Biomedical subjects

H Rigatto

Publications and source records attributed to H Rigatto.

105 records · Page 6Linked to original sources

PubMed1975

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

To measure the effects of O2 on the ventilatory response to CO2 in preterm infants, we studied eight babies (birth wt 1-2 kg; gestational age 32-36 wk) 10 times during the first 11 days of life. After breathing 21% O2 for 3 min, they were given 15%, 21%, 40%, or 100% O2 for 4 min and then 2% CO2 plus the various concentrations of O2 for 4 min each. The mean slopes of the CO2 response curves were 0.013, 0.027, 0.034, and 0.056 1/(min-kg-mmHg PACO2) with 15%, 21%, 40%, and 100% inspired O2, respectively. Thus, the more hypoxic the infant, the flatter was the response to CO2. These findings suggest that in preterm infants 1) the response to inhaled CO2 is the reverse of that seen in adult man where the higher the inspired O2 concentration, the flatter the response, and 2) the respiratory center is depressed during hypoxia.

Carbon Dioxide↗

PubMed1975

Chemoreceptor reflexes in preterm infants: I. The effect of gestational and postnatal age on the ventilatory response to inhalation of 100% and 15% oxygen.

We studied 16 "healthy" preterm infants (birthweight, 1,000 to 2,000 gm) 94 times during postnatal life to define the effect of gestational and postnatal age on the ventilatory response to 100% and 15% oxygen. They were given air, then 100% oxygen for two and five minutes respectively (No.=63) or 21%, 15% and then 21% oxygen for five minutes each (No.=31). We measured respiratory minute and tidal volumes, frequency, heart rate, and alveolar PCO2 and PO2. We used the magnitude of the immediate change in ventilation during during 100% and 15% oxygen breathing to test peripheral chemoreceptor function. The immediate decrease in ventilation with 100% oxygen and the immediate increase in ventilation with 15% oxygen were statistically similar at different gestational and postnatal ages. The late increase in ventilation (five minutes) with 100% oxygen was also similar at different ages. However, the late decrease in ventilation with 15% oxygen was not present at 18 days of age. These findings suggest that: (1) the peripheral chemo-receptors are active at least from 28 weeks of gestation and are probably not important in triggering periodic breathing or apnea in preterm infants, and (2) the preterm infant matures his response to hypoxia and is able to sustain hyperventilation with low oxygen by 18 days of age.

Age Factors↗

PubMed1975

Chemoreceptor reflexes in preterm infants: II. The effect of gestational and postnatal age on the ventilatory response to inhaled carbon dioxide.

We studied nine "healthy" preterm infants (birthweight, 1,000 to 2,000 gm) 58 times during postnatal life to define the effects of gestational and postnatal age on the ventilatory response to carbon dioxide. The infants were given air and 2% and 4% carbon dioxide in air to breathe for five minutes each. We determined respiratory minute and tidal volumes, frequency,heart rate, and alveolar PCO2 and PO2. We measured ventilation with a nosepiece and a screen flowmeter, using a constant flow-through to eliminate valves and reduce diad space. Analysis were made during the fifth minute while the baby breathed the various gas mistures. The slope of the carbon dioxide response increased 42% from 32 to 37 weeks gestation (P smaller than .05) and 62% from 2 to 27 days of age (P smaller than. 025). However, the intercept at .3 liter/min/kg was the same at different gestational ages, but significantly greater at 2 compared with 27 days of age (P smaller than.05). We sugest that the unresposiveness primarily dependent on the mechanical abnormalities of the lung.

Age Factors↗

PubMed1973