Giacomo Grasselli

Patient–ventilator interaction in ARDS patients with extremely low compliance undergoing ECMO: a novel approach based on diaphragm electrical activity

PurposePatients with acute respiratory distress syndrome (ARDS) requiring extracorporeal membrane oxygenation (ECMO) usually present very low respiratory system compliance (Cstrs) values (i.e., severe restrictive respiratory syndrome patients). As a consequence, they are at high risk of experiencing poor patient–ventilator interaction during assisted breathing. We hypothesized that monitoring of diaphragm electrical activity (EAdi) may enhance asynchrony assessment and that neurally adjusted ventilatory assist (NAVA) may reduce asynchrony, especially in more severely restricted patients.MethodsWe enrolled ten consecutive ARDS patients with very low Cstrs values undergoing ECMO after switching from controlled to pressure support ventilation (PSV). We randomly tested (30xa0min) while recording EAdi: (1) PSV30 (PSV with an expiratory trigger at 30xa0% of flow peak value); (2) PSV1 (PSV with expiratory trigger at 1xa0%); (3) NAVA. During each step, we measured the EAdi-based asynchrony index (AIEAdi)xa0=xa0flow-, pressure- and EAdi-based asynchrony events/EAdi-based respiratory ratexa0×xa0100.ResultsAIEAdi was high during all ventilation modes, and the most represented asynchrony pattern was specific for this population (i.e., premature cycling). NAVA was associated with significantly decreased, although suboptimal, AIEAdi values in comparison to PSV30 and PSV1 (pxa0<xa00.01 for both). The PSV30–NAVA and PSV1–NAVA differences in AIEAdi values were inversely correlated with patients’ Cstrs (R2xa0=xa00.545, pxa0=xa00.01 and R2xa0=xa00.425, pxa0<xa00.05; respectively).ConclusionsEAdi allows accurate analysis of asynchrony patterns and magnitude in ARDS patients with very low Cstrs undergoing ECMO. In these patients, NAVA is associated with reduced asynchrony.

Respiratory mechanics to understand ARDS and guide mechanical ventilation

OBJECTIVEnAs precision medicine is becoming a standard of care in selecting tailored rather than average treatments, physiological measurements might represent the first step in applying personalized therapy in the intensive care unit (ICU). A systematic assessment of respiratory mechanics in patients with the acute respiratory distress syndrome (ARDS) could represent a step in this direction, for two main reasons. Approach and Main results: On the one hand, respiratory mechanics are a powerful physiological method to understand the severity of this syndrome in each single patient. Decreased respiratory system compliance, for example, is associated with low end expiratory lung volume and more severe lung injury. On the other hand, respiratory mechanics might guide protective mechanical ventilation settings. Improved gravitationally dependent regional lung compliance could support the selection of positive end-expiratory pressure and maximize alveolar recruitment. Moreover, the association between driving airway pressure and mortality in ARDS patients potentially underlines the importance of sizing tidal volume on respiratory system compliance rather than on predicted body weight.nnnSIGNIFICANCEnThe present review article aims to describe the main alterations of respiratory mechanics in ARDS as a potent bedside tool to understand severity and guide mechanical ventilation settings, thus representing a readily available clinical resource for ICU physicians.

Systematic assessment of advanced respiratory physiology: precision medicine entering real-life ICU?

In this uprising era of precision medicine [1], clinical translation of physiological measurements supporting personalized treatments in the intensive care unit (ICU) is of extreme interest. To this end, respiratory mechanics measurements in patients with acute respiratory distress syndrome (ARDS) might become standard to titrate mechanical ventilation settings [2]. This concept was the driving hypothesis of an interesting article by Lu Chen and colleagues recently published in Critical Care [3]. The authors report implementation into the real-life of the medical-surgical and trauma-neurosurgical ICUs of the Toronto-based St. Michael’s Hospital of a 1-year quality improvement program aimed at measuring advanced respiratory mechanics at the bedside in patients with ARDS. Output was real-time creation of an analytic report with actual patient measures handed to the attending physician and start of a prospective registry for future studies. The program enrolled 62 patients in the first year, all with early ARDS, deeply sedated and often paralyzed, who were switched to protective volume-controlled ventilation with standard settings. Esophageal pressure measure was added to patients with moderate and severe ARDS [4]. Target physiological measurements included in the clinical report and registry were: total positive endexpiratory pressure (PEEP), peak pressure, plateau pressure, intrinsic PEEP, driving pressure, respiratory system compliance, resistance, end-expiratory transpulmonary pressure, end-inspiratory transpulmonary pressure, lung compliance, chest wall compliance, transpulmonary plateau pressure, oxygenation, and hemodynamic response to a 3–5 cmH2O PEEP change [5], and (de)recruitment obtained at clinical PEEP by an abrupt 10 cmH2O PEEP decrease [6]. In the present analysis, at first the authors retrospectively looked at whether making these measurements available to the attending physician induced any change in ventilation settings. This was true in 67% of cases with a switch from pressure to volume control and PEEP change as the most frequent adjustments. Secondly, authors assessed whether the changes in ventilation settings ameliorated physiological variables known to be associated with patients’ clinical outcome: oxygenation index improved and plateau and driving pressure decreased. Finally, authors investigated whether the changes in ventilation settings were consistent with the physiological report findings and described how the attending physician introduced PEEP changes consistent with the indications suggested by the physiological assessments. The study by Chen and colleagues obviously has limitations: it is a retrospective observational analysis describing an association between measuring advanced respiratory mechanics, changes in ventilation settings, and improvement of respiratory physiology that does not allow any description of causal relationship between these entities; it was performed in a single academic center with experience in conducting physiologic studies and clinical trials on mechanical ventilation for many years [5], making generalizability of the results difficult; the respiratory mechanics test was performed only once, while lung * Correspondence: antonio.pesenti@unimi.it Department of Pathophysiology and Transplantation, University of Milan, Milan, Italy Department of Anesthesia, Critical Care and Emergency, Fondazione IRCCS Ca’ Granda Ospedale Maggiore Policlinico, Via F. Sforza 35, 20122 Milan, Italy Full list of author information is available at the end of the article

Respiratory support after extubation: noninvasive ventilation or high-flow nasal cannula, as appropriate

© The Author(s) 2017. This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. Editorial Decreasing the duration of invasive mechanical ventilation by early safe extubation is a major clinical goal in intensive care unit (ICU) [1]. Prolonged intubation increases the risk of ventilator-induced lung injury, ventilator-induced diaphragm dysfunction, myopathy and infections. Nonetheless, patients’ management in the post-extubation period can be challenging and every effort should be made to avoid re-intubation, which is associated with significantly increased morbidity and mortality [1]. To this end, in this issue of the “Annals of Intensive Care,” Dr. Fernandez and colleagues report findings from a randomized controlled trial comparing low-flow oxygen supplied through nasal prongs or facial mask versus high-flow nasal cannula (HFNC) for 24 h after extubation as respiratory supports in patients at high risk of extubation failure [2]. This is the third large clinical trial recently published by the research group of Dr. Fernandez on the same topic, the other two being comparisons of HFNC versus noninvasive ventilation (NIV) in high-risk patients and of HFNC versus standard oxygen in low risk [3, 4]. In this issue study [2], patients’ population consisted of adult critically ill patients receiving mechanical ventilation for more than 12 h, considered as high risk of extubation failure and extubated after successful spontaneous breathing trial (SBT). High risk of extubation failure was defined as the presence of at least one among the following: age above 65 years old, heart failure, moderate or severe chronic obstructive pulmonary disease, APACHE II score higher than 12, body mass index above 30 kg/ m2, weak cough with abundant secretions, more than one SBT failure and/or mechanical ventilation for more than 7 days. The primary study outcome was the development of respiratory failure within 72 h after extubation, with an expected incidence of 28% in the conventional oxygen group versus 21% in the HFNC group. Re-intubation, length of stay and mortality were secondary outcomes. We must underline that the study has several limitations, in part acknowledged by the authors. First, avoiding use of NIV in high-risk patients might pose serious ethical issues as it might be failure to apply a treatment that was clearly shown to improve clinical outcome [5]. Second, the planned sample size for the primary outcome was 1184 patients (592 per arm), but the study was stopped at 155 due to slow recruitment (average of 1.6 patients per unit per month). Third, it is questionable whether assessment of the risk of extubation failure should be performed beforehand without any post-extubation reassessment: For example, a patient with early signs of respiratory failure (e.g., desaturation within 1 h from extubation) but no pre-defined risk factors might be regarded as more at risk than a patient presenting only some pre-extubation risk factors. Fourth, HFNC was arbitrarily implemented for 24 h only, while in everyday clinical practice, its discontinuation would more likely be based on the patient’s clinical evolution. Fifth, no physiologic test was performed to guide randomization (i.e., predictive enrichment: HFNC could have been implemented only in patients who have decreased respiratory rate after 30 min of treatment). Finally, patients developing hypercapnia during the SBT were excluded; thus, findings from this study do not apply to this population, which might be the most clinically relevant [5] and should be considered as post-extubation NIV application. Despite these limitations, we must recognize that study findings on the role of HFNC in the post-extubation period are relevant and encouraging: Incidence of respiratory failure reflected the hypothesized reduction granted by HFNC and re-intubation somehow Open Access

ABO blood types and major outcomes in patients with acute hypoxaemic respiratory failure: A multicenter retrospective cohort study

Introduction ABO blood type A was reported to correlate with an increased risk of acute respiratory distress syndrome (ARDS) in white patients with severe sepsis and major trauma compared with patients with other blood types. Information regarding ABO phenotypes and major outcomes in patients with ARDS is unavailable. The primary aim was to determine the relationship between ABO blood type A and intensive care unit (ICU) mortality in patients with acute hypoxemic respiratory failure (AHRF). The secondary aim was to describe the association between ABO blood type A and ICU length of stay (LOS) in this study population. Methods In a multicenter, retrospective cohort study, we collected the clinical records of patients admitted from January 2012 to December 2014 in five ICUs of Northern Italy. We included adult white patients admitted to the ICU who were diagnosed with AHRF requiring mechanical ventilation. Results The electronic records of 1732 patients with AHRF were reviewed. The proportion of patients with ABO blood type A versus other blood types was 39.9% versus 60.1%. ICU mortality (25%) and ICU LOS (median [interquartile range], 5 [2–12] days) were not different when stratified by ABO blood type (ICU mortality, overall p value = 0.905; ICU LOS, overall p value = 0.609). SAPSII was a positive predictor of ICU mortality (odds ration [OR], 32.80; 95% confidence interval [CI], 18.80–57.24; p < 0.001) and ICU LOS (β coefficient, 0.55; 95% CI, 0.35–0.75; p < 0.001) at multivariate analyses, whereas ABO blood type did not predict ICU outcome when forced into the model. Conclusion ABO blood type did not correlate with ICU mortality and ICU LOS in adult patients with AHRF who were mechanically ventilated.

Impact of flow and temperature on patient comfort during respiratory support by high-flow nasal cannula

BackgroundThe high-flow nasal cannula (HFNC) delivers up to 60xa0l/min of humidified air/oxygen blend at a temperature close to that of the human body. In this study, we tested whether higher temperature and flow decrease patient comfort. In more severe patients, instead, we hypothesized that higher flow might be associated with improved comfort.MethodsA prospective, randomized, cross-over study was performed on 40 acute hypoxemic respiratory failure (AHRF) patients (PaO2/FiO2u2009≤u2009300u2009+u2009pulmonary infiltrates + exclusion of cardiogenic edema) supported by HFNC. The primary outcome was the assessment of patient comfort during HFNC delivery at increasing flow and temperature. Two flows (30 and 60xa0l/min), each combined with two temperatures (31 and 37xa0°C), were randomly applied for 20xa0min (four steps per patient), leaving clinical FiO2 unchanged. Toward the end of each step, the following were recorded: comfort by Visual Numerical Scale ranging between 1 (extreme discomfort) and 5 (very comfortable), together with respiratory parameters. A subgroup of more severe patients was defined by clinical FiO2u2009≥u200945%.ResultsPatient comfort was reported as significantly higher during steps at the lower temperature (31xa0°C) in comparison to 37xa0°C, with the HFNC set at both 30 and 60xa0l/min (pu2009<u20090.0001). Higher flow, however, was not associated with poorer comfort.In the subgroup of patients with clinical FiO2u2009≥u200945%, both lower temperature (31xa0°C) and higher HFNC flow (60xa0l/min) led to higher comfort (pu2009<u20090.01).ConclusionsHFNC temperature seems to significantly impact the comfort of AHRF patients: for equal flow, lower temperature could be more comfortable. Higher flow does not decrease patient comfort; at variance, it improves comfort in the more severely hypoxemic patient.

High flow nasal cannula improves lung aeration and enhances CO2 removal in hypoxemic critically ill patients

High-flow nasal cannula (HFNC) is a non-invasive respiratory support increasingly applied to hypoxemic acute respiratory failure patients. HFNC decreases dyspnea, improves oxygenation and enhances patients comfort.

NAVA: Applications and Limitations

In recent years there has been an increasing interest in the use of partial ventilatory support modes not only as weaning techniques but also in the acute phases of respiratory failure. During assisted spontaneous breathing, a variable proportion of the work of breathing is provided by the ventilator, to unload the patient’s respiratory muscles [1]. Multiple ventilator modes are currently available for assisted spontaneous breathing: among these, neurally-adjusted ventilator assist (NAVA) is undergoing extensive clinical evaluation. NAVA is conceptually different from any other mode of ventilation, since the ventilator is not controlled by the ‘pneumatic’ output of respiratory muscles (i. e., a change in airway pressure or flow) but directly by the neural activity of respiratory centers, expressed by the diaphragm electromyogram (EAdi) [2].