Effects of acute hypercapnia on the cardiovascular system (CYS) were studied in the anesthetized cat. After surgery the animal was exposed to a gas mixture of 12% CO2 and 25% O2 in nitrogen, and hypercapnia with low levels of arterial pH (pHa) was produced for 20 minutes. In the second run the same level of hypercapnia was induced by ventilating the same cat from the above gas mixture but pHa w...

Periodic breathing is a regularly recurring waxing and waning of tidal volume due to oscillations in central respiratory drive. It is a sign of respiratory control system instability. Under normal conditions, the respiratory and circulatory systems work in concert to deliver O2 according to metabolic demands, and to excrete CO2 to maintain acid-base homeostasis. As a result, arterial PO2 (PaO2)...

The peripheral chemoreflex was tested in healthy term infants by measuring the ventilatory response to 100% oxygen over 30 seconds. Minute ventilation did not change when studied two to six hours after birth. By contrast, at 2-6 days of age a mean decrease of 9.8% was noted, the difference between the groups being highly significant. There were no significant changes in respiratory rate. It is ...

Recent advances have clarified how the brain detects CO2 to regulate breathing (central respiratory chemoreception). These mechanisms are reviewed and their significance is presented in the general context of CO2/pH homeostasis through breathing. At rest, respiratory chemoreflexes initiated at peripheral and central sites mediate rapid stabilization of arterial PCO2 and pH. Specific brainstem n...

Spontaneous periodic breathing, although a common feature in fullterm and preterm human infants, is scarce in other newborn mammals. The aim of this study was to induce periodic breathing in lambs. Four 10-day-old and two <48-h-old awake lambs were instrumented with jugular catheters connected to an extracorporeal membrane lung aimed at controlling arterial PCO2 (PaCO2). Arterial PO2 (PaO2) was...