Biomedical subjects

D Cates

Publications and source records attributed to D Cates.

13 recordsLinked to original sources

PubMed1992

Effects of inhaled oxygen (up to 40%) on periodic breathing and apnea in preterm infants.

To discover whether increases in inhaled O2 fraction (FIO2; up to 40%) decrease apnea via an increase in minute ventilation (VE) or a change in respiratory pattern, 15 preterm infants (birth weight 1,300 +/- 354 g, gestational age 29 +/- 2 wk, postnatal age 20 +/- 9 days) breathed 21, 25, 30, 35, and 40% O2 for 10 min in quiet sleep. A nosepiece and a flow-through system were used to measure ventilation. Alveolar PCO2, transcutaneous PO2, and sleep states were also assessed. All infants had periodic breathing with apneas greater than or equal to 3 s. With an increase in FIO2 breathing became more regular and apneas decreased (P less than 0.001). This regularization in breathing was not associated with significant changes in VE. However, the variability of VE, tidal volume, and expiratory and inspiratory times decreased significantly. The results indicate that the more regular breathing observed with small increases in FIO2 was not associated with significant changes in ventilation. The findings suggest that the increased oxygenation decreases apnea and periodicity in preterm infants, not via an increase in ventilation, but through a decrease in breath-to-breath variability of VE.

Apnea↗

PubMed1992

Small preterm infants (less than or equal to 1500 g) have only a sustained decrease in ventilation in response to hypoxia.

The classic "biphasic" ventilatory response to 15% O2 was previously observed in preterm infants who were large compared with those in the intensive care nursery today. We hypothesized that in the smaller infant (less than or equal to 1500 g) the response might be closer to that of the fetus, with no initial increase in ventilation. Thus, we studied 14 healthy preterm infants less than or equal to 1500 g [birth weight 1200 +/- 63 g (mean +/- SEM); gestational age 29 +/- 0.4 wk; postnatal age 17 +/- 3 d] during rapid eye movement and quiet sleep. Ventilation was measured using a nosepiece and a flow-through system. Sleep states were defined using EEG, electro-oculogram, and body movements. After a control period in 21% O2 (3 min), infants breathed 15% O2 for 5 min. In rapid eye movement sleep, minute ventilation decreased from 0.186 +/- 0.020 (control) to 0.178 +/- 0.021 (30 s), to 0.171 +/- 0.017 (1 min; p = 0.03), to 0.145 +/- 0.016 (3 min; p = 0.002), and to 0.129 +/- 0.011 l.min-1.kg-1 (5 min; p = 0.004). In quiet sleep, it decreased from 0.173 +/- 0.019 (control) to 0.164 +/- 0.019 (30 s), to 0.166 +/- 0.019 (1 min), to 0.148 +/- 0.013 (3 min; p = 0.03), and to 0.146 +/- 0.012 l.min-1.kg-1 (5 min; p = 0.04).(ABSTRACT TRUNCATED AT 250 WORDS)

Humans↗

PubMed1992

The effects of 21 or 30% O2 plus umbilical cord occlusion on fetal breathing and behavior.

We have shown previously that continuous fetal breathing can be induced by 100% O2 alone or combined with umbilical cord occlusion (Baier, Hasan, Cates, Hooper, Nowaczyk & Rigatto, 1990). To know whether it could also be induced by lower O2 concentrations plus cord occlusion, we studied 9 chronically instrumented fetal sheep (16 experiments) using our window model. After a baseline cycle [1 low voltage + 1 high voltage electrocortical activity (ECoG) epoch] the fetal lung was distended via an endotracheal tube to about 30 cm H2O. Inspired N2 (control) and 21 or 30% O2 were given for one cycle each. While on 21% or 30% O2 the umbilical cord was occluded (balloon cuff). In 10 out of 16 experiments breathing output (% maximum of integral of EMGdi x f) increased after cord occlusion from 80 +/- 48 (N2) to 2871 +/- 641 (SEM; P < 0.01); in 7 of them breathing became continuous. Arterial PO2 increased from 14 +/- 1 (N2) to 33.5 +/- 5 Torr (occlusion; P < 0.01). In the other 6 experiments breathing output decreased from 319 +/- 116 (N2) to 86 +/- 38 (occlusion; P < 0.01) and arterial PO2 changed from 18 +/- 1 (N2) to 22 +/- 5 Torr (occlusion; P = 0.4). Arterial PCO2 increased similarly after occlusion in both groups, those which did respond with increased breathing (to 46 +/- 2 Torr) and those which did not respond (to 48 +/- 3 Torr; P = 0.6). The percent low voltage ECoG and the behavioral score increased after occlusion in the responder group only.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1989

Decrease in plasma prostaglandin E2 is not essential for the establishment of continuous breathing at birth in sheep.

Depression of prostanoid concentrations by indomethacin induces continuous breathing in fetal sheep, but it is not known whether this is associated with changes in fetal behaviour. Furthermore, the relationship between changes in prostaglandin E2 (PGE2) concentration after delivery and the appearance of continuous breathing has not been examined. We hypothesized that the decrease in fetal PGE2 by infusion of indomethacin would induce continuous breathing and a change in behaviour such that the fetus should come to resemble a newborn lamb; and coinciding with the establishment of continuous breathing at birth, PGE2 concentrations would decrease to a critical level below that present in the fetus. We found that continuous breathing in fetal sheep induced by infusion of indomethacin was related to a decrease in PGE2 from 436 +/- 114 to 189 +/- 73 pg/ml (P less than 0.005) but that this was not associated with fetal wakefulness. In addition, measurements of carotid arterial PGE2 concentrations showed that the beginning of continuous breathing after birth occurred at a plasma concentration of PGE2 of 1245 +/- 260 pg/ml, a value about three times higher than the 422 +/- 53 pg/ml measured in the fetus during breathing activity. Together these findings suggest that PGE2 is not primarily involved in the establishment of continuous breathing at birth.

Animals↗

PubMed1988

Effect of increased arterial CO2 on fetal breathing and behavior in sheep.

We studied breathing and behavioral response to increased arterial CO2 (PaCO2) in 12 fetal sheep between 130 and 145 days of gestation. Of these 12 fetuses, 10 had an increase in PaCO2 through maternal rebreathing of CO2; in the other 2 fetuses CO2 was increased via an endotracheal tube and application of continuous distending airway pressure. We used our window technique to observe and videotape fetal behavior. The experiments consisted of recording breathing activity and behavior during resting conditions (1 low- and high-voltage ECoG cycle) and during administration of CO2. We measured electrocortical activity (ECoG), eye movements (EOG), electromyography of the diaphragm (EMGdi) and neck muscles, tracheal (Ptr), amniotic, and carotid arterial pressures. Administration of CO2 by the rebreathing technique produced an increase in the amplitude of breathing activity as reflected by an increase in Ptr from 5.0 +/- 0.6 to 12 +/- 1.9 mmHg (P less than 0.01) and an increase in SEMGdi from 32 +/- 4 to 77 +/- 8% max (P less than 0.001). Frequency increased due to a decrease in inspiratory (TI) and expiratory duration. Ptr/TI increased from 11.0 +/- 2.0 to 37.4 +/- 9.0 mmHg/s (P less than 0.05) and SEMGdi/TI increased from 67 +/- 7 to 221 +/- 28% max/s (P less than 0.001). Although the response was at times prolonged into the transitional high-voltage zone, it did not persist during established high-voltage ECoG.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1988

Ventilatory response to hypoxia in unanesthetized newborn kittens.

We studied the ventilatory response to hypoxia in 11 unanesthetized newborn kittens (n = 54) between 2 and 36 days of age by use of a flow-through system. During quiet sleep, with a decrease in inspired O2 fraction from 21 to 10%, minute ventilation increased from 0.828 +/- 0.029 to 1.166 +/- 0.047 l.min-1.kg-1 (P less than 0.001) and then decreased to 0.929 +/- 0.043 by 10 min of hypoxia. The late decrease in ventilation during hypoxia was related to a decrease in tidal volume (P less than 0.001). Respiratory frequency increased from 47 +/- 1 to 56 +/- 2 breaths/min, and integrated diaphragmatic activity increased from 14.9 +/- 0.9 to 20.2 +/- 1.4 arbitrary units; both remained elevated during hypoxia (P less than 0.001). Younger kittens (less than 10 days) had a greater decrease in ventilation than older kittens. These results suggest that the late decrease in ventilation during hypoxia in the newborn kitten is not central but is due to a peripheral mechanism located in the lungs or respiratory pump and affecting tidal volume primarily. We speculate that either pulmonary bronchoconstriction or mechanical uncoupling of diaphragm and chest wall may be involved.

Aging↗

PubMed1987

A developmental study on types and frequency distribution of short apneas (3 to 15 seconds) in term and preterm infants.

We measured the frequency distribution and the ventilatory correlates of the various types of apneas 3 to 15 s long during sleep in eight term infants (birth weight 3.65 +/- 0.16 kg; gestational age 39.5 +/- 0.3 wk) and eight preterm infants (birth weight 2.07 +/- 0.18 kg; gestational age 34.3 +/- 0.4 wk). Each infant was studied on five to seven occasions from birth to 56 wk of postconceptual age using a modified flow-through system. Sixty-six paired epochs of quiet sleep (1163 min) and rapid eye movement sleep (829 min) were analyzed in term infants and 85 paired epochs of quiet sleep (1553 min) and rapid eye movement sleep (1328 min) in preterm infants. Of the 783 apneas recorded in term infants 82% were central, 1.5% obstructive, 0.5% mixed, and 16% were of the breath-holding type; the corresponding figures for the 4086 apneas recorded in preterm infants were 93, 0.5, 1.0, and 5.5%. This distribution was similar in the two sleep states but term infants had a higher percentage of breath-holding apneas than preterm infants (p less than 0.01). In preterm infants the rate of central apneas decreased with postnatal age (p less than 0.01); in term infants the rate did not change significantly. The duration of apneas showed a modal distribution for central apneas at about 8 s for both groups during the 1st month of life (p less than 0.05). The findings suggest: 1) apneas in the newborn and early infancy are primarily central and are more frequent in preterm than in term infants.(ABSTRACT TRUNCATED AT 250 WORDS)

Apnea↗

PubMed1986

Fetal breathing and behavior measured through a double-wall Plexiglas window in sheep.

The inability to see the fetus makes the assessment of fetal behavior difficult. To circumvent this problem we implanted a Plexiglas window in the left flank of the ewe. Fetuses were instrumented for measurements of sleep, breathing, and swallowing. Ten fetal sheep were studied on 32 occasions. Six fetuses were delivered through the window at term, and postnatal behavior was compared with intrauterine behavior. Fetuses observed during resting conditions alternated between periods of quiet sleep [high-voltage electrocortical activity (ECoG)] and active or rapid-eye-movement sleep (low-voltage ECoG). In quiet sleep, movements were absent except for periodic generalized electromyographic discharges. Eye and breathing movements were rare or absent. Swallowing was also absent. In active sleep, movements were increased with powerful breathing and swallowing activity. Fetal wakefulness defined by open eyes and purposeful movements of the head was never seen in utero but was clearly observed after delivery. We conclude that fetal wakefulness as defined postnatally was not able to be demonstrated in utero.

Animals↗

PubMed1985

The effect of rebreathing CO2 on ventilation and diaphragmatic electromyography in newborn infants.

We tested the hypothesis of whether the reduced ventilatory response to CO2 in preterm as compared to term infants is related to primary central unresponsiveness, or to mechanical impairment of the respiratory pump. Eleven preterm (n = 19; gestational age 32 +/- 0.4 wk) and 14 term (n = 24; GA 40 +/- 0.3 wk) infants were studied. Minute integrated diaphragmatic activity EMGDi X f), and mean inspiratory diaphragmatic activity (EMGDi/TI), were used as indices of central output. After 3 min breathing 21% O2 (control), infants rebreathed from a bag containing 5% CO2 in 40% O2 for 2 to 3 minutes. We measured VE, VT, f, VT/TI. Sleep states were monitored. Preterm infants had a decreased ventilatory response to CO2 both in quiet sleep (QS) (0.0379 +/- 0.067 vs 0.505 +/- 0.032 L . (min . kg . kPa PACO2)-1; P less than 0.04) and in active sleep (AS) (0.210 +/- 0.032 vs 0.331 +/- 0.048 L . (min . kg . kPa PACO2)-1; P less than 0.04). The decrease in response primarily was a function of a lack of increase in tidal volume with CO2 in QS and a lack of increase in f in AS. Parallel to these changes there were significant correlations between the increases in EMGDi X f and VE with inhaled CO2 (r = 0.75; P less than 0.001); VT and EMGDi (r = 0.63; P less than 0.01); and between the increases in EMGDi/TI and VT/TI with inhaled CO2 (r = 0.64; P less than 0.001). The results suggest that ventilatory response to CO2 is (1) correlated highly with diaphragmatic indices of central output; (2) less in active than in quiet sleep; (3) less in preterm than in term infants. We conclude that despite their increased chest wall compliance, preterm infant respond less to CO2 because of central unresponsiveness.

Carbon Dioxide↗

PubMed1979

Immediate and late ventillatory response to high and low O2 in preterm infants and adult subjects.

The differences in the immediate (30 sec or 1 min) and late (5 min) ventilatory response to high and low O2 have not been quantitated in preterm infants and adult subjects using the same methods. It was thought that these differences might explain the paradoxical ventilatory response to CO2 at various O2 concentrations in preterm infants (12). Thus, 9 preterm infants and 10 adult subjects were given 21% O2 to breathe and then 100 or 15% O2 for 5 min each. Adults also breathed 15% O2 before 100% O2 or 12% O2 in order to make their resting arterial PO2 more comparable to those of infants breathing 21% O2. The ventilatory response to 100% O2 was the same in preterm infants and adult subjects, but the late response to 15% O2 remained paradoxical, ventilation decreasing at 5 min by 18% in infants and increasing by 19% in adults. The authors conclude: 1) the traditional concept of the ventilatory response to 100% O2 being different in infants and adult subjects is false; 2) the notion that the response to low O2 is paradoxical in infants is correct; and 3) the data do not explain why the response to CO2 under various background concentrations of O2 in infants is the reverse of that in adult subjects, but the depressed ventilatory response to hypoxia in infants may justify, at least in part, their flatter response to CO2 during low O2 breathing.

Adult↗

PubMed1979

Effect of sleep state on chest distortion and on the ventilatory response to CO2 in neonates.

In 10 preterm and 10 term infants, the effect of sleep state on chest distortion and on the ventilatory response to CO2 was assessed. It was found that chest distortion and ventilatory response to CO2 were independent of sleep state. Chest distortion, however, was more frequent in preterm than in term infants. The authors suggest that the increased prevalence of chest distortion in preterm infants is related to their highly compliant chest wall rather than to differences in sleep state.

Carbon Dioxide↗

PubMed1979

Quantitative noninvasive method to measure cerebral blood flow in newborn infants.

We measured cerebral blood flow (CBF) in 32 healthy neonates by venous occlusion plethysmography. Mean CBF was 63 ml/min/100 gm which compared favorably with invasive methods used in older children and adult subjects. We suggest that this is a useful method to quantify CBF in neonates. It may be valuable in assessing sequential changes occurring during asphyxia, intracranial hemorrhage, or during administration of various gas mixtures and drugs such as theophylline.

Blood Flow Velocity↗

PubMed1976

Effects of CO2 on immediate ventilatory response to O2 in preterm infants.

We wanted to know wheter the paradoxical response to CO2 under various background concentrations of O2 in preterm infants was mediated at the peripheral chemoreceptors. In five preterm infants we estimated peripheral chemoreceptor activity using the immediate change in ventilation (first 30 s) when 15%, 40%, 60%, or 100% O2 was substituted for 21% O2. Potentiation between O2 and CO2 was assessed by comparing the response with and without 4% CO2. CO2 enhanced the immediate hyperventilation with hypoxia (P less than 0.005) and reduced the immediate hypoventilation with hyperoxia (P less than 0.025 for 40% O2). This effect of CO2 increased from .00% to 15% O2 (P less than 0.05). These findings suggest: 1) CO2 interacts with O2 at the peripheral chemoreceptor level, and 2) because this interaction is more pronounced with hypoxia, the flatter CO2 response we observed with hypoxia was probably not mediated through the peripheral chemoreceptors and is likely to be central in origin.

Carbon Dioxide↗