Ola Hjalmarson

Immediate Effects on Lung Function of Instilled Human Surfactant in Mechanically Ventilated Newborn Infants with IRDS

ABSTRACT. We have studied the effects on lung volume, respiratory mechanics and ventilation during the first hours after instillation of 60 mg/kg of human surfactant into the trachea of 4 very preterm, newborn infants with severe IRDS under mechanical ventilation. Measurements were made with a “face‐out” body plethysmograph and a modified nitrogen wash‐out method. In addition to a transient decrease in total and alveolar ventilation immediately after the instillation we found an immediate rise in lung volume, but respiratory compliance decreased. These changes lasted less than two hours. Oxygen requirements fell in 3 out of 4 infants. The changes in lung volume and compliance are explained in terms of changes in the shape of the static recoil pressure characteristics of the diseased lungs after treatment. Mechanisms behind the short duration are sought in mode of instillation, dosage, age at treatment, and severity of disease.

Lung Volume, Gas Mixing, and Mechanics of Breathing in Mechanically Ventilated Very Low Birth Weight Infants with Idiopathic Respiratory Distress Syndrome

ABSTRACT: We assessed pulmonary function in 14 mechanically ventilated newborn very low birth weight infants with idiopathic respiratory distress syndrome by means of a face-out, volume displacement body plethysmograph and nitrogen washout analyses. Specially designed computer programs were used for calculations of lung volumes, ventilation, gas mixing efficiency, and mechanical parameters. In addition to very low compliance and moderately elevated resistance of the respiratory system, there were considerably impaired gas mixing efficiency and low functional residual capacity (FRC). No correlations between positive end-expiratory pressure and mean airway pressure versus compliance, resistance, or FRC could be found. Neither could correlations be found between FRC and compliance or FRC and the calculated right to left shunt.

A plethysmographic method for assessment of lung function in mechanically ventilated very low birth weight infants.

ABSTRACT: We have developed and tested a plethysmographic method for assessment of lung function in mechanically ventilated very low birth weight infants during intensive care. Information about the mechanics of the respiratory system is obtained from the respiratory flow as measured by volume displacement plethysmography and from airway pressure measured in the artificial airway. Data on lung volumes, ventilation, and distribution of ventilation is obtained simultaneously by combining the respiratory flow measurements with nitrogen concentration analyses of the respiratory gas. No significant differences were found when the estimations of mechanical parameters and FRC were compared with reference methods and when determinations of the same parameters were repeated in the same subjects. The plethysmograph was shown to be safe and convenient to use, even in studies lasting several hours.

Epidemiological Analysis of the Increased Risk of Disturbed Neonatal Respiratory Adaptation after Caesarean Section

ABSTRACT. In a prospective, unselected study of all 4659 infants born in Göteborg, Sweden, risk factors for all kinds of neonatal respiratory disturbances (RD) after Caesarean section (CS) were analyzed. After CS, a significantly increased incidence rate of RD was found compared to vaginal delivery (24.6% vs. 5.5%). The increased overall risk affected full term infants only but IRDS was more common after CS in preterm infants. Rupture of membranes or uterine contractions prior to CS significantly reduced the incidence rate of RD in full term infants. Acute maternal complications did not affect the incidence. The elevated RD rate could partly be related to an increased incidence of low Apgar score after CS, and to absence of labour and rupture of membranes before the CS. But full term infants with Apgar score of 7 or more, delivered surgically after rupture of membranes and start of contractions, still had almost three times higher incidence of RD.

MECHANICAL AND VENTILATORY PARAMETERS IN HEALTHY AND DISEASED NEWBORN INFANTS

Neonatal pulmonary disease is a major clinical problem. Different pathogenetic patterns present themselves in a rather uniform clinical picture with increased respiratory frequency, cyanosis, retractions and often “grunting” breathing, often referred to as “respiratory distress”. Increasing knowledge of radiology, pathology, physiology and the clinical course in this syndrome has led to a differentiation in diagnoses. Idiopathic respiratory distress syndrome (IRDS) or hyaline membrane disease (HMD) (39) and aspiration syndrome (34, 40) or type I1 respiratory distress syndrome (37, 43) are dominant but other lung disease, congenital lung malformations and heart diseases often appear witk similar symtoms. Clinical respiratory disturbances may also originate from delayed functional adaptation immediately after birth and from disturbances of the central nervous system. A great deal of controversy exists about clinical diagnostic criteria in neonatal pulmonary disease. The main diagnostic methods used are lung X-ray, estimation of the degree of right-to-left shunt, determination of acid-base status and physical status. Pulmonary function testing has had no place in routine diagnostic work in neonates with pulmonary disease because of the lack of suitable methods. However, as described in the preceding paper, it is possible to analyse the pulmonary mechanics in a neonate without requiring any cooperation of the patient. Analysis of pulmonary mechanics in the neonates is of special interest as one factor of considerable importance in the pathogenesis of IRDS is considered to be an interference with the formation of surfactant (1 7) with consequences for the mechanical properties of the lung. It has also been shown that IRDS Aim of the study

Effects of Delivery by Caesarean Section on Lung Function in Healthy Newborn Infants

ABSTRACT. With the aim of extending previous studies showing differences in lung function after birth between infants delivered vaginally (VD) and by Caesarean section (CS) we investigated lung volumes, ventilation, efficiency of ventilation, and lung mechanics in 24 healthy, full term infants with no clinical signs of respiratory disease, 12 after VD and 12 after CS. Measurements were made on two occasions: 2 and 26 hours after birth. At 2 hours no differences in any measured quantity were found between the groups. The only difference found 24 hours later was that the average thoracic gas volume (TGV), was lower in infants after CS than after VD. The difference in functional residual capacity was, however, not significant. This means that the difference in TGV, previously also found by other workers, did not affect the ventilated air space. Our results do not support the theory of general inferiority in lung performance after birth in healthy, full term infants without respiratory disease delivered by CS.

Efficiency of ventilation in neonatal pulmonary maladaptation.

ABSTRACT. Lung physiology was studied in sixteen infants with pulmonary maladaptation (PMA) during the course of the disease and after clinical recovery. A sensitive nitrogen washout method was used. During the disease the infants showed reduced ventilatory efficiency and increased dead space. Total ventilation increased simultaneously, while alveolar ventilation was maintained. The majority of the infants showed greater functional residual capacity during the disease than after clinical recovery. The results suggest that gas mixing efficiency is impaired in infants with PMA and that this might be due to effects on the small airway function in the lungs.

THEORETICAL CONSIDERATIONS AND METHODS

A great deal of interest has been directed to the mechanical properties of the lungs of newborn infants during the last twenty years. Measurements of ventilatory mechanics, however, involve several problems and only a few investigations on pulmonary mechanics in newborns with lung desease have been published. Because of the existing interest in problems of differential diagnosis and monitoring of deseased newborn infants in our departments there was an interest in evaluating mechanical lung parameters in newborns with lung disorders for such purposes. Many systems have been used to measure flow and volumes in newborn infants during breathing, including pressureor volume-recording body plethysmography (13, 14, 15,42), inverse plethysmography (17, 28), pneumotachography (12) and impedance plethysmography (39). For our purposes we preferred a plethysmographic method for flow and volume measurements, as it would permit examinations to be made during more than a few breaths and under controlled circumstances. Such a method does not require a face mask, with its added dead space andtace irritation, and measurements of thoracic gas volume can be made with the same system (6, 29). For this study a flowdisplacement body plethysmograph was built and will be described. As distinguished from a closed plethysmograph, such a box may have small dimensions without the drawback of high back pressure, which may interfere with the ventilatory system, create unfavorable effects due to heat exchange and increase the risk of air leaks. It was also an advantage for us to have flow as the primary output signal as no differentiations were required before embarking on the computer analysis to be described. Essential advantages for measurements and calculations were achieved by combining this plethysmograph with a computer.

WORK OF BREATHING

The work of breathing in newborn infants with pulmonary disease is considered to be markedly increased (9, 11, 14, 18). Cook et al. (11) commented from their measurements of the work of breathing in two infants with respiratory distress that their results supported “the clinical impression that these infants frequently die of exhaustion”, and that “therapy should, at least in part, be directed toward support of respiratory efforts”. If this is the case measurement of the work of breathing might be of clinical value, helpful in choice of therapy and an important parameter for monitoring in diseased infants. However, to date only a limited number of observations have been reported on this topic.

2 IMMEDIATE EFFECTS OF TREATMENT WITH HUMAN SURFACTANT ON VENTILATION, LUNG VOLUME AND MECHANICS IN NEWBORN INFANTS WITH IRDS

We have studied lung function in 4 intubated and ventilated newborn infants with IRDS (birth-weights 1.1-1.47 kg, gest. age 26-29 w) immediately before and then repeatedly over 4 hours after instillation of human surfactant (100 mg/kg) into the endotrachealtubes. The infants were ventilated with max. insufflation pressures of 24-33 cml 120 and 4-10 cml 120 PEEP. Ventilatory flow was recorded by body plethysmography and FRC and ventilation efficiency by a N2 wash-out technique. Calculations were made by computer.In all infants FRC increased 20-120% within 10 min after treatment. Compliance of the respiratory system fell by 20-50%. Resistance was unaffected. Gas mixing improved over the first 30 min in 3/4. The changes in FRC and compliance returned within 45-90 min with a concomitant reduction of oxygenation. However, in 3/4 the need of oxygen or PEEP was persistantly reduced after treatment. We conclude that in these sick, ventilated infants with IRDS, the main effect of human surfactant in given doses was an immediate but transient increase of FRC that paralleled a fall in oxygen needs in 3/4. Supported by The Swedish Medical Research Council, Proj No. 5703.