Biomedical subjects

T Norsted

Publications and source records attributed to T Norsted.

14 recordsLinked to original sources

PubMed1999

Reactivation of human herpesvirus 6 during pregnancy.

Reactivation of human herpesvirus 6 (HHV-6) and cytomegalovirus (CMV) during pregnancy and transmission of the viruses to the fetus were investigated by polymerase chain reaction (PCR) and serology. In all, 104 blood samples were obtained 3 times during pregnancy and once at delivery. In another 107 women, samples were obtained only at delivery. Cord blood samples were obtained from both groups of women. HHV-6 DNA was detected in 41%-44% of the samples during months 3-8 of pregnancy, in 25% at delivery, and in 24% of age-matched controls. HHV-6 DNA was found in 1.0% of the cord blood samples. CMV DNA was detected in 1.7% of leukocytes from 104 pregnant women but in no cord blood sample. IgG antibodies to HHV-6 were found in 96% and CMV IgG in 62.5% of the women. HHV-6 IgG titers were significantly higher in HHV-6 PCR-positive women. Thus, HHV-6 reactivation seems common during pregnancy, and transfer of HHV-6 to the fetus may occur in approximately 1% of pregnancies.

Adult↗

PubMed1999

Short-term outcome of perinatal care in a Swedish county. Mortality, neonatal intensive care and overall evaluation of neuromotor function at 0-10 months of corrected age in preterm and term infants.

Improvements in obstetrical and neonatal care during the last decades have led to a marked increase in survival rate of preterm and term infants. In order to study the short- and long-term outcome in infants who survived neonatal intensive care (NIC) and were born in the county of Uppsala between January 1st 1986 and April 30th 1989, a prospective long-term follow-up study was conducted. Epidemiological data on all infants born in the county during the study period and the short-term outcome, measured as overall neuromotor function at term and at 2, 4, 6 and 10 months of corrected age in 245 infants surviving NIC and 72 healthy control infants are presented. The infants' neuromotor function was evaluated with different clinical neurological methods. In the study population of NIC infants 85.9% survived the neonatal period. The early infant mortality was high in this group 11.6% compared to that of all infants born in the county of Uppsala (0.30%). Only a minority of the infants showed abnormal neuromotor function. A comparison of the results of the overall evaluation of neuromotor function at 10 months of age with those of the examinations made at an earlier age showed poor correspondence in individual infants, especially in preterm and very preterm infants.

Bronchopulmonary Dysplasia↗

PubMed1999

Second trimester ultrasound screening performed by midwives; sensitivity for detection of fetal anomalies.

BACKGROUND: To assess the sensitivity for detection of fetal anomalies by a second trimester ultrasound screening program performed in a way representative of a majority of Swedish obstetrical departments. The examinations were performed at the ultrasound division of the Department of Obstetrics and Gynecology at the University Hospital of Uppsala, Sweden. METHOD: A prospective study covering a two-year period. Eight thousand two hundred and twenty-eight unselected, consecutive pregnant women (8345 fetuses) were examined. The ultrasound scans were performed at a gestational age of 15-22 weeks by specially trained midwives. All fetal anomalies suspected at the ultrasound screening were recorded. Follow-up of all scanned fetuses was done through neonatal reports, records from the pediatric department, a national malformation registry and autopsies. All live-born infants were followed one year after birth. Main outcome measures were sensitivity, specificity, and positive predictive value for detection of fetal anomalies and prevalence of fetal anomalies. RESULTS: In all 145 fetuses/infants with confirmed anomalies were identified (prevalence 1.7%). Thirty-two were detected by second trimester ultrasound screening (sensitivity 22.1%). Twenty false positive cases were identified, of which fifteen were ruled out on the same day the suspicion arose and five were transient findings. The specificity was 99.8% and the positive predictive value 61.5% CONCLUSIONS: When performing a second trimester ultrasound screening program, prenatal diagnosis of fetal anomalies will be part of the procedure whether this is a primary aim or not. It is therefore of great importance that the pregnant women receive adequate information and that the voluntariness of participation is stressed. In this study the sensitivity was low. Standardizing the scanning procedure (check-list for fetal anatomy) and improving the education of the operators are feasible ways to increase the sensitivity.

Adult↗

PubMed1997

Trigger delay in infant ventilators.

In an experimental study we determined the response trigger delay time of three infant ventilators with a capacity to detect and support spontaneous breathing. We measured this in anaesthetized cats as the time between the start of phrenic nerve activity and the increase in airway pressure caused by the subsequent inflation. Two modes of ventilatory support were used, namely Assist/Control (A/C) and synchronised intermittent mandatory ventilation (SIMV). We found that ventilators equipped with flow sensors close to the free end of the endotracheal tube had a shorter trigger delay than a ventilator which detected breathing with an abdominal sensor. Further, the trigger delay was shorter in SIMV mode than in A/C mode of operation. A higher set sensitivity reduced the response time. We conclude that triggered ventilation may be used in infants, at least when the spontaneous breathing rate is below 60 breaths per minute. This mode of ventilation could be useful when infants are to be weaned off the ventilator.

Animals↗

PubMed1996

Irregular breathing in young lambs and newborn infants during heat stress.

Ten healthy unanaesthetized full-term lambs, aged 4-12 days, were studied during moderate radiant heat stress, and 21 full-term newborn infants were studied during moderate convective heat stress. The rate of breathing and the breathing pattern were recorded, using strain gauges made of mercury-filled rubber tubing placed around the thorax and abdomen. In both the lambs and the infants the respiratory rate increased during heat stress. When this increase began, both the lambs and infants had short periods of very rapid breathing followed by short apnoeas. The concentrations of carbon dioxide and water in a flow-through system collecting expired air increased during the short periods of rapid breathing and then decreased again during the subsequent short apnoeic period.

Animals↗

PubMed1995

Endotracheal intubation influences respiratory water loss during heat stress in young lambs.

To study the effect of intubation on respiratory water loss (RWL) during heat stress, 10 young nonsedated lambs were exposed to radiative heat stress both when intubated and when not. RWL, oxygen consumption (VO2), and carbon dioxide production were monitored continuously by using a flow-through system with a mass spectrometer for gas analysis. When the lambs were not intubated, heat stress caused RWL to increase by 218%, whereas VO2 and body temperature remained unchanged. When the lambs were intubated, heat stress caused RWL to increase by 131% and VO2 to increase by 36%. On extubation during heat stress, RWL increased by 117 +/- 48% (standard error of the estimate) of the preextubation value and body temperature started to fall. This study shows that intubation reduces the ability of the lamb to increase RWL and heat loss during heat stress in a warm environment, possibly as an effect of exclusion of the nose and a reduction in dead space. After extubation, RWL increases markedly, a finding that might also be valid for intubated infants.

Animals↗

PubMed1994

The temperature of inspired air influences respiratory water loss in young lambs.

The temperature of inspired air influences respiratory water loss (RWL) in young lambs. Water loss from the airways, oxygen consumption and carbon dioxide production were measured using an open flow-through system with a mass spectrometer, specially equipped with a water channel, for gas analysis. Measurements were made in 9 newborn lambs at 3 different inspired air temperatures keeping all other environmental factors stable, including the ambient air temperature. The water content of the inspired air was also kept constant. RWL was found to be 9.9 +/- 3.9 (SD) mg/kg/min when the temperature of the inspired air was 30 degrees C and its humidity 30%. At 40 degrees C this loss increased to 11.5 +/- 3.6 mg/kg/min, and at about 60 degrees C it increased further to 26.0 +/- 8.2 mg/kg/min. The oxygen consumption was 10.0 +/- 0.8 (SD) ml/kg/min at 30 degrees C and 10.4 +/- 2.0 ml/kg/min at 60 degrees C, a change which is not significant. Thus RWL is influenced by the temperature of the inspired air, with greater loss at higher temperatures.

Air↗

PubMed1992

Airway pressures during positive pressure ventilation with superimposed oscillations before and after lung injury in the cat.

This study was made to determine how oscillations superimposed on intermittent positive pressure ventilation (IPPV) influence the arterial blood gases, pH and the airway pressures during adequate alveolar ventilation i.e. at inhibition of inspiratory activity, before and after experimentally induced lung injury in the anaesthetized cat. Two IPPV frequencies were studied. The lung was injured by instillation of xanthine oxidase into the upper airways during IPPV. The peak, mean and end-expiratory intrapleural and airway (intratracheal) pressures at two levels were measured and the arterial blood gases and pH were determined at inhibition of inspiratory activity with and without superimposition of oscillations on the ventilatory pattern. Before lung injury, superimposed oscillations lowered the airway pressures only at an IPPV rate of 15 breaths per minute (b.p.m.). After lung injury, such oscillations increased the airway pressures only at 15 b.p.m. The airway pressures were always lower at 60 than at 15 b.p.m.

Acid-Base Imbalance↗

PubMed1990

Respiratory response to adenosine in newborn lambs is modified by hypoxemia and by heat stress.

A study was made to determine whether adenosine is involved in the regulation of breathing and whether the respiratory response to injections of adenosine and its analogue L-PIA (phenylisopropyl adenosine) is modified by moderate hypoxemia or by heat stress. Unanesthetized lambs with chronically implanted catheters were used for the investigation. Intravenous injections of adenosine caused an increase in the rate of breathing lasting for 5-30 s, except during heat stress, when the rate of breathing decreased. Injection of L-PIA also increased the rate of breathing, but the effects lasted longer than after injection of adenosine. During heat stress the response to injection of L-PIA varied. Both the arterial blood pressure and heart rate decreased transiently after intravenous injection of adenosine or L-PIA, while the central venous pressure increased. Adenosine might thus be part of a positive feedback system that stimulates breathing under normal environmental conditions with or without moderate hypoxemia. The respiratory responses to injection of adenosine during heat stress are different, which might indicate that under this condition the effects of adenosine on breathing are modified by its influence on temperature control.

Adenosine↗

PubMed1990

Airway pressures during positive-pressure ventilation with superimposed oscillations.

This study was undertaken to determine whether oscillations superimposed on a regular ventilatory pattern influence the arterial blood gases and pH and the airway pressures at adequate alveolar ventilation at the onset of inhibition of inspiratory activity. The peak, mean and end-expiratory airway pressures were therefore measured at inhibition of this activity with and without superimposition of oscillations on the ventilatory pattern. It was found that superimposed oscillations lowered the airway pressure only at a low ventilatory frequency, whereas inhibition occurred at almost equal arterial PCO2 and pH values with and without superimposed oscillations on the ventilatory pattern.

Animals↗

PubMed1989

Pancuronium bromide does not lower airway pressures during intermittent positive pressure ventilation in young cats.

High intrapulmonary pressure is probably an important factor in the development of extra-alveolar air leaks and bronchopulmonary dysplasia during neonatal intermittent positive pressure ventilation (IPPV). Spontaneous breathing, which may be asynchronous with the ventilator as a result of hypoventilation or sometimes of the ventilatory pattern of the ventilator, can be prevented by neuromuscular blockade. During neuromuscular blockade with pancuronium bromide the central inspiratory (phrenic nerve activity) activity could be inhibited during IPPV at all ventilatory frequencies tested, but a lower arterial PCO2 and a higher pH were needed to achieve inhibition at a low frequency (15 bpm). In the present study it was observed that central inspiratory activity in cats was stimulated by intravenous injection of pancuronium bromide. In cats not subjected to neuromuscular blockade the inspiratory activity was inhibited during IPPV at all ventilatory frequencies studied. At the onset of inhibition of this activity, the arterial blood gases and pH in these animals were almost the same at all ventilatory frequencies. When ventilation was administered at a low frequency, higher peak intratracheal pressures were needed to obtain inhibition of central inspiratory activity than when high frequencies were used, both before and after neuromuscular blockade.

Animals↗

PubMed1987

Changes in inspiratory activity after injection of adenosine and hypoxanthine in cats.

The effects of intra-arterial and intravenous injections of adenosine and hypoxanthine were investigated with special reference to respiratory variables in anesthetized young cats. Studies were made of the effects on inspiratory activity (phrenic nerve activity), heart rate, blood pressure and central venous pressure. To assess the risk of accumulation of adenosine degeneration products after several injections measurements were also made of hypoxanthine, xanthine and urate in plasma at intervals after the injections. It was found that intra-arterial and intravenous injections of adenosine increased central inspiratory activity during the first few breaths after the injection. The blood pressure and heart rate decreased slightly and central venous pressure increased slightly after the injection. Degradation of adenosine and its metabolites takes place rapidly and it is therefore unlikely that metabolites influence the results. It is concluded that adenosine causes brief stimulation of inspiratory activity.

Adenosine↗

PubMed1986

Inhibition of phrenic nerve activity during positive-pressure ventilation at high and low frequencies.

A study was made to determine whether the ventilatory pattern, in terms of ventilatory frequency, insufflation period and end-expiratory pressure, influences the arterial blood gas level at which central inspiratory activity is inhibited, and whether further expansion of the lung changes this activity. This was accomplished by measuring arterial pH and blood gases, and intratracheal, intrapleural and transpulmonary pressures, at the setting of positive-pressure ventilation causing inhibition of phrenic nerve activity in chloralose-anaesthetized cats. Spontaneous breathing movements were prevented by muscle relaxation. Ventilatory frequencies of 15-120 breaths per minute (b.p.m.) were studied at at least two different insufflation times. A volume-controlled ventilator with a large compressible volume was used in the frequency range 15-45 b.p.m. and a constant flow respirator with a low-compressible volume in the range 45-120 b.p.m. A much lower PCO2 was needed for phrenic nerve activity to be inhibited at a ventilatory frequency of 15 b.p.m. than at higher frequencies. At ventilatory frequencies between 30 and 120 b.p.m. inhibition could be achieved at a higher PCO2, within the normal range. The inhibition of phrenic nerve activity tended to be less stable when PEEP was added during ventilation with a long insufflation period, but PEEP did not influence the arterial blood gas level at which inhibition occurred. In the lower frequency range of 15-30 b.p.m., inspiratory activity was observed with bursts at the same rate as the insufflations given by the ventilator. The intratracheal peak pressures at ventilation causing inhibition of phrenic nerve activity decreased with increasing ventilatory frequencies.(ABSTRACT TRUNCATED AT 250 WORDS)

Acid-Base Equilibrium↗

PubMed1985

Continuous positive airway pressure increases vagal and phrenic nerve activity in cats.

To investigate how continuous positive airway pressure (CPAP) changes the vagal nerve activity and whether CPAP alters the efferent phrenic nerve activity or the breathing pattern similarly before and after vagotomy, a study was made of vagal and phrenic nerve activity in chloralose-anaesthetized cats. In the vagal nerve, CPAP increased the mean impulse frequency during expiratory rest. The breath-related impulse frequency also increased with CPAP. With higher CPAP (greater than or equal to 0.5 kPa), the peak of breath-induced activity in the vagal nerve lasted longer than inspiration. In the phrenic nerve, the impulse frequency in the bursts increased almost linearly with CPAP irrespective of whether the vagal nerves were intact or not. The duration of the phrenic nerve bursts decreased with increasing CPAP when the vagal nerves were intact. When the vagal nerves were cut, the burst duration did not change. The rate of breathing was almost unchanged by CPAP regardless of whether the vagal nerves were cut or not. The inspiration/expiration ratio decreased with increasing CPAP when the vagal nerves were intact, but not when they were cut.

Animals↗