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1.
Anesthesiology ; 2021 Oct 13.
Artigo em Inglês | MEDLINE | ID: mdl-34644374

RESUMO

BACKGROUND: Experimental and pilot clinical data suggest that spontaneously breathing patients with sepsis and septic shock may present increased respiratory drive and effort, even in the absence of pulmonary infection. The study hypothesis was that respiratory drive and effort may be increased in septic patients and correlated with extrapulmonary determinant and that high-flow nasal cannula may modulate drive and effort. METHODS: Twenty-five nonintubated patients with extrapulmonary sepsis or septic shock were enrolled. Each patient underwent three consecutive steps: low-flow oxygen at baseline, high-flow nasal cannula, and then low-flow oxygen again. Arterial blood gases, esophageal pressure, and electrical impedance tomography data were recorded toward the end of each step. Respiratory effort was measured as the negative swing of esophageal pressure (ΔPes); drive was quantified as the change in esophageal pressure during the first 500 ms from start of inspiration (P0.5). Dynamic lung compliance was calculated as the tidal volume measured by electrical impedance tomography, divided by ΔPes. The results are presented as medians [25th to 75th percentile]. RESULTS: Thirteen patients (52%) were in septic shock. The Sequential Organ Failure Assessment score was 5 [4 to 9]. During low-flow oxygen at baseline, respiratory drive and effort were elevated and significantly correlated with arterial lactate (r = 0.46, P = 0.034) and inversely with dynamic lung compliance (r = -0.735, P < 0.001). Noninvasive support by high-flow nasal cannula induced a significant decrease of respiratory drive (P0.5: 6.0 [4.4 to 9.0] vs. 4.3 [3.5 to 6.6] vs. 6.6 [4.9 to 10.7] cm H2O, P < 0.001) and effort (ΔPes: 8.0 [6.0 to 11.5] vs. 5.5 [4.5 to 8.0] vs. 7.5 [6.0 to 12.6] cm H2O, P < 0.001). Oxygenation and arterial carbon dioxide levels remained stable during all study phases. CONCLUSIONS: Patients with sepsis and septic shock of extrapulmonary origin present elevated respiratory drive and effort, which can be effectively reduced by high-flow nasal cannula.

2.
Eur Respir J ; 2021 Aug 19.
Artigo em Inglês | MEDLINE | ID: mdl-34413155

RESUMO

BACKGROUND: Although small randomised controlled trials (RCTs) and observational studies have examined helmet non-invasive ventilation (NIV), uncertainty remains regarding its role. We conducted a systematic review and meta-analysis to examine the effect of helmet NIV compared to facemask NIV or high flow nasal cannula (HFNC) in acute respiratory failure. METHODS: We searched multiple databases to identify RCTs and observational studies reporting on at least one of mortality, intubation, ICU length of stay, NIV duration, complications, or comfort with NIV therapy. We assessed study risk of bias (ROB) using the Cochrane ROB tool for RCTs and the Ottawa-Newcastle scale for observational studies and rated certainty of pooled evidence using GRADE. RESULTS: We separately pooled data from 16 RCTs (n=949) and 8 observational studies (n=396). Compared to facemask NIV, based on low certainty evidence, helmet NIV may reduce mortality (relative risk (RR) 0.56, 95% confidence interval (CI) (0.33 to 0.95)), and intubation (RR 0.35, 95% CI (0.22 to 0.56)) in both hypoxic and hypercapnic respiratory failure but may have no effect on duration of NIV. There was an uncertain effect of helmet on ICU length of stay and development of pressure sores. Data from observational studies was consistent with the foregoing findings but of lower certainty. Based on low and very low certainty data, helmet NIV may reduce intubation compared to HFNC, but its effect on mortality is uncertain. CONCLUSION: Compared to facemask NIV, helmet NIV may reduce mortality and intubation; however, the effect of helmet compared to HFNC remains uncertain.

3.
Front Physiol ; 12: 693736, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34349666

RESUMO

Transpulmonary driving pressure (DPL) corresponds to the cyclical stress imposed on the lung parenchyma during tidal breathing and, therefore, can be used to assess the risk of ventilator-induced lung injury (VILI). Its measurement at the bedside requires the use of esophageal pressure (Peso), which is sometimes technically challenging. Recently, it has been demonstrated how in an animal model of ARDS, the transpulmonary pressure (PL) measured with Peso calculated with the absolute values method (PL = Paw-Peso) is equivalent to the transpulmonary pressure directly measured using pleural sensors in the central-dependent part of the lung. We hypothesized that, since the PL derived from Peso reflects the regional behavior of the lung, it could exist a relationship between regional parameters measured by electrical impedance tomography (EIT) and driving PL (DPL). Moreover, we explored if, by integrating airways pressure data and EIT data, it could be possible to estimate non-invasively DPL and consequently lung elastance (EL) and elastance-derived inspiratory PL (PI). We analyzed 59 measurements from 20 patients with ARDS. There was a significant intra-patient correlation between EIT derived regional compliance in regions of interest (ROI1) (r = 0.5, p = 0.001), ROI2 (r = -0.68, p < 0.001), and ROI3 (r = -0.4, p = 0.002), and DPL. A multiple linear regression successfully predicted DPL based on respiratory system elastance (Ers), ideal body weight (IBW), roi1%, roi2%, and roi3% (R 2 = 0.84, p < 0.001). The corresponding Bland-Altmann analysis showed a bias of -1.4e-007 cmH2O and limits of agreement (LoA) of -2.4-2.4 cmH2O. EL and PI calculated using EIT showed good agreement (R 2 = 0.89, p < 0.001 and R 2 = 0.75, p < 0.001) with the esophageal derived correspondent variables. In conclusion, DPL has a good correlation with EIT-derived parameters in the central lung. DPL, PI, and EL can be estimated with good accuracy non-invasively combining information coming from EIT and airway pressure.

4.
Am J Respir Crit Care Med ; 204(8): 933-942, 2021 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-34252009

RESUMO

Rationale: Unilateral ligation of the pulmonary artery may induce lung injury through multiple mechanisms, which might be dampened by inhaled CO2. Objectives: This study aims to characterize bilateral lung injury owing to unilateral ligation of the pulmonary artery in healthy swine undergoing controlled mechanical ventilation and its prevention by 5% CO2 inhalation and to investigate relevant pathophysiological mechanisms. Methods: Sixteen healthy pigs were allocated to surgical ligation of the left pulmonary artery (ligation group), seven to surgical ligation of the left pulmonary artery and inhalation of 5% CO2 (ligation + FiCO2 5%), and six to no intervention (no ligation). Then, all animals received mechanical ventilation with Vt 10 ml/kg, positive end-expiratory pressure 5 cm H2O, respiratory rate 25 breaths/min, and FiO2 50% (±FiCO2 5%) for 48 hours or until development of severe lung injury. Measurements and Main Results: Histological, physiological, and quantitative computed tomography scan data were compared between groups to characterize lung injury. Electrical impedance tomography and immunohistochemistry analysis were performed in a subset of animals to explore mechanisms of injury. Animals from the ligation group developed bilateral lung injury as assessed by significantly higher histological score, larger increase in lung weight, poorer oxygenation, and worse respiratory mechanics compared with the ligation + FiCO2 5% group. In the ligation group, the right lung received a larger fraction of Vt and inflammation was more represented, whereas CO2 dampened both processes. Conclusions: Mechanical ventilation induces bilateral lung injury within 48 hours in healthy pigs undergoing left pulmonary artery ligation. Inhalation of 5% CO2 prevents injury, likely through decreased stress to the right lung and antiinflammatory effects.

5.
Intensive Care Med ; 47(8): 851-866, 2021 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-34232336

RESUMO

The role of non-invasive respiratory support (high-flow nasal oxygen and noninvasive ventilation) in the management of acute hypoxemic respiratory failure and acute respiratory distress syndrome is debated. The oxygenation improvement coupled with lung and diaphragm protection produced by non-invasive support may help to avoid endotracheal intubation, which prevents the complications of sedation and invasive mechanical ventilation. However, spontaneous breathing in patients with lung injury carries the risk that vigorous inspiratory effort, combined or not with mechanical increases in inspiratory airway pressure, produces high transpulmonary pressure swings and local lung overstretch. This ultimately results in additional lung damage (patient self-inflicted lung injury), so that patients intubated after a trial of noninvasive support are burdened by increased mortality. Reducing inspiratory effort by high-flow nasal oxygen or delivery of sustained positive end-expiratory pressure through the helmet interface may reduce these risks. In this physiology-to-bedside review, we provide an updated overview about the role of noninvasive respiratory support strategies as early treatment of hypoxemic respiratory failure in the intensive care unit. Noninvasive strategies appear safe and effective in mild-to-moderate hypoxemia (PaO2/FiO2 > 150 mmHg), while they can yield delayed intubation with increased mortality in a significant proportion of moderate-to-severe (PaO2/FiO2 ≤ 150 mmHg) cases. High-flow nasal oxygen and helmet noninvasive ventilation represent the most promising techniques for first-line treatment of severe patients. However, no conclusive evidence allows to recommend a single approach over the others in case of moderate-to-severe hypoxemia. During any treatment, strict physiological monitoring remains of paramount importance to promptly detect the need for endotracheal intubation and not delay protective ventilation.


Assuntos
Ventilação não Invasiva , Síndrome do Desconforto Respiratório , Insuficiência Respiratória , Humanos , Hipóxia/terapia , Intubação Intratraqueal , Oxigênio , Respiração com Pressão Positiva , Síndrome do Desconforto Respiratório/terapia , Insuficiência Respiratória/terapia
6.
Crit Care Explor ; 3(7): e0486, 2021 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-34278316

RESUMO

Positive end-expiratory pressure and tidal volume may have a key role for the outcome of patients with acute respiratory distress syndrome. The variety of acute respiratory distress syndrome phenotypes implies personalization of those settings. To guide personalized positive end-expiratory pressure and tidal volume, physicians need to have an in-depth understanding of the physiologic effects and bedside methods to measure the extent of these effects. In the present article, a step-by-step physiologic approach to select personalized positive end-expiratory pressure and tidal volume at the bedside is described. DATA SOURCES: The present review is a critical reanalysis of the traditional and latest literature on the topic. STUDY SELECTION: Relevant clinical and physiologic studies on positive end-expiratory pressure and tidal volume setting were reviewed. DATA EXTRACTION: Reappraisal of the available physiologic and clinical data. DATA SYNTHESIS: Positive end-expiratory pressure is aimed at stabilizing alveolar recruitment, thus reducing the risk of volutrauma and atelectrauma. Bedside assessment of the potential for lung recruitment is a preliminary step to recognize patients who benefit from higher positive end-expiratory pressure level. In patients with higher potential for lung recruitment, positive end-expiratory pressure could be selected by physiology-based methods balancing recruitment and overdistension. In patients with lower potential for lung recruitment or in shock, positive end-expiratory pressure could be maintained in the 5-8 cm H2O range. Tidal volume induces alveolar recruitment and improves gas exchange. After setting personalized positive end-expiratory pressure, tidal volume could be based on lung inflation (collapsed lung size) respecting safety thresholds of static and dynamic lung stress. Positive end-expiratory pressure and tidal volume could be kept stable for some hours in order to allow early recognition of changes in the clinical course of acute respiratory distress syndrome but also frequently reassessed to avoid crossing of safety thresholds. CONCLUSIONS: The setting of personalized positive end-expiratory pressure and tidal volume based on sound physiologic bedside measures may represent an effective strategy for treating acute respiratory distress syndrome patients.

7.
Crit Care ; 25(1): 192, 2021 06 03.
Artigo em Inglês | MEDLINE | ID: mdl-34082795

RESUMO

BACKGROUND: In acute respiratory distress syndrome (ARDS), non-ventilated perfused regions coexist with non-perfused ventilated regions within lungs. The number of unmatched regions might reflect ARDS severity and affect the risk of ventilation-induced lung injury. Despite pathophysiological relevance, unmatched ventilation and perfusion are not routinely assessed at the bedside. The aims of this study were to quantify unmatched ventilation and perfusion at the bedside by electrical impedance tomography (EIT) investigating their association with mortality in patients with ARDS and to explore the effects of positive end-expiratory pressure (PEEP) on unmatched ventilation and perfusion in subgroups of patients with different ARDS severity based on PaO2/FiO2 and compliance. METHODS: Prospective observational study in 50 patients with mild (36%), moderate (46%), and severe (18%) ARDS under clinical ventilation settings. EIT was applied to measure the regional distribution of ventilation and perfusion using central venous bolus of saline 5% during end-inspiratory pause. We defined unmatched units as the percentage of only ventilated units plus the percentage of only perfused units. RESULTS: Percentage of unmatched units was significantly higher in non-survivors compared to survivors (32[27-47]% vs. 21[17-27]%, p < 0.001). Percentage of unmatched units was an independent predictor of mortality (OR 1.22, 95% CI 1.07-1.39, p = 0.004) with an area under the ROC curve of 0.88 (95% CI 0.79-0.97, p < 0.001). The percentage of ventilation to the ventral region of the lung was higher than the percentage of ventilation to the dorsal region (32 [27-38]% vs. 18 [13-21]%, p < 0.001), while the opposite was true for perfusion (28 [22-38]% vs. 36 [32-44]%, p < 0.001). Higher percentage of only perfused units was correlated with lower dorsal ventilation (r = - 0.486, p < 0.001) and with lower PaO2/FiO2 ratio (r = - 0.293, p = 0.039). CONCLUSIONS: EIT allows bedside assessment of unmatched ventilation and perfusion in mechanically ventilated patients with ARDS. Measurement of unmatched units could identify patients at higher risk of death and could guide personalized treatment.


Assuntos
Impedância Elétrica/uso terapêutico , Perfusão/normas , Prognóstico , Respiração Artificial/normas , Síndrome do Desconforto Respiratório/complicações , Adulto , Idoso , Feminino , Humanos , Itália/epidemiologia , Masculino , Pessoa de Meia-Idade , Perfusão/métodos , Perfusão/estatística & dados numéricos , Estudos Prospectivos , Respiração Artificial/métodos , Respiração Artificial/estatística & dados numéricos , Síndrome do Desconforto Respiratório/epidemiologia , Síndrome do Desconforto Respiratório/mortalidade , Escala Psicológica Aguda Simplificada
8.
Front Physiol ; 12: 663313, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-33897471

RESUMO

Rationale: Reducing the respiratory rate during extracorporeal membrane oxygenation (ECMO) decreases the mechanical power, but it might induce alveolar de-recruitment. Dissecting de-recruitment due to lung edema vs. the fraction due to hypoventilation may be challenging in injured lungs. Objectives: We characterized changes in lung physiology (primary endpoint: development of atelectasis) associated with progressive reduction of the respiratory rate in healthy animals on ECMO. Methods: Six female pigs underwent general anesthesia and volume control ventilation (Baseline: PEEP 5 cmH2O, Vt 10 ml/kg, I:E = 1:2, FiO2 0.5, rate 24 bpm). Veno-venous ECMO was started and respiratory rate was progressively reduced to 18, 12, and 6 breaths per minute (6-h steps), while all other settings remained unchanged. ECMO blood flow was kept constant while gas flow was increased to maintain stable PaCO2. Measurements and Main Results: At Baseline (without ECMO) and toward the end of each step, data from quantitative CT scan, electrical impedance tomography, and gas exchange were collected. Increasing ECMO gas flow while lowering the respiratory rate was associated with an increase in the fraction of non-aerated tissue (i.e., atelectasis) and with a decrease of tidal ventilation reaching the gravitationally dependent lung regions (p = 0.009 and p = 0.018). Intrapulmonary shunt increased (p < 0.001) and arterial PaO2 decreased (p < 0.001) at lower rates. The fraction of non-aerated lung was correlated with longer expiratory time spent at zero flow (r = 0.555, p = 0.011). Conclusions: Progressive decrease of respiratory rate coupled with increasing CO2 removal in mechanically ventilated healthy pigs is associated with development of lung atelectasis, higher shunt, and poorer oxygenation.

9.
Br J Anaesth ; 127(1): 143-152, 2021 07.
Artigo em Inglês | MEDLINE | ID: mdl-33892948

RESUMO

BACKGROUND: Bilateral lung transplantation results in pulmonary vagal denervation, which potentially alters respiratory drive, volume-feedback, and ventilatory pattern. We hypothesised that Neurally Adjusted Ventilatory Assist (NAVA) ventilation, which is driven by diaphragm electrical activity (EAdi), would reveal whether vagally mediated pulmonary-volume feedback is preserved in the early phases after bilateral lung transplantation. METHODS: We prospectively studied bilateral lung transplant recipients within 48 h of surgery. Subjects were ventilated with NAVA and randomised to receive 3 ventilatory modes (baseline NAVA, 50%, and 150% of baseline NAVA values) and 2 PEEP levels (6 and 12 cm H2O). We recorded airway pressure, flow, and EAdi. RESULTS: We studied 30 subjects (37% female; age: 37 (27-56) yr), of whom 19 (63%) had stable EAdi. The baseline NAVA level was 0.6 (0.2-1.0) cm H2O µV-1. Tripling NAVA level increased the ventilatory peak pressure over PEEP by 6.3 (1.8), 7.6 (2.4), and 8.7 (3.2) cm H2O, at 50%, 100%, and 150% of baseline NAVA level, respectively (P<0.001). EAdi peak decreased by 10.1 (9.0), 9.5 (9.4) and 8.8 µV (8.7) (P<0.001), accompanied by small increases in tidal volume, 8.3 (3.0), 8.7 (3.6), and 8.9 (3.3) ml kg-1 donor's predicted body weight at 50%, 100%, and 150% of baseline NAVA levels, respectively (P<0.001). Doubling PEEP did not affect tidal volume. CONCLUSIONS: NAVA ventilation was feasible in the majority of patients during the early postoperative period after bilateral lung transplantation. Despite surgical vagotomy distal to the bronchial anastomoses, bilateral lung transplant recipients maintained an unmodified respiratory pattern in response to variations in ventilatory assistance and PEEP. CLINICAL TRIAL REGISTRATION: NCT03367221.


Assuntos
Retroalimentação , Suporte Ventilatório Interativo/métodos , Transplante de Pulmão/métodos , Respiração com Pressão Positiva/métodos , Cuidados Pós-Operatórios/métodos , Volume de Ventilação Pulmonar/fisiologia , Adulto , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Estudos Prospectivos , Ventilação Pulmonar/fisiologia , Desmame do Respirador/métodos
11.
Crit Care Med ; 49(2): e208-e209, 2021 02 01.
Artigo em Inglês | MEDLINE | ID: mdl-33438986
12.
J Crit Care ; 61: 125-132, 2021 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-33157308

RESUMO

PURPOSE: Optimal esophageal balloon filling volume (Vbest) depends on the intrathoracic pressure. During Sigh breath delivered by the ventilator machine, esophageal balloon is surrounded by elevated intrathoracic pressure that might require higher filling volume for accurate measure of tidal changes in esophageal pressure (Pes). The primary aim of our investigation was to evaluate and compare Vbest during volume controlled and pressure support breaths vs. Sigh breath. MATERIALS AND METHODS: Twenty adult patients requiring invasive volume-controlled ventilation (VCV) for hypoxemic acute respiratory failure were enrolled. After the insertion of a naso-gastric catheter equipped with 10 ml esophageal balloon, each patient underwent three 30-min trials as follows: VCV, pressure support ventilation (PSV), and PSV + Sigh. Sigh was added to PSV as 35 cmH2O pressure-controlled breath over 4 s, once per minute. PSV and PSV + Sigh were randomly applied and, at the end of each step, esophageal balloon calibration was performed. RESULTS: Vbest was higher for Sigh breath (4.5 [3.0-6.8] ml) compared to VCV (1.5 [1.0-2.9] ml, P = 0.0004) and PSV tidal breath (1.0 [0.5-2.4] ml, P < 0.0001). CONCLUSIONS: During Sigh breath, applying a calibrated approach for Pes assessment, a higher Vbest was required compared to VCV and PSV tidal breath.

13.
Chest ; 159(4): 1426-1436, 2021 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-33197403

RESUMO

BACKGROUND: Sigh is a cyclic brief recruitment maneuver: previous physiologic studies showed that its use could be an interesting addition to pressure support ventilation to improve lung elastance, decrease regional heterogeneity, and increase release of surfactant. RESEARCH QUESTION: Is the clinical application of sigh during pressure support ventilation (PSV) feasible? STUDY DESIGN AND METHODS: We conducted a multicenter noninferiority randomized clinical trial on adult intubated patients with acute hypoxemic respiratory failure or ARDS undergoing PSV. Patients were randomized to the no-sigh group and treated by PSV alone, or to the sigh group, treated by PSV plus sigh (increase in airway pressure to 30 cm H2O for 3 s once per minute) until day 28 or death or successful spontaneous breathing trial. The primary end point of the study was feasibility, assessed as noninferiority (5% tolerance) in the proportion of patients failing assisted ventilation. Secondary outcomes included safety, physiologic parameters in the first week from randomization, 28-day mortality, and ventilator-free days. RESULTS: Two-hundred and fifty-eight patients (31% women; median age, 65 [54-75] years) were enrolled. In the sigh group, 23% of patients failed to remain on assisted ventilation vs 30% in the no-sigh group (absolute difference, -7%; 95% CI, -18% to 4%; P = .015 for noninferiority). Adverse events occurred in 12% vs 13% in the sigh vs no-sigh group (P = .852). Oxygenation was improved whereas tidal volume, respiratory rate, and corrected minute ventilation were lower over the first 7 days from randomization in the sigh vs no-sigh group. There was no significant difference in terms of mortality (16% vs 21%; P = .337) and ventilator-free days (22 [7-26] vs 22 [3-25] days; P = .300) for the sigh vs no-sigh group. INTERPRETATION: Among hypoxemic intubated ICU patients, application of sigh was feasible and without increased risk. TRIAL REGISTRY: ClinicalTrials.gov; No.: NCT03201263; URL: www.clinicaltrials.gov.

14.
Intensive Care Med ; 46(12): 2226-2237, 2020 12.
Artigo em Inglês | MEDLINE | ID: mdl-33201321

RESUMO

PURPOSE: High flow nasal cannula (HFNC) is a relatively recent respiratory support technique which delivers high flow, heated and humidified controlled concentration of oxygen via the nasal route. Recently, its use has increased for a variety of clinical indications. To guide clinical practice, we developed evidence-based recommendations regarding use of HFNC in various clinical settings. METHODS: We formed a guideline panel composed of clinicians, methodologists and experts in respiratory medicine. Using GRADE, the panel developed recommendations for four actionable questions. RESULTS: The guideline panel made a strong recommendation for HFNC in hypoxemic respiratory failure compared to conventional oxygen therapy (COT) (moderate certainty), a conditional recommendation for HFNC following extubation (moderate certainty), no recommendation regarding HFNC in the peri-intubation period (moderate certainty), and a conditional recommendation for postoperative HFNC in high risk and/or obese patients following cardiac or thoracic surgery (moderate certainty). CONCLUSIONS: This clinical practice guideline synthesizes current best-evidence into four recommendations for HFNC use in patients with hypoxemic respiratory failure, following extubation, in the peri-intubation period, and postoperatively for bedside clinicians.


Assuntos
Ventilação não Invasiva , Insuficiência Respiratória , Adulto , Extubação , Cânula , Humanos , Oxigênio , Oxigenoterapia , Insuficiência Respiratória/terapia
15.
Intensive Care Med ; 46(12): 2314-2326, 2020 12.
Artigo em Inglês | MEDLINE | ID: mdl-33140181

RESUMO

Mechanical ventilation may have adverse effects on both the lung and the diaphragm. Injury to the lung is mediated by excessive mechanical stress and strain, whereas the diaphragm develops atrophy as a consequence of low respiratory effort and injury in case of excessive effort. The lung and diaphragm-protective mechanical ventilation approach aims to protect both organs simultaneously whenever possible. This review summarizes practical strategies for achieving lung and diaphragm-protective targets at the bedside, focusing on inspiratory and expiratory ventilator settings, monitoring of inspiratory effort or respiratory drive, management of dyssynchrony, and sedation considerations. A number of potential future adjunctive strategies including extracorporeal CO2 removal, partial neuromuscular blockade, and neuromuscular stimulation are also discussed. While clinical trials to confirm the benefit of these approaches are awaited, clinicians should become familiar with assessing and managing patients' respiratory effort, based on existing physiological principles. To protect the lung and the diaphragm, ventilation and sedation might be applied to avoid excessively weak or very strong respiratory efforts and patient-ventilator dysynchrony.


Assuntos
Diafragma , Respiração , Humanos , Pulmão , Respiração Artificial/efeitos adversos , Ventiladores Mecânicos
16.
Crit Care ; 24(1): 654, 2020 11 23.
Artigo em Inglês | MEDLINE | ID: mdl-33225971

RESUMO

BACKGROUND: Nasal high flow delivered at flow rates higher than 60 L/min in patients with acute hypoxemic respiratory failure might be associated with improved physiological effects. However, poor comfort might limit feasibility of its clinical use. METHODS: We performed a prospective randomized cross-over physiological study on 12 ICU patients with acute hypoxemic respiratory failure. Patients underwent three steps at the following gas flow: 0.5 L/kg PBW/min, 1 L/kg PBW/min, and 1.5 L/kg PBW/min in random order for 20 min. Temperature and FiO2 remained unchanged. Toward the end of each phase, we collected arterial blood gases, lung volumes, and regional distribution of ventilation assessed by electrical impedance tomography (EIT), and comfort. RESULTS: In five patients, the etiology was pulmonary; infective disease characterized seven patients; median PaO2/FiO2 at enrollment was 213 [IQR 136-232]. The range of flow rate during NHF 1.5 was 75-120 L/min. PaO2/FiO2 increased with flow, albeit non significantly (p = 0.064), PaCO2 and arterial pH remained stable (p = 0.108 and p = 0.105). Respiratory rate decreased at higher flow rates (p = 0.014). Inhomogeneity of ventilation decreased significantly at higher flows (p = 0.004) and lung volume at end-expiration significantly increased (p = 0.007), but mostly in the non-dependent regions. Comfort was significantly poorer during the step performed at the highest flow (p < 0.001). CONCLUSIONS: NHF delivered at rates higher than 60 L/min in critically ill patients with acute hypoxemic respiratory failure is associated with reduced respiratory rate, increased lung homogeneity, and additional positive pressure effect, but also with worse comfort.

17.
Crit Care ; 24(1): 622, 2020 10 22.
Artigo em Inglês | MEDLINE | ID: mdl-33092607

RESUMO

BACKGROUND: The physiological behavior of lungs affected by the acute respiratory distress syndrome (ARDS) differs between inspiration and expiration and presents heterogeneous gravity-dependent distribution. This phenomenon, highlighted by the different distribution of opening/closing pressure and by the hysteresis of the pressure-volume curve, can be studied by CT scan, but the technique expose the patient to radiations, cannot track changes during time and is not feasible at the bedside. Electrical impedance tomography (EIT) could help in assessing at the bedside regional inspiratory and expiratory mechanical properties. We evaluated regional opening/closing pressures, hysteresis and atelectrauma during inspiratory and expiratory low-flow pressure-volume curves in ARDS using electrical impedance tomography. METHODS: Pixel-level inspiratory and expiratory PV curves (PVpixel) between 5 and 40 cmH2O were constructed integrating EIT images and airway opening pressure signal from 8 ARDS patients. The lower inflection point in the inspiratory and expiratory PVpixel were used to find opening (OPpixel) and closing (CPpixel) pressures. A novel atelectrauma index (AtI) was calculated as the percentage of pixels opening during the inspiratory and closing during the expiratory PV curves. The maximal hysteresis (HysMax) was calculated as the maximal difference between normalized expiratory and inspiratory PV curves. Analyses were conducted in the global, dependent and non-dependent lung regions. RESULTS: Gaussian distribution was confirmed for both global OPpixel (r2 = 0.90) and global CPpixel (r2 = 0.94). The two distributions were significantly different with higher values for OPpixel (p < 0.0001). Regional OPpixel and CPpixel distributions were Gaussian, and in the dependent lung regions, both were significantly higher than in the non-dependent ones (p < 0.001). Both AtI and the HysMax were significantly higher in the dependent regions compared to the non-dependent ones (p < 0.05 for both). CONCLUSIONS: Gravity impacts the regional distribution of opening and closing pressure, hysteresis and atelectrauma, with higher values in the dorsal lung. Regional differences between inspiratory and expiratory lung physiology are detectable at the bedside using EIT and could allow in-depth characterization of ARDS phenotypes and guide personalized ventilation settings.


Assuntos
Impedância Elétrica , Síndrome do Desconforto Respiratório/diagnóstico por imagem , Tomografia Computadorizada por Raios X/métodos , Idoso , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Pressão , Fenômenos Fisiológicos Respiratórios
18.
Crit Care Med ; 48(11): e1129-e1136, 2020 11.
Artigo em Inglês | MEDLINE | ID: mdl-32947472

RESUMO

OBJECTIVES: Reintubation after failed extubation is associated with increased mortality and longer hospital length of stay. Noninvasive oxygenation modalities may prevent reintubation. We conducted a systematic review and meta-analysis to determine the safety and efficacy of high-flow nasal cannula after extubation in critically ill adults. DATA SOURCES: We searched MEDLINE, EMBASE, and Web of Science. STUDY SELECTION: We included randomized controlled trials comparing high-flow nasal cannula to other noninvasive methods of oxygen delivery after extubation in critically ill adults. DATA EXTRACTION: We included the following outcomes: reintubation, postextubation respiratory failure, mortality, use of noninvasive ventilation, ICU and hospital length of stay, complications, and comfort. DATA SYNTHESIS: We included eight randomized controlled trials (n = 1,594 patients). Compared with conventional oxygen therapy, high-flow nasal cannula decreased reintubation (relative risk, 0.46; 95% CI, 0.30-0.70; moderate certainty) and postextubation respiratory failure (relative risk, 0.52; 95% CI, 0.30-0.91; very low certainty), but had no effect on mortality (relative risk, 0.93; 95% CI, 0.57-1.52; moderate certainty), or ICU length of stay (mean difference, 0.05 d fewer; 95% CI, 0.83 d fewer to 0.73 d more; high certainty). High-flow nasal cannula may decrease use of noninvasive ventilation (relative risk, 0.64; 95% CI, 0.34-1.22; moderate certainty) and hospital length of stay (mean difference, 0.98 d fewer; 95% CI, 2.16 d fewer to 0.21 d more; moderate certainty) compared with conventional oxygen therapy, however, certainty was limited by imprecision. Compared with noninvasive ventilation, high-flow nasal cannula had no effect on reintubation (relative risk, 1.16; 95% CI, 0.86-1.57; low certainty), mortality (relative risk, 1.12; 95% CI, 0.82-1.53; moderate certainty), or postextubation respiratory failure (relative risk, 0.82; 95% CI, 0.48-1.41; very low certainty). High-flow nasal cannula may reduce ICU length of stay (moderate certainty) and hospital length of stay (moderate certainty) compared with noninvasive ventilation. CONCLUSIONS: High-flow nasal cannula reduces reintubation compared with conventional oxygen therapy, but not compared with noninvasive ventilation after extubation.


Assuntos
Cânula , Ventilação não Invasiva , Oxigenoterapia , Extubação , Humanos , Ventilação não Invasiva/métodos , Oxigênio/administração & dosagem
20.
Crit Care Med ; 48(8): 1129-1134, 2020 08.
Artigo em Inglês | MEDLINE | ID: mdl-32697482

RESUMO

OBJECTIVES: Severe cases of coronavirus disease 2019 develop the acute respiratory distress syndrome, requiring admission to the ICU. This study aimed to describe specific pathophysiological characteristics of acute respiratory distress syndrome from coronavirus disease 2019. DESIGN: Prospective crossover physiologic study. SETTING: ICU of a university-affiliated hospital from northern Italy dedicated to care of patients with confirmed diagnosis of coronavirus disease 2019. PATIENTS: Ten intubated patients with acute respiratory distress syndrome and confirmed diagnosis of coronavirus disease 2019. INTERVENTIONS: We performed a two-step positive end-expiratory pressure trial with change of 10 cm H2O in random order. MEASUREMENTS AND MAIN RESULTS: At each positive end-expiratory pressure level, we assessed arterial blood gases, respiratory mechanics, ventilation inhomogeneity, and potential for lung recruitment by electrical impedance tomography. Potential for lung recruitment was assessed by the recently described recruitment to inflation ratio. In a subgroup of seven paralyzed patients, we also measured ventilation-perfusion mismatch at lower positive end-expiratory pressure by electrical impedance tomography. At higher positive end-expiratory pressure, respiratory mechanics did not change significantly: compliance remained relatively high with low driving pressure. Oxygenation and ventilation inhomogeneity improved but arterial CO2 increased despite unchanged respiratory rate and tidal volume. The recruitment to inflation ratio presented median value higher than previously reported in acute respiratory distress syndrome patients but with large variability (median, 0.79 [0.53-1.08]; range, 0.16-1.40). The FIO2 needed to obtain viable oxygenation at lower positive end-expiratory pressure was significantly correlated with the recruitment to inflation ratio (r = 0.603; p = 0.05). The ventilation-perfusion mismatch was elevated (median, 34% [32-45%] of lung units) and, in six out of seven patients, ventilated nonperfused units represented a much larger proportion than perfused nonventilated ones. CONCLUSIONS: In patients with acute respiratory distress syndrome from coronavirus disease 2019, potential for lung recruitment presents large variability, while elevated dead space fraction may be a specific pathophysiological trait. These findings may guide selection of personalized mechanical ventilation settings.


Assuntos
Betacoronavirus , Infecções por Coronavirus/complicações , Pneumonia Viral/complicações , Respiração com Pressão Positiva/métodos , Síndrome do Desconforto Respiratório/terapia , Adulto , Idoso , Idoso de 80 Anos ou mais , Gasometria , COVID-19 , Estudos Cross-Over , Feminino , Hospitais Universitários , Humanos , Itália , Masculino , Pessoa de Meia-Idade , Oxigênio/sangue , Pandemias , Estudos Prospectivos , Síndrome do Desconforto Respiratório/etiologia , Síndrome do Desconforto Respiratório/fisiopatologia , Mecânica Respiratória , SARS-CoV-2
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