Quality of life-related and non-quality of life-related issues in ICU survivors and non-ICU-treated controls: a multi-group exploratory factor analysis.

BACKGROUND: Quality of life (QoL) is a key outcome measure in healthcare. However, the heterogeneity in its definitions presents challenges in the objective evaluation of improvement. Universal questionnaires, tailored for a broad demographic group, inadequately represent the unique experiences of intensive care unit (ICU) survivors, including a lack of ability to discriminate issues related to QoL from issues that do not. METHODS: Using a 218-item, 13-domain provisional questionnaire, we assessed 395 adult ICU survivors, with a minimum 72-h stay at one of three Swedish university hospital ICUs, at 6 months to three years post-discharge. Their responses were compared to those of 195 controls, matched for age and sex and randomly recruited from the Swedish Population Registry. By multi-group exploratory factor analysis, we compared dimensionality in QoL perceptions between the two groups, emphasising patterns of correlation to 13 domain-specific QoL questions. Model fit was assessed using information criteria. Internal consistency reliability for each scale was determined using McDonald's omega or Cronbach's alpha. All analyses were conducted using Mplus, applying full information maximum likelihood to handle missing data. RESULTS: All domains except Cognition had a subset of questions correlating to the domain-specific QoL question in at least the ICU survivor group. The similarity between the two groups varied, with Physical health, Sexual health and Gastrointestinal (GI) functions mainly correlating the same issues to QoL in the two groups. In contrast, Fatigue, Pain, Mental health, activities of daily living, Sleep, Sensory functions and Work life showed considerable differences. In all, about one-fourth of the issues correlated to QoL in the ICU survivor group and about one-tenth of the issues in the control group. CONCLUSIONS: We found most issues experienced by ICU survivors to be unrelated to quality of life. Our findings indicate that the consequences of post-ICU issues may play a more significant role in affecting QoL than the issues themselves; issues restricting and affecting social life and work life were more related to QoL in ICU survivors than in non-ICU-treated controls. Caution is advised before associating all post-ICU problems with an effect on quality of life. TRIAL REGISTRATION: ClinicalTrials.gov Ref# NCT02767180; Registered 28 April 2016.

The relationship between ICU survivorship, comorbidity and educational level in quality of life after intensive care.

BACKGROUND: ICU survivors have lower quality of life (QoL) compared to a non-ICU-treated population. The reason for this is not fully understood, but differences in baseline characteristics may be an important factor. This study evaluates the roles of comorbidity and educational level as possible explanatory factors for differences in QoL in ICU survivors compared to a non-ICU-treated population. METHODS: Using a provisional questionnaire with 218 questions in 13 domains on QoL after intensive care, we compared the responses from 395 adult ICU survivors and 195 non-ICU-treated controls. An initial bivariable linear correlation analysis compared the responses from the two groups. Two secondary multivariable regression analyses tested for effect modification by comorbidity and educational level, respectively, on the effect on QoL from belonging to the ICU survivor group compared to the control group. RESULTS: There was a significant difference in QoL between the two groups in 170 of 218 (78%) questions. In the multivariable analyses, associations between group belonging and QoL remained in 139 questions. In 59 of these, both belonging to the ICU survivor group and comorbidity was associated to QoL, in parallel to each other. Comorbidity moderated the association between group belonging and QoL in six questions, with the highest proportion of questions within the domains of cognition and urinary functions, and the lowest proportion within appetite and alcohol, physical health, and fatigue. In 26 questions, both belonging to the ICU survivor group and educational level were associated to QoL, in parallel to each other. Educational level moderated the association between group belonging and QoL in 34 questions, with the highest proportion of questions within the domains of urinary functions, ADL and physical health, and the lowest proportion within the domains of cognition, appetite and alcohol, pain, sensory functions, and fatigue. CONCLUSIONS: Lower QoL seen in ICU survivors compared to non-ICU-treated controls, as measured by our provisional questionnaire, cannot be explained only by a higher burden of comorbidity, and rarely by only educational level. In issues where comorbidity or educational level was associated to QoL, it often was so in parallel to an association from belonging to the ICU survivor group. Comparing QoL in ICU survivors to that of a non-ICU-treated population may be adequate despite differences in baseline characteristics.

Outcome prediction for patients assessed by the medical emergency team: a retrospective cohort study.

BACKGROUND: Medical emergency teams (METs) have been implemented to reduce hospital mortality by the early recognition and treatment of potentially life-threatening conditions. The objective of this study was to establish a clinically useful association between clinical variables and mortality risk, among patients assessed by the MET, and further to design an easy-to-use risk score for the prediction of death within 30 days. METHODS: Observational retrospective register study in a tertiary university hospital in Sweden, comprising 2,601 patients, assessed by the MET from 2010 to 2015. Patient registry data at the time of MET assessment was analysed from an epidemiological perspective, using univariable and multivariable analyses with death within 30 days as the outcome variable. Predictors of outcome were defined from age, gender, type of ward for admittance, previous medical history, acute medical condition, vital parameters and laboratory biomarkers. Identified factors independently associated with mortality were then used to develop a prognostic risk score for mortality. RESULTS: The overall 30-day mortality was high (29.0%). We identified thirteen factors independently associated with 30-day mortality concerning; age, type of ward for admittance, vital parameters, laboratory biomarkers, previous medical history and acute medical condition. A MET risk score for mortality based on the impact of these individual thirteen factors in the model yielded a median (range) AUC of 0.780 (0.774-0.785) with good calibration. When corrected for optimism by internal validation, the score yielded a median (range) AUC of 0.768 (0.762-0.773). CONCLUSIONS: Among clinical variables available at the time of MET assessment, thirteen factors were found to be independently associated with 30-day mortality. By applying a simple risk scoring system based on these individual factors, patients at higher risk of dying within 30 days after the MET assessment may be identified and treated earlier in the process.

Long-term health-related quality of life and burden of disease after intensive care: development of a patient-reported outcome measure.

BACKGROUND: ICU survivorship includes a diverse burden of disease. Current questionnaires used for collecting information about health-related problems and their relation to quality of life lack detailed questions in several areas relevant to ICU survivors. Our aim was to construct a provisional questionnaire on health-related issues based on interviews with ICU survivors and to test if this questionnaire was able to show differences between ICU survivors and a control group. METHODS: Thirty-two ICU survivors were identified at a post-ICU clinic and interviewed at least six months after ICU discharge. Using an established qualitative methodology from oncology, all dysfunctions and disabilities were extracted, rephrased as questions and compiled into a provisional questionnaire. In a second part, this questionnaire was tested on ICU survivors and controls. Inclusion criteria for the ICU survivors were ICU stay at least 72 h with ICU discharge six months to three years prior to the study. A non-ICU-treated control group was obtained from the Swedish Population Register, matched for age and sex. Eligible participants received an invitation letter and were contacted by phone. If willing to participate, they were sent the questionnaire. Descriptive statistics were applied. RESULTS: Analysis of the interviews yielded 238 questions in 13 domains: cognition, fatigue, physical health, pain, psychological health, activities of daily living, sleep, appetite and alcohol, sexual health, sensory functions, gastrointestinal functions, urinary functions and work life. In the second part, 395 of 518 ICU survivors and 197 of 231 controls returned a completed questionnaire, the response rates being 76.2% and 85.3%, respectively. The two groups differed significantly in 13 of 22 comorbidities. ICU survivors differed in a majority of questions (p ≤ 0.05) distributed over all 13 domains compared with controls. CONCLUSIONS: This study describes the development of a provisional questionnaire to identify health-related quality of life issues and long-term burden of disease after intensive care. The questionnaire was answered by 395 ICU survivors. The questionnaire could identify that they experience severe difficulties in a wide range of domains compared with a control group. Trial registry ClinicalTrials.gov Ref# NCT02767180.

Transpulmonary driving pressure during mechanical ventilation-validation of a non-invasive measurement method.

BACKGROUND: Transpulmonary driving pressure plays an important role in today's understanding of ventilator induced lung injury. We have previously validated a novel non-invasive method based on stepwise increments of PEEP to assess transpulmonary driving pressure in anaesthetised patients with healthy lungs. The aim of this study was to validate the method in patients who were mechanically ventilated for different diagnoses requiring intensive care. METHODS: We measured transpulmonary pressure (Ptp) and calculated transpulmonary driving pressure (ΔPtp) in 31 patients undergoing mechanical ventilation in an intensive care unit. Parallel triplicate measurements were performed with the PEEP step method (PtpPSM) and the conventional oesophageal balloon method (Ptpconv). Their agreement was compared using the intraclass correlation coefficient (ICC) and the Bland Altman plot. RESULT: The coefficient of variation for the repeated measurements was 4,3 for ΔPtpPSM and 9,2 for ΔPtpconv. The ICC of 0,864 and the Bland Altman plot indicate good agreement between the two methods. CONCLUSION: The non-invasive method can be applied in mechanically ventilated patients to measure transpulmonary driving pressure with good repeatability and accuracy comparable to the traditional oesophageal balloon method.

Detailed measurements of oesophageal pressure during mechanical ventilation with an advanced high-resolution manometry catheter.

BACKGROUND: Oesophageal pressure (PES) is used for calculation of lung and chest wall mechanics and transpulmonary pressure during mechanical ventilation. Measurements performed with a balloon catheter are suggested as a basis for setting the ventilator; however, measurements are affected by several factors. High-resolution manometry (HRM) simultaneously measures pressures at every centimetre in the whole oesophagus and thereby provides extended information about oesophageal pressure. The aim of the present study was to evaluate the factors affecting oesophageal pressure using HRM. METHODS: Oesophageal pressure was measured using a high-resolution manometry catheter in 20 mechanically ventilated patients (15 in the ICU and 5 in the OR). Different PEEP levels and different sizes of tidal volume were applied while pressures were measured continuously. In 10 patients, oesophageal pressure was also measured using a conventional balloon catheter for comparison. A retrospective analysis of oesophageal pressure measured with HRM in supine and sitting positions in 17 awake spontaneously breathing patients is also included. RESULTS: HRM showed large variations in end-expiratory PES (PESEE) and tidal changes in PES (ΔPES) along the oesophagus. Mean intra-individual difference between the minimum and maximum end-expiratory oesophageal pressure (PESEE at baseline PEEP) and tidal variations in oesophageal pressure (ΔPES at tidal volume 6 ml/kg) recorded by HRM in the different sections of the oesophagus was 23.7 (7.9) cmH2O and 7.6 (3.9) cmH2O respectively. Oesophageal pressures were affected by tidal volume, level of PEEP, part of the oesophagus included and patient positioning. HRM identified simultaneous increases and decreases in PES within a majority of individual patients. Compared to sitting position, supine position increased PESEE (mean difference 12.3 cmH2O), pressure variation within individual patients and cardiac artefacts. The pressure measured with a balloon catheter did not correspond to the average pressure measured with HRM within the same part of the oesophagus. CONCLUSIONS: The intra-individual variability in PESEE and ΔPES is substantial, and as a result, the balloon on the conventional catheter is affected by many different pressures along its length. Oesophageal pressures are not only affected by lung and chest wall mechanics but are a complex product of many factors, which is not obvious during conventional measurements. For correct calculations of transpulmonary pressure, factors influencing oesophageal pressures need to be known. HRM, which is available at many hospitals, can be used to increase the knowledge concerning these factors. TRIAL REGISTRATION: ClinicalTrials.gov, NCT02901158.

Inhaled nitric oxide does not reduce mortality in patients with acute respiratory distress syndrome regardless of severity: systematic review and meta-analysis.

OBJECTIVE: Treatment with inhaled nitric oxide improves oxygenation but not survival in mechanically ventilated patients with acute respiratory distress syndrome, but the effect may depend on the severity of hypoxemia. Our objective was to determine whether nitric oxide reduces hospital mortality in patients with severe acute respiratory distress syndrome (PaO2/FIO2 ≤ 100 mm Hg) but not in patients with mild-moderate acute respiratory distress syndrome (100 < PaO2/FIO2 ≤ 300 mm Hg) at the time of randomization. DATA SOURCES: Data were collected from Medline, Embase, and Cochrane CENTRAL electronic databases (inception to May 2013); proceedings from five conferences (to May 2013); and trial registries (http://www.clinicaltrials.gov and http://www.controlled-trials.com). No language restrictions were applied. STUDY SELECTION: Two authors independently selected parallel-group randomized controlled trials comparing nitric oxide with control (placebo or no gas) in mechanically ventilated adults or postneonatal children with acute respiratory distress syndrome. DATA EXTRACTION: Two authors independently extracted data from included trials. Trial investigators provided subgroup data. Meta-analyses used within-trial subgroups and random-effects models. DATA SYNTHESIS: Nine trials (n = 1,142 patients) met inclusion criteria. Overall methodological quality was good. Nitric oxide did not reduce mortality in patients with severe acute respiratory distress syndrome (risk ratio, 1.01 [95% CI, 0.78-1.32]; p = 0.93; n = 329, six trials) or mild-moderate acute respiratory distress syndrome (risk ratio, 1.12 [95% CI, 0.89-1.42]; p = 0.33; n = 740, seven trials). Risk ratios were similar between subgroups (interaction p = 0.53). There was no between-trial heterogeneity in any analysis (I = 0%). Varying the PaO2/FIO2 threshold between 70 and 200 mm Hg, in increments of 10 mm Hg, did not identify any threshold at which the nitric oxide-treated patients had lower mortality relative to controls. CONCLUSIONS: Nitric oxide does not reduce mortality in adults or children with acute respiratory distress syndrome, regardless of the degree of hypoxemia. Given the lack of related ongoing or recently completed randomized trials, new data addressing the effectiveness of nitric oxide in patients with acute respiratory distress syndrome and severe hypoxemia will not be available for the foreseeable future.

Recent advances in and limitations of cardiac output monitoring by means of electrical impedance tomography.

BACKGROUND: Currently, the monitoring of cardiac output (CO) and stroke volume (SV) is mainly performed using invasive techniques. Therefore, performing CO monitoring noninvasively by means of electrical impedance tomography (EIT) would be advantageous for intensive care. Our hypothesis was that, by means of EIT, it is possible to assess heart rate (HR) and to quantify changes in SV due to changes in ventilator settings. METHODS: CO (HR and SV) of 14 pigs (32-40 kg body weight) was changed by incremental increases in positive end-expiratory pressure levels (0, 5, 10, 15, and 20 cm·H2O; ramp maneuver). This ramp maneuver was applied 4 times in each animal, yielding 43 evaluable single experiments. At each positive end-expiratory pressure level, SV was assessed by transpulmonary thermodilution using a PiCCO device. EIT data were acquired using a Dräger EIT Evaluation Kit 2. RESULTS: The EIT-based SV-related signal, Z(SV) (in [AU]), showed only a weak correlation (after excluding 2 measurements) with SV(TTD) of r = 0.58 (95% confidence interval, 0.43-0.71). If Z(SV) is calibrated by the reference 1 time for each experiment (defined as SVEIT), the correlation is approximately 0.85 (95% confidence interval, 0.78-0.90). A possible reason for the moderate correlation is the unexpected scaling pattern, leading to amplification of the cardiac impedance signal, found in some animals. The scaling is probably due to the imperfect reconstruction (i.e., a change of sensitivity) of the EIT images or to a change in the position of the heart. CONCLUSIONS: The hypothesis that EIT can be used to monitor CO and SV was confirmed, but further studies are required before this technique can be applied in clinical practice. HR was determined robustly and accurately. For SV monitoring, promising results were obtained in 80% of the experiments. However, unexpected scaling of the cardiac EIT signal causing inaccurate estimation of SV remains an issue. Before robust assessment of SV by EIT is suitable for clinical practice, the cause of and compensation for undesired scaling effects need to be investigated.

Isolated diastolic dysfunction is associated with increased mortality in critically ill patients.

PURPOSE: Left ventricular (LV) diastolic dysfunction is important in critically ill patients, but prevalence and impact on mortality is not well studied. We classified intensive care patients with normal left ventricular function according to current diastolic guidelines and explored associations with mortality. MATERIAL AND METHODS: Echocardiography was performed within 24 h of intensive care admission. Patients with reduced LV ejection fraction, regional wall motion abnormality, or a history of cardiac disease were excluded. Patients were classified according to the 2016 EACVI guidelines, Recommendations for the Evaluation of LV Diastolic Function by Echocardiography. RESULTS: Out of 218 patients, 162 (74%) had normal diastolic function, 21 (10%) had diastolic dysfunction, and 35 (17%) had indeterminate diastolic function. Diastolic dysfunction were more common in female patients, older patients and associated with sepsis, respiratory and cardiovascular comorbidity as well as higher SAPS Score. In a risk-adjusted logistic regression model, patients with indeterminate diastolic dysfunction (OR 4.3 [1.6-11.4], p = 0.004) or diastolic dysfunction (OR 5.1 [1.6-16.5], p = 0.006) had an increased risk of death at 90 days compared to patients with normal diastolic function. CONCLUSION: Isolated diastolic dysfunction, assessed by a multi-parameter approach, is common in critically ill patients and is associated with mortality. TRIAL REGISTRATION: Secondary analysis of data from a single-center prospective observational study focused on systolic dysfunction in intensive care unit patients (Clinical Trials ID: NCT03787810.

Electrical impedance tomography: potentials and pitfalls.

PURPOSE OF REVIEW: Electrical impedance tomography (EIT) is a useful noninvasive tool for monitoring ventilation finding its way into the clinical setting. The focus of this review is to discuss the balance between the potential for EIT as a clinical monitor accepting a level of uncertainty and the scientific demand for absolute perfection. RECENT FINDINGS: The controversy concerning whether EIT impedance changes can be safely used to monitor lung volume changes now appears to be solved after recent elegant studies. It is now high time to display lung volume changes measured by EIT in clinical units, that is in millilitres following calibration versus tidal volume. A growing number of indices for regional ventilation distribution are emerging some of which should be further evaluated and developed for clinical decision support. SUMMARY: Already now EIT is a useful clinical monitor. Still more work is needed to develop and interpret indices which are simple enough to be used in the clinical setting to guide the clinician towards effective and safe ventilator management.

A Consciously Applied, Design-Driven Dialogue Can Improve Healing Architecture.

OBJECTIVES: This article states that a consciously applied, design-driven dialogue can improve healing architecture. There are different forms of knowledge, beyond evidence, which are partly hidden from our consciousness. We call this type of knowledge tacit. By using a design-driven dialogue, where staff and management participate in the design process, this tacit knowledge may transform into a more conscious and explicit one, a kind of knowledge that will inform the architect's work in a richer way and thereby increase the possibilities for improving healthcare architecture. BACKGROUND: Among proponents of evidence-based design (EBD), there has been an aspiration toward rigor to avoid arbitrary decision making. The concept of evidence has been put forward as a way to achieve this. Some of the advocates of EBD have looked upon subjective and aesthetic decisions with great skepticism. However, today, there is a growing number of architects who have lately become critical of that attitude in design. They search for alternative ways to understand the use of different kinds of knowledge in order to promote better architecture. This article aims to overcome some contradictions between different ways of looking at the design process. METHODS: This discussion article is based on personal introspection and literature studies. The personal experiences referred to stem from three major design projects for general and forensic psychiatric care facilities. RESULTS: This article presents a tentative design theory on how a design-driven dialogue process can be formed in order to achieve better outcomes in healthcare architecture. CONCLUSIONS: How the design-process is driven has a vital influence for the physical environment and its impact on treatment outcomes.

Can Healing Architecture Increase Safety in the Design of Psychiatric Wards?

OBJECTIVES: The objective of this discussion paper is to deepen the discourse on the complex interrelationship between "healing architecture" and "safe architecture," here labeled "The healing and safety complex," for the benefit of those who want to make informed decisions in the design of future psychiatric wards. BACKGROUND: Today's psychiatric care sets the patient at the forefront. As a part of this ambition, the discussion regarding the patient's physical environment has also advanced. At the same time, staff are exposed to increasing threats and violence in their everyday work, which can lead to severe personal psychological suffering as well as physical injuries. The requirements of patients and staff are sometimes conflicting which has ethical implications. METHODS: The reasoning and arguments presented here mainly derive from discussions and dialogue with psychiatric facility management and other healthcare professionals in multidisciplinary working groups during the design process. RESULTS: Offering patients and staff a healing and safe environment is the most important architectural challenge in the design of psychiatric wards. How architects, management, and staff evaluate and balance the two aspects will have a crucial impact on the building's final design and atmosphere and thereby influence staff and patient safety as well as civil protection. CONCLUSIONS: In everyday practice, it is up to the multidisciplinary design teams and management to become better informed in order to make "the right decisions to the best of their ability" as evidence is still limited when it comes to "The healing and safety complex."

Regional left ventricular systolic dysfunction associated with critical illness: incidence and effect on outcome.

AIMS: Left ventricular (LV) dysfunction can be triggered by non-cardiac disease, such as sepsis, hypoxia, major haemorrhage, or severe stress (Takotsubo syndrome), but its clinical importance is not established. In this study, we evaluate the incidence and impact on mortality of LV dysfunction associated with critical illness. METHODS AND RESULTS: In this single-centre, observational study, consecutive patients underwent an echocardiographic examination within 24 h of intensive care unit (ICU) admission. LV systolic dysfunction was defined as an ejection fraction (EF) < 50% and/or regional wall motion abnormalities (RWMA). A cardiologist assessed patients with LV dysfunction for the presence of an acute or chronic cardiac disease, and coronary angiography was performed in high-risk patients. Of the 411 patients included, 100 patients (24%) had LV dysfunction and in 52 (13%) of these patients, LV dysfunction was not attributed to a cardiac disease. Patients with LV dysfunction and non-cardiac disease had higher mortality risk score (Simplified Acute Physiologic Score 3 score), heart rate, noradrenaline doses, and lactate levels as well as decreased EF, stroke volume, and cardiac output compared with patients with normal LV function. Diagnoses most commonly associated with LV dysfunction and non-cardiac disease were sepsis, respiratory insufficiency, major haemorrhage, and neurological disorders. RWMA (n = 40) with or without low EF was more common than global hypokinesia (n = 12) and was reversible in the majority of cases. Twelve patients had a circumferential pattern of RWMA in concordance with Takotsubo syndrome. Crude 30 day mortality was higher in patients with LV dysfunction and non-cardiac disease compared with patients with normal LV function (33% vs. 18%, P = 0.023), but not after risk adjustment (primary outcome) {odds ratio [OR] 1.56 [confidence interval (CI) 0.75-3.39], P = 0.225}. At 90 days, crude mortality was 44% and 22% (P = 0.002), respectively, in these groups. This difference was also significant after risk adjustment [OR 2.40 (CI 1.18-4.88), P = 0.016]. CONCLUSIONS: Left ventricular systolic dysfunction is commonly triggered by critical illness, is frequently seen as regional hypokinesia, and is linked to an increased risk of death. The prognostic importance of LV dysfunction in critical illness might be underestimated.

Changes over time in 30-day survival and the incidence of shockable rhythms after in-hospital cardiac arrest - A population-based registry study of nearly 24,000 cases.

OBJECTIVE: To determine changes over time in 30-day survival and the incidence of shockable rhythms after in-hospital cardiac arrest, from a countrywide perspective. METHODS: Patient information from the Swedish Registry for Cardiopulmonary Resuscitation was analysed in relation to monitoring level of ward and initial rhythm. The primary outcome was defined as survival at 30 days. Changes in survival and incidence of shockable rhythms were reported per year from 2008 to 2018. Also, epidemiological data were compared between two time periods, 2008-2013 and 2014-2018. RESULTS: In all, 23,186 unique patients (38.6% female) were included in the study. The mean age was 72.6 (SD 13.2) years. Adjusted trends indicated an overall increase in 30-day survival from 24.7% in 2008 to 32.5% in 2018, (on monitoring wards from 32.5% to 43.1% and on non-monitoring wards from 17.6% to 23.1%). The proportion of patients found in shockable rhythms decreased overall from 31.6% in 2008 to 23.6% in 2018, (on monitoring wards from 42.5% to 35.8 % and on non-monitoring wards from 20.1% to 12.9%). Among the patients found in shockable rhythms, the proportion of patients defibrillated before the arrival of cardiac arrest team increased from 71.0% to 80.9%. CONCLUSIONS: In an 11-year perspective, resuscitation in in-hospital cardiac arrest in Sweden was characterised by an overall increase in the adjusted 30-day survival, despite a decrease in shockable rhythms. An increased proportion, among the patients found in a shockable rhythm, who were defibrillated before the arrival of a cardiac arrest team may have contributed to the finding.

Can we estimate transpulmonary pressure without an esophageal balloon?-yes.

A protective ventilation strategy is based on separation of lung and chest wall mechanics and determination of transpulmonary pressure. So far, this has required esophageal pressure measurement, which is cumbersome, rarely used clinically and associated with lack of consensus on the interpretation of measurements. We have developed an alternative method based on a positive end expiratory pressure (PEEP) step procedure where the PEEP-induced change in end-expiratory lung volume is determined by the ventilator pneumotachograph. In pigs, lung healthy patients and acute lung injury (ALI) patients, it has been verified that the determinants of the change in end-expiratory lung volume following a PEEP change are the size of the PEEP step and the elastic properties of the lung, ∆PEEP × Clung. As a consequence, lung compliance can be calculated as the change in end-expiratory lung volume divided by the change in PEEP and esophageal pressure measurements are not needed. When lung compliance is determined in this way, transpulmonary driving pressure can be calculated on a breath-by-breath basis. As the end-expiratory transpulmonary pressure increases as much as PEEP is increased, it is also possible to determine the end-inspiratory transpulmonary pressure at any PEEP level. Thus, the most crucial factors of ventilator induced lung injury can be determined by a simple PEEP step procedure. The measurement procedure can be repeated with short intervals, which makes it possible to follow the course of the lung disease closely. By the PEEP step procedure we may also obtain information (decision support) on the mechanical consequences of changes in PEEP and tidal volume performed to improve oxygenation and/or carbon dioxide removal.

Regional lung derecruitment after endotracheal suction during volume- or pressure-controlled ventilation: a study using electric impedance tomography.

OBJECTIVE: To assess lung volume and compliance changes during open- and closed-system suctioning using electric impedance tomography (EIT) during volume- or pressure-controlled ventilation. DESIGN AND SETTING: Experimental study in a university research laboratory. SUBJECTS: Nine bronchoalveolar saline-lavaged pigs. INTERVENTIONS: Open and closed suctioning using a 14-F catheter in volume- or pressure-controlled ventilation at tidal volume 10 ml/kg, respiratory rate 20 breaths/min, and positive end-expiratory pressure 10 cmH2O. MEASUREMENTS AND RESULTS: Lung volume was monitored by EIT and a modified N2 washout/-in technique. Airway pressure was measured via a pressure line in the endotracheal tube. In four ventral-to-dorsal regions of interest regional ventilation and compliance were calculated at baseline and 30 s and 1, 2, and 10 min after suctioning. Blood gases were followed. At disconnection functional residual capacity (FRC) decreased by 58+/-24% of baseline and by a further 22+/-10% during open suctioning. Arterial oxygen tension decreased to 59+/-14% of baseline value 1 min after open suctioning. Regional compliance deteriorated most in the dorsal parts of the lung. Restitution of lung volume and compliance was significantly slower during pressure-controlled than volume-controlled ventilation. CONCLUSIONS: EIT can be used to monitor rapid lung volume changes. The two dorsal regions of the lavaged lungs are most affected by disconnection and suctioning with marked decreases in compliance. Volume-controlled ventilation can be used to rapidly restitute lung aeration and oxygenation after lung collapse induced by open suctioning.

Transpulmonary and pleural pressure in a respiratory system model with an elastic recoiling lung and an expanding chest wall.

BACKGROUND: We have shown in acute lung injury patients that lung elastance can be determined by a positive end-expiratory pressure (PEEP) step procedure and proposed that this is explained by the spring-out force of the rib cage off-loading the chest wall from the lung at end-expiration. The aim of this study was to investigate the effect of the expanding chest wall on pleural pressure during PEEP inflation by building a model with an elastic recoiling lung and an expanding chest wall complex. METHODS: Test lungs with a compliance of 19, 38, or 57 ml/cmH2O were placed in a box connected to a plastic container, 3/4 filled with water, connected to a water sack of 10 l, representing the abdomen. The space above the water surface and in the lung box constituted the pleural space. The contra-directional forces of the recoiling lung and the expanding chest wall were obtained by evacuating the pleural space to a negative pressure of 5 cmH2O. Chest wall elastance was increased by strapping the plastic container. Pressure was measured in the airway and pleura. Changes in end-expiratory lung volume (ΔEELV), during PEEP steps of 4, 8, and 12 cmH2O, were determined in the isolated lung, where airway equals transpulmonary pressure and in the complete model as the cumulative inspiratory-expiratory tidal volume difference. Transpulmonary pressure was calculated as airway minus pleural pressure. RESULTS: Lung pressure/volume curves of an isolated lung coincided with lung P/V curves in the complete model irrespective of chest wall stiffness. ΔEELV was equal to the size of the PEEP step divided by lung elastance (EL), ΔEELV = ΔPEEP/EL. The end-expiratory "pleural" pressure did not increase after PEEP inflation, and consequently, transpulmonary pressure increased as much as PEEP was increased. CONCLUSIONS: The rib cage spring-out force causes off-loading of the chest wall from the lung and maintains a negative end-expiratory "pleural" pressure after PEEP inflation. The behavior of the respiratory system model confirms that lung elastance can be determined by a simple PEEP step without using esophageal pressure measurements.