Torgny Norsted

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.

Skin conductance measurements as pain assessment in newborn infants born at 22-27 weeks gestational age at different postnatal age

BACKGROUND To assess pain or stress in newborn infants submitted to intensive care is important but difficult, as different observational pain scales are not always reliable in premature infants. As an indicator of pain, skin conductance (SC) measurements have detected increased sweating in newborn infants >28 gestational age (GA) submitted to heel lancing. OBJECTIVE To measure SC during heel lancing and routine care in newborn infants, born at 22 to 27 GA, with special relation to postnatal age (PNA). METHODS In six infants <28+0 GA and 4 infants ≥28+0 GA spontaneous SC activity and behavioural state (Neonatal Pain Agitation and Sedation Scale (N-PASS)) was measured before, during and after each intervention. Measurements were repeated in each patient at different PNA. RESULTS Baseline SC prior to intervention took longer time to stabilise and was higher in <28 than in ≥28+0 PNA. The combination of heel lancing and squeezing gave an increased SC in <28 PNA, whereas heel lancing alone gave the same SC response in ≥28+0 PNA. A possibly continued immature response in SC measurements was not observed. Oral glucose admission prior to heel lancing increased SC. Routine care did not give any changes in SC. Except during orogastric tube placement no signs of discomfort or pain could be detected by the neonatal pain, agitation and sedation scale (N-PASS) in <28 PNA. CONCLUSION Changes in SC could be detected in infants at <28+0 PNA and related to the combination of heel lancing and squeezing. A maturational development of the SC was observed in infants born <28 GA. SC seems to be able to differentiate between pain and discomfort.

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.

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 (≥ 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.

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.

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 frrqurnry, insufllation 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 pressurrs, 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 insumation 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 ronld be achieved at a higher Pco2, within the normal range. The inhibition of phrenic nerve activity tended to he less stable when PEEP was added during ventilation with a long insumation 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 insumations given by the ventilator. The intratracheal peak pressures at ventilation causing inhibition of phrenic nerve activity decreased with increasing ventilatory frequencies. The intratracheal peak pressure was always highest at 15 b.p.m., and at each ventilatory frequency it was higher when PEEP was used.

Shortterm outcome of infants born at the limit of viability in two Swedish tertiary care centers. |[dagger]| 1043

Of 7 tertiary care centers in Sweden, the University Hospitals in Uppsala and Umea have consistently had an aggressive approach to the treatment of newborns with gestational age (GA) of < 25 weeks.

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.

Ariway 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.

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.