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Description / Table of Contents: Abstract. Intrinsic positive end-expiratory pressure (PEEPi) occurring during mechanical ventilation depends on expiratory time constants, expiratory volume and expiration time as well as on external flow resistance (tubes, valves, etc.). It is not routinely determined in mechanically ventilated patients, but it is necessary to optimize respirator settings. The aim of the present study was the validation of an automated PEEPi determination method implemented in the respirator EVITA (Drägerwerke, Lübeck) in mechanically ventilated patients with acute lung failure. Patients. The method was validated in ten sedated, myorelaxed patients with respiratory insufficiency of different etiologies (five with restrictive, and five with obstructive pulmonary disease). PEEPi was determined using the volume constant ventilatory mode at ZEEP or at an external PEEP of 5 as well as 10 cm H2O. Method. PEEPi was first determined with the automated method implemented in the EVITA (five measurements at each end-expiratory pressure level; PEEPEvita). Steady-state was attained between each measurement. These values were compared to the results obtained with end-expiratory occlusion (external, computer-controlled valve in the inspiratory limb of the circuit) at the respective pressure levels (PEEPEEO). The average of five measurements at each PEEP level with each method was defined as PEEPi for the particular ventilatory situation. Gas flow was measured at the proximal end of the endotracheal tube with a heated pneumotachometer (Fleisch no. 2, Fleisch, Lausanne, Switzerland) and a differential pressure transducer. Tracheal pressure was determined in the same position with a further differential pressure transducer (Dr. Fenyves & Gut, Basel, Switzerland). After A/D conversion, data were sampled with a frequency of 20 Hz and processed on an IBM compatible PC. Software for data collection and processing as well as for control of the occlusion valve was self-programmed. For the statistical analysis we used the Mann-Whitney U-test or Wilcoxon signed-ranks test; a P value less than 0.05 was considered significant. Results. At the given respiratory setting and without PEEP patients with obstructive lung disease had a higher PEEPi (median: 6.4 cm H2O; range: 5.0 – 9.6 cm H2O) than those with restrictive pulmonary disease (median: 2.3 cm H2O; range: 0.8 – 3.0 cm H2O) (P〈0.05). Increasing external PEEP to 5 or 10 cm H2O significantly decreased the pressure difference between PEEPi and external PEEP (P〈0.05), but was unable to eliminate it completely. There was no statistically significant difference between PEEPEEO and PEEPEvita (P=0.43; Wilcoxon signed-ranks tests). Regression analysis showed a highly significant correlation between PEEPEEO and PEEPEvita values (r=0.985, P〈0.001; y=1.03x−0.18). Discussion. PEEPi occurs during ventilation in patients with obstructive and restrictive lung disease. The difference between external end-expiratory pressure and PEEPi decreases with increasing external PEEP. However, PEEPi may increase with increasing external PEEP in some instances. The reason for this may be that the PEEPi determined at the proximal end of the endotracheal tube represents only a mean value of different PEEPi values of various lung regions. Increasing external PEEP only partially alters this mean value due to an effect on PEEPi values lower than external PEEP. The PEEPi values measured by the EVITA respirator compared with classical end-expiratory occlusion with an external valve were nearly identical. Unfortunately, PEEPi measurement of the EVITA can only be performed during controlled and not during assisting (PSV, BIPAP etc.) ventilation. Optimal respirator settings require a knowledge of PEEPi (i.e., adaption of external PEEP for lowering the work of breathing in COPD patients or prolongation of the expiratory phase to avoid unwanted side effects of an occult PEEPi on the circulation). Since modern microprocessor-controlled respirators can easily be updated with the necessary equipment, measurement of PEEPi should be a part of routine ventilatory monitoring today.

Description / Table of Contents: Abstract During pressure support ventilation (PSV), the timing of the breathing cycle is mainly controlled by the patient. Therefore, the delivered flow pattern during PSV might be better synchronised with the patient's demands than during volume-assisted ventilation. In several modern ventilators, inspiration is terminated when the inspiratory flow decreases to 25% of the initial peak value. However, this timing algorithm might cause premature inspiration termination if the initial peak flow is high. This could result not only in an increased risk of dyssynchronization between the patient and the ventilator, but also in reduced ventilatory support. On the other hand, a decreased peak flow might inappropriately increase the patient's inspiratory effort. The aim of our study was to evaluate the influence of the variation of the initial peak-flow rate during PSV on respiratory pattern and mechanical work of breathing. Patients. Six patients with chronic obstructive pulmonary disease (COPD) and six patients with no or minor nonobstructive lung pathology (control) were studied during PSV with different inspiratory flow rates by variations of the pressurisation time (Evita I, Drägerwerke, Lübeck, Germany). During the study period all patients were in stable circulatory conditions and in the weaning phase. Method. Patients were studied in a 45° semirecumbent position. Using the medium pressurization time (1 s) during PSV the inspiratory pressure was individually adjusted to obtain a tidal volume of about 8 ml/kg body weight. Thereafter, measurements were performed during five pressurization times (〈0.1, 0.5, 1, 1.5, 2 s defined as T 0.1, T 0.5, T 1, T 1.5 and T 2) in random order, while maintaining the pressure support setting at the ventilator. Between each measurement steady-state was attained. Positive end-exspiratory pressure (PEEP) and FIO2 were maintained at prestudy levels and remained constant during the study period. Informed consent was obtained from each patient or his next of kin. The study protocol was approved by the ethics committee of our medical faculty. Gas flow was measured at the proximal end of the endotracheal tube with a pneumotachometer (Fleisch no. 2, Fleisch, Lausanne, Switzerland) and a differential pressure transducer. Tracheal pressure (Paw) was determined in the same position with a second differential pressure transducer (Dr. Fenyves & Gut, Basel, Switzerland). Esophageal pressure (Pes) was obtained by a nasogastric balloon-catheter (Mallinckrodt, Argyle, NY, USA) connected to a further differential pressure transducer of the same type as described above. The balloon was positioned 2–3 cm above the dome of the diaphragm. The correct balloon position was verified by an occlusion test as described elsewhere. The data were sampled after A/D conversion with a frequency of 20 Hz and processed on an IBM-compatible PC. Software for data collection and processing was self-programmed using a commercially available software program (Asyst 4.0, Asyst Software Technologies, Rochester, NY, USA). Patient's inspiratory work of breathing Wpi (mJ/l) was calculated from Pes/volume plots according to the modified Campbell's diagram. Dynamic intrinsic PEEP (PEEPidyn) was obtained from esophageal pressure tracings relative to airway pressure as the deflection in Pes before the initiation of inspiratory flow Patient's additive work of breathing (Wadd) against ventilator system resistance was calculated directly from Paw/V tracings when Paw was lower than the pressure on the compliance curve. Two-way analysis of variance (ANOVA) was used for statistical analysis, followed by post hoc testing of the least significant difference between means for multiple comparisons. Probability values less than 0.05 were considered as significant. Results. COPD patients had significantly higher pressure support than control patients. With decreasing inspiratory flow, Wpi increased significantly in COPD patients. Additionally, the duct cycle (Ti/Ttot) significantly increased with decreased flow rates which resulted in a higher PEEPidyn compared to the baseline. At T 1.5 and T 2 with lower flow rates, the pre-set pressure support level was not achieved within inspiration in the COPD patients. Wadd increased significantly at T 1, T 1.5 and T 2 in COPD patients and at T 1.5 and T 2 in the control group. In one patient, premature termination of inspiration owing to high initial peak flow was corrected by adjustment of the inspiratory flow. Conclusion. Our results demonstrate that a decreased peak flow during PSV resulted in increased patient's work of breathing in COPD patients. During lower flow, the pre-set pressure support level was not attained and additional work had to be done on the ventilator system. Furthermore, the higher PEEPidyn during lower flow rates indicates a higher risk of dynamic pulmonary hyperinflation in patients with COPD. We conclude that the use of pressurization times ≥1 s to decrease inspiratory peak flow during PSV is of no benefit and should be avoided, particularly in COPD patients. However, in selected cases, slight decrease of inappropriately high peak flows might be useful for optimization of PSV setting to avoid premature termination of inspiration.

Description / Table of Contents: Abstract We report the case of a 35-year-old male who was admitted to the intensive care unit because of somnolence due to accidental hypothermia. Initial examination showed a Glasgow coma score of 10 and a rectal temperature of 27.4° C. Because of stable circulatory conditions, there was no mandatory indication for rewarming by means of cardiopulmonary bypass. We rewarmed the patient with an extracorporeal veno-venous haemofiltration device combined with a countercurrent fluid warmer. An average increase in body temperature of 1.34° Ch−1 could be obtained. We conclude that the described technique represents an effective and well-controllable method for treatment of hypothermia in patients with stable haemodynamic conditions. Because of the availability of the required equipment, this method can also be practised in hospitals without cardiac surgical departments and cardiopulmonary bypass facilities.

Description / Table of Contents: Abstract Pyoderma gangrenosum (PG) is a necrotizing and ulcerative skin disease of unknown cause. The pathogenesis is thought to be related to a defective immune response. The ulcerations appear spontaneously or after skin trauma. Development in a surgical wound can be misinterpreted as wound infection. However, in contrast to postoperative infections, treatment of PG requires immunosuppressive therapy. We report a case of PG following hipjoint surgery that was complicated by a severe life-threatening systemic inflammatory response syndrome (SIRS). Typically, wound and blood cultures were negative for pathogens. Prednisolone stopped the activity of the disease promptly.

Description / Table of Contents: Abstract In clinical practice, the administration of supplementary albumin often depends on the measured plasma concentration of total protein (TPC). A TPC of less than 5 g/dl is generally accepted as an indication for albumin therapy, assuming an albumin concentration of less than 2.5 g/dl. However, a physiological relation between TPC and albumin cannot be expected in critically ill patients, and thus, measurement of TPC may be misleading as an indicator for the use of albumin. Therefore, we investigated the sensitivity and specificity of TPC testing for diagnosing hypoalbuminaemia requiring treatment. Methods. In this prospective study, 210 consecutive patients were included. Protein electrophoresis was performed three times a week; the second electrophoresis was selected for evaluation. Applied statistical analysis revealed the number of positive total protein tests indicating hypalbuminaemia requiring treatment (sensitivity) and the number of negative with tolerably reduced albumin concentrations (specificity). Results. Of the investigated patients, 27.6% had normal TPCs between 6.2 and 8.0 g/dl. In 81.9% of cases an albumin concentration below 3.5 g/dl was found, while 43 patients had a concentration below 2.5 g/dl. The sensitivity and specificity of TPC measurement for the diagnosis of clinically relevant hypoalbuminaemia (albumin concentration 〈2.5 g/dl) was calculated at different cutoff points for total protein. With a TPC of 6.0 g/dl, the sensitivity was 0.96 and the specificity 0.44. With a cutoff point of 5.0 g/dl, the sensitivity was reduced to 0.65 and specificity increased to 0.86. Finally, with a TPC of 4.0 g/dl sensitivity was 0.25 and specificity almost 1. Conclusions. Depending on the cutoff point for TPC, a relevant albumin requirement would frequently not be detected. In other cases, a need for albumin would be assumed from a reduced TPC even though the albumin concentration still exceeded 2.5 g/dl. Therefore, determination of TPC is not a suitable indicator of the need for albumin replacement. As a result, we suggest routine determination of albumin concentrations instead of TPC.

Description / Table of Contents: Abstract A commercially available C1 inhibitor (C1-INH) concentrate was used for short-term prophylaxis before surgery in two patients with hereditary angioneurotic oedema. The patients suffered from recurrent subcutaneous and submucosal oedema of the face, extremities, and gastrointestinal tract as the result of a hereditary C1-INH deficiency. Both patients were receiving tranexamic acid or danazol therapy as oral long-term prophylaxis. Over the years the patients underwent several operations in regional and general anaesthesia, with mask ventilation or intubation. The C1-INH plasma concentrations measured preoperatively were always very low (0.02–0.06 g/l, normal range 0.15–0.35 g/l), despite the oral long-term prophylaxis. Substitution treatment with 500–1000 U C1-INH was performed 1 h before surgery. No side effects were seen following the concentrate infusions. With this substitution treatment no specific symptoms of hereditary angioneurotic oedema were recognized in either case. The measurement of C1-INH plasma concentration 2 h or 4 h after C1-INH substitution showed a marked rise in both patients, though normal values were not reached in either. We suggest that infusion of C1 concentrate is an appropriate form of preoperative substitution treatment in patients with hereditary angioneurotic oedema, in view of the lower risk of infection than with infusion of fresh-frozen plasma and the observed effectiveness.