Ruth B. Cherry

Studies of respiratory physiology in the newborn infant. II. Observations during and after respiratory distress.

An invitation to participate in this publication honoring Professor Wallgren confers no small distinction on any American pediatrician. It also imposes a high standard of scientific scholarship upon those so invited. The Harvard group working with newborn infants are more hopeful of meeting that standard because of the recent presence of one of Dr. Wallgrens own staff in our laboratory, a happy circumstance which has considerably increased the information we can contribute to this publication. Although we are submitting only a preliminary report of studies now in progress, the opportunity of presenting the data here was too tempting to be resisted by this international team of admirers of Professor Wallgren, C. A. S.

Nitrogen excretion by newborn infants during oxygen breathing

Summary 1. An average N 2 -excretion curve has been determined for infants breathing oxygen. 2. Infants excrete relatively more nitrogen during oxygen breathing than do adults. 3. The infant excretion curve for nitrogen should probably be used for correction of nitrogen-washout studies in the newborn.

90 Vascular Responses to Oxygen Breathing in the Newborn Infant

During the course of measurements of pulmonary function in newborn infants breathing 60–100 % oxygen, we have previously noted frequent, rapid and significant decreases in hematocrit and hemoglobin levels. The present investigation has been designed to confirm and elucidate this finding. 14 newborn infants varying in gestational age from 36–37 weeks, in birth weight from 2.7–4.6 kg and in postnatal age from 1–18 h breathed 60 % O2 by demand valve for periods of 60–70 min. Hematocrit (Hct), hemoglobin (Hb), total protein (TP) and blood gases were followed throughout and blood volume (CO method) was measured in 3 infants. Within 10 min of onset of O2 breathing prompt decreases of Hb, Hct, TP were seen reaching levels of 20 % below control values by 60 min. These changes promptly reversed upon resumption of air breathing. TP changes were seen to be more consistent and marked than changes in Hct or Hb. The response was seen with arterial O2 tensions of as low as 116 mm Hg. Total blood volume increases of 40–60 ml/kg were noted during O2 breathing in 3 infants. These data suggest auto-infusion of tissue fluid from some vascular bed in response to O2 breathing; this may imply an increase in precapillary resistance with consequent decrease in capillary pressure and derangement of the Starling equilibrium. Preliminary investigations indicate that bradycardia and increased peripheral vascular resistance are involved in this phenomenon. (APS)

Further studies on ventilation/perfusion relations in the newborn's lung

Radioisotope scanning of the lungs following the intravenous administration of macroaggregated albumin (MAA) labeled with I TM provides an assessment of the distribution of pulmonary blood flow between the r ight and left lung and between different areas of the same lung. The safety and validity of this technique have been tested in animals and man. In adults, the distribution of radioactivity between the r ight and left lung closely correlated with the oxygen consumption of each lung measured by bronchospirometry (r ~ 0.98, p ~ 0.001). Eight lung scintiscans were done in 6 patients with severe hyaline membrane disease (HMD) following the intravenous administration of 0.1 to 0.2 ml. of 1 per cent MAA labeled with 10 to 15 /~c of I TM. All patients required oxygen by face mask to relieve cyanosis. Four of the infants died, and all had H M D on histologic examination. An arterialized capillary pH greater than 7.30 was associated with a normal scan. Patients with a pH of 7.29 or less had either a relative decrease in the perfusion of one lung or nearly complete shunt ing of radioactivity to the liver and spleen via extrapulmonary right-to-left shunts. The diminution of pulmonary blood flow to one lung seen on the scans correlated with the increased severity of the disease on that side seen on the chest films. These findings are consistent with previous observations that effective pulmonary blood flow may be reduced in se~zere HMD. The lung scintiscan also demonstrates tha t the distribution of pulmonary circulation in H M D may be nonuniform.