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R H Hooper

Publications and source records attributed to R H Hooper.

7 recordsLinked to original sources
PubMed1992

Single breath measurement of pulmonary blood flow in man: the causes of variability.

Theoretically, pulmonary blood flow can be measured by the uptake of a 'soluble' gas (e.g. freon-22) compared with an 'insoluble' gas (e.g. argon). As with all indirect methods, a number of uncertainties exist. Inhalation of a freon-22 and argon mixture (3.5%, 10%, 35% O2 balance N2) was made, with a subsequent, slow steady exhalation. The complete manoeuvre is termed the single breath technique (SBT). The repeatability of the SBT was assessed over four repeat measurements at rest, the mean difference between paired measurements lying in the range -0.09 to 0.04 l min-1, excluding the first trial measurements. Various features of the SBT were investigated to assess their influence on the reliability of the technique. It is shown: that the initial volume inhaled should be close to vital capacity; that a brief period of apnoea greater than 9 s following inhalation is necessary; that the subsequent exhalation should be about 10 l min-1; and that difficulties associated with recirculation of freon-22 are not encountered, presumably due to its wide distribution in body water. Under these highly controlled circumstances the technique is reliable.

Adult↗
PubMed1990

Effective pulmonary flow, aortic flow and cardiac output: in vitro and in vivo comparisons in the dog.

This paper presents data on the measurement of aortic flow (Qa) using an electromagnetic flowmeter and the measurement of pulmonary blood flow (Qep) using a single-breath technique employing freon-22 as the soluble marker gas. The purpose was to assess the potential of a single-breath technique (using freon) as an effective way to estimate cardiac output (Q) non-invasively. The electromagnetic flowmeter was calibrated in vitro in an isolated heart-aorta preparation by collection of the ejected blood volume, thereby giving an absolute calibration of the Qa measurement. Using anaesthetized beagles Qa was measured immediately preceding (Qa,mean) and during (Qa,inst) measurement of Qep. These measurements were made before and after I.V. bolus doses of nifedipine used to increase cardiac output so as to measure a range of flows. The Qa was disturbed by the respiratory manoeuvre imposed as part of the single-breath technique, rising, falling and rising again as the lung volume was reduced, increasing with the test gas and reducing again, typically giving Qep = 1.39 +/- 0.13 l min-1, Qa,mean = 1.35 +/- 0.15 l min-1 and Qa,inst = 1.33 +/- 0.17 l min-1 (+/- S.D., n = 7 in each case). The standard deviations include interanimal variation as well as technique errors. Regression analysis of Qep on Qa,mean gave the highest correlation (r = 0.75) and the lowest coefficient of variation (11.7%), the values being 0.69 and 14.0% respectively for Qep on Qa,inst. These compare favourably with equivalent values for alternative methods reported in the literature, the strict calibration giving confidence that the single-breath technique provides data closely related to the aortic flow found prior to the respiratory manoeuvre, i.e. the undisturbed cardiac output.

Animals↗
PubMed1989

Solubility of freon-22 in blood and lung tissue.

Despite the frequent use of freon-22 (e.g. to measure pulmonary blood flow), there is no agreement on its solubility in water or body fluids. The values in the literature vary, often quoted without reference to measurement or identification as Ostwald or Bunsen coefficients. We used a Schölander apparatus and determined the Bunsen solubility coefficient (mlgas.(mlfluid.atmosphere)-1) at 37 degrees C as: 0.476 in water; 0.673 in human whole blood; 0.479 in human plasma; 0.662 in canine whole blood; 0.437 in canine plasma; and 1.077 in homogenized canine lung tissue. As pure freon was used, these solubilities may not be applicable if freon-22 does not obey Henry's law. In man, the Ostwald solubility coefficient is calculated as 0.76 ml/ml whole blood at BTPS. These results provide information for further studies involving freon-22, and clear the confusion which has arisen from poorly defined solubility coefficients.

Animals↗
PubMed1977

The hepatocellular uptake of glucose, galactose and fructose in conscious sheep.

1. Surgical techniques for chronic catheterization of hepatic and portal veins in the sheep are described. These catheters remained usable for 2-6 months and did not alter hepatic morphology. 2. Hepatocellular uptake of monosaccharides was estimated from their ability to pass the boundaries of the sucrose space in a double indicator dilution procedure in conscious fed sheep. 3. A large proportion (81%) of D-glucose carried in the portal blood was found to enter an hepatic cellular compartment. 4. The radioactive label of D-glucose infused in the portal vein remained associated with D-glucose in hepatic venous blood samples during the experimental period. 5. A large proportion (74%) of an infused trace of D-galactose, a smaller proportion (33%) of D-fructose, and negligible amounts of L-glucose were taken up in a single passage through the liver. 6. Raised blood concentrations of sucrose or of methyl-alpha-D-glucoside (Me-alpha-DG) significantly diminished the proportional uptake of D-glucose. Raised blood concentrations of glucose, galactose or Me-alpha-DG diminished the proportional uptake of D-galactose. Raised blood concentrations of fructose diminished the proportional uptake of fructose. 7. Neither total hepatic blood flow changes nor competitive effects within the cell could account for these findings. 8. It is concluded that these monosaccharides enter the liver cell by facilitated diffusion, and share at least some of the membrane elements that mediate this process. It seems likely that only a proportion of the glucose-transporting apparatus is accessible to galactose.

Animals↗