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O Stenqvist

Publications and source records attributed to O Stenqvist.

At least 19 recordsLinked to original sources
PubMed2006

Positive end-expiratory pressure optimization using electric impedance tomography in morbidly obese patients during laparoscopic gastric bypass surgery.

BACKGROUND: Morbidly obese patients have an increased risk for peri-operative lung complications and develop a decrease in functional residual capacity (FRC). Electric impedance tomography (EIT) can be used for continuous, fast-response measurement of lung volume changes. This method was used to optimize positive end-expiratory pressure (PEEP) to maintain FRC. METHODS: Fifteen patients with a body mass index of 49 +/- 8 kg/m(2) were studied during anaesthesia for laparoscopic gastric bypass surgery. Before induction, 16 electrodes were placed around the thorax to monitor ventilation-induced impedance changes. Calibration of the electric impedance tomograph against lung volume changes was made by increasing the tidal volume in steps of 200 ml. PEEP was titrated stepwise to maintain a horizontal baseline of the EIT curve, corresponding to a stable FRC. Absolute FRC was measured with a nitrogen wash-out/wash-in technique. Cardiac output was measured with an oesophageal Doppler method. Volume expanders, 1 +/- 0.5 l, were given to prevent PEEP-induced haemodynamic impairment. RESULTS: Impedance changes closely followed tidal volume changes (R(2) > 0.95). The optimal PEEP level was 15 +/- 1 cmH(2)O, and FRC at this PEEP level was 1706 +/- 447 ml before and 2210 +/- 540 ml after surgery (P < 0.01). The cardiac index increased significantly from 2.6 +/- 0.5 before to 3.1 +/- 0.8 l/min/m(2) after surgery, and the alveolar dead space decreased. P(a)O2/F(i)O2, shunt and compliance remained unchanged. CONCLUSION: EIT enables rapid assessment of lung volume changes in morbidly obese patients, and optimization of PEEP. High PEEP levels need to be used to maintain a normal FRC and to minimize shunt. Volume loading prevents circulatory depression in spite of a high PEEP level.

Adult↗
PubMed2003

Alveolar pressure monitoring: an evaluation in a lung model and in patients with acute lung injury.

OBJECTIVES: We evaluated an algorithm for continuous on-line monitoring of alveolar pressure over time in a lung model with lower and upper inflection points and variable resistance ratios and in patients with acute lung injury. The algorithm is based on "static" pressure/volume curves obtained from tracheal pressure measurements under dynamic conditions. DESIGN AND SETTING: Experimental and clinical evaluation of algorithm in a university hospital laboratory and intensive care unit. PATIENTS: Ten patients undergoing postoperative respiratory therapy (feasibility of tracheal measurement) and ten patients with acute lung injury undergoing ventilator treatment (evaluation of algorithm). MEASUREMENTS AND RESULTS: Direct tracheal pressure measurements with a catheter inserted through the endotracheal tube. Comparison of measured alveolar and the dynostatic alveolar pressure vs. time in a lung model with changes in five ventilatory parameters. Examples of clinical monitoring are reported. In the model there was excellent agreement between alveolar pressures obtained by the algorithm, the dynostatic alveolar pressure, and measured alveolar pressure at all ventilator settings. For inspiratory/expiratory resistance ratios between 1:2.1-2.1:1, the dynostatic alveolar pressure was within +/-1.5 cm H(2)O of measured alveolar pressure. In patients the technique for direct tracheal pressure measurement using a catheter inserted through the endotracheal tube functioned satisfactorily with intermittent air flushes for cleansing. CONCLUSIONS: Using a thin tracheal pressure catheter inserted through the endotracheal tube alveolar pressure allows continuous bedside monitoring with ease and precision using the dynostatic algorithm. The method is unaffected by tube and connector geometry or by secretions.

Adolescent↗
PubMed2002

Dead-space reduction and tracheal pressure measurements using a coaxial inner tube in an endotracheal tube.

OBJECTIVE: To evaluate the effects on CO(2) washout of the coaxial double lumen tube (DLT) as compared to a standard endotracheal tube (ETT) and tracheal gas insufflation (TGI). Precision of tracheal pressure monitoring through the DLT and safety issues, including intrinsic PEEP (PEEPi) formation during DLT ventilation, were also evaluated. DESIGN: Lung model study. SETTING: University research laboratory. MEASUREMENTS AND RESULTS: CO(2) washout was analysed in a lung model by measuring single alveolar CO(2) concentration during DLT ventilation as compared to standard ETT ventilation, at different minute ventilation (6-14 l/min) and different CO(2)-output levels (180 ml/min, 240 ml/min, and 300 ml/min). At a CO(2) output level of 240 ml/min the CO(2) washout was also compared to tidal volume-adjusted continuous TGI and expiratory synchronised TGI. Precision of tracheal pressure monitoring and PEEPi formation during DLT ventilation was evaluated by comparing pressure in each limb above the tube to reference tracheal pressure, varying I:E ratios (1:2, 1:1, and 2:1), tidal volumes (300-700 ml), breathing frequencies (15-25), and compliance (20-50 ml/cmH(2)O). DLT ventilation had the same efficacy in removing CO(2) as continuous and expiratory synchronised TGI, reducing single alveolar CO(2) concentration by 9-21% compared to normal ventilation. Tracheal pressure could be measured through the DLT with high precision. There was only marginal formation of PEEPi at tidal volumes <or=600 ml, I:E ratio <or=1:1, and compliance <or=35 ml/cmH(2)O. CONCLUSIONS: The double lumen tube is as effective as tracheal gas insufflation in reducing CO(2) tension. Tracheal pressure and formation of PEEPi can be monitored with high precision without interrupting ventilation.

Calibration↗
PubMed2002

Clinical evaluation of a partial CO2 rebreathing technique for cardiac output monitoring in critically ill patients.

BACKGROUND: Monitoring central hemodynamics is essential in critically ill patients and less invasive techniques are needed. In this study, the clinical and technical performance of a new non-invasive cardiac output monitor (NICO) based on partial CO2 rebreathing technique and a modified Fick equation were evaluated. The various sources of possible errors in measurement of cardiac output (CO), carbon dioxide production (VCO2) and pulmonary shunt were also assessed. METHODS: Simultaneous measurements of CO with partial CO2 rebreathing technique (CO(nico)) and thermodilution (CO(td)) were performed in 15 patients during major surgery or in the ICU. Pulmonary shunt was estimated from this device and compared to values obtained by standard shunt formula. The accuracy of VCO2 measurements was assessed in a mechanical lung model. RESULTS: A good correlation was found between CO(nico) and CO(td) (r = 0.96, within-subject correlation r = 0.88) with a small underestimation of cardiac output by the NICO of 0.04 L/min, limits of agreement (+/- 2 SD) being - 1.68 and 1.76 L/min. In hemodynamic unstable patients the method closely tracked changes in CO. Pulmonary shunt was underestimated by approximately 11%-units compared to standard shunt calculations using arterial and mixed venous blood gases. We also observed an underestimation in VCO2 measurements. CONCLUSION: Clinical evaluation shows that partial CO2 rebreathing technique provides a useful and accurate non-invasive estimate of cardiac output. Although this technique cannot fully replace the pulmonary artery catheter, it may be used to monitor central hemodynamics in a large number of critically ill patients.

Adult↗
PubMed2001

[Liver transplantation--from experiment to routine care. Experiences from the first 500 liver transplantations in Gothenburg].

During a fifteen-year period, 500 liver transplantations have been performed at Sahlgrenska University Hospital in Göteborg. The results have improved, and factors influencing outcome are discussed. A one-year survival rate over 90% and a 5-year survival rate close to 80% can now be expected for most indications. Long-term complications as well as special problems occurring in different groups of recipients are discussed. New indications for liver transplantation such as liver metastasis of endocrine tumors are described. This article also describes our experience of in situ splitting and living-related liver transplantation as well as other innovations such as cavoportal hemitransposition and multivisceral transplantation.

Adult↗
PubMed2001

Continuous on-line measurements of respiratory system, lung and chest wall mechanics during mechanic ventilation.

OBJECTIVE: We present a concept of on-line, manoeuvre-free monitoring of respiratory mechanics during dynamic conditions, displaying calculated alveolar pressure/volume curves continuously and separating lung and chest wall mechanics. DESIGN: Prospective observational study. SETTING: Intensive care unit of a university hospital. PATIENTS: Ten ventilator-treated patients with acute lung injury. INTERVENTIONS: Different positive end-expiratory pressure (PEEP) and tidal volumes, low flow inflation. MEASUREMENTS AND RESULTS: Previously validated methods were used to present a single-value dynostatic compliance for the whole breath and a dynostatic volume-dependent initial, middle and final compliance within the breath. A high individual variation of respiratory mechanics was observed. Reproducibility of repeated measurements was satisfactory (coefficients of variations for dynostatic volume-dependent compliance: < or =9.2% for total respiratory system, < or =18% for lung). Volume-dependent compliance showed a statistically significant pattern of successively decreasing compliance from the initial segment through the middle and final parts within each breath at all respiratory settings. This pattern became more prominent with increasing PEEP and tidal volume, indicating a greater distension of alveoli. No lower inflection point (LIP) was seen in patients with respiratory rate 20/min and PEEP at 4 cmH2O. A trial with low flow inflation in four of the patients showed formation of a LIP in three of them and an upper inflection in one. CONCLUSIONS: The monitoring concept revealed a constant pattern of successively decreasing compliance within each breath, which became more prominent with increasing PEEP and tidal volume. The monitoring concept offers a simple and reliable method of monitoring respiratory mechanics during ongoing ventilator treatment.

Adult↗
PubMed2001

Warning! Suctioning. A lung model evaluation of closed suctioning systems.

BACKGROUND: Closed system suctioning, CSS, has been advocated to avoid alveolar collapse. However, ventilator manufacturers indicate that extreme negative pressure levels can be obtained during closed system suctioning, impeding the performance of the ventilator. METHODS: Suctioning with a 12 or 14 Fr catheter with a vacuum level of -50 kPa was either performed with an open technology or a CSS, where the catheter is introduced through a tight-fitting connection through the endotracheal tube, EYT. The lung model was ventilated with a Servo 900C or 300 ventilator with an I:E ratio of 1:2, 1:1 and 2:1 and extrinsic positive end-expiratory pressure (PEEP) at 0 or 10 cm H20. Respiratory volumes and alveolar pressure were measured at the lung model alveolus. RESULTS: The initial suctioning flow was >40 l/min with a 14 Fr catheter. When inserting the catheter through a no. 7 ETT, PEEP rose from 11 to 23 cm H2O during volume control ventilation with an I:E ratio 1:1. During suctioning the alveolar pressure fell to 10 cm H2O below the set PEEP level. CSS during pressure control ventilation had fewer effects. Low tidal volumes, inverse I:E ratio and secretions in the tube resulted in pressures down to -92 cm H2O. CONCLUSION: CSS should not be used in volume control ventilation due to risk of high intrinsic PEEP levels at insertion of the catheter and extreme negative pressures during suctioning. Pressure control ventilation produces less intrinsic PEEP effect. The continuous positive airway pressure (CPAP) mode offers the least intrinsic PEEP during insertion of the catheter and least sub-atmospheric pressure during suctioning.

Air Pressure↗
PubMed2001

Direct tracheal airway pressure measurements are essential for safe and accurate dynamic monitoring of respiratory mechanics. A laboratory study.

BACKGROUND: All monitoring of respiratory mechanics should depend on tracheal pressures (Trach-P) as endotracheal tube resistance (ETT-Res) will otherwise distort them. The aim of this study was to investigate factors that may vary ETT-Res, causing difficulties in ETT-Res estimation clinically, and to evaluate a method for direct Trach-P measurements to obviate these problems. METHODS: In a model we studied: 1) The influence on ETT-Res caused by different connectors and secretions; 2) Direct Trach-P measurements with a catheter (o.d. 2 mm, i.d. 0.9 mm) with either end or side hole, filled with either air or liquid, introduced through the ETT lumen and evaluated regarding response time and position. RESULTS: The pressure drop between trachea and Y-piece increased by 15% when respectively a swivel connector and a humidification device were connected to the ETT. When injecting 1 ml and 2 ml gel into the ETT lumen the inspiratory resistance increased 100% and 600% respectively. The response time of all catheters was < or = 12 ms. During constant flow in inspiratory and expiratory directions the pressure difference between an end hole catheter positioned from 2 cm above the ETT tip to 4 cm below and a reference pressure in the artificial trachea was less than 1.5 cmH2O. CONCLUSIONS: ETT connections and secretions cause a variance in resistance. Tracheal pressure can be measured with high precision with an air- or liquid-filled catheter. An end hole catheter placed within 2 cm above or below the ETT tip will give sufficiently precise measurements for clinical purposes.

Air Pressure↗
PubMed2001

Descending aortic blood flow and cardiac output: a clinical and experimental study of continuous oesophageal echo-Doppler flowmetry.

BACKGROUND: Several studies have demonstrated that perioperative optimisation of oxygen delivery and haemodynamics can reduce mortality and morbidity for high-risk surgical patients. To optimise cardiac output, reliable, continuous and "less invasive" methods for measuring cardiac output are urgently needed. METHODS: Eight landrace pigs were studied during experimental repeated cardiac tamponade and 14 patients during liver transplantation. Aortic blood flow was measured by using transoesophageal echo-Doppler technique. A total of 91 paired measurements of aortic blood flow and cardiac output with different techniques were performed in the pigs and 124 paired measurements in the patients. RESULTS: Transoesophageal echo-Doppler did provide continuous real-time monitoring of the rapid and dramatic haemodynamic changes occurring during cardiac tamponade and during liver transplantation, while only intermittent information was obtained from the bolus thermodilution technique. Changes in haemodynamics were more difficult to detect with the "continual" cardiac output thermodilution technique. Changes in aortic blood flow closely followed changes in cardiac output determined by the bolus thermodilution technique both in pigs (r= 0.89) and in patients (r=0.80). In patients, aortic blood flow constituted about 70% of cardiac output determined by the bolus thermodilution technique. CONCLUSIONS: A combined echo-Doppler technique can be valuable for continuous monitoring of haemodynamic changes in the perioperative setting, and changes in aortic blood flow agree well with corresponding changes in cardiac output intermittently obtained by thermodilution cardiac output measurements. With the combined echo-Doppler technique a proper position of the Doppler beam is greatly facilitated by the M-mode echo visualisation of the aortic wall and aortic cross-sectional area is continuously measured.

Adult↗
PubMed2001

Oxygen consumption in patients with hyperthyroidism before and after treatment with beta-blockade versus thyrostatic treatment: a prospective randomized study.

OBJECTIVE: To evaluate randomly the effect of thyrostatic treatment (tiamazole) versus selective (metoprolol) and nonselective beta-blockade (propranolol) on whole-body energy metabolism in women with hyperthyroidism. SUMMARY BACKGROUND DATA: beta-blockade is used as an alternative to thyrostatic drugs in the preoperative treatment of patients with hyperthyroidism. beta-blockers have well-established symptomatic effects, but in contrast to antithyroid drugs beta-blockade is thought to lack direct effects on the increased metabolism in hyperthyroidism. METHODS: Whole-body oxygen consumption and carbon dioxide production was measured in a semiopen canopy system with paramagnetic O2 and infrared CO2 sensors. A constant flow generator and the gas-dilution method for calculation of gas flow were used. Anabolic parameters were body weight, triceps skinfold, and arm muscle circumference. RESULTS: Tiamazole normalized oxygen consumption and induced signs of anabolism with improved nutritional state. Metroprolol did not affect oxygen consumption. Propranolol reduced elevated oxygen consumption by 54%. Body weight and other anthropometric assessments were stable after specific and nonspecific beta-blockade, which also led to symptomatic relief in approximately 90% of the patients. CONCLUSION: Tiamazole was the most effective drug to oppose the adverse effects of hyperthyroidism. Therefore, thyrostatic agents are recommended for preoperative treatments of patients with severe catabolic hyperthyroidism. Whenever beta-blockers are chosen for treatment of hyperthyroidism, propranolol (beta 1 + beta 2) has an advantage because it reduces the metabolic rate, whereas selective beta 1-blockade seemed to provide only symptomatic relief, related to the normalization of heart rate.

Adrenergic beta-Antagonists↗
PubMed2000

Evaluation of pressure/volume loops based on intratracheal pressure measurements during dynamic conditions.

BACKGROUND: The aim of this study was to evaluate and compare information about lung mechanics obtained by dynamic pressure/volume loops based on Y-piece and intratracheal airway pressure. METHODS: Airway pressure was measured simultaneously at the Y-piece and trachea. Flow/tidal volume was measured by sidestream spirometry at the Y-piece. The effect of an intraluminal catheter in the tube was evaluated in a lung model. Ten adults with acute lung injury and mechanical ventilation were studied. Measurements were performed during volume-(VC) and pressure-controlled (PC) ventilation at different ventilator settings. RESULTS: Lung model: There was a statistically significant difference (P<0.001) between trachea and Y-piece pressure/volume loop areas during both VC and PC ventilation. The ratio trachea area/Y-piece area decreased with increased endotracheal tube resistance (r=0.96). PATIENTS: The difference between trachea and Y-piece P/V-loops was statistically significant at all 21 ventilatory settings (P<0.05-0.001). The tracheal loop revealed clearly intrinsic PEEP and lowered compliance during overinflation, which was difficult or impossible to see in the Y-piece pressure/volume loop. CONCLUSION: By measuring airway pressure at the trachea the effect of endotracheal tube resistance during inspiration is excluded while it is included during expiration, yielding correct end-points of inspiration and expiration. This makes it possible to calculate accurately total compliance of the respiratory system during dynamic conditions. By monitoring of airway pressure in the trachea, respiratory mechanics can be assessed more accurately and ventilatory settings adjusted to attenuate ventilator induced lung injury.

Aged↗
PubMed2000

Anaesthesia, recovery and postoperative nausea and vomiting after breast surgery. A comparison between desflurane, sevoflurane and isoflurane anaesthesia.

BACKGROUND: Whereas induction and recovery will occur more rapidly with the new low soluble anaesthetics than with isoflurane, the quality of anaesthesia and recovery with special emphasis on postoperative nausea and vomiting (PONV) is not well known. METHODS: In an open (peroperatively), double-blinded (postoperatively), randomised controlled study, we assessed anaesthesia characteristics, recovery and 24 h PONV after breast surgery comparing isoflurane, desflurane and sevoflurane. RESULTS: There were no significant quality differences between the three agents during anaesthesia and recovery except for the incidence of PONV in the postanaesthesia care unit (PACU). The PONV rate (24 h in PACU and ward) was higher in the desflurane group (67%) than in the isoflurane group (22%), (P<0.01). The corresponding PONV rate for sevoflurane was 36%. CONCLUSION: The quality of anaesthesia, time to opening of eyes and influence on respiration was similar with all three anaesthetics. As the emergence from anaesthesia did not differ significantly between the three agents, the choice of agent could be based on PONV rate and price. Desflurane had a significantly higher 24 h PONV rate than isoflurane. Early PACU PONV rate was significantly (P<0.05) lower for the more soluble isoflurane (4%) than for the low soluble gases, desflurane and sevoflurane together (28%). The result of this study does not give a rationale for a transition to the new low soluble agents in breast cancer surgery.

Anesthesia Recovery Period↗
PubMed2000

Intestinal perfusion during pneumoperitoneum with carbon dioxide, nitrogen, and nitric oxide during laparoscopic surgery.

OBJECTIVE: To find out what effect insufflation pressure and type of gas have on intestinal perfusion during pneumoperitoneum. DESIGN: Randomized, controlled, prospective, experimental study. SETTING: University affiliated animal experimental laboratory, Sweden. ANIMALS: Fasted, anaesthetised, domestic pigs of both sexes operated on laparoscopically (n = 7, weight 26-31 kg). INTERVENTIONS: Insufflation of carbon dioxide (CO2), nitric oxide (NO), or nitrogen (N2) at intra-abdominal pressures of 0, 5, 10, 15 and 20 mm Hg. MAIN OUTCOME MEASURES: Cardiac output, portal blood flow, and jejunal mucosal perfusion. RESULTS: Cardiac output decreased during N2 and NO (15, 20 mm Hg) but not during CO2 insufflation because of an accompanying tachycardia. Portal flow decreased during insufflation with N2 and NO (15, 20 mm Hg) and CO2 (20 mm Hg). Jejunal perfusion was reduced during N2 and NO insufflation (5-20 mm Hg) but remained unchanged during CO2 insufflation (5-20 mm Hg). CONCLUSIONS: Insufflation with CO2 maintained jejunal mucosal perfusion, probably as a result of hypercarbia as N2 at equal pressures reduced mesenteric flow. The vasodilator NO provided no haemodynamic benefit.

Abdomen↗
PubMed2000

A new method for non-invasive, manoeuvre-free determination of "static" pressure-volume curves during dynamic/therapeutic mechanical ventilation.

BACKGROUND: Lung mechanics are usually measured using static or quasistatic methods, abandoning normal ventilatory treatment. We have developed a method to calculate the alveolar pressure during dynamic/therapeutic conditions, "the dynostatic pressure" (P(dyn)), using airway pressure (P) measured in the trachea and volume (V) and flow (V) at the Y-piece. METHODS: P(dyn) is calculated according to the formula P(dyn)= (P(insp) x V(exp)-P(exp) x V(insp))/(V(exp)-V(insp)), making the assumption that inspiratory and expiratory resistances are equal at isovolume. The method was evaluated in a lung model during dynamic conditions comparing measured alveolar pressure (P(alv)) and P(dyn) at equal and unequal inspiratory and expiratory resistances and P/V-curves obtained during static and dynamic conditions. The algorithm was then applied in patients with acute lung injury (ALI). RESULTS: When inspiratory and expiratory resistances were equal there was an excellent agreement between the P(dyn) and the P(alv), irrespective of ventilator settings, r(2)=0.995 (range 0.981-0.999). P(dyn) derived compliance was equal to static values. When the ratio between inspiratory and expiratory resistance was varied between 2.3:1 and 1:2.3 the r(2) was above 0.95 (range 0.952-0.996). Development of intrinsic PEEP and overdistension was easily revealed in patients, as shown by the dynostatic P/V-curve. CONCLUSION: The dynostatic method gives a breath-by-breath reflection of the interaction between ventilatory settings and lung mechanics in patients during ordinary ventilator treatment. It is only marginally affected by the moderate differences in inspiratory versus expiratory resistances present in patients with ALI.

Airway Resistance↗