Repetitive postoperative extubation failure due to dynamic inspiratory airway collapse concomitant with subglottic stenosis in a patient who previously underwent tracheostomy.

BACKGROUND: This report describes a case of dynamic inspiratory airway collapse concomitant with subglottic stenosis in a patient who previously underwent tracheostomy that led to repeated post-operative extubation failure. CASE PRESENTATION: A 43-year-old woman who had undergone tracheostomy 25 years previously was admitted to our intensive-care unit (ICU) after coronary artery bypass graft surgery. On postoperative day (POD) 0, she was extubated, but stridor was observed. We suspected upper airway obstruction and she was therefore reintubated. Before reintubation, urgent laryngotracheoscopy revealed dynamic inspiratory airway collapse and obstruction concomitant with subglottic stenosis. Preoperative computed tomography showed mild subglottic stenosis. Although intravenous corticosteroids were administered to prevent tracheal mucosal edema and a cuff leak test was confirmed to be negative, she developed extubation failure on POD6. On POD12, we performed tracheostomy to reduce mechanical irritation from the endotracheal tube. Mechanical ventilation was withdrawn and she discharged from the ICU. On POD33, her tracheostomy tube was removed and she remained clinically asymptomatic. CONCLUSIONS: We should be aware of the history of tracheostomy, especially at high tracheostomy sites, even in the absence of respiratory symptoms as risk factors for dynamic inspiratory airway collapse concomitant with subglottic stenosis contributing to repeated respiratory failure after extubation. J. Med. Invest. 70 : 301-305, February, 2023.

Interfacial Distribution of Nafion Ionomer Thin Films on Nitrogen-Modified Carbon Surfaces.

Chemically modified carbon supports for the cathode catalyst layers of polymer electrolyte fuel cells (PEFCs) show considerable promise for boosting the oxygen reduction reaction. This study evaluated the ionomer distribution of Nafion ionomer thin films on nitrogen (N)-modified carbon surfaces along their depth direction. Neutron reflectivity (NR) measurements performed using the double-contrast technique with H2O and D2O revealed that the introduction of N functional groups to carbon thin films promoted ionomer adsorption onto the surface under wet conditions (22 °C, 85% relative humidity). Molecular dynamics (MD) simulations conducted to verify the origin of the robust contact between the ionomer and N-modified carbon surface revealed an ionomer adsorption mechanism on the N-modified carbon surfaces, which involved Coulomb interactions between the positively charged carbon surface and the ionomer side chains with negatively charged sulfonic acid groups. The positive surface charge, which was determined using the contents of the N functional groups estimated by X-ray photoelectron spectroscopy, was found to be sufficient as an impetus for ionomer adsorption. This strategy involving NR measurements and MD simulations can provide insights into the solid-ionomer interfacial structures in a cathode catalyst layer and can therefore be extensively employed in studies on PEFCs.

The quality and quantity of sleep on dexmedetomidine during high-flow nasal cannula oxygen therapy in critically ill patients.

Purpose : High-flow nasal cannula oxygen therapy (HFNC) is a new type of non-invasive respiratory support for acute respiratory failure patients. However, patients receiving HFNC often develop sleep disturbances. We therefore examined whether dexmedetomidine could preserve the sleep characteristics in patients who underwent HFNC. Patients and Methods : This was a pilot, randomized controlled study. We assigned critically ill patients treated with HFNC to receive dexmedetomidine (0.2 to 0.7 µg / kg / h, DEX group) or not (non-DEX group) at night (9:00 p.m. to 6:00 a.m.). Polysomnograms were monitored during the study period. The primary outcomes were total sleep time (TST), sleep efficiency and duration of stage 2 non-rapid eye movement (stage N2) sleep. Results : Of the 28 patients who underwent randomization, 24 were included in the final analysis (12 patients per group). Dexmedetomidine increased the TST (369 min vs. 119 min, p = 0.024) and sleep efficiency (68% vs. 22%, P = 0.024). The duration of stage N2 was increased in the DEX group compared with the non-DEX group, but this finding did not reach statistical significance. The incidences of respiratory depression and hemodynamic instability were similar between the two groups. Conclusions : In critically ill patients who underwent HFNC, dexmedetomidine may optimize the sleep quantity without any adverse events. J. Med. Invest. 69 : 266-272, August, 2022.

Acquired laryngomalacia as a cause of post-extubation respiratory failure in patient with postoperative seizure and central pontine myelinolysis after craniotomy.

Background : Laryngomalacia is a congenital abnormality of the larynx that commonly occurs in children and rarely in adults. We report the first case of acquired laryngomalacia mainly due to postoperative seizure and central pontine myelinolysis after scheduled craniotomy. Case presentation : A 69-year-old man was admitted to the hospital for elective craniotomy for craniopharyngioma. After the surgery, he developed refractory seizure and required intubation and mechanical ventilation in the intensive-care unit (ICU). After treatment for the seizure, he was extubated. However, immediately after extubation, he developed stridor and respiratory retraction. We performed fiberoptic laryngoscopy and confirmed that the epiglottis had collapsed into the posterior wall of the pharynx during inspiration, which was suspected to be laryngomalacia. He received invasive mechanical ventilation for two days following re-extubation. After the second extubation, he developed stridor again due to acquired laryngomalacia. Six days later, his respiratory condition had worsened, and he received re-intubation and tracheostomy. After ICU discharge, central pontine myelinolysis was diagnosed by magnetic resonance imaging. Conclusions : Adult-onset laryngomalacia is a rare cause of upper airway obstruction but should be considered as a cause of postoperative extubation failure. We should not delay performing fiberoptic laryngoscopy to evaluate this pathology and provide optimal treatment. J. Med. Invest. 69 : 316-319, August, 2022.

Independent lung ventilation for the management of acute allograft rejection after single-lung transplantation for end-stage emphysema.

Background : We herein report the use of independent lung ventilation (ILV) for managing acute allograft rejection after single-lung transplantation (SLT) for end-stage emphysema. Case presentation : A 54-year-old woman was transferred to our hospital with severe hypoxemia and respiratory distress due to unilateral lung disease with diffuse alveolar damage in the right donor lung associated with acute allograft rejection and with hyperinflation of the left native lung due to emphysema. She was unresponsive to immunosuppressive medications and conventional ventilation strategies, so different ventilator settings for each lung were required. A double-lumen endotracheal tube (DLT) was inserted, and ILV was initiated. The right lung was ventilated with high positive end-expiratory pressure (PEEP), intended for lung recruitment, and the left lung was ventilated with lung protective strategies using a low tidal volume and low levels of PEEP to avoid hyperinflation. Two days later, her lung function was dramatically improved, and the DLT was replaced with a single-lumen endotracheal tube. Gas exchange was maintained, and she was successfully weaned from mechanical ventilation on intensive-care unit day 15. Conclusions : ILV appears to be effective and safe for managing acute allograft rejection after SLT for emphysema. J. Med. Invest. 69 : 323-327, August, 2022.

Relationships between double cycling and inspiratory effort with diaphragm thickness during the early phase of mechanical ventilation: A prospective observational study.

BACKGROUND: Increased and decreased diaphragm thickness during mechanical ventilation is associated with poor outcomes. Some types of patient-ventilator asynchrony theoretically cause myotrauma of the diaphragm. However, the effects of double cycling on structural changes in the diaphragm have not been previously evaluated. Hence, this study aimed to investigate the relationship between double cycling during the early phase of mechanical ventilation and changes in diaphragm thickness, and the involvement of inspiratory effort in the occurrence of double cycling. METHODS: We evaluated adult patients receiving invasive mechanical ventilation for more than 48 h. The end-expiratory diaphragm thickness (Tdiee) was assessed via ultrasonography on days 1, 2, 3, 5 and 7 after the initiation of mechanical ventilation. Then, the maximum rate of change from day 1 (ΔTdiee%) was evaluated. Concurrently, we recorded esophageal pressure and airway pressure on days 1, 2 and 3 for 1 h during spontaneous breathing. Then, the waveforms were retrospectively analyzed to calculate the incidence of double cycling (double cycling index) and inspiratory esophageal pressure swing (ΔPes). Finally, the correlation between double cycling index as well as ΔPes and ΔTdiee% was investigated using linear regression models. RESULTS: In total, 19 patients with a median age of 69 (interquartile range: 65-78) years were enrolled in this study, and all received pressure assist-control ventilation. The Tdiee increased by more than 10% from baseline in nine patients, decreased by more than 10% in nine and remained unchanged in one. The double cycling indexes on days 1, 2 and 3 were 2.2%, 1.3% and 4.5%, respectively. There was a linear correlation between the double cycling index on day 3 and ΔTdiee% (R2 = 0.446, p = 0.002). The double cycling index was correlated with the ΔPes on days 2 (R2 = 0.319, p = 0.004) and 3 (R2 = 0.635, p < 0.001). CONCLUSIONS: Double cycling on the third day of mechanical ventilation was associated with strong inspiratory efforts and, possibly, changes in diaphragm thickness.

Rectus Femoris Mimicking Ultrasound Phantom for Muscle Mass Assessment: Design, Research, and Training Application.

Ultrasound has become widely used as a means to measure the rectus femoris muscle in the acute and chronic phases of critical illness. Despite its noninvasiveness and accessibility, its accuracy highly depends on the skills of the technician. However, few ultrasound phantoms for the confirmation of its accuracy or to improve technical skills exist. In this study, the authors created a novel phantom model and used it for investigating the accuracy of measurements and for training. Study 1 investigated how various conditions affect ultrasound measurements such as thickness, cross-sectional area, and echogenicity. Study 2 investigated if the phantom can be used for the training of various health care providers in vitro and in vivo. Study 1 showed that thickness, cross-sectional area, and echogenicity were affected by probe compression strength, probe angle, phantom compression, and varying equipment. Study 2 in vitro showed that using the phantom for training improved the accuracy of the measurements taken within the phantom, and Study 2 in vivo showed the phantom training had a short-term effect on improving the measurement accuracy in a human volunteer. The new ultrasound phantom model revealed that various conditions affected ultrasound measurements, and phantom training improved the measurement accuracy.

Upper limb muscle atrophy associated with in-hospital mortality and physical function impairments in mechanically ventilated critically ill adults: a two-center prospective observational study.

BACKGROUND: Lower limb muscle atrophy is often observed in critically ill patients. Although upper limb muscles can undergo atrophy, it remains unclear how this atrophy is associated with clinical outcomes. We hypothesized that this atrophy is associated with mortality and impairments in physical function. METHODS: In this two-center prospective observational study, we included adult patients who were expected to require mechanical ventilation for > 48 h and remain in the intensive care unit (ICU) for > 5 days. We used ultrasound to evaluate the cross-sectional area of the biceps brachii on days 1, 3, 5, and 7 and upon ICU discharge along with assessment of physical functions. The primary outcome was the relationship between muscle atrophy ratio and in-hospital mortality on each measurement day, which was assessed using multivariate analysis. The secondary outcomes were the relationships between upper limb muscle atrophy and Medical Research Council (MRC) score, handgrip strength, ICU Mobility Scale (IMS) score, and Functional Status Score for the ICU (FSS-ICU). RESULTS: Sixty-four patients (43 males; aged 70 ± 13 years) were enrolled. The Acute Physiology and Chronic Health Evaluation (APACHE) II score was 27 (22-30), and in-hospital mortality occurred in 21 (33%) patients. The decreased cross-sectional area of the biceps brachii was not associated with in-hospital mortality on day 3 (p = 0.43) but was associated on days 5 (p = 0.01) and 7 (p < 0.01), which was confirmed after adjusting for sex, age, and APACHE II score. In 27 patients in whom physical functions were assessed, the decrease of the cross-sectional area of the biceps brachii was associated with MRC score (r = 0.47, p = 0.01), handgrip strength (r = 0.50, p = 0.01), and FSS-ICU (r = 0.56, p < 0.01), but not with IMS score (r = 0.35, p = 0.07) upon ICU discharge. CONCLUSIONS: Upper limb muscle atrophy was associated with in-hospital mortality and physical function impairments; thus, it is prudent to monitor it. (321 words) TRIAL REGISTRATION: UMIN 000031316 . Retrospectively registered on 15 February 2018.

Association of the winged helix motif of the TFIIEα subunit of TFIIE with either the TFIIEß subunit or TFIIB distinguishes its functions in transcription.

In eukaryotes, the general transcription factor TFIIE consists of two subunits, α and ß, and plays essential roles in transcription. Structure-function studies indicate that TFIIE has three-winged helix (WH) motifs, with one in TFIIEα and two in TFIIEß. Recent studies suggested that, by binding to the clamp region of RNA polymerase II, TFIIEα-WH promotes the conformational change that transforms the promoter-bound inactive preinitiation complex to the active complex. Here, to elucidate its roles in transcription, functional analyses of point-mutated human TFIIEα-WH proteins were carried out. In vitro transcription analyses identified two classes of mutants. One class was defective in transcription initiation, and the other was defective in the transition from initiation to elongation. Analyses of the binding of this motif to other general transcription factors showed that the former class was defective in binding to the basic helix-loop-helix motif of TFIIEß and the latter class was defective in binding to the N-terminal cyclin homology region of TFIIB. Furthermore, TFIIEα-WH bound to the TFIIH XPB subunit at a third distinct region. Therefore, these results provide further insights into the mechanisms underlying RNA polymerase II activation at the initial stages of transcription.

Transcription cofactor PC4 plays essential roles in collaboration with the small subunit of general transcription factor TFIIE.

In eukaryotes, positive cofactor 4 (PC4) stimulates activator-dependent transcription by facilitating transcription initiation and the transition from initiation to elongation. It also forms homodimers and binds to single-stranded DNA and various transcriptional activators, including the general transcription factor TFIIH. In this study, we further investigated PC4 from Homo sapiens and the nematode Caenorhabditis elegans (hPC4 and cePC4, respectively). hPC4 strongly stimulated transcription on a linearized template, whereas it alleviated transcription on a supercoiled template. Transcriptional stimulation by PC4 was also alleviated by increasing the amount of TFIID. GST pull-down studies with general transcription factors indicated that both hPC4 and cePC4 bind strongly to TFIIB, TFIIEß, TFIIFα, TFIIFß and TFIIH XPB subunits and weakly to TBP and TFIIH p62. However, only hPC4 bound to CDK7. The effect of each PC4 on transcription was studied in combination with TFIIEß. hPC4 stimulated both basal and activated transcription, whereas cePC4 primarily stimulated activated transcription, especially in the presence of TFIIEß from C. elegans. Finally, hPC4 bound to the C-terminal region of hTFIIEß adjacent to the basic region. These results indicate that PC4 plays essential roles in the transition step from transcription initiation to elongation by binding to melted DNA in collaboration with TFIIEß.