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Biomedical subjects

C Frostell

Publications and source records attributed to C Frostell.

54 records · Page 3Linked to original sources
PubMed1990

Atelectasis causes gas exchange impairment in the anaesthetised horse.

The anatomical basis of gas exchange impairment in the anaesthetised horse was studied by computerised tomography (CT; three shetland ponies) and morphological analysis (one pony and three horses). By means of CT, densities were seen in dependent lung regions early during anaesthesia, both with spontaneous breathing and with mechanical ventilation. The densities remained for some time where they had initially been created when the animal was turned from dorsal to sternal recumbency. Deep insufflation of the lungs reduced the dense area. Gas exchange was impaired roughly in proportion to the dense area. On histological analysis, the densities were atelectatic and congested with blood. Gravimetry showed no more extravascular water per unit lung tissue in the atelectatic than in the 'normal' regions, and the blood content was increased only slightly. It is concluded that the horse develops atelectasis in dependent lung regions early during anaesthesia in dorsal recumbency, and that atelectasis is the most likely explanation for the large shunt and impaired arterial oxygenation regularly seen during anaesthesia.

Anesthesia↗
PubMed1989

Knowledge base design for decision support in respirator therapy.

A knowledge base is built for decision support applied to respirator therapy (the KUSIVAR project). The knowledge representation is object-oriented using frames to store multiple forms of knowledge: variable descriptions, transformation tables, rules and mathematical models. The system is data-driven, generating and displaying advice automatically triggered by changes in data from the respirator and the patient. The inferenceing mechanism is forward-chaining i.e. a rule is evaluated as soon as it's condition is satisfied. Temporal aspects of the reasoning are represented by a number of mechanisms, among others limited validity times for data, trend analysis and mathematical models. The knowledge base is organized according to disease groups and decision situation which simplifies knowledge acquisition and improves response times since it enables the system to focus on a limited set of rules in each situation. To test the feasibility of the system design a prototype has been built using Knowledge Engineering Environment (KEE) from Intellicorp on an Explorer workstation from Unisys. The production system, which is interfaced to a Siemens Elema Servo Ventilator 900C, is currently being implemented under the Microsoft Windows multitasking environment on a microcomputer based on an Intel 80386 processor.

Decision Support Techniques↗
PubMed1989

Voluntary relaxation of the external anal sphincter.

In this study five volunteers with special training in anal sphincter exercise (Scandinavian Yoga School) managed voluntarily to reduce anal pressure. The mean reduction of anal pressure was 20 mm Hg. In one of the subjects, this was shown by manometry during low spinal anesthesia and electromyography to be caused by relaxation of the external anal sphincter.

Anal Canal↗
PubMed1989

A knowledge-based support system for mechanical ventilation of the lungs. The KUSIVAR concept and prototype.

The KUSIVAR is an expert system for mechanical ventilation of adult patients suffering from respiratory insufficiency. Its main objective is to provide guidance in respirator management. The knowledge base includes both qualitative, rule-based knowledge and quantitative knowledge expressed in the form of mathematical models (expert control) which is used for prediction of arterial gas tensions and optimization purposes. The system is data driven and uses a forward chaining mechanism for rule invocation. The interaction with the user will be performed in advisory, critiquing, semi-automatic and automatic modes. The system is at present in an advanced prototype stage. Prototyping is performed using KEE (Knowledge Engineering Environment) on a Sperry Explorer workstation. For further development and clinical use the expert system will be downloaded to an advanced PC. The system is intended to support therapy with a Siemens-Elema Servoventilator 900 C.

Adult↗
PubMed1989

Pulmonary densities during anaesthesia. An experimental study on lung morphology and gas exchange.

The nature of dense areas in dependent lung regions regularly seen in anaesthetized humans was examined in a sheep model. During anaesthesia with muscle paralysis and mechanical ventilation dense areas in dependent lung regions could be seen by means of computerized tomography (CT). They had the same location and the same attenuation as in anaesthetized humans. Gas exchange impairment tended to increase in proportion to the size of the dense area on the CT scan. Microscopy showed that the densities in the sheep were atelectatic lung regions, with no or little interstitial oedema and only minor vascular congestion. The atelectatic lung tissue was sharply demarcated and the lung tissue in the immediate vicinity was well aerated, or even hyperinflated. Gravimetry showed the same amount of extravascular fluid and blood per unit lung weight in the atelectatic lung and in the aerated lung region. It is concluded that the densities appearing in dependent lung regions during anaesthesia are caused by atelectasis.

Anesthesia↗
PubMed1989

[Chronic respiratory insufficiency--a death sentence?].

Chronic respiratory deficiency is a complication in a number of diseases and results in poor quality of life and increased mortality. Notwithstanding that the long-term prognosis is poor the patient should be offered respiratory support via a nasal mask or a tracheotomy tube; this issue was discussed at an international meeting on ventilation at home held in Lyons in France.

Adolescent↗
PubMed1987

Selective mechanical ventilation of dependent lung regions in the anaesthetized horse in dorsal recumbency.

The effect of selective mechanical ventilation of dependent lung regions were studied in anaesthetized horses (mean weight 486 kg) in dorsal recumbency. Blood-gas measurements were performed with the horse in the lateral position during spontaneous breathing (before selective intubation) and in dorsal recumbency during spontaneous breathing, general mechanical ventilation, and spontaneous breathing + selective mechanical ventilation. Arterial oxygen tension (PaO2) was 32.3 kPa in the lateral position during spontaneous breathing with a high inspired oxygen fraction (FlO2 greater than 92%). In dorsal recumbency PaO2 decreased to 10.9 kPa during spontaneous breathing and was not significantly affected by general mechanical ventilation (PaO2 12.6 kPa). The institution of selective mechanical ventilation with a selective positive end-expiratory pressure (PEEP) of 20 cm H2O caused a marked increase in PaO2 to an average of 35.3 kPa. It is concluded that selective intubation of dependent regions in the diaphragmatic lobes is a feasible procedure and that selective mechanical ventilation with PEEP markedly improves arterial oxygenation in the anaesthetized horse in dorsal recumbency.

Anesthesia, General↗
PubMed1987

Thoracic and abdominal lymph drainage in relation to mechanical ventilation and PEEP.

Thoracic and abdominal lymph flow have been studied in 25 dogs. Thoracic lymph flow (TLF) was found to be (mean +/- s.e. mean) 6.1 +/- 1.4 ml/h before, and 29 +/- 4.6 ml/h after the induction of lung damage with oleic acid. TLF was depressed by 50% both before and after lung damage, when a positive end-expiratory pressure (PEEP) of 1.0 kPa (10 cmH2O) was applied. This suggests impeded drainage of the lung tissue. Spontaneous breathing, compared to mechanical ventilation, significantly increased TLF by approximately 70%. Abdominal lymph flow increased from 61 +/- 5.3 ml/h to 111 +/- 12.6 ml/h, when a PEEP of 1.0 kPa was applied. These findings demonstrate that PEEP may contribute to oedema in a surgical area. It is concluded that increased intrathoracic pressure reduces TLF, and spontaneous breathing increases TLF, as compared to mechanical ventilation without PEEP.

Abdomen↗
PubMed1987

Effects of PEEP on extravascular lung water and central blood volume in the dog.

Twenty-four mongrel dogs were anaesthetized and ventilated mechanically in the supine position. Extravascular lung water (EVLW) and central blood volume (CBV) were measured with a double indicator (dye/cold) dilution technique. Both indicators were detected intravascularly in the aortic root with a fibreoptic thermistor catheter. Seven dogs ventilated with a positive end-expiratory pressure (PEEP) of 1.0 kPa (10 cmH2O) for a short period of time (less than 20 min) displayed no significant change in EVLW as measured with the indicator dilution technique (= EVLWi), while reductions were seen in both CBV (15%, P less than 0.01) and cardiac output (CO-thermodilution technique) (10%, P less than 0.05). Another seven dogs ventilated with a PEEP of 1.0 kPa for 8 h showed a gradual increase in EVLWi. After 8 h, a mean increase of 34% (P less than 0.01) was recorded, and the increase was also verified by post-mortem gravimetric determination of EVLW (= EVLWg), displaying an increase of 61% (P less than 0.01). In five dogs ventilated with zero end-expiratory pressure (ZEEP) for 8 h, no changes in EVLWi, CO, and CBV were observed, and EVLWg was mean 4.39 g/kg body weight (BW). Five additional dogs were sacrificed after 15 min of anaesthesia without catheterization and EVLWg was found to be 4.24 g/kg BW. It is concluded that EVLWi does not change measurably during ZEEP or short periods of PEEP. However, long periods (8 h) of PEEP result in elevated EVLWi values. Gravimetry supports these conclusions.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

Effects of prolonged surgical trauma on the extravascular lung water and central blood volume in the dog.

Extravascular lung water (EVLW) and central blood volume (CBV) were measured in 13 dogs with a double-indicator dilution technique (dye-cold), the indicators being detected intravascularly. Animals in a control group (n = 5) were mechanically ventilated for 8-15 h after baseline measurements. Another group of animals (n = 8) were subjected to extensive lymph duct cannulations, including a thoracoabdominal incision, and the dogs were followed for 8 to 18 h postoperatively. All dogs (n = 13) then received a dose of oleic acid intravenously in order to create lung damage. A positive fluid balance was maintained throughout the experiment. Basal EVLW was 8.8 ml/kg (n = 13) (similar in both groups), and did not change significantly in either group before oleic acid. Basal CBV was 18.5 ml/kg (n = 13); it increased (P less than 0.05) in the control group and decreased (P less than 0.05) in the surgery group during a 8-15-h period. EVLW was doubled (P less than 0.001) and CBV decreased slightly 2 h after oleic acid administration. The lung damage was similar in both groups, and was accompanied by increased pulmonary vascular pressures and marked reductions in arterial oxygen tension and thoracic compliance. The findings suggest that an earlier proposed dog model for the simultaneous measurement of EVLW and lymph flow can be used in long-term studies on lung fluid balance.

Anesthesia↗
PubMed1986

An experimental model for the separate sampling of thoracic and abdominal lymph.

A new animal model for the selective sampling of both the thoracic and the abdominal lymph is presented. Separation of the abdominal from the thoracic lymph flow provides new information on pulmonary physiology during mechanical ventilation and is a prerequisite for studies on pulmonary lymph flow. This is underscored by the observation that the abdominal contribution to the total lymph flow in the neck is more than 90%.

Abdomen↗
PubMed1986

Separate thoracic and abdominal lymph flow in the dog.

We present results from an improved dog model, in which lymph flows from the thorax and abdomen are separated. The effect of increased alveolar pressure on lymph flows was studied by the application of positive end expiratory pressure (PEEP). Mean (+/- SD) thoracic lymph flow in 10 dogs was 4.1 ml/h (+/- 2.9) before, and 27.0 ml/h (+/- 17) after the induction of lung damage with oleic acid. Thoracic lymph flow was depressed by 50% with the application of a PEEP of 1.0 kPa (10 cm H2O), both before and after lung damage, thus impeding the drainage of the lung tissue. Abdominal lymph flow increased from 57 +/- 29 ml/h to 111 +/- 65 ml/h with the application of a PEEP of 1.0 kPa. These simulated events in a surgical area demonstrate the risk of causing excessive edema with PEEP. We conclude that if the application of PEEP in a clinical situation is necessary then the additional risk factors (increased extravascular lung water, increased edema in surgical areas) that have been presented should be taken into consideration.

Abdomen↗
PubMed1984

Differential ventilation with selective PEEP in bilateral lung disease.

A patient with severe, acute respiratory failure (ARF) due to bilateral lung disease has been treated with a new ventilation concept aimed at improving the vertical match of ventilation and perfusion. The patient suffered from severe hypoxemia in spite of artificial ventilation with high PEEP and high inspired oxygen fraction. He was intubated with a double lumen bronchial catheter and placed in the lateral decubital posture, whereafter each lung was ventilated in accordance with its assumed perfusion, and selective PEEP of 10-15 cm H2O to the dependent and 0-5 cm H2O to the non-dependent lung was applied. Differential ventilation with selective PEEP resulted in a substantial improvement in pulmonary gas exchange in two separate periods of 3-4 days. The technique thus proved to be efficient and also clinically feasible in a standard intensive care unit.

Aged↗
PubMed1984

Practical aspects of differential ventilation with selective peep in acute respiratory failure.

Hypoxaemia in association with acute respiratory failure continues to be a severe problem in some intensive care patients. Among strategies proposed, we want to focus attention on differential ventilation with selective PEEP, administered in the lateral position. This ventilation technique has proved successful in the treatment of refractory hypoxaemia due to severe bilateral lung disease. The rationale of this concept is briefly presented in this paper, where the main emphasis is laid on the practical aspects of its clinical application. Two case reports are included as examples of our experiences.

Acute Disease↗
PubMed1983

Effects of high-frequency breathing on pulmonary ventilation and gas exchange.

The effects of spontaneous high-frequency breathing (HFB) on lung function were evaluated in three subjects highly trained in the practice of yoga. Transpulmonary pressure was measured by an esophageal balloon catheter and gas flow by pneumotachography. The abdominal and rib cage contributions to tidal breathing were measured separately by respiratory inductive plethysmography. Gas exchange was studied by the conventional technique and by multiple inert gas elimination. During HFB, respiratory rate increased to 232 cycles/min with a tidal volume of 0.35 liter. This resulted in a more than 10-fold increase in expired minute ventilation to approximately 90 1/min. The transpulmonary pressure varied by 20 cmH2O, with the calculated elastic, resistive, and accelerative components varying by 2, 20, and 8 cmH2O, respectively. Respiratory work increased more than 200-fold in comparison with resting ventilation. A phase shift between thoracic and abdominal breathing was observed and was interpreted as a volume displacement of approximately 30 1/min between the two parts of the respiratory system. Arterial oxygen and carbon dioxide tension remained normal. Bohr dead space increased, while acetone dead space remained unaltered. A bimodal distribution of ventilation-perfusion ratios (VA/Q) was observed, with one mode in normal and another in "high" VA/Q regions.

Adult↗
PubMedDate not supplied

Kave: a tool for knowledge acquisition to support artificial ventilation.

A decision support system for artificial ventilation is being developed. One of the fundamental goals for this system is the application of the system when a domain expert is not present. Such a system requires a rich knowledge base. The knowledge acquisition process is often considered to be the bottleneck in acquiring such a complete knowledge base. Since no single available method, for example interviewing domain experts, is sufficient for removing this bottleneck, we have chosen a combination of different methods. The different backgrounds of knowledge engineers and domain experts could cause communication restrictions and difficulties between them, e.g. they might not understand each others knowledge domain and this will affect formulation of the knowledge. To solve this problem we needed a tool which supports both the knowledge engineer and the domain expert already from the initial phase of developing the knowledge base. We have developed a knowledge acquisition system called KAVE to elicit knowledge from domain experts and storing it in the knowledge base. KAVE is based on a domain specific conceptual model which is a result of cooperation between knowledge engineers and domain experts during identification, design and structuring of knowledge for this domain. KAVE includes a patient simulator to help validate knowledge in the knowledge base and a knowledge editor to facilitate refinement and maintenance of the knowledge base.

Artificial Intelligence↗
PubMedDate not supplied

Differential ventilation in acute respiratory failure. Indications and outcome.

Acute respiratory failure (ARF) is a life-threatening condition which frequently requires ventilatory support. Many patients die of hypoxaemia despite a high inspired oxygen concentration and application of general positive end-expiratory pressure (PEEP). Differential ventilation has been used in selected patients with unilateral lung disease or with large inequalities in pathology between the two lungs. An important contributor to the hypoxaemia is a vertical inequality in the ventilation-perfusion (V/Q) matching. This can be compensated for by placing the patient in the lateral position, ventilating each lung separately in proportion to its assumed blood flow, and applying PEEP selectively to the dependent lung to counteract airway closure and alveolar collapse and thus improve the gas distribution within that lung. This ventilatory regime should promote V/Q matching better than general PEEP, and will not impede cardiac output. Major improvement in gas exchange has been achieved in short-term experiments and in prolonged ventilator treatment of patients with ARF.

Acute Disease↗