La ventilation non invasive dans l'insuffisance respiratoire aiguë : de la broncho-pneumonie chronique obstructive au syndrome de détresse respiratoire aiguë

RESUME : L'application d'une ventilation non-invasive (VNI) à pression positive chez des patients avec une insuffisance respiratoire aiguë hypoxémique non liée à une broncho-pneumopathie chronique obstructive (BPCO), reste controversée malgré les résultats encourageants apparus dans de récentes études. Ce travail de thèse est composé d'une introduction qui comprend un historique de la VNI et une revue de ces applications principales dans l'insuffisance respiratoire aiguë avec, en particulier, une analyse des études cliniques principales concernant son utilisation dans l'exacerbation de la BPCO, dans l'asthme aigu sévère, dans les syndromes restrictifs et dans l'insuffisance respiratoire aiguë hypoxémique. La première partie aborde également les aspects pratiques de l'utilisation de la VNI, avec une description de l'équipement et des techniques utilisées. Ce travail de thèse a ensuite pour but d'analyser dans une étude personnelle l'application d'une VNI à pression positive chez des patients avec une insuffisance respiratoire aiguë hypoxémique non liée à une BPCO. Il s'agit d'une étude prospective et observationnelle, dans laquelle nous avons voulu analyser l'efficacité de la VNI chez un groupe de patients sélectionnés et coopérants, stables du point de vue hémodynamique, présentant un syndrome de détresse respiratoire aiguë (SDRA) primaire (atteinte pulmonaire directe). Les échanges gazeux, le taux d'intubation, la mortalité et la durée de séjour dans l'unité de soins intensifs ont été enregistrés. Dans notre travail, la VNI a été appliquée de manière prospective à 12 patients, stables du point de vue hémodynamique, présentant les critères diagnostiques pour un SDRA primaire (SDRAP) et une indication pour une ventilation mécanique classique. Leur évolution a été comparée avec celle d'un groupe contrôle de 12 patients avec SDRAP. et précédemment traités dans la même unité de soins intensifs, ayant des caractéristiques similaires à l'admission : âge, score SAPS II, rapport Pa02/Fi02 et valeurs de pH . Un échec de la VNI fut observé chez 4 patients (33%), tous bactériémiques et nécessitant une intubation endotrachéale. Un facteur prédictif négatif. Les patients traités avec succès ont présenté un temps cumulatif de ventilation (p=0.001) et une durée de séjour aux soins intensifs (p=0.004) inférieure à ceux du groupe contrôle. Pendant la première période d'observation de la ventilation, l'oxygénation après 60 minutes s'est améliorée de manière plus importante dans le groupe VNI par rapport au groupe contrôle (PaO2/FiO2 : 146 +/- 52 mmHg vs. 109 +/- 34 mmHg ; p=0.05). Le taux de mortalité globale aux soins intensifs ne fut pas différent entre le groupe VNI et le groupe de patients intubés. Le taux de complications graves fut plus élevé chez les patients du groupe contrôle. Nos résultats suggèrent que chez des patients stables et coopérants, avec une pneumonie étendue, sans bactériémie à l'admission et remplissant les critères diagnostiques d'un SDRAp, la VNI représente une alternative valable à l'intubation endotrachéale.

Neurally Adjusted Ventilatory Assist (NAVA) improves the matching of diaphragmatic electrical activity and tidal volume in comparison to pressure support (PS) under non invasive ventilation

INTRODUCTION. Patient-ventilator asynchrony is a frequent issue in non invasivemechanical ventilation (NIV) and leaks at the patient-mask interface play a major role in itspathogenesis. NIV algorithms alleviate the deleterious impact of leaks and improve patient-ventilator interaction. Neurally adusted ventilatory assist (NAVA), a neurally triggered modethat avoids interferences between leaks and the usual pneumatic trigger, could further improvepatient-ventilator interaction in NIV patients.OBJECTIVES. To evaluate the feasibility ofNAVAin patients receiving a prophylactic postextubationNIV and to compare the respective impact ofPSVandNAVAwith and withoutNIValgorithm on patient-ventilator interaction.METHODS. Prospective study conducted in 16 beds adult critical care unit (ICU) in a tertiaryuniversity hospital. Over a 2 months period, were included 17 adult medical ICU patientsextubated for less than 2 h and in whom a prophylactic post-extubation NIV was indicated.Patients were randomly mechanically ventilated for 10 min with: PSV without NIV algorithm(PSV-NIV-), PSV with NIV algorithm (PSV-NIV+),NAVAwithout NIV algorithm (NAVANIV-)and NAVA with NIV algorithm (NAVA-NIV+). Breathing pattern descriptors, diaphragmelectrical activity, leaks volume, inspiratory trigger delay (Tdinsp), inspiratory time inexcess (Tiexcess) and the five main asynchronies were quantified. Asynchrony index (AI) andasynchrony index influenced by leaks (AIleaks) were computed.RESULTS. Peak inspiratory pressure and diaphragm electrical activity were similar in thefour conditions. With both PSV and NAVA, NIV algorithm significantly reduced the level ofleak (p\0.01). Tdinsp was not affected by NIV algorithm but was shorter in NAVA than inPSV (p\0.01). Tiexcess was shorter in NAVA and PSV-NIV+ than in PSV-NIV- (p\0.05).The prevalence of double triggering was significantly lower in PSV-NIV+ than in NAVANIV+.As compared to PSV,NAVAsignificantly reduced the prevalence of premature cyclingand late cycling while NIV algorithm did not influenced premature cycling. AI was not affectedby NIV algorithm but was significantly lower in NAVA than in PSV (p\0.05). AIleaks wasquasi null with NAVA and significantly lower than in PSV (p\0.05).CONCLUSIONS. NAVA is feasible in patients receiving a post-extubation prophylacticNIV. NAVA and NIV improve patient-ventilator synchrony in different manners. NAVANIV+offers the best patient-ventilator interaction. Clinical studies are required to assess thepotential clinical benefit of NAVA in patients receiving NIV.

Noninvasive functional and structural exploration of human subcortical structures with high resolution

Projecte de recerca elaborat a partir d’una estada al Max Planck Institute for Human Cognitive and Brain Sciences, Alemanya, entre 2010 i 2012. El principal objectiu d’aquest projecte era estudiar en detall les estructures subcorticals, en concret, el rol dels ganglis basals en control cognitiu durant processament lingüístic i no-lingüístic. Per tal d’assolir una diferenciació minuciosa en els diferents nuclis dels ganglis basals s’utilitzà ressonància magnètica d’ultra-alt camp i alta resolució (7T-MRI). El còrtex prefrontal lateral i els ganglis basals treballant conjuntament per a mitjançar memòria de treball i la regulació “top-down” de la cognició. Aquest circuit regula l’equilibri entre respostes automàtiques i d’alt-ordre cognitiu. Es crearen tres condicions experimentals principals: frases/seqüències noambigües, no-gramatical i ambigües. Les frases/seqüències no-ambigües haurien de provocar una resposta automàtica, mentre les frases/seqüències ambigües i no-gramaticals produïren un conflicte amb la resposta automàtica, i per tant, requeririen una resposta de d’alt-ordre cognitiu. Dins del domini de la resposta de control, la ambigüitat i no-gramaticalitat representen dues dimensions diferents de la resolució de conflicte, mentre per una frase/seqüència temporalment ambigua existeix una interpretació correcte, aquest no és el cas per a les frases/seqüències no-gramaticals. A més, el disseny experimental incloïa una manipulació lingüística i nolingüística, la qual posà a prova la hipòtesi que els efectes són de domini-general; així com una manipulació semàntica i sintàctica que avaluà les diferències entre el processament d’ambigüitat/error “intrínseca” vs. “estructural”. Els resultats del primer experiment (sintax-lingüístic) mostraren un gradient rostroventralcaudodorsal de control cognitiu dins del nucli caudat, això és, les regions més rostrals sostenint els nivells més alts de processament cognitiu

Noninvasive visualization of coronary artery endothelial function in healthy subjects and in patients with coronary artery disease.

OBJECTIVES: The goal was to test 2 hypotheses: first, that coronary endothelial function can be measured noninvasively and abnormal function detected using clinical 3.0-T magnetic resonance imaging (MRI); and second, that the extent of local coronary artery disease (CAD), in a given patient, is related to the degree of local abnormal coronary endothelial function. BACKGROUND: Abnormal endothelial function mediates the initiation and progression of atherosclerosis and predicts cardiovascular events. However, direct measures of coronary endothelial function have required invasive assessment. METHODS: The MRI was performed in 20 healthy adults and 17 patients with CAD. Cross-sectional coronary area and blood flow were quantified before and during isometric handgrip exercise, an endothelial-dependent stressor. In 10 severe, single-vessel CAD patients, paired endothelial function was measured in the artery with severe stenosis and the contralateral artery with minimal disease. RESULTS: In healthy adults, coronary arteries dilated and flow increased with stress. In CAD patients, coronary artery area and blood flow decreased with stress (both p </= 0.02). In the paired study, coronary artery area and blood flow failed to increase during exercise in the mildly diseased vessel, but both area (p = 0.01) and blood flow (p = 0.02) decreased significantly in the severely diseased, contralateral artery. CONCLUSIONS: Endothelial-dependent coronary artery dilation and increased blood flow in healthy subjects, and their absence in CAD patients, can now be directly visualized and quantified noninvasively. Local coronary endothelial function differs between severely and mildly diseased arteries in a given CAD patient. This novel, safe method may offer new insights regarding the importance of local coronary endothelial function and improved risk stratification in patients at risk for and with known CAD.

Mechanical ventilation and clinical practice heterogeneity in intensive care units: a multicenter case-vignette study.

BACKGROUND: Observational studies on mechanical ventilation (MV) show practice variations across ICUs. We sought to determine, with a case-vignette study, the heterogeneity of processes of care in ICUs focusing on mechanical ventilation procedures, and whether organizational patterns or physician characteristics influence practice variations. METHODS: We conducted a cross-sectional multicenter study using the case-vignette methodology. Descriptive analyses were calculated for each organizational pattern and respondent characteristics. An Index of Qualitative Variation (IQV, from 0, no heterogeneity, to a maximum of 1) was calculated. RESULTS: Forty ICUs from France (N = 33) and Switzerland (N = 7) participated; 396 physicians answered our case-vignettes. There was major heterogeneity of management processes related to MV within and across centers (mean IQV per center 0.51, SD 0.09). We observed the lowest variability (mean IQV per question < 0.4) for questions related to intubation procedure, ventilation of acute respiratory distress syndrome and the use of the semirecumbent position. We observed a high variability (mean IQV per question > 0.6) for questions related to management of endotracheal tube or suctioning, management of sedation and analgesia, and respect of autonomy. Heterogeneity was independent of respondent characteristics and of the presence of written procedures. There was a correlation between the processes associated with the highest variability (mean IQV per question > 0.6) and the annual volume of ICU admission (r = 0.32 (0.01 to 0.58)) and MV (r = 0.38 (0.07 to 0.63)). Within ICUs there was a large heterogeneity regarding knowledge of a local written procedure. CONCLUSIONS: Large clinical practice variations were found among ICUs. High volume centers were more likely to have heterogeneous practices. The presence of a local written procedure or respondent characteristics did not influence practice variation.

The automatic selection of ventilation parameters during the initial phase of mechanical ventilation.

OBJECTIVE: To test a method that allows automatic set-up of the ventilator controls at the onset of ventilation. DESIGN: Prospective randomized crossover study. SETTING: ICUs in one adult and one children's hospital in Switzerland. PATIENTS: Thirty intubated stable, critically ill patients (20 adults and 10 children). INTERVENTIONS: The patients were ventilated during two 20-min periods using a modified Hamilton AMADEUS ventilator. During the control period the ventilator settings were chosen immediately prior to the study. During the other period individual settings were automatically determined by the ventilatior (AutoInit). MEASUREMENTS AND RESULTS: Pressure, flow, and instantaneous CO2 concentration were measured at the airway opening. From these measurements, series dead space (V(DS)), expiratory time constant (RC), tidal volume (VT, total respiratory frequency (f(tot), minute ventilation (MV), and maximal and mean airway pressure (Paw, max and Paw, mean) were calculated. Arterial blood gases were analyzed at the end of each period. Paw, max was significantly less with the AutoInit ventilator settings while f(tot) was significantly greater (P < 0.05). The other values were not statistically significant. CONCLUSIONS: The AutoInit ventilator settings, which were automatically derived, were acceptable for all patients for a period of 20 min and were not found to be inferior to the control ventilator settings. This makes the AutoInit method potentially useful as an automatic start-up procedure for mechanical ventilation.

Influence of the quality of nursing on the duration of weaning from mechanical ventilation in patients with chronic obstructive pulmonary disease.

OBJECTIVE: To evaluate the influence of nursing on the duration of weaning from mechanical ventilation in patients with chronic obstructive pulmonary disease. DESIGN: Data were collected prospectively over a 1-yr period (study year) and compared with previously collected prospective data recorded in our chronic obstructive pulmonary disease database during a 5-yr period. SETTING: The medical intensive care unit (ICU) of a university hospital. PATIENTS: Eighty-seven patients with chronic obstructive pulmonary disease. Fifteen patients had chronic obstructive pulmonary disease that required mechanical ventilation for acute exacerbation of their disease (study year), and 72 were patients with chronic obstructive pulmonary disease from the previously collected data. INTERVENTIONS: The ICU course (duration of mechanical ventilation, mortality) was recorded, as well as several respiratory parameters (pulmonary function tests and arterial blood gases in stable conditions, and nutritional status), and they were compared with an "index of nursing." MEASUREMENTS AND MAIN RESULTS: We developed an "index of nursing", comparing the effective workforce of the nurses (number and qualifications) with the ideal workforce required by the number of patients and the severity of their diseases. A value of 1.0 represented a perfect match between the needed and the effectively present nurses, whereas a lesser value signified a diminished available workforce. This index was compared with the complications and duration of weaning from mechanical ventilation. During the first 5 yrs, the duration of mechanical ventilation increased progressively from 7.3 +/- 8.0 to 38.2 +/- 25.8 days (p = .006). A significant inverse correlation between the duration of mechanical ventilation and the nursing index (p = .025) was found. In the sixth comparative year, the number of nurses increased (nursing index = 1.05) and the duration of mechanical ventilation decreased to 9.9 +/- 13 days (p < .001, yr 5 vs. yr 6). CONCLUSIONS: The quality of nursing appears to be a measurable and critical factor in the weaning from mechanical ventilation of patients with chronic obstructive pulmonary disease. Below a threshold in the available workforce of ICU nurses, the weaning duration of patients with chronic obstructive pulmonary disease increases dramatically. Therefore, very close attention should be given to the education and number of ICU nurses.

Trabecular bone score: a noninvasive analytical method based upon the DXA image.

The trabecular bone score (TBS) is a gray-level textural metric that can be extracted from the two-dimensional lumbar spine dual-energy X-ray absorptiometry (DXA) image. TBS is related to bone microarchitecture and provides skeletal information that is not captured from the standard bone mineral density (BMD) measurement. Based on experimental variograms of the projected DXA image, TBS has the potential to discern differences between DXA scans that show similar BMD measurements. An elevated TBS value correlates with better skeletal microstructure; a low TBS value correlates with weaker skeletal microstructure. Lumbar spine TBS has been evaluated in cross-sectional and longitudinal studies. The following conclusions are based upon publications reviewed in this article: 1) TBS gives lower values in postmenopausal women and in men with previous fragility fractures than their nonfractured counterparts; 2) TBS is complementary to data available by lumbar spine DXA measurements; 3) TBS results are lower in women who have sustained a fragility fracture but in whom DXA does not indicate osteoporosis or even osteopenia; 4) TBS predicts fracture risk as well as lumbar spine BMD measurements in postmenopausal women; 5) efficacious therapies for osteoporosis differ in the extent to which they influence the TBS; 6) TBS is associated with fracture risk in individuals with conditions related to reduced bone mass or bone quality. Based on these data, lumbar spine TBS holds promise as an emerging technology that could well become a valuable clinical tool in the diagnosis of osteoporosis and in fracture risk assessment.

Clinical characteristics and outcome of patients admitted to a medico-surgical ICU requiring non invasive ventilation (NIV) for hypercapnic respiratory failure

Introduction: Because it decreases intubation rate and mortality, NIV has become first-line treatment in case of hypercapnic respiratory failure (HRF). Whether this approach is equally successful for all categories of HRF patients is however debated. We assessed if any clinical characteristics of HRF patients were associated with NIV intensity, success, and outcome, in order to identify prognostic factors. Methods: Retrospective analysis of the clinical database (clinical information system and MDSi) of patients consecutively admitted to our medico-surgical ICU, presenting with HRF (defined as PaCO2 >50 mm Hg), and receiving NIV between January 2009 and December 2010. Demographic data, medical diagnoses (including documented chronic lung disease), reason for ICU hospitalization, recent surgical interventions, SAPS II and McCabe scores were extracted from the database. Total duration of NIV and the need for tracheal intubation during the 5 days following the first hypercapnia documentation, as well as ICU and hospital mortality were recorded. Results are reported as median [IQR]. Comparisons with Chi2 or Kruskal-Wallis tests, p <0.05 (*). Results: 164 patients were included, 45 (27.4%) of whom were intubated after 10 [2-34] hours, after having received 7 [2-19] hours of NIV. NIV successful patients received 15 [5-22] hours of NIV for up to 5 days. Intubation was correlated with increased ICU (20% vs. 3%, p <0.001) and hospital (46.7% vs. 30.2, p >0.05) mortality. Conclusions: A majority of patients requiring NIV for hypercapnic respiratory failure in our ICU have no diagnosed chronic pulmonary disease. These patients tend to have increased ICUand hospital mortality. The majority of patients were non-surgical, a feature correlated with increased hospital mortality. Beside usual predictors of severity such as age and SAPS II, absence of diagnosed chronic pulmonary disease and non-operative state appear to be associated with increased mortality. Further studies should explore whether these patients are indeed more prone to an adverse outcome and which therapeutic strategies might contribute to alter this course.

Noninvasive coronary vessel wall and plaque imaging with magnetic resonance imaging.

BACKGROUND: Conventional x-ray angiography frequently underestimates the true burden of atherosclerosis. Although intravascular ultrasound allows for imaging of coronary plaque, this invasive technique is inappropriate for screening or serial examinations. We therefore sought to develop a noninvasive free-breathing MR technique for coronary vessel wall imaging. We hypothesized that such an approach would allow for in vivo imaging of coronary atherosclerosis. METHODS AND RESULTS: Ten subjects, including 5 healthy adult volunteers (aged 35+/-17 years, range 19 to 56 years) and 5 patients (aged 60+/-4 years, range 56 to 66 years) with x-ray-confirmed coronary artery disease (CAD), were studied with a T2-weighted, dual-inversion, fast spin-echo MR sequence. Multiple adjacent 5-mm cross-sectional images of the proximal right coronary artery were obtained with an in-plane resolution of 0.5x1.0 mm. A right hemidiaphragmatic navigator was used to facilitate free-breathing MR acquisition. Coronary vessel wall images were readily acquired in all subjects. Both coronary vessel wall thickness (1.5+/-0.2 versus 1.0+/-0.2 mm) and wall area (21.2+/-3.1 versus 13.7+/-4.2 mm(2)) were greater in patients with CAD (both P:<0.02 versus healthy adults). CONCLUSIONS: In vivo free-breathing coronary vessel wall and plaque imaging with MR has been successfully implemented in humans. Coronary wall thickness and wall area were significantly greater in patients with angiographic CAD. The presented technique may have potential applications in patients with known or suspected atherosclerotic CAD or for serial evaluation after pharmacological intervention.

Use of high-frequency jet ventilation for percutaneous tumor ablation.

PURPOSE: To report feasibility and potential benefits of high-frequency jet ventilation (HFJV) in tumor ablations techniques in liver, kidney, and lung lesions. METHODS: This prospective study included 51 patients (14 women, mean age 66 years) bearing 66 tumors (56 hepatic, 5 pulmonary, 5 renal tumors) with a median size of 16 ± 8.7 mm, referred for tumor ablation in an intention-to-treat fashion before preoperative anesthesiology visit. Cancellation and complications of HFJV were prospectively recorded. Anesthesia and procedure duration, as well as mean CO2 capnea, were recorded. When computed tomography guidance was used, 3D spacial coordinates of an anatomical target <2 mm in diameter on 8 slabs of 4 slices of 3.75-mm slice thickness were registered. RESULTS: HFJV was used in 41 of 51 patients. Of the ten patients who were not candidate for HFJV, two patients had contraindication to HFJV (severe COPD), three had lesions invisible under HFJV requiring deep inspiration apnea for tumor targeting, and five patients could not have HFJV because of unavailability of a trained anesthetic team. No specific complication or hypercapnia related to HFJV were observed despite a mean anesthetic duration of 2 h and ventilation performed in procubitus (n = 4) or lateral decubitus (n = 6). Measured internal target movement was 0.3 mm in x- and y-axis and below the slice thickness of 3.75 mm in the z-axis in 11 patients. CONCLUSIONS: HFJV is feasible in 80 % of patients allowing for near immobility of internal organs during liver, kidney, and lung tumor ablation.

Is atherosclerosis screening by noninvasive imaging effective in cardiovascular prevention? a systematic review

Texte intégral: http://www.springerlink.com/content/3q68180337551r47/fulltext.pdf

Décubitus ventral et syndrome de détresse respiratoire aiguë de l'adulte: de la théorie à la pratique [Prone position mechanical ventilation in the Acute Respiratory Distress syndrome: theoretical and practical considerations].

Mortality of the acute respiratory distress syndrome (ARDS) remains extremely high and only few evidence-based specific treatments are currently available. Protective mechanical ventilation has emerged as the comer stone of the management of ARDS to avoid the occurrence of ventilation-induced lung injuries (VILI). Mechanical ventilation in the prone position has often been considered as a rescue therapy reserved to refractory hypoxemia. Since the publication of the PROSEVA study in 2013, early prone positioning for mechanical ventilation should be recommended to improve survival of patients with severe ARDS. In this article, both the theoretical and practical aspects of mechanical ventilation in prone position are reviewed.