Occlusion pressures vs. micropipette pressures in the pulmonary circulation

1989 ◽  
Vol 67 (3) ◽  
pp. 1277-1285 ◽  
Author(s):  
T. S. Hakim ◽  
S. Kelly
Keyword(s):  
Pressure Gradient ◽  
Autologous Blood ◽  
Lower Lobe ◽  
Venous Occlusion ◽  
Pulmonary Capillary ◽  
Large Pressure ◽  
Catheterization Technique ◽  
Large Pressure Gradient ◽  
Occlusion Technique ◽  
Arteries And Veins

Because of the discrepancies between the arterial and venous occlusion technique and the micropuncture technique in estimating pulmonary capillary pressure gradient, we compared measurements made with the two techniques in the same preparations (isolated left lower lobe of dog lung). In addition, we also obtained direct and reliable measurements of pressures in 0.9-mm arteries and veins using a retrograde catheterization technique, as well as a microvascular pressure made with the double-occlusion technique. The following conclusions were made from dog lobes perfused with autologous blood at normal flow rate of 500–600 ml/min and pressure gradient of 12 mmHg. 1) The double-occlusion technique measures pressure in the capillaries, 2) a small pressure gradient (0.5 mmHg) exists between 30- to 50-micron arteries and veins, 3) a large pressure gradient occurs in arteries and veins greater than 0.9 mm, 4) the arterial and venous occlusion techniques measure pressures in vessels that are less than 900 microns diam but greater than 50 microns, very likely close to 100 microns, 5) serotonin constricts arteries (larger and smaller than 0.9 mm) whereas histamine constricts veins (larger and smaller than 0.9 mm). Thus three different techniques (small retrograde catheter, arterial and venous occlusion, and micropuncture) show consistent results, confirming the presence of significant resistance in large arteries and veins with minimal resistance in the microcirculation.

Effects of arachidonate on permeability and resistance distribution in canine lungs

1985 ◽  
Vol 58 (1) ◽  
pp. 206-210 ◽  
Author(s):  
M. I. Townsley ◽  
R. J. Korthuis ◽  
A. E. Taylor
Keyword(s):  
Low Dose ◽  
Constant Pressure ◽  
Autologous Blood ◽  
Venous Occlusion ◽  
High Dose ◽  
Constant Flow ◽  
Pulmonary Capillary ◽  
Pulmonary Capillary Pressure ◽  
Prior Administration ◽  
Lung Lobes

In this study, 14 canine lung lobes were isolated and perfused with autologous blood at constant pressure (CP) or constant flow (CF). Pulmonary capillary pressure (Pc) was measured via venous occlusion or simultaneous arterial and venous occlusions. Arterial and venous pressures and blood flow were measured concurrently so that total pulmonary vascular resistance (RT) as well as pre- (Ra) and post- (Rv) capillary resistances could be calculated. In both CP and CF perfused lobes, 5-min arachidonic acid (AA) infusions (0.085 +/- 0.005 to 2.80 +/- 0.16 mg X min-1 X 100 g lung-1) increased RT, Rv, and Pc (P less than 0.05 at the highest dose), while Ra was not significantly altered and Ra/Rv fell (P less than 0.05 at the highest AA dose). In five CP-perfused lobes, the effect of AA infusion on the pulmonary capillary filtration coefficient (Kf,C) was also determined. Neither low-dose AA (0.167 +/- 0.033 mg X min-1 X 100 g-1) nor high-dose AA (1.35 +/- 0.39 mg X min-1 X 100 g-1) altered Kf,C from control values (0.19 +/- 0.02 ml X min-1 X cmH2O-1 X 100 g-1). The hemodynamic response to AA was attenuated by prior administration of indomethacin (n = 2). We conclude that AA infusion in blood-perfused canine lung lobes increased RT and Pc by increasing Rv and that microvascular permeability is unaltered by AA infusion.

Site of pulmonary hypoxic vasoconstriction studied with arterial and venous occlusion

1983 ◽  
Vol 54 (5) ◽  
pp. 1298-1302 ◽  
Author(s):  
T. S. Hakim ◽  
R. P. Michel ◽  
H. Minami ◽  
H. K. Chang
Keyword(s):  
Flow Rate ◽  
Airway Pressure ◽  
Lower Lobe ◽  
Blood Flow Rate ◽  
Venous Occlusion ◽  
Smooth Muscle Contraction ◽  
Vasoactive Drugs ◽  
Pressure Drops ◽  
Hypoxic Vasoconstriction ◽  
Occlusion Technique

We applied the arterial and venous occlusion technique in an in situ, isolated left lower lobe preparation of a dog lung to compare the effects of hypoxia with the effects of airway pressure elevation, and the infusion of serotonin, norepinephrine, and histamine. The total arteriovenous pressure drop across the lobe was partitioned longitudinally into pressure drops across the relatively indistensible arteries (delta Pa) and veins (delta Pv) and across the middle distensible vessels (delta Pm). Hypoxia increased primarily delta Pm, as did elevation of airway pressure, whereas the vasoactive drugs increased either delta Pa or delta Pv. The increases in pulmonary arterial pressure (Pa) caused by hypoxia and by elevation of airway pressure were independent of blood flow rate, but increases in Pa induced by the vasoactive drugs were dependent on flow rate. We conclude that in the dog hypoxia acts primarily on small distensible vessels, whereas pulmonary vasoactive drugs constrict the relatively indistensible arteries and veins. It is possible that the increase in pulmonary vascular resistance during hypoxia did not involve smooth muscle contraction.

DLO2 in excised lungs perfused with blood containing sodium dithionite (Na2S2O4)

1979 ◽  
Vol 46 (1) ◽  
pp. 100-110 ◽  
Author(s):  
B. Burns ◽  
R. H. Shepard
Keyword(s):  
Autologous Blood ◽  
Lower Lobe ◽  
Compartment Model ◽  
Sodium Dithionite ◽  
Diffusing Capacity ◽  
Lung Weight ◽  
Pulmonary Capillary ◽  
Two Compartment Model ◽  
Pulmonary Capillary Blood ◽  
Experimental Findings

If the excised lung is perfused with blood containing the chemical sodium dithionite (DDT), the PO2 of pulmonary capillary blood is everywhere zero and the membrane diffusing capacity for O2 (DmO2) can be measured by a standard rebreathing technique. The reaction rate of DDT with O2 is not rate limiting in the DmO2. In 15--25 kg dogs anesthetized with pentobarbital sodium (30 mg/kg, iv), left lower lobe was excised, suspended horizontally and perfused with autologous blood at 25--27 degrees C. DDT was added to the blood and the rebreathing alveolar disappearance curves for O2 were measured. The DmO2 ranged from 6 to 43 (ml/min.Torr, STPD) at lung volumes of 240--780 ml (FRC at 6 cmH2O end-expiratory pressure). Lung weight, pulmonary artery pressure, and the DmO2 were stable in the presence of DDT. Histopathology indicates that dithionite in the concentrations used does not harm the lung. Effects of inequalities in the distributions of ventilation, volume, and diffusing capacity were examined in a two-compartment model and compared with the experimental findings.

Pesticide Accidents in Relation to Weather Conditions

1980 ◽  
Vol 7 (3) ◽  
pp. 219-222
Author(s):  
Don Fred ◽  
Edwin Kessler
Keyword(s):  
Wind Speed ◽  
Pressure Gradient ◽  
Strong Relationship ◽  
Weather Conditions ◽  
Strong Positive Correlation ◽  
Slight Tendency ◽  
Positive Correlation ◽  
Large Pressure ◽  
Large Pressure Gradient ◽  
Weak Wind

Research has shown that it is inadvisable to spray crops during either near-absolute calms or very windy conditions; therefore, we studied weather maps and reports of herbicide accidents to investigate the hypothesis that the strong positive correlation between largescale pressure gradient and wind-speed can be used to facilitate prediction of favourable spraying times in Oklahoma. We gave detailed study to the conditions of 10 May 1977, the date in that year when the most herbicide accidents were reported. Although a relatively large pressure gradient existed, there was only weak wind at the KTVY meteorologically instrumented tower (150 km distant from the area of the accidents). We also searched for a strong relationship between herbicide accidents and the pressure gradient through tabulations of daily gradients and accident reports. Only a slight tendency is shown for accidents to occur on days with larger gradients. Research and significant findings for this study were hampered by a lack of specificity and detail in accident reports.

scholarly journals Segmental pulmonary vascular responses to ATP in rat lungs: role of nitric oxide

1997 ◽  
Vol 82 (3) ◽  
pp. 852-858 ◽  
Author(s):  
Tawfic S. Hakim ◽  
Lara Ferrario ◽  
Jeffrey C. Freedman ◽  
Robert E. Carlin ◽  
Enrico M. Camporesi
Keyword(s):  
Nitric Oxide ◽  
Autologous Blood ◽  
Vascular Occlusion ◽  
Dependent Manner ◽  
Vascular Responses ◽  
Rat Lungs ◽  
Occlusion Technique ◽  
Resting Tone ◽  
Arteries And Veins

Hakim, Tawfic S., Lara Ferrario, Jeffrey C. Freedman, Robert E. Carlin, and Enrico M. Camporesi. Segmental pulmonary vascular responses to ATP in rat lungs: role of nitric oxide. J. Appl. Physiol. 82(3): 852–858, 1997.—ATP exhibits vascular pressor and depressor responses in a dose- and tone-dependent manner. The vascular site of ATP-induced contraction or dilation has not previously been characterized. Using the vascular occlusion technique, we investigated the effects of ATP in isolated rat lungs perfused with autologous blood (hematocrit = 20%) and described its action during resting and elevated tone in terms of changes in resistances of the small and large arteries and veins. During resting tone, ATP (10−5M)

Effect of hematocrit on vascular pressure profile in dog lungs

1985 ◽  
Vol 58 (3) ◽  
pp. 743-748 ◽  
Author(s):  
M. Julien ◽  
T. S. Hakim ◽  
R. Vahi ◽  
H. K. Chang
Keyword(s):  
Vascular Resistance ◽  
Lower Lobe ◽  
Blood Flow Rate ◽  
Pressure Profile ◽  
Venous Occlusion ◽  
Longitudinal Distribution ◽  
Middle Segment ◽  
Pressure Drops ◽  
Occlusion Technique

We studied the effect of blood hematocrit (Hct) on the longitudinal distribution of pulmonary vascular pressure profile in an in situ isolated left lower lobe preparation of dog lung using the arterial and venous occlusion technique. The total arteriovenous pressure drop (delta PT) across the lobe was partitioned into pressure drops across an arterial (delta Pa), a venous (delta Pv), and a middle segment (delta Pm). Three levels of Hct were studied: low (18 +/- 5%), normal (41 +/- 4%), and high (66 +/- 5%). Arterial and venous occlusions were performed under constant-flow or constant-pressure perfusion. When flow was maintained constant, the increase in delta PT between low and normal Hct was due to increases in delta Pa, delta Pm, and delta Pv; however, between normal and high Hct, the increase in delta PT was primarily due to an increase in delta Pm. When delta PT was kept constant by adjusting flow, changes in delta Pa and delta Pv were in the same direction as changes in blood flow rate but in opposite direction to changes in Hct. In contrast, changes in delta Pm were in the same direction as changes in Hct. The results showed that the vascular resistance of the middle segment ranged from 7% of total pulmonary vascular resistance at low Hct to 53% at high Hct, suggesting that the vessels within this segment offer the greatest impairment to the transit of blood cells.

Segmental pulmonary vascular resistance in progressive hydrostatic and permeability edema

1985 ◽  
Vol 59 (1) ◽  
pp. 242-247 ◽  
Author(s):  
C. G. Wang ◽  
T. S. Hakim ◽  
R. P. Michel ◽  
H. K. Chang
Keyword(s):  
Vascular Resistance ◽  
Venous Pressure ◽  
Lower Lobe ◽  
Venous Occlusion ◽  
Longitudinal Distribution ◽  
Edema Formation ◽  
Small Rise ◽  
Occlusion Technique ◽  
Isolated Lungs

We used the in situ blood-perfused left lower lobe preparation of the dog to examine the effect of hydrostatic and permeability edema on the slope and intercept of the vascular pressure-flow (P/Q) relationship and on the longitudinal distribution of vascular resistance with the arterial and venous occlusion technique. Hydrostatic edema (HE) was induced by raising the venous pressure, and permeability edema (PE) was induced with alpha-naphthylthiourea. When the hematocrit (Hct) of the perfusate was kept normal (approximately 40%), HE had no significant effect on either the slope or the intercept of the P/Q relationship or on the distribution of vascular resistance. PE caused a small increase in the intercept of the P/Q relationship and a small rise in the resistance of the vessels in the middle segment. In another series of HE experiments in which Hct was allowed to increase during edema formation, there was a marked increase in vascular resistance. We conclude that edema per se does not increase vascular resistance significantly and that the increases in vascular resistance which were observed previously by other investigators in the isolated lungs may be due to increases in blood hematocrit.

Sign in / Sign up

Export Citation Format

Share Document