[Change in therapy target and therapy limitations in intensive care medicine. Position paper of the Ethics Section of the German Interdisciplinary Association for Intensive Care and Emergency Medicine]. / Therapiezieländerung und therapiebegrenzung in der intensivmedizin. Positionspapier der Sektion Ethik der Deutschen Interdisziplinären Vereinigung für Intensiv- und Notfallmedizin.

The task of physicians is to maintain life, to protect and re-establish health as well as to alleviate suffering and to accompany the dying until death, under consideration of the self-determination rights of patients. Increasingly more and differentiated options for this are becoming available in intensive care medicine. Within the framework of professional responsibility physicians must decide which of the available treatment options are indicated. This process of decision-making is determined by answering the following question: when and under which circumstances is induction or continuation of intensive care treatment justified? In addition to the indications, the advance directive of the patient is the deciding factor. Medical indications represent a scientifically based estimation that a therapeutic measure is suitable in order to achieve a defined therapy target with a given probability. The ascertainment of the patient directive is achieved in a graded process depending on the state of consciousness of the patient. The present article offers orientation assistance to physicians for these decisions which are an individual responsibility.

[Decision-making support in Intensive Care to facilitate organ donation : Position paper of the Ethics Section and the Organ Donation and Transplantation Section of the German Interdisciplinary Association of Critical Care and Emergency Medicine (DIVI) in collaboration with the Ethics Section of the German Society of Medical Intensive Care Medicine and Emergency Medicine (DGIIN)]. / Entscheidungshilfe bei erweitertem intensivmedizinischem Behandlungsbedarf auf dem Weg zur Organspende : Positionspapier der Sektion Ethik und der Sektion Organspende und -transplantation der Deutschen Interdisziplinären Vereinigung für Intensiv- und Notfallmedizin (DIVI) unter Mitarbeit der Sektion Ethik der Deutschen Gesellschaft für Internistische Intensivmedizin und Notfallmedizin (DGIIN).

BACKGROUND AND CHALLENGE: Injuries, especially traumatic brain injury, or specific illnesses and their respective sequelae can result in the demise of the patients afflicted despite all efforts of modern intensive care medicine. If in principle organ donation is an option after a patient's death, intensive therapeutic measures are regularly required in order to maintain the homeostasis of the organs. These measures, however, cannot benefit the patient afflicted anymore-which in turn might lead to an ethical conflict between dignified palliative care for him/her and expanded intensive treatment to facilitate organ donation for others, especially if the patient has opted for the limitation of life-sustaining therapies in an advance directive. METHOD: The Ethics Section and the Organ Donation and Transplantation Section of the German Interdisciplinary Association of Critical Care and Emergency Medicine (DIVI) have convened several meetings and a telephone conference and have arrived at a decision-making aid as to the extent of treatment for potential organ donors. This instrument focusses first on the assessment of five individual dimensions regarding organ donation, namely the certitude of a complete and irreversible loss of all brain function, the patient's wishes as to organ donation, his or her wishes as to limiting life-sustaining therapies, the intensity of expanded intensive treatment for organ protection and the odds of its successful attainment. Then, the combination of the individual assessments, as graphically shown in a {Netzdiagramm}, will allow for a judgement as to whether a continuation or possibly an expansion of intensive care measures is ethically justified, questionable or even inappropriate. RESULT: The aid described can help mitigate ethical conflicts as to the extent of intensive care treatment for moribund patients, when organ donation is a medically sound option. NOTE: Gerald Neitzke und Annette Rogge contributed equally to this paper and should be considered co-first authors.

[Amendment to the documentation of decisions to withhold or withdraw life-sustaining therapies in consideration of wish to donate organs : Recommendation of the Ethics Section and the Organ Donation and Transplantation Section of the German Interdisciplinary Association of Critical Care and Emergency Medicine (DIVI) in collaboration with the Ethics Section of the German Society of Medical Intensive Care Medicine and Emergency Medicine (DGIIN)]. / Ergänzung des Dokumentationsbogens "Therapiebegrenzung" unter Berücksichtigung eines möglichen Organspendewunsches : Empfehlung der Sektion Ethik sowie der Sektion Organspende und Organtransplantation der Deutschen Interdisziplinären Vereinigung für Intensiv- und Notfallmedizin (DIVI) unter Mitarbeit der Sektion Ethik der Deutschen Gesellschaft für Internistische Intensivmedizin und Notfallmedizin (DGIIN).

The Ethics Section of the German Interdisciplinary Association of Critical Care and Emergency Medicine (DIVI) recently published a documentation for decisions to withhold or withdraw life-sustaining therapies. The wish to donate organs was not considered explicitly. Therefore the Ethics Section and the Organ Donation and Transplantation Section of the DIVI together with the Ethics Section of the German Society of Medical Intensive Care Medicine and Emergency Medicine worked out a supplementary footnote for the documentation form to address the individual case of a patient's wish to donate organs.

[The 40th anniversary of the German Interdisciplinary Association of Critical Care Medicine : A ceremonial address on the occasion of the anniversary]. / 40 Jahre Deutsche Interdisziplinäre Vereinigung für Intensiv- und Notfallmedizin : Ein Festvortrag anlässlich des Jubiläums.

During the 17th annual meeting, the German Interdisciplinary Association of Critical Care Medicine (DIVI) celebrated its 40th anniversary. On this occasion a speech was given with the following content. In 1977, the DIVI was founded as an umbrella association for medical societies involved in critical care. It became a well-respected representative for matters of critical care medicine. During the following period, many important recommendations for critical care were issued, such as on structural and staffing standards, further education, treatment concepts, etc. In 2007, DIVI was changed into a membership society. The activities within the society are mostly done within the sections where members of the various disciplines (internists, anesthesiologists, neurologists, etc.) and professions (physicians, nurses) cooperate together on special topics. Currently, critical care in Germany has to overcome severe problems: rigorous economic pressure, critical lack of staff, missing professional long-term perspectives for intensivists, weak representation at international conferences. DIVI and its contributing societies must urgently join together in order to overcome these existential problems.

[Introduction of the flat rate reimbursement system in Germany : A historical review]. / Einführung des Fallpauschalensystems in Deutschland : Ein geschichtlicher Rückblick.

With the new millenium, "Gesundsheitsreform 2000" (Health Reform 2000) fundamentally changed the principles for reimbursement of hospital treatment costs in Germany. Before then, hospital treatment was completely reimbursed by the health insurance companies. Now, reimbursement is entirely based on a new diagnosis-related group (DRG) payment system. The aim was a reduction of the expanding cost of the health care system, more efficient economics, and better control. This concept was unique, since until now reimbursement had nowhere been based 100% on a DRG system. For critical care medicine, this became a special problem because standardization of treatment procedures is nearly impossible and is not related to specific diagnoses. Therefore, completely new solutions had to be found for a fair reimbursement of critical care treatment. The difficult search for a good solution is described here. The DIVI (German Interdisciplinary Association of Critical Care and Emergency Medicine) was able to present good arguments and concepts based on actual and realistic cost analyses. However, the solutions found remain insufficient, and fundamental problems are still not solved.

[Cost analysis as a tool for assessing the efficacy of intensive care units]. / Kosten als Instrument zur Effizienzbeurteilung intensivmedizinischer Funktionseinheiten.

BACKGROUND: The German "Hospital Structure Act" intends to align the state hospital planning on quality criteria. Within this process cost-utility analyses (CUAs) shall be used to assess the efficacy of medical care. To be objective, CUAs of intensive care units (ICUs) require standardization (adjustment) of costs. The present study analyzed the extent to which treatment costs are related to patient-specific baseline variables (such as type and severity of the primary disease). METHODS: From 2000-2004, a bottom-up procedure was used to quantify total costs on 14 ICUs in nine German university hospitals. Results were combined with demographic data, and data indicating type (ICD-10 codes) and severity (ICU scoring systems) of the primary disease at ICU admission. Various statistical models were tested to identify that which best described the associations between baseline variables and costs. RESULTS: In all, 3803 critically ill patients could be examined. The median of treatment costs per patient was 3199 € (IQR 1768-6659 €). No model allowed an acceptably precise adjustment of costs; the estimated mean absolute prognostic error was at least 3860 € (mean relative prognostic error 66%), when we tested an Extreme Gradient Boosting Model. CONCLUSION: Instruments which are currently available (cost adjustment based on patient-specific baseline variables) do not allow a standardization of costs, and an objective CUA of ICUs. Factors unknown at baseline may cause a large portion of treatment costs.

Evaluation of respiratory inductive plethysmography in controlled ventilation: measurement of tidal volume and PEEP-induced changes of end-expiratory lung volume.

STUDY OBJECTIVE: To determine the accuracy of respiratory inductive plethysmography (RIP) with a respiratory monitor (Respitrace Plus; NIMS Inc., Miami) operating in the DC-mode for the measurement of tidal volumes (VT) and positive end-expiratory pressure (PEEP)-induced changes of end-expiratory lung volume (deltaEELV) in patients with normal pulmonary function, acute lung injury (ALI), and COPD during volume-controlled ventilation. DESIGN: Prospective comparison of RIP with pneumotachography (PT) for assessment of VT and with multibreath nitrogen washout procedure (N2WO) for determination of deltaEELV as reference methods. SETTING: Mixed ICU at a university hospital. PATIENTS: Thirty-one sedated and paralyzed patients: 12 patients with normal pulmonary function mechanically ventilated after major surgery, 10 patients with respiratory failure due to ALI, and 9 patients with a known history of COPD ventilated after surgery or because of respiratory failure due to bronchopulmonary infection. INTERVENTIONS: Stepwise increase of PEEP from 0 to 5 to 10 cm H2O and reduction to 0 cm H2O again. On each PEEP level, N2WO was performed. MEASUREMENTS AND MAIN RESULTS: The baseline drift of RIP averaged 25.4+/-29.1 mL/min but changed over a wide range even in single patient measurements. Determination of VT for single minutes revealed that 66.5% and 90.0% of all values were accurate within a range of +/-10% and +/-20%, respectively. The deviation for VT measurements between RIP and PT in patients with COPD was significantly (p<0.05) higher compared to patients with ALI or normal pulmonary function. The difference of deltaEELV between RIP and N2WO was 11.6+/-174.1 mL with correlation coefficients of 0.77 (postoperative and COPD patients) and 0.86 (ALI patients). However, just 25.8% and 46.2% were precise within +/-10% and +/-20%, respectively. deltaEELV determination in COPD patients differed more between RIP and N2WO than in the other groups, but this was not significant. CONCLUSION: In a mixed group of patients undergoing controlled ventilation, RIP using the Respitrace Plus monitor was not consistently precise enough for quantitative evaluation of VT and EELV when compared to our reference methods. This was most evident in patients with COPD. For long-term volume measurements, a better control of the baseline drift of RIP should be achieved.

Effects of early treatment with immunoglobulin on critical illness polyneuropathy following multiple organ failure and gram-negative sepsis.

OBJECTIVE: The evaluation of incidences and relating factors of severe persisting critical illness polyneuropathy (CIP) in survivors of multiple organ failure (MOF). DESIGN: Prospective study with an entry period of 24 months. Electrophysiological studies for the diagnosis of CIP were performed 1 or 2 days before the patients were discharged from the intensive care unit (ICU). Factors which might have been related to the development of CIP were identified by a retrospective chart analysis. SETTING: The interdisciplinary ICU of a university hospital. PATIENTS: Thirty-three patients who survived MOF. Sixteen of these critically ill patients developed severe sepsis due to nosocomial infections with gram-negative bacteria. RESULTS: In seven survivors of MOF and sepsis typical electrophysiological features of CIP, like spontaneous fibrillations and low compound muscle action potentials, were detectable at the time of discharge from the ICU. Seventeen patients with MOF following multiple trauma who developed no sepsis, and nine survivors of MOF with sepsis showed no signs of persisting CIP at the end of their ICU stay. Chart analysis revealed that eight survivors of MOF with sepsis and without the development of CIP had been treated with intravenous immunoglobulin (IVIG) with a dosage of 0.3 g/kg per day for 3 days immediately (within 24 h) after the diagnosis of sepsis. Four out of seven patients with MOF and sepsis who developed CIP were transferred to our ICU after the onset of sepsis and had not received IVIG treatment. The IVIG treatment in three patients was delayed for more than 24 h after the diagnosis of sepsis and was then omitted. Obviously not related to the development of CIP were aminoglycoside antibiotics, steroids, nutritional disturbances and episodes of hypotension or hypoxia. Neuromuscular blocking agents were not used during intensive care treatment. CONCLUSIONS: A high incidence of severe CIP persisting until the day of discharge from the ICU was related to gram-negative sepsis but not to MOF alone. Retrospective chart analysis suggested that early application of IVIG may prevent or mitigate this severe complication. However, these results have to be confirmed in a prospective, placebo-controlled study.

Intensive care training and specialty status in Europe: international comparisons. Task Force on Educational issues of the European Society of Intensive Care Medicine.

OBJECTIVE: To describe current arrangements for postgraduate training and speciality status for intensive care medicine in Europe, and to compare these with three other geographical regions: the Middle East, North America, and Australia and New Zealand. METHODS: An iterative survey, by questionnaire and direct discussion, of council members of the European Society of Intensive Care Medicine, national specialist societies with involvement in intensive care, and national experts, representing four geographical regions and 47 countries. RESULTS: For the purposes of analysis, countries with common training structures have been grouped together; the denominator therefore includes both countries and regions. Formal training programmes in intensive care medicine (ICM) are available in 18 (85%) of the 21 countries or regions surveyed. Twelve (57%) offer multidisciplinary access to intensive care training with a common core curriculum. In six (28%) training in ICM is available solely through anaesthesia. The duration of intensive care training required for recognition as a specialist in the 18 countries or regions with a formal programme ranges from 18 to 30 months, with a median of 24 months. All countries assess competence in intensive care, but methods for doing so vary widely. Eighteen countries or regions offer specialist registration (accreditation) in ICM; in 12 this is provided as dual accreditation in a base speciality and in ICM. CONCLUSIONS: There is substantial support for multidisciplinary training in ICM, as demonstrated by collaborative interspeciality developments in many countries. We propose that these national developments should be strengthened within Europe by the recognition of 'supra-speciality' status for ICM by the European Commission, and by the establishment of a multidisciplinary Board for training in ICM, with international agreement on core competencies and duration of training programmes, and a common approach to the assessment of competence through formal examination.

Pressure signal transmission of five commercially available oesophageal balloon catheters.

OBJECTIVE: Five commercially available oesophageal balloon catheters (OBCs) were tested to evaluate the accuracy in transmitting fast-changing pressure signals which can be observed, for example, during phrenic nerve stimulation. SETTING: Research laboratory of a university hospital. METHOD: The OBCs tested varied in length (900-1390 mm) and inner diameter (0.9-1.5 mm) as well as in balloon material [latex or polyvinylchloride (PVC)]. A 180-cm tube served as a control. A sudden pressure drop was generated by the explosion of a pressurized latex balloon. The time between the pressure drop and 75, 50, 25 and 10% of the maximal pressure was measured. RESULTS: The time intervals required to transduce a pressure drop of 90% varied between the different OBCs from 85 to 476 ms (control 32 ms). Transmission time was lower in OBCs with a larger inner diameter. Shortening the OBCs resulted in a further decrease in transmission time. CONCLUSION: The type of OBC used has an impact on signal processing. An OBCs with a short transmission time should be chosen, especially if fast pressure changes are to be evaluated such as during phrenic nerve stimulation.

High-dose intravenous magnesium sulfate in the management of life-threatening status asthmaticus.

In severe status asthmaticus basic medical treatment often fails to improve the patient's condition. Mechanical ventilation in this situation is associated with a high incidence of serious complications. After the bronchodilating effect of moderate-dose magnesium sulfate in asthmatic patients had been demonstrated in previous studies we treated five mechanically ventilated patients with refractory status asthmaticus successfully with high dosages of MgSO4 IV (10-20 g within 1 h depending on the bronchodilating effect). MgSO4 resulted in a significant decrease of peak airway pressure (43.0 +/- 6.8 to 32.0 +/- 8.0 cmH2O) and inspiratory flow resistance (22.7 +/- 7.0 to 11.9 +/- 6.0 cmH2O.l-1.s-1) within 1 h. The resulting serum magnesium levels after one hour were up to threefold of the normal serum levels. Although a maintainance dose of 0.4 g/h had been administered continuously during the following 24 h serum magnesium decreased towards normal values within this time. The only relevant side-effect was a mild to moderate arterial hypotension in two of the five patients during the high dose administration period of MgSO4 which responded readily to dopamine treatment.

Hydrogen peroxide in expired breath condensate of patients with acute respiratory failure and with ARDS.

OBJECTIVE: Measurement of hydrogen peroxide concentrations in breath condensate of mechanically ventilated patients with ARDS and with risk factors for developing ARDS. DESIGN: Open study in intensive care patients. SETTING: Intensive care units of the Clinics of the University of Göttingen, a primary care center. PATIENTS: 10 post-operatively ventilated patients as a control group and 26 patients with acute respiratory failure, 7 of them with ARDS, 12 with polytrauma, 4 with pneumonia, 3 with cardiogenic or nephrogenic pulmonary edema. INTERVENTIONS: None. MEASUREMENTS: Breath condensate was collected by a special cold trap and was analysed for H2O2 by a chemiluminescence method. Daily measurements were performed for 4.2 +/- 2.6 days (mean +/- SD) as soon as possible after manifestation of respiratory failure. RESULTS: Patients with acute respiratory failure exhibited higher H2O2 concentrations than control patients (median 95 nmol/l, range 76-144 nmol/l), with the highest median value found in the ARDS group (552 nmol/l, range 154-893). After clinical improvement, H2O2 concentrations decreased to the range of the control group. CONCLUSION: Since high concentrations of H2O2 in breath condensate were only found in patients with ARDS or with risk factors for ARDS, the results add to the existing evidence that reactive oxygen species are associated with some acute lung diseases.

End-expiratory lung impedance change enables bedside monitoring of end-expiratory lung volume change.

OBJECTIVE: The aim of the study was to investigate the effect of lung volume changes on end-expiratory lung impedance change (ELIC) in mechanically ventilated patients, since we hypothesized that ELIC may be a suitable parameter to monitor lung volume change at the bedside. DESIGN: Clinical trial on patients requiring mechanical ventilation. SETTINGS: Intensive care units of a university hospital. PATIENTS: Ten mechanically ventilated patients were included in the study. INTERVENTION: Patients were ventilated in volume-controlled mode with constant flow and respiratory rate. In order to induce changes in the end-expiratory lung volume (EELV), PEEP levels were increased from 0 mbar to 5 mbar, 10 mbar, and 15 mbar. At each PEEP level EELV was measured by an open-circuit nitrogen washout manoeuvre and ELIC was measured simultaneously using Electrical Impedance Tomography (EIT) with sixteen electrodes placed on the circumference of the thorax and connected with an EIT device. Cross-sectional electro-tomographic measurements of the thorax were performed at each PEEP level, and a modified Sheffield back-projection was used to reconstruct images of the lung impedance. ELIC was calculated as the average of the end-expiratory lung impedance change. RESULTS. Increasing PEEP stepwise from 0 mbar to 15 mbar resulted in an linear increase of EELV and ELIC according to the equation: y =0.98 x -0.68, r(2)=0.95. CONCLUSION: EIT is a simple bedside technique which enables monitor lung volume changes during ventilatory manoeuvres such as PEEP changes.

Determination of functional residual capacity (FRC) by multibreath nitrogen washout in a lung model and in mechanically ventilated patients. Accuracy depends on continuous dynamic compensation for changes of gas sampling delay time.

OBJECTIVE: Validation of an open-circuit multibreath nitrogen washout technique (MBNW) for measurement of functional residual capacity (FRC). The accuracy of FRC measurement with and without continuous viscosity correction of mass spectrometer delay time (TD) relative to gas flow signal and the influence of baseline FIO2 was investigated. DESIGN: Laboratory study and measurements in mechanically ventilated patients. SETTING: Experimental laboratory and anesthesiological intensive care unit of a university hospital. PATIENTS: 16 postoperative patients with normal pulmonary function (NORM), 8 patients with acute lung injury (ALI) and 6 patients with chronic obstructive pulmonary disease (COPD) were included. INTERVENTIONS: Change of FIO2 from baseline to 1.0. MEASUREMENTS AND MAIN RESULTS: FRC was determined by MBNW using continuous viscosity correction of TD(TDdyn), a constant TD based on the viscosity of a calibration gas mixture (TD0) and a constant TD referring to the mean viscosity between onset and end of MBNW (TDmean). Using TDdyn, the mean deviation between 15 measurements of three different lung model FRCs (FRCmeasured) and absolute volumes (FRCmodel) was 0.2%. For baseline FIO2 ranging from 0.21 to 0.8, the mean deviation between FRCmeasured and FRCmodel was -0.8%. However, depending on baseline FIO2, the calculation of FRC using TDmean and TD0 increased the mean deviation between FRCmeasured and FRCmodel to 2-4% and 8-12%, respectively. In patients (n = 30) the average repeatability coefficient was 6.0%. FRC determinations with TDmean and TD0 were 0.8-13.3% and 4.2-23.9% (median 2.7% and 8.7%) smaller than those calculated with TDdyn. CONCLUSION: A dynamic viscosity correction of TD improves the accuracy of FRC determinations by MBNW considerably, when gas concentrations are measured in a sidestream. If dynamic TD correction cannot be performed, the use of constant TDmean might be suitable. However, in patient measurements this can cause an FRC underestimation of up to 13%.

Improved determination of static compliance by automated single volume steps in ventilated patients.

A new method for determination the static compliance of the respiratory system is described ("static compliance by automated single steps"--SCASS). In 12 ventilated patients pressure/volume (P/V) curves were determined by automated repetitive occlusion (6 s) at single volume steps and compared to the conventional syringe method (SM). All measurements were corrected for effects of temperature, humidity and pressure (THP). SM was found to be significantly influenced by intrapulmonary gas exchange causing an effective mean volume deficit of 217.4 +/- 65.7 ml (BTPS) at the end of the deflation. In contrast to that, the short duration of occlusion in SCASS minimize the gas exchange effects. The methodical differences between both methods result in overestimation of the inflation compliance in the uncorrected SM (SMuncorr: 83.4 +/- 12.6; SCASS: 76.0 +/- 11.9 ml/cmH2O. p less than 0.01) and underestimation of the deflation compliance resp. (SMuncorr: 58.3 +/- 7.5; SCASS: 79.1 +/- 15.0 ml/cmH2O. p less than 0.005). In contrast to the P/V curves by SM no significant hysteresis was found by SCASS. Gas exchange seems to be the main reason for the hysteresis. Even after correcting gas exchange and THP effects a significant hysteresis remained. The SCASS method avoids these problems and allows furthermore an accurate checking of leaks.

Severe accidental hypothermia: rewarming strategy using a veno-venous bypass system and a convective air warmer.

OBJECTIVE: To study a rewarming strategy for patients with severe accidental hypothermia using a simple veno-venous bypass in combination with a convective air warmer. SETTING: Eighteen beds in a university hospital intensive care unit. PATIENTS: Four adults admitted with a core temperature less than 30 degrees C. Hypothermia was caused by alcoholic intoxication in three patients and by drug overdose in one patient. MEASUREMENTS AND MAIN RESULTS: All patients were rewarmed by a venovenous bypass and in three cases a convective air warmer was also used. At a bypass flow rate of 100-300 ml/min the mean increase in core temperature was 1.15 degrees C/h (Range: 1.1-1.2 degrees C/h). One patient died 2 days after rewarming as a consequence of a reactivated pancreatitis. The other three patients survived without neurological sequelae. CONCLUSION: This rewarming technique seems safe and effective and allowed the controlled rewarming of our patients who suffered from severe accidental hypothermia

Proportional assist versus pressure support ventilation: effects on breathing pattern and respiratory work of patients with chronic obstructive pulmonary disease.

OBJECTIVE: To investigate the breathing pattern and the inspiratory work of breathing (WOB(I)) in patients with chronic obstructive pulmonary disease (COPD) assisted with proportional assist ventilation (PAV) and conventional pressure support ventilation (PSV). DESIGN: Prospective controlled study. SETTING: Intensive care unit of a university hospital. PATIENTS: Thirteen COPD patients being weaned from mechanical ventilation. INTERVENTIONS: All patients were breathing PSV and two different levels of PAV. MEASUREMENTS AND MAIN RESULTS: During PAV (EVITA 2 prototype, Dräger, Germany), the resistance of the endotracheal tube (R(et)) was completely compensated while the patients' resistive and elastic loads were compensated for by approximately 80 % and 50 % (PAV(80) and PAV(50)), respectively. PSV was adjusted to match the same mean inspiratory pressure (Pinsp(mean)) as during PAV(80). Airway pressure, esophageal pressure and gas flow were measured over a period of 5 min during each mode. Neuromuscular drive (P(0.1)) was determined by inspiratory occlusions. Mean tidal volume (V(T)) was not significantly different between the modes. However, the coefficient of variation of V(T) was 10 +/- 4.%, 20 +/- 13 % and 15 +/- 8 % during PSV, PAV(80) and PAV(50), respectively. Respiratory rate (RR) and minute ventilation (V(E)) were significantly lower during PAV(80) as compared with both other modes, but the differences did not exceed 10 %. PAV(80) and PSV had comparable effects on WOB(I) and P(0.1), whereas WOB(I) and P(0.1) increased during PAV(50) compared with both other modes. CONCLUSION: Mean values of breathing pattern did not differ by a large amount between the investigated modes. However, the higher variability of V(T) during PAV indicates an increased ability of the patients to control V(T) in response to alterations in respiratory demand. A reduction in assist during PAV(50) resulted in an increase in WOB and indices of patient effort.

Intrinsic PEEP determined by static pressure-volume curves--application of a novel automated occlusion method.

OBJECTIVE: Evaluation of new computer-controlled occlusion procedure for determination of intrinsic PEEP in mechanically ventilated patients and comparison with the standard end-expiratory occlusion method. DESIGN: Prospective controlled study. SETTING: Intensive care unit of a university hospital. PATIENTS: 16 patients with acute respiratory failure of different degree and etiology. All patients were mechanically ventilated, heavily sedated and muscle paralyzed (non-depolarising relaxants). The type of ventilator, the inspiration/expiration ratio, FIO2 and PEEP were selected by the attending clinicians according to the patients' need and independently from the study. INTERVENTIONS: Static compliance of the respiratory system (Cstat) was determined at varying external end-expiratory pressure settings: ZEEP (= ambient pressure), PEEP of 5 cmH2O and 10 cmH2O. All other ventilator settings were kept constant during the entire procedure. MEASUREMENTS AND RESULTS: A computer-controlled occlusion method (SCASS) was used for determination of Cstat. Intrinsic PEEP was determined by SCASS as the extrapolated zero-volume intercept of the regression line of multiple pressure/volume data pairs (PEEPSCASSinspir and PEEPSCASSexpir). Directly thereafter intrinsic PEEP in this particular ventilatory setting was determined by end-expiratory occlusions (PEPPEEO). The intrinsic PEEP values of the different methods were nearly identical with a significant correlation (p < 0.0001). Mean values +/- SD: PEEPSCASSinspir 7.1 +/- 4.3 cmH2O; PEEPSCASSexpir 7.1 +/- 4.5 cmH2O; PEEPEEO 7.1 +/- 4.2 cmH2O. CONCLUSION: Since no significant difference between PEEPi values measured by the inspiratory and expiratory occlusion method (SCASS) was seen, this indicates that no alveolar recruitment occurred during the respiratory cycle. This study demonstrates that the automated occlusion method for measuring Cstat system can also be used with high accuracy for determination of intrinsic PEEP in mechanically ventilated patients.

Effect of low-level PEEP on inspiratory work of breathing in intubated patients, both with healthy lungs and with COPD.

OBJECTIVE: Evaluation of low-level PEEP (5 cm H2O) and the two different CPAP trigger modes in the Bennett 7200a ventilator (demand-valve and flow-by trigger modes) on inspiratory work of breathing (Wi) during the weaning phase. DESIGN: Prospective controlled study. SETTING: The intensive care unit of a university hospital. PATIENTS: Six intubated patients with normal lung function (NL), ventilated because of non-pulmonary trauma or post-operative stay in the ICU, and six patients recovering from acute respiratory failure due to exacerbation of chronic obstructive pulmonary disease (COPD), breathing either FB-CPAP or DV-CPAP with the Bennett 7200a ventilator. INTERVENTIONS: The patients studied were breathing with zero end-expiratory pressure (ZEEP), as well as CPAP of 5 cm H2O (PEEP), with the following respiratory modes: the demand-valve trigger mode, pressure support of 5 cm H2O, and the flow-by trigger mode (base flow of 20 l/min and flow trigger of 2 l/min). Furthermore, Wi during T-piece breathing was evaluated. MEASUREMENTS AND RESULTS: Wi was determined using a modified Campbell's diagram. Total inspiratory work (Wi), work against flow-resistive resistance (W(ires)), work against elastic resistance (Wiel), work imposed by the ventilator system (W(imp)), dynamic intrinsic positive end-expiratory pressure (PEEPidyn), airway pressure decrease during beginning inspiration (P(aw)) and spirometric parameters were measured. In the NL group, only minor, clinically irrelevant changes in the measured variables were detected. In the COPD group, in contrast, PEEP reduced Wi and its components W(ires) and Wiel significantly compared to the corresponding ZEEP settings. This was due mainly to a significant decrease in PEEPidyn when external PEEP was applied. Flow-by imposed less Wi on the COPD patients during PEEP than did demand-valve CPAP. Differences in W(imp) between the flow-by and demand-valve trigger models were significant for both groups. However, in relation to Wi these differences were small. CONCLUSION: We conclude that the application of low-level external PEEP benefits COPD patients because it reduces inspiratory work, mainly by lowering the inspiratory threshold represented by PEEPidyn. Differences between the trigger modes of the ventilator used in this study were small and can be compensated for by the application of a small amount of pressure support.