Terapia de presión negativa para pacientes con enfisema subcutáneo y neumomediastino masivo / Negative pressure therapy for patients with subcutaneous emphysemaand massive pneumomediastinum

Se han descrito diversas técnicas para el tratamiento del enfisema subcutáneo y del neumomediastino. Algunos pacientes con pequeñas perforaciones traqueales pueden ser manejados de forma expectante, salvo que requieran ventilación mecánica. Se presentan las imágenes de un paciente con enfisema subcutáneo y neumomediastino no candidato a cirugía y quien fue tratado exitosamente con terapia de presión negativa.

Different techniques have been described for the treatment of subcutaneous emphysema and pneumomediatinum. Some patients with small tracheal perforations can be managed expectantly, unless they require mechanical ventilation. Images of a patient with subcutaneous emphysema and pneumomediastinum not a candidate for surgery and who was successfully treated with negative pressure therapy are presented.

Effects of mechanical ventilation with expiratory negative airway pressure on porcine pulmonary and systemic circulation: mechano-physiology and potential application.

We studied the impact of mechanically regulated, expiratory negative airway pressure (ENAP) ventilation on pulmonary and systemic circulation including its mechanisms and potential applications. Microminipigs weighing about 10 kg were anesthetized (n = 5). First, hemodynamic variables were evaluated without and with ENAP to approximately -16 cmH2O. ENAP significantly increased heart rate and cardiac output, but decreased right atrial, pulmonary arterial and pulmonary capillary wedge pressures. Second, the evaluation was repeated following pharmacological adrenergic blockade, modestly blunting ENAP effects. Third, fluvoxamine (10 mg/kg) was intravenously administered to intentionally induce cardiovascular collapse in the presence of adrenergic blockade. ENAP was started when systolic pressure was < 40 mmHg in the animals assigned to ENAP treatment-group. Fluvoxamine induced cardiovascular collapse within 4 out of 5 animals. ENAP increased systolic pressure to > 50 mmHg (n = 2): both animals fully recovered without neurological deficit, whereas without ENAP both animals died of cardiac arrest (n = 2). ENAP may become an innovative treatment for drug-induced cardiovascular collapse.

Impact of negative pressure system on microbiological air quality in a Central Sterile Supply Department.

OBJECTIVE: Guidelines recommend that the cleaning area in a Central Sterile Supply Department (CSSD) maintain a negative pressure of the environmental air, but how much this system can impact the contamination of the air by bioaerosols in the area is not known. The objective of this study was to assess the impact of negative pressure on CSSD by evaluating the microbiological air quality of this sector. METHODS: Microbiological air samples were collected in two CSSD in the same hospital: one with and one without a negative air pressure system. Outdoor air samples were collected as a comparative control. Andersen six-stage air sampler was used to obtain the microbiological air samples. RESULTS: The concentration of bioaerosols in the CSSD without negative pressure was 273.15 and 206.71 CFU/m3 , while in the CSSD with negative pressure the concentration of bioaerosols was 116.96 CFU/m3 and 131.10 CFU/m3 . The number of isolated colonies in the negative pressure CSSD was significantly lower (P = .01541). CONCLUSION: The findings showed that the negative pressure system in the CSSD cleaning area contributed to the quantitative reduction in bioaerosols. However, the concentration of bioaerosols was lower than that established in the guideline for indoor air quality of many countries. Therefore, it cannot be concluded that CSSDs which do not have a negative pressure system in their cleaning area offer occupational risk.

Comparing the effectiveness of negative-pressure barrier devices in providing air clearance to prevent aerosol transmission.

PURPOSE: To investigate the effectiveness of aerosol clearance using an aerosol box, aerosol bag, wall suction, and a high-efficiency particulate air (HEPA) filter evacuator to prevent aerosol transmission. METHODS: The flow field was visualized using three protective device settings (an aerosol box, and an aerosol bag with and without sealed working channels) and four suction settings (no suction, wall suction, and a HEPA filter evacuator at flow rates of 415 liters per minute [LPM] and 530 LPM). All 12 subgroups were compared with a no intervention group. The primary outcome, aerosol concentration, was measured at the head, trunk, and foot of a mannequin. RESULTS: The mean aerosol concentration was reduced at the head (p < 0.001) but increased at the feet (p = 0.005) with an aerosol box compared with no intervention. Non-sealed aerosol bags increased exposure at the head and trunk (both, p < 0.001). Sealed aerosol bags reduced aerosol concentration at the head, trunk, and foot of the mannequin (p < 0.001). A sealed aerosol bag alone, with wall suction, or with a HEPA filter evacuator reduced the aerosol concentration at the head by 7.15%, 36.61%, and 84.70%, respectively (99.9% confidence interval [CI]: -4.51-18.81, 27.48-45.73, and 78.99-90.40); trunk by 70.95%, 73.99%, and 91.59%, respectively (99.9% CI: 59.83-82.07, 52.64-95.33, and 87.51-95.66); and feet by 69.16%, 75.57%, and 92.30%, respectively (99.9% CI: 63.18-75.15, 69.76-81.37, and 88.18-96.42), compared with an aerosol box alone. CONCLUSIONS: As aerosols spread, an airtight container with sealed working channels is effective when combined with suction devices.

A Novel Negative Pressure-Flow Waveform to Ventilate Lungs for Normothermic Ex Vivo Lung Perfusion.

Ex vivo lung perfusion (EVLP) is increasingly used to treat and assess lungs before transplant. Minimizing ventilator induced lung injury (VILI) during EVLP is an important clinical need, and negative pressure ventilation (NPV) may reduce VILI compared with conventional positive pressure ventilation (PPV). However, it is not clear if NPV is intrinsically lung protective or if differences in respiratory pressure-flow waveforms are responsible for reduced VILI during NPV. In this study, we quantified lung injury using novel pressure-flow waveforms during normothermic EVLP. Rat lungs were ventilated-perfused ex vivo for 2 hours using tidal volume, positive end-expiratory pressure (PEEP), and respiratory rate matched PPV or NPV protocols. Airway pressures and flow rates were measured in real time and lungs were assessed for changes in compliance, pulmonary vascular resistance, oxygenation, edema, and cytokine secretion. Negative pressure ventilation lungs demonstrated reduced proinflammatory cytokine secretion, reduced weight gain, and reduced pulmonary vascular resistance (p < 0.05). Compliance was higher in NPV lungs (p < 0.05), and there was no difference in oxygenation between the two groups. Respiratory pressure-flow waveforms during NPV and PPV were significantly different (p < 0.05), especially during the inspiratory phase, where the NPV group exhibited rapid time-dependent changes in pressure and airflow whereas the PPV group exhibited slower changes in airflow/pressures. Lungs ventilated with PPV also had a greater transpulmonary pressure (p < 0.05). Greater improvement in lung function during NPV EVLP may be caused by favorable airflow patterns and/or pressure dynamics, which may better mimic human respiratory patterns.

Clinical transplantation using negative pressure ventilation ex situ lung perfusion with extended criteria donor lungs.

Lung transplantation remains the best treatment option for end-stage lung disease; however, is limited by a shortage of donor grafts. Ex situ lung perfusion, also known as ex vivo lung perfusion, has been shown to allow for the safe evaluation and reconditioning of extended criteria donor lungs, increasing donor utilization. Negative pressure ventilation ex situ lung perfusion has been shown, preclinically, to result in less ventilator-induced lung injury than positive pressure ventilation. Here we demonstrate that, in a single-arm interventional study (ClinicalTrials.gov number NCT03293043) of 12 extended criteria donor human lungs, negative pressure ventilation ex situ lung perfusion allows for preservation and evaluation of donor lungs with all grafts and patients surviving to 30 days and recovered to discharge from hospital. This trial also demonstrates that ex situ lung perfusion is safe and feasible with no patients demonstrating primary graft dysfunction scores grade 3 at 72 h or requiring post-operative extracorporeal membrane oxygenation.

Near-fatal negative pressure pulmonary oedema successfully treated with venovenous extracorporeal membrane oxygenation performed in the hybrid emergency room.

We report a rare case of negative pressure pulmonary oedema (NPPE), a life-threatening complication of tracheal intubation. A 41-year-old obese man was admitted to a previous hospital for neck surgery. After extubation, he developed respiratory distress followed by haemoptysis and desaturation. The patient was reintubated and brought to our hospital where we introduced venovenous extracorporeal membrane oxygenation (ECMO) to prevent cardiac arrest, which is an unusual clinical course for NPPE. He returned to his routine without any sequelae. This is the first case report of NPPE successfully resolved with venovenous ECMO in the hybrid emergency room (hybrid ER), which is a resuscitation room equipped with interventional radiology features and a sliding CT scanner. Since the hybrid ER serves as a single move for patients where all necessary procedures are performed, it has the potential to lower the incidence of cannulation complications, beyond the delay in ECMO initiation.

Feasibility of neurally synchronized and proportional negative pressure ventilation in a small animal model.

RATIONALE: Synchronized positive pressure ventilation is possible using diaphragm electrical activity (EAdi) to control the ventilator. It is unknown whether EAdi can be used to control negative pressure ventilation. AIM: To evaluate the feasibility of using EAdi to control negative pressure ventilation. METHODS: Fourteen anesthetized rats were studied (380-590 g) during control, resistive breathing, acute lung injury or CO2 rebreathing. Positive pressure continuous neurally adjusted ventilatory assist (cNAVAP+ ) was applied via intubation. Negative pressure cNAVA (cNAVAP- ) was applied with the animal placed in a sealed box. In part 1, automatic stepwise increments in cNAVA level by 0.2 cmH2 O/µV every 30 s was applied for cNAVAP+ , cNAVAP- , and a 50/50 combination of the two (cNAVAP± ). In part 2: During 5-min ventilation with cNAVAP+ or cNAVAP- we measured circuit, box, and esophageal (Pes) pressure, EAdi, blood pressure, and arterial blood gases. RESULTS: Part 1: During cNAVAP+ , pressure in the circuit increased with increasing cNAVA levels, reaching a plateau, and similarly for cNAVAP- , albeit reversed in sign. This was associated with downregulation of the EAdi. Pes swings became less negative with cNAVAP+ but, in contrast, Pes swings were more negative during increasing cNAVAP- levels. Increasing the cNAVA level during cNAVAP± resulted in an intermediate response. Part 2: no significant differences were observed for box/circuit pressures, EAdi, blood pressure, or arterial blood gases. Pes swings during cNAVAP- were significantly more negative than during cNAVAP+ . CONCLUSION: Negative pressure ventilation synchronized and proportional to the diaphragm activity is feasible in small animals.

A Novel Negative Pressure Isolation Device for Aerosol Transmissible COVID-19.

The coronavirus disease 2019 (COVID-19) pandemic creates a need to protect health care workers (HCWs) from patients undergoing aerosol-generating procedures which may transmit the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). Existing personal containment devices (PCDs) may protect HCWs from respiratory droplets but not from potentially dangerous respiratory-generated aerosols. We describe a new PCD and its aerosol containment capabilities. The device ships flat and folds into a chamber. With its torso drape and protective arm sleeves mounted, it provides contact, droplet, and aerosol isolation during intubation and cardiopulmonary resuscitation (CPR). Significantly improved ergonomics, single-use workflow, and ease of removal distinguish this device from previously published designs.

Aerosolized Particle Reduction: A Novel Cadaveric Model and a Negative Airway Pressure Respirator (NAPR) System to Protect Health Care Workers From COVID-19.

OBJECTIVES: This study aimed to identify escape of small-particle aerosols from a variety of masks using simulated breathing conditions. This study also aimed to evaluate the efficacy of a negative-pressure environment around the face in preventing the escape of small aerosolized particles. STUDY DESIGN: This study is an evaluation study with specific methodology described below. SETTING: This study was performed in our institution's fresh tissue laboratory. SUBJECTS AND METHODS: A fixed cadaver head was placed in a controlled environment with a black background, and small-particle aerosols were created using joss incense sticks (mass-median aerosol diameter of 0.28 µ). Smoke was passed through the cadaver head, and images were taken with a high-resolution camera in a standardized manner. Digital image processing was used to calculate relative amounts of small-particle escape from a variety of masks, including a standard surgical mask, a modified Ambu mask, and our negative airway pressure respirator (NAPR). RESULTS: Significant amounts of aerosolized particles escaped during the trials with no mask, a standard surgical mask, and the NAPR without suction. When suction was applied to the NAPR, creating a negative-pressure system, no particle escape was noted. CONCLUSION: We present a new and effective method for the study of small-particle aerosols as a step toward better understanding the spread of these particles and the transmission of coronavirus disease 2019. We also present the concept of an NAPR to better protect health care workers from aerosols generated from the upper and lower airways.

Predictors of Negative Pressure Ventilation Response in Pediatric Acute Respiratory Failure.

BACKGROUND: Use of negative pressure ventilation is neither well described nor widespread in pediatric critical care; existing data are from small, specialized populations. We sought to describe a general population of critically ill subjects with acute respiratory failure supported with negative pressure ventilation to find predictors of response or failure. METHODS: We conducted a retrospective cohort study of subjects 0-18 y old admitted to a single (non-cardiac) pediatric ICU who received acute respiratory failure support via negative pressure ventilation from May 2015 through May 2016. RESULTS: In 118 subjects, the most common causes of acute respiratory failure were viral bronchiolitis (86.4%) and pneumonia (15.3%). A majority of subjects (68.6%) stabilized with negative pressure ventilation and did not need a change of respiratory support; in those who failed with negative pressure ventilation, median time to respiratory support change was 5.1 h (interquartile range 1.9-11.0). Subjects stabilized with negative pressure ventilation did not differ from those needing a change of respiratory support in terms of age, comorbidities, or FIO2 at initiation of ventilation. Compared to those who did not respond to negative pressure ventilation, mean SpO2 /FIO2 was higher at 1 h after start of negative pressure ventilation (218.8 vs 131.7) in those who did respond. Subjects with SpO2 /FIO2 < 192 after 1 h on negative pressure ventilation support had 5-fold higher odds of needing a respiratory support change (odds ratio 5.143, 95% CI 1.17-22.7, P = .031). Analysis of SpO2 /FIO2 was limited by 81.3% (96/118) of subjects who had an SpO2 > 97% at 1 h after the start of negative pressure ventilation. CONCLUSIONS: Negative pressure ventilation successfully supported 69% of pediatric subjects with all-cause acute respiratory failure. Oxygen requirement was lower in subjects who were responsive to negative pressure ventilation within 1 h of initiation. Standardized negative pressure ventilation protocols should include weaning of supplemental oxygen to determine responsiveness.

Philip Drinker versus John Haven Emerson: Battle of the iron lung machines, 1928-1940.

The "iron lung," originally known as the Drinker respirator, was developed in 1928 by Dr Philip Drinker and Dr Louis Agassiz Shaw to improve the respiration of polio patients. In 1931, John Haven Emerson, an inventor from Cambridge, MA, enhanced the design of the Drinker respirator and introduced a new and highly improved model of the iron lung that was cheaper and significantly lighter. Dr Drinker eventually filed a lawsuit against Emerson for alleged patent infringement. In his defense, Emerson argued that devices that help save human lives should be widely accessible to all patients. He also questioned the novelty of Drinker's design, claiming that Drinker's device comprised of patented technology that existed since the late 1800s, and that he therefore did not have full ownership of the machine's intellectual property. Ultimately, the case backfired on Drinker, as he not only lost the court case but also lost the entire panel of patents that were in his possession.

Thunberg's Barospirator, a Fully Encasing Predecessor of the Iron Lung.

Used as a ventilator for assisting victims of polio, the barospirator was described by Swedish physician-scientist Torsten Thunberg in 1924. An immediate predecessor of the iron lung of Philip Drinker, the barospirator fully encased the entire body. Cyclic air-pressure changes within the chamber achieved ventilation during equilibrations of intrapulmonary and ambient pressures. Pulmonary medicine innovator Alvan Leroy Barach used a modified barospirator for lung rest as a treatment of tuberculosis in the 1940s. Adverse effects included damage to patients' tympanic membranes. Despite its limited clinical success, the barospirator was successfully used by one of Drinker's competitors, John H. Emerson, to invalidate Drinker's US patent filings.

Acute Hemodynamic Effects of Negative Extrathoracic Pressure in Fontan Physiology.

We sought to assess acute hemodynamic changes after implementation of negative extrathoracic pressure (NEP) in spontaneously breathing ambulatory Fontan patients with symptomatic heart failure. We hypothesized that application of NEP would result in an acute decrease in pulmonary artery pressure. Ten patients with clinical evidence of Fontan failure underwent baseline hemodynamic catheterization while breathing spontaneously. Hemodynamic measurements were then repeated after 30 min of continuous NEP. After 30 min of continuous NEP, 4/10 patients had a decrease in their Fontan pressure by 2 mmHg and one patient had a decrease by 1 mmHg. There were three patients that had an increase in Fontan pressure by 2 mmHg. In 7/10 patients, indexed pulmonary vascular resistance decreased by an average of 31%. In symptomatic Fontan patients with a favorable hemodynamic response to NEP during catheterization, potential benefit of longer-term NEP to improve clinical status should be explored.

An acute exposure to intermittent negative airway pressure elicits respiratory long-term facilitation in awake humans.

BACKGROUND: A sustained elevation in respiratory drive following removal of the inducing stimulus is known as respiratory long-term facilitation (rLTF). We investigated whether an acute exposure to intermittent negative airway pressure (INAP) elicits rLTF in humans. METHOD: 13 healthy males (20.9 ±â€¯2.8 years) undertook two trials (INAP and Control). In the INAP trial participants were exposed to one hour of 30-second episodes of breathing against negative pressure (-10 cmH2O) interspersed by 60-second intervals of breathing at atmospheric pressure. In the Control trial participants breathed at atmospheric pressure for one hour. Ventilation following INAP (recovery phase) was compared to that during baseline. RESULTS: Ventilation increased from baseline to recovery in the INAP trial (14.9 ±â€¯0.9 vs 19.1 ±â€¯0.7 L/min, P = 0.002). This increase was significantly greater than the equivalent during the Control trial (P = 0.019). Data shown as mean ± SEM. CONCLUSION: In this study INAP elicited rLTF in awake, healthy humans. Further research is required to investigate the responsible mechanisms.

A novel intermittent negative air pressure device ameliorates obstructive sleep apnea syndrome in adults.

PURPOSE: Patients with obstructive sleep apnea syndrome (OSAS) have difficulties in compliance with continuous positive airway pressure (CPAP) and the treatment outcome is heterogeneous. We proposed a proof-of-concept study of a novel intermittent negative air pressure (iNAP®) device for physicians to apply on patients who have failed or refused to use CPAP. METHODS: The iNAP® device retains the tongue and the soft palate in a forward position to decrease airway obstruction. A full nightly usage with the device was evaluated with polysomnography. Subgrouping by baseline apnea-hypopnea index (AHI) and body mass index (BMI) with different treatment response criteria was applied to characterize the responder group of this novel device. RESULTS: Thirty-five patients were enrolled: age 41.9 ± 12.2 years (mean ± standard deviation), BMI 26.6 ± 4.3 kg/m2, AHI 41.4 ± 24.3 events/h, and oxygen desaturation index (ODI) 40.9 ± 24.4 events/h at baseline. AHI and ODI were significantly decreased (p < 0.001) by the device. Patients with moderate OSAS, with baseline AHI between 15 to 30 events/h, achieved 64% response rate; and non-obese patients, with BMI below 25 kg/m2, achieved 57% response rate, with response rate defined as 50% reduction in AHI from baseline and treated AHI lower than 20. There were minimal side effects reported. CONCLUSIONS: In a proof-of-concept study, the device attained response to treatment as defined, in more than half of the moderate and non-obese OSAS patients, with minimal side effects.

Positive pressure ventilation compresses pulmonary acinar microvessels but not their supply vessels.

Pulmonary alveolar septal capillaries receive their perfusion from a web of larger surrounding acinar vessels. Using 4 µm diam. Latex particles, we showed that positive pressure ventilation narrowed the acinar vessels as evidenced by venous 4 µm particle concentrations and perfusate flows <50% of particle concentrations in negative pressure ventilated lungs. We aimed to understand the effects of positive and negative pressure ventilation on flows of larger particles through the lung. Isolated, ventilated rat lungs (air, transpulmonary pressures of 15/5 cm H2O, 25 breaths/min) were perfused with a hetastarch solution at Ppulm art/PLA pressures of 10/0 cm H2O. Red latex 7 µm (2.5 mg, 4.8 × 106) or 15 µm (2.5 mg, 5.5 × 105) particles were infused into each lung during positive or negative pressure ventilation. An equal number of green particles was infused 20 min later. Flows through lungs infused with 7 µm and 15 µm particles were not different from flows through lungs infused with 4 µm particles (p = 0.811). Venous particle concentrations of 7 µm particles relative to infused particles were lower in positive pressure lungs (0.03 ±â€¯0.03%) compared to negative pressure lungs (0.17 ±â€¯0.12%) (p = 0.041). Venous particle concentrations of 15 µm particles were not different between positive (2.3 ±â€¯1.9%) and negative (3.3 ±â€¯1.8%) pressure ventilation (p = 0.406). Together with our previous study, we conclude that 4 µm and 7 µm particles both enter acinar vessels but that the 7 µm particles are too large to flow through those vessels. In contrast, we conclude that 15 µm particles bypass the acinar vessels, flowing instead through larger intrapulmonary vessels to enter the venous outflow. These findings suggest that intrapulmonary vessels are organized as a web that allows bypass of the acinar vessels by large particles and, that these bypass vessels are not compressed by positive pressure ventilation.

Devising negative pressure within intercuff space reduces microaspiration.

BACKGROUND: Microaspiration past the tracheal tube cuffs causes ventilator-associated pneumonia. The objective of the current study was to evaluate whether creating negative pressure between the tracheal double cuffs could block the fluid passage past the tracheal tube cuffs. METHODS: A new negative pressure system was devised between the double cuffs through a suction hole in the intercuff space. Blue-dyed water was instilled above the cuff at negative suction pressures of - 54, - 68, - 82, - 95, - 109, - 122, and - 136 cmH2O, and the volume leaked was measured in an underlying water trap after 10 min. Leakage tests were also performed during positive pressure ventilation, and using higher-viscosity materials. The actual negative pressures delivered at the hole of double cuffs were obtained by placing microcatheter tip between the intercuff space and the artificial trachea. RESULTS: No leakage occurred past the double cuff at - 136 cmH2O suction pressure at all tracheal tube cuff pressures. The volume leaked decreased significantly as suction pressure increased. When connected to a mechanical ventilator, no leakage was found at - 54 cmH2suction pressure. Volume of the higher-viscosity materials (dynamic viscosity of 63-108 cP and 370-430 cP) leaked was small compared to that of normal saline (0.9-1.1 cP). The pressures measured in the intercuff space corresponded to 3.8-5.9% of those applied. CONCLUSIONS: A new prototype double cuff with negative pressure in the intercuff space completely prevented water leakage. The negative pressure transmitted to the tracheal inner wall was a small percentage of that applied.