Energy transmission in mechanically ventilated children: a translational study.

BACKGROUND: Recurrent delivery of tidal mechanical energy (ME) inflicts ventilator-induced lung injury (VILI) when stress and strain exceed the limits of tissue tolerance. Mechanical power (MP) is the mathematical description of the ME delivered to the respiratory system over time. It is unknown how ME relates to underlying lung pathology and outcome in mechanically ventilated children. We therefore tested the hypothesis that ME per breath with tidal volume (Vt) normalized to bodyweight correlates with underlying lung pathology and to study the effect of resistance on the ME dissipated to the lung. METHODS: We analyzed routinely collected demographic, physiological, and laboratory data from deeply sedated and/or paralyzed children < 18 years with and without lung injury. Patients were stratified into respiratory system mechanic subgroups according to the Pediatric Mechanical Ventilation Consensus Conference (PEMVECC) definition. The association between MP, ME, lung pathology, and duration of mechanical ventilation as a primary outcome measure was analyzed adjusting for confounding variables and effect modifiers. The effect of endotracheal tube diameter (ETT) and airway resistance on energy dissipation to the lung was analyzed in a bench model with different lung compliance settings. RESULTS: Data of 312 patients with a median age of 7.8 (1.7-44.2) months was analyzed. Age (p <  0.001), RR p <  0.001), and Vt <  0.001) were independently associated with MPrs. ME but not MP correlated significantly (p <  0.001) better with lung pathology. Competing risk regression analysis adjusting for PRISM III 24 h score and PEMVECC stratification showed that ME on day 1 or day 2 of MV but not MP was independently associated with the duration of mechanical ventilation. About 33% of all energy generated by the ventilator was transferred to the lung and highly dependent on lung compliance and airway resistance but not on endotracheal tube size (ETT) during pressure control (PC) ventilation. CONCLUSIONS: ME better related to underlying lung pathology and patient outcome than MP. The delivery of generated energy to the lung was not dependent on ETT size during PC ventilation. Further studies are needed to identify injurious MErs thresholds in ventilated children.

Bedside calculation of mechanical power during volume- and pressure-controlled mechanical ventilation.

BACKGROUND: Mechanical power (MP) is the energy delivered to the respiratory system over time during mechanical ventilation. Our aim was to compare the currently available methods to calculate MP during volume- and pressure-controlled ventilation, comparing different equations with the geometric reference method, to understand whether the easier to use surrogate formulas were suitable for the everyday clinical practice. This would warrant a more widespread use of mechanical power to promote lung protection. METHODS: Forty respiratory failure patients, sedated and paralyzed for clinical reasons, were ventilated in volume-controlled ventilation, at two inspiratory flows (30 and 60 L/min), and pressure-controlled ventilation with a similar tidal volume. Mechanical power was computed both with the geometric method, as the area between the inspiratory limb of the airway pressure and the volume, and with two algebraic methods, a comprehensive and a surrogate formula. RESULTS: The bias between the MP computed by the geometric method and by the comprehensive algebraic method during volume-controlled ventilation was respectively 0.053 (0.77, - 0.81) J/min and - 0.4 (0.70, - 1.50) J/min at low and high flows (r2 = 0.96 and 0.97, p < 0.01). The MP measured and computed by the two methods were highly correlated (r2 = 0.95 and 0.94, p < 0.01) with a bias of - 0.0074 (0.91, - 0.93) and - 1.0 (0.45, - 2.52) J/min at high-low flows. During pressure-controlled ventilation, the bias between the MP measured and the one calculated with the comprehensive and simplified methods was correlated (r2 = 0.81, 0.94, p < 0.01) with mean differences of - 0.001 (2.05, - 2.05) and - 0.81 (2.11, - 0.48) J/min. CONCLUSIONS: Both for volume-controlled and pressure-controlled ventilation, the surrogate formulas approximate the reference method well enough to warrant their use in the everyday clinical practice. Given that these formulas require nothing more than the variables already displayed by the intensive care ventilator, a more widespread use of mechanical power should be encouraged to promote lung protection against ventilator-induced lung injury.

Clinical characteristics of long-term survival with noninvasive ventilation and factors affecting the transition to invasive ventilation in amyotrophic lateral sclerosis.

INTRODUCTION: We evaluated post-noninvasive ventilation survival and factors for the transition to tracheostomy in amyotrophic lateral sclerosis (ALS). METHODS: We analyzed 197 patients using a prospectively collected database with 114 patients since 2000. RESULTS: Among 114 patients, 59 patients underwent noninvasive ventilation (NIV), which prolonged the total median survival time to 43 months compared with 32 months without treatment. The best post-NIV survival was associated with a lack of bulbar symptoms, higher measured pulmonary function, and a slower rate of progression at diagnosis. The transition rate from NIV to tracheostomy gradually decreased over the years. Patients using NIV for more than 6 months were more likely to refuse tracheostomy and to be women. DISCUSSION: This study confirmed a positive survival effect with NIV, which was less effective in patients with bulbar dysfunction. Additional studies are required to determine the best timing for using NIV with ALS in patients with bulbar dysfunction. Muscle Nerve 58:770-776 2018.

Mechanical ventilation strategies for intensive care unit patients without acute lung injury or acute respiratory distress syndrome: a systematic review and network meta-analysis.

BACKGROUND: It has been shown that the application of a lung-protective mechanical ventilation strategy can improve the prognosis of patients with acute lung injury (ALI) or acute respiratory distress syndrome (ARDS). However, the optimal mechanical ventilation strategy for intensive care unit (ICU) patients without ALI or ARDS is uncertain. Therefore, we performed a network meta-analysis to identify the optimal mechanical ventilation strategy for these patients. METHODS: We searched the Cochrane Central Register of Controlled Trials (CENTRAL) in the Cochrane Library, EMBASE, MEDLINE, CINAHL, and Web of Science for studies published up to July 2015 in which pulmonary compliance or the partial pressure of arterial oxygen/fraction of inspired oxygen (PaO2/FIO2) ratio was assessed in ICU patients without ALI or ARDS, who received mechanical ventilation via different strategies. The data for study characteristics, methods, and outcomes were extracted. We assessed the studies for eligibility, extracted the data, pooled the data, and used a Bayesian fixed-effects model to combine direct comparisons with indirect evidence. RESULTS: Seventeen randomized controlled trials including a total of 575 patients who received one of six ventilation strategies were included for network meta-analysis. Among ICU patients without ALI or ARDS, strategy C (lower tidal volume (VT) + higher positive end-expiratory pressure (PEEP)) resulted in the highest PaO2/FIO2 ratio; strategy B (higher VT + lower PEEP) was associated with the highest pulmonary compliance; strategy A (lower VT + lower PEEP) was associated with a shorter length of ICU stay; and strategy D (lower VT + zero end-expiratory pressure (ZEEP)) was associated with the lowest PaO2/FiO2 ratio and pulmonary compliance. CONCLUSIONS: For ICU patients without ALI or ARDS, strategy C (lower VT + higher PEEP) was associated with the highest PaO2/FiO2 ratio. Strategy B (higher VT + lower PEEP) was superior to the other strategies in improving pulmonary compliance. Strategy A (lower VT + lower PEEP) was associated with a shorter length of ICU stay, whereas strategy D (lower VT + ZEEP) was associated with the lowest PaO2/FiO2 ratio and pulmonary compliance.

Fisioterapia respiratoria / No disponible

No disponible

Ventilación no invasiva con presión de soporte con volumen asegurado en un paciente con enfermedad pulmonar obstructiva crónica (EPOC) agudizada / No disponible

El paciente con EPOC exacerbado y encefalopatía hipercápnica puede plantear serios problemas al tratarle con ventilación mecánica no invasiva (VMNI). Aun no siendo una contraindicación para la VMNI, la falta de colaboración puede ser motivo de fracaso de la técnica. En la actualidad disponemos de modos ventilatorios limitados por presión que aseguran el volumen corriente aportado al paciente. El modo presión de soporte con volumen asegurado (AVAPS) nos ofrece esta opción. Existen pocas publicaciones sobre el uso de esta modalidad ventilatoria en la situación de fallo respiratorio agudo hipercápnico. Presentamos el caso de un paciente con EPOC exacerbado en situación de encefalopatía hipercápnica, tratado con éxito con este modo ventilatorio

The patient with exacerbated COPD and hypercapnic encephalopathy may pose serious problems regarding treatment with non-invasive mechanical ventilation (NIMV). Although no contraindication has been found for NIMV, lack of collaboration may be a reason for failure of the technique. We currently have ventilatory methods limited by the pressure that ensures the tidal volume provided to the patient. The average volume assured pressure support (AVAPS) offers us this option. There are few publications on the use of this ventilatory modality when there is acute hypercapnic respiratory failure. We present the case of a male patient with exacerbated COPD with hypercapnic encephalopathy who was successfully treated with this ventilatory mode

Selección de la interfase en ventilación mecánica no invasiva en el paciente crítico / Interface selection in non-invasive mechanical ventilation in critically ill patient

Antecedentes. La ventilación mecánica no invasiva (VMNI) se utiliza con un ventilador mecánico y una interfase que se interpone entre el paciente y el ventilador sin invadir la vía aérea como alternativa a la vía aérea artificial en diversas situaciones de insuficiencia respiratoria. Objetivo. Determinar si la selección de una interfase adecuada al contorno facial del paciente y su patología conlleva el triunfo o fracaso del procedimiento, considerándola una variable dependiente del éxito de VMNI. Método. Revisión descriptiva. Búsqueda bibliográfica principal en PubMed, con búsquedas secundarias en The Cochrane Library y CUIDEN. Se incluyen los artículos publicados desde 2000 en adultos. No se imponen limitaciones en diseño del estudio, tipo de intervención o resultados de las publicaciones. Se revisan los artículos para determinar su relevancia y extraer las conclusiones. La heterogeneidad de diseños impide la combinación estadística de resultados. Resultados. Se encontraron 67 publicaciones, de las cuales se desestimaron 28 por no estar relacionadas con el motivo del estudio, 12 por estar realizadas en población pediátrica, 8 por idioma, 2 por haberse efectuado en animales y 1 por estar duplicada. Los 16 estudios incluidos evidencian la eficacia de la VMNI con estudios no comparables entre diferentes interfases. Conclusiones. La evidencia consultada sugiere los beneficios de la VMNI e insiste en la gran importancia de la interfase en la tolerancia y éxito de la técnica. Los estudios son heterogéneos en diseño, pero los autores sugieren continuar desarrollando mejores interfases con mayor tolerancia y menores complicaciones (AU)

Background. Non-invasive ventilation is used with a mechanical ventilator and an interface that is interposed between the patient and the ventilator without invading the airway. It is an alternative to the artificial airway in situations of acute respiratory insufficiency. Objective. Determine if the selection of an appropriate interface to the contour of the patient’s face and the pathology involves the triumph or failure of the procedure, deeming it is a dependent variable in the success of the NIV. Method. Research bibliographic in PubMed, with secondary search in the Cochrane Library and CUIDEN. Includes the articles published since 2000 in adults. No limitations have been imposed on study design, type of intervention or results of the publications. The articles are reviewed to determine their relevance and draw conclusions. The heterogeneity of designs prevents statistical combination of results and a review was conducted descriptive. results. There were 67 publications of which 28 were rejected by may not be related to the reason for this study, 12 to be made in pediatric population, 8 per language, 2 to be carried out on animals and 1 to be duplicated. The 16 included studies attest to the effectiveness of the NIV with studies not comparable between different interfaces. Conclusions. The consulted evidence suggests the benefits of NIV, it insisting on the great importance of the interface to toleranceand successful of the technique. The studies are heterogeneous in its design but the authors suggest continue developing better interfaces, with greater tolerance and fewer complications (AU)

A taxonomy for mechanical ventilation: 10 fundamental maxims.

The American Association for Respiratory Care has declared a benchmark for competency in mechanical ventilation that includes the ability to "apply to practice all ventilation modes currently available on all invasive and noninvasive mechanical ventilators." This level of competency presupposes the ability to identify, classify, compare, and contrast all modes of ventilation. Unfortunately, current educational paradigms do not supply the tools to achieve such goals. To fill this gap, we expand and refine a previously described taxonomy for classifying modes of ventilation and explain how it can be understood in terms of 10 fundamental constructs of ventilator technology: (1) defining a breath, (2) defining an assisted breath, (3) specifying the means of assisting breaths based on control variables specified by the equation of motion, (4) classifying breaths in terms of how inspiration is started and stopped, (5) identifying ventilator-initiated versus patient-initiated start and stop events, (6) defining spontaneous and mandatory breaths, (7) defining breath sequences (8), combining control variables and breath sequences into ventilatory patterns, (9) describing targeting schemes, and (10) constructing a formal taxonomy for modes of ventilation composed of control variable, breath sequence, and targeting schemes. Having established the theoretical basis of the taxonomy, we demonstrate a step-by-step procedure to classify any mode on any mechanical ventilator.

[Statement of the Association of Pneumological Clinics and the German Respiratory Society on the coding of invasive and non-invasive ventilation in intensity care]. / Positionspapier des Verbandes pneumologischer Kliniken und der Deutschen Gesellschaft für Pneumologie und Beatmungsmedizin zur Kodierung der invasiven und nicht-invasiven Beatmung bei intensivmedizinisch versorgten Patienten.

Mechanical ventilation in patients with respiratory failure represents one of the most important aspects of intensity care. It can be performed invasively and non-invasively depending on the clinical situation and the underlying disease. The expenditure and consumption of resources is the basis of the compensation for each patient case in the German diagnosis related group system. For ventilated patients it is calculated based on the hours of ventilation, according to the standard coding guideline. In this statement, the German Respiratory Society and the Association of Pneumological Clinics aim to clarify some aspects of the coding of invasive and non-invasive ventilation.

A rational framework for selecting modes of ventilation.

Mechanical ventilation is a life-saving intervention for respiratory failure and thus has become the cornerstone of the practice of critical care medicine. A mechanical ventilation mode describes the predetermined pattern of patient-ventilator interaction. In recent years there has been a dizzying proliferation of mechanical ventilation modes, driven by technological advances and market pressures, rather than clinical data. The comparison of these modes is hampered by the sheer number of combinations that need to be tested against one another, as well as the lack of a coherent, logical nomenclature that accurately describes a mode. In this paper we propose a logical nomenclature for mechanical ventilation modes, akin to biological taxonomy. Accordingly, the control variable, breath sequence, and targeting schemes for the primary and secondary breaths represent the order, family, genus, and species, respectively, for the described mode. To distinguish unique operational algorithms, a fifth level of distinction, termed variety, is utilized. We posit that such coherent ordering would facilitate comparison and understanding of modes. Next we suggest that the clinical goals of mechanical ventilation may be simplified into 3 broad categories: provision of safe gas exchange; provision of comfort; and promotion of liberation from mechanical ventilation. Safety is achieved via optimization of ventilation-perfusion matching and pressure-volume relationship of the lungs. Comfort is provided by fostering patient-ventilator synchrony. Liberation is promoted by optimization of the weaning experience. Then we follow a paradigm that matches the technological capacity of a particular mode to achieving a specific clinical goal. Finally, we provide the reader with a comparison of existing modes based on these principles. The status quo in mechanical ventilation mode nomenclature impedes communication and comparison of existing mechanical ventilation modes. The proposed model, utilizing a systematic nomenclature, provides a useful framework to address this unmet need.

Impact of mechanical ventilation and fluid load on pulmonary glycosaminoglycans.

The combined effect of mechanical ventilation and fluid load on pulmonary glycasaminoglycans (GAGs) was studied in anaesthetized rats ((BW 290±21.8 (SE)g) mechanically ventilated for 4h: (a) at low (∼7.5mlkg(-1)) or high (∼23mlkg(-1)) tidal volume (V(T)) and zero alveolar pressure; (b) at low or high V(T) at 5cmH(2)O positive end-expiratory pressure (PEEP); (c) with or without 7mlkg(-1)h(-1) intravenous infusion of Phosphate Buffer Solution (PBS). Compared to spontaneous breathing, GAGs extractability decreased by 52.1±1.5% and 42.2±7.3% in not-infused lungs mechanically ventilated at low V(T) or at high V(T) and PEEP, respectively. In contrast, in infused lungs, GAGs extractability increased by 56.1±4.0% in spontaneous ventilation and PEEP and up to 81.1% in all mechanically ventilated lungs, except at low V(T) without PEEP. In the absence of an inflammatory process, these results suggest that PEEP was protective at low but not at high V(T) when alveolar structures experience exceedingly high stresses. When combined to mechanical ventilation, fluid load might exacerbate edema development and lung injury.

Determining the basis for a taxonomy of mechanical ventilation.

BACKGROUND: Mechanical ventilation technology has evolved rapidly over the last 30 years. One consequence is the creation of an unmanageable number of names to describe modes of ventilation. The proliferation of names makes education of end users difficult, potentially compromising the quality of patient care. OBJECTIVE: To determine if stakeholders are familiar enough with published constructs related to modes of mechanical ventilation to form a basis for a consensus, by surveying the medical, education, and business communities. The hypotheses tested were: there is concordance (> 50%) on 10 basic constructs related to modes; concordance with the basic constructs varies among stakeholders according to professional training and professional activity; and concordance varies among the set of constructs. METHODS: The survey was distributed through an Internet-based tool to 2,994 physicians, respiratory therapists, nurses, engineers, and others involved with mechanical ventilation. Hypotheses were tested with chi-square, with P < .05 considered significant. RESULTS: The response rate was 15%. Respondents were 55% respiratory therapists, 35% physicians, 3% nurses, 1% engineers, and 5% other professionals. There was an 82% concordance with the 10 constructs (P < .001). Respiratory therapists showed the highest degree of concordance (84%) and "other profession" showed the lowest (79%) (P = .006). No significant difference (P = .07) in concordance was observed when data were grouped by professional activity. Concordance differed significantly among the survey questions (P < .001). CONCLUSIONS: Survey results indicate that respondents were either familiar with or amenable to the previously published literature that the survey constructs represented. The degree of familiarity and concordance with these constructs represents a sufficient basis for attempting to formalize a taxonomy. Further analysis of the pattern of concordance among the constructs will inform future educational and consensus building efforts.