Disfunción Diafragmática en Ventilación Mecánica: Evaluación e Implicancias Clínicas / Diaphragmatic Dysfunction in Mechanical Ventilation: Evaluation and Clinical Implications

La debilidad diafragmática es un problema relevante en pacientes admitidos a la unidad de cuidados intensivos (UCI). Su presencia ha sido asociada a mayor tiempo en ventilación mecánica, weaning dificultoso, mayor riesgo de readmisión hospitalaria y mayor mortalidad. Las causas de esta debilidad son múltiples incluyendo factores relacionados a la severidad de la enfermedad, las intervenciones en la UCI y el uso de ventilación mecánica, termino conocido como miotrauma. Se han propuesto cuatro diferentes mecanismos de miotrauma relacionados a la sobre asistencia ventilatoria, baja asistencia ventilatoria, ocurrencia de contracciones diafragmáticas excéntricas y efecto de la presión espiratoria al final de espiración. Una adecuada evaluación y monitoreo de la función diafragmática es, por lo tanto, un aspecto clave que debe ser realizado al lado de la cama del paciente. La prueba de referencia para medir la función del diafragma es la presión transdiafragmática calculada como la diferencia entre la presión gástrica y presión esofágica. Adicionalmente, otras técnicas disponibles para la evaluación de la función del diafragma corresponden a la ecografía y la medición de la actividad eléctrica. Desde un punto de vista clínico, basado en la evidencia sobre disfunción diafragmática en los pacientes ventilados mecánicamente, uno de los principales desafíos actuales es poder buscar estrategias ventilatorias que incorporen protección diafragmática mientras se mantiene una ventilación protectora pulmonar. En este sentido, favorecer un nivel de esfuerzo inspiratorio adecuado junto con optimizar la interacción entre el paciente y el ventilador constituyen los principales objetivos de una ventilación diafragmática protectora.

Diaphragm weakness is a relevant problem in patients admitted to the intensive care unit (ICU). Its presence has been associated with prolonged mechanical ventilation, difficult weaning, higher risk of hospital readmission, and higher mortality. The causes of this weakness are multiple, including factors related to the severity of the disease, ICU interventions and the use of mechanical ventilation, a term known as myotrauma. Four different mechanisms of myotrauma have been proposed: 1. Ventilator over-assistance; 2. Ventilator under-assistance: 3. Eccentric diaphragm contractions: and 4. Excessive end-expiratory shortening by high PEEP. An adequate evaluation and monitoring of diaphragmatic function is, therefore, a key aspect that must be performed at the patient's bedside. The gold standard for measuring diaphragm function is transdiaphragmatic pressure calculated as the difference between gastric pressure and esophageal pressure. Furthermore, other techniques available for the evaluation of diaphragm function correspond to ultrasound and the measurement of its electrical activity. From a clinical point of view, based on diaphragmatic dysfunction evidence in mechanically ventilated patients, the main current challenge consists in applying ventilatory strategies that incorporate diaphragmatic protection while maintaining lung protective ventilation. In this sense, favoring an adequate level of inspiratory effort together with optimizing the interaction between the patient and the ventilator are the main objectives of diaphragm protective ventilation.

Near-Apneic Ventilation Decreases Lung Injury and Fibroproliferation in an Acute Respiratory Distress Syndrome Model with Extracorporeal Membrane Oxygenation.

RATIONALE: There is wide variability in mechanical ventilation settings during extracorporeal membrane oxygenation (ECMO) in patients with acute respiratory distress syndrome. Although lung rest is recommended to prevent further injury, there is no evidence to support it. OBJECTIVES: To determine whether near-apneic ventilation decreases lung injury in a pig model of acute respiratory distress syndrome supported with ECMO. METHODS: Pigs (26-36 kg; n = 24) were anesthetized and connected to mechanical ventilation. In 18 animals lung injury was induced by a double-hit consisting of repeated saline lavages followed by 2 hours of injurious ventilation. Then, animals were connected to high-flow venovenous ECMO, and randomized into three groups: 1) nonprotective (positive end-expiratory pressure [PEEP], 5 cm H2O; Vt, 10 ml/kg; respiratory rate, 20 bpm), 2) conventional-protective (PEEP, 10 cm H2O; Vt, 6 ml/kg; respiratory rate, 20 bpm), and 3) near-apneic (PEEP, 10 cm H2O; driving pressure, 10 cm H2O; respiratory rate, 5 bpm). Six other pigs were used as sham. All groups were maintained during the 24-hour study period. MEASUREMENTS AND MAIN RESULTS: Minute ventilation and mechanical power were lower in the near-apneic group, but no differences were observed in oxygenation or compliance. Lung histology revealed less injury in the near-apneic group. Extensive immunohistochemical staining for myofibroblasts and procollagen III was observed in the nonprotective group, with the near-apneic group exhibiting the least alterations. Near-apneic group showed significantly less matrix metalloproteinase-2 and -9 activity. Histologic lung injury and fibroproliferation scores were positively correlated with driving pressure and mechanical power. CONCLUSIONS: In an acute respiratory distress syndrome model supported with ECMO, near-apneic ventilation decreased histologic lung injury and matrix metalloproteinase activity, and prevented the expression of myofibroblast markers.

Sleep spindle activity in children with obstructive sleep apnea as a marker of neurocognitive performance: A pilot study.

STUDY OBJECTIVES: To assess spindle activity as possible markers for neurocognitive consequences in children with mild obstructive sleep apnea. METHODS: Children aged 6-11 years diagnosed with mild OSA (i.e., an apnea hypopnea index <5.0) were recruited and compared with age and gender-matched healthy controls. Polysomnographic recordings were analyzed for sleep microstructure and spindle activity. All children completed also an intelligence test battery (i.e., the Wechsler intelligence test for children, 4th version). RESULTS: Nineteen children with OSA (13 boys, mean age 7.1 ± 1.4 y), and 14 controls (7 boys, mean age 8.1 ± 1.9 y) were included. Mean IQ was 110 ± 12 for the complete sample, in children with OSA 111 ± 13, and in controls 108 ± 12 (p = 0.602). Controls showed a higher spindle index in N2 stage than children with OSA: 143.0 ± 42.5 vs 89.5 ± 56.9, respectively (p = 0.003). Spindle index in NREM was strongly and significantly correlated with Verbal Comprehension Index (VCI), Working Memory Index (WMI), Processing Speed Index (PSI), and total IQ in children with OSA. CONCLUSIONS: Children with mild OSA demonstrate a different pattern of sleep spindle activity that seems to be linked with neurocognitive performance, especially concerning memory. Sleep spindle activity seems to be involved with mechanisms related with neurocognitive consequences in children with OSA.

Impact of a Noninvasive Ventilation Protocol in Hospitalized Children With Acute Respiratory Failure.

BACKGROUND: Noninvasive ventilation (NIV) has proven to be useful in the management of children with acute respiratory failure as a result of acute lower respiratory infection. Despite this, evidence addressing the initiation and/or discontinuation criteria of NIV in children remains limited. The objective of this study was to evaluate the usefulness and clinical impact of an NIV protocol in hospitalized children with acute respiratory failure because of acute lower respiratory infection. METHODS: A randomized controlled clinical trial was carried out among subjects admitted during the winter season at Hospital Josefina Martinez between May and October of 2013. Inclusion criteria were age 3 months to 2 y, diagnosis of acute lower respiratory infection and requiring NIV according to a Modified Wood Scale score of ≥ 4 points. Subjects were randomized to NIV management according to medical criteria (control group) or to protocolized management of NIV (protocol group). Hours of NIV, hospital stay, and supplemental oxygen use after discontinuation of NIV, severity changes after NIV initiation, respiratory symptoms, and proportion of intubations were considered as events of interest. RESULTS: A total of 23 subjects were analyzed in the control group and 24 were analyzed in the protocol group. Hours of hospital stay, NIV, and supplemental oxygen post-NIV were not significantly different between groups (P = .70, .69, and .68, respectively). There were also no differences in intubation rate (3 of 29 for the control group and 2 of 31 for the protocol group). For the total sample there was a statistically significant decrease in the Modified Wood Scale score after 1 h of NIV (P < .001). A similar result was observed when performing a stratified intragroup analysis. CONCLUSIONS: We observed that the implementation of an NIV management protocol that integrates initiation and discontinuation criteria for NIV is feasible. However, its use showed no advantages over a non-protocolized strategy.

Geographic latitude and sleep duration: A population-based survey from the Tropic of Capricorn to the Antarctic Circle.

The impact of latitude on sleep duration remains virtually unexplored, even though latitude exerts profound influences on daylight duration. Using Chile as a one-country model, we explored on the potential associations between sleep duration and latitude. Based on the 2nd Chilean Health Survey, we identified reported sleep data during spring of people living from north to south in Chilean cities, located between 18°29'S to 53°18'S (4329 km distance at same longitude). A total of n = 2493 participants were included (mean age 45.3 ± 18.4 years, 41.8% males). Mean sleep duration on workdays and weekends was 7.42 ± 1.71 h, and 7.91 ± 2.13 h, respectively, ranging from 7.91 ± 1.92 h in the north to 8.33 ± 1.89 h in the south, such that more northern latitudes (i.e., 18°29'S to 39°50'S) slept less compared to more southern latitudes (i.e., 51°43'S-53°18'), even after controlling for age, gender, and socioeconomic status. In the logistic regression models, men residing at northern latitudes exhibited an odds ratio of 3.348 [95% CI: 1.905-5.882; p < 0.0001] for having shorter sleep on weekends than their southern counterparts. Latitude appears to strongly affect reported sleep patterns, leading to longer sleep duration with increasing latitude, particularly in men during weekends. Whether environmental factors such as photoperiod are causally involved in theses associations needs to be elucidated in future studies.

Long-term effects of adenotonsillectomy in children with obstructive sleep apnoea: protocol for a systematic review.

INTRODUCTION: Adenotonsillar hypertrophy is the most important anatomical factor associated with obstructive sleep apnoea syndrome in children. The American Academy of Pediatrics recommends adenotonsillectomy as the first line of treatment. AT can reduce the apnoea hypopnoea index; however, its effect on long-term outcomes remains unclear. METHODS AND ANALYSIS: We will conduct an electronic search for randomised controlled trials in MEDLINE, Cochrane Central Register of Controlled Trials (CENTRAL) and EMBASE. We will also identify literature by reviewing the references included in the selected studies and relevant reviews, screening through important scientific conferences, and searching for ongoing trials in the WHO International Clinical Trials Registry Platform. Two researchers will independently undertake selection of studies, data extraction and assessment of the risk of bias of included studies. We will estimate pooled risk ratios for dichotomous data, and mean difference or standardised mean difference for continuous outcomes. A random-effects model will be used for meta-analyses. Data synthesis and other analyses will be conducted using RevMan V.5.3 software. ETHICS AND DISSEMINATION: No ethics approval is considered necessary. The results of this study will be disseminated via peer-reviewed publications and social networks. TRIAL REGISTRATION NUMBER: CRD42015022102.

Extracorporeal membrane oxygenation improves survival in a novel 24-hour pig model of severe acute respiratory distress syndrome.

Extracorporeal membrane oxygenation (ECMO) is increasingly being used to treat severe acute respiratory distress syndrome (ARDS). However, there is limited clinical evidence about how to optimize the technique. Experimental research can provide an alternative to fill the actual knowledge gap. The purpose of the present study was to develop and validate an animal model of acute lung injury (ALI) which resembled severe ARDS, and which could be successfully supported with ECMO. Eighteen pigs were randomly allocated into three groups: sham, ALI, and ALI + ECMO. ALI was induced by a double-hit consisting in repeated saline lavage followed by a 2-hour period of injurious ventilation. All animals were followed up to 24 hours while being ventilated with conventional ventilation (tidal volume 10 ml/kg). The lung injury model resulted in severe hypoxemia, increased airway pressures, pulmonary hypertension, and altered alveolar membrane barrier function, as indicated by an increased protein concentration in bronchoalveolar fluid, and increased wet/dry lung weight ratio. Histologic examination revealed severe diffuse alveolar damage, characteristic of ARDS. Veno-venous ECMO was started at the end of lung injury induction with a flow > 60 ml/kg/min resulting in rapid reversal of hypoxemia and pulmonary hypertension. Mortality was 0, 66.6 and 16.6% in the SHAM, ALI and ALI + ECMO groups, respectively (p < 0.05). This is a novel clinically relevant animal model that can be used to optimize the approach to ECMO and foster translational research in extracorporeal lung support.

Sleep-disordered breathing in children with Down syndrome: Usefulness of home polysomnography.

OBJECTIVE: To investigate the technical feasibility of unattended home polysomnography (HPSG) in children with Down syndrome. METHODS: Data from children with Down syndrome under 10 years of age referred to a diagnostic sleep study was analyzed. A full sleep-lab based polysomnography (PSG) or a HPSG with a portable device was performed. Uninterpretable HPSGs were defined as: recordings with (i) loss of ≥2 of the following channels: nasal flow, or thoracoabdominal sensors, or (ii) HPSG with less than 4h of artifact-free recording time or (iii) less than 4h SpO2 (peripheral capillary oxygen saturation) signal. RESULTS: A total of 44 children (68% males) were included in the study, with a mean age of 3.6 (0.1-10) years. PSG was performed in 8 cases and HPSG in 36 cases. Six HPSG recordings were classified as uninterpretable and had to be repeated. Age, gender and BMI were no significant predictors of uninterpretability of the HPSG. Obstructive sleep apnea (OSA) was present in 61% (n=27) of all subjects, and classified as mild, moderate, and severe in 43% (n=19), 11% (n=5), and 7% (n=3) of cases, respectively. Interpretable and technically acceptable HPSGs were obtained in 30 subjects (83%). Age, gender and BMI were no significant predictors for interpretability of the HPSG. DISCUSSION: This study demonstrates that a portable polysomnographic home device may be helpful for diagnosing OSA in children with Down syndrome. Considering the potential consequences of untreated OSA, this screening test may be helpful for early diagnosis of OSA in children with Down syndrome.

Sleep-Disordered Breathing in Adolescents and Younger Adults: A Representative Population-Based Survey in Chile.

BACKGROUND: Prevalence and potential risk contributors of sleep-disordered breathing (SDB) in adolescents and younger adults remain unclear. We hypothesized that SDB prevalence in younger Hispanic adults is higher than the limited evidence indicates. METHODS: This is a population-based study of Hispanic subjects surveyed as part of the Chilean National Health Survey database. For this study, only subjects aged 15 to 40 years were included. Sleep and demographic questionnaires were used to assess SDB prevalence and its risk factors. Anthropometric measurements were performed in each subject. Prevalence was calculated for each SDB-related symptom. A regression model was constructed to investigate demographic risk factors of SDB. RESULTS: A total of 2,147 subjects were included. Mean age (± SD) was 27.2 ± 7.2 years, n = 899 (42%) were men. Habitual snoring was highly prevalent, with an average of 53.8% in men and 38.3% in women. Snoring, witnessed apneas, and daytime somnolence increased continuously with age, with an abnormal SDB questionnaire score detected in 2.5%. Reported sleep duration was 7.61 ± 1.67 hours during weekdays and 8.27 ± 2.11 hours during weekends. Snoring frequency was significantly higher in men than women at nearly all age groups, and an adjusted regression model (OR [95% CI]) identified male sex (2 [1.6-2.5]; P < .001) and BMI (1.08 [1.03-1.12]; P < .001) as independent risk factors for snoring. CONCLUSION: The risk of SDB is highly prevalent in younger adults, even in females, and increases with age and BMI. The high prevalence and low awareness justify active screening and treatment of SDB in this population.

Impact of television on the quality of sleep in preschool children.

OBJECTIVES: We aimed to investigate the impact of different habits concerning television (TV) use and the time of day in which TV is watched on the sleep quality of young children. METHODS: Parents of 100 healthy children (58% boys, mean age of 2.7 ± 1.5 years) attending a routine health check completed the Sleep Disturbance Scale for Children (SDSC) and a questionnaire concerning TV and electronic media use. Children were divided into those with a normal (SDSC-) or abnormal (SDSC+) questionnaire score. TV viewing habits were compared between groups. RESULTS: The total sleep time and total TV viewing time were not different between groups. A TV set was inside each child's bedroom in 51% of participants. Children with a TV in their bedroom showed significantly higher scores in the "sleep terrors," "nightmares," "sleep talking," and "tired when waking up" responses of the SDSC (P = 0.02, 0.01, 0.01, and 0.01, respectively). Children with a TV in their room had an odds ratio (95% confidence interval) of 3.29 (1.08-9.99) for having an abnormal SDSC. Evening TV viewers had significantly higher SDSC scores compared with those who watched TV earlier during the day (P = 0.04). CONCLUSIONS: The presence of a TV set in the child's bedroom was associated with significant reductions in the quality of young children's sleep. Evening exposure to TV was associated with significantly worse sleep quality.

What is the effect of chest physiotherapy in hospitalized children with pneumonia?

Chest physiotherapy is applied in clinical practice for the treatment of pneumonia. However, its use is still controversial. Searching in Epistemonikos database, which is maintained by screening 30 databases, we identified one systematic review including two relevant randomized controlled trials. We combined the evidence using meta-analysis and generated a summary of findings table following the GRADE approach. We concluded it is unclear whether chest physiotherapy increases or decreases the length of hospitalization, severity, or the time to clinical improvement in children with pneumonia because the certainty of the evidence is very low.

La kinesioterapia respiratoria es ampliamente utilizada en la práctica clínica para el tratamiento de la neumonía, sin embargo, su efecto en niños con neumonia aún es controvertido. Utilizando la base de datos Epistemonikos, la cual es mantenida mediante búsquedas en 30 bases de datos, identificamos una revisión sistemática que incluye dos estudios aleatorizados pertinentes a la pregunta. Realizamos un metanálisis y tablas de resumen de los resultados utilizando el método GRADE. Concluimos que existe incertidumbre sobre si la kinesioterapia respiratoria tiene algún efecto sobre el tiempo de hospitalización, severidad y resolución clínica en niños con neumonía porque la certeza de la evidencia es muy baja.