the field may be linked to the chosen animal model. Understanding the differing fundamental mechanics between PPV and NPV may provide insights for improving ventilation strategies and design to prevent associated lung injuries. [ABSTRACT FROM AUTHOR]

Negative-pressure pulmonary edema (NPPE) is a rare but life-threatening postoperative complication that occurs due to the acute obstruction of the upper airway. In our case report, we present a 25-year-old female patient who underwent elective mammoplasty under general anesthesia and developed NPPE 4 hours after extubation. The patient had a preoperative mallampati score of 3. After routine anesthesia induction, the patient was intubated with an endotracheal tube with a guide wire. Aspiration wasn't observed during extubation. The patient was followed in the post-anesthesia care unit (PACU) for 30 minutes with a saturation of 95% and was subsequently transferred to the service. Four hours after the operation, the patient was re-examined due to dyspnea and shortness of breath. Due to oxygen saturation of 88% and pO2of 56mmHg despite mask ventilation, the patient was admitted to the intensive care unit (ICU). A computed tomography (CT) scan revealed extensive diffuse ground-glass opacities and consolidations in both lungs. She did not respond to mask ventilation and was given non-invasive ventilation with continuous positive airway pressure (CPAP). Forced diuresis was induced with furosemide. Tachypnea resolved within 2 hours after CPAP was initiated, the patient did not require oxygen support and COVID-19 polymerase chain reaction (PCR) testing was negative. Subsequently, the patient was discharged to the clinical ward on postoperative day 1. When considering NPPE, early diagnosis and respiratory support are associated with reduced mortality and rapid recovery. Patients who develop laryngospasm during extubation must be closely monitored, and in the case of pulmonary edema, NPPE should be considered in the differential diagnosis. [ABSTRACT FROM AUTHOR]

Objective: To establish recommendations related to negative pressure therapy with instillation according to effectiveness, safety, efficiency, consensus guidelines and stability data of instillation solutions. Method: A literature search was conducted to compare the available evidence regarding effectiveness, safety and efficiency of negative pressure therapy with instillation, as well as the existence of consensus guidelines for use. The articles were classified according to the “Scale of evidence classification for therapeutic studies” of the American Society of Plastic and Reconstructive Surgery. Results: A total of 13 studies were included, of which five were comparative cohort studies (level II and III of evidence), and the rest corresponded to case series (level IV of evidence). Two consensus guidelines were selected with recommendations regarding the type of wound, instillation solution, solution retention time, vacuum pressure and appropriate vacuum time. According to literature and available evidence, recommendations were proposed and established on negative pressure therapy with instillation in our hospital, including stability data of the proposed solutions. Conclusions: This paper provides preliminary guidelines on the application of negative pressure therapy with instillation until new evidence supports or modifies these recommendations.

Surgical site infection (SSI) and wound breakdown after emergency laparotomy are common. They incur significant patient morbidity and health care costs. Negative-pressure dressings (NPDs) applied over closed incisions may minimize wound complications. However, its utility in the emergency setting is unknown. Here, we examined whether prophylactic NPD reduces wound complications after emergency laparotomies. This is a retrospective review of consecutive emergency laparotomies undertaken at a university hospital from January 2018 to October 2019. Outcomes included the rate of SSI, wound breakdown, hospital-outreach service utilization, wound-related readmissions, and length of stay. Propensity score matched analysis was used to assess bias. A total of 227 emergency laparotomies were reviewed, 70 received NPD and 157 had conventional dressings (controls). SSI was identified in 33 (21.0%) patients from the control group and six (8.6%) from the NPD group (odds ratio 0.35, 95% confidence interval: 0.15-0.85, P = 0.022). Wound breakdown was observed in 21 (13.4%) patients from the control group and three (4.3%) from the NPD group (odds ratio 0.29, 95% confidence interval: 0.09-0.91, P = 0.040). The prophylactic benefit of NPD was most evident in clean-contaminated, contaminated, and dirty wounds. The NPD group had comparatively shorter postoperative stay, less outreach service utilization, and lower rates of wound-related readmissions. Multivariate analysis demonstrated that increasing age, body weight >75 kg, and wound contamination are independent predictors of wound complications, whereas NPD prevented SSI and wound breakdown. Prophylactic NPD significantly reduced wound complications after emergency laparotomy. This was associated with a substantial health resource saving. This study provides a strong rationale for randomized trials in this area. [ABSTRACT FROM AUTHOR]

Background: The coronavirus disease (COVID‐19) pandemic has raised concern of transmission of infectious organisms through aerosols formation in endonasal and transoral surgery. Methods: Retrospective review. We introduce the negative‐pressure otolaryngology viral isolation drape (NOVID) system to reduce the risk of aerosol. NOVID consists of a plastic drape suspended above the patient's head and surgical field with a smoke evacuator suction placed inside the chamber. Results: Four patients underwent endonasal (4) and endo‐oral surgery (1). Fluorescein was applied to the surgical field. Black light examination of fluorescein‐treated operative fields revealed minimal contamination distant to the surgical field. In two prolonged cases with high‐speed drilling, droplets were identified under the barrier and on the tip of the smoke evacuator. Instruments and cottonoids appeared to be a greater contributor to field contamination. Conclusions: Negative‐pressure aspiration of air under a chamber barrier, which appears to successfully keep aerosol and droplet contamination to a minimum. [ABSTRACT FROM AUTHOR]

Negative-pressure hydrocephalus is a rare condition with the development of symptomatic hydrocephalus despite subnormal intracranial pressure (ICP). The etiology remains unclear. Some authors proposed that the differential pressure between the ventricular space and the subarachnoid space over cerebral convexity leads to the development of ventriculomegaly, namely as the transmantle pressure theory. A 49-year-old patient with a left Sylvian fissure arachnoid cyst underwent several surgeries including cystoperitoneal shunts and fenestrations of the cyst. The patient developed a cerebrospinal fluid fistula from the cranial wound was complicated by bacterial meningitis. Consequently, the shunt was removed, and external cyst drainage was placed. After 9 days, the patient developed acute hydrocephalus requiring external ventricular drainage (EVD). Two days later, after overdrainage of the external cyst drain, the patient suffered neurologic deterioration. The ICP measured by the EVD was –4 cm H 2 O, and a computed tomography scan demonstrated progression of the hydrocephalus. The external cyst drainage was shut off and the EVD level was adjusted to produce between 5 and 10 mL/hour of cerebrospinal fluid under a subatmospheric pressure set at –5 cm H 2 O, and gradually raised in increments of 1 cm every 3 days until a positive ICP occurred. Once clinical and radiographic stability was accomplished, a programmable ventriculoperitoneal shunt was inserted set to 30 mm H 2 O. A marked clinical and radiologic improvement was observed in the follow-up. This negative-pressure hydrocephalus case report supports the main role of the transmantle pressure theory. The subatmospheric EVD method and a low-pressure valve resulted in excellent clinical and radiographic outcomes. [ABSTRACT FROM AUTHOR]

This paper proposes a design and implementation of thermal and negative-pressure wind tunnel testing system for middle-to-high temperature and low Mach number ( Ma < 0. 3 ). Draft fan is used to build negative pressure environment, air heater is used to heat airflow, finned-tube heat exchanger is used to cool two-phase flow, dust collector is used to recycle erosion particle and PC is used for experimental data acquisition and test system monitoring via the serial port server DIGATTOT. System framework and the inhalating approach of dust are introduced. The distance from spout to erosion surface is computed, and data acquisition and control unit are introduced. PC and DIGATTOT series serial server are used for telnet communication, the communication of server with all the sensors and control elements is completed by RS485 serial interface. PC interface is completed by using industrial configuration software MCGS. After testing, the maximum temperature of the system reaches 750°C, gas-solid flow particulate concentrations and erosion speed are all adjustable. The angle of attack can be arbitrarily adjusted with the range of 0-90. By the temperature, velocity and heat stability tests, the experiment station has reached the design target. [ABSTRACT FROM AUTHOR]

In order to solve the millet sowing labour, improve the accuracy of sowing and seeding efficiency, reduce the leakage sowing rate, this paper presents a negative pressure precision millet seed-metering device with adjustable disc gap. Each set of seeding device is composed of two discs, can adjust the gap to meet the requirements of different seed amount. The millet seedmetering according to the requirements of sowing and achieve the required seeding rate, row spacing and plant spacing, saving a large amount of seed, increase the utilization rate of the seeds, ensure production, fully meet the demand for Chinese farmers. The structure and the arrangement of the seed-metering device was optimized, and can be adjusted according to the actual requirements. Also takes into account the economic savings, take discharge device and a furrow opener together, reduce the complexity, and the seeding effect is not affected. So as to achieve the purpose of the design of the seeding machine to achieve the desired. [ABSTRACT FROM AUTHOR]

Objective: Negative-pressure hydrocephalus (NegPH) is a rare clinical entity characterised by enlarged ventricles and symptoms consistent with increased intracranial pressure (ICP) in the setting of negative ICP. Little has been published regarding appropriate treatment and outcomes of negative-pressure hydrocephalus patients, and no data have been published demonstrating successful therapy producing acceptable long-term outcomes. Here we present 8 cases successfully treated by titrated external ventricular drainage (TEVD), including drainage at negative (subatmospheric) pressure, and subsequent low-pressure ventriculoperitoneal shunting. Methods: A retrospective audit of all cases of negative-pressure hydrocephalus occurring at a university teaching hospital between 2006 and 2012 was undertaken. The clinical features of these cases, results of radiological investigations, treatment, and outcome were drawn from the patients' records. Results: Eight cases of NegPH were identified. All patients had at least one preceding intracranial procedure (mean number of procedures 3.0). All cases were treated using TEVD, titrated to produce between 5 and 15 mL per hour of CSF drainage, including drainage under subatmospheric pressure if this was required to maintain CSF flow. Mean delay from first negative ICP to TEVD was 1.8 days. All 8 patients demonstrated clinical improvement. TEVD resulted in improvement in Glasgow Coma Scale (mean increase 4.6, p = 0.003), and increases in ICP (mean increase 8.5, p < 0.001). Mean length of follow-up was 471.8 days. At follow-up, four patients had returned to pre-morbid functioning, three had a reduction in functioning attributable to their initial presentation (not NegPH), and one had died of unknown cause. Illustrative case descriptions are included. Conclusions: Negative-pressure hydrocephalus is a rare but underrecognised syndrome that can be successfully treated by timely external ventricular drainage titrated to maintain CSF flow, and subsequent low-pressure ventriculoperitoneal shunting. [ABSTRACT FROM AUTHOR]

BACKGROUND: This study evaluates the efficacy of negative-pressure therapy (NPT) in preventing surgical site infections (SSIs) in high-risk surgical oncology patients. METHODS: A retrospective analysis of 191 operations for colorectal, pancreatic, or peritoneal sur-face malignancies was performed. Incisional NPT was used in patients with multiple SSI risk factors. Rates of SSIs were compared with patients treated with a standard sterile dressing (SSD). RESULTS: NPT was used in 104 patients, whereas SSDs were used in 87 patients. Despite being at an increased risk of SSI, patients treated with NPT developed fewer superficial incisional SSIs com-pared with SSD patients (6.7% vs 19.5%, P = .015). In a subgroup analysis of clean-contaminated cases, NPT was associated with fewer superficial incisional SSIs (6.0% vs 27.4%, P = .001), fewer total SSIs (16.0% vs 35.5%, P = .011), and fewer wound openings for any reason (16.0% vs 35.5%, P = .011). CONCLUSIONS: Our findings suggest that NPT decreases SSIs in high-risk surgical oncology patients. [ABSTRACT FROM AUTHOR]

Abstract: Low-pressure hydrocephalus is a rare type of hydrocephalus characterized by negative intracranial pressure (ICP) and ventriculomegaly. Given the shortcomings of available methods to treat refractory low-pressure hydrocephalus, we set out to develop a new system for evacuation of cerebrospinal fluid (CSF) from the ventricular system where existing shunt systems do not produce the necessary gradient for CSF drainage. We retrospectively reviewed the charts of two patients with the diagnosis of negative-pressure hydrocephalus refractory to traditional treatments. We combined a traditional low-pressure, non-siphoning valve with a pumping chamber placed distal to the valve to create a system that could be actively pumped to remove excess CSF. Treatment of negative-pressure hydrocephalus requires the establishment of a lower ventricular drainage pressure than the drainage pressure in the subarachnoid space. In refractory cases, we propose the use of this active negative-pressure pumping system. [Copyright &y& Elsevier]

Summary Background and objective Few and conflicting data are available regarding the changes of plasma potassium concentration during acute respiratory acidosis in human beings. This study compares the acute changes in plasma potassium concentration in acutely hypercapnic patients and in non-hypercapnic patients during general anaesthesia. Methods Thirty-three patients undergoing interventional rigid bronchoscopy were studied. Ventilation of the lungs was randomly conducted using either spontaneous-assisted ventilation or intermittent negative-pressure ventilation. All patients received the same anaesthetic protocol. Arterial blood gases and osmolality, and plasma concentrations of glucose, sodium, potassium and chloride were measured. Results Intraoperatively, PaCO2 was higher during spontaneous-assisted ventilation than during intermittent negative-pressure ventilation (9 ± 1.8 vs. 5.4 ± 1.2 kPa, P < 0.001) and the pH was also lower during spontaneous-assisted ventilation than during intermittent negative-pressure ventilation (7.24 ± 0.07 vs. 7.4 ± 0.08, P < 0.001). Plasma potassium concentration remained similar in both groups (3.8 ± 0.2 mmol L-1 with spontaneous-assisted ventilation vs. 3.7 ± 0.4 mmol L-1 with intermittent negative-pressure ventilation). Conclusion Acute respiratory acidosis does not affect plasma potassium concentration. [ABSTRACT FROM AUTHOR]