Marcos Melo

Columbia University | CU · Department of Anesthesiology

Mechanical ventilation exposes the lung to injurious stresses and strains that can negatively affect clinical outcomes in acute respiratory distress syndrome or cause pulmonary complications after general anesthesia. Excess global lung strain, estimated as increased respiratory system driving pressure, is associated with mortality related to mechan...

BACKGROUND Postoperative pulmonary complications (PPCs) occur frequently after cardiac surgery. Absolute postoperative values of biomarkers of inflammation (interleukin [IL]-6, IL-8, and tumor necrosis factor-alpha [TNF-α]) and alveolar epithelial injury (soluble receptor for advanced glycation end-products [sRAGE]) have been associated with hypoxi...

Intraoperative cardiopulmonary variables are well-known predictors of postoperative pulmonary complications (PPC), traditionally quantified by median values over the duration of surgery. However, it is unknown whether cardiopulmonary instability, or wider intra-operative variability of the same metrics, is distinctly associated with PPC risk and se...

Regional pulmonary perfusion (Q) has been investigated using blood volume (Fb) imaging as an easier-to-measure surrogate. However, it is unclear if changing pulmonary conditions could affect their relationship. We hypothesized that vascular changes in early acute respiratory distress syndrome (ARDS) affect Q and Fb differently. Five sheep were anes...

As a team studying the predictors of complications after lung surgery, we have encountered high missingness of data on one-lung ventilation (OLV) start and end times due to high clinical workload and cognitive overload during surgery. Such missing data limit the precision and clinical applicability of our findings. We hypothesized that available in...

Background Positive end-expiratory pressure (PEEP) individualized to a maximal respiratory system compliance directly implies minimal driving pressures with potential outcome benefits, yet, raises concerns on static and dynamic overinflation, strain and cyclic recruitment. Detailed accurate assessment and understanding of these has been hampered by...

Study objective: Postoperative respiratory failure is a major surgical complication and key quality metric. Existing prediction tools underperform, are limited to specific populations, and necessitate manual calculation. This limits their implementation. We aimed to create an improved, machine learning powered prediction tool with ideal characteri...

Regional pulmonary perfusion (Q) has been investigated using blood volume (Fb) imaging as an easier-to-measure surrogate. However, it is unclear if changing pulmonary conditions could affect their relationship. We hypothesized that vascular changes in early acute respiratory distress syndrome (ARDS) affect Q and Fb differently. Five sheep were anes...

Introduction: Lung perfusion magnitude and distribution are essential for oxygenation and, potentially, lung inflammation and protection during acute respiratory distress syndrome (ARDS). Yet, perfusion patterns and their relationship to inflammation are unknown pre-ARDS. We aimed to assess perfusion/density ratios and spatial perfusion-density di...

Patients requiring neuromuscular block for anaesthesia have a higher risk of adverse postoperative outcomes. The choice of reversal drug and its corresponding dose is critical for improving clinical outcomes. Although drug costs are higher for sugammadex relative to neostigmine, additional factors need to be considered when choosing one drug over t...

Background Postoperative pulmonary complications (PPCs) are a major cause of morbidity and mortality after open abdominal surgery. Optimized perioperative lung expansion may minimize the synergistic factors responsible for the multiple-hit perioperative pulmonary dysfunction. This ongoing study will assess whether an anesthesia-centered bundle focu...

Multiple thoracic imaging modalities have been developed to link structure to function in the diagnosis and monitoring of lung disease. Volumetric computed tomography (CT) renders three-dimensional maps of lung structures and may be combined with positron emission tomography (PET) to obtain dynamic physiological data. Magnetic resonance imaging (MR...

Acute respiratory distress syndrome (ARDS) is a common lung disorder that involves severe inflammatory damage in the pulmonary barrier, but the underlying mechanisms remain elusive. Here, we demonstrated that pulmonary macrophages originating from ARDS patients and mice caused by bacteria were characterized by increased expression of ferroportin (F...

During hypoxia or inflammation, extracellular adenosine levels are elevated. Studies using pharmacologic approaches or genetic animal models pertinent to extracellular adenosine signaling implicate this pathway in attenuating hypoxia-associated inflammation. There are four distinct adenosine receptors. Of these, it is not surprising that the Adora2...

Background: The impact of high vs low intraoperative tidal volumes on postoperative respiratory complications remains unclear. We hypothesised that the effect of intraoperative tidal volume on postoperative respiratory complications is dependent on respiratory system elastance. Methods: We retrospectively recorded tidal volume (Vt; ml kg-1 ideal...

BACKGROUND Reintubation after lung cancer resection is an important quality metric due to increased disability, mortality and cost. However, no validated predictive instrument is in use to reduce reintubation after lung resection. We aimed to create and validate the PRediction Of REintubation After Lung cancer resection (PROREAL) score. METHODS We...

Adjuvant regional anesthesia is often selected for patients or procedures with high risk of pulmonary complications after general anesthesia. The benefit of adjuvant regional anesthesia to reduce postoperative pulmonary complications remains uncertain. In a prospective observational multicenter study, patients scheduled for non-cardiothoracic surge...

Atelectasis is a frequent clinical condition, yet knowledge is limited and controversial on its biological contribution towards lung injury. We assessed the regional proteomics of atelectatic versus normally-aerated lung tissue to test the hypothesis that immune and alveolar-capillary barrier functions are compromised by purely atelectasis and dysr...

The present study describes the magnitude and spatial distribution of lung strain in healthy anesthetized, mechanically ventilated dogs with and without positive end-expiratory pressure (PEEP). Total lung strain (LSTOTAL) has a dynamic (LSDYNAMIC) and a static (LSSTATIC) component. Due to lung heterogeneity, global lung strain may not accurately re...

Background The aim of this analysis is to determine geo–economic variations in epidemiology, ventilator settings and outcome in patients receiving general anesthesia for surgery. Methods Posthoc analysis of a worldwide study in 29 countries. Lower and upper middle–income countries (LMIC and UMIC), and high–income countries (HIC) were compared. The...

The practice of thoracic anesthesia involves not only patients with impaired pulmonary function, it also necessitates dynamic changes in ventilation with resulting impact on perfusion and ventilation/perfusion matching. Thus it is imperative that the thoracic anesthesiologist has a thorough understanding of the normal pulmonary physiology, as well...

Background Geoeconomic variations in epidemiology, the practice of ventilation, and outcome in invasively ventilated intensive care unit (ICU) patients without acute respiratory distress syndrome (ARDS) remain unexplored. In this analysis we aim to address these gaps using individual patient data of four large observational studies. Methods In thi...

The development of pulmonary atelectasis is common in the surgical patient. Pulmonary atelectasis can cause various degrees of gas exchange and respiratory mechanics impairment during and after surgery. In its most serious presentations, lung collapse could contribute to postoperative respiratory insufficiency, pneumonia, and worse overall clinical...

Pulmonary atelectasis is common in the perioperative period. Physiologically, it is produced when collapsing forces derived from positive pleural pressure and surface tension overcome expanding forces from alveolar pressure and parenchymal tethering. Atelectasis impairs blood oxygenation and reduces lung compliance. It is increasingly recognized th...

A 75-year-old woman with a history of right-upper lobectomy for adenocarcinoma presented for a right completion pneumonectomy due to 2 new fluorodeoxyglucose-avid densities on the remaining lung. After uneventful anesthetic induction and surgical resection with modest blood loss, the patient developed refractory hypoxemia on emergence without signi...

Background It is uncertain whether the association of the intraoperative driving pressure (ΔP) with postoperative pulmonary complications (PPCs) depends on the surgical approach during abdominal surgery. Our primary objective was to determine and compare the association of time–weighted average ΔP (ΔP TW ) with PPCs. We also tested the association...

BACKGROUND One key element of lung-protective ventilation is the use of a low tidal volume (VT). A sex difference in use of low tidal volume ventilation (LTVV) has been described in critically ill ICU patients. OBJECTIVES The aim of this study was to determine whether a sex difference in use of LTVV also exists in operating room patients, and if pr...

Background: Anaemia is frequently recorded during preoperative screening and has been suggested to affect outcomes after surgery negatively. Objectives: The objectives were to assess the frequency of moderate to severe anaemia and its association with length of hospital stay. Design: Post hoc analysis of the international observational prospec...

To evaluate a compact and easily interpretable 4-parameter model describing the shape of the volumetric capnogram, and the resulting estimates of anatomical dead space (VDAW) and Phase III (alveolar plateau) slope (SIII). Data from of 8 mildly-endotoxemic pre-acute respiratory distress syndrome sheep were fitted to the proposed 4-parameter model (4...

Background: Limited information is available regarding intraoperative ventilator settings and the incidence of postoperative pulmonary complications (PPCs) in patients undergoing neurosurgical procedures. The aim of this post-hoc analysis of the 'Multicentre Local ASsessment of VEntilatory management during General Anaesthesia for Surgery' (LAS VE...

Background: It is uncertain whether associations between driving pressure (ΔP) during and occurrence of pulmonary complications after abdominal surgery depend on the surgical approach. Our primary objective was to test the time–weighted average ΔP (ΔPTW) association with postoperative pulmonary complications and our secondary objective was to test...

Background International data on the epidemiology, ventilation practice, and outcomes in patients undergoing abdominal robotic-assisted surgery (RAS) are lacking. The aim of the study was to assess the incidence of postoperative pulmonary complications (PPCs), and to describe ventilator management after abdominal RAS. Methods This was an internati...

Positron emission tomography (PET) with 18F-fluorodeoxyglucose (18F-FDG) has been increasingly applied, predominantly in the research setting, to study drug effects and pulmonary biology and monitor disease progression and treatment outcomes in lung diseases, disorders that interfere with gas exchange through alterations of the pulmonary parenchyma...

Background We aimed to investigate the physiological mechanism and spatial distribution of increased physiological dead‐space, an early marker of ARDS mortality, in the initial stages of ARDS. We hypothesized that: increased dead‐space results from the spatial redistribution of pulmonary perfusion, not ventilation; such redistribution is not relate...

Background: In the Protective Ventilation in Cardiac Surgery (PROVECS) randomized, controlled trial, an open-lung ventilation strategy did not improve postoperative respiratory outcomes after on-pump cardiac surgery. In this prespecified subanalysis, the authors aimed to assess the regional distribution of ventilation and plasma biomarkers of lung...

Background: Pulmonary atelectasis is frequent in clinical settings. Yet there is limited mechanistic understanding and substantial clinical and biologic controversy on its consequences. The authors hypothesize that atelectasis produces local transcriptomic changes related to immunity and alveolar-capillary barrier function conducive to lung injury...

Background: Intraoperative mechanical ventilation may influence postoperative pulmonary complications (PPCs). Current practice during thoracic surgery is not well described. Methods: This is a post-hoc analysis of the prospective multicenter cross-sectional LAS VEGAS study focusing on patients who underwent thoracic surgery. Consecutive adult pa...

Background Higher intraoperative driving pressures (ΔP) are associated with increased postoperative pulmonary complications (PPC). We hypothesised that dynamic adjustment of PEEP throughout abdominal surgery reduces ΔP, maintains positive end-expiratory transpulmonary pressures (Ptp_ee) and increases respiratory system static compliance (Crs) with...

Rationale and Objectives Pulmonary atelectasis presumably promotes and facilitates lung injury. However, data are limited on its direct and remote relation to inflammation. We aimed to assess regional 2-deoxy-2-[¹⁸F]-fluoro-D-glucose (¹⁸F-FDG) kinetics representative of inflammation in atelectatic and normally aerated regions in models of early lun...

Background High ventilatory frequencies increase static lung strain and possibly lung stress by shortening expiratory time, increasing intrathoracic pressure, and causing dynamic hyperinflation. We hypothesised that high intraoperative ventilatory frequencies were associated with postoperative respiratory complications. Methods In this retrospecti...

Background: Mechanical ventilation with variable tidal volumes (VT) may improve lung function and reduce ventilator-induced lung injury in experimental acute respiratory distress syndrome (ARDS). However, previous investigations were limited to less than 6 h, and control groups did not follow clinical standards. We hypothesised that 24 h of mechan...

Purpose To evaluate whether a perioperative open-lung ventilation strategy prevents postoperative pulmonary complications after elective on-pump cardiac surgery. Methods In a pragmatic, randomized, multicenter, controlled trial, we assigned patients planned for on-pump cardiac surgery to either a conventional ventilation strategy with no ventilati...

Background: Pneumoperitoneum and nonphysiological positioning required for robotic surgery increase cardiopulmonary risk because of the use of larger airway pressures (Paws) to maintain tidal volume (VT). However, the quantitative partitioning of respiratory mechanics and transpulmonary pressure (PL) during robotic surgery is not well described. W...

The physiologic concept, pathophysiologic implications, and clinical relevance and application of driving pressure and transpulmonary pressure to prevent ventilator-induced lung injury are discussed.

Objectives: To determine the impact of positive end-expiratory pressure during mechanical ventilation with and without spontaneous breathing activity on regional lung inflammation in experimental nonsevere acute respiratory distress syndrome. Design: Laboratory investigation. Setting: University hospital research facility. Subjects: Twenty-f...

Background: The aim of this post hoc analysis of a large cohort study was to evaluate the association between night-time surgery and the occurrence of intraoperative adverse events (AEs) and postoperative pulmonary complications (PPCs). Methods: LAS VEGAS (Local Assessment of Ventilatory Management During General Anesthesia for Surgery) was a prosp...

BACKGROUND: The aim of this post hoc analysis of a large cohort study was to evaluate the association between night-time surgery and the occurrence of intraoperative adverse events (AEs) and postoperative pulmonary complications (PPCs). METHODS: LAS VEGAS (Local Assessment of Ventilatory Management During General Anesthesia for Surgery) was a pros...

Rationale: Low tidal volume ventilation might protect healthy lungs from volutrauma but lead to inflammation from other mechanisms, namely alveolar derecruitment and the ensuing alveolar collapse and reexpansion. Objective: We hypothesized that the different mechanisms of low and high volume injury would be reflected in different mechanical prop...