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Biomedical subjects

G Sedin

Publications and source records attributed to G Sedin.

At least 73 records · Page 4Linked to original sources
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↗
PubMed1988

Influence of radiant heat stress on respiratory water loss in new-born lambs.

Respiratory water loss, oxygen consumption and carbon dioxide production were measured during rest and during moderate radiant heat stress in 9 healthy unanaesthetized lambs, age 4-15 days. The method used is based on an open flow-through system with a mass spectrometer for gas analyses. Respiratory water loss was 12.7 mg/kg min when the lamb was at rest and increased to 24.7 mg/kg min during heat stress. Oxygen consumption was 13.9 ml/kg min at rest and remained unchanged during heat stress. The mean rate of breathing increased from 63 to 125 breaths/min.

Animals↗
PubMed1987

Respiratory water loss in fullterm infants on their first day after birth.

Measurements of water loss from the airways, oxygen consumption and carbon dioxide production were made in 12 fullterm, newborn infants on their first day after birth, using an open flow-through system. The system includes a mass spectrometer, specially equipped with a water channel, for analysis of gas concentrations. To avoid condensation of water vapour, the tubing in the flow-through system is heated. Respiratory water loss was 4.9 +/- 1.2 (SD) mg/kg min, which meant an insensible water loss from the respiratory tract of 25.4 +/- 6.9 (SD) g per infant and 24 h at rest, at an ambient temperature of 32.2 degrees C and with an ambient humidity of 50%. Oxygen consumption was 6.0 +/- 0.8 (SD) ml/kg min. An inverse relationship was found between respiratory water loss and ambient humidity, with higher losses at a low than at a high humidity. Oxygen consumption did not change very much with ambient humidity.

Body Water↗
PubMed1987

Respiratory water loss in relation to activity in fullterm infants on their first day after birth.

Respiratory water loss (RWL), oxygen consumption and carbon dioxide production were measured in ten fullterm infants on their first day after birth, using an open flow-through system with a mass spectrometer, specially equipped with a water channel, for analysis of gas concentrations. Measurements were made both with the infant asleep and during different levels of motor activity. The ambient temperature was maintained at approximately 32.5 degrees C and the ambient relative humidity at 50%. RWL increased from 4.2 +/- 0.7 (SD) mg/kg min when the infant was asleep to 6.3 +/- 1.0 mg/kg min when he or she was awake but calm; with increasing activity there was a further increase in RWL. The oxygen consumption increased from 5.4 +/- 0.9 (SD) ml/kg min during sleep to 6.9 +/- 0.8 (SD) ml/kg min when awake, and also increased further with increasing activity.

Female↗
PubMed1987

The epidemiology of sudden infant death syndrome and attacks of lifelessness in Sweden.

Infants who died showing the syndrome of sudden infant death (SIDS) and infants who survived attacks of lifelessness (AL) were examined in a prospective epidemiological multicentre study over 24 months covering close to 40% of all births in Sweden. Seventy SIDS cases and 34 cases of AL were observed, giving an incidence for SIDS of 0.94/1000 and for AL of 0.46/1000. This SIDS incidence is higher than that observed during the seventies. The boy/girl ratio was 1.4:1 for SIDS and 1.6:1 for AL. The age distribution for AL resembled that for SIDS. Similarities were also seen with regard to place of occurrence. Sixty per cent of the SIDS cases occurred during the daytime/evening. Twenty-nine per cent of the infants with AL had more than one apneic spell during the three-day-period around the attack, indicating a period of respiratory instability, but only 12% had such spells later on. None of the infants who had had AL died from SIDS. The possible relationship between AL and SIDS is discussed.

Age Factors↗
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

Positive-pressure ventilation at moderately high frequency in newborn infants with respiratory distress syndrome (IRDS).

In 24 seriously ill newborn infants with respiratory distress syndrome (IRDS) and ensuing respiratory failure, high-frequency positive-pressure ventilation was administered. The mean gestational age of the infants was 32 +/- 3 weeks. In the infant ventilator employed, the compressible volume had been reduced in order to give higher flow rates but lower intratracheal pressures. The ventilation frequency was kept constant at 60-66 per min and the insufflation period at 32-35% of the ventilatory cycle. A positive end-expiratory pressure (PEEP) of 0.2-0.6 kPa was used. Arterial PCO2 was maintained at 4.0-5.3 kPa and PO2 at 8.5-10.5 kPa by adjusting the gas flow through the patient circuit, the peak tubing pressure, the PEEP and the oxygen concentration in inspired gas. High-frequency positive-pressure ventilation improved oxygenation and gave adequate alveolar ventilation in all infants, in most cases at a low peak pressure. Only one infant developed pneumothorax during intermittent positive pressure ventilation, and in no infant did bronchopulmonary dysplasia or retrolental fibroplasia occur. One infant died from intracranial hemorrhage during the ventilation period, giving a survival rate of 96%.

Female↗
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↗
PubMed1986

Measurement of respiratory water loss in newborn lambs.

A flow-through system for measurement of respiratory water loss, providing data on oxygen consumption and carbon dioxide production, is described. The system uses a mass spectrometer, specially equipped with a water channel, for analysis of gas concentrations. To avoid condensation of water vapour, the tubing in the flow-through system is heated. The method was tested by evaporating known amounts of water, and was found to be very accurate with a correlation coefficient of 0.999. Measurements were made in 10 fullterm lambs of varying postnatal age (4-15 days) and a mean respiratory water loss (RWL) of 11.7 mg kg-1 min-1 was found at rest. The RWL decreased with increasing postnatal age, as did oxygen consumption. The RWL at rest was influenced by the ambient relative humidity, with higher values at lower humidities.

Age Factors↗
PubMed1986

Heat loss from the skin of preterm and fullterm newborn infants during the first weeks after birth.

In 68 infants appropriate for gestational age, born after 25-41 weeks of gestation, the evaporation rate from the skin and ambient, skin and body temperatures were measured repeatedly during the first 4 weeks after birth, and the heat exchange due to evaporation, radiation and convection was calculated. All measurements were made at an ambient humidity of 50%, with the infants calm and quiet. High evaporative heat losses were found in preterm infants on their first days of life, with gradually decreasing values with increasing gestational and postnatal age. It was only during the 1st week of life in infants born at 25-27 weeks of gestation that evaporative heat loss was higher than radiative heat loss. The high evaporative heat losses in very preterm infants were balanced by low losses or even a gain through radiation and convection, because of the high ambient temperature needed to maintain a stable body temperature. Total heat loss increased with increasing gestational and postnatal age.

Aging↗
PubMed1985

Dispositions of di- and mono-(2-ethylhexyl) phthalate in newborn infants subjected to exchange transfusions.

The dispositions of the plasticizer di-(2-ethylhexyl) phthalate (DEHP) and its primary metabolite mono-(2-ethylhexyl) phthalate (MEHP) were studied in newborn infants subjected to exchange transfusions. During a single exchange transfusion the amounts of DEHP and MEHP infused ranged from 0.8-3.3 and 0.05-0.20 mg kg-1 body weight, respectively. There were indications that about 30% of the infused DEHP originated from parts of the transfusion set other than the blood bag. Approximately 30% of the infused amount of DEHP was withdrawn during the course of each transfusion. Immediately after the transfusions the plasma levels of DEHP ranged between 5.8 and 19.6 micrograms ml-1, and subsequently they declined rapidly. This decline, probably reflecting distribution of DEHP within the body, was followed by a slower elimination phase. The half-life of this phase was approximately 10 h. The maximal plasma levels of MEHP were about 5 micrograms ml-1. In one pre-term infant the elimination of MEHP was slower than its formation, whereas in one full-term newborn the formation appeared to be rate-limiting for the elimination.

Diethylhexyl Phthalate↗
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↗
PubMed1985

Ovarian hyperstimulation syndrome in preterm infants.

Estradiol-producing ovarian cysts were found in four very preterm females at a postconceptional age that slightly preceded the expected time of delivery. The serum concentration of estradiol was very high. In the first infant one cystic ovary was removed surgically. When cysts appeared in the other ovary, the girl was treated with medroxyprogesterone acetate. The serum concentration of estradiol then fell and the cysts disappeared. Medroxyprogesterone acetate treatment was given also to the second girl, who had a high and rising serum concentration of estradiol. In infants 3 and 4 the cysts disappeared and the serum estradiol normalized spontaneously. Measurements of serum concentrations of luteinizing hormone and follicle-stimulating hormone before and after an iv injection of luteinizing hormone releasing hormone showed that preterm girls with early estradiol-producing ovarian cysts have a postpubertal type of response to luteinizing hormone-releasing hormone. When the test is repeated some months later they have a prepubertal type of response, which is normal for their age.

Estradiol↗
PubMed1985

Measurements of transepidermal water loss in newborn infants.

Measurement of transepidermal water loss without disturbing the microclimate in the air layers above the skin has not been possible with previously available methods. The introduction of a new instrument, the Evaporimeter, for measuring the vapor pressure gradient above the skin surface meant that the evaporation of water from the skin could be determined. Each measurement is of short duration, and measurements can be made even in the most preterm infants under the conditions in which they are normally nursed. Studies of the evaporation rate and transepidermal water loss by this technique have increased our knowledge considerably during the last ten years. It is now well established that the loss of water from the skin surface is related to the ambient humidity, gestational age at birth, and postnatal age, and to weight, activity, and body temperature, and that it differs between appropriate- and small-for-gestational-age infants. Conclusions of special clinical importance drawn from these studies are that the most preterm infants may lose as much as 13 per cent of their body weight as TEWL during their first day after birth even at an ambient humidity of 50 per cent, and much more at a lower ambient humidity, and that their losses gradually diminish with age but are of significance even four weeks after birth. Small-for-gestational-age infants have a lower TEWL early after birth than appropriate-for-gestational-age infants. For heat exchange between the infant and its environment, TEWL plays an important role. In preterm infants, losses of heat through evaporation are very high early after birth. On the other hand, their heat losses through other routes are smaller because of the high ambient temperature in which they have be nursed in order to maintain a stable and normal body temperature. Simultaneous measurements of evaporation rate and skin blood flow have shown that the skin blood flow increases at a lower body temperature than the evaporation rate and that not all full-term infants sweat in a warm environment even when their body temperature becomes higher than 37.2 degrees C, which may indicate a delay in the postnatal adaptation of heat regulation. In addition, this regulation can easily be disturbed by a central cold-stimulation in infants who react with sweating in a warm environment.

Body Temperature↗