Lorenzo Ball

Assessment of extravascular lung water by quantitative ultrasound and CT in isolated bovine lung

Lung ultrasonography (LUS) and computed tomography (CT) were compared for quantitative assessment of extravascular lung water (EVLW) in 10 isolated bovine lung lobes. LUS and CT were obtained at different inflation pressures before and after instillation with known amounts of hypotonic saline. A video-based quantitative LUS analysis was superior to both single-frame quantitative analysis and visual scoring in the assessment of EVLW. Video-based mean LUS intensity was strongly correlated with EVLW density (r(2)=0.87) but weakly correlated with mean CT attenuation (r(2)=0.49) and physical density (r(2)=0.49). Mean CT attenuation was weakly correlated with EVLW density (r(2)=0.62) but strongly correlated with physical density (r(2)=0.99). When the effect of physical density was removed by partial correlation analysis, EVLW density was significantly correlated with video-based LUS intensity (r(2)=0.75) but not mean CT attenuation (r(2)=0.007). In conclusion, these findings suggest that quantitative LUS by video gray-scale analysis can assess EVLW more reliably than LUS visual scoring or quantitative CT.

Monitoring respiration: What the clinician needs to know

A recent large prospective cohort study showed an unexpectedly high in-hospital mortality after major non-cardiac surgery in Europe, as well as a high incidence of postoperative pulmonary complications. The direct effect of postoperative respiratory complications on mortality is still under investigation, for intensive care unit (ICU) and in the perioperative period. Although respiratory monitoring has not been actually proven to affect in-hospital mortality, it plays an important role in patient care, leading to appropriate setting of ventilatory support as well as risk stratification. The aim of this article is to provide an overview of various respiratory monitoring techniques including the role of conventional and most recent methods in the perioperative period and in critically ill patients. The most recent techniques proposed for bedside respiratory monitoring, including lung imaging, are presented and discussed, comparing them to those actually considered as gold standards.

Modes of mechanical ventilation for the operating room

Most patients undergoing surgical procedures need to be mechanically ventilated, because of the impact of several drugs administered at induction and during maintenance of general anaesthesia on respiratory function. Optimization of intraoperative mechanical ventilation can reduce the incidence of post-operative pulmonary complications and improve the patients outcome. Preoxygenation at induction of general anaesthesia prolongs the time window for safe intubation, reducing the risk of hypoxia and overweighs the potential risk of reabsorption atelectasis. Non-invasive positive pressure ventilation delivered through different interfaces should be considered at the induction of anaesthesia morbidly obese patients. Anaesthesia ventilators are becoming increasingly sophisticated, integrating many functions that were once exclusive to intensive care. Modern anaesthesia machines provide high performances in delivering the desired volumes and pressures accurately and precisely, including assisted ventilation modes. Therefore, the physicians should be familiar with the potential and pitfalls of the most commonly used intraoperative ventilation modes: volume-controlled, pressure-controlled, dual-controlled and assisted ventilation. Although there is no clear evidence to support the advantage of any one of these ventilation modes over the others, protective mechanical ventilation with low tidal volume and low levels of positive end-expiratory pressure (PEEP) should be considered in patients undergoing surgery. The target tidal volume should be calculated based on the predicted or ideal body weight rather than on the actual body weight. To optimize ventilation monitoring, anaesthesia machines should include end-inspiratory and end-expiratory pause as well as flow-volume loop curves. The routine administration of high PEEP levels should be avoided, as this may lead to haemodynamic impairment and fluid overload. Higher PEEP might be considered during surgery longer than 3 h, laparoscopy in the Trendelenburg position and in patients with body mass index >35 kg/m(2). Large randomized trials are warranted to identify subgroups of patients and the type of surgery that can potentially benefit from specific ventilation modes or ventilation settings.

Quantitative Analysis of Lung Ultrasonography for the Detection of Community-Acquired Pneumonia: A Pilot Study

Background and Objective. Chest X-ray is recommended for routine use in patients with suspected pneumonia, but its use in emergency settings is limited. In this study, the diagnostic performance of a new method for quantitative analysis of lung ultrasonography was compared with bedside chest X-ray and visual lung ultrasonography for detection of community-acquired pneumonia, using thoracic computed tomography as a gold standard. Methods. Thirty-two spontaneously breathing patients with suspected community-acquired pneumonia, undergoing computed tomography examination, were consecutively enrolled. Each hemithorax was evaluated for the presence or absence of abnormalities by chest X-ray and quantitative or visual ultrasonography. Results. Quantitative ultrasonography showed higher sensitivity (93%), specificity (95%), and diagnostic accuracy (94%) than chest X-ray (64%, 80%, and 69%, resp.), visual ultrasonography (68%, 95%, and 77%, resp.), or their combination (77%, 75%, and 77%, resp.). Conclusions. Quantitative lung ultrasonography was considerably more accurate than either chest X-ray or visual ultrasonography in the diagnosis of community-acquired pneumonia and it may represent a useful first-line approach for confirmation of clinical diagnosis in emergency settings.

WHO Needs High FIO2

World Health Organization and the United States Center for Disease Control have recently recommended the use of 0.8 FIO2 in all adult surgical patients undergoing general anaesthesia, to prevent surgical site infections. This recommendation has arisen several discussions: As a matter of fact, there are numerous studies with different results about the effect of FIO2 on surgical site infection. Moreover, the clinical effects of FIO2 are not limited to infection control. We asked some prominent authors about their comments regarding the recent recommendations.

Postoperative respiratory disorders.

Purpose of reviewPostoperative pulmonary complications (PPC) are a prominent determinant of postoperative morbidity, mortality, and increased use of healthcare resources. Several scores have been developed to identify patients at higher risk of PPC and have been proposed or validated as tools to predict postoperative respiratory disorders, stratify risk among patients requiring surgery, and to plan clinical studies. The aim of this review is to provide an update on the recent progresses in perioperative medicine concerning the risk assessment, prevention, and treatment of PPCs. Recent findingsEfforts are being made to develop a uniform definition of PPCs; several scores have been developed and some of them externally validated. Their use can help the clinician to identify patients at higher risk, develop tailored strategies to mitigate the risk, and to perform a thoughtful allocation of healthcare resources. Intraoperative protective ventilation, with low tidal volume, low plateau pressure, low driving pressure and positive end expiratory pressure set at low-moderate levels titrated to avoid an increase in driving pressure and to achieve an acceptable gas exchange, can reduce the incidence of PPCs. Noninvasive positive pressure ventilation has an important role in the treatment of early stages of postoperative respiratory impairment, whereas not enough evidence is available concerning the use of routine prophylactic noninvasive continuous positive airway pressure postoperatively. SummarySeveral strategies can improve patients’ outcome, including risk assessment, intraoperative protective ventilation and postoperative noninvasive ventilation.

Postoperative complications of patients undergoing cardiac surgery.

Purpose of reviewCardiac surgery is at high risk for the development of postoperative complications involving cardiovascular and respiratory system, as well as kidneys and central nervous system. The aim of this review is to provide an overview on the most recent findings concerning the type and incidence of different complications after cardiac surgery and to summarize the current recommendations. Recent findingsDespite an improvement of surgical and anaesthesia techniques that resulted in a significant decrease in mortality, postoperative complications play a major role in affecting morbidity, mortality, length of hospital stay and patients’ quality of life. The most recent evidence suggests that fluid and inotropes administration should be targeted to maintain a cardiac index above 3 l/min/m2 throughout the perioperative period. Volatile anaesthesia and mechanical ventilation with low tidal volumes, low driving pressure and moderate-low positive end-expiratory pressure should be preferred. Preoperative steroids could reduce postoperative atrial fibrillation, whereas no drug has shown to effectively prevent kidney injury. SummaryCardiac surgery is still at high risk for postoperative complications. The optimal type of anaesthesia, protective mechanical ventilation during and after surgery as well as haemodynamic management with vasoactive and inotropic drugs is still to be determined.

CPAP Devices for Emergency Prehospital Use: A Bench Study

BACKGROUND: CPAP is frequently used in prehospital and emergency settings. An air-flow output minimum of 60 L/min and a constant positive pressure are 2 important features for a successful CPAP device. Unlike hospital CPAP devices, which require electricity, CPAP devices for ambulance use need only an oxygen source to function. The aim of the study was to evaluate and compare on a bench model the performance of 3 orofacial mask devices (Ventumask, EasyVent, and Boussignac CPAP system) and 2 helmets (Ventukit and EVE Coulisse) used to apply CPAP in the prehospital setting. METHODS: A static test evaluated air-flow output, positive pressure applied, and FIO2 delivered by each device. A dynamic test assessed airway pressure stability during simulated ventilation. Efficiency of devices was compared based on oxygen flow needed to generate a minimum air flow of 60 L/min at each CPAP setting. RESULTS: The EasyVent and EVE Coulisse devices delivered significantly higher mean air-flow outputs compared with the Ventumask and Ventukit under all CPAP conditions tested. The Boussignac CPAP system never reached an air-flow output of 60 L/min. The EasyVent had significantly lower pressure excursion than the Ventumask at all CPAP levels, and the EVE Coulisse had lower pressure excursion than the Ventukit at 5, 15, and 20 cm H2O, whereas at 10 cm H2O, no significant difference was observed between the 2 devices. Estimated oxygen consumption was lower for the EasyVent and EVE Coulisse compared with the Ventumask and Ventukit. CONCLUSIONS: Air-flow output, pressure applied, FIO2 delivered, device oxygen consumption, and ability to maintain air flow at 60 L/min differed significantly among the CPAP devices tested. Only the EasyVent and EVE Coulisse achieved the required minimum level of air-flow output needed to ensure an effective therapy under all CPAP conditions.

Effects of Nebulizer Position, Gas Flow, and CPAP on Aerosol Bronchodilator Delivery: An In Vitro Study

BACKGROUND: The aim of this study was to investigate the effects of different delivery circuit configurations, nebulizer positions, CPAP levels, and gas flow on the amount of aerosol bronchodilator delivered during simulated spontaneous breathing in an in vitro model. METHODS: A pneumatic lung simulator was connected to 5 different circuits for aerosol delivery, 2 delivering CPAP through a high-flow generator tested at 30, 60, and 90 L/min supplementary flow and 5, 10, and 15 cm H2O CPAP and 3 with no CPAP: a T-piece configuration with one extremity closed with a cap, a T-piece configuration without cap and nebulizer positioned proximally, and a T-piece configuration without cap and nebulizer positioned distally. Albuterol was collected with a filter, and the percentage amount delivered was measured by infrared spectrophotometry. RESULTS: Configurations with continuous high-flow CPAP delivered higher percentage amounts of albuterol compared with the configurations without CPAP (9.1 ± 6.0% vs 6.2 ± 2.8%, P = .03). Among configurations without CPAP, the best performance was obtained with a T-piece with one extremity closed with a cap. In CPAP configurations, the highest delivery (13.8 ± 4.4%) was obtained with the nebulizer placed proximal to the lung simulator, independent of flow. CPAP at 15 cm H2O resulted in the highest albuterol delivery (P = .02). CONCLUSIONS: Based on our in vitro study, without CPAP, a T-piece with a cap at one extremity maximizes albuterol delivery. During high-flow CPAP, the nebulizer should always be placed proximal to the patient, after the T-piece, using the highest CPAP clinically indicated.

Intraoperative mechanical ventilation in patients with non-injured lungs: time to talk about tailored protective ventilation?

It is a well-established concept that general anaesthesia can impair lung function postoperatively, even in subjects with healthy lungs (1), and mechanical ventilation itself is considered to play a major role in contributing to such dysfunction. Mortality after surgery was found to be higher than expected (2), with postoperative pulmonary complications (PPCs) having a relevant impact on outcome (3,4). Following these epidemiological findings, several research groups aimed at identifying modifiable risk factors associated with PPCs, in order to plan mitigation strategies to reduce the incidence of such complications and improve patients’ outcome. Among the others, several specific ventilation strategies have been found to be associated with a lower risk of developing PPCs. However, due to the low number of observed events, it is difficult to achieve a definitive answer on optimal intraoperative ventilation strategy to minimize the postoperative incidence of adverse events (5). In fact, general anaesthesia is nowadays considered as a safe procedure with a relatively low incidence of complications (6). The general tendency of the last decade was to translate the concept of “protective mechanical ventilation” borrowed by the critical care setting to non-injured lungs in operating room or intensive care and found to influence clinical outcome (7-9).