Microvascular pressures during hypoxia in isolated lungs of newborn rabbits

1988 ◽  
Vol 65 (1) ◽  
pp. 283-287 ◽  
Author(s):  
C. D. Fike ◽  
S. J. Lai-Fook ◽  
R. D. Bland
Keyword(s):  
Blood Flow ◽  
Arterial Pressure ◽  
Airway Pressure ◽  
Left Atrial ◽  
Pulmonary Arterial Pressure ◽  
Hypoxic Conditions ◽  
Hypoxic Vasoconstriction ◽  
Pulmonary Arterial ◽  
Isolated Lungs ◽  
Ventilation Of The Lungs

The purpose of this study was to determine the sites of hypoxic vasoconstriction in lungs of newborn rabbits. We isolated and perfused with blood the lungs from 19 rabbit pups, 7-23 days old. We maintained blood flow constant, continuously monitored pulmonary arterial and left atrial pressures, and alternated ventilation of the lungs with 95% O2-5% CO2 (control), and 95% N2-5% CO2 (hypoxia). Using micropipettes and a servonulling device, we measured pressures in 20-60-micron-diam subpleural arterioles and venules during control and hypoxic conditions. We inflated the lungs to a constant airway pressure of 5-7 cmH2O and kept left atrial pressure greater than airway pressure (zone 3) during micropuncture. In eight lungs we measured microvascular pressures first during control and then during hypoxia. We reversed this order in four lungs. In seven lungs we measured microvascular pressures only during hypoxia. We found a significant increase in pulmonary arterial pressure with no change in microvascular pressures. These results indicate that the site of hypoxic vasoconstriction in lungs of newborn rabbits is arteries greater than 60 micron in diameter.

Pulmonary venous pressure increases during alveolar hypoxia in isolated lungs of newborn pigs

1992 ◽  
Vol 73 (2) ◽  
pp. 552-556 ◽  
Author(s):  
C. D. Fike ◽  
M. R. Kaplowitz
Keyword(s):  
Airway Pressure ◽  
Left Atrial ◽  
Pulmonary Arterial Pressure ◽  
Venous Pressure ◽  
Co2 Gas ◽  
Hypoxic Vasoconstriction ◽  
Alveolar Hypoxia ◽  
Pulmonary Arterial ◽  
Newborn Pigs ◽  
Isolated Lungs

The purpose of this study was to determine whether pulmonary venous pressure increases during alveolar hypoxia in lungs of newborn pigs. We isolated and perfused with blood the lungs from seven newborn pigs, 6–7 days old. We maintained blood flow constant at 50 ml.min-1.kg-1 and continuously monitored pulmonary arterial and left atrial pressures. Using the micropuncture technique, we measured pressures in 10 to 60-microns-diam venules during inflation with normoxic (21% O2–69–74% N2–5–10% CO2) and hypoxic (90–95% N2–5–10% CO2) gas mixtures. PO2 was 142 +/- 21 Torr during normoxia and 20 +/- 4 Torr during hypoxia. During micropuncture we inflated the lungs to a constant airway pressure of 5 cmH2O and kept left atrial pressure greater than airway pressure (zone 3). During hypoxia, pulmonary arterial pressure increased by 69 +/- 24% and pressure in small venules increased by 40 +/- 23%. These results are similar to those obtained with newborn lambs and ferrets but differ from results with newborn rabbits. The site of hypoxic vasoconstriction in newborn lungs is species dependent.

Pulmonary arterial and venous constriction during hypoxia in 3- to 5-wk-old and adult ferrets

1990 ◽  
Vol 69 (6) ◽  
pp. 2183-2189 ◽  
Author(s):  
J. U. Raj ◽  
R. Hillyard ◽  
P. Kaapa ◽  
M. Gropper ◽  
J. Anderson
Keyword(s):  
Blood Flow ◽  
Pressure Drop ◽  
Left Atrial ◽  
Pulmonary Arterial Pressure ◽  
Venous Pressure ◽  
Pressure Profile ◽  
Fluid Filtration ◽  
Pressure Drops ◽  
Hypoxic Vasoconstriction ◽  
Pulmonary Arterial

We have determined the sites of hypoxic vasoconstriction in ferret lungs. Lungs of five 3- to 5-wk-old and five adult ferrets were isolated and perfused with blood. Blood flow was adjusted initially to keep pulmonary arterial pressure at 20 cmH2O and left atrial and airway pressures at 6 and 8 cmH2O, respectively (zone 3). Once adjusted, flow was kept constant throughout the experiment. In each lung, pressures were measured in subpleural 20- to 50-microns-diam arterioles and venules with the micropipette servo-nulling method during normoxia (PO2 approximately 100 Torr) and hypoxia (PO2 less than 50 Torr). In normoxic adult ferret lungs, approximately 40% of total vascular resistance was in arteries, approximately 40% was in microvessels, and approximately 20% was in veins. With hypoxia, the total arteriovenous pressure drop increased by 68%. Arterial and venous pressure drops increased by 92 and 132%, respectively, with no change in microvascular pressure drop. In 3- to 5-wk-old ferret lungs, the vascular pressure profile during normoxia and the response to hypoxia were similar to those in adult lungs. We conclude that, in ferret lungs, arterial and venous resistances increase equally during hypoxia, resulting in increased microvascular pressures for fluid filtration.

Developmental differences in vascular responses to hypoxia in lungs of rabbits

1994 ◽  
Vol 77 (2) ◽  
pp. 507-516 ◽  
Author(s):  
C. D. Fike ◽  
M. R. Kaplowitz
Keyword(s):  
Arterial Pressure ◽  
Left Atrial ◽  
Pulmonary Arterial Pressure ◽  
Developmental Differences ◽  
Age Group ◽  
Co2 Gas ◽  
Micropuncture Technique ◽  
Age Related ◽  
Hypoxic Vasoconstriction ◽  
Pulmonary Arterial

Our purpose was to determine whether postnatal age and prostaglandins influence the sites of hypoxic vasoconstriction in lungs of rabbits. To do this, we used the micropuncture technique to measure pressures in 20- to 80-microns-diam subpleural arterioles and venules during sequential inflation of lungs of newborn and adult rabbits with normoxic (21% O2–7–10% CO2–69–72% N2) and hypoxic (90–93% N2–7–10% CO2) gas mixtures. Indomethacin (40 micrograms/ml) was added to the perfusate of some lungs of each age group. During hypoxia in untreated lungs of newborn rabbits, both pulmonary arterial and 20- to 80-microns-diam arteriolar pressure increased by 5%, whereas 20- to 80-microns-diam venular pressure remained the same. In contrast, during hypoxia in untreated lungs of adult rabbits, pulmonary arterial pressure increased by 48%, whereas 20- to 80-microns-diam arteriolar pressure decreased slightly and 20- to 80-microns-diam venular pressure did not change. Regardless of the presence of indomethacin, location of vessels used for micropuncture, or level of left atrial pressure, pulmonary arterial pressure was the only measured vascular pressure that increased with hypoxia in adult lungs. Thus, in adult lungs, the site of hypoxia-induced vasoconstriction was limited to arteries > 80 microns diam, whereas in newborn lungs the site of hypoxia-induced vasoconstriction included vessels both larger and smaller than 20- to 80-microns-diam arteries. This age-related difference in the sites of hypoxia-induced vasoconstriction was not found in indomethacin-treated lungs.

Regional pulmonary blood flow during 96 hours of hypoxia in conscious sheep

1986 ◽  
Vol 61 (6) ◽  
pp. 2136-2143 ◽  
Author(s):  
D. C. Curran-Everett ◽  
K. McAndrews ◽  
J. A. Krasney
Keyword(s):  
Blood Flow ◽  
Arterial Pressure ◽  
Pulmonary Blood Flow ◽  
Pulmonary Arterial Pressure ◽  
Pressor Response ◽  
Superior Vena ◽  
Acute Hypoxia ◽  
Vena Cava ◽  
Normobaric Hypoxia ◽  
Pulmonary Arterial

The effects of acute hypoxia on regional pulmonary perfusion have been studied previously in anesthetized, artificially ventilated sheep (J. Appl. Physiol. 56: 338–342, 1984). That study indicated that a rise in pulmonary arterial pressure was associated with a shift of pulmonary blood flow toward dorsal (nondependent) areas of the lung. This study examined the relationship between the pulmonary arterial pressor response and regional pulmonary blood flow in five conscious, standing ewes during 96 h of normobaric hypoxia. The sheep were made hypoxic by N2 dilution in an environmental chamber [arterial O2 tension (PaO2) = 37–42 Torr, arterial CO2 tension (PaCO2) = 25–30 Torr]. Regional pulmonary blood flow was calculated by injecting 15-micron radiolabeled microspheres into the superior vena cava during normoxia and at 24-h intervals of hypoxia. Pulmonary arterial pressure increased from 12 Torr during normoxia to 19–22 Torr throughout hypoxia (alpha less than 0.049). Pulmonary blood flow, expressed as %QCO or ml X min-1 X g-1, did not shift among dorsal and ventral regions during hypoxia (alpha greater than 0.25); nor were there interlobar shifts of blood flow (alpha greater than 0.10). These data suggest that conscious, standing sheep do not demonstrate a shift in pulmonary blood flow during 96 h of normobaric hypoxia even though pulmonary arterial pressure rises 7–10 Torr. We question whether global hypoxic pulmonary vasoconstriction is, by itself, beneficial to the sheep.

Flow through zone 1 lungs utilizes alveolar corner vessels

1991 ◽  
Vol 70 (4) ◽  
pp. 1518-1523 ◽  
Author(s):  
W. J. Lamm ◽  
K. R. Kirk ◽  
W. L. Hanson ◽  
W. W. Wagner ◽  
R. K. Albert
Keyword(s):  
Arterial Pressure ◽  
Pulmonary Arterial Pressure ◽  
Left Lung ◽  
Lateral Position ◽  
Double Lumen Endotracheal Tube ◽  
Mean Pulmonary Arterial Pressure ◽  
Flow Through ◽  
Pulmonary Arterial ◽  
Isolated Lungs

We have previously observed flows equivalent to 15% of the resting cardiac output of rabbits occurring through isolated lungs that were completely in zone 1. To distinguish between alveolar corner vessels and alveolar septal vessels as a possible zone 1 pathway, we made in vivo microscopic observations of the subpleural alveolar capillaries in five anesthetized dogs. Videomicroscopic recordings were made via a transparent thoracic window with the animal in the right lateral position. From recordings of the uppermost surface of the left lung, alveolar septal and corner vessels were classified depending on whether they were located within or between alveoli, respectively. Observations were made with various levels of positive end-expiratory pressure (PEEP) applied only to the left lung via a double-lumen endotracheal tube. Consistent with convention, flow through septal vessels stopped when PEEP was raised to the mean pulmonary arterial pressure (the zone 1-zone 2 border). However, flow through alveolar corner vessels continued until PEEP was 8-16 cmH2O greater than mean pulmonary arterial pressure (8-16 cm into zone 1). These direct observations support the idea that alveolar corner vessels rather than patent septal vessels provide the pathway for blood flow under zone 1 conditions.

The response of the pulmonary circulation to exercise during normoxia and hypoxia following pneumonectomy in the adult sheep

1989 ◽  
Vol 67 (3) ◽  
pp. 202-206 ◽  
Author(s):  
Michele Smith ◽  
Geoffrey Coates ◽  
J. Michael Kay ◽  
Hugh O'Brodovich
Keyword(s):  
Blood Flow ◽  
Arterial Pressure ◽  
Pulmonary Arterial Pressure ◽  
Hemodynamic Response ◽  
Pulmonary Hemodynamics ◽  
Vascular Reserve ◽  
Mean Pulmonary Arterial Pressure ◽  
Pulmonary Hemodynamic ◽  
Pulmonary Arterial ◽  
Increased Blood Flow

Pneumonectomy approximately halves the available pulmonary vascular bed. It is unknown whether the remaining lung has sufficient vascular reserve to cope with increased blood flow under stressful conditions without demonstrating abnormal pulmonary hemodynamics. To investigate this question, unanesthetized ewes with vascular catheters had hemodynamics assessed before and after a left pneumonectomy. Subsequently, on different days, the sheep were exercised on a treadmill under normoxic and hypobaric hypoxic (430 mmHg) (1 mmHg = 133.3 Pa) conditions. Pneumonectomy itself increased mean pulmonary arterial pressure by 4 mmHg. During normoxic or hypoxic exercise, the pneumonectomized sheep demonstrated a pulmonary hemodynamic response similar to normal sheep with two lungs. The pressure–flow relation for the right lung suggested the vascular reserve of the lung was not exceeded during exercise in the pneumonectomized sheep. Eighteen to 70 days after pneumonectomy there was no evidence of right ventricular hypertrophy, but there were small increases in the number of muscularized vessels less than 50 μm diameter and in the amount of muscle in normally muscularized pulmonary arteries. This study demonstrates that pneumonectomy slightly increases mean pulmonary arterial pressure. However, there is sufficient vascular reserve in the remaining lung to permit a normal hemodynamic response to exercise-induced increased blood flow even under hypoxic conditions.Key words: pulmonary hypertension, pneumonectomy, sheep.

Hypoxic pulmonary vasoconstriction during steady and pulsatile flow in ferrets

1984 ◽  
Vol 57 (1) ◽  
pp. 205-212 ◽  
Author(s):  
T. J. Gregory ◽  
M. L. Ellsworth ◽  
J. C. Newell
Keyword(s):  
Arterial Pressure ◽  
Steady Flow ◽  
Pulsatile Flow ◽  
Airway Pressure ◽  
Pulmonary Arterial Pressure ◽  
Pressor Response ◽  
Flow Curves ◽  
Mean Pulmonary Arterial Pressure ◽  
Pulmonary Arterial ◽  
Pulsatile Perfusion

We examined the effects of hypoxia and pulsatile flow on the pressure-flow relationships in the isolated perfused lungs of Fitch ferrets. When perfused by autologous blood from a pump providing a steady flow of 60 ml/min, the mean pulmonary arterial pressure rose from 14.6 to 31.3 Torr when alveolarPO2 was reduced from 122 to 46 Torr. This hypoxic pressor response was characterized by a 10.1-Torr increase in the pressure-axis intercept of the extrapolated pressure-flow curves and an increase in the slope of these curves from 130 to 240 Torr X l–1 X min. With pulsatile perfusion from a piston-typepump, mean pulmonary arterial pressure increased from 17.5 to 36.3 Torr at the same mean flow.Thishypoxic pressor response was also characterized by increases in the intercept pressure and slope of thepressure-flow curves. When airway pressure was raised during hypoxia, the intercept pressure increased further to 25 +/- 1 Torr with a further increase in vascular resistance to 360 Torr X l–1 X min. Thus, in contrast to the dog lung, in the ferret lung pulsatile perfusion does not result in lower perfusion pressures during hypoxia when compared with similar mean levels of steady flow. Since the effects of high airway pressure and hypoxia are additive, they appear to act at or near the same site in elevating perfusion pressure.

Effects of left atrial pressure on the pulmonary vascular response to hypoxic ventilation

1991 ◽  
Vol 70 (5) ◽  
pp. 1991-1995 ◽  
Author(s):  
S. A. Gu ◽  
J. Ducas ◽  
U. Schick ◽  
R. M. Prewitt
Keyword(s):  
Arterial Pressure ◽  
Left Atrial ◽  
Pulmonary Arterial Pressure ◽  
Mean Value ◽  
Atrial Pressure ◽  
Left Atrial Pressure ◽  
Vascular Response ◽  
Wide Range ◽  
Pulmonary Arterial ◽  
The Mean

We investigated the effects of hypoxic ventilation on the pulmonary arterial pressure- (P) flow (Q) relationship in an intact canine preparation. Mean pulmonary P-Q coordinates were obtained during hypoxic ventilation and during ventilation with 100% O2 at normal and at increased left atrial pressure. Specifically, we tested the hypothesis that, over a wide range, changes in left atrial pressure would alter the effects of hypoxic ventilation on pulmonary P-Q characteristics. Seven dogs were studied. When left atrial pressure was normal (5 mmHg), the mean value of the extrapolated intercept (PI) of the linear P-Q relationship was 10.9 mmHg and the slope (incremental vascular resistance, IR) of the P-Q relationship was 2.2 mmHg.l-1.min. Hypoxic ventilation increased PI to 18 mmHg (P less than 0.01) but did not affect IR. Subsequently, during ventilation with 100% O2, when left atrial pressure was increased to 14 mmHg by inflation of left atrial balloon, PI increased to 18 mmHg. IR was 1.6 mmHg.l-1.min. Again, hypoxic ventilation caused an isolated change in PI. Hypoxia increased PI from 18 to 28 mmHg (P less than 0.01). As in the condition of normal left atrial pressure, hypoxic ventilation did not affect IR. We conclude that, in an anesthetized intact canine preparation, hypoxic ventilation causes an isolated increase in the extrapolated pressure intercept of the pulmonary P-Q relationship. Furthermore the effects of hypoxic ventilation on pulmonary P-Q characteristics are not affected by the resting left atrial pressure.

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