Dendritic epidermal T cell hydrogel induces the polarization of M2 macrophages to promote the healing of deep tissue pressure injury.

Dendritic epidermal T cells (DETCs) have been shown to promote wound healing. However, the mechanisms involved need to be better understood. In the present study, we investigated the role and mechanism of DETCs in deep tissue pressure injury (DTPI). We established the DTPI model using C57BL/6 mice. Then, DTPI was evaluated and analyzed by histological staining, immunohistochemistry, real-time PCR, Western blotting, and flow cytometry in different treatment groups (DETCs, DETCs/gel, Matrigel, Saline, and Normal group). The results showed that insulin-like growth factor 1 and vascular endothelial growth factor-A expression increased after local DETCs and DETCs/gel implantation in DTPI on days 3 and 7. M1 (inducible nitric oxide synthas-marked) macrophages were predominant at 3 days after DTPI. At 7 days, M1 macrophages were decreased, and M2 (CD206-marked) macrophages were increased in the DETCs and DETCs/gel groups. In vitro, in the co-culture of DETCs and RAW264.7, CD206 expression was significantly increased in M2 macrophages. In addition, Interleukin-17A initially inhibited wound healing 1 day after injury. However, it promoted wound healing at 7, 14, and 21 days after treatment with DETCs and DETCs/gel, respectively. In conclusion, our data suggest that exogenous DETCs improve DTPI wound healing by regulating M1 to M2 macrophage polarization.

Tissue Pressure Changes and Implications on Dressing Selection when utilising Negative Pressure Wound Therapy on an Ex Vivo Porcine Model.

Negative Pressure Wound Therapy (NPWT) is broadly used in surgical wound management and more recently burn care; however, the tissue pressure changes and best dressing application technique remains unknown. This study was done to help understand the tissue pressure changes beneath negative pressure when varying the delivered pressures, dressing thickness and distribution of dressings. This study was done in 2021 at a quaternary paediatric burns hospital. Utilising a cadaveric porcine model, an intracranial pressure monitor and transducer were used to assess pressure. The transducer was placed on the epidermis or inserted under ultrasound guidance via cannulation to the dermis, subcutaneous or muscular layer. Mepitel™, ACTICOAT™, varying layers of Kerlix™ (10, 20 or 30 layers) and NPWT were then applied either circumferentially or non-circumferentially. Each set of results is indicative of the intracranial pressure probe reading when NPWT was delivered at -40, -60, -80, -100 and -120 mmHg. The median and interquartile pressure recordings were epidermis: -42 (-42.5 - -41), -60.5 (-62.5 - -60), -80.5 (-82 - -80), - 99 (-99 - -98)mmHg (p < 0.001); dermis: 1 (0 - 2), 2 (1 - 3.5), 3 (2 - 5.5), 4 (3 - 7), 5.5 (4 - 7.5)mmHg (p < 0.001) (the increase in pressure was less when circumferential dressings (p < 0.001) or more layers of Kerlix were applied (p < 0.001)); subcutis: 1.5 (-4.5-1), -2.5 (-7.5 - 1.5), -3.5 (-11 - 1.5), -5 (-14 - 1.5) and -6 (-16 - 2)mmHg (p = 006) (the decrease in pressure was less with increased layers of Kerlix (0.047) and muscular: 0 (-0.5 - 0), 0 (-1 - 0.5), 0 (-1 - 1), 0 0 (-1 - 1), 00 (-1.5 - 1)mmHg (p = 0.55). These data suggest negative pressure paradoxically exerts a positive pressure on the dermis. Circumferential and multi-layer dressings reduce this positive pressure. This knowledge has impacted our burn negative pressure wound therapy dressing selection. The limitation of this study is the cadaveric model, a live model is suggested for future studies.

dECM restores macrophage immune homeostasis and alleviates iron overload to promote DTPI healing.

Due to its highly insidious and rapid progression, deep tissue pressure injury (DTPI) is a clinical challenge. Our previous study found that DTPI may be a skeletal muscle injury dominated by macrophage immune dysfunction due to excessive iron accumulation. Decellularized extracellular matrix (dECM) hydrogel promotes skeletal muscle injury repair. However, its role in polarizing macrophages and regulating iron metabolism in DTPI remains unclear. Here, porcine dECM hydrogel was prepared, and its therapeutic function and mechanism in repairing DTPI were investigated. The stimulus of dECM hydrogel toward RAW264.7 cells resulted in a significantly higher percentage of CD206+ macrophages and notably decreased intracellular divalent iron levels. In mice DTPI model, dECM hydrogel treatment promoted M1 to M2 macrophage conversion, improved iron metabolism and reduced oxidative stress in the early stage of DTPI. In the remodeling phase, the dECM hydrogel remarkably enhanced revascularization and accelerated skeletal muscle repair. Furthermore, the immunomodulation of dECM hydrogels in vivo was mainly involved in the P13k/Akt signaling pathway, as revealed by GO and KEGG pathway analysis, which may ameliorate the iron deposition and promote the healing of DTPI. Our findings indicate that dECM hydrogel is promising in skeletal muscle repair, inflammation resolution and tissue injury healing by effectively restoring macrophage immune homeostasis and normalizing iron metabolism.

Real-Time Continuous Monitoring of Oral Soft Tissue Pressure with a Wireless Mouthguard Device for Assessing Tongue Thrusting Habits.

In orthodontics, understanding the pressure of oral soft tissues on teeth is important to elucidate the cause and establish treatment methods. We developed a small wireless mouthguard (MG)-type device that continuously and unrestrainedly measures pressure, which had previously been unachieved, and evaluated its feasibility in human subjects. First, the optimal device components were considered. Next, the devices were compared with wired-type systems. Subsequently, the devices were fabricated for human testing to measure tongue pressure during swallowing. The highest sensitivity (51-510 g/cm2) with minimum error (CV < 5%) was obtained using an MG device with polyethylene terephthalate glycol and ethylene vinyl acetate for the lower and upper layers, respectively, and with a 4 mm PMMA plate. A high correlation coefficient (0.969) was observed between the wired and wireless devices. In the measurements of tongue pressure on teeth during swallowing, 132.14 ± 21.37 g/cm2 for normal and 201.17 ± 38.12 g/cm2 for simulated tongue thrust were found to be significantly different using a t-test (n = 50, p = 6.2 × 10-19), which is consistent with the results of a previous study. This device can contribute to assessing tongue thrusting habits. In the future, this device is expected to measure changes in the pressure exerted on teeth during daily life.

Rhinorrhea and increased chloride secretion through the CFTR chloride channel-a systematic review.

PURPOSE: Allergic and non-allergic rhinorrhea in the forms of acute or chronic rhinosinusitis can mean a watery nasal discharge that is disabling. Primary objective was to review the evidence supporting the hypothesis that rhinorrhea is due to increased chloride secretion through the CFTR chloride channel. METHODS: The structure of the evidence review followed the EQUATOR Reporting Guidelines. Databases searched from inception to February 2022 included Pubmed, EMBASE and the Cochrane library using keywords "Rhinorrhea", "chloride", "chloride channel", "CFTR" and "randomized controlled trial". Quality assessment was according to the Oxford Centre for Evidence-based Medicine. RESULTS: 49 articles were included. They included randomized controlled trials out of which subsets of data with the outcome of rhinorrhea on 6038 participants were analysed and in vitro and animal studies. The review revealed that drugs, which activate CFTR are associated with rhinorrhea. Viruses, which cause rhinorrhea like rhinovirus were found to activate CFTR. The chloride concentration in nasal fluid showed an increase in patients with viral upper respiratory tract infection. Increased hydrostatic tissue pressure, which is an activator of CFTR was observed in allergic upper airway inflammation. In this condition exhaled breath condensate chlorine concentration was found to be significantly increased. Drugs, which can reduce CFTR function including steroids, anti-histamines, sympathomimetic and anticholinergic drugs reduced rhinorrhea in randomized controlled trials. CONCLUSIONS: A model of CFTR activation-mediated rhinorrhea explains the effectiveness of anticholinergic, sympathomimetic, anti-histamine and steroid drugs in reducing rhinorrhea and opens up avenues for further improvement of treatment by already known specific CFTR inhibitors.

Acute Extremity Compartment Syndrome and (Regional): Anesthesia: The Monster Under the Bed.

Acute compartment syndrome (ACS) is a potential orthopedic emergency that leads, without prompt diagnosis and immediate treatment with surgical fasciotomy, to permanent disability. The role of regional anesthesia (RA) for analgesia in patients at risk for ACS remains unjustifiably controversial. This critical review aims to improve the perception of the published literature to answer the question, whether RA techniques actually delay or may even help to hasten the diagnosis of ACS. According to literature, peripheral RA alone does not delay ACS diagnosis and surgical treatment. Only in 4 clinical cases, epidural analgesia was associated with delayed ACS diagnosis.

Extracts of Portulaca oleracea promote wound healing by enhancing angiology regeneration and inhibiting iron accumulation in mice.

Objective: To investigate the role of Portulaca oleracea (POL) in promoting revascularization and re-epithelization as well as inhibiting iron aggregation and inflammation of deep tissue pressure injury (DTPI). Methods: The hydroalcoholic extract of POL (P) and aqueous phase fraction of POL (PD) were prepared based on maceration and liquid-liquid extraction. The number of new blood vessels and VEGF-A expression level were assessed using H&E stain and Western blot on injured muscle to examine the role of POL different extracts in vascularization. The iron distribution and total elemental iron of injured muscle were detected using laser ablation inductively coupled plasma mass spectrometry (ICP-MS) and Perls' staining to determine whether POL extracts can inhibit the iron accumulation. Besides, the ability of POL extracts to promote wound healing by combining re-epithelization time, inflammation degree and collagen deposition area were comprehensively evaluated. Results: In vitro, we observed a significant increase in HUVEC cell viability, migration rate and the number of the tube after P and PD treatment (P < 0.05). In vivo, administration of P and PD impacted vascularization and iron accumulation on injured tissue, evident from more new blood vessels, higher expression of VEGF-A and decreased muscle iron concentration of treatment groups compared with no-treatment groups (P < 0.05). Besides, shorter re-epithelization time, reduced inflammatory infiltration and distinct collagen deposition were associated with administration of P and PD (P < 0.05). Conclusion: POL extract administration groups have high-quality wound healing, which is associated with increased new blood vessels, collagen deposition and re-epithelization, along with decreased iron accumulation and inflammatory infiltration. Our results suggest that that POL extract is beneficial to repair injured muscle after ischemia-reperfusion, highlighting the potential of POL in the DTPI treatment.

Novel tissue-pressure sensing technology using a wide-band dielectric imaging system: An in vivo study.

BACKGROUND: A novel dielectric wide-band imaging system with tissue pressure (TP) technology provides real-time contact force (CF) monitoring using non-CF catheters. This study sought to investigate the feasibility, safety, and efficacy of ablation with TP technology. METHODS: Eighty-five patients with supraventricular tachycardia (SVT) were ablated with real-time monitoring of CF by TP technology and compared with 85 patients who underwent ablation with a conventional non-TP approach. Baseline characteristics, procedural data, and TP data were analyzed in the study. Ablation applications in the TP group were then subdivided into good contact and poor contact groups according to the TP level for analysis. RESULTS: The TP group had a significantly shorter procedural time (16.2 ±â€¯6.9 min vs. 19.9 ±â€¯10.0 min, p = 0.033), shorter ablation time (334.6 ±â€¯166.9 s vs. 391.3 ±â€¯195.7 s, p = 0.049), and fewer mean numbers of radiofrequency catheter ablation (RFCA) deliveries (6.2 ±â€¯3.2 vs. 7.6 ±â€¯5.2, p = 0.047) than the non-TP group. The achieved average percentage of TP >3 g was significantly higher in the good-contact group (97.94% vs. 15.48%, p < 0.001). The median impedance decreases during RFCA in the good contact group and poor contact group were 4.10 (0.30-6.88) Ω and 2.60 (-0.05-4.98) Ω at 10 s, 4.45 (0.58-8.25) Ω and 2.88 (0.23-5.70) Ω at 20 s, and 4.67 (1.95-9.08) Ω and 2.97 (-0.26-6.33) Ω at 30 s, respectively (p < 0.05 for comparisons between categories). All patients achieved acute success, and no complications were observed. Two patients in the TP group and one patient in the non-TP group experienced recurrence during follow-up. CONCLUSION: TP-technology guided ablation of SVT is feasible, efficient, and safe.

Hard Tissue Volume Stability Effect beyond the Bony Envelope of a Three-Dimensional Preformed Titanium Mesh with Two Different Collagen Barrier Membranes on Peri-Implant Dehiscence Defects in the Anterior Maxilla: A Randomized Clinical Trial.

This single-blinded, randomized, controlled study aimed to clinically and radiographically evaluate hard tissue volume stability beyond the bony envelope using three-dimensional preformed titanium mesh (3D-PFTM) for peri-implant dehiscence defects in the anterior maxilla. A total of 28 patients who wished to undergo implant surgery combined with guided bone regeneration (GBR) after extraction of a single maxillary anterior tooth were randomly assigned to two groups depending on the type of collagen membrane used, additionally with the 3D-PFTM-test (n = 14, cross-linked collagen membrane; CCM) and control (n = 14, non-cross-linked collagen membrane; NCCM) groups. Each implant was evaluated radiographically using CBCT at baseline, immediately after surgery, and at 6 months postoperatively. The relative position and distances from the bony envelope to the outlines of the augmented ridge were further determined immediately after GBR and 6 months after healing. At the platform level, the mean horizontal hard tissue gain (HG) at all the sites was 2.35 ± 0.68 mm at 6 months postoperatively. The mean HG rate was 84.25% ± 14.19% in the CCM group and 82.56% ± 13.04% in the NCCM group, but the difference was not significant between the groups. In all cases, HG was maintained beyond the bony envelope even after 6 months of GBR. This study suggests that 3D-PFTM should be considered a valuable option for GBR for peri-implant dehiscence defects in the anterior maxilla. In addition, 3D-PFTM may confer predictable hard tissue volume stability even after the healing period of hard tissue augmented outside the bony envelope by GBR.

Long term functional outcomes after minimally invasive surgical decompression in upper limb chronic exertional compartment syndrome in 30 patients.

Chronic exertional compartment syndrome (CECS) of the upper limbs is less well known than its equivalent in the lower limbs, thus its diagnosis is often delayed. Our goals were to evaluate the impact of CECS on activities of daily living and work-related activities and to report the functional outcomes after minimally invasive fasciotomy. This was a retrospective study of patients with CECS of the upper limb who were operated at two hospitals between 2008 and 2019. Thirty patients were reviewed an average of 5 years after minimally invasive fasciotomy: 26 had CECS of the forearm, 3 of the thenar compartment and 1 of the first interosseous compartment. For the evaluation, patients were asked to assess their pain on a visual analog scale (VAS), complete the QuickDASH questionnaire and rate their satisfaction with the outcome. Preoperative pain on the VAS was 7.45/10 with a negative impact on activities of daily living in 97% of patients, and on work-related activities in 77% of patients with 17% requiring a career change. The mean time to surgical treatment was 5 years. The mean QuickDASH at the final assessment was 6.0 (0-31.8) with a significant decrease in pain on VAS of 1.9/10 (p < 0.01). Seventy-seven percent of patients had very good results while 13% had good results. Full healing was achieved in 63% of patients and physical performance improved in 50%. Seventy-seven percent of patients were either satisfied or very satisfied with the outcome. One patient had a recurrence requiring surgical revision. CECS affects athletes of all levels and impacts both activities of daily living and work-related activities. We need to greatly expand our education and prevention efforts for CECS. Mini-open fasciotomy yields good results.

Deep Tissue Pressure Injuries: Identification, Treatment, and Outcomes Among Critical Care Patients.

Deep tissue pressure injury (DTPI) is a serious form of pressure injuries. The condition remains invisible for up to 48 hours and then progresses rapidly to full-thickness skin and soft tissue loss. Many other conditions that lead to purple skin can be misidentified as DTPI, making the diagnosis difficult at times. A thorough history exploring exposure to pressure is imperative.

Evaluation of infrared technology to detect category I and suspected deep tissue injury in hospitalised patients.

OBJECTIVE: To evaluate the use of an infrared thermography device in assessing skin temperature among category I pressure ulcer (PU) and/or suspected deep tissue injuries (SDTI) with intact skin. METHODS: An observational cross-sectional study design was used. Adult inpatients (cases) who had a category I PU or suspected deep tissue injury (skin intact) on the sacral or heel during the study period (March to April 2018) were recruited. Patients without a PU were also recruited to act as control. Thermal images of the patient's PU site and non-PU site were taken within 24 hours of PU occurrence. Thermal images of the control patients (no PU) were also taken. Each PU case was matched to three control patients in terms of age, gender, race and anatomical sites. All thermal images were taken using a portable CAT S60 Thermal Imaging Rugged Smartphone (Caterpillar Inc., US) that provided readings of the skin temperature in degrees Celsius. RESULTS: A total of 17 cases and 51 controls were recruited. Among the cases, the mean difference in skin temperature between the PU site (mean: 31.14°C; standard deviation [SD]: 1.54) and control site within the cases (mean: 28.93°C; SD: 3.47) was significant (difference: 2.21±3.66°C; p=0·024). When comparing between all cases and controls, the mean temperature difference was non-significant. When comparing between the category I PU and suspected deep pressure injury cases, the mean difference was also non-significant. CONCLUSION: Using infrared thermography technology at the bedside to measure skin temperature will support the clinical diagnosis of patients with skin types I to III. However, there is a need for a more accurate and objective measurement to identify and diagnose early category I PU or suspected deep tissue injury in adult patients with darker skin types 4 and above, enabling early initiation of preventive measures in the hospital acute care setting.

Hard tissue volume stability of guided bone regeneration during the healing stage in the anterior maxilla: A clinical and radiographic study.

BACKGROUND: Guided bone regeneration (GBR) is currently the most widely used technique to reconstruct localized peri-implant bone defects. OBJECTIVES: To evaluate hard tissue volume stability during the healing stage of GBR with particulate bone graft and resorbable collagen membrane. MATERIALS AND METHODS: Twenty-eight patients who were missing a single maxillary incisor and required implant placement combined with GBR were randomly assigned to 2 groups: submerged (n = 14) and transmucosal (n = 14) healing groups. Cone-beam computed tomography (CBCT) was performed before, immediately after and 6 months post-surgery. The 3 sets of CBCT data were three-dimensionally reconstructed and superimposed. Horizontal hard tissue alterations at different vertical levels were recorded. The relative position and distances from the boundary line of the bony defect envelope to the outlines of the augmented ridge were determined immediately post-augmentation and 6 months after healing. RESULTS: Augmented ridge underwent horizontal volume reduction during the healing period. Vertical levels (P = .000) rather than healing strategies (submerged or transmucosal) (P = .182) had statistically significant impacts on the reduction width. The boundary line of the ridge defect envelope located within the bony profile immediately after surgery, but outside of the bony profile after 6 months. CONCLUSIONS: GBR with resorbable membrane and particulate bovine bone would undergo horizontal volume reduction during the healing stage. New bone formation at the coronal site may only be predictable within the bony envelope.

Elastographic Assessment of Xenograft Pancreatic Tumors.

High tissue pressures prevent chemotherapeutics from reaching the parenchyma of pancreatic ductal adenocarcinoma, which makes it difficult to treat this aggressive disease. Researchers currently use invasive probes to monitor the effectiveness of pressure-reducing therapies, but this practice introduces additional complications. Here, we hypothesize that Young's modulus is a good surrogate for tissue pressure because collagen density and hyaluoronic acid, the key features of the tumor microenvironment responsible for high tissue pressures, also affect modulus elastograms. To corroborate this hypothesis, we used model-based quasi-static elastography to assess how the Young's modulus of naturally occurring AsPc-1 pancreatic tumors varies with collagen density and hyaluoronic acid concentration. We observed that Young's moduli of orthotopically grown xenograft tumors were 6 kPa (p < 0.05) higher than that of their subcutaneously grown counterparts. We also observed a strong correlation between Young's modulus and regions within the tumors with high collagen (R2 ≈ 0.8) and hyaluoronic acid (R2 ≈ 0.6) densities. These preliminary results indicate that hyaluronic acid and collagen density, features of the pancreatic ductal adenocarcinoma tumor microenvironment responsible for high tissue pressure, influence Young's modulus.

Feedback modulation of surrounding pressure determines the onset of negative effort dependence in a collapsible tube bench model of the pharyngeal airway.

Negative effort dependence (NED), decreased airflow despite increased driving pressure, has been proposed as a specific obstructive sleep apnea (OSA) phenotypic characteristic. We examined conditions under which NED occurs in a collapsible tube, pharyngeal airway bench model with the chamber enclosed, focusing on relationships with surrounding pressure levels and longitudinal strain. Using a vacuum source, graded airflows (V̇; 0-5 l/s) were generated through a thin-walled latex tube enclosed within a rigid, cylindrical chamber, sealed with initial chamber pressures (Pci) of 0-5 cmH2O (separate runs), or opened to the atmosphere. Upstream minus downstream pressure (Pu - Pd), maximum airflow (V̇max), and chamber pressure (Pc) were measured at 0-50% longitudinal strain. NED occurred across the range of Pci and strains studied but was most pronounced for the chamber open condition. With a sealed chamber, V̇ increased and Pc decreased with increasing Pu - Pd until the onset of NED at V̇max and a Pc value that was designated as critical (Pcc). Pcc was lowest (-17 cmH20) and V̇max was highest (~5 l/s) with chamber sealed: Pci = 0 cmH2O and 12.5 to 25% strain. We conclude that for our collapsible tube model, the achievable V̇max before the onset of NED depends on both the initial conditions (Pci and strain) and the dynamics of feedback between driving pressure and chamber pressure (chamber sealed vs. open). NED-based phenotypic analyses for OSA may need to focus on potential feedback control mechanisms (eg lung volume change, muscle activity) that may link peripharyngeal tissue pressure levels to driving pressures for airflow.NEW & NOTEWORTHY A collapsible tube, pharyngeal airway bench model was used to study the role of surrounding pressure and longitudinal wall strain at the onset of negative effort dependence (NED). NED occurred to varying degrees across all conditions tested, but maximum airflow was achieved with 1) low initial surrounding pressure, 2) a feedback mechanism between surrounding pressure and driving pressure; and 3) a moderate amount of strain applied. Potential impacts on OSA phenotypic analyses are discussed.

Demyelinating diseases as a result of cerebral edema?

Due to the elastic properties of the human organs, tissue edema causes an increased tissue pressure. This phenomenon leads to a reduction of blood circulation or ischemia, and thus leads to the hypothesis that tissue edema can be the cause of demyelinating lesions. Even though brain edema occurs in the whole brain, the authors assume that the characteristically focal appearance of demyelinated lesions, for instance of multiple sclerosis plaques, are attributable to anatomical and structural characteristics of the brain. In an experimental section, a balloon inserted into the brain and other organs removed during autopsies produces an increased tissue pressure. This model shows tissue pressure in the vicinity of the balloon up to 80mmHg. The height of the produced pressure varies in different organs and special regions of the brain. The verified pressures in the pons cerebri show that stretched myelinated fiber bundles in outer regions can induce strong pressures in enclosed edematous tissue, as seen in central pontine myelinolysis. The presented experimental results support the hypothesis that demyelinated lesions, as seen in multiple sclerosis, may be caused by increased tissue pressure, or respectively, brain edema.

[Diagnostics and treatment decisions in acute compartment syndrome. Results of a survey in German hospitals]. / Diagnostik und Therapieentscheidung beim akuten Kompartmentsyndrom. Ergebnisse einer Umfrage in deutschen Kliniken.

BACKGROUND AND OBJECTIVES: The presented survey was intended to evaluate whether a standardization of diagnostics and therapy for acute compartment syndrome has been achieved. MATERIALS AND METHODS: University hospitals, academic teaching hospitals, and county hospitals in Germany were included. RESULTS: A total of 38% (n=120) of all contacted hospitals participated in this study with questions mainly answered by consulting physicians (68%). In general the importance of the clinical examination was considered as being more important than other diagnostic measures. In cases where further diagnostics were necessary, the intramuscular pressure measurement was used most frequently. Of the participants 50% performed surgical fasciotomy based on the clinical examination in combination with the intramuscular pressure measurement; however, there were considerable differences between the participating hospitals with respect to the anatomical position of intramuscular measurements, the limiting value of the intramuscular pressure and the surgical technique for performing fasciotomy. CONCLUSION: According to the presented analysis the diagnosis and indications for surgical treatment in patients developing an acute compartment syndrome do not seem to be sufficiently clarified. The establishment of unified treatment guidelines could help to reduce the number of delayed diagnoses of compartment syndrome.

Submental negative pressure application decreases collapsibility of the passive pharyngeal airway in nonobese women.

The pharyngeal airway is surrounded by soft tissues that are also enclosed by bony structures such as the mandible, maxilla, and cervical spine. The passive pharyngeal airway is therefore structurally analogous to a collapsible tube within a rigid box. Cross-sectional area of the tube is determined by transmural pressure, the pressure difference between intraluminal and extraluminal pressures. Due to a lack of knowledge on the influence of extraluminal soft tissue pressure on the human pharyngeal airway patency, we hypothesized that application of negative external pressure to the submental region decreases collapsibility of the passive pharynx, and that obese individuals have less response to the intervention than nonobese individuals. Static mechanical properties of the passive pharynx were compared before and during application of submental negative pressure in 10 obese and 10 nonobese adult women under general anesthesia and paralysis. Negative pressure was applied through use of a silicone collar covering the entire submental region and a vacuum pump. In nonobese subjects, application of submental negative pressure (-25 and -50 cmH2O) significantly decreased closing pressures at the retropalatal airway by 2.3 ± 3.2 cmH2O and 2.0 ± 3.0 cmH2O, respectively, and at the retroglossal airway by 2.9 ± 2.7 cmH2O and 3.7 ± 2.6 cmH2O, respectively, and the intervention stiffened the retroglossal pharyngeal airway wall. No significant mechanical changes were observed during application of submental negative pressure in obese subjects. Conclusively, application of submental negative pressure was found to decreases collapsibility of the passive pharyngeal airway in nonobese Japanese women.

Peripharyngeal tissue deformation, stress distributions, and hyoid bone movement in response to mandibular advancement.

Mandibular advancement (MA) increases upper airway (UA) patency and decreases collapsibility. Furthermore, MA displaces the hyoid bone in a cranial-anterior direction, which may contribute to MA-associated UA improvements via redistribution of peripharyngeal tissue stresses (extraluminal tissue pressure, ETP). In the present study, we examined effects of MA on ETP distributions, deformation of the peripharyngeal tissue surface (UA geometry), and hyoid bone position. We studied 13 supine, anesthetized, tracheostomized, spontaneously breathing adult male New Zealand White rabbits. Graded MA was applied from 0 to ∼4.5 mm. ETP was measured at six locations distributed throughout three UA regions: tongue, hyoid, and epiglottis. Axial computed tomography images of the UA (nasal choanae to glottis) were acquired and used to measure lumen geometry (UA length; regional cross-sectional area) and hyoid displacement. MA resulted in nonuniform decreases in ETP (greatest at tongue region), ranging from -0.11 (-0.15 to -0.06) to -0.82 (-1.09 to -0.54) cmH2O/mm MA [linear mixed-effects model slope (95% confidence interval)], across all sites. UA length decreased by -0.5 (-0.8 to -0.2) %/mm accompanied by nonuniform increases in cross-sectional area (greatest at hyoid region) ranging from 7.5 (3.6-11.4) to 18.7 (14.9-22.5) %/mm. The hyoid bone was displaced in a cranial-anterior direction by 0.42 (0.36-0.44) mm/mm MA. In summary, MA results in nonuniform changes in peripharyngeal tissue pressure distributions and lumen geometry. Displacement of the hyoid bone with MA may play a pivotal role in redistributing applied MA loads, thus modifying tissue stress/deformation distributions and determining resultant UA geometry outcomes.

[Intraoperative monitoring of oxygen tissue pressure: Applications in vascular neurosurgery]. / Monitorización intraoperatoria de la presión tisular de oxígeno: aplicaciones en neurocirugía vascular.

Ischemic lesions related to surgical procedures are a major cause of postoperative morbidity in patients with cerebral vascular disease. There are different systems of neuromonitoring to detect intraoperative ischemic events, including intraoperative monitoring of oxygen tissue pressure (PtiO2). The aim of this article was to describe, through the discussion of 4 cases, the usefulness of intraoperative PtiO2 monitoring during vascular neurosurgery. In presenting these cases, we demonstrate that monitoring PtiO2 is a reliable way to detect early ischemic events during surgical procedures. Continuous monitoring of PtiO2 in an area at risk allows the surgeon to resolve the cause of the ischemic event before it evolves to an established cerebral infarction.