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PubMed1986

Hepatic blood flow measurement with inert gas clearance.

Inert gas clearance has been used for 20 years to measure hepatic blood flow. Injection of a saline solution of 85Kr or 133Xe is usually made via the PV, and the resulting hepatic clearance is monitored with a Geiger-Müller tube, scintillation crystal, or gamma camera. Complex slow components in 133Xe clearance curves, once believed to indicate a correspondingly complex hepatic microcirculation, are now considered to be caused by nonhepatic radioactivity. Normal liver is therefore believed to receive a homogeneous perfusion throughout the depth of tissue in any given region. HA blood and PV blood are normally completely mixed in the hepatic sinusoids. Macroscopic variations in tissue perfusion may exist in different lobes of the liver in both animals and man. The technique expresses flow in units of milliliters per minute per 100 g. Accurate and acceptably reproducible results have been obtained after PV injection of isotope; fast component analysis of 133Xe clearance is most appropriate, while beta detection of 85Kr yields a simple monoexponential curve. Normal hepatic blood flow in dogs and in man is 100-130 ml min-1 100 g-1. Employing sites of isotope administration other than the PV produces inaccurate results unless appropriate corrections are made. Accuracy of flow measurement is critically dependent on a knowledge of the partition coefficient of the gas used. Liver disease per se does not affect measurement accuracy, and many practical features make the technique an attractive tool for the measurement of hepatic hemodynamics in man. Nevertheless, it is essential that the investigator be aware of certain limitations of the method, and carefully apply current concepts of clearance curve analysis and interpretation, in order to derive maximum advantage.

Animals↗
PubMed1984

Effect of posture on inter-regional distribution of pulmonary ventilation in man.

Regional ventilation per unit alveolar volume (V/VA) and regional lung expansion (FRCR/TLCR) were measured in twelve normal male human subjects in seated, supine, lateral decubitus and prone postures using a gamma camera and inhalation of the radioactive gases 81Krm (half-life 13 sec) and 85Krm (half-life 4.4 h). FRCR/TLCR decreased from superior to inferior in all postures except prone where it was uniform; V/VA increased from superior to inferior except in the prone position where it was uniform. In the horizontal axis FRCR/TLCR and V/VA were uniformly distributed except for cranial to caudal gradients (with lower values caudally) in supine and lateral decubitus postures. In the prone posture V/VA tended to be higher in caudal lung zones.

Adult↗
PubMed1984

Effect of posture on inter-regional distribution of pulmonary perfusion and VA/Q ratios in man.

Using a gamma camera regional pulmonary perfusion per unit alveolar volume (Q/VA) and ventilation-perfusion ratios (VA/Q) were measured in fourteen normal male volunteers in upright, supine, lateral decubitus, prone and prone suspended postures with inhalation and intravenous infusion of radioactive 81Krm (half-life 13 sec) and inhalation of radioactive 85Krm (half-life 4.4 h). In the vertical axis, Q/VA increased from upper to lower lung regions in upright, lateral decubitus, prone and prone suspended postures but was uniform in supine and within the dependent lung in decubitus postures. Horizontally, Q/VA decreased from cranial to caudal in lateral decubitus, prone suspended, and near the diaphragm in supine. Vertically, VA/Q decreased from upper to lower in all postures except in supine and within the dependent decubitus lung where it increased. VA/Q tended to increase from cranial to caudal in horizontal postures. The effects of gravity on Q/VA and VA/Q vertical distributions are modified when FRC is low (supine, lower decubitus lung) because perfusion is more uniformly distributed. Horizontal gradients of Q/VA and VA/Q are more pronounced under conditions of high local lung volume but also occur in postures where FRC is low.

Adult↗
PubMedDate not supplied

Ocular effects of various laser wavelengths.

Lasers have become an indispensable tool in management of many ocular disorders. This review describes the principles of lasers and the effects various laser modalities and wavelength modalities can produce on ocular structure. Guidelines are provided for appropriate selection of various wavelengths and prevention of complications of the laser treatment.

Argon↗
PubMed1977

The effect of prostaglandin F2alpha on the counter-current transfer of 85krypton in the ovarian pedicle of the sheep.

A miniature Geiger-Müller probe was inserted into the corpus luteum in five anesthetized ewes. A similar probe was inserted into either the lumen of the adjacent fallopian tube or the opposite ovary. Overall, 17 infusions of 85Krypton-saline into the uterine vein were carried out in the five subjects. After each two minute infusion into the uterine vein, an increase in radioactivity was registered in the adjacent corpus luteum within 30 - 60 seconds. Maximum radioactivity was registered 1 - 3 minutes after the start of the infusion and within 10 minutes radioactivity had dropped to background [corrected] levels. In two out of three sheep a similar kpattern of 85Krypton transfer was registered in the adjacent fallopian tube. Only a negligible amount of radioactivity above background level was registered in the contralateral control ovary, a result in keeping with the known rapid clearance of 85Krypton from the circulation. There was no indication of any change in pattern of the counter current transfer of 85Krypton during the infusion of PGF2alpha (10 microng/hr) into the ovarian pedicle. These results suggest that the previously observed slow transfer of PGF2alpha itself in the ovarian pedicle may be due to physical rather than pharmacological properties of this prostaglandin.

Animals↗