Ongoing Mechanical Ventilation Research Articles

In-line Mechanical Insufflation-Exsufflation as an Alternative to Invasive Suction for Secretion Management in Ventilated Patients, A Randomized Controlled Trial

Background Catheter suction (CS), the standard method for airway secretion management in tracheostomized or intubated patients, is invasive and has significant hemodynamic and traumatic side effects. In-line mechanical insufflation-exsufflation (IL-MIE) is a new, non-invasive technology that clears secretions by simulating coughs without interrupting ongoing mechanical ventilation. It is not known whether IL-MIE can be safely and effectively used as an alternative to CS in these ventilated patients. Methods A randomized controlled study was conducted comparing a standard protocol of CS with automatic IL-MIE (CoughSync, Ruxin Medical Systems, Beijing) performed every 30 minutes, with CS added only if needed, in post-operative mechanically ventilated patients. Results Over 8 hours, the IL-MIE cohort required significantly fewer CS treatments per patient than the control cohort (mean 0.4 vs. 2.6, p < 0.001, n = 60 for both cohorts). Seventy-three percent of the IL-MIE subjects required no CS at all, compared to 2% in the control group (p < 0.001). At 8 hours, IL-MIE subjects had a significantly lower heart rate than control subjects (mean 90 vs. 96, p = 0.047), implying a hemodynamic advantage to IL-MIE. No significant adverse events were associated with IL-MIE. Conclusions IL-MIE minimizes the need for invasive CS without detriment to ventilatory management in mechanically ventilated patients.

Effects of hyperbaric oxygen combined cabin ventilator on critically ill patients with liberation difficulty after tracheostomy

BackgroundCritically ill patients undergoing liberation often encounter various physiological and clinical complexities and challenges. However, whether the combination of hyperbaric oxygen and in-cabin ventilator therapy could offer a comprehensive approach that may simultaneously address respiratory and potentially improve outcomes in this challenging patient population remain unclear.MethodsThis retrospective study involved 148 patients experiencing difficulty in liberation after tracheotomy. Inclusion criteria comprised ongoing mechanical ventilation need, lung inflammation on computed tomography (CT) scans, and Glasgow Coma Scale (GCS) scores of ≤ 9. Exclusion criteria excluded patients with active bleeding, untreated pneumothorax, cerebrospinal fluid leakage, and a heart rate below 50 beats per minute. Following exclusions, 111 cases were treated with hyperbaric oxygen combined cabin ventilator, of which 72 cases were successfully liberated (SL group) and 28 cases (NSL group) were not successfully liberated. The hyperbaric oxygen chamber group received pressurization to 0.20 MPa (2.0 ATA) for 20 min, followed by 60 min of ventilator oxygen inhalation. Successful liberation was determined by a strict process, including subjective and objective criteria, with a prolonged spontaneous breathing trial. GCS assessments were conducted to evaluate consciousness levels, with scores categorized as normal, mildly impaired, moderately impaired, or severely impaired.ResultsPatients who underwent treatment exhibited improved GCS, blood gas indicators, and cardiac function indexes. The improvement of GCS, partial pressure of oxygen (PaO2), oxygen saturation of blood (SaO2), oxygenation index (OI) in the SL group was significantly higher than that of the NSL group. However, there was no significant difference in the improvement of left ventricular ejection fraction (LVEF), left ventricular end-systolic volume (LVESV), left ventricular end-diastolic volume (LVEDV), and stroke volume (SV) between the SL group and the NSL group after treatment.ConclusionsHyperbaric oxygen combined with in-cabin ventilator therapy effectively enhances respiratory function, cardiopulmonary function, and various indicators of critically ill patients with liberation difficulty after tracheostomy.

The PROMIZING trial enrollment algorithm for early identification of patients ready for unassisted breathing

BackgroundLiberating patients from mechanical ventilation (MV) requires a systematic approach. In the context of a clinical trial, we developed a simple algorithm to identify patients who tolerate assisted ventilation but still require ongoing MV to be randomized. We report on the use of this algorithm to screen potential trial participants for enrollment and subsequent randomization in the Proportional Assist Ventilation for Minimizing the Duration of MV (PROMIZING) study.MethodsThe algorithm included five steps: enrollment criteria, pressure support ventilation (PSV) tolerance trial, weaning criteria, continuous positive airway pressure (CPAP) tolerance trial (0 cmH2O during 2 min) and spontaneous breathing trial (SBT): on fraction of inspired oxygen (FiO2) 40% for 30–120 min. Patients who failed the weaning criteria, CPAP Zero trial, or SBT were randomized. We describe the characteristics of patients who were initially enrolled, but passed all steps in the algorithm and consequently were not randomized.ResultsAmong the 374 enrolled patients, 93 (25%) patients passed all five steps. At time of enrollment, most patients were on PSV (87%) with a mean (± standard deviation) FiO2 of 34 (± 6) %, PSV of 8.7 (± 2.9) cmH2O, and positive end-expiratory pressure of 6.1 (± 1.6) cmH2O. Minute ventilation was 9.0 (± 3.1) L/min with a respiratory rate of 17.4 (± 4.4) breaths/min. Patients were liberated from MV with a median [interquartile range] delay between initial screening and extubation of 5 [1–49] hours. Only 7 (8%) patients required reintubation.ConclusionThe trial algorithm permitted identification of 93 (25%) patients who were ready to extubate, while their clinicians predicted a duration of ventilation higher than 24 h.

Analgesia and Sedation in Critically Ill Patients With Burns.

Analgesia and Sedation in Critically Ill Patients With Burns.

Effects of mechanical ventilation versus apnea on bi-ventricular pressure-volume loop recording.

Respiration changes intrathoracic pressure and lung volumes in a cyclic manner, which affect cardiac function. Invasive ventricular pressure-volume (PV) loops can be recorded during ongoing mechanical ventilation or in transient apnea. No consensus exists considering ventilatory mode during PV loop recording. The objective of this study was to investigate the magnitude of any systematic difference of bi-ventricular PV loop variables recorded during mechanical ventilation versus apnea. PV loops were recorded simultaneously from the right ventricle and left ventricle in a closed chest porcine model during mechanical ventilation and in transient apnea (n=72). Variables were compared by regression analyses. Mechanical ventilation versus apnea affected regression coefficients for important PV variables including right ventricular stroke volume (1.22, 95% CI [1.08-1.36], p=0.003), right ventricular ejection fraction (0.90, 95% CI [0.81-1.00], p=0.043) and right ventricular arterial elastance (0.61, 95%CI [0.55-0.68], p<0.0001). Right ventricular pressures and volumes were parallelly shifted with Y-intercepts different from 0. Few left ventricular variables were affected, mainly first derivatives of pressure (dP/dt(max): 0.96, 95% CI [0.92-0.99], p=0.016, and dP/dt(min): 0.92, 95% CI [0.86-0.99], p=0.026), which might be due to decreased heart rate in apnea (Y-intercept -6.88, 95% CI [-12.22; -1.54], p=0.012). We conclude, that right ventricular stroke volume, ejection fraction and arterial elastance were mostly affected by apnea compared to mechanical ventilation. The results motivate future standardization of respiratory modality when measuring PV relationships.

Systemic thrombolysis and anticoagulation improved biomarker measurements in massive-like pulmonary embolism and severe COVID-19 pneumonia: a case report.

BackgroundFrom asymptomatic patients to severe acute respiratory distress syndrome, COVID-19 has a wide range of clinical presentations, and venous thromboembolism has emerged as a critical and frequent complication.Case summaryWe present a case of a 69-year-old man with a clinical presentation of massive-like pulmonary embolism (PE) overlapping with severe COVID-19 pneumonia. The diagnosis was made based on hypotension, severe oxygen desaturation (33%), and right ventricular dysfunction (RVD). We used alteplase and low-molecular-weight heparin, obtaining immediate clinical improvement. Also, we identified an extremely elevated D-dimer (31.2 mcg/mL), and computed tomography pulmonary angiography (CTPA) revealed an unexpected low thrombus burden and a crazy-paving pattern. Considering this, we decided to discontinue the alteplase. Therefore, the mechanisms of pulmonary hypertension and RVD could be multifactorial. Despite the patient’s respiratory status worsening and ongoing mechanical ventilation, biomarkers kept lowering to normal ranges. It appears a favourable outcome was related to early PE diagnosis and a multimodal therapeutic approach.DiscussionPhysicians in the ER should be warned about extremely high D-dimer measurements and severe oxygen desaturation as possible markers of severe COVID-19 pneumonia in patients with high-clinical suspicion of PE. Although ESC guidelines recommend immediate reperfusion in cardiogenic shock secondary to PE, we suggest initial CTPA in patients with high-clinical suspicion of severe COVID-19.

Occurrence of ventilator associated pneumonia using a tracheostomy tube with subglottic secretion drainage.

Ventilator-associated pneumonia (VAP) is a significant cause of morbidity and mortality in critically ill patients who require mechanical ventilation (MV). Subglottic secretions above the endotracheal cuff are associated with bacteria colonization of lower respiratory tract, causing VAP. A preventive strategy to avoid subglottic secretion progression is the drainage with special tracheal tubes effective in preventing both early onset and late onset VAP. The purpose of this study was to measure VAP incidence in tracheostomized patients with suction above the cuff. The authors performed a matched cohort study with historical control in three academic Intensive Care Units (ICUs): upon ICU admission, patients requiring MV were submitted to tracheostomy with a tracheal tube allowing drainage of subglottic secretions (treatment group). A control group without suctioning above the cuff was selected applying the propensity score matching on dataset of previous ELT Study. VAP occurrence at 28-days from intubation was the primary endpoint; hospital mortality and ICU-free days at 28-days were the secondary endpoints. Between July 2014 and April 2016, 125 tracheostomized patients were included in the analysis. 232 tracheostomized patients without suctioning were selected as a control group for the matched cohort study. The application of propensity score matching selected 60 patients to compare the two groups. Incidence of VAP was 8% in treatment group and 19.4% in the control group (P value =0.004). After balance with propensity score matching VAP was 8.3% and 21.7% (P value =0.0408), respectively. Subglottic secretion drainage reduces incidence of VAP in critically ill patients requiring ongoing MV via tracheostomy.

Tracheostomy ventilation outside the intensive care unit: Experience of a tertiary care hospital

INTRODUCTION: Some patients remain dependent on invasive mechanical ventilation after critical illness. In most centers, these patients require Intensive Care Unit (ICU)-level care for ongoing tracheostomy-based mechanical ventilation. Our center has over 22 years of experience providing care for patients who require ventilation via tracheostomy on a medical ward. OBJECTIVE: The objective was to describe a patient cohort, including demographics, length of stay, complications and discharge disposition, who were ventilated via tracheostomy on medical wards. METHODS: A single center, retrospective study was conducted from 1993 to 2015. RESULTS: There were 144 admissions for 50 patients over the 22-year study period. Mean age at first admission was 55.6 years; 32 patients (64%) were male and 42 (84%) were admitted from home. Patients required ventilation for amyotrophic lateral sclerosis (ALS; 36%), spinal cord injury (16%), Guillain-Barre (12%) or another neuromuscular disorder (12%). Mean ICU length of stay on index admission was 46.6 days (range 2–219), and ward stay was an average of 264 days (range, 5–1402). Complications on index admission included 23 episodes of stoma infection, 48 episodes of pneumonia, and a total of 28 ICU transfers. Of the 50 patients, 19 (38%) were discharged home, 18 (36%) were transferred to long-term care and 12 patients (24%) died in hospital including 1 due to a critical incident involving prolonged disconnection from the ventilator. CONCLUSION: The complex care needs of patients requiring mechanical ventilation can safely be provided on medical wards. This opens ICU beds for other patients requiring critical care.

Prolonged Weaning - S2k-Guideline Published by the German Respiratory Society

Mechanical ventilation (MV) is an essential part of modern intensive care medicine. MV is performed in patients with severe respiratory failure caused by insufficiency of respiratory muscles and/or lung parenchymal disease when/after other treatments, (i. e. medication, oxygen, secretion management, continuous positive airway pressure or nasal highflow) have failed.MV is required to maintain gas exchange and to buy time for curative therapy of the underlying cause of respiratory failure. In the majority of patients weaning from MV is routine and causes no special problems. However, about 20 % of patients need ongoing MV despite resolution of the conditions which precipitated the need for MV. Approximately 40 - 50 % of time spent on MV is required to liberate the patient from the ventilator, a process called "weaning."There are numberous factors besides the acute respiratory failure that have an impact on duration and success rate of the weaning process such as age, comorbidities and conditions and complications acquired in the ICU. According to an international consensus conference "prolonged weaning" is defined as weaning process of patients who have failed at least three weaning attempts or require more than 7 days of weaning after the first spontaneous breathing trial (SBT). Prolonged weaning is a challenge, therefore, an inter- and multi-disciplinary approach is essential for a weaning success.In specialised weaning centers about 50 % of patients with initial weaning failure can be liberated from MV after prolonged weaning. However, heterogeneity of patients with prolonged weaning precludes direct comparisons of individual centers. Patients with persistant weaning failure either die during the weaning process or are discharged home or to a long term care facility with ongoing MV.Urged by the growing importance of prolonged weaning, this Sk2-guideline was first published in 2014 on the initiative of the German Respiratory Society (DGP) together with other scientific societies involved in prolonged weaning. Current research and study results, registry data and experience in daily practice made the revision of this guideline necessary.The following topics are dealt with in the guideline: Definitions, epidemiology, weaning categories, the underlying pathophysiology, prevention of prolonged weaning, treatment strategies in prolonged weaning, the weaning unit, discharge from hospital on MV and recommendations for end of life decisions.Special emphasis in the revision of the guideline was laid on the following topics:- A new classification of subgroups of patients in prolonged weaning- Important aspects of pneumological rehabilitation and neurorehabilitation in prolonged weaning- Infrastructure and process organization in the care of patients in prolonged weaning in the sense of a continuous treatment concept- Therapeutic goal change and communication with relativesAspects of pediatric weaning are given separately within the individual chapters.The main aim of the revised guideline is to summarize current evidence and also expert based- knowledge on the topic of "prolonged weaning" and, based on the evidence and the experience of experts, make recommendations with regard to "prolonged weaning" not only in the field of acute medicine but also for chronic critical care.Important addressees of this guideline are Intensivists, Pneumologists, Anesthesiologists, Internists, Cardiologists, Surgeons, Neurologists, Pediatricians, Geriatricians, Palliative care clinicians, Rehabilitation physicians, Nurses in intensive and chronic care, Physiotherapists, Respiratory therapists, Speech therapists, Medical service of health insurance and associated ventilator manufacturers.

Conversations About Goals and Values Are Feasible and Acceptable in Long-Term Acute Care Hospitals: A Pilot Study.

The chronically critically ill have survived acute critical illness but require prolonged mechanical ventilation. These patients are frequently transferred from acute care to long-term acute care hospitals (LTACHs) for prolonged recovery, yet many suffer setbacks requiring readmission to acute care. The patient's relatively improved condition while at the LTACH might be an opportunity for communication regarding care goals; however, there have been no prior studies of the feasibility of such conversations in the LTACH. To determine the feasibility, acceptability, and potential usefulness of conversations about serious illness with chronic critical illness patients or their surrogate decision makers after LTACH admission. We adapted an existing conversation guide for use in chronically critically ill (defined by tracheotomy for prolonged ventilation) LTACH patients or their surrogates to explore views about quality of life, understanding of medical conditions, expectations, and planning for setbacks. These conversations were conducted by one interviewer and summarized for the patients' clinicians. We surveyed patients, surrogates, and clinicians to assess acceptability. A total of 70 subjects were approached and 50 (71%) were enrolled, including 30 patients and 20 surrogates. The median duration of the conversation was 14 minutes 45 seconds [IQR 12:46, 19]. The presence of ongoing mechanical ventilation did not lead to longer conversations; in fact, conversations with patients were shorter than those with surrogates. The majority of subjects (81%) described the conversation as worthwhile. The majority of clinicians (73%) reported that the conversation offered a new and significant understanding of the patient's preferences if a setback were to occur. Conversations about serious illness care goals can be accomplished in a relatively short period of time, are acceptable to chronically critically ill patients and their surrogate decision makers in the LTACH, and are perceived as worthwhile by patients, surrogates, and clinicians.

Monitoring of total positive end-expiratory pressure during mechanical ventilation by artificial neural networks

Ventilation treatment of acute lung injury (ALI) requires the application of positive airway pressure at the end of expiration (PEEPapp) to avoid lung collapse. However, the total pressure exerted on the alveolar walls (PEEPtot) is the sum of PEEPapp and intrinsic PEEP (PEEPi), a hidden component. To measure PEEPtot, ventilation must be discontinued with an end-expiratory hold maneuver (EEHM). We hypothesized that artificial neural networks (ANN) could estimate the PEEPtot from flow and pressure tracings during ongoing mechanical ventilation. Ten pigs were mechanically ventilated, and the time constant of their respiratory system (τRS) was measured. We shortened their expiratory time (TE) according to multiples of τRS, obtaining different respiratory patterns (Rpat). Pressure (PAW) and flow (V'AW) at the airway opening during ongoing mechanical ventilation were simultaneously recorded, with and without the addition of external resistance. The last breath of each Rpat included an EEHM, which was used to compute the reference PEEPtot. The entire protocol was repeated after the induction of ALI with i.v. injection of oleic acid, and 382 tracings were obtained. The ANN had to extract the PEEPtot, from the tracings without an EEHM. ANN agreement with reference PEEPtot was assessed with the Bland-Altman method. Bland Altman analysis of estimation error by ANN showed -0.40±2.84 (expressed as bias±precision) and ±5.58 as limits of agreement (data expressed as cmH2O). The ANNs estimated the PEEPtot well at different levels of PEEPapp under dynamic conditions, opening up new possibilities in monitoring PEEPi in critically ill patients who require ventilator treatment.

Evaluation of a practice guideline for the management of respiratory distress syndrome in preterm infants: A quality improvement initiative

The use of mechanical ventilation to treat respiratory distress syndrome in preterm infants has been associated with the development of bronchopulmonary dysplasia. As part of a quality improvement initiative to reduce the incidence of bronchopulmonary dysplasia in preterm infants, a new practice guideline for the management of respiratory distress syndrome was developed and adopted into practice in a neonatal intensive care unit in February 2012. To evaluate the effects of implementing the new guideline in regard to the use of mechanical ventilation and surfactant, and the incidence of bronchopulmonary dypslasia. An historical cohort of very preterm infants (gestational age 26(0) to 32(6) weeks) born one year before guideline implementation was compared with a similar cohort of infants born one year following guideline implementation. Data were collected retrospectively from the local neonatal intensive care unit database. A total of 272 preterm infants were included in the study: 129 in the preguideline cohort and 143 in the postguideline cohort. Following the implementation of the guideline, the proportion of infants treated with ongoing mechanical ventilation was reduced from 49% to 26% (P<0.001) and there was a trend toward a reduction in bronchopulmonary dysplasia (27% versus 18%; P=0.07). There was no difference in the proportion of infants treated with surfactant (54% versus 50%). The implementation of the practice guideline helped to minimize the use of ongoing mechanical ventilation in preterm infants.

Abdominal compartment syndrome in trauma patients: New insights for predicting outcomes.

Context:Abdominal compartment syndrome (ACS) is associated with high morbidity and mortality among trauma patients. Several clinical and laboratory findings have been suggested as markers for ACS, and these may point to different types of ACS and complications.Aims:This study aims to identify the strength of association of clinical and laboratory variables with specific adverse outcomes in trauma patients with ACS.Settings and Design:A 5-year retrospective chart review was conducted at three Level I Trauma Centers in the City of Chicago, IL, USA.Subjects and Methods:A complete set of demographic, pre-, intra- and post-operative variables were collected from 28 patient charts.Statistical Analysis:Pearson's correlation coefficient was used to determine the strength of association between 29 studied variables and eight end outcomes.Results:Thirty-day mortality was associated strongly with the finding of an initial intra-abdominal pressure >20 mmHg and moderately with blunt injury mechanism. A lactic acid >5 mmol/L on admission was moderately associated with increased blood transfusion requirements and with acute renal failure during the hospitalization. Developing ACS within 48 h of admission was moderately associated with increased length of stay in the Intensive Care Unit (ICU), more ventilator days, and longer hospital stay. Initial operative intervention lasting more than 2 h was moderately associated with risk of developing multi-organ failure. Hemoglobin level <10 g/dL on admission, ongoing mechanical ventilation, and ICU stay >7 days were moderately associated with a disposition to long-term support facility.Conclusions:Clinical and lab variables can predict specific adverse outcomes in trauma patients with ACS. These findings may be used to guide patient management, improve resource utilization, and build capacity within trauma centers.

Use of the Blom Tracheotomy Tube with Suction Inner Cannula to Decontaminate Microorganisms from the Subglottic Space. A Proof of Concept.

Preventing pulmonary complications during mechanical ventilation via tracheotomy is a high priority. To investigate if the Blom tracheotomy tube with suction-above-the-cuff inner cannula reduced the quantity of normal flora and pathogens in supra- versus subglottic spaces. We enrolled 20 consecutive medical ICU adults requiring tracheostomy for mechanical ventilation in this proof-of-concept, prospective, single-center study. All participants received a Blom tracheotomy tube with suction-above-the-cuff inner cannula to decontaminate microorganisms from the supra- and subglottic spaces. Supra- and subglottic sputum samples were obtained for microbiologic analysis while an endotracheal tube was in place before tracheotomy and once per week for up to 4 weeks of mechanical ventilation after tracheotomy. Demographics, duration of endotracheal tube intubation, and duration of mechanical ventilation post-tracheotomy were recorded. There was a significant reduction for supraglottic (2.86 ± 1.11 [mean ± SD]) versus subglottic suction samples (2.48 ± 1.07) (paired t test, P = 0.048; Wilcoxon test, P = 0.045) when all data pairs for normal flora and pathogens were combined across times. There was a significant reduction of normal flora pooled across times in 19 data pairs for supraglottic (3.00 ± 1.05) versus subglottic suction samples (2.00 ± 0.94) (paired t test, P = 0.0004; Wilcoxon test, P = 0.0007). There was no significant reduction of pathogens pooled across times in 25 data pairs for supraglottic (2.76 ± 1.16) versus subglottic suction samples (2.84 ± 1.03) (paired t test, P = 0.75; Wilcoxon test, P = 0.83). Proof-of-concept was confirmed. The Blom tracheotomy tube with disposable suction-above-the-cuff inner cannula decontaminated microorganisms from the subglottic space when normal flora and pathogens were combined. Future research should investigate if decreased quantity of normal flora and pathogens in the subglottic space reduces the incidence of ventilator-associated pulmonary complications in critically ill patients requiring ongoing mechanical ventilation via tracheotomy.

Hints for cyclical recruitment of atelectasis during ongoing mechanical ventilation in lavage and oleic acid lung injury detected by SpO2 oscillations and electrical impedance tomography

ABSTRACTPurpose of the Study: Detection of cyclical recruitment of atelectasis after induction of lavage (LAV) or oleic acid injury (OAI) in mechanically ventilated pigs. Primary hypothesis is that oxygen oscillations within the respiratory cycle can be detected by SpO2 recordings (direct hint). SpO2 oscillations reflect shunt oscillations that can only be explained by cyclical recruitment of atelectasis. Secondary hypothesis is that electrical impedance tomography (EIT) depicts specific regional changes of lung aeration and of pulmonary mechanical properties (indirect hint). Materials and Methods: Three groups (each n = 7) of mechanically ventilated pigs were investigated applying above mentioned methods before and repeatedly after induction of lung injury: (1) sham treated animals (SHAM), (2) LAV, and (3) OAI. Results: Early oxygen oscillations occurred in the LAV group (mean calculated amplitude: 73.8 mmHg reflecting shunt oscillation of 11.2% in mean). In the OAI group oxygen oscillations occurred hours after induction of lung injury (mean calculated amplitude: 57.1 mmHg reflecting shunt oscillations of 8.4% in mean). The SHAM group had no relevant oxygen oscillations (<30 mmHg, shunt oscillations < 1.5%). Synchronously to oxygen oscillations, EIT depicted (1) a decrease of ventilation in dorsal areas, (2) an increase in ventral areas, (3) a decrease of especially dependent expiratory impedance, 3) an increase in late inspiratory flow especially in the dependant areas, (4) an increase in the speed of peak expiratory flow (PEF), and (5) a decrease of dorsal late expiratory flow. Conclusions: SpO2 and EIT recordings detect events that are interpreted as cyclical recruitment of atelectasis.

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Case Reports: Anti-N-methyl-d-aspartate (NMDA) receptor encephalitis is a condition in which anti-NMDA receptor antibodies cause severe neurological disorders. The condition usually requires transfer to the intensive care unit and prolonged ventilatory support. There are five stages: prodromal phase, psychotic phase, unresponsive phase, hyperkinetic phase, and gradual recovery phase. We report a case of a young man with severe agitation, requiring extremely large amounts of sedation with an initial unknown diagnosis. The patient initially presented with confusion to an outside hospital; he was diagnosed with and treated for seizures. One week later, he presented to an outside hospital with lower extremity weakness and further confusion and agitation, requiring high amounts of sedation and intubation. He was transferred to our institution for further work-up of his fevers, delirium, and agitation. MRI was unrevealing and EEG demonstrated severe diffuse encephalopathy without active seizures. Multiple lumbar punctures were performed with a bland CSF. Empiric antibiotics were discontinued. A variety of sedative cocktails were attempted without yielding any success for managing his extreme agitation. Without a definitive cause, it appeared that the patient would be subjected to on-going mechanical ventilation and combinations of high amounts of sedatives. However, final CSF findings revealed positive NMDA receptor antibody. The patient then underwent tests to evaluate for possible source of neoplasm. The ultrasound of the testicles and PET scan were both negative for cancer. He was placed on steroids and had several rounds of plasmapheresis. Due to minimal improvement, the patient was started on Rituximab and Cyclophosphamide. Agitation subsided and the patient was weaned off the ventilator. He began some rehabilitation in the hospital and was successfully discharged to the LTAC. This is a case of how severe agitation was not due to poor management with sedation but required diligent work-up to diagnosing a treatable condition. Anti-NMDA receptor encephalitis is an emerging diagnosis that should be considered in cases of psychosis and delirium, particularly in the ICU setting.

Inspiratory capacity at inflation hold in ventilated newborns

To study appropriateness of respiratory system compliance calculation using an inflation hold and compare it with ventilator readouts of pressure and tidal volume as well as with measurement of compliance of the respiratory system with the single-breath-single-occlusion technique gained with a standard lung function measurement. Prospective clinical trial. Level III neonatal unit of a university hospital. Sixty-seven newborns, born prematurely or at term, ventilated for a variety of pathologic conditions. A standardized sigh maneuver with a predefined peak inspiratory pressure of 30 cm H2O, termed inspiratory capacity at inflation hold, was applied. Using tidal volume, exhaled from inspiratory pause down to ambient pressure, as displayed by the ventilator, and predefined peak inspiratory pressure, compliance at inspiratory capacity at inflation hold conditions could be calculated as well as ratio of tidal volume and ventilator pressure using tidal volume and differential pressure at baseline ventilator settings: peak inspiratory pressure minus positive end-expiratory pressure. For the whole cohort, the equation for the regression between tidal volume at inspiratory capacity at inflation hold and compliance of the respiratory system was: compliance of the respiratory system = 0.052 * tidal volume at inspiratory capacity at inflation hold - 0.113, and compliance at inspiratory capacity at inflation hold conditions was closely related to the standard lung function measurement method of compliance of the respiratory system (R = 0.958). In contrast, ratio of tidal volume and ventilator pressure per kilogram calculated from the ventilator readouts and displayed against compliance of the respiratory system per kilogram yielded a broad scatter throughout the whole range of compliance; both were only weakly correlated (R = 0.309) and also the regression line was significantly different from the line of identity (p < .05). Peak inspiratory pressure at study entry did not affect the correlation between compliance at inspiratory capacity at inflation hold conditions and compliance of the respiratory system. After a standard sigh maneuver, inspiratory capacity at inflation hold and the derived quantity compliance at inspiratory capacity at inflation hold conditions can be regarded as a valid, accurate, and reliable surrogate measure for standard compliance of the respiratory system in contrast to ratio of tidal volume and ventilator pressure calculated from the ventilator readouts during ongoing mechanical ventilation at respective ventilator settings.

Assessment of a volume-dependent dynamic respiratory system compliance in ALI/ARDS by pooling breathing cycles

New methods were developed to calculate the volume-dependent dynamic respiratory system compliance (Crs) in mechanically ventilated patients. Due to noise in respiratory signals and different characteristics of the methods, their results can considerably differ. The aim of the study was to establish a practical procedure to validate the estimation of intratidal dynamic Crs. A total of 28 patients from intensive care units of eight German university hospitals with acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) were studied retrospectively. Dynamic volume-dependent Crs was determined during ongoing mechanical ventilation with the SLICE method, dynostatic algorithm and adaptive slice method. Conventional two-point compliance C2P was calculated for comparison. A number of consecutive breathing cycles were pooled to reduce noise in the respiratory signals. Crs-volume curves produced with different methods converged when the number of pooling cycles increased (n ≥ 7). The mean volume-dependent Crs of 20 breaths was highly correlated with mean C2P (C2P,mean = 0.945 × Crs,mean − 0.053, r2 = 0.968, p < 0.0001). The Bland–Altman analysis indicated that C2P,mean was lower than Crs,mean (−2.4 ± 6.4 ml cm−1 H2O, mean bias ± 2 SD), but not significant according to the paired t-test (p > 0.05). Methods for analyzing dynamic respiratory mechanics are sensitive to noise and will converge to a unique solution when the number of pooled cycles increases. Under steady-state conditions, assessment of the volume-dependent Crs in ALI/ARDS patients can be validated by pooling respiratory data of consecutive breaths regardless of which method is applied. Confidence in dynamic Crs determination may be increased with the proposed pooling.

Dynamic versus static respiratory mechanics in acute lung injury and acute respiratory distress syndrome

It is not clear whether the mechanical properties of the respiratory system assessed under the dynamic condition of mechanical ventilation are equivalent to those assessed under static conditions. We hypothesized that the analyses of dynamic and static respiratory mechanics provide different information in acute respiratory failure. Prospective multiple-center study. Intensive care units of eight German university hospitals. A total of 28 patients with acute lung injury and acute respiratory distress syndrome. None. Dynamic respiratory mechanics were determined during ongoing mechanical ventilation with an incremental positive end-expiratory pressure (PEEP) protocol with PEEP steps of 2 cm H2O every ten breaths. Static respiratory mechanics were determined using a low-flow inflation. The dynamic compliance was lower than the static compliance. The difference between dynamic and static compliance was dependent on alveolar pressure. At an alveolar pressure of 25 cm H2O, dynamic compliance was 29.8 (17.1) mL/cm H2O and static compliance was 59.6 (39.8) mL/cm H2O (median [interquartile range], p < .05). End-inspiratory volumes during the incremental PEEP trial coincided with the static pressure-volume curve, whereas end-expiratory volumes significantly exceeded the static pressure-volume curve. The differences could be attributed to PEEP-related recruitment, accounting for 40.8% (10.3%) of the total volume gain of 1964 (1449) mL during the incremental PEEP trial. Recruited volume per PEEP step increased from 6.4 (46) mL at zero end-expiratory pressure to 145 (91) mL at a PEEP of 20 cm H2O (p < .001). Dynamic compliance decreased at low alveolar pressure while recruitment simultaneously increased. Static mechanics did not allow this differentiation. The decrease in static compliance occurred at higher alveolar pressures compared with the dynamic analysis. Exploiting dynamic respiratory mechanics during incremental PEEP, both compliance and recruitment can be assessed simultaneously. Based on these findings, application of dynamic respiratory mechanics as a diagnostic tool in ventilated patients should be more appropriate than using static pressure-volume curves.

Analysis of Atelectasis, Ventilated, and Hyperinflated Lung During Mechanical Ventilation by Dynamic CT

To study the dynamics of lung compartments by dynamic CT (dCT) imaging during uninterrupted pressure-controlled ventilation (PCV) and different positive end-expiratory pressure (PEEP) settings in healthy and damaged lungs. Experimental animal investigation. Experimental animal facility of a university department. In seven anesthetized pigs, static inspiratory pressure volume curves were obtained to identify the individual lower inflection point (LIP) before and after saline solution lung lavage. During PCV, PEEP was adjusted 5 millibars (mbar) below the individually determined LIP (LIP - 5), at the LIP, and 5 mbar above the LIP (LIP + 5). Measurements were repeated before and after induction of lung damage. Hemodynamics, arterial and mixed venous blood gases, and dCT imaging in one juxtadiaphragmatic slice (effective temporal resolution of 100 ms) were assessed during uninterrupted PCV in series of three successive respiratory cycles. The mean fractional area (FA) of the hyperinflated lung (FA-H), mean FA of ventilated lung, mean FA of poorly ventilated lung, and mean FA of nonventilated lung (FA-NV), and the change in FA of the whole lung area (DeltaFA) were compared at different PEEP settings. Calculated pulmonary shunt (Qs/Qt) was compared to FA-NV. LIP + 5 decreased the amount of atelectasis (FA-NV) and increased hyperinflation (FA-H) in healthy and injured lungs. Cyclic changes of atelectasis (DeltaFA-NV) and hyperinflation (DeltaFA-H) were observed in both healthy and injured lungs. In the injured but not in the healthy lungs, the amount of cyclic changes of atelectasis and hyperinflation were independent from the adjusted PEEP level. FA-NV correlated with the calculated Qs/Qt, with a slight overestimation (mean +/- SEM, 2.1 +/- 4.1%). dCT imaging allows the following: (1) the quantification of the extent of atelectasis, ventilated, poorly ventilated, and hyperinflated lung parenchyma during ongoing mechanical ventilation; (2) the detection and quantification of repeated recruitment and derecruitment, as well as hyperinflation; and (3) an estimation of Qs/Qt. dCT adds promising functional information for the respiratory treatment of early ARDS.