In subjects breathing 100% 0 2 , arterial circulation was occluded proximal to transcutaneous 0 2 and COz electrodes. The linear fall of tcPo,, APo,, was used to quantitate skin metabolic rate, VO,. At 45"C, mean APo, was 16.8 kPa/min (127.2 mmHg/min). Multiplying by solubility, 0.0219 ml ml-latm-1, gives skin Vo, = 0.00366 ml 0 2 gm-1min-1. At 37°C (after vasodilation at 45"C), VO, was 0.00278. Assuming skin R Q = 0.8, the initial APCO, was used to estimate skin COz dissociation curve slope to be 1.48 ml gm-'atm-1. tcPc0, rose two to three times more rapidly when skin became hypoxic, suggesting anaerobic titration of skin HCO 5. After release of occlusion both electrodes yielded quasi-exponential returns to control from which blood flow was estimated to be 1.2 ml gm-lmin-1 from 0 2 rate, and 0.3 ml gm-lmin-1 from COz. Flow was also computed from the VO, and the (a-v)Po,, estimated to be twice the arterial to capillary PO, difference. Capillary PO, (cP0,) was computed from tcPo, by adding 30 mmHg (diffusion gradient at 45°C) and correcting CPO, to 37°C. Flow from this (a-v)Oz content difference and VO, averaged 0.39Computer programs have been developed to solve four simultaneous equations after determining tcPo, and Pao, at high and low PO, at two temperatures. Preliminary data in three adults gave mean blood flow values of 0.45 ml gm-'min-1. Equations also determine capillary temperature, Tc, and capillary to surface diffusion gradient, D:Tc = 0.92(Te-37) + 37, and D = 4 kPa (30 mmHg) at 45"C, where Te is electrode temperature. 0.10 ml gm-'min-1 at 45°C in 1 1 runs.

The stirring effect factor O , used to correct tcPo, readings for the gradient of Po, induced in skin by electrode 0 2 consumption, was measured with 20 pm cathode electrodes at 44°C for various membrane, spacer and electrolyte combinations. Two in vitro models closely resemble skin O values: (1) 50% ethylene glycol/water equilibrated with air at 44"C, compared to air above this liquid; (2) a mock skin consisting of 25 pm Teflon on foam rubber, in air, dry.varied from 1.01 with 22 pm polypropylene over a 12 pm cellophane spacer, with either aqueous or nonaqueous, chloride-free alkaline electrolyte, to more than 1.10 when 25 pm Teflon was tested without a spacer. may be predicted: 0 = 1 + 0.44 i/(M + 1OC + 20)

W e tested the hypothesis t h a t n e t L+R duct shunt contributes t o PBF surge i n premature lambs during the f i r s t hour of l i f e (Pediat. Res., 8:433, 1974) and t o high PBF seen l a t e r i n lambs with severe HMD (Pediat. Res., 5:393, 1975). Total PBF, r i g h t v e n t r i c u l a r output (RVO) and duct shunt were measured during f i r s t hours of l i f e i n 1 lamb with and 1 without HMD. A t 129-130d g e s t a t i o n , a pre-calibrated electromagnetic flow transducer with non-occlusive zero was implanted on the main pulmonary a r t e r y (PA) t o measure RVO; a s i m i l a r transducer was implanted on the postductal portion of the common PA t o measure PBF. Duct shunt was calculated a s the d i f f e r e n c e between PBF and RVO.Lambs were returned t o the amniotic cavity f o r 7-8d and then delivered by C-Section a t 137d gestation.I n each lamb, PBF rose sharply from < 50 t o peaks of 487 and 473 mllkglmin, respectivel y , a t 22 and 29 min of age and then s t a b i l i z e d a t lower l e v e l s >y 1 h r of age. RVO stayed a t high l e v e l s u n t i l a f t e r the PBF surge, then f e l l t o s t a b l e l e v e l s by 1 h r of age. During the F i r s t 4 h r , net L+R duct shunt accounted f o r 28 t o 68% of PBF :means 54 and 52%). These data suggest t h a t L-tR duct shunt cont r i b u t e s appreciably t o PBF during the PBF surge and a t age 1-4 l r . L+R duct shunt may be a major source of the high PBF x e v i o u s l y reported i n lambs with HMD. (RDS) in premature i n f a n t s i s associated with a deficiency of pulmonary s u r f a c t a n t . Disaturatec phosphatidylcholine (DSPC) i s the major phospholipid component oi s u r f a c t a n t . W e have u t i l i z e d the osmium t e t r o UCLA School of Medicine. D e~t . of P e d i a t r i c s . Los Anneles. Calif The acute and chronic e f f e c t s of URIs on lung function have not been adequately studied i n children. Four normal (N) and a l l e r g i c (A) children, 9-15 years i n age were studied prospect i v e l y a t baseline, a t the time of URI and 2, 4 , and 9 months following URI. Lung function s t u d i e s included maximal expirato flow-volume curves and the response of flows t o a helium-oxygen gas mixture (VisoV) , exercise and isoproterenol. A t baseline, 1 N.and 5 A had minor abnormalities i n flows measured a f t e r 50% (Vmax 50) and 75% ( k a x 75) o f t h e v i t a l capacity had been exhaled. A t t h e time of t h e URIs, 12/14 subjects had elevated Visoo; 8 had a f a l l i n FEV1, i m a x 50 and \;max 75; 9 subjects demonstrated a g r e a t e r than 10% f a l l i n flows with exercise ( t h i included a l l 4 N), but ~i s o ? was abnormal i n only 3/12 subjects post-exercise. With isoproterenol, FEVl did not change i n any s u b j e c t but Vmax 50 and Vmax 75 increased i n 10 s u b j e c t s ; ~i s o i ' was abnormal i n 4 s u b j e c t s . Two months following URI, small ailway obstruction and bronchial hyperreactivity were s t i l l evident i n nearly 1/2 of t h e s u b j e c t s , but t h e abnormaliti...

We investigated: (1) The effects of NaN03 concentration, membrane material and thickness, and electrolyte layer thickness on electrode 0 2 consumption, stirring effect ( a ) and response time; (2) The effect of NaN03 on P(H20) and electrode drift; and (3) The effect of KC1 on Ag deposition at the cathode. Electrolytes containing 0-8 M NaN03, 0.01 M KC1, and 0.1 M p H 7 phosphate were tested in a 20 pm cathode tcPo, electrode at 42°C. Increasing NaN03 concentration reduced 0 2 solubility and sensitivity by a factor: e-(c/4.G). Thus, sensitivity was a linear function of solubility. Without cellophane, sensitivity with 12 pm polypropylene was 50% that of 25 pm Teflon; 7 M NaN03 reduced sensitivity for both membranes by about 60%. 12 pm cellophane, by increasing the thickness of the electrolyte layer, minimized the difference between the membranes and exaggerated the effects of increasing NaN03 concentration on sensitivity. wasalinear functionofsensitivity. Cellophane decreased the ratio of 0 to sensitivity. Response times of electrodes were almost unaffected by addition of NaN03, but were increased as expected by use of thicker membranes, and by addition of cellophane spacers. Electrolyte vapour pressure was decreased 67% by addition of 7 M NaN03. When electrolyte vapour pressure differed significantly from that of skin or calibration solutions, water crossed the polypropylene or Teflon membranes, changing the 0 2 sensitivity, and causing drift both on skin and in calibration solutions. With KCI containing electrolytes. silver deposition occurs at the cathode, the rate of deposition increasing greatly as KC1 concentration approaches saturation. Thus addition of NaN03 to 0 2 electrolytes lowers vapour pressure, delays dehydration, reduces 0 2 sensitivity by reducing permeability of the electrolyte layer to 0 2 , and thereby reduces the gas/skin correction factor 0, without significantly delaying response time, and without increasing silver deposition.