Influence of different noninvasive oxygenation support devices on tidal volume.

BACKGROUND: Multiple devices are available for noninvasive oxygenation support, including non-rebreather oxygen mask (O2-mask), high-flow oxygen through nasal cannula (HFNC), continuous positive airway pressure (CPAP), mask noninvasive ventilation (Mask-NIV) and helmet NIV (Helmet-NIV). As tidal volume is a key determinant of efficacy and safety during ventilatory support, we assessed whether it was influenced by the type of noninvasive oxygenation device. METHODS: A bench study using a manikin with a realistic face connected to a lung simulator was performed. Six conditions were assessed: no device, O2-mask, HFNC, CPAP, Mask-NIV and Helmet-NIV. Three respiratory mechanics were simulated (normal, obstructive, restrictive), at three simulated efforts (low, moderate, respiratory distress). Flow was recorded at the lung simulator inlet and mouth pressure into the manikin mouth. The same devices were evaluated on healthy volunteers with tidal volume assessed by electrical impedance tomography (EIT). RESULTS: Tidal volume was significantly influenced by oxygenation devices in bench model. As compared to O2-mask, HFNC and CPAP delivered significantly lower tidal volumes (440 ± 352 mL, 414 ± 333 mL and 377 ± 297 mL, respectively), while Mask-NIV or Helmet-NIV were associated with significantly higher tidal volumes (690 ± 321 mL and 652 ± 366 mL, respectively). Tidal volume was strongly correlated with the specific effect of each device on mouth pressure during inspiration: HFNC and CPAP were characterized by a negative PTPmouth (- 0.3 [- 0.8 to - 0.2] and - 0.7 [- 2.2 to - 0.5] cmH2O.sec/cycle, respectively), while Helmet-NIV and Mask-NIV were associated with a positive PTPmouth (4.5 [4.1-4.6] and 6.1 [5.9-7.1] cmH2O.sec/cycle, respectively). Tidal volume was also significantly influenced by oxygenation devices in healthy volunteers, with similar tidal volumes between O2-mask and CPAP (644 [571-764] and 648 [586-770] mL) but higher with HFNC, Mask-NIV and Helmet-NIV (819 [609-918], 1110 [661-1305] and 1086 [833-1243] mL). CONCLUSIONS: Tidal volume is significantly influenced by noninvasive oxygenation support devices, with a strong correlation with the pressure variation generated into the mouth during inspiration. NIV was associated with the highest tidal volumes and CPAP with the lowest ones. Clinical studies are needed to clarify the clinical implications of these effects.

Dual titration of minute ventilation and sweep gas flow to control carbon dioxide variations in patients on venovenous extracorporeal membrane oxygenation.

BACKGROUND: The implantation of venovenous extracorporeal membrane oxygenation (VV-ECMO) support to manage severe acute respiratory distress syndrome generates large variations in carbon dioxide partial pressure (PaCO2) that are associated with intracranial bleeding. We assessed the feasibility and efficacy of a pragmatic protocol for progressive dual titration of sweep gas flow and minute ventilation after VV-ECMO implantation in order to limit significant PaCO2 variations. PATIENTS AND METHODS: A protocol for dual titration of sweep gas flow and minute ventilation following VV-ECMO implantation was implemented in our unit in September 2020. In this single-centre retrospective before-after study, we included patients who required VV-ECMO from March, 2020 to May, 2021, which corresponds to two time periods: from March to August, 2020 (control group) and from September, 2020 to May, 2021 (protocol group). The primary endpoint was the mean absolute change in PaCO2 in consecutive arterial blood gases samples drawn over the first 12 h following VV-ECMO implantation. Secondary endpoints included large (> 25 mmHg) initial variations in PaCO2, intracranial bleedings and mortality in both groups. RESULTS: Fifty-one patients required VV-ECMO in our unit during the study period, including 24 in the control group and 27 in the protocol group. The protocol was proved feasible. The 12-h mean absolute change in PaCO2 was significantly lower in patients of the protocol group as compared with their counterparts (7 mmHg [6-12] vs. 12 mmHg [6-24], p = 0.007). Patients of the protocol group experienced less large initial variations in PaCO2 immediately after ECMO implantation (7% vs. 29%, p = 0.04) and less intracranial bleeding (4% vs. 25%, p = 0.04). Mortality was similar in both groups (35% vs. 46%, p = 0.42). CONCLUSION: Implementation of our protocol for dual titration of minute ventilation and sweep gas flow was feasible and associated with less initial PaCO2 variation than usual care. It was also associated with less intracranial bleeding.

Driving pressure-guided ventilation decreases the mechanical power compared to predicted body weight-guided ventilation in the Acute Respiratory Distress Syndrome.

BACKGROUND: Whether targeting the driving pressure (∆P) when adjusting the tidal volume in mechanically ventilated patients with the acute respiratory distress syndrome (ARDS) may decrease the risk of ventilator-induced lung injury remains a matter of research. In this study, we assessed the effect of a ∆P-guided ventilation on the mechanical power. METHODS: We prospectively included adult patients with moderate-to-severe ARDS. Positive end expiratory pressure was set by the attending physician and kept constant during the study. Tidal volume was first adjusted to target 6 ml/kg of predicted body weight (PBW-guided ventilation) and subsequently modified within a range from 4 to 10 ml/kg PBW to target a ∆P between 12 and 14 cm H2O. The respiratory rate was then re-adjusted within a range from 12 to 40 breaths/min until EtCO2 returned to its baseline value (∆P-guided ventilation). Mechanical power was computed at each step. RESULTS: Fifty-one patients were included between December 2019 and May 2021. ∆P-guided ventilation was feasible in all but one patient. The ∆P during PBW-guided ventilation was already within the target range of ∆P-guided ventilation in five (10%) patients, above in nine (18%) and below in 36 (72%). The change from PBW- to ∆P-guided ventilation was thus accompanied by an overall increase in tidal volume from 6.1 mL/kg PBW [5.9-6.2] to 7.7 ml/kg PBW [6.2-8.7], while respiratory rate was decreased from 29 breaths/min [26-32] to 21 breaths/min [16-28] (p < 0.001 for all comparisons). ∆P-guided ventilation was accompanied by a significant decrease in mechanical power from 31.5 J/min [28-35.7] to 28.8 J/min [24.6-32.6] (p < 0.001), representing a relative decrease of 7% [0-16]. With ∆P-guided ventilation, the PaO2/FiO2 ratio increased and the ventilatory ratio decreased. CONCLUSION: As compared to a conventional PBW-guided ventilation, a ∆P-guided ventilation strategy targeting a ∆P between 12 and 14 cm H2O required to change the tidal volume in 90% of the patients. Such ∆P-guided ventilation significantly reduced the mechanical power. Whether this physiological observation could be associated with clinical benefit should be assessed in clinical trials.

Functional Ex Vivo Testing of Alveolar Monocytes in Patients with Pneumonia-Related ARDS.

Biomarkers of disease severity might help with individualizing the management of patients with acute respiratory distress syndrome (ARDS). During sepsis, a sustained decreased expression of the antigen-presenting molecule human leucocyte antigen-DR (HLA-DR) on circulating monocytes is used as a surrogate marker of immune failure. This study aimed at assessing whether HLA-DR expression on alveolar monocytes in the setting of a severe lung infection is associated with their functional alterations. BAL fluid and blood from immunocompetent patients with pneumonia-related ARDS admitted between 2016 and 2018 were isolated in a prospective monocentric study. Alveolar and blood monocytes were immunophenotyped using flow cytometry. Functional tests were performed on alveolar and blood monocytes after in vitro lipopolysaccharide (LPS) stimulation. Phagocytosis activity and intracellular tumor necrosis factor (TNF) production were quantified using fluorochrome-conjugated-specific antibodies. Ten ARDS and seven non-ARDS control patients were included. Patients with pneumonia-related ARDS exhibited significantly lower HLA-DR expression both on circulating (p < 0.0001) and alveolar (p = 0.0002) monocytes. There was no statistically significant difference observed between patient groups (ARDS vs. non-ARDS) regarding both alveolar and blood monocytes phagocytosis activity. After LPS stimulation, alveolar (p = 0.027) and blood (p = 0.005) monocytes from pneumonia-related ARDS patients had a significantly lower intracellular TNF expression than non-ARDS patients. Monocytes from pneumonia-related ARDS patients have a deactivated status and an impaired TNF production capacity but display potent phagocytic activity. HLA-DR level expression should not be used as a surrogate marker of the phagocytic activity or the TNF production capacity of alveolar monocytes.

Severe Hemoptysis Associated with Bacterial Pulmonary Infection: Clinical Features, Significance of Parenchymal Necrosis, and Outcome.

PURPOSE: Severe hemoptysis (SH) associated with non-tuberculosis bacterial lower respiratory tract infection (LRTI) is poorly described, and the efficacy of the usual decision-making process is unknown. This study aimed at describing the clinical, radiological patterns, mechanism, and microbiological spectrum of SH related to bacterial LRTI, and assessing whether the severity of hemoptysis and the results of usual therapeutic strategy are influenced by the presence of parenchymal necrosis. METHODS: A single-center analysis of patients with SH related to bacterial LRTI from a prospective registry of consecutive patients with SH admitted to the intensive care unit of a tertiary referral center between November 1996 and May 2013. RESULTS: Of 1504 patients with SH during the study period, 65 (4.3%) had SH related to bacterial LRTI, including non-necrotizing infections (n = 31), necrotizing pneumonia (n = 23), pulmonary abscess (n = 10), and excavated nodule (n = 1). The presence of parenchymal necrosis (n = 34, 52%) was associated with a more abundant bleeding (volume: 200 ml [70-300] vs. 80 ml [30-170]; p = 0.01) and a more frequent need for endovascular procedure (26/34; 76% vs. 9/31; 29%; p < 0.001). Additionally, in case of parenchymal necrosis, the pulmonary artery vasculature was involved in 16 patients (47%), and the failure rate of endovascular treatment was up to 25% despite multiple procedures. CONCLUSIONS: Bacterial LRTI is a rare cause of SH. The presence of parenchymal necrosis is more likely associated with bleeding severity, pulmonary vasculature involvement, and endovascular treatment failure.

Etiologies, diagnostic work-up and outcomes of acute respiratory distress syndrome with no common risk factor: a prospective multicenter study.

BACKGROUND: Patients meeting the Berlin definition for the acute respiratory distress syndrome (ARDS) might lack exposure to one or more "common" risk factors and exhibit different clinical phenotype and outcomes. We aimed to compare the clinical presentation and outcome of ARDS patients with or without risk factors, the impact on hospital mortality, and to assess the diagnostic work-up performed. The current study is an ancillary analysis of an international, multicenter, prospective cohort study (the Large Observational Study to Understand the Global Impact of Severe Acute Respiratory Failure, LUNG SAFE). Patients meeting ARDS criteria within 2 days of acute hypoxemic respiratory failure onset were included in the study and categorized as having risk factors or not. Outcomes were compared using propensity score matching. RESULTS: Among 2813 patients, 234 (8.3% [7.3-9.3]) had no ARDS risk factor identified. These were older, had more frequent chronic diseases and presented with less severe SOFA and non-pulmonary SOFA scores (p < 0.001). Compared to other ARDS, CT scan (32.1 vs 23.9%, p < 0.001) and open lung biopsy (2.6 vs 0.2%, p < 0.001) were slightly more frequent but left heart filling pressures assessment was not (69.4 vs 68.4%, p > 0.99). Among ARDS with no risk factor, 45 patients (19.2%) had a specific diagnosis made. As compared to others, patients having ARDS with no risk factor had a lower ICU but not hospital mortality (34.6 vs 40.0%; p = 0.12). A matched cohort analysis confirmed the lack of significant difference in mortality. CONCLUSION: Eight percent of ARDS patients have no identified risk factor, 80% of whom have no etiological diagnosis made. The outcome of ARDS with no risk factor was comparable to other ARDS but few had a comprehensive diagnostic work-up, potentially leading to missed curable diseases. Trial registration clinicaltrials.gov Identifier: NCT02010073.

Neuroimaging findings of postnatally acquired Zika virus infection: a pictorial essay.

Zika virus (ZIKV) is a mosquito-borne arbovirus from the Flaviviridae family, first discovered in 1947. There has been no report of severe complications caused by this virus in humans until recently. However, it is confirmed now that prenatally acquired ZIKV infection may cause severe congenital brain abnormalities in the infected fetuses. In addition, there has been an increasing number of reports during recent years about the causal relationship between postnatally acquired ZIKV infection and severe neurologic complications (mostly immune-mediated ones). Hence, ZIKV should not be considered as benign as it was initially thought, but it might be seen as a serious global threat to human health that may severely affect not only fetuses. In this pictorial essay, we aim to describe and illustrate the currently recognized spectrum of neuroimaging findings in postnatally acquired ZIKV infection. Although neurologic complications do not frequently occur in postnatal ZIKV infection, it is important to be aware of them because they may cause high morbidity and mortality in the affected patients. In addition to clinical and laboratory findings, neuroimaging may help in the diagnostic work-up to make the correct diagnosis, determine the extent of the disease, and follow the clinical course.

Hypoxaemic rescue therapies in acute respiratory distress syndrome: Why, when, what and which one?

Acute respiratory distress syndrome (ARDS) is an inflammatory condition of the lungs which can result in refractory and life-threatening hypoxaemic respiratory failure. The risk factors for the development of ARDS are many but include trauma, multiple blood transfusions, burns and major surgery, therefore this condition is not uncommon in the severely injured patient. When ARDS is severe, high-inspired oxygen concentrations are frequently required to minimise hypoxaemia. In these situations clinicians commonly utilise interventions termed 'hypoxaemic rescue therapies' in an attempt to improve oxygenation, as without these, conventional mechanical ventilation can be associated with high mortality. However, their lack of efficacy on mortality when used prophylactically in generalised ARDS cohorts has resulted in their use being confined to clinical trials and the subset of ARDS patients with refractory hypoxaemia. First line hypoxaemic rescue therapies include inhaled nitric oxide, prone positioning, alveolar recruitment manoeuvres and high frequency oscillatory ventilation, which have all been shown to be effective in improving oxygenation. In situations where these first line rescue therapies are inadequate extra-corporeal membrane oxygenation has emerged as a lifesaving second line rescue therapy. Rescue therapies in critically ill patients with traumatic injuries presents specific challenges and requires careful assessment of both the short and longer term benefits, therapeutic limitations, and specific adverse effects before their use.