Noninvasive ventilation for patients with hypoxemic acute respiratory failure.

Noninvasive ventilation (NIV) has an established efficacy to improve gas exchange and reduce the work of breathing in patients with hypoxemic acute respiratory failure. The clinical efficacy in terms of meaningful outcome is less clear and depends very much on patient selection and assessment of the risks of the technique. The potential risks include an insufficient reduction of the oxygen consumption of the respiratory muscles in case of shock, an excessive increase in tidal volume in case of lung injury, and a risk of delayed or emergent intubation. With a careful selection of patients and a rapid decision regarding the need for intubation in case of failure, great benefits can be offered to patients. Emerging indications include its use in patients with treatment limitations, in the postoperative period, and in patients with immunosuppression. This last indication will necessitate reappraisal because the prognosis of the conditions associated with immunosuppression has improved over the years. In all cases, there is both a time window and a severity window for NIV to work, after which delaying endotracheal intubation may worsen outcome. The preventive use of NIV seems promising in this setting but needs more research. An emerging interesting new option is the use of high flow humidified oxygen, which seems to be intermediate between oxygen alone and NIV.

Impact of Airway Humidification Strategy in Mechanically Ventilated COVID-19 Patients.

BACKGROUND: Humidification of inspiratory gases is mandatory in all mechanically ventilated patients in ICUs, either with heated humidifiers (HHs) or with heat and moisture exchangers (HMEs). In patients with COVID-19, the choice of the humidification device may have relevant impact on patients' management as demonstrated in recent studies. We reported data from 2 ICUs using either HME or HH. METHODS: Data from patients with COVID-19 requiring invasive mechanical ventilation during the first wave in 2 ICUs in Québec City were reviewed. In one ICU, HMEs were used, whereas heated-wire HHs were used in the other ICU. We compared ventilator settings and arterial blood gases at day one after adjustment of ventilator settings. Episodes of endotracheal tube occlusions (ETOs) or subocclusions and a strategy to limit the risk of under-humidification were reported. On a bench test, we measured humidity with psychrometry with HH at different ambient temperature and evaluated the relation with heater plate temperature. RESULTS: We reported data from 20 subjects positive for SARS-Cov-2, including 6 in the ICU using HME and 14 in the ICU using HH. In the HME group, PaCO2 was higher (48 vs 42 mm Hg) despite higher minute ventilation (171 vs 145 mL/kg/min predicted body weight [PBW]). We also reported 3 ETOs occurring in the ICU using HH. The hygrometric bench study reported a strong correlation between heater plate temperatures of the HH and humidity delivered. After implementation of measures to avoid under-humidification, including heater plate temperature monitoring, no more ETOs occurred. CONCLUSIONS: The choice of the humidification device used in subjects with COVID-19 had a relevant impact on ventilation efficiency (increased CO2 removal with lower dead space) and on complications related to low humidity, including ETOs that may be present with heated-wire HHs when used with high ambient temperatures.

Positioning of patients with acute respiratory distress syndrome: combining prone and upright makes sense.

Positional strategies have been proposed for mechanically ventilated patients with acute respiratory distress syndrome. Despite different physiological mechanisms involved, oxygenation improvement has been demonstrated with both prone and upright positions. In the previous issue of Critical Care, Robak and colleagues reported the first study evaluating the short-term effects of combining prone and upright positioning. The combined positioning enhanced the response rate in terms of oxygenation. Other benefits, such as a reduction in ventilator-associated pneumonia and better enteral feeding tolerance, can potentially be expected.

Can proportional ventilation modes facilitate exercise in critically ill patients? A physiological cross-over study : Pressure support versus proportional ventilation during lower limb exercise in ventilated critically ill patients.

BACKGROUND: Early exercise of critically ill patients may have beneficial effects on muscle strength, mass and systemic inflammation. During pressure support ventilation (PSV), a mismatch between demand and assist could increase work of breathing and limit exercise. A better exercise tolerance is possible with a proportional mode of ventilation (Proportional Assist Ventilation, PAV+ and Neurally Adjusted Ventilatory Assist, NAVA). We examined whether, in critically ill patients, PSV and proportional ventilation have different effects on respiratory muscles unloading and work efficiency during exercise. METHODS: Prospective pilot randomized cross-over study performed in a medico-surgical ICU. Patients requiring mechanical ventilation >48 h were enrolled. At initiation, the patients underwent an incremental workload test on a cycloergometer to determine the maximum level capacity. The next day, 2 15-min exercise, at 60% of the maximum capacity, were performed while patients were randomly ventilated with PSV and PAV+ or NAVA. The change in oxygen consumption (ΔVO2, indirect calorimetry) and the work efficiency (ratio of ΔVO2 per mean power) were computed. RESULTS: Ten patients were examined, 6 ventilated with PSV/PAV+ and 4 with PSV/NAVA. Despite the same mean inspiratory pressure at baseline between the modes, baseline VO2 (median, IQR) was higher during proportional ventilation (301 ml/min, 270-342) compared to PSV (249 ml/min, 206-353). Exercise with PSV was associated with a significant increase in VO2 (ΔVO2, median, IQR) (77.6 ml/min, 59.9-96.5), while VO2 did not significantly change during exercise with proportional modes (46.3 ml/min, 5.7-63.7, p < 0.05). As a result, exercise with proportional modes was associated with a better work efficiency than with PSV. The ventilator modes did not affect patient's dyspnea, limb fatigue, distance, hemodynamics and breathing pattern. CONCLUSIONS: Proportional ventilation during exercise results in higher work efficiency and less increase in VO2 compared to ventilation with PSV. These preliminary findings suggest that proportional ventilation could enhance the training effect and facilitate rehabilitation.

Easy and fast detection and genotyping of high-risk human papillomavirus by dedicated DNA microarrays.

Persistent cervical high-risk human papillomavirus (HPV) infection is correlated with an increased risk of developing a high-grade cervical intraepithelial lesion. A two-step method was developed for detection and genotyping of high-risk HPV. DNA was firstly amplified by asymmetrical PCR in the presence of Cy3-labelled primers and dUTP. Labelled DNA was then genotyped using DNA microarray hybridization. The current study evaluated the technical efficacy of laboratory-designed HPV DNA microarrays for high-risk HPV genotyping on 57 malignant and non-malignant cervical smears. The approach was evaluated for a broad range of cytological samples: high-grade squamous intraepithelial lesions (HSIL), low-grade squamous intraepithelial lesions (LSIL) and atypical squamous cells of high-grade (ASC-H). High-risk HPV was also detected in six atypical squamous cells of undetermined significance (ASC-US) samples; among them only one cervical specimen was found uninfected, associated with no histological lesion. The HPV oligonucleotide DNA microarray genotyping detected 36 infections with a single high-risk HPV type and 5 multiple infections with several high-risk types. Taken together, these results demonstrate the sensitivity and specificity of the HPV DNA microarray approach. This approach could improve clinical management of patients with cervical cytological abnormalities.

Designing a HER2/neu promoter to drive alpha1,3galactosyltransferase expression for targeted anti-alphaGal antibody-mediated tumor cell killing.

INTRODUCTION: Our goal was to specifically render tumor cells susceptible to natural cytolytic anti-alphaGal antibodies by using a murine alpha1,3galactosyltransferase (malphaGalT) transgene driven by a designed form of HER2/neu promoter (pNeu), the transcription of which is frequently observed to be above basal in breast tumors. Indeed, the alphaGalT activity that promotes Galalpha1,3Galbeta1,4GlcNAc-R (alphaGal) epitope expression has been mutationally disrupted during the course of evolution, starting from Old World primates, and this has led to the counter-production of large amounts of cytotoxic anti-alphaGal antibodies in recent primates, including man. METHOD: Expression of the endogenous c-erbB-2 gene was investigated in various cell lines by northern blotting. A malphaGalT cDNA was constructed into pcDNA3 vector downstream of the original CMV promoter (pCMV/malphaGalT) and various forms of pNeu were prepared by PCR amplification and inserted in the pCMV/malphaGalT construct upstream of the malphaGalT cDNA, in the place of the CMV promoter. These constructs were transferred into HEK-293 control and breast tumor cell lines. Stably transfected cells were analyzed by northern blotting for their expression of alphaGalT and c-erbB-2, and by flow cytometry for their binding with fluorescein isothiocyanate-conjugated Griffonia simplicifolia/isolectin B4. RESULTS: We show that expression of the malphaGalT was up- or down-modulated according to the level of endogenous pNeu activity and the particular form of constructed pNeu. Among several constructs, two particular forms of the promoter, pNeu250 containing the CCAAT box and the PEA3 motif adjacent to the TATAA box, and pNeu664, which has three additional PEA3 motifs upstream of the CCAAT box, were found to promote differential alphaGalT expression. CONCLUSION: Our results strengthen current concepts about the crucial role played by the proximal PEA3 motif of pNeu, and may represent a novel therapeutic approach for the development of targeted transgene expression.

Epigenetic reprogramming of UDP-N-acetylglucosamine 2-epimerase/N-acetylmannosamine kinase (GNE) in HIV-1-infected CEM T cells.

Sialylated glycoconjugates mediate several key lymphocyte functions. We previously reported that hyposialylation occurred in latently HIV-1-infected CEM T cells, despite the fully preserved catalytic activity of several sialyltransferases. We show now that these cells are affected by a down-regulation of UDP-N-acetylglucosamine 2-epimerase/N-acetylmannosamine kinase (GNE), which leads to a dramatic decrease in the synthesis of CMP-sialic acid, the donor substrate of all sialyltransferases. The GNE gene promoter was found to be located in a CpG island with several regulatory motifs CREB, SP1, and AP-2. De novo hypermethylation of this promoter was observed in HIV-1-infected CEM cells. This phenomenon might explain some immunological disorders that persist in infected individuals despite long-term therapeutically controlled viral replication. Indeed, an overall decrease in sialic acid engraftment can affect glycoproteins, notably those in which the sialylation status is crucial to ensure homing, recirculation, and survival of lymphocytes.

Bench testing of a new hyperbaric chamber ventilator at different atmospheric pressures.

PURPOSE: Providing mechanical ventilation is challenging at supra-atmospheric pressure. The higher gas density increases resistance, reducing the flow delivered by the ventilator. A new hyperbaric ventilator (Siaretron IPER 1000) is said to compensate for these effects automatically. The aim of this bench test study was to validate the compensation, define its limits and provide details on the ventilator's output at varied atmospheric pressures. METHODS: Experiments were conducted inside a multiplace hyperbaric chamber at 1, 2.2, 2.8 and 4 atmospheres absolute (ATA), with the ventilator connected to a test lung. Transducers were recalibrated at each ATA level. Various ventilator settings were tested in volume and pressure control modes. Measured tidal volumes were compared with theoretical predictions based on gas laws. RESULTS: Results confirmed the ventilator's ability to provide compensation, but also identified its limits. The compensation range could be predicted and depended on the maximal flow attainable, decreasing linearly with increasing atmospheric pressure. With settings inside the range, tidal volumes approximated set values (mean error 10 ± 5 %). With settings outside the range, the volume was limited to the predicted maximal value calculated from maximal flow. A practical guide for clinicians is provided. CONCLUSION: The IPER 1000 ventilator attempted to deliver stable tidal volume by adjusting the opening of the inspiratory valve in proportion to atmospheric pressure. Adequate compensation was observed, albeit only within a predictable range, which can be reliably predicted for each setting and ATA level combination. Setting a tidal volume outside this range can result in an unwanted decrease in minute ventilation.

Immunohistochemical and molecular study of severe cervical dysplasia associated with HPV-83.

BACKGROUND: Based on epidemiological data, infections with specific types of HPV can be classified as high-risk (HR), low-risk (LR) or intermediate-risk (IR) HPV depending on the risk of progression to cervical cancer. CASE: A 70-year-old woman consulted for relapse of abnormal cytology with high-grade squamous intraepithelial lesions (HSIL) associated with HPV-83 infection. Histological examination demonstrated high-grade cervical intraepithelial neoplasia (CIN III) with strong and diffuse staining by the P16(INK4a)-specific antibody. CONCLUSION: This patient's intermediate-risk HPV infection (HPV-83) rapidly progressed to severe cervical intraepithelial neoplasia (CIN III) with strong anti-P16(INK4a) immunolabelling. Analysis of the E6 peptide sequence revealed several mutations in one of the two putative zinc finger regions (AA residues 107-135) associated with p53 binding.

High permissivity of human HepG2 hepatoma cells for influenza viruses.

Human HepG2 hepatoma cells are highly permissive for influenza virus type A and type B, even without the addition of trypsin, and they exhibit a marked cytopathic effect. This property greatly facilitates the primary isolation of influenza viruses. Virus replication was significantly reduced by the plasmin(ogen)-specific inhibitor tranexamic acid, and this suggests a potential role played by the plasminogen/tissue plasminogen activator complex at the surface of HepG2 cells. This might represent a new approach for study of the interrelations of this complex with influenza viruses.

A complete alpha1,3-galactosyltransferase gene is present in the human genome and partially transcribed.

The synthesis of Galalpha1-3Gal-terminated oligosaccharides (alpha-Gal) epitopes has been interrupted during the course of evolution, starting with Old World primates. Partial sequences similar to the alpha1,3-galactosyltransferase (alpha1,3GalT) gene, which governs the synthesis of alpha-Gal epitopes, have been detected in the human genome and were found to correspond to pseudogenes. We completed the sequence of the human alpha1,3GalT pseudogene present on chromosome 9 and found it to be organized like the murine alpha1,3GalT gene. In human cell lines and several normal and tumor tissues we detected truncated transcripts corresponding to this pseudogene. Considering these mRNAs, translation of an open reading frame containing the first four translated exons but missing the two catalytic exons could predict a truncated alpha1,3GalT polypeptide that should be enzymatically inactive. We show that transcription of human alpha1,3GalT is prematurely terminated at the level of a strong transcriptional stop signal in the middle of intron VII. We were able to reproduce this effect in vitro by subcloning the implicated DNA region upstream from a reporter cDNA. The premature transcriptional arrest of human alpha1,3-GalT gene leads to an ectopic splicing event and to the connection of a short intronic sequence downstream from translated exons. Finally, we show that these truncated transcripts are overexpressed in cell lines with modifications of O-glycans.

Altered T cell surface glycosylation in HIV-1 infection results in increased susceptibility to galectin-1-induced cell death.

The massive T cell death that occurs in HIV type 1 (HIV-1) infection contributes profoundly to the pathophysiology associated with AIDS. The mechanisms controlling cell death of both infected and uninfected T cells ("bystander" death) are not completely understood. We have shown that HIV-1 infection of T cells results in altered glycosylation of cell surface glycoproteins; specifically, it decreased sialylation and increased expression of core 2 O-glycans. Galectin-1 is an endogenous human lectin that recognizes these types of glycosylation changes and induces cell death of activated lymphocytes. Therefore we studied the possible contribution of galectin-1 in the pathophysiology of AIDS. O-glycan modifications were investigated on peripheral lymphocytes from AIDS patients. Oligosaccharides from CD43 and CD45 of CEM cells latently infected with HIV-1 were chemically analyzed. Consistent with our previous results, we show that HIV-1 infection results in accumulation of exposed lactosamine residues, oligosaccharides recognized by galectin-1 on cell surface glycoproteins. Both latently HIV-1-infected T cell lines and peripheral CD4 and CD8 T cells from AIDS patients exhibited exposed lactosamine residues and demonstrated marked susceptibility to galectin-1-induced cell death, in contrast to control cultures or cells from uninfected donors. The fraction of cells that died in response to galectin-1 exceeded the fraction of infected cells, indicating that death of uninfected cells occurred. Altered cell surface glycosylation of T cells during HIV-1 infection increases the susceptibility to galectin-1-induced cell death, and this death pathway can contribute to loss of both infected and uninfected T cells in AIDS.