Wolfgang Eichler

Influence of body water distribution on skin thickness: measurements using high‐frequency ultrasound

Background Although it is known that the skin acts as a water reservoir and participates in the fluid content of the whole body, no method has been established to quantify the fluid shifts in superficial tissue.

The Accuracy of the Oxygen Washout Technique for Functional Residual Capacity Assessment During Spontaneous Breathing

BACKGROUND:Measurement of functional residual capacity (FRC) is of considerable interest for monitoring patients with lung injury. The lack of instruments has impeded routine bedside FRC measurement. Recently, a simple automated method for FRC assessment by O2 washout has been introduced. We designed this study to evaluate the accuracy of FRC measurement using the O2 washout technique. METHODS:The LUFU system (Draeger, Luebeck, Germany) estimates FRC by O2 washout, a variant of multiple breath nitrogen washout. This technique uses a sidestream O2-analyzer to calculate FRC from end-inspired and end-expired O2 concentrations during fast changes of Fio2. We measured FRC in 23 healthy, spontaneously breathing volunteers in the sitting position using three techniques: 1) helium dilution (FRC-He), 2) body plethysmography (FRC-bp), 3) oxygen washout (FRC-O2). RESULTS:FRC-O2 (mean 4.1 ± 1.1 L, range 2.4–6.9 L) corresponds with FRC-He (mean 4.0 ± 1.0 L, range 2.4–6.2 L; bias of FRC-O2: −0.2 ± 0.4 L) and FRC-bp (mean 4.2 ± 1.0 L, range 2.8–6.1 L; bias of FRC-O2: 0.1 ± 0.6 L). CONCLUSIONS:The bias and precision of the O2 washout technique using the LUFU system were clinically acceptable when compared with FRC-He and FRC-bp for FRC assessment in spontaneously breathing volunteers.

Functional Residual Capacity Changes After Different Endotracheal Suctioning Methods

BACKGROUND:Our primary objective was to investigate the effects of three different endotracheal suctioning procedures on functional residual capacity (FRC). METHODS:Using a crossover design, postoperative cardiac surgery patients (n = 20) received three different suctioning methods in randomized order: closed suctioning during pressure-controlled ventilation, closed suctioning during volume-controlled ventilation, and open suctioning. FRC was measured before and 20 min after the intervention. RESULTS AND CONCLUSIONS:FRC is reduced in postcardiac surgery patients after suctioning, regardless of which method is used. Certain patients may have very pronounced changes of FRC. Routine FRC measurements could complement respiratory monitoring to optimize respiratory therapy.

Automated Evaluation of Functional Residual Capacity by Oxygen Washout

Objective.Measurement of functional residual capacity (FRC) is of considerable interest for monitoring ventilated patients in ICUs. However, the lack of instruments that can be used in the clinical setting has so far impeded the routine application of this measurement. It was the aim of our study to evaluate the accuracy and the reproducibility of a simplified oxygen washout technique (FRC[O2]). Materials and methods.For the evaluation of FRC[O2], gas flow, CO2 and O2 concentrations were determined by the flow probe of an ICU ventilator, a mainstream capnometer and O2 analyser. In 30 volunteers FRC[O2] as measured during spontaneous breathing was compared to: 1. Helium dilution technique (FRC[He], n= 21), 2. Body plethysmography (FRC[bp], n= 9). In n= 7 male patients FRC[O2] was repeatedly evaluated during mechanical ventilation and compared to the preoperative FRC[bp]. Results.FRC[O2] corresponded well with FRC[He] (range: 1.9 to 6.0 l, bias of FRC[O2]: 0.53 l (95% CI 0.24 l to 0.82 l)) and FRC[bp] (range: 2.1 to 4.3 l, bias of FRC[O2] 0.03 l (95% CI –0.30 l to 0.37 l)). The mean of the repeated FRC[O2]-measurements (basic range: 1.3 to 3.6 l) during mechanical ventilation with unchanged ventilator settings stayed unchanged. The within subject-between error ranged from 0.1 to 0.4 l (mean = 0.23 l). Mean FRC[O2] during mechanical ventilation decreased to 66.6 percent of the preoperative mean FRC[bp]. Conclusions.The automated oxygen washout technique is a simple method to measure FRC in the ICU patient.

Assessment of fluid balance by measurement of skin tissue thickness during clinical anaesthesia.

Study objective: To determine if measuring skin tissue thickness by a recently developed 10 MHz ultrasound scan may be used as a valuable parameter to guide fluid therapy and detect fluid shifts to the extravascular space during surgical procedures in addition to central venous pressure (CVP).

Functional residual capacity-guided alveolar recruitment strategy after endotracheal suctioning in cardiac surgery patients.

Objective:To determine whether the results of functional residual capacity measurements after endotracheal suctioning could guide the decision to perform an alveolar recruitment maneuver and thus improve lung function. Design:Prospective, randomized, controlled interventional study. Setting:Intensive care unit of a university hospital. Patients:Fifty-nine mechanically ventilated patients within 2 hrs after elective cardiac surgery without preexisting lung diseases. Interventions:Patients received a standard suctioning procedure with disconnection of the ventilator (20 secs, 14 F catheter, 200 cm H2O negative pressure). Prospectively, patients were stratified into two groups by the postsuctioning functional residual capacity value (group A: functional residual capacity >94% of baseline; group B: functional residual capacity <94% of baseline). Both groups were randomized into either a recruitment maneuver (RM) group (positive end-expiratory pressure 15 cm H2O, peak inspiratory pressure 35–40 cm H2O for 30 secs, group RM) or a non-RM group, in which ventilation was resumed without an RM (group NRM), resulting in four groups. Measurements and Main Results:Functional residual capacity and arterial blood gases were recorded for up to 1 hr. In addition, distribution of ventilation was measured by means of electrical impedance tomography. The RM had an impact on distribution of ventilation, functional residual capacity, and oxygenation in patients with a decrease of functional residual capacity after suctioning. In contrast, the RM showed no impact on these parameters in patients with no decrease of functional residual capacity after suctioning. Conclusions:By measurements of functional residual capacity after endotracheal suctioning, patients profiting from a consecutive recruitment maneuver could be identified. Guiding the recruitment strategy on changes of functional residual capacity may improve patient care.

A rise of MMP-2 and MMP-9 in bronchoalveolar lavage fluid is associated with acute lung injury after cardiopulmonary bypass in a swine model

Postoperative acute lung injury (ALI) contributes to the morbidity and mortality following cardiopulmonary bypass (CPB). To determine whether the presence of matrix metalloproteinases (MMPs) is associated with ALI after CPB, MMP-2 and MMP-9 activities in bronchoalveolar lavage fluid (BALF) were compared with parameters indicating impaired gas exchange. In a prospective study, 17 minipigs were subjected to CPB for 60 min. Before and at five and 180 min after CPB, MMP-2 and MMP-9 were assayed in BALF and the arterial-alveolar gradient of oxygen tension (AaDO2), the pulmonary capillary wedge pressure (PCWP) and the water content of lung tissue samples (Wt) were evaluated and compared with baseline values. MMP-2 and MMP-9 increased significantly 5 minutes (2.1- and 6.2-fold, respectively) and 180 minutes (3.4- and 14.3-fold, respectively) post-CPB. AaDO2 and Wt, but not PCWP, increased significantly 180 minutes after CPB and only AaDO2, but not PCWP or Wt, was significantly correlated with MMP-2 (r /0.66, p /0.006) and MMP-9 (r /0.62, p /0.01). In conclusion, high levels of MMP-2 and MMP-9 in the pulmonary compartment are associated with ALI after CPB.

The impact of different step changes of inspiratory fraction of oxygen on functional residual capacity measurements using the oxygen washout technique in ventilated patients.

BACKGROUND:Functional residual capacity (FRC) measurements may help to guide respiratory therapy. Using the oxygen washout technique, FRC can be assessed at bedside during spontaneous breathing. High repeatability, crucial for monitoring, has not been shown in ventilated patients. A large step change of inspiratory fraction of oxygen (Fio2) (&Dgr;Fio2) may impede the clinical use in patients ventilated with high Fio2. We investigated the repeatability of FRC measurements and the impact of different &Dgr;Fio2 on this repeatability. METHODS:The LUFU system (Draeger Medical, Luebeck, Germany) estimates FRC by oxygen washout, a variant of multiple-breath-nitrogen-washout during a fast &Dgr;Fio2. In 20 postoperative cardiac surgery patients, FRC was measured in duplicate using &Dgr;Fio2 of 0.1, 0.2, and 0.6. RESULTS:There were no differences between repeated measurements of FRC, neither using a &Dgr;Fio2 of 0.1, 0.2 nor 0.6(&Dgr;0.1: 2.62 L ± 0.58, 2.62 L ± 0.59, P = 0.995; &Dgr;0.2: 2.70 L ± 0.59, 2.66 L ± 0.56, P = 0.258; &Dgr;0.6: 2.61 L ± 0.58, 2.59 L ± 0.58, P = 0,639). Coefficients of variation were 6.6%, 5.6%, and 6.6%, respectively. CONCLUSIONS:FRC can be measured in ventilated patients using the oxygen washout technique with a clinically acceptable repeatability. Repeatability is not significantly influenced whether using a &Dgr;Fio2 of 0.1, 0.2, or 0.6.

Clinical biochemical tissue monitoring during ischaemia and reperfusion in major vascular surgery

Background: Major vascular surgery with aortic cross-clamping is associated with temporary ischaemia of the lower limb due to lack of tissue blood flow. The present study was designed to determine if the short-term changes in cellular metabolism occurring during this situation can be detected by subcutaneous microdialysis. It was also hoped to ascertain if this new technique is useful in the continuous bedside monitoring of metabolism during aortic surgery. Methods: In a controlled clinical study 20 patients undergoing elective aortic surgery were monitored using microdialysis probes that were inserted in the subcutaneous tissue of the left lower limb and a non-ischaemic region (shoulder). Interstitial fluid was obtained and the concentrations of glucose and lactate during lower limb ischaemia and during reperfusion were measured and compared with concentrations observed in fluid obtained from the non-ischaemic control tissue. Results: Circulatory occlusion caused an immediate and significant decrease in the glucose/lactate ratio from 3·1±1·3 to 0·48±0·5 (P<0·05) that returned to preocclusion values within 2 h of commencing reperfusion. Conclusion: We suggest that microdialysis may be used both to assess acute changes in tissue metabolism during ischaemic periods and also to act as an additional tool for the detection of peri-operative acute variations in limb blood flow.

Blood levels of atrial natriuretic peptide, endothelin, cortisol and ACTH in patients undergoing coronary artery bypass grafting surgery with cardiopulmonary bypass

Previous studies demonstrated a bi-phasic time course with post-operative dissociation of blood levels of cortisol and ACTH in patients undergoing major surgery and critically ill patients. A possible role of endothelin and atrial natriuretic peptide (ANP) in the dissociation of concentrations of cortisol and ACTH in critically ill patients has been suggested. In the present study, we investigated the perioperative course of blood levels of endothelin, ANP, ACTH, and cortisol in 13 male patients undergoing cardiac surgery with cardiopulmonary bypass (CPB): group 1 consisted of 7 patients with an uneventful perioperative period and group 2 consisted of 6 patients with perioperative complications. Blood samples were taken pre-[T1], intra-[T2], post-operatively (on the day of surgery) [T3], as well as on the first [T4] and second [T5] post-operative days. Blood samples of endothelin, ANP, cortisol, and ACTH were measured using commercially available immunoassays. Perioperatively, a biphasic time course with post-operative dissociation of ACTH and cortisol concentrations was observed in all patients studied. Intraoperatively, during CPB, the highest levels of endothelin were found. Perioperatively, ANP and endothelin levels were elevated compared to pre-operative values up to the second post-operative day. On the second post-operative day, ANP concentrations were significantly higher in patients with complications in the perioperative period compared to those with an uneventful perioperative period. Our results suggest that: 1) plasma levels of ANP increased in patients with perioperative complications; 2) plasma levels of ANP may have prognostic value for patients undergoing cardiac surgery; and 3) the dissociation of ACTH and cortisol cannot solely be explained by the increase in endothelin-1 and ANP concentrations observed in patients undergoing major surgery.