Sergio N. Nemer

Recomendações brasileiras de ventilação mecânica 2013. Parte I

Perspectives on invasive and noninvasive ventilatory support for critically ill patients are evolving, as much evidence indicates that ventilation may have positive effects on patient survival and the quality of the care provided in intensive care units in Brazil. For those reasons, the Brazilian Association of Intensive Care Medicine (Associacao de Medicina Intensiva Brasileira - AMIB) and the Brazilian Thoracic Society (Sociedade Brasileira de Pneumologia e Tisiologia - SBPT), represented by the Mechanical Ventilation Committee and the Commission of Intensive Therapy, respectively, decided to review the literature and draft recommendations for mechanical ventilation with the goal of creating a document for bedside guidance as to the best practices on mechanical ventilation available to their members. The document was based on the available evidence regarding 29 subtopics selected as the most relevant for the subject of interest. The project was developed in several stages, during which the selected topics were distributed among experts recommended by both societies with recent publications on the subject of interest and/or significant teaching and research activity in the field of mechanical ventilation in Brazil. The experts were divided into pairs that were charged with performing a thorough review of the international literature on each topic. All the experts met at the Forum on Mechanical Ventilation, which was held at the headquarters of AMIB in Sao Paulo on August 3 and 4, 2013, to collaboratively draft the final text corresponding to each sub-topic, which was presented to, appraised, discussed and approved in a plenary session that included all 58 participants and aimed to create the final document.

Parâmetros preditivos para o desmame da ventilação mecânica

The use of predictive parameters for weaning from mechanical ventilation is a rather polemic topic, and the results of studies on this topic are divergent. Regardless of the use of these predictive parameters, the spontaneous breathing trial (SBT) is recommended. The objective of the present study was to review the utility of predictive parameters for weaning in adults. To that end, we searched the Medline, LILACS, and PubMed databases in order to review articles published between 1991 and 2009, in English or in Portuguese, using the following search terms: weaning/desmame, extubation/extubacao, and weaning indexes/indices de desmame. The use of clinical impression is an inexact means of predicting weaning outcomes. The most widely used weaning parameter is the RR/tidal volume (V T) ratio, although this parameter presents heterogeneous results in terms of accuracy. Other relevant parameters are MIP, airway occlusion pressure (P0.1), the P0.1/MIP ratio, RR, V T, minute volume, and the index based on compliance, RR, oxygenation, and MIP. An index created in Brazil, the integrative weaning index, has shown high accuracy. Although recommended, the SBT is inaccurate, approximately 15% of extubation failures going unidentified in SBTs. The main limitations of the weaning indexes are related to their use in specific populations, the cut-off points selected, and variations in the types of measurement. Since the SBT and the clinical impression are not 100% accurate, the weaning parameters can be useful, especially in situations in which the decision as to weaning is difficult.

Evaluation of maximal inspiratory pressure, tracheal airway occlusion pressure, and its ratio in the weaning outcome.

PURPOSE The objective of this study is to evaluate the predictive performance of maximal inspiratory pressure (Pimax), airway occlusion pressure (P 0.1), and its ratio (P 0.1/Pimax) in the weaning outcome. MATERIALS AND METHODS Seventy patients on mechanical ventilation for more than 24 hours, who fulfilled weaning criteria, were prospectively evaluated. Pimax less than -25 cm H(2)O, P 0.1 less than 4.2 cm H(2)O, and P 0.1/Pimax less than 0.14 were evaluated in all patients before spontaneous breathing trials. The receiver operating characteristic (ROC) curve was calculated to evaluate the predictive performance of each index. RESULTS Pimax presented the area under the ROC curves smaller than those for P 0.1 and P 0.1/Pimax (0.52 x 0.76 and 0.52 x 0.78; P = .004 and P = .0006, respectively), being the criteria of worst performance. P 0.1/Pimax presented excellent predictive performance in weaned patients, with sensitivity of 98.08, but with the area under the ROC curves only slightly larger than those for P 0.1 (0.78 x 0.76, respectively; P = .69). CONCLUSION In our study, P 0.1 and P 0.1/Pimax ratio were moderately accurate, whereas Pimax was less accurate in predicting the weaning outcome.

Alveolar recruitment maneuver in patients with subarachnoid hemorrhage and acute respiratory distress syndrome: A comparison of 2 approaches☆

PURPOSE The purpose of the study was to compare 2 alveolar recruitment maneuvers (ARMs) approaches in patients with subarachnoid hemorrhage (SAH) and acute respiratory distress syndrome (ARDS). MATERIAL AND METHODS Sixteen SAH patients with ARDS were randomized in 2 similar groups. One received ARM with continuous positive airway pressure (CPAP) of 35 cm H(2)O for 40 seconds (CPAP recruitment), whereas the other received pressure control ventilation with positive-end expiratory pressure of 15 cm H(2)O and pressure control above positive end-expiratory pressure of 35 cm H(2)O for 2 minutes (pressure control recruitment maneuver [PCRM]). Intracranial pressure (ICP) and cerebral perfusion pressure (CPP) were measured before and after ARM. The ratio of arterial oxygen tension to fraction of inspired oxygen was measured before and 1 hour after the ARM. RESULTS After ARM, ICP was higher in CPAP recruitment (20.50 ± 4.75 vs 13.13 ± 3.56 mm Hg; P = .003); and CPP was lower in CPAP recruitment (62.38 ± 9.81 vs 79.60 ± 6.8 mm Hg; P = .001). One hour after the ARM, the ratio of arterial oxygen tension to fraction of inspired oxygen increased significantly only in PCRM (108.5 to 203.6; P = .0078). CONCLUSION In SAH patients with ARDS, PCRM did not affect ICP and decreased CPP in safe levels, besides improving oxygenation.

Effects of positive end-expiratory pressure on brain tissue oxygen pressure of severe traumatic brain injury patients with acute respiratory distress syndrome: A pilot study

PURPOSE To verify whether high positive end-expiratory pressure levels can increase brain tissue oxygen pressure, and also their effects on pulse oxygen saturation, intracranial pressure, and cerebral perfusion pressure. MATERIAL AND METHODS Twenty traumatic brain injury patients with acute respiratory distress syndrome were submitted to positive end-expiratory pressure levels of 5, 10, and 15 cm H2O progressively. The 3 positive end-expiratory pressure levels were used during 20 minutes for each one, whereas brain tissue oxygen pressure, oxygen saturation, intracranial pressure, and cerebral perfusion pressure were recorded. RESULTS Brain tissue oxygen pressure and oxygen saturation increased significantly with increasing positive end-expiratory pressure from 5 to 10 and from 10 to 15 cm H2O (P=.0001 and P=.0001 respectively). Intracranial pressure and cerebral perfusion pressure did not differ significantly with increasing positive end-expiratory pressure from 5 to 10 and from 10 to 15 cm H2O (P=.16 and P=.79 respectively). CONCLUSIONS High positive end-expiratory pressure levels increased brain tissue oxygen pressure and oxygen saturation, without increase in intracranial pressure or decrease in cerebral perfusion pressure. High positive end-expiratory pressure levels can be used in severe traumatic brain injury patients with acute respiratory distress syndrome as a safe alternative to improve brain oxygenation.

Applying a new weaning index in ICU older patients

With the increase in life expectation, more admissions to hospital, use of mechanical ventilation (MV) and weaning trials in older patients have been observed.

Effects of expiratory trigger setting on respiratory parameters of nonchronic obstructive pulmonary disease patients

< 40%. Expiratory trigger was set at 1%, 25%, 50% and 70%, for at least 5-minute period each. Respiratory rate, f / Vt ratio, Vt, Ve, SpO2, and Ti / Ttot were measured in each percentage of ET. Analysis of variance for repeated measures was used to analyze variations during the four ET values and to verify variations out of the comfort zone. Bonferroni test was used to identify which values were significantly different among the multiple comparisons. A probability of less than 0.05 was considered significant. Results: Tidal volume, RR and f / Vt ratio presented significant increase in the percentage of patients that showed these parameters out of the comfort zone (p = 0.0025, p = 0.0002 and p = 0.007 respectively). No respiratory parameter presented significant variations when the comparisons were made from 1% to 25% of ET. Conclusions: In non-COPD patients, the use of ET in 1% or 25% has no effect on the respiratory parameters. The increase of ET to 50% or more can worse the respiratory parameters and lead to a rapid shallow breathing, suggesting that these values should be avoided in non-COPD patients.

The Integrative Weaning Index in Elderly ICU Subjects

BACKGROUND: With increasing life expectancy and ICU admission of elderly patients, mechanical ventilation, and weaning trials have increased worldwide. METHODS: We evaluated a cohort with 479 subjects in the ICU. Patients younger than 18 y, tracheostomized, or with neurologic diseases were excluded, resulting in 331 subjects. Subjects ≥70 y old were considered elderly, whereas those <70 y old were considered non-elderly. Besides the conventional weaning indexes, we evaluated the performance of the integrative weaning index (IWI). The probability of successful weaning was investigated using relative risk and logistic regression. The Hosmer-Lemeshow goodness-of-fit test was used to calibrate and the C statistic was calculated to evaluate the association between predicted probabilities and observed proportions in the logistic regression model. RESULTS: Prevalence of successful weaning in the sample was 83.7%. There was no difference in mortality between elderly and non-elderly subjects (P = .16), in days of mechanical ventilation (P = .22) and days of weaning (P = .55). In elderly subjects, the IWI was the only respiratory variable associated with mechanical ventilation weaning in this population (P < .001). CONCLUSIONS: The IWI was the independent variable found in weaning of elderly subjects that may contribute to the critical moment of this population in intensive care.

Positive end-expiratory pressure can increase brain tissue oxygen pressure in hypoxemic severe traumatic brain injury patients

Brain tissue oxygen pressure (PtiO2) reflects brain oxygenation and is a useful tool in traumatic brain injury (TBI) patients. Increases in inspired oxygen fraction (FiO2) are related to improvement on PbrO2, but other approaches that aim to improve oxygenation, like increasing positive-end expiratory pressure (PEEP), were not deeply evaluated in humans.