Phase characteristics of breathing movements in healthy newborns

In the neonatal period, respiratory distortion of the chest wall in active sleep has been reported to reduce the thoracic gas volume. In order to investigate whether the distortion influences the tidal volume, a thorough quantification of the phase differences between the movements of the chest wall and the abdominal wall and the relation of the phase differences to the ventilation was performed on fifteen newborn infants sleeping in prone position. The changes in the circumference of the chest and abdomen were measured with mercury-in-silastic strain gauges; nasal air flow was monitored with a pneumotachograph. During quiet sleep, the movements of the chest wall and the abdominal wall were congruent and regular, and the tidal volume was not dependent on the observed phase differences between them. In active sleep, the breathing movements were incongruent, the tidal volume was negatively correlated with the phase shift between the movements of the chest wall and the abdominal wall, and the mean inspiratory flow was increased. Ventilation (ml/min) did not differ between the sleep states. This study thus suggests that, in healthy newborns in active sleep, the chest wall distortion leads to a reduction of the tidal volume, but ventilation is upheld by compensatory mechanisms, i.e. increased breathing rate and increased amplitude of movements of the diaphragm.     

Proconflict effect of carbon dioxide inhalation in rats

The effect of brief inhalation of carbon dioxide (CO₂) was studied in a conflict situation (Vogel test) in the rat. This treatment, which inhibits γ-aminobutyric acid (GABA)-mediated transmission in rat brain and induces anxiety and panic attacks in humans, elicited a proconflict effect. Exposure of rats for l min to CO₂ decreased by ~ 40% the number of licking periods in the test. This effect was abolished by prior administration of alprazolam (0.5 mg per kilogram of body Mass, I.p.). Although these results may support a role for GABA-mediated transmission in the anxiogenic effect of CO₂ inhalation, the possibility that different neurotransmitters other than GABA are involved in the action of CO₂ can not be ruled out.     

The interaction between oxygen and carbon dioxide movements in fishes

Many teleost fishes have haemoglobins which possess a Root effect, a large Haldane effect and a low buffer capacity. This combination of characteristics influences the interaction between movements of oxygen and carbon dioxide in the red cell, in the respiratory epithelium, and in the tissues. The presence of the Root effect may limit oxygen uptake at the gills due to an accumulation of Bohr protons released upon oxygenation. However, the Root effect is probably important in maintaining or elevating blood PO₂ during muscle capillary transit, enhancing oxygen delivery to the tissues.Bohr protons are reversibly bound to haemoglobin. The release of Bohr protons during oxygenation facilitates bicarbonate dehydration at the gills, while Bohr proton binding facilitates CO₂ hydration at the tissues. In some teleost fishes, most of the Bohr protons are released and bound to haemoglobin, between 50 and 100% of haemoglobin-oxygen saturation (27). This trait is probably significant in maximizing oxygen uptake at the gills and in conserving body CO₂ stores during exposure to hypoxia and exercise, when the lower reaches of the haemoglobin-oxygen equilibrium curve are used.     

Influence of breathing pattern on functional residual capacity in sleeping newborn infants

The present study was designed to assess the influence of breathing pattern on the variations of functional residual capacity during sleep in newborn infants. Functional residual capacity was measured by the He-dilution method. Neurophysiologic criteria were used to identify sleep states. Movements of chest and abdomen were monitored. Twenty-six healthy newborn infants were studied. Sixteen were premature and 10 were at term. Functional residual capacity did not change in relation to changes in sleep states. In active sleep it was 1.48 +/- 0.07 ml/cm compared with 1.50 +/- 0.06 ml/cm in quiet sleep. Functional residual capacity decreased when rib cage and abdomen moved out-of-phase with a value of 1.38 +/- 0.09 ml/cm as compared to 1.56 +/- 0.09 ml/cm when in phase (P less than 0.01), in the 7 infants who displayed these two opposite patterns.     

Effect of sighs on breathing memory and dynamics in healthy infants.

Deep inspirations (sighs) play a significant role in altering lung mechanical and airway wall function; however, their role in respiratory control remains unclear. We examined whether sighs act via a resetting mechanism to improve control of the respiratory regulatory system. Effects of sighs on system variability, short- and long-range memory, and stability were assessed in 25 healthy full-term infants at 1 mo of age [mean 36 (range 28-57) days] during quiet sleep. Variability was examined using moving-window coefficient of variation, short-range memory using autocorrelation function, and long-range memory using detrended fluctuation analysis. Stability was examined by studying the behavior of the attractor with use of phase-space plots. Variability of tidal volume (VT) and minute ventilation (VE) increased during the initial 15 breaths after a sigh. Short-range memory of VT decreased during the 50 breaths preceding a sigh, becoming uncorrelated (random) during the 10-breath presigh window. Short-range memory increased after a sigh for the entire 50 breaths compared with the randomized data set and for 20 breaths compared with the presigh window. Similar, but shorter duration, changes were noted in VE. No change in long-range memory was seen after a sigh. Coefficient of variation and range of points located within a defined attractor segment increased after a sigh. Thus control of breathing in healthy infants shows long-range stability and improvement in short-range memory and variability after a sigh. These results add new evidence that the role of sighs is not purely mechanical.     

Ferroxidases and xanthine oxidase in plasma of healthy newborn infants

In the neonatal period, there is a high iron load, while both the level and molar oxidase activity of ceruloplasmin are low. On the other hand, the neonatal xanthine oxidase (XO) activity is higher than later in life and XO has a significant iron-oxidizing capacity. We therefore studied the physiological contribution of XO to the ferroxidase activity of the plasma in 20 full-term newborn infants. Ferroxidase activity was measured spectrophotometrically, with Fe⁺⁺ as substrate. The uric acid formed by XO was assayed by means of HPLC, with electrochemical detection.

The total ferroxidase activity in the plasma was about one-fourth of the adult level and rapidly increased doubling within 3 days after birth. About 90% of the plasma ferroxidase activity was due to ceruloplasmin, the remainder being accounted for by ferroxidase II. The XO activity underwent a 30% (statistically non-significant) elevation at 24 h, though ferroxidase activity attributable to XO was not detected at any time.

Accordingly, XO does not seem to add substantially to the total iron-oxidizing capacity of the plasma in the neonatal period. The high molar ferroxidase activity is probably of importance at the endothelial cell surface.     

Ferroxidases and xanthine oxidase in plasma of healthy newborn infants

In the neonatal period, there is a high iron load, while both the level and molar oxidase activity of ceruloplasmin are low. On the other hand, the neonatal xanthine oxidase (XO) activity is higher than later in life and XO has a significant iron-oxidizing capacity. We therefore studied the physiological contribution of XO to the ferroxidase activity of the plasma in 20 full-term newborn infants. Ferroxidase activity was measured spectrophotometrically, with Fe⁺⁺ as substrate. The uric acid formed by XO was assayed by means of HPLC, with electrochemical detection.

The total ferroxidase activity in the plasma was about one-fourth of the adult level and rapidly increased doubling within 3 days after birth. About 90% of the plasma ferroxidase activity was due to ceruloplasmin, the remainder being accounted for by ferroxidase II. The XO activity underwent a 30% (statistically non-significant) elevation at 24 h, though ferroxidase activity attributable to XO was not detected at any time.

Accordingly, XO does not seem to add substantially to the total iron-oxidizing capacity of the plasma in the neonatal period. The high molar ferroxidase activity is probably of importance at the endothelial cell surface.     

Drug effect on the rotation thromboelastogram in newborn infants

The impact of the antibiotics carbenicilin and gentamycin on the aggregation and adhesiveness of thrombocytes and on the rotation thrombelastogramme is investigated in healthy newborns. Thrombocyte aggregation was markedly inhibited by carbenicilline; gentamycine had no influence. Thrombocyte adhesiveness was less influenced by both medicaments. The parameters of TEG, viz. reaction time, clotforming time, thrombus elasticity and index were compared before and after rotation and with and without medicaments. Under carbenicilline a prolongation of the clotforming time and a decrease of thrombus elasticity could be shown to exist after rotation. The impact of medicaments on the rotation thrombelastogramme can only be conceived by comparing the values before and after rotation in each case with and without medicament and not simply evaluating it, so that the rotation thrombelastogramms cannot be recommended to be used for assessing the disturbance of thrombocyte function induced by medicaments.     

The effect of carbon dioxide on egg production inMyrmica rubra

Summary An earlier study suggested that anaesthetization with heavy doses of carbon dioxide can be harmful to ants. It is shown that a light dose of carbon dioxide can be a safe and convenient anaesthetic for laboratory studies of ants of the genusMyrmica.     

Measuring equipment for bedside diagnosis of respiratory function in spontaneously breathing newborn infants

Equipment was developed for bedside lung function testing in the newborn using the simultaneous measurement of air flow rate, tidal volume, and esophageal pressure changes as a measure of transpulmonary pressure. The equipment has a number of advantages for the investigation of very low birthweight infants. A flow-through technique was used to eliminate the dead space of the face mask and a very thin micro-tipped catheter permits ready measurement of esophageal pressure. With this equipment, long-term measurements are also possible in oxygen-dependent newborns and the air-tightness of the mask can be monitored continuously. Long-time measurements in neonates are a prerequisite for standardizing the measuring conditions and adapting the duration of the measurement to the variability of the signals, especially in newborn with an irregular pattern of breathing.