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J Räsänen

Publications and source records attributed to J Räsänen.

At least 19 recordsLinked to original sources
PubMed2006

Genome-controlled reverse transcriptase-polymerase chain reaction for targeted gene-expression analysis.

OBJECTIVE: Although gene-expression profiling has an important part to play in the classification of tumours and premalignant conditions, reproducibility of the present polymerase chain reaction (PCR)-based quantitative techniques needs to be improved for diagnostic purposes and to enable analysis of gene expression in formalin-fixed paraffin-embedded (FFPE) tissue samples. We have developed reverse transcriptase-PCR-based technology for quantitative assessment of the relative content of multiple mRNA transcripts in small tissue or cell samples. MATERIAL AND METHODS: A multiplexed sequence modifying cDNA synthesis reaction is performed with this technique to create a 4-5 degrees increase in the melting temperature of subsequent short (56-64 bp) PCR amplicons. Each cDNA template is competitively co-amplified with genomic DNA, which serves as a universal internal standard. The relative amounts of cDNA and genomic DNA-derived amplicons are quantified in-tube by homogeneous melting curve analysis. RESULTS: The dynamic range of the assay was three orders of magnitude, while the detection limit was 100 cDNA molecules. A prototype assay, consisting of the analysis of eight genes, displayed good reproducibility (inter-assay CV 5-20 %) compared to the TaqMan assay (inter-assay CV 7-43 %). Gene-expression analysis could be performed in 20 of 20 (100 %) archival frozen samples, in 30 of 35 (86 %) archival FFPE samples and in 26 of 27 (96 %) endoscopic biopsies. CONCLUSIONS: We demonstrate that this new technique enables accurate analysis of mRNA expression in cultured cells and endoscopic tissue biopsies. Sensitive analysis FFPE tissue is also possible thanks to the short PCR amplicons.

Biopsy↗
PubMed2005

Ephedrine and phenylephrine for the treatment of maternal hypotension in a chronic sheep model of increased placental vascular resistance.

BACKGROUND: We hypothesized that ephedrine and phenylephrine are equal with respect to uterine and placental haemodynamics and fetal acid-base status after exposure to maternal hypoxaemia and hypotension in a chronic sheep model of increased placental vascular resistance (R(UA)). METHODS: At 114-135 days gestation, chronically instrumented fetal sheep underwent placental embolization leading to increased R(UA). Twenty-four hours after embolization, the ewes were anaesthetized and randomized to receive boluses of ephedrine (n=7) or phenylephrine (n=6) for epidural-induced hypotension after maternal hypoxaemia. Uterine (Q(UtA)) and placental (Q(UA)) volume blood flows and uterine vascular resistance (R(UtA)) and R(UA) were recorded. Uterine (PI(UtA)) and umbilical artery (PI(UA)) pulsatility indices were obtained by Doppler ultrasonography. Fetal arterial blood samples were analysed for acid-base values and lactate concentrations. RESULTS: During hypotension, Q(UtA), fetal pH, BE, and Po(2) decreased whereas R(UtA), PI(UtA), R(UA), and fetal lactate concentration increased. With ephedrine, Q(UtA), R(UtA), PI(UtA), R(UA), and fetal Po(2) returned to baseline. Fetal pH, BE, and lactate concentration did not change from hypotensive values. With phenylephrine, Q(UtA) remained lower (P=0.007) and R(UtA) (P=0.007), PI(UtA) (P=0.013), and R(UA) (P=0.050) higher than at baseline. Fetal Po(2) returned to baseline and fetal pH and BE did not change from hypotensive values. However, fetal lactate concentration increased further (mean difference 1.49, 95% confidence interval 0.72-2.26 mmol litre(-1); P=0.004). CONCLUSIONS: In a chronic sheep model of increased placental vascular resistance, compared with ephedrine administration, phenylephrine administration was associated with impaired uterine and placental haemodynamics and increased fetal lactate concentrations.

Anesthesia, Epidural↗
PubMed2005

Low-dose aspirin does not improve ovarian responsiveness or pregnancy rate in IVF and ICSI patients: a randomized, placebo-controlled double-blind study.

BACKGROUND: Poor ovarian and endometrial responses to gonadotrophin stimulation in assisted reproduction techniques lead to decreased pregnancy rates. The aim of the present study was to test the hypothesis that low-dose aspirin started prior to controlled ovarian stimulation improves ovarian responsiveness, pregnancy rate (PR) and pregnancy outcome. METHODS: A total of 374 women who were to undergo IVF/ICSI were randomized to receive 100 mg of aspirin (n=186) or placebo (n=188) daily. Treatment was started on the first day of controlled ovarian stimulation. It was continued until menstruation or a negative pregnancy test. Pregnant women continued the medication until delivery. The main outcome measures were the number of oocytes, number and quality of embryos, the clinical PR and pregnancy outcome. RESULTS: The mean (+/-SD) number of oocytes (12.0+/-7.0 versus 12.7+/-7.2), the total mean number of embryos (5.82+/-4.35 versus 5.99+/-4.66), the mean number of top quality embryos (0.99+/-1.39 versus 1.18+/-1.51) and the number of embryos transferred (1.64+/-0.64 versus 1.63+/-0.71) did not differ in the aspirin and placebo groups. Between the aspirin and placebo group, there was no statistically significant difference in clinical PR per embryo transfer (25.3%, n=44 out of 174 versus 27.4%, n=48 out of 175) or clinical PR per cycle initiated (23.7% versus 25.5%). Birth rate per embryo transfer did not differ significantly between the aspirin (18.4%) and placebo (21.1%) groups. The incidence of poor responders [12 (6.5%) versus 13 (6.9%)] was similar in both groups. CONCLUSIONS: The present results indicate that low-dose aspirin treatment does not have any beneficial effect on ovarian responsiveness, PR and pregnancy outcome in unselected women undergoing IVF/ICSI.

Adult↗
PubMed2005

Human fetal cardiac function during the first trimester of pregnancy.

OBJECTIVE: To investigate first trimester human fetal cardiac function in relation to cardiac volume blood flow, and peripheral arterial and venous blood flow patterns. METHODS: Transvaginal Doppler ultrasonography was performed in 16 uncomplicated pregnancies at 6+, 7+, 8+, 9+, and 10+ gestational weeks. The shape of the inflow waveform and the presence of atrioventricular valve regurgitation (AVVR) were noted. The outflow mean velocity (Vmean) was calculated. The proportions of the isovolumetric relaxation (IRT%) and contraction times (ICT%) of the cardiac cycle were defined. Ductus venosus and umbilical artery pulsatility indices (PI) were obtained. RESULTS: Every inflow waveform was monophasic before 9+ weeks. At 9+ weeks 11 of 16 and at 10+ weeks all waveforms were biphasic. At 7+ and 8+ weeks AVVR was documented in one case. At 9+ and 10+ weeks AVVR was present in four and seven fetuses, respectively. Mean (SD) outflow Vmean increased between 6+ and 8+ weeks from 3.6 (1.5) to 8.4 (3.0) cm/s (p < 0.05). IRT% decreased significantly from 6+ to 7+ weeks (39.8 (2.6) to 19.2 (6.2), p < 0.001). ICT% decreased between 8+ and 9+ weeks from 13.2 (4.0) to 8.5 (2.5) (p < 0.05). Ductus venosus PIs were unchanged. Umbilical artery Vmean increased between 7+ and 10+ weeks from 1.59 (0.51) to 5.06 (1.06) cm/s (p < 0.001) and PIs remained unchanged. CONCLUSIONS: The first trimester of pregnancy is characterised by significant improvements in cardiac diastolic and systolic function with a concomitant increase in cardiac volume blood flow. At 10+ weeks AVVR is a common finding. Placental volume blood flow increases significantly with no change in the placental vascular impedance.

Blood Flow Velocity↗
PubMed2004

Effects of ephedrine and phenylephrine on uterine and placental circulations and fetal outcome following fetal hypoxaemia and epidural-induced hypotension in a sheep model.

BACKGROUND: Recent studies support the use of alpha-agonists during regional anaesthesia in uncomplicated term pregnancies. We hypothesized that ephedrine and phenylephrine, administered for maternal hypotension following fetal hypoxaemia, are equal in respect of fetal outcome. METHODS: At 117-132 days gestation, chronically instrumented, anaesthetized and mechanically ventilated ewes were randomized to receive boluses of ephedrine (n=9) or phenylephrine (n=8) for maternal epidural-induced hypotension after a period of fetal hypoxaemia. Uterine (QUtA) and placental (QUA) volume blood flows were measured with perivascular transit-time ultrasonic flow probes, and uterine (RUtA) and placental (RUA) vascular resistances were computed from volume blood flows and maternal and fetal mean arterial pressures. Uterine (PIUtA) and umbilical artery (PIUA) pulsatility indices were obtained by Doppler ultrasonography. RESULTS: Ephedrine increased QUtA and decreased RUtA and PIUtA from a hypotensive to baseline level and had no significant effect on umbilical circulation. With phenylephrine, QUtA remained lower (P=0.011) and RUtA higher (P=0.043) than at baseline, although PIUtA decreased to baseline level. PIUA increased from baseline with phenylephrine (P=0.007), whereas QUA decreased (P=0.050). Maternal volume expansion with hydroxyethyl starch decreased RUtA significantly irrespective of the vasopressor used. There were no significant differences in fetal blood gas values or lactate concentrations between the ephedrine and phenylephrine groups. CONCLUSIONS: Despite the more favourable effects on uterine and placental circulations of ephedrine over phenylephrine, no significant differences in fetal acid-base status or lactate concentrations were observed.

Acid-Base Equilibrium↗
PubMed2003

Retrograde aortic isthmus net blood flow and human fetal cardiac function in placental insufficiency.

OBJECTIVE: Retrograde aortic isthmus (AoI) net blood flow has been associated with diminished oxygen delivery to cerebral circulation. This study was designed to characterize the cardiac function in human fetuses with retrograde AoI net blood flow in pregnancies complicated by placental insufficiency. METHODS: The control group comprised 43 fetuses in uncomplicated pregnancies. Study groups consisted of fetuses with placental insufficiency, and either antegrade (Group 1; n = 18) or retrograde (Group 2; n = 11) AoI net blood flow. Volume blood flows (Q) of left (LVCO) and right (RVCO) ventricles, ductus arteriosus (Q(DA)), pulmonary arterial bed (Q(P)) and foramen ovale (Q(FO)) were calculated and their proportions (%) of combined cardiac output (CCO) were determined. Ventricular ejection forces were calculated. Blood velocity waveforms of the mitral (MV) and tricuspid (TV) valves were obtained. The proportion of left ventricular isovolumetric relaxation time (IRT%) of the cardiac cycle, and index of myocardial performance (IMP) were calculated. RESULTS: In Group 1, Q(DA)% was increased (P < 0.05) and Q(P)% decreased (P < 0.05) compared with the control group, and Q(FO)% was greater (P < 0.01) compared with the control group and Group 2. In Group 2, the distribution of CCO did not differ from that of the control group. Ventricular ejection forces were similar among the groups. In Group 2, the MV early filling/atrial contraction time-velocity integral ratio was greater (P < 0.05) compared with those of the control group and Group 1. In Groups 1 and 2, IRT% and IMP were increased (P < 0.001) compared with the control group. CONCLUSIONS: In placental insufficiency, fetuses with antegrade AoI net blood flow show a shift in RVCO from the pulmonary to the systemic circulation, and Q(FO) makes up the majority of LVCO. Fetuses with retrograde AoI net blood flow fail to demonstrate these changes, suggesting a relative drop in the oxygen content of the blood entering the left ventricle.

Aorta, Thoracic↗
PubMed2002

Retrograde net blood flow in the aortic isthmus in relation to human fetal arterial and venous circulations.

OBJECTIVES: To characterize changes in the human fetal arterial and venous circulations associated with retrograde aortic isthmus net blood flow. METHODS: Study groups consisted of fetuses with placental insufficiency and/or fetal growth restriction and either antegrade (Group 1; n = 18) or retrograde (Group 2; n = 11) net blood flow in the aortic isthmus. The control group comprised 31 fetuses in uncomplicated pregnancies. Pulsatility indices of the umbilical, middle cerebral and proximal pulmonary arteries and the descending aorta, and pulsatility indices for veins of the ductus venosus and inferior vena cava were calculated. Right and left ventricular fractional shortenings were ascertained. The coronary artery blood flow was visualized and the presence of tricuspid regurgitation was noted. RESULTS: In the study groups, the umbilical artery and descending aorta pulsatility indices were significantly higher (P < 0.05), and those of the middle cerebral artery lower (P < 0.001), than in the control group, with no difference between the two study groups. The proximal pulmonary artery pulsatility index was significantly higher in Group 2 (P < 0.001) than in Group 1 and the control group. In Group 2, the right ventricular fractional shortening was significantly lower (P < 0.01) than in Group 1. Coronary artery blood flow was visualized significantly more often (P < 0.03) and tricuspid regurgitation was present more frequently (P < 0.003) in Group 2 than in Group 1. In Group 2, the ductus venosus pulsatility index for veins was significantly higher than in Group 1 (P < 0.01) and the control group (P < 0.01), with no difference in the inferior vena cava pulsatility index for veins. CONCLUSIONS: Fetuses with retrograde aortic isthmus net blood flow demonstrate a rise in right ventricular afterload and increased pulsatility in ductus venosus blood velocity waveforms.

Aorta↗
PubMed2001

Umbilical artery N-terminal peptide of proatrial natriuretic peptide in hypertensive pregnancies and fetal acidemia during labor.

OBJECTIVE: To assess the activity of the human fetal atrial natriuretic peptide system in hypertensive pregnancies with and without signs of increased fetal systemic venous pressure and in pregnancies complicated by fetal acidemia during labor. METHODS: Umbilical artery plasma N-terminal peptide of proatrial natriuretic peptide concentrations were measured in neonates by radioimmunoassay. The control group consisted of 50 neonates with uncomplicated gestation and labor. In group 1, there were 22 newborns of hypertensive pregnancies. Doppler ultrasonography showed abnormal umbilical artery blood velocity waveform in five cases and normal nonpulsatile umbilical vein blood velocity profile in every case. Group 2 consisted of five newborns of pregnancies complicated by maternal hypertensive disorder. Atrial pulsations in the umbilical vein and retrograde diastolic blood velocity pattern in the umbilical artery were detected in every case. Group 3 was composed of 27 newborns of uncomplicated pregnancies with fetal acidemia (pH 7.10 or less) during labor. RESULTS: In groups 1-3, N-terminal peptide of proatrial natriuretic peptide concentrations were higher (P <.001) than in the control group. In group 1, neonates with abnormal umbilical artery blood velocity pattern had higher N-terminal peptide of proatrial natriuretic peptide concentrations than neonates with normal umbilical artery Doppler findings (P <.006). N-terminal peptide of proatrial natriuretic peptide concentrations were higher in group 2 (P <.002) than in groups 1 and 3. CONCLUSIONS Maternal hypertensive disorder and fetal acidemia during labor stimulate fetal atrial natriuretic peptide production, which was greatest in fetuses with severe placental insufficiency and signs of congestive heart failure.

Adult↗
PubMed2001

Perioperative determinants and outcome of cardiopulmonary arrest in children after heart surgery.

OBJECTIVES: To identify perioperative factors associated with postoperative cardiopulmonary arrest (CA) in the pediatric intensive care unit (PICU) in children undergoing cardiovascular surgery, and to report the outcome of cardiopulmonary resuscitation (CPR) in these patients. METHODS: We reviewed the medical records of all patients under 16 years of age who had undergone cardiovascular surgery and sustained CA in PICU in an urban, tertiary care children's hospital over a 5-year period. We used two control groups of patients who recovered without CA. (1) Sixty-five patients, who were operated under deep hypothermic circulatory arrest (DHCA) during the study period. (2) All patients who underwent repair of congenital heart lesions without DHCA in 1994 (n=278). RESULTS: Eighty-two children experienced CA during postoperative care in PICU, mainly from cardiovascular causes. Thirty-four (41%) were declared dead without attempted resuscitation, CPR was initiated in 48 (59%). The primary survival rate was 56% and 1 year survival rate was 19%. The incidence of CA was 3.6% for closed heart operations, 4.9% for intra-cardiac surgery without DHCA, and 27% for operations involving DHCA. Thirty-three per cent of patients with CA arrested during the first 24 postoperative h. Preoperative mechanical ventilation (P=0.03), prostaglandin E1 (P=0.001) and inotropic support (P=0.04) were given significantly more frequently to patients who postoperatively required CPR, compared to control groups. Patients in whom CPR was attempted were younger than the 1994 controls (0.4 vs. 1.2 years; P<0.04), had longer mean aortic-cross-clamp times (76 vs. 51 min; P<0.0001) and cardiopulmonary bypass times (124 vs. 85 min; P<0.0002), and required more inotropic support upon leaving the operating room (P<0.0001). Patients who received CPR had significantly longer DHCA times (53 vs. 32 min; P<0.0002) and required more inotropic support than patients in the DHCA control group (P<0.002). CONCLUSIONS: CA after pediatric cardiac surgery is associated with repair of complex congenital heart anomalies in patients who require preoperative mechanical ventilation and vasoactive agents, prolonged aortic cross-clamp, circulatory arrest; and heavy postoperative inotropic support.

Cardiac Surgical Procedures↗
PubMed2000

Utstein style reporting of in-hospital paediatric cardiopulmonary resuscitation.

STUDY OBJECTIVE: To report paediatric in-hospital cardiac arrest data according to Utstein style and to determine the effectiveness of cardiopulmonary resuscitation (CPR) in hospitalized children. DESIGN: Retrospective 5-year case series. SETTING: Urban, tertiary-care children's hospital. PARTICIPANTS: All patients who sustained cardiopulmonary arrest. RESULTS: Altogether 227 patients experienced a cardiopulmonary arrest during the study period, 109 (48.0%) were declared dead without attempted resuscitation, and CPR was initiated in 118 (52.0%). The incidence of cardiac arrest was 0. 7% of all hospital admissions and 5.5% of PICU admissions; the incidence of CPR attempts was 0.4 and 2.5%, respectively. Most of the CPR attempts (64.4%) took place in the PICU and the most frequent aetiology was cardiovascular (71.2%). The 1-year survival rate was 17.8%. Short duration of external CPR was the best prognostic factor associated with survival. With few exceptions, the Paediatric Utstein Style was found to be applicable for reporting retrospective data from in-hospital cardiac arrests in children. CONCLUSIONS: In-hospital cardiopulmonary resuscitation was shown to be an uncommon event in children; the survival rate was similar to earlier studies.

Adolescent↗
PubMed2000

Pharmacokinetics of amrinone in neonates and infants.

OBJECTIVE: To evaluate the pharmacokinetics of amrinone and its metabolites in neonates and infants after reconstructive surgery for congenital heart disease. DESIGN: Prospective study. SETTING: Pediatric intensive care unit in a university hospital. PARTICIPANTS: Fifteen neonates aged less than 1 month with transposition of the great arteries and 14 infants aged 2 to 6 months with complete atrioventricular septal defect. INTERVENTIONS: Amrinone, loading dose of 2 mg/kg, was administered before weaning from cardiopulmonary bypass, followed by a maintenance infusion of 7.5 microg/kg/min. MEASUREMENTS AND MAIN RESULTS: Blood samples to determine plasma concentrations of amrinone, N-acetylamrinone, and N-glycolylamrinone were drawn before amrinone administration, frequently after the loading dose, every 6 hours during the maintenance infusion, and until 48 hours after the end of the infusion. Amrinone clearance was 2.4 +/- 0.9 mL/kg/min in neonates and 3.2 +/- 1.2 mL/kg/min in infants (p < 0.05). The volume of distribution at steady-state was smaller (p < 0.05) in neonates than in infants. The elimination half-life of amrinone was 10.7 +/- 6.7 hours in neonates and 6.1 +/- 1.4 hours in infants (p < 0.05). There was a linear correlation between the clearance of amrinone and the body surface area (r = 0.67; p < 0.05). The ratio of the plasma concentration of N-acetylamrinone to that of amrinone did not differ between neonates and infants. CONCLUSIONS: Amrinone is eliminated at a slower rate in neonates than in infants. The rate of acetylation of amrinone appears to be similar; the differences in the elimination capacity of amrinone are mainly due to the immature renal function in neonates.

Amrinone↗
PubMed2000

Association of severe placental insufficiency and systemic venous pressure rise in the fetus with increased neonatal cardiac troponin T levels.

OBJECTIVE: The aim of this study was to test the hypothesis that severe placental insufficiency and a rise in fetal systemic venous pressure are associated with fetal myocardial cell damage, which in turn leads to increased neonatal troponin T levels. STUDY DESIGN: Sixty-six neonates born after uncomplicated pregnancy and delivery were included in the control group. Study groups 1 and 2 consisted of 32 and 5 neonates, respectively, born to women with hypertensive disorder. In study group 1 the fetal intra-abdominal portion of the umbilical vein showed normal nonpulsatile blood flow pattern in every case. In study group 2 all the fetuses had atrial pulsations in the intraabdominal umbilical vein. After delivery blood samples were collected from the umbilical arteries, and cardiac troponin T concentrations were measured with commercially available enzyme-linked immunosorbent assay kits. A clinically significant troponin T level was set at >/=0.10 ng/mL. RESULTS: In study group 1 the maternal main uterine arterial blood flow pattern was normal in 30 cases and abnormal in 2 cases. Umbilical artery blood velocity waveforms were normal in 26 fetuses, 4 fetuses had a decreased diastolic blood flow, 1 fetus had an absent diastolic blood flow pattern, and 1 fetus had a retrograde diastolic blood flow pattern. In study group 2 maternal uterine arterial Doppler findings were abnormal in every case, and all the fetuses had retrograde diastolic blood flow pattern in the umbilical artery. Neonatal troponin T levels were <0.10 ng/mL in the control group (0-0.14 ng/mL) and in study group 1 (0-0.16 ng/mL), except for 1 case in each group. Every neonate in study group 2 had a troponin T level >0.10 ng/mL, with the range from 0.11 to 0.35 ng/mL. In study group 2 troponin T concentrations were significantly higher (P <.0001) than in either the control group or study group 1. CONCLUSION: Neonatal troponin T levels are not clinically significantly increased in normal pregnancies and in pregnancies complicated by maternal hypertensive disorder but with normal fetal umbilical venous return. Neonatal troponin T concentrations are significantly increased in the presence of abnormal umbilical venous return, which indicates myocardial cell damage.

Adult↗
PubMed2000

Postoperative nitric oxide therapy in children with congenital heart disease. Can the need be predicted?

The necessity for postoperative inhaled nitric oxide (NO) therapy and predictive factors for that need were retrospectively analysed in 457 paediatric patients at risk of pulmonary hypertensive events following open-heart surgery for congenital heart disease. Inhaled NO was given postoperatively to 46% of the study group and to 23% of all patients undergoing open-heart surgery during the study period. Factors associated with increased need for postoperative NO were age <1 year, Down's syndrome, preoperative pulmonary hypertension and increased pulmonary vascular resistance. Using a multivariate model based on these factors, 73% of the patients who were given NO were identified. Thus, in a setting with unrestricted access to NO therapy, almost half of the patients with cardiac lesions that commonly give rise to postoperative pulmonary hypertension were given postoperative NO. Seventy-three percent of postoperative NO treatment was associated with a relatively small number of pre- and perioperative patient-related risk factors.

Adolescent↗
PubMed1998

Efficacy of cardiopulmonary resuscitation in pulseless paediatric trauma patients.

BACKGROUND: A study was designed to determine which paediatric trauma patients with no detectable vital signs are likely to benefit from cardiopulmonary resuscitation (CPR). METHODS: A 10-year retrospective study of all pulseless patients under 16 years of age with trauma in whom CPR was initiated in a prehospital or in-hospital setting in Southern Finland. RESULTS: Forty-one patients, 25 male and 16 female, were included in this study. The mean age was 7.8 years (range 0.1-15.9 years). Twenty three patients had blunt injuries and three patients had penetrating injuries. The mean Injury Severity Score was 51 (range 25-75). In 15 patients, the arrest was secondary to smoke inhalation, strangulation or electric shock. Resuscitation was initiated at the scene or en route in 28 patients and in 13 patients at the hospital. Five patients received open-chest CPR and 36 patients closed-chest CPR. Spontaneous circulation was restored in four patients with open-chest CPR and in six patients with closed-chest CPR. Two patients had intact survival and one patient survived with moderate disability. The mechanism of traumatic cardiac arrest, initial cardiac rhythm or location of arrest did not seem to affect outcome of CPR. CONCLUSIONS: The overall survival rate of paediatric patients with cardiac arrest secondary to trauma is poor. Trauma patients in whom cardiac arrest is caused by respiratory arrest or by thoracoabdominal trauma in the hospital setting may have a chance of survival if a spontaneous circulation is rapidly restored with effective resuscitative measures.

Cardiopulmonary Resuscitation↗
PubMed1998

Detection of lung injury with conventional and neural network-based analysis of continuous data.

OBJECTIVE: To test if analysis of pressure and flow waveform patterns with an artificial intelligence neural network could distinguish between normal and injured lungs. METHODS: Acute lung injury was induced in ten healthy anesthetized, mechanically ventilated dogs with repeated injections of oleic acid, until arterial blood oxyhemoglobin saturation reached 85% breathing room air. Airway pressure, esophageal pressure, airway flow, and arterial and mixed venous saturation signals were stored at 2 min intervals. Hemodynamic and blood gas data were collected every 10 min. Back-propagation neural networks were trained with normalized airway pressure and flow waveforms from normal and fully injured lungs. RESULTS: The networks scored lung injury on a continuous scale from +1 (normal) to -1 (injured). Network scores unequivocally distinguished between normal and fully injured lungs and suggested a gradual transition from normal to injury pattern. However, the response of the network was slow compared to compliance, resistance and venous admixture. CONCLUSIONS: Normal and fully injured lungs display distinct flow and pressure waveform patterns which are independent of changes in calculated pulmonary mechanics variables. These patterns can be recognized by a neural network. Further research is needed to determine the full potential of automated pattern recognition for lung monitoring.

Animals↗
PubMed1998

Measured versus predicted oxygen consumption in children with congenital heart disease.

OBJECTIVE: To compare measured and predicted oxygen consumption (VO2) in children with congenital heart disease. DESIGN: Retrospective study. SETTING: The cardiac catheterisation laboratory in a university hospital. PATIENTS: 125 children undergoing preoperative cardiac catheterisation. INTERVENTIONS: VO2 was measured using indirect calorimetry; the predicted values were calculated from regression equations published by Lindahl, Wessel et al, and Lundell et al. Stepwise linear regression and analysis of variance were used to evaluate the influence of age, sex, weight, height, cardiac malformation, and heart failure on the bias and precision of predicted VO2. An artificial neural network was trained and used to produce an estimate of VO2 employing the same variables. The various estimates for VO2 were evaluated by calculating their bias and precision values. RESULTS: Lindahl's equation produced the highest precision (+/- 42%) of the regression based estimates. The corresponding average bias of the predicted VO2 was 3% (range -66% to 43%). When VO2 was predicted according to regression equations by Wessel and Lundell, the bias and precision were 0% and +/- 44%, and -16% and +/- 51%, respectively. The neural network predicted VO2 from variables included in the regression equations with a bias of 6% and precision +/- 29%; addition of further variables failed to improve this estimate. CONCLUSIONS: Both regression based and artificial intelligence based techniques were inaccurate for predicting preoperative VO2 in patients with congenital heart disease. Measurement of VO2 is necessary in the preoperative evaluation of these patients.

Calorimetry, Indirect↗
PubMed1996

Neural network-based detection of esophageal intubation in anesthetized patients.

OBJECTIVE: To test whether a neural network-based method could differentiate between tracheal and esophageal intubation in anesthetized patients by recognizing breathing circuit pressure and flow waveform patterns. METHODS: Tracheal tubes were placed in the trachea and in the esophagus of adult patients undergoing elective operations. After ensuring for proper oxygenation, ventilator settings were changed to 5 ml/kg tidal volume (VT) and 15 cpm and circuit pressure and flow were recorded for 15 seconds. Then, the breathing circuit was switched to the tube placed in the esophagus, and signals were recorded for an additional 15-second period. During off-line analysis, individual waveforms were separated. Tracheal breaths were labeled with a score of 1 while esophageal "breaths" were labeled with -1. A neural network was defined to learn to associate waveforms to their corresponding scores. Data from 54% of the patients were used to train the neural network. Data from the remaining subjects were used for testing. RESULTS: Forty-six patients were studied. Neural network training was achieved with 100 tracheal and 94 esophageal waveforms from 25 patients. Neural network performance was tested on 84 tracheal and 76 esophageal waveforms from 21 subjects. The neural network assigned scores of 0.99 +/- 0.05 (mean +/- SD) to tracheal waveforms and -0.99 +/- 0.03 to esophageal waveforms. The difference between mean esophageal and tracheal scores was -1.99 with a 99.999% confidence range of -2.01 to -1.96. Any arbitrary cutoff threshold, ranging between -0.76 and 0.7, separated tracheal and esophageal score regions, yielding no false positive or negative results. CONCLUSION: A neural network differentiated consistently tracheal from esophageal intubation when the ventilation test mode was used. The ventilation mode employed is feasible in most adult patients undergoing elective procedures under general anesthesia. Further research is required to train neural networks to recognize esophageal intubation in different age groups and when different ventilation modes are applied.

Anesthesia, General↗