Savino Spadaro

Estimation of Patient’s Inspiratory Effort From the Electrical Activity of the Diaphragm*

Objectives:To calculate an index (termed Pmusc/Eadi index) relating the pressure generated by the respiratory muscles (Pmusc) to the electrical activity of the diaphragm (Eadi), during assisted mechanical ventilation and to assess if the Pmusc/Eadi index is affected by the type and level of ventilator assistance. The Pmusc/Eadi index was also used to measure the patient’s inspiratory effort from Eadi without esophageal pressure. Design:Crossover study. Setting:One general ICU. Patients:Ten patients undergoing assisted ventilation. Intervention:Pressure support and neurally adjusted ventilator assist delivered, each, at three levels of ventilatory assistance. Measurement and Main Results:Airways flow and pressure, esophageal pressure, and Eadi were continuously recorded. Sixty tidal volumes for each ventilator settings were analyzed off-line, at three time points during inspiration. For each time point, Pmusc/Eadi index was calculated. Pmusc/Eadi index was also calculated from airway pressure drop during end-expiratory occlusions. Pmusc/Eadi index was very variable among patients, but within one patient it was not affected by type and level of ventilator assistance. Pmusc/Eadi index decreased during the inspiration. Pmusc/Eadi index obtained during an occlusion from airway pressure swing was tightly correlated with that derived from esophageal pressure during tidal ventilation and allowed to estimate pressure time product. Conclusions:Pmusc is tightly related to Eadi, by a proportionality coefficient that we termed Pmusc/Eadi index, stable within each patient under different conditions of ventilator assistance. The derivation of the Pmusc/Eadi index from Eadi and airway pressure during an expiratory occlusion enables a continuous estimate of patient’s inspiratory effort.

Effects of Recruitment Maneuver and Positive End-expiratory Pressure on Respiratory Mechanics and Transpulmonary Pressure during Laparoscopic Surgery

Background:The authors tested the hypothesis that during laparoscopic surgery, Trendelenburg position and pneumoperitoneum may worsen chest wall elastance, concomitantly decreasing transpulmonary pressure, and that a protective ventilator strategy applied after pneumoperitoneum induction, by increasing transpulmonary pressure, would result in alveolar recruitment and improvement in respiratory mechanics and gas exchange. Methods:In 29 consecutive patients, a recruiting maneuver followed by positive end-expiratory pressure 5 cm H2O maintained until the end of surgery was applied after pneumoperitoneum induction. Respiratory mechanics, gas exchange, blood pressure, and cardiac index were measured before (TBSL) and after pneumoperitoneum with zero positive end-expiratory pressure (TpreOLS), after recruitment with positive end-expiratory pressure (TpostOLS), and after peritoneum desufflation with positive end-expiratory pressure (Tend). Results:Esophageal pressure was used for partitioning respiratory mechanics between lung and chest wall (data are mean ± SD): on TpreOLS, chest wall elastance (Ecw) and elastance of the lung (EL) increased (8.2 ± 0.9 vs. 6.2 ± 1.2 cm H2O/L, respectively, on TBSL; P = 0.00016; and 11.69 ± 1.68 vs. 9.61 ± 1.52 cm H2O/L on TBSL; P = 0.0007). On TpostOLS, both chest wall elastance and EL decreased (5.2 ± 1.2 and 8.62 ± 1.03 cm H2O/L, respectively; P = 0.00015 vs. TpreOLS), and PaO2/inspiratory oxygen fraction improved (491 ± 107 vs. 425 ± 97 on TpreOLS; P = 0.008) remaining stable thereafter. Recruited volume (the difference in lung volume for the same static airway pressure) was 194 ± 80 ml. PplatRS remained stable while inspiratory transpulmonary pressure increased (11.65 + 1.37 cm H2O vs. 9.21 + 2.03 on TpreOLS; P = 0.007). All respiratory mechanics parameters remained stable after abdominal desufflation. Hemodynamic parameters remained stable throughout the study. Conclusions:In patients submitted to laparoscopic surgery in Trendelenburg position, an open lung strategy applied after pneumoperitoneum induction increased transpulmonary pressure and led to alveolar recruitment and improvement of Ecw and gas exchange.

Effects of Sigh on Regional Lung Strain and Ventilation Heterogeneity in Acute Respiratory Failure Patients Undergoing Assisted Mechanical Ventilation

Objective:In acute respiratory failure patients undergoing pressure support ventilation, a short cyclic recruitment maneuver (Sigh) might induce reaeration of collapsed lung regions, possibly decreasing regional lung strain and improving the homogeneity of ventilation distribution. We aimed to describe the regional effects of different Sigh rates on reaeration, strain, and ventilation heterogeneity, as measured by thoracic electrical impedance tomography. Design:Prospective, randomized, cross-over study. Setting:General ICU of a single university-affiliated hospital. Patients:We enrolled 20 critically ill patients intubated and mechanically ventilated with PaO2/FIO2 up to 300 mm Hg and positive end-expiratory pressure at least 5 cm H2O (15 with acute respiratory distress syndrome), undergoing pressure support ventilation as per clinical decision. Interventions:Sigh was added to pressure support ventilation as a 35 cm H2O continuous positive airway pressure period lasting 3–4 seconds at different rates (no-Sigh vs 0.5, 1, and 2 Sigh(s)/min). All study phases were randomly performed and lasted 20 minutes. Measurements and Main Results:In the last minutes of each phase, we measured arterial blood gases, changes in end-expiratory lung volume of nondependent and dependent regions, tidal volume reaching nondependent and dependent lung (Vtnondep and Vtdep), dynamic intratidal ventilation heterogeneity, defined as the average ratio of Vt reaching nondependent/Vt reaching dependent lung regions along inspiration (VtHit). With Sigh, oxygenation improved (p < 0.001 vs no-Sigh), end-expiratory lung volume of nondependent and dependent regions increased (p < 0.01 vs no-Sigh), Vtnondep showed a trend to reduction, and Vtdep significantly decreased (p = 0.11 and p < 0.01 vs no-Sigh, respectively). VtHit decreased only when Sigh was delivered at 0.5/min (p < 0.05 vs no-Sigh), while it did not vary during the other two phases. Conclusions:Sigh decreases regional lung strain and intratidal ventilation heterogeneity. Our study generates the hypothesis that in ventilated acute respiratory failure patients, Sigh may enhance regional lung protection.

Control of Respiratory Drive and Effort in Extracorporeal Membrane Oxygenation Patients Recovering from Severe Acute Respiratory Distress Syndrome

Background:The amount of extracorporeal carbon dioxide removal may influence respiratory drive in acute respiratory distress syndrome (ARDS) patients undergoing extracorporeal membrane oxygenation (ECMO). The authors evaluated the effects of different levels of extracorporeal carbon dioxide removal in patients recovering from severe ARDS undergoing pressure support ventilation (PSV) and neurally adjusted ventilatory assist (NAVA). Methods:The authors conducted a prospective, randomized, crossover study on eight spontaneously breathing ARDS patients undergoing venovenous ECMO since 28 ± 20 days. To modulate carbon dioxide extraction, ECMO gas flow (GF) was decreased from baseline resting protective conditions (i.e., GF100%, set to obtain pressure generated in the first 100 ms of inspiration against an occluded airway less than 2 cm H2O, respiratory rate less than or equal to 25 bpm, tidal volume less than 6 ml/kg, and peak airway pressure less than 25 cm H2O) to GF50%-GF25%-GF0% during both PSV and NAVA (random order for ventilation mode). Continuous recordings of airway pressure and flow and esophageal pressure were obtained and analyzed during all study phases. Results:At higher levels of extracorporeal carbon dioxide extraction, pressure generated in the first 100 ms of inspiration against an occluded airway decreased from 2.8 ± 2.7 cm H2O (PSV, GF0%) and 3.0 ± 2.1 cm H2O (NAVA, GF0%) to 0.9 ± 0.5 cm H2O (PSV, GF100%) and 1.0 ± 0.8 cm H2O (NAVA, GF100%; P < 0.001) and patients’ inspiratory muscle pressure passed from 8.5 ± 6.3 and 6.5 ± 5.5 cm H2O to 4.5 ± 3.1 and 4.2 ± 3.7 cm H2O (P < 0.001). In time, decreased inspiratory drive and effort determined by higher carbon dioxide extraction led to reduction of tidal volume from 6.6 ± 0.9 and 7.5 ± 1.2 ml/kg to 4.9 ± 0.8 and 5.3 ± 1.3 ml/kg (P < 0.001) and of peak airway pressure from 21 ± 3 and 25 ± 4 cm H2O to 21 ± 3 and 21 ± 5 cm H2O (P < 0.001). Finally, transpulmonary pressure linearly decreased when the amount of carbon dioxide extracted by ECMO increased (R2 = 0.823, P < 0.001). Conclusions:In patients recovering from ARDS undergoing ECMO, the amount of carbon dioxide removed by the artificial lung may influence spontaneous breathing. The effects of carbon dioxide removal on spontaneous breathing during the earlier acute phases of ARDS remain to be elucidated.

Aeromonas sobria necrotizing fasciitis and sepsis in an immunocompromised patient: a case report and review of the literature

IntroductionAeromonas veronii biovar sobria is a rare cause of bacteremia, with several studies indicating that this isolate may be of particular clinical significance since it is enterotoxin producing. A wide spectrum of infections has been associated with Aeromonas species in developing countries that include gastroenteritis, wound infections, septicemia and lung infections. This infection, caused by Aeromonas species, is usually more severe in immunocompromised than immunocompetent individuals. We here describe a case of soft tissue infection and severe sepsis due to Aeromonas sobria in an immunocompromised patient.Case presentationA 74-year-old Caucasian man with a clinical history of chronic lymphocytic leukemia and immune thrombocytopenia, periodically treated with steroids, was admitted to our Intensive Care Unit because of necrotizing fasciitis and multiorgan failure due to Aeromonas sobria, which resulted in his death. The unfortunate coexistence of a Candida albicans infection played a key role in the clinical course.ConclusionOur experience suggests that early recognition and aggressive medical and surgical therapy are determinants in the treatment of severe septicemia caused by an Aeromonas sobria in an immunocompromised patient.

Effect of positive end-expiratory pressure on pulmonary shunt and dynamic compliance during abdominal surgery

BACKGROUND General anaesthesia decreases pulmonary compliance and increases pulmonary shunt due to the development of atelectasis. The presence of capnoperitoneum during laparoscopic surgery may further decrease functional residual capacity, promoting an increased amount of atelectasis compared with laparotomy. The aim of this study was to evaluate the effects of different levels of positive end-expiratory pressure (PEEP) in both types of surgery and to investigate whether higher levels of PEEP should be used during laparoscopic surgery. METHODS This prospective observational study included 52 patients undergoing either laparotomy or laparoscopic surgery. Three levels of PEEP were applied in random order: (1) zero (ZEEP), (2) 5 cmH2O and (3) 10 cmH2O. Pulmonary shunt and ventilation/perfusion mismatch were assessed by the automatic lung parameter estimator system. RESULTS Pulmonary shunt was similar in both groups. However, in laparotomy, a PEEP of 5 cmH2O significantly decreased shunt when compared with ZEEP (12 vs 6%; P=0.001), with additional PEEP having no further effect. In laparoscopic surgery, a significant reduction in shunt (13 vs 6%; P=0.001) was obtained only at a PEEP of 10 cmH2O. Although laparoscopic surgery was associated with a lower pulmonary compliance, increasing levels of PEEP were able to ameliorate it in both groups. CONCLUSION Both surgeries have similar negative effects on pulmonary shunt, while the presence of capnoperitoneum reduced only the pulmonary compliance. It appears that a more aggressive PEEP level is required to reduce shunt and to maximize compliance in case of laparoscopic surgery.

Variation of poorly ventilated lung units (silent spaces) measured by electrical impedance tomography to dynamically assess recruitment

BackgroundAssessing alveolar recruitment at different positive end-expiratory pressure (PEEP) levels is a major clinical and research interest because protective ventilation implies opening the lung without inducing overdistention. The pressure-volume (P-V) curve is a validated method of assessing recruitment but reflects global characteristics, and changes at the regional level may remain undetected. The aim of the present study was to compare, in intubated patients with acute hypoxemic respiratory failure (AHRF) and acute respiratory distress syndrome (ARDS), lung recruitment measured by P-V curve analysis, with dynamic changes in poorly ventilated units of the dorsal lung (dependent silent spaces [DSSs]) assessed by electrical impedance tomography (EIT). We hypothesized that DSSs might represent a dynamic bedside measure of recruitment.MethodsWe carried out a prospective interventional study of 14 patients with AHRF and ARDS admitted to the intensive care unit undergoing mechanical ventilation. Each patient underwent an incremental/decremental PEEP trial that included five consecutive phases: PEEP 5 and 10 cmH2O, recruitment maneuver + PEEP 15 cmH2O, then PEEP 10 and 5 cmH2O again. We measured, at the end of each phase, recruitment from previous PEEP using the P-V curve method, and changes in DSS were continuously monitored by EIT.ResultsPEEP changes induced alveolar recruitment as assessed by the P-V curve method and changes in the amount of DSS (p < 0.001). Recruited volume measured by the P-V curves significantly correlated with the change in DSS (rs = 0.734, p < 0.001). Regional compliance of the dependent lung increased significantly with rising PEEP (median PEEP 5 cmH2O = 11.9 [IQR 10.4–16.7] ml/cmH2O, PEEP 15 cmH2O = 19.1 [14.2–21.3] ml/cmH2O; p < 0.001), whereas regional compliance of the nondependent lung decreased from PEEP 5 cmH2O to PEEP 15 cmH2O (PEEP 5 cmH2O = 25.3 [21.3–30.4] ml/cmH2O, PEEP 15 cmH2O = 20.0 [16.6–22.8] ml/cmH2O; p <0.001). By increasing the PEEP level, the center of ventilation moved toward the dependent lung, returning to the nondependent lung during the decremental PEEP steps.ConclusionsThe variation of DSSs dynamically measured by EIT correlates well with lung recruitment measured using the P-V curve technique. EIT might provide useful information to titrate personalized PEEP.Trial registrationClinicalTrials.gov, NCT02907840. Registered on 20 September 2016.

Simulation training for residents focused on mechanical ventilation: A randomized trial using mannequin-based versus computer-based simulation

Introduction Advances in knowledge regarding mechanical ventilation (MV), in particular lung-protective ventilation strategies, have been shown to reduce mortality. However, the translation of these advances in knowledge into better therapeutic performance in real-life clinical settings continues to lag. High-fidelity simulation with a mannequin allows students to interact in lifelike situations; this may be a valuable addition to traditional didactic teaching. The purpose of this study is to compare computer-based and mannequin-based approaches for training residents on MV. Methods This prospective randomized single-blind trial involved 50 residents. All participants attended the same didactic lecture on respiratory pathophysiology and were subsequently randomized into two groups: the mannequin group (n = 25) and the computer screen–based simulator group (n = 25). One week later, each underwent a training assessment using five different scenarios of acute respiratory failure of different etiologies. Later, both groups underwent further testing of patient management, using in situ high-fidelity simulation of a patient with acute respiratory distress syndrome. Results Baseline knowledge was not significantly different between the two groups (P = 0.72). Regarding the training assessment, no significant differences were detected between the groups. In the final assessment, the scores of only the mannequin group significantly improved between the training and final session in terms of either global rating score [3.0 (2.5–4.0) vs. 2.0 (2.0–3.0), P = 0.005] or percentage of key score (82% vs. 71%, P = 0.001). Conclusions Mannequin-based simulation has the potential to improve skills in managing MV.

Oxidative Stress and Endometriosis: A Systematic Review of the Literature

Endometriosis is one of the most common gynaecologic diseases in women of reproductive age. It is characterized by the presence of endometrial tissue outside the uterine cavity. The women affected suffer from pelvic pain and infertility. The complex etiology is still unclear and it is based on three main theories: retrograde menstruation, coelomic metaplasia, and induction theory. Genetics and epigenetics also play a role in the development of endometriosis. Recent studies have put the attention on the role of oxidative stress, defined as an imbalance between reactive oxygen species (ROS) and antioxidants, which may be implicated in the pathophysiology of endometriosis causing a general inflammatory response in the peritoneal cavity. Reactive oxygen species are intermediaries produced by normal oxygen metabolism and are inflammatory mediators known to modulate cell proliferation and to have deleterious effects. A systematic review was performed in order to clarify the different roles of oxidative stress and its role in the development of endometriosis. Several issues have been investigated: iron metabolism, oxidative stress markers (in the serum, peritoneal fluid, follicular fluid, peritoneal environment, ovarian cortex, and eutopic and ectopic endometrial tissue), genes involved in oxidative stress, endometriosis-associated infertility, and cancer development.

No relationship between red blood cell distribution width and microcirculatory alterations in septic patients

BACKGROUND Increased red cell distribution width (RDW), a quantitative measure of erythrocyte size variability, has been associated with increased mortality in critically ill patients. METHODS In this post-hoc analysis of prospectively collected data, we studied 122 septic patients with and without shock who had undergone sublingual microcirculatory assessment using Sidestream Dark Field (SDF) videomicroscopy. Patient demographics, comorbidities, the Acute Physiology and Chronic Health Evaluation (APACHE) II score on admission and the Sequential Organ Failure Assessment (SOFA) score on the day of the microcirculatory assessment were collected. The RDW was retrospectively collected on the day of the microcirculatory evaluation from the routine daily blood count analysis. RESULTS Median patient age was 68[55-77] years, and median APACHE II and SOFA scores were 22[17-28] and 10[8-12], respectively; ICU mortality was 43%. On the day of the microcirculatory analysis, the median RDW was 13.8[12.8-15.5]% and was elevated (>13.4%) in 74 (61%) patients. There was no correlation between RDW and microcirculatory parameters (functional capillary density, r2 = 0.12; proportion of small perfused vessels, r2 = 0.17; mean flow index, r2 = 0.14). RDW was not related to disease severity, the presence of shock or survival. CONCLUSIONS RDW is not associated with microcirculatory alterations or prognosis in septic patients.