Intermittent Negative Pressure Research Articles

Medicine's Glass Slipper: The PAVAEX Boot and 20th Century Negative Pressure Therapy.

Before the 20th century, peripheral artery disease (PAD) manifested as extreme pain, chronic wounds, and, eventually, gangrene requiring amputation. Despite this, it was rarely diagnosed. However, at the turn of the century, Western medicine shifted focus from infectious to chronic illnesses, and with this change, physicians' engagement with PAD transformed. Aiming to mitigate long-term injury, physicians now worked to identify and treat vessel disease to restore meaningful blood circulation. This article explores the development and deployment of a new device resulting from this refocus, the PAssive VAscular EXerciser (PAVAEX) Boot, and its role as a creative response to a previously intractable clinical problem. The PAVAEX Boot, designed in 1933 by vascular surgeons Louis G. Herrmann and Mont R. Reid, was one of the few interventions for PAD at the time. Based on the observation that continuous negative pressure results in vasoconstriction, while short bursts transiently increase blood flow, the PAVAEX Boot utilized intermittent negative pressure to enhance peripheral vascular perfusion. Well-marketed and praised throughout the 1930s, it vanished from public writing and academic literature just 20years later. However, negative pressure wound therapy resurged in the late 20th century, and though its inventors failed to recognize the precedent of the PAVAEX Boot, many of these devices and therapies are rooted in identical theories. We examine why the PAVAEX Boot faded from use and argue that the device remains a crucial advancement in negative pressure therapy.

Negative Pressure Level and Effects on Bacterial Growth Kinetics in an in vitro Wound Model.

Negative Pressure Wound Therapy (NPWT) has been widely adopted in wound healing strategies due to its multimodal mechanism of action. While NPWT's positive impression on wound healing is well-established, its effect on bacterial load reduction remains equivocal. This study investigates NPWT's efficacy in reducing bioburden using an in vitro porcine skin model, focusing on the impact of Staphylococcus aureus and Staphylococcus epidermidis. Custom-made negative pressure chambers were employed to apply varying negative pressures. Porcine skin was cut into 5 × 5 cm squares and three standardized wounds of 6 mm each were created using a biopsy punch. Then, wounds were infected with S. aureus and S. epidermidis bacterial suspensions diluted 1:10,000 to obtain a final concentration of 1.5 × 104 CFU/ml and were placed in negative pressure chambers. After incubation, bacterial counts were expressed as colony-forming units (CFU) per ml. For S. aureus at 120 hours, the median CFU, mean area per colony, and total growth area were notably lower at -80 mmHg when compared to -250 mmHg and -50 mmHg, suggesting an optimal negative pressure for the pressure-dependent inhibition of the bacterial proliferation. While analyzing S. epidermidis at 120 hours, the response to the negative pressure was similar but less clear, with the minor CFU at -100 mmHg. The influence of intermittent negative pressure on the S. epidermidis growth showed notably lower median CFU with the interval therapy every hour compared to the S. aureus control group. This study contributes valuable insights into NPWT's influence on the bacterial load, emphasizing the need for further research to reformulate its role in managing contaminated wounds.

Catheter-based pulmonary vein isolation fails to prevent transient atrial arrhythmogenic changes related to acute obstructive respiratory events in a porcine model.

Pulmonary vein isolation (PVI) is the corner stone of modern rhythm control strategies in patients with atrial fibrillation (AF). Sleep-disordered breathing (SDB) is prevalent in more than 50% of patients undergoing AF ablation, and studies have indicated a greater recurrence rate after PVI in patients with SDB. Herein, we study the effect of catheter-based PVI on AF in a pig model for SDB. In 11 sedated spontaneously breathing pigs, obstructive apnoeas were simulated by 75 s of intermittent negative upper airway pressure (INAP) applied by a negative pressure device connected to the endotracheal tube. Intermittent negative upper airway pressures were performed before and after PVI. AF-inducibility and atrial effective refractory periods (aERPs) were determined before and during INAP by programmed atrial stimulation. Pulmonary vein isolation prolonged the aERP by 48 ± 27 ms in the right atrium (RA) (P < 0.0001) and by 40 ± 34 ms in the left atrium (LA) (P = 0.0004). Following PVI, AF-inducibility dropped from 28 ± 26% to 0% (P = 0.0009). Intermittent negative upper airway pressure was associated with a transient aERP-shortening (ΔaERP) in both atria, which was not prevented by PVI (INAP indued ΔaERP after PVI in the RA: -57 ± 34 ms, P = 0.0002; in the LA: -42 ± 24 ms, P < 0.0001). Intermittent negative upper airway pressure was associated with a transient increase in AF-inducibility (from 28 ± 26% to 69 ± 21%; P = 0.0008), which was not attenuated by PVI [INAP-associated AF-inducibility after PVI: 58 ± 33% (P = 0.5)]. Transient atrial arrhythmogenic changes related to acute obstructive respiratory events are not prevented by electrical isolation of the pulmonary veins, which partially explains the increased AF recurrence in patients with SDB after PVI procedures.

Inhibition of the acetylcholine-regulated potassium current prevents transient apnea-related atrial arrhythmogenic changes in a porcine model

BackgroundMore than 50% of patients with atrial fibrillation (AF) suffer from sleep disordered breathing (SDB). Obstructive respiratory events contribute to a transient, vagally mediated atrial arrhythmogenic substrate, which is resistant to most available antiarrhythmic drugs. ObjectiveThe purpose of this study was to investigate the effect of pharmacologic inhibition of the G-protein–gated acetylcholine-regulated potassium current (IK,ACh) with and without acute autonomic nervous system activation by nicotine in a pig model for obstructive respiratory events. MethodsIn 21 pigs, SDB was simulated by applying an intermittent negative upper airway pressure (INAP). AF inducibility and atrial effective refractory periods (aERPs) were determined before and during INAP by an S1S2 atrial pacing-protocol. Pigs were randomized into 3 groups—group 1: vehicle (n = 4); group 2: XAF-1407 (IK,ACh inhibitor) (n = 7); and group 3: nicotine followed by XAF-1407 (n = 10). ResultsIn group 1, INAP shortened aERP (ΔaERP –42.6 ms; P = .004) and transiently increased AF inducibility from 0% to 31%. In group 2, XAF-1407 prolonged aERP by 25.2 ms (P = .005) during normal breathing and prevented INAP-induced aERP shortening (ΔaERP –3.6 ms; P = .3) and AF inducibility. In group 3, INAP transiently shortened aERP during nicotine perfusion (ΔaERP –33.6 ms; P = .004) and increased AF inducibility up to 61%, which both were prevented by XAF-1407. ConclusionSimulated obstructive respiratory events transiently shorten aERP and increase AF inducibility, which can be prevented by the IK,ACh-inhibitor XAF-1407. XAF-1407 also prevents these arrhythmogenic changes induced by obstructive respiratory events during nicotine perfusion. Whether IK,ACh channels represent a target for SDB-related AF in humans warrants further study.

The Sandwich Technique for Quick and Efficient Application of Negative Pressure Wound Therapy to the Feet and Hands: A Case Report

Introduction. NPWT is a surgical dressing that combines polyurethane foam with the subsequent application of continuous or intermittent negative pressure. NPWT facilitates granulation tissue production by macrostrain, microstrain and, if desired, fluid instillation. Sealing the polyurethane foam over the wound bed is achieved using acrylic drapes; however, this can be difficult to use in some anatomic sites. Failure to achieve an effective seal can necessitate additional supplies, which has led to increased innovation in developing a more effective NPWT seal over the target wound bed. Obtaining an effective pressure seal on the feet or hands can be difficult because these anatomic sites have distinct curvature for each digit, with multiple interdigital web spaces and independent mobility. In this case report, the authors propose a technique to apply either an acrylic drape or combination acrylic and soft silicone drape utilizing the “sandwich technique” to seal NPWT foam quickly and efficiently to the feet or hands.

Novel cell culture system for monitoring cells during continuous and variable negative-pressure wound therapy.

Although the clinical efficacy of negative-pressure wound therapy (NPWT) is well known, many of its molecular biological mechanisms remain unresolved, mainly due to the difficulty and paucity of relevant in vitro studies. We attempted to develop an in vitro cell culture system capable of real-time monitoring of cells during NPWT treatment. A novel negative-pressure cell culture system was developed by combining an inverted microscope, a stage-top incubator, a sealed metal chamber for cell culture, and an NPWT treatment device. Human keratinocytes, PSVK-1, were divided into ambient pressure (AP), continuous negative-pressure (NPc), and intermittent negative-pressure (NPi) groups and cultured for 24h with scratch assay using our real-time monitoring system and device. Pressure inside the device, medium evaporation rate, and the residual wound area were compared across the groups. Pressure in the device was maintained at almost the same value as set in all groups. Medium evaporation rate was significantly higher in the NPi group than in the other two groups; however, it had negligible effect on cell culture. Residual wound area after 9h evaluated by the scratch assay was significantly smaller in the NPc and NPi groups than in the AP group. We developed a negative-pressure cell culture device that enables negative-pressure cell culture under conditions similar to those used in clinical practice and is able to monitor cells under NPWT. Further experiments using this device would provide high-quality molecular biological evidence for NPWT.

Pharmacological inhibition of SK-channels with AP14145 prevents atrial arrhythmogenic changes in a porcine model for obstructive respiratory events.

Obstructive sleep apnea (OSA) creates a complex substrate for atrial fibrillation (AF), which is refractory to many clinically available pharmacological interventions. We investigated atrial antiarrhythmogenic properties and ventricular electrophysiological safety of small-conductance Ca2+ -activated K+ (SK)-channel inhibition in a porcine model for obstructive respiratory events. In spontaneously breathing pigs, obstructive respiratory events were simulated by intermittent negative upper airway pressure (INAP) applied via a pressure device connected to the intubation tube. INAP was applied for 75 s, every 10 min, three times before and three times during infusion of the SK-channel inhibitor AP14145. Atrial effective refractory periods (AERP) were acquired before (pre-INAP), during (INAP) and after (post-) INAP. AF-inducibility was determined by a S1S2 atrial pacing protocol. Ventricular arrhythmicity was evaluated by heart rate adjusted QT-interval duration (QT-paced) and electromechanical window (EMW) shortening. During vehicle infusion, INAP transiently shortened AERP (pre-INAP: 135 ± 10 ms vs. post-INAP 101 ± 11 ms; p = .008) and increased AF-inducibility. QT-paced prolonged during INAP (pre-INAP 270 ± 7 ms vs. INAP 275 ± 7 ms; p = .04) and EMW shortened progressively throughout INAP and post-INAP (pre-INAP 80 ± 4 ms; INAP 59 ± 6 ms, post-INAP 46 ± 10 ms). AP14145 prolonged baseline AERP, partially prevented INAP-induced AERP-shortening and reduced AF-susceptibility. AP14145 did not alter QT-paced at baseline (pre-AP14145 270 ± 7 ms vs. AP14145 268 ± 6 ms, p = .83) or QT-paced and EMW-shortening during INAP. In a pig model for obstructive respiratory events, the SK-channel-inhibitor AP14145 prevented INAP-associated AERP-shortening and AF-susceptibility without impairing ventricular electrophysiology. Whether SK-channels represent a target for OSA-related AF in humans warrants further study.

Management of a rare case of pediatric deep sternal wound infection with vacuum-assisted closure (VAC)

Background: Deep sternal wound infection (DSWI) or mediastinitis is a severe and life-threatening infection with high morbidity and mortality rates. Vacuum-assisted closure (VAC) provides good results and is very useful in wound closure. VAC therapy is a safe and affordable method for managing complex sternal and thoracic injuries. The use of VAC has been shown to increase parasternal blood flow by dilating arterioles, reducing bacterial load, and accelerating granulation tissue formation. It also helps with facilitating wound edge closure. Case and Operation Technique: A 6-month-old baby presented with an ulcer 2 cm deep in the thorax region. The wound had an exposed bone surrounded by slough and hyperemic edges. Bone destruction was seen to have reached the costochondral joint with a gross visible appearance of the pleura. Management of this patient included debridement, sternotomy, internal fixation of the sternum using the Robiscek technique, and application of the Water Shield Drainage (WSD) and VAC. The tobacco-sack technique was used to close the open wound. The Robiscek technique was used in this patient because of the bone destruction to the costochondral joints causing the sternum to become unstable. The VAC dressing was then connected to a suction with an intermittent negative pressure of 75mmHg. After a significant decrease in the wound surface area, a local rotational flap was used to close the wound. Conclusion: The use of modified VAC for deep sternal wound infection (DSWI) is effective, simple, and affordable with minimal complications.

Application of Comfort Therapy under eCASH Concept in Acute and Chronic Wound Treatment.

Given the new ideas on wound care offered by the eCASH (early Comfort using Analgesia, minimal Sedatives, and maximal Humane care) and the substantial differences in clinical treatment between acute and chronic wounds, we aimed to investigate the effect of comfort therapy under the eCASH concept on analgesic sedation and accelerated wound healing in patients with acute or chronic wounds. This randomized clinical study was conducted in two parts: acute wounds and chronic wounds. Patients with acute wounds were allocated into the acute wound control group (AWCG) and the acute wound experimental group (AWEG). Patients with chronic wounds were allocated into the chronic wound control group (CWCG) and two experimental groups, in which they received intermittent negative pressure therapy (IPTEG) and continuous negative pressure therapy (CPTEG). On the basis of the standard treatment for patients in the control group, eCASH therapy was used in the experimental groups. In addition, pain intensity and procedural anxiety were evaluated using the visual analogue score (VAS) and the Hamilton Anxiety Scale (HAM-A). In addition, clinical effects were assessed on the basis of the size of the surface area, rate of healing, and concentration of pro-inflammatory factors (IL-1, IL-6, TNF-α) and growth factors (VEGF, bFGF, TGF-β1). Compared with the control group, the VAS score and HAM-A score in the experimental groups were significantly decreased after intervention (P < 0.05). After intervention, the levels of IL-1β, IL-6, and TNF-α in AWEG, IPTEG, and CPTEG were significantly lower than those in AWCG. In addition, the levels of VEGF, bFGF, and TGF-β1 in IPTEG and CPTEG were significantly higher than those in CWCG (P < 0.05). These results indicated that comfort therapy under the eCASH concept has a significant effect on ameliorating the pain and anxiety of patients, reducing the inflammatory reaction during the period of wound healing in the treatment of acute and chronic wounds. The trial has been registered in the Chinese Clinical Trial Registry (ChiCTR2200057981).

Device for Negative Pressure Wound Therapy in Low-Resource Regions: Open-Source Description and Bench Test Evaluation.

Background: Negative (vacuum) pressure therapy promotes wound healing. However, commercially available devices are unaffordable to most potential users in low- and middle-income countries (LMICs), limiting access to many patients who could benefit from this treatment. This study aimed to design and test a cheap and easy-to-build negative pressure device and provide its detailed open-source description, thereby enabling free replication. Methods: the negative pressure device was built using off-the-shelf materials available via e-commerce and was based on a small pump, a pressure transducer, and the simplest Arduino controller with a digital display (total retail cost ≤ 75 US$). The device allows the user to set any therapeutic range of intermittent negative pressure and has two independent safety mechanisms. The performance of the low-cost device was carefully tested on the bench using a phantom wound, producing a realistic exudate flow rate. Results: the device generates the pressure patterns set by the user (25–175 mmHg of vacuum pressure, 0–60 min periods) and can drain exudate flows within the clinical range (up to 1 L/h). Conclusions: a novel, low-cost, easy-to-build negative pressure device for wound healing displays excellent technical performance. The open-source hardware description provided here, which allows for free replication and use in LMICs, will facilitate the application and wider utilization of this therapy to patients.

Effects and mechanism of negative pressure microenvironment on the neogenesis of human umbilical vein endothelial cells

Effects and mechanism of negative pressure microenvironment on the neogenesis of human umbilical vein endothelial cells

Sympatho-vagal activation during obstructive respiratory events in pigs and blunted atrial arrhythmogenic effects by pharmacological IKACh-inhibition

Abstract Funding Acknowledgements Type of funding sources: Foundation. Main funding source(s): Novo nordisk foundation Background Obstructive sleep apnea (OSA) is associated with a sympatho-vagal activation which is suspected to create a complex substrate for atrial fibrillation (AF). Purpose In pigs, we investigated atrial arrhythmogenic consequences of simulated obstructive respiratory events by intermittent negative upper airway pressure (INAP) application and tested antiarrhythmic properties of an atria-specific IK,ACh-inhibitor. Methods In spontaneously breathing pigs, obstructive respiratory events were simulated by intermittent negative upper airway pressure (INAP) applied via a pressure device connected to the intubation tube. INAP was applied for 75 seconds, every 10 minutes, three times before (vehicle) and two times following infusion of an IK,ACh-inhibitor. P-wave, PQ-duration, atrial effective refractory periods (AERP) and left ventricular hemodynamic parameters (maximum upstroke velocity, minimal downslope velocity and systole duration) were acquired before (Pre-INAP), during (INAP) and after (Post-) INAP. AF-inducibility was determined by a S1S2 atrial pacing protocol. Results During vehicle infusion, INAP transiently shortened AERP (Pre-INAP: 147±8ms vs. Post-INAP 105±12 ms; p=0.021) and increased AF-inducibility (Pre-INAP: 10±6% vs. Post-INAP 57±15%; p=0.018). Whereas p-wave duration remained stable, PQ-duration prolonged (Pre-INAP: 130±6ms vs. Post-INAP 142±7ms; p=0.03). Left ventricular maximum upstroke velocity increased (Pre-INAP: 1990±118 mmHg/s vs. Post-INAP 3980±704 mmHg/s; p=0.04), minimal downslope velocity decreased and systole duration shortened (Pre-INAP: 236±6 ms vs. Post-INAP 202±12 ms; p=0.04). The IK,ACh-inhibitor increased AERP (vehicle 147±8ms vs. IK,ACh-inhibitor 171±9ms; p=0.05) and sufficiently prevented INAP-associated AERP-shortening (Pre-INAP: 171±9ms vs. Post-INAP 180±9ms; p=0.219) and PQ-duration prolongation (Pre-INAP: 116±8ms vs. Post-INAP 113±7ms; p=0.76). INAP-induced changes of left ventricular maximum upstroke/minimal downslope velocity and systole duration remained unaffected in the presence of the IK,ACh-inhibitor. Conclusion During obstructive respiratory events simulated by INAP in pigs, left ventricular hemodynamic changes demonstrated elevated sympathetic tone, while atrial electrophysiological parameters resemble elevated parasympathetic tone at the same time. This was associated with increased AF-susceptibility. Pharmacological IK,ACh-inhibition blunted INAP-induced impairment of atrial electrophysiology without affecting left ventricular hemodynamic changes. Hence, pharmacological IKACh-inhibition may constitute a promising treatment strategy in AF-patients with OSA.

Differential effects of positive and negative upper airway pressure application on atrial electrophysiology: implications for CPAP-therapy in OSA-patients

Abstract Funding Acknowledgements Type of funding sources: Foundation. Main funding source(s): Novo nordisk foundation Background Obstructive sleep apnea (OSA) is closely associated with atrial fibrillation (AF) and OSA-treatment by continuous positive airway pressure (CPAP) is believed to reduce the AF burden in OSA-patients. While negative upper airway pressure during obstructive respiratory events have been shown to increase AF susceptibility, atrial electrophysiological effects of positive upper airway pressure during CPAP-therapy are unknown. Purpose In pigs, we investigated differential atrial electrophysiological effects of increasing levels of CPAP-applications compared to obstructive respiratory events. Methods In sedated and spontaneously breathing pigs, obstructive respiratory events were simulated by intermittent negative upper airway pressure (INAP) applied via a pressure device connected to the intubation tube. INAP was applied for 75 seconds with a 10 minute resting period in-between. After four INAP-applications, during which atrial electrophysiological responses to INAP were recorded, continuous positive airway pressure was applied in increasing pressure stages for a duration of 20 minutes for each pressure level (4, 8, 12 and 16 mbar). Atrial effective refractory periods (AERP) were recorded at the free wall of the right atrium (RA) and in the distal area of the coronary sinus (CS) before (Pre-INAP), during (INAP) and after (Post-) INAP and every 10 minutes throughout the stepwise increase of CPAP. Results AERP shortened due to INAP application in the RA (Pre-INAP 134±7ms vs. INAP 95±7ms; p=0.008, Fig.1.), but not in the CS (Pre-INAP 132±8ms vs. INAP 110±9ms; p=0.144, Fig.2). Stepwise increases of CPAP-application up until 12 mbar did neither result in changes of RA- nor CS-AERP. Only CPAP-application at 16 mbar (CPAP16) resulted in transiently shortened CS-AERP (CPAP-baseline 140±6ms versus CPAP16 115±10ms; p=0.0081, Fig.2.), but not RA-AERPs (p=0.31, Fig.1.). Conclusion While simulation of obstructive respiratory events by INAP were reproducibly associated with a predominantly right atrial shortening of refractoriness, high-pressure CPAP-application of 16 mbar was associated with an isolated moderate shortening of left atrial refractoriness. These findings may have important implications for CPAP treatment in patients with AF, which should be considered in the design of future clinical studies.

Pharmacological inhibition of SK-channels with AP14145 prevents atrial arrhythmogenic changes in a porcine model for obstructive respiratory events

Abstract Funding Acknowledgements Type of funding sources: Foundation. Main funding source(s): This work was supported by the Novo Nordisk Foundation (Tandem Programme; #31634). Background Obstructive sleep apnea (OSA) creates a complex substrate for atrial fibrillation (AF), which is refractory to many clinically available pharmacological interventions. Purpose To investigate atrial antiarrhythmogenic properties and ventricular electrophysiological safety of small-conductance Ca2+ -activated K+ (SK)- channel inhibition in a porcine model for obstructive respiratory events. Methods In spontaneously breathing pigs, obstructive respiratory events were simulated by intermittent negative upper airway pressure (INAP) applied via a pressure device connected to the intubation tube. INAP was applied for 75 seconds, every 10 minutes, three times before and three times during infusion of the SK-channel inhibitor AP14145. Atrial effective refractory periods (AERP) were acquired before (Pre-INAP), during (INAP) and after (Post-) INAP. AF-inducibility was determined by a S1S2 atrial pacing protocol. For the purpose of drug safety, ventricular arrhythmicity was evaluated by heart rate adjusted QT-interval duration (QT-paced) and electromechanical window (EMW) calculation. Results During vehicle infusion, INAP transiently shortened AERP (Pre-INAP: 135±10 ms vs. Post-INAP 101±11 ms; p=0.008) and increased AF-inducibility. QT-paced prolonged during INAP (Pre-INAP 270±7 ms vs. INAP 275±7 ms; p=0.04) and EMW shortened progressively throughout INAP and Post-INAP (Pre-INAP 80±4 ms; INAP 59±6 ms, Post-INAP 46±10 ms). AP14145 prolonged baseline AERP, partially prevented INAP-induced AERP-shortening and reduced AF-susceptibility. AP14145 did neither alter QT-paced (Pre-AP14145 270±7 ms vs. AP14145 268±6 ms, p=0.83) nor INAP-induced QT-paced prolongation, but blunted Post-INAP associated EMW-shortening. Conclusion In a pig model for obstructive respiratory events, the SK-channel-inhibitor AP14145 prevented INAP-associated AERP-shortening and AF-susceptibility without impairing ventricular electrophysiology. Hence, SK-channels may represent a promising target for OSA-related AF.

The Effect of 12-Week Treatment with Intermittent Negative Pressure on Blood Flow Velocity and Flowmotion, Measured with a Novel Doppler Device (Earlybird). Secondary Outcomes from a Randomized Sham-Controlled Trial in Patients with Peripheral Arterial Disease

Treatment with intermittent negative pressure (INP) is proposed as an adjunct to standard care in patients with peripheral arterial disease (PAD). The aims of this study were to evaluate the applicability of a novel ultrasound Dopplerdevice (earlybird) to assess blood flow characteristics in patients with PAD during a treatment session with INP, and whether certain flowproperties could determine who could benefit from INP treatment. Secondary outcomes of data from a randomized sham-controlled trial were explored. Patients were randomized to 12weeks of treatment with 40mm Hg or 10mm Hg INP, for one hour twice daily. Earlybird blood flow velocity recordings were made before and after the 12-week treatmentperiod and consists of a 5-min recording in rest, 3-min during INP treatment and 5-min recording after ended INP test-treatment. Mean blood flow velocity (vmean), relative changes in flow and frequency spectrum by Fourier-transform of the respective bandwidths of endothelial, sympathetic, and myogenic functions, were analyzed for the different series of blood flow measurements. In total, 62 patients were eligible for analysis, where 32 patients were treated with 40mm Hg INP. The acquired recordings were of good quality and were used for descriptive analyses of flow characteristics. An immediate increase in vmean during the negative pressure periods of the INP test-treatment was observed in the 40mm Hg INP treatment group at both pre- and post-test. There was a significant difference between the treatment groups, with a difference between the medians of 13.7 (P<0.001) at pre-test and 10.7 (P<0.001) at posttest. This finding was confirmed with spectrum analysis by Fourier-transform of the bandwidth corresponding to INP treatment. The change in amplitude corresponding to myogenic function after 12-weeks of treatment, was significantly different in favor of the 40mm Hg INP treatment group. We were not able to detect the specific flow characteristics indicating who would benefit INP-treatment. Earlybird is an applicable tool for assessing blood flow velocity in patients with PAD. Analysis of the flow velocity recordings shows that INP induces an immediate increase in blood flow velocities during INP. The positive effects of INP may be attributed to recruitment of arterioles, and thereby, increasing blood flow. In these analyses, no flow characteristics were determined which could predict who would benefit INP treatment.

Indigenously Prepared Intermittent Negative Pressure Wound Dressing: Effective and Economic in Indian Scenario

Introduction: Intermittent negative pressure wound treatment (INPWT) is a proven way to accelerate wound healing by increasing blood flow, promoting angiogenesis and suction removal of matrix metalloproteinases. The purpose of the study was to evaluate the use of INPWT in pressure sores. In our study, we have used very low-cost locally available material for INPWT in place of commercially available costly vacuum-assisted closure (VAC) machine and dressing. Materials and Methods: This was a prospective study conducted in the department of plastic and reconstruction surgery and physical medicine and rehabilitation at a tertiary level facility. Eighty patients of spinal cord injury with 70% of ASIA Grade A and B with pressure ulcer most commonly at sacral and ischial regions with National Pressure Ulcer Advisory Panel Grade 3 and Grade 4 pressure sore were treated. Patients enrolled included 57 males and 23 females. The study employed locally manufactured low-cost materials such as foam, Ioban tape, Room Vac drain and suction machine (easily and locally available at any primary, secondary as well as tertiary healthcare centre) for INPWT in patients with pressure sores. Dressing was changed every 4th day till desired granulation tissue was formed. Results: Out of patients who were treated with INPWT, 30% achieved direct closure, 49% required split skin grafting and 21% required reconstruction by local flaps. Commercial available VAC machines available in the market cost around 300,000–500,000 INR, and the cost of single dressing is around 7000–15,000 INR. This may not be economically feasible, especially in patients having large wounds which require multiple applications of these dressings with our indigenous dressing; there is a 95%–98% decrease in pricing of dressing. Conclusion: The study concluded that low-cost indigenously prepared INPWT dressing produced effective results at minimum cost that were at par with commercially available costly VAC dressing. This low-cost indigenously prepared INPWT can be groundbreaking in treatment of patients with pressure ulcer in developing country like India in both rural and urban settings.

Pharmacological inhibition of acetylcholine-regulated potassium current (I K,ACh) prevents atrial arrhythmogenic changes in a rat model of repetitive obstructive respiratory events.

BackgroundIn obstructive sleep apnea (OSA), intermittent hypoxemia and intrathoracic pressure fluctuations may increase atrial fibrillation (AF) susceptibility by cholinergic activation.ObjectiveTo investigate short-term atrial electrophysiological consequences of obstructive respiratory events, simulated by intermittent negative upper airway pressure (INAP), and the role of atrial acetylcholine-regulated potassium current (IK,ACh) activated by the M2 receptor.MethodsIn sedated (2% isoflurane), spontaneously breathing rats, INAP was applied noninvasively by a negative pressure device for 1 minute, followed by a resting period of 4 minutes. INAP was applied repeatedly throughout 70 minutes, followed by a 2-hour recovery period. Atrial effective refractory period (AERP) and AF inducibility were determined throughout the protocol. To study INAP-induced IK,ACh activation, protein levels of protein kinase C (PKCƐ) were determined in membrane and cytosolic fractions of left atrial (LA) tissue by Western blotting. Moreover, an IK,ACh inhibitor (XAF-1407: 1 mg/kg) and a muscarinic receptor inhibitor (atropine: 1 μg/kg) were investigated.ResultsIn vehicle-treated rats, repetitive INAP shortened AERP (37 ± 3 ms vs baseline 44 ± 3 ms; P = .001) and increased LA membrane PKCƐ content relative to cytosolic levels. Upon INAP recovery, ratio of PKCƐ membrane to cytosol content normalized and INAP-induced AERP shortening reversed. Both XAF-1407 and atropine increased baseline AERP (control vs XAF-1407: 61 ± 4 ms; P > .001 and control vs atropine: 58 ± 3 ms; P = .011) and abolished INAP-associated AERP shortening.ConclusionShort-term simulated OSA is associated with a progressive, but transient, AERP shortening and a PKCƐ translocation to LA membrane. Pharmacological IK,ACh and muscarinic receptor inhibition prevented transient INAP-induced AERP shortening, suggesting an involvement of IK,ACh in the transient arrhythmogenic AF substrate in OSA.

Application effects of three ventilation methods on swine in winter

AbstractAn appropriate housing ventilation system is needed to ensure livestock and poultry health. In this study, 315 90‐d‐old Duroc × Landrace × Yorkshire (DLY) crossbred swine were distributed to three experimental swine houses. Each house had 105 swine, with 15 swine in each pen (including seven males and eight females). The ventilation systems for three houses were naturally ventilated, intermittent negative pressure longitudinal mechanical ventilation, and tunnel ventilation. The experiment was monitored for 28 consecutive days. The average temperature and relative humidity of the tunnel‐ventilated swine house were 19.22 °C and 60.79%, respectively, which were higher than other two swine houses (P &lt; .05). The NH3 and CO2 concentrations in the tunnel‐ventilated swine house were lower than the other systems (P &lt; .05). The average daily growth of swine in the tunnel ventilated was 14.9% higher (P &lt; .05) than that in the natural ventilation. The feed/gain (F/G) ratio was 11.44% higher (P &lt; .05) and abnormal behavior was lower in the tunnel ventilated swine house than those in the naturally ventilated swine house. Our results indicate that the tunnel ventilation is the best ventilation system for swine houses during the winter in northern China.

The efficacy of intermittent pneumatic compression and negative pressure therapy on muscle function, soreness and serum indices of muscle damage: a randomized controlled trial

BackgroundThe study aimed to assess whether intermittent pneumatic compression (IPC) and intermittent negative pressure (INP) would attenuate the muscle damaging effects of eccentric exercise.MethodsForty-five healthy males were recruited. Immediately post, 24 and 48 h post eccentric exercise consisting of 100 drop jumps, volunteers randomly received 30-min sessions of intermittent pneumatic compression (IPC, n = 15) or intermittent negative pressure (INP, n = 15), or sham microcurrent (PT, n = 15). Creatine kinase (CK), lactate dehydrogenase (LDH), isokinetic muscle strength, soreness and active flexion of the knee joint were measured after every therapy session.ResultsNo significant intergroup differences were observed in biochemical or functional measurements. However, there was an increase in muscle soreness (P < 0.05), CK and LDH activity (P < 0.05), and a reduction in muscle strength (P < 0.05) and range of active knee flexion (P < 0.05).ConclusionsThe prescription of IPC and INP did not attenuate the reduction of markers to muscle function or pain perception up to 48 h after muscle damaging exercise. Future research should focus on the potential impact of treatment frequency and duration on muscle recovery.Trial registration The study was retrospectively registered in the Australian New Zealand Clinical Trials Registry (ANZCTR); The trial registration number: ACTRN12621001294842; date of registration: 24/09/2021.

Novel Intraoral Negative Airway Pressure in Drug-Induced Sleep Endoscopy with Target-Controlled Infusion.

BackgroundIn intermittent negative airway pressure (iNAP) therapy, soft tissues are reshaped into a forward-resting position, thus reducing airway obstruction during sleep. This study investigated the effect of iNAP therapy that was administered during drug-induced sleep endoscopy with target-controlled infusion (TCI-DISE) in patients with obstructive sleep apnea (OSA) intolerant of continuous positive airway pressure (CPAP) therapy.MethodsThis prospective case series study included 92 patients with polysomnography (PSG)-confirmed OSA who underwent TCI-DISE with iNAP from January 2018 to February 2020 at a tertiary referral hospital. Upper airway obstruction was evaluated and scored using the velum, oropharynx, tongue base, and epiglottis (VOTE) classification. Obstruction severity was assessed multiple times with the patient in the supine position with or without lateral rotation of the head and the application of iNAP therapy, respectively.ResultsAfter the application of iNAP therapy in the supine position, obstruction severity decreased significantly: from complete or partial obstruction to partial or no obstruction in 37, 12, and 36 patients (40.2%, 13%, and 39%, respectively) with velar obstruction, oropharyngeal, and tongue base obstruction, respectively. After simultaneously applying iNAP therapy with head rotation, obstruction severity decreased in 47, 43, and 19 patients (51%, 47%, and 21%, respectively) with velar, tongue base, and epiglottic obstruction, respectively.ConclusionIn TCI-DISE, we found that iNAP therapy relieved velar, oropharyngeal, and tongue base obstruction in the supine position in some patients. Moreover, iNAP therapy can be combined with positional therapy to alleviate velar, tongue base, and epiglottic obstruction in some patients. TCI-DISE can also be used to screen the possible responders for iNAP therapy because it is less time consuming than PSG.