Modes Of Assisted Ventilation Research Articles

Post-insufflation diaphragm contractions in patients receiving various modes of mechanical ventilation

BackgroundDuring mechanical ventilation, post-insufflation diaphragm contractions (PIDCs) are non-physiologic and could be injurious. PIDCs could be frequent during reverse-triggering, where diaphragm contractions follow the ventilator rhythm. Whether PIDCs happens with different modes of assisted ventilation is unknown. In mechanically ventilated patients with hypoxemic respiratory failure, we aimed to examine whether PIDCs are associated with ventilator settings, patients’ characteristics or both.MethodsOne-hour recordings of diaphragm electromyography (EAdi), airway pressure and flow were collected once per day for up to five days from intubation until full recovery of diaphragm activity or death. Each breath was classified as mandatory (without-reverse-triggering), reverse-triggering, or patient triggered. Reverse triggering was further subclassified according to EAdi timing relative to ventilator cycle or reverse triggering leading to breath-stacking. EAdi timing (onset, offset), peak and neural inspiratory time (Tineuro) were measured breath-by-breath and compared to the ventilator expiratory time. A multivariable logistic regression model was used to investigate factors independently associated with PIDCs, including EAdi timing, amplitude, Tineuro, ventilator settings and APACHE II.ResultsForty-seven patients (median[25%-75%IQR] age: 63[52–77] years, BMI: 24.9[22.9–33.7] kg/m2, 49% male, APACHE II: 21[19–28]) contributed 2 ± 1 recordings each, totaling 183,962 breaths. PIDCs occurred in 74% of reverse-triggering, 27% of pressure support breaths, 21% of assist-control breaths, 5% of Neurally Adjusted Ventilatory Assist (NAVA) breaths. PIDCs were associated with higher EAdi peak (odds ratio [OR][95%CI] 1.01[1.01;1.01], longer Tineuro (OR 37.59[34.50;40.98]), shorter ventilator inspiratory time (OR 0.27[0.24;0.30]), high peak inspiratory flow (OR 0.22[0.20;0.26]), and small tidal volumes (OR 0.31[0.25;0.37]) (all P ≤ 0.008). NAVA was associated with absence of PIDCs (OR 0.03[0.02;0.03]; P < 0.001). Reverse triggering was characterized by lower EAdi peak than breaths triggered under pressure support and associated with small tidal volume and shorter set inspiratory time than breaths triggered under assist-control (all P < 0.05). Reverse triggering leading to breath stacking was characterized by higher peak EAdi and longer Tineuro and associated with small tidal volumes compared to all other reverse-triggering phenotypes (all P < 0.05).ConclusionsIn critically ill mechanically ventilated patients, PIDCs and reverse triggering phenotypes were associated with potentially modifiable factors, including ventilator settings. Proportional modes like NAVA represent a solution abolishing PIDCs.

Use of pressure muscle index to guide pressure support ventilation setting: a study protocol and statistical plan for a prospective randomised controlled proof-of-concept trial

IntroductionAlthough pressure support ventilation is one of the most commonly used assisted ventilation modes in intensive care units, there is still a lack of precise strategies for setting pressure support....

Research advances on neurally adjusted ventilatory assist

Mechanical ventilation has, since its introduction into clinical practice, undergone a major evolution from controlled ventilation to diverse modes of assisted ventilation. Conventional mechanical ventilators depend on flow sensors and pneumatic pressure and controllers to complete the respiratory cycle. Neurally adjusted ventilatory assist (NAVA) is a new form of assisted ventilation in recent years, which monitors the electrical activity of the diaphragm (EAdi) to provide an appropriately level of pressure support. And EAdi is the best available signal to sense central respiratory drive and trigger ventilatory assist. Unlike other ventilation modes, NAVA breathing instructions come from the center. Therefore, NAVA have the synchronous nature of the breaths and the patient-adjusted nature of the support. Compared with traditional ventilation mode, NAVA can efficiently unload respiratory muscles, relieve the risk of ventilator-induced lung injury (VILI), improve patient-ventilator coordination, enhance gas exchange, increase the success rate of weaning, etc. This article reviews the research progress of NAVA in order to provide theoretical guidance for clinical applications.

Analysis of the treatment of a premature infant with critical coronavirus disease caused by the Omicron variant of SARS-CoV-2

The patient is a female infant who was born at a gestational age of 30+4 weeks in the breech position and was delivered by assisted vaginal delivery. She was admitted to the neonatal department of Tianjin First Central Hospital for 44 days, during which she had stable respiration, oxygen saturation, and regular weight gain. The patient was discharged home by her family. The infant was readmitted to the hospital due to poor appetite for 15 hours and irregular breathing with weak response for 4 hours at the corrected gestational age of 37+2 weeks at 47 days after birth. The day before admission, the patient's mother experienced throat discomfort, and on the day of admission, the mother had a fever, with the highest temperature of 37.9 centigrade (she later tested positive for SARS-CoV-2 antigen). About 15 hours before admission, the family noticed that the patient had poor milk intake and weakened suction. About 4 hours before admission, the patient developed irregular breathing and weakened responses. After admission, the patient presented frequent apnea, and it was not relieved by adjusting the respiratory mode and parameters of non-invasive assisted ventilation, as well as caffeine citrate to stimulate the respiratory center. The patient was eventually given mechanical ventilation and other symptomatic support treatments. The pharyngeal swab was positive for COVID nucleic acid testing with a Ct value of 20.1 for the N gene. And the chest X-ray showed multiple patchy shadows in both lungs. The patient was diagnosed with critical coronavirus disease (COVID) caused by the Omicron variant in premature infants. After treatment, the child was clinically cured and discharged 8 days after hospitalization. Symptoms of COVID in premature infants may be atypical, and the condition can deteriorate rapidly. During the Omicron variant epidemic, we should pay more attention to premature infants so as to detect severe and critical cases as early as possible, and treat them actively to improve the prognosis.

Clinical effects of adaptive lung ventilation regime during weaning of mixed ICU patients

Background. Weaning from mechanical ventilation (MV) became one of the main problems of intensive care unit (ICU) physicians. Choosing the optimal mode of MV, which make possible to accelerate the process of weaning the patient, remain unresolved. A promising direction is the use of new adaptive ventilation modes.Objective. To compare the clinical efficacy of the iSV regimen with the traditional CPAP + PS (PSV) regimen in patients of a mixed ICU.Design and methods. 45 patients (age 31–81) were examined. Patients were on prolonged MV from 5 to 28 days. In group 1 pressure support (PSV) mode was used to adapt to spontaneous breathing. Group 2 consisted of patients in whom adaptive ventilation (iSV) mode was used.Results. Both modes of assisted ventilation provided effective respiratory support. In the PSV mode, on the 3rd and 5th days of weaning from MV, hypocapnia and a higher support by the pressure of spontaneous inspirations (PS) were noted. A higher daily energy requirement was revealed in PSV mode on day 3. The length of stay in ICU in iSV group was moderately decreased.Conclusion. Assisted ventilation modes PSV and iSV are effective in adapting patients to spontaneous breathing after prolonged MV. The iSV mode appears to cause less respiratory stress compared to the PSV mode. Assisted ventilation in iSV versus PSV can possibly reduce ICU length of stay.

Patient-Ventilator Synchrony in Neurally-Adjusted Ventilatory Assist and Variable Pressure Support Ventilation.

Neurally-adjusted ventilatory assist (NAVA) improves patient-ventilator synchrony and reduces the risk of respiratory over-assistance. Variable pressure support ventilation (PSV) is a recently introduced mode of assisted ventilation that has also shown reduction in patient-ventilator asynchronies. We hypothesized that NAVA would reduce patient-ventilator asynchronies and inspiratory effort compared to variable PSV because breathing variability was intrinsically determined by the patient and not by the ventilator. This study aimed to evaluate patient-ventilator asynchronies and inspiratory effort pressure-time product (PTP) between NAVA and variable PSV in subjects with mild ARDS. After 24 h of controlled mechanical ventilation, subjects (PaO2 /FIO2 200-300 and PEEP level < 10 cm H2O) were randomized in sequence 1:1 by using a web-based encrypted platform and assigned to NAVA or variable PSV groups. Both modes of ventilation were consecutively kept for 24 h unless there were clinical changes. The primary aim of this study was to evaluate differences in asynchrony index (AI) between variable PSV and NAVA. Our secondary aims were to evaluate the coefficient of variation (CV) of breathing patterns and inspiratory effort between the groups. Thirteen subjects were randomized in the NAVA group and 13 subjects in the variable PSV group. AI over time and minute PTP (PTPmin) were not different between NAVA and variable PSV groups (AI t0P = .52, AI t12P = .27, AI t24P = .12; and PTPmin-t0P = .60, PTPmin-t12P = .57, PTPmin-t24P = .85, respectively). CV for tidal volume (VT) and pressure support (PS) was lower in variable PSV group over time compared with NAVA group (P < .05). In this randomized controlled trial including subjects with mild ARDS, NAVA and variable PSV had comparable effects on patient-ventilator synchronies and PTP. However, variable PSV reduced the variability of VT and PS when compared with NAVA.

Novel ventilation techniques in children.

Extraordinary progress has been made during the past few decades in the development of anesthesia machines and ventilation techniques. With unprecedented precision and performance, modern machines for pediatric anesthesia can deliver appropriate mechanical ventilation for children and infants of all sizes and with ongoing respiratory diseases, ensuring very small volume delivery and compensating for circuit compliance. Along with highly accurate monitoring of the delivered ventilation, modern ventilators for pediatric anesthesia also have a broad choice of ventilation modalities, including synchronized and assisted ventilation modes, which were initially conceived for ventilation weaning in the intensive care setting. Despite these technical advances, there is still room for improvement in pediatric mechanical ventilation. There is a growing effort to minimize the harm of intraoperative mechanical ventilation of children by adopting the protective ventilation strategies that were previously employed only for prolonged mechanical ventilation. More than ever, the pediatric anesthesiologist should now recognize that positive‐pressure ventilation is potentially a harmful procedure, even in healthy children, as it can contribute to both ventilator‐induced lung injury and ventilator‐induced diaphragmatic dysfunction. Therefore, careful choice of the ventilation modality and its parameters is of paramount importance to optimize gas exchange and to protect the lungs from injury during general anesthesia. The present report reviews the novel ventilation techniques used for children, discussing the advantages and pitfalls of the ventilation modalities available in modern anesthesia machines, as well as innovative ventilation modes currently under development or research. Several innovative strategies and devices are discussed. These novel modalities are likely to become part of the armamentarium of the pediatric anesthesiologist in the near future and are particularly relevant for challenging ventilation scenarios.

Effects of Different Levels of Variability and Pressure Support Ventilation on Lung Function in Patients With Mild–Moderate Acute Respiratory Distress Syndrome

Background: Variable pressure support ventilation (vPSV) is an assisted ventilation mode that varies the level of pressure support on a breath-by-breath basis to restore the physiological variability of breathing activity. We aimed to compare the effects of vPSV at different levels of variability and pressure support (ΔPS) in patients with acute respiratory distress syndrome (ARDS).Methods: This study was a crossover randomized clinical trial. We included patients with mild to moderate ARDS already ventilated in conventional pressure support ventilation (PSV). The study consisted of two blocks of interventions, and variability during vPSV was set as the coefficient of variation of the ΔPS level. In the first block, the effects of three levels of variability were tested at constant ΔPS: 0% (PSV0%, conventional PSV), 15% (vPSV15%), and 30% (vPSV30%). In the second block, two levels of variability (0% and variability set to achieve ±5 cmH2O variability) were tested at two ΔPS levels (baseline ΔPS and ΔPS reduced by 5 cmH2O from baseline). The following four ventilation strategies were tested in the second block: PSV with baseline ΔPS and 0% variability (PSVBL) or ±5 cmH2O variability (vPSVBL), PSV with ΔPS reduced by 5 cmH2O and 0% variability (PSV−5) or ±5 cmH2O variability (vPSV−5). Outcomes included gas exchange, respiratory mechanics, and patient-ventilator asynchronies.Results: The study enrolled 20 patients. In the first block of interventions, oxygenation and respiratory mechanics parameters did not differ between vPSV15% and vPSV30% compared with PSV0%. The variability of tidal volume (VT) was higher with vPSV15% and vPSV30% compared with PSV0%. The incidence of asynchronies and the variability of transpulmonary pressure (PL) were higher with vPSV30% compared with PSV0%. In the second block of interventions, different levels of pressure support with and without variability did not change oxygenation. The variability of VT and PL was higher with vPSV−5 compared with PSV−5, but not with vPSVBL compared with PSVBL.Conclusion: In patients with mild-moderate ARDS, the addition of variability did not improve oxygenation at different pressure support levels. Moreover, high variability levels were associated with worse patient-ventilator synchrony.Clinical Trial Registration: www.clinicaltrials.gov, identifier: NCT01683669.

Proportional assist and neurally adjusted ventilation: Clinical knowledge and future trials in newborn infants.

Different types of patient triggered ventilator modes have become the mainstay of ventilation in term and preterm newborn infants. Maintaining spontaneous breathing has allowed for earlier weaning and the additive effects of respiratory efforts combined with pre-set mechanical inflations have reduced mean airway pressures, both of which are important components in trying to avoid lung injury and promote normal lung development. New sophisticated modes of assisted ventilation have been developed during the last decades where the control of ventilator support is turned over to the patient. The ventilator detects the respiratory effort and adjusts ventilatory assistance proportionally to each phase of the respiratory cycle, thus enabling the patient to have full control of the start, the duration and the amount of ventilatory assistance. In this paper we will review the literature on the ventilatory modes of proportional assist ventilation and neurally adjusted ventilatory assistance, examine the different ways the signals are analyzed, propose future studies, and suggest ways to apply these modes in the clinical environment.

EL PERSONAL DE ENFERMERÍA EN LA APLICACIÓN DEL PROTOCOLO DE VENTILACIÓN MECÁNICA

La ventilación mecánica es un tratamiento de soporte vital, en el que se utiliza una máquina que suministra un soporte ventilatorio y oxigenatorio, facilitando el intercambio gaseoso y el trabajo respiratorio de los pacientes con insuficiencia respiratoria. Un protocolo es un documento que se desarrolla para orientar la toma de decisiones entorno a problemas específicos, ya sea como diagnosticar, tratar y cuidar a alguien con una afección específica. En este documento se describe si el personal de Enfermería aplica el Protocolo de Ventilación Mecánica propio de la unidad o del Ministerio de Salud Pública en la Unidad de Cuidados Intensivos. ). Por tal motivo resulta importante resaltar el papel que el personal de enfermería desempeña en las áreas de cuidados intensivos brindando la atención especializada e individualizada que requiere el paciente aportando a su progresiva recuperación El tipo de investigación realizada es de carácter observacional, de campo y prospectivo, Participaron en el estudio un total de 11 profesionales de enfermería del área de la Unidad de Cuidados Intensivos del Hospital Napoleón Dávila Córdova de Chone. De acuerdo con las encuestas realizadas el 100% del personal refiere que aplican el protocolo de Ventilación Mecánica del MSP, utilizando con mayor frecuencia el modo de ventilación mecánica asistida. Previo al procedimiento de ventilación mecánica el personal de enfermería aplica las debidas normas de bioseguridad. La implementación del protocolo del de VM invasiva y no invasiva al momento de realizar el procedimiento es esencial porque de esta manera se va a trabajar con una guía específica la cual evitará posibles complicaciones en la UCI.

Proportional assist ventilation versus pressure support ventilation for weaning from mechanical ventilation in adults: a meta-analysis and trial sequential analysis

BackgroundPressure support ventilation (PSV) is the prevalent weaning method. Proportional assist ventilation (PAV) is an assisted ventilation mode, which is recently being applied to wean the patients from mechanical ventilation. Whether PAV or PSV is superior for weaning remains unclear.MethodsEligible randomized controlled trials published before April 2020 were retrieved from databases. We calculated the risk ratio (RR) and mean difference (MD) with 95% confidence intervals (CIs).ResultsSeven articles, involving 634 patients, met the selection criteria. Compared to PSV, PAV was associated with a significantly higher rate of weaning success (fixed-effect RR 1.16; 95% CI 1.07–1.26; I2 = 0.0%; trial sequential analysis-adjusted CI 1.03–1.30), and the trial sequential monitoring boundary for benefit was crossed. Compared to PSV, PAV was associated with a lower proportion of patients requiring reintubation (RR 0.49; 95% CI 0.28–0.87; I2 = 0%), a shorter ICU length of stay (MD − 1.58 (days), 95% CI − 2.68 to − 0.47; I2 = 0%), and a shorter mechanical ventilation duration (MD − 40.26 (hours); 95% CI − 66.67 to − 13.84; I2 = 0%). There was no significant difference between PAV and PSV with regard to mortality (RR 0.66; 95% CI 0.42–1.06; I2 = 0%) or weaning duration (MD − 0.01 (hours); 95% CI − 1.30–1.28; I2 = 0%).ConclusionThe results of the meta-analysis suggest that PAV is superior to PSV in terms of weaning success, and the statistical power is confirmed using trial sequential analysis.Graphical abstract

"Current concepts of mechanical ventilation in neonates" - Part 1: Basics.

Mechanical ventilation is potentially live saving in neonatal patients with respiratory failure. The main purpose of mechanical ventilation is to ensure adequate gas exchange, including delivery of adequate oxygenation and enough ventilation for excretion of CO2. The possibility to measure and deliver small flows and tidal volumes have allowed to develop very sophisticated modes of assisted mechanical ventilation for the most immature neonates, such as volume targeted ventilation, which is used more and more by many clinicians. Use of mechanical ventilation requires a basic understanding of respiratory physiology and pathophysiology of the disease leading to respiratory failure. Understanding pulmonary mechanics, elastic and resistive forces (compliance and resistance), and its influence on the inspiratory and expiratory time constant, and the mechanisms of gas exchange are necessary to choose the best mode of ventilation and adequate ventilator settings to minimize lung injury. Considering the pathophysiology of the disease allows a physiology-based approach and application of these concepts in daily practice for decision making regarding the use of modes and settings of mechanical ventilation, with the ultimate aim of providing adequate gas exchange and minimising lung injury.

Monitoring respiratory mechanics during assisted ventilation.

Accurate monitoring of the mechanical properties of the respiratory system is crucial to understand the pathophysiological mechanisms of respiratory failure in mechanically ventilated patients, to optimize mechanical ventilation settings and to reduce ventilator-induced lung injury. However, although the assessment of respiratory mechanics is simple in patients undergoing fully controlled ventilation, it becomes quite challenging in the presence of spontaneous breathing activity. Aim of the present review is to describe how the different components of respiratory mechanics [resistance, static compliance, and intrinsic positive end-expiratory pressure (PEEP)] can be measured at the bedside during assisted modes of ventilation. Available techniques for bedside measurement of resistance during assisted ventilation are complex and not commonly implemented. On the contrary, an increasing number of reports indicate that measurement of static compliance and intrinsic PEEP can be easily obtained, both with advanced monitoring systems (esophageal and gastric manometry, diaphragm electromyography, electrical impedance tomography) and, with some limitations, with simple airways occlusion maneuvers. Assessment of respiratory mechanics in spontaneously breathing patients, with some limitations, is feasible and should be included in everyday clinical practice; however, more data are needed to understand the clinical relevance of the measures obtained during assisted ventilation.

Comparison of ventilatory modes to facilitate liberation from mechanical ventilation: protocol for a systematic review and network meta-analysis

IntroductionTimely liberation from invasive mechanical ventilation is important to reduce the risk of ventilator-associated complications. Once a patient is deemed ready to tolerate a mode of partial ventilator assist, clinicians...

Evaluation of indirect measures of neural inspiratory time from invasive and noninvasive recordings of respiratory activity.

Measuring diaphragmatic electromyography (EMGdi) provides an indirect quantification of neural respiratory drive and allows the delimitation of diaphragm neural activation and deactivation during inspiration. EMGdi recordings have been incorporated in novel modes of assisted mechanical ventilation, such as neurally adjusted ventilatory assist (NAVA), to trigger and cycle-off the ventilator. The EMGdi signal improves the assistance delivered by more conventional ventilatory modes, in which the ventilator is synchronized with the patient employing a pneumatic triggering. In this work, we evaluate the time delay between the onset and offset of inspiratory activity estimated from EMGdi and three respiratory mechanical signals: the respiratory flow (FL), the transdiaphragmatic pressure (Pdi) and the diaphragm length (Ldi) signals. To this purpose, these signals were acquired in three mongrel dogs surgically instrumented under general anesthesia. Onsets and offsets were estimated manually and by automatic algorithms on these signals. The highest delays were obtained between EMGdi and FL (100 ms) while the lowest delays were obtained between EMGdi and Pdi (8 ms). Moreover, differences between manual and automatic estimations showed a mean absolute error lower than 45 ms. In conclusion, our study points out that both EMGdi and Pdi signals detect the onset and offset of inspiratory activity earlier than the FL signal, and would therefore be better for the improvement of patient-ventilator synchrony.

Independent risk factors for sepsis in patients with large area burns

Objective To determine the independent risk factors for sepsis in patients with large area burns. Methods The study enrolled 307 patients with large area burns treated from June 2014 to June 2015. Related variables included age, gender, visit time, emergency eschar open, burn index, tangential excision of eschar during shock stage, delayed resuscitation during shock stage, oxygen pressure (PaO2), carbon dioxide pressure (PaCO2), assisted ventilation mode, mechanical ventilation time, inhalation injury, prophylactic tracheotomy, continuous lactic acid rise, refractory hypernatremia, heart-lung disease history, and diabetes history. Correlation of the variables with the incidence of sepsis was observed. Independent predictors of sepsis in patients with large burns were differentiated using the Logistic regression analysis. Results Delayed resuscitation during shock period (OR=1.747, 95% CI 1.822-7.431, P<0.05), continuous lactic acid rise (OR=1.758, 95%CI 1.137-4.002, P<0.05), refractory hypernatremia (OR=2.985, 95%CI 1.074-6.782, P<0.05), moderate and severe inhalation injury(OR=14.764, 95%CI 0.892-47.323, P<0.05) and burn index (OR=5.017, 95%CI 1.075-23.572, P<0.05) were found be independently associated with sepsis in patients with large burns. Conclusions These independent risk factors for sepsis in large area burn patients deserve more attention. Early and timely treatment measures may reduce the incidence of sepsis. Key words: Burns; Sepsis; Risk factors

Assisted Ventilation

Controlled Mechanical Ventilation may be essential in the setting of severe respiratory failure but consequences to the patient including increased use of sedation and neuromuscular blockade may contribute to delirium, atelectasis, and diaphragm dysfunction. Assisted ventilation allows spontaneous breathing activity to restore physiological displacement of the diaphragm and recruit better perfused lung regions. Pressure Support Ventilation is the most frequently used mode of assisted mechanical ventilation. However, this mode continues to provide a monotonous pattern of support for respiration which is normally a dynamic process. Noisy Pressure Support Ventilation where tidal volume is varied randomly by the ventilator may improve ventilation and perfusion matching but the degree of support is still determined by the ventilator. Two more recent modes of ventilation, Proportional Assist Ventilation and Neurally Adjusted Ventilatory Assist (NAVA), allow patient determination of the pattern and depth of ventilation. Proposed advantages of Proportional Assist Ventilation and NAVA include decrease in patient ventilator asynchrony and improved adaptation of ventilator support to changing patient demand. Work of breathing can be normalized with these modes as well. To date, however, a clear pattern of clinical benefit has not been demonstrated. Existing challenges for both of the newer assist modes include monitoring patients with dynamic hyperinflation (auto-positive end expiratory pressure), obstructive lung disease, and air leaks in the ventilator system. NAVA is dependent on consistent transduction of diaphragm activity by an electrode system placed in the esophagus. Longevity of effective support with this technique is unclear.

Comparing two different modes of mechanical ventilation by the least square fitting method: nava versus PSV

The Least Square Fitting (LSF) method is a statistical approach used for evaluating respiratory mechanics [1]. It allows measurement of respiratory mechanics continuously at the bedside, even in presence of flow limitation [23], without the need for constant inspiratory flow rate, end-inspiratory hold and end-expiratory occlusion. These features allow the application of the LSF method to assisted ventilation modes, such as pressure support ventilation (PSV) [3] and neurally-adjusted ventilatory assist (NAVA).

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 patient's 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.

Assisted mechanical ventilation: the future is now!

Assisted ventilation is a highly complex process that requires an intimate interaction between the ventilator and the patient. The complexity of this form of ventilation is frequently underappreciated by the bedside clinician. In assisted mechanical ventilation, regardless of the specific mode, the ventilator’s gas delivery pattern and the patient’s breathing pattern must match near perfectly or asynchrony between the patient and the ventilator occurs. Asynchrony can be categorized into four general types: flow asynchrony; trigger asynchrony; cycle asynchrony; and mode asynchrony. In an article recently published in BMC Anesthesiology, Hodane et al. have demonstrated reduced asynchrony during assisted ventilation with Neurally Adjusted Ventilatory Assist (NAVA) as compared to pressure support ventilation (PSV). These findings add to the growing volume of data indicating that modes of ventilation that provide proportional assistance to ventilation – e.g., NAVA and Proportional Assist Ventilation (PAV) – markedly reduce asynchrony. As it becomes more accepted that the respiratory center of the patient in most circumstances is the most appropriate determinant of ventilatory pattern and as the negative outcome effects of patient-ventilator asynchrony become ever more recognized, we can expect NAVA and PAV to become the preferred modes of assisted ventilation!