Regional differences in gas exchange in the lung of erect man

1962 ◽  
Vol 17 (6) ◽  
pp. 893-898 ◽  
Author(s):  
J. B. West
Keyword(s):  
Blood Flow ◽  
Gas Exchange ◽  
Lung Volume ◽  
Regional Differences ◽  
Capillary Blood ◽  
O2 Uptake ◽  
Regional Ventilation ◽  
Ventilation Perfusion Ratio ◽  
Ph Variations

Measurements of regional ventilation and blood flow using radioactive CO2 show that both increase from apex to base of the lung; the results are used to build an integrated picture of gas exchange. Ventilation-perfusion ratios at nine levels of the lung have been calculated and differences in local gas exchange deduced. In the resulting model, alveolar O2 tension changes by more than 40 mm Hg from apex to base while CO2 and N2 tensions change by about 14 and 29 mm Hg, respectively. Maximal differences in O2 saturation of end-capillary blood are 4% but differences in CO2 contents of 7 vol % and pH variations of 0.12 units occur. The O2 uptake per unit lung volume increases eightfold down the lung while corresponding variations in CO2 output are less than threefold. N2 passes out of the blood in upper parts of the lung but into the blood in basal regions (net exchange is zero). Over-all O2 uptake and CO2 outputs are reduced by only 2–3% by the ventilation-perfusion ratio inequality, causing alveolar-arterial differences of 4, 1, and 3 mm Hg for O2, CO2, and N2, respectively. Submitted on April 6, 1962

Temporal course of gas exchange and mechanical compensation after right pneumonectomy in immature dogs

1996 ◽  
Vol 80 (4) ◽  
pp. 1304-1312 ◽  
Author(s):  
S. Takeda ◽  
E. Y. Wu ◽  
M. Ramanathan ◽  
A. S. Estrera ◽  
C. C. Hsia
Keyword(s):  
Blood Flow ◽  
Gas Exchange ◽  
Lung Volume ◽  
Pulmonary Blood Flow ◽  
Capillary Blood ◽  
Diffusing Capacity ◽  
Pulmonary Capillary ◽  
Capillary Blood Volume ◽  
Pulmonary Capillary Blood ◽  
Pulmonary Capillary Blood Volume

To determine the temporal progression and magnitude of functional compensation in immature dogs raised to maturity after extensive lung resection, we performed right pneumonectomy (R-Pnx) or right thoracotomy without pneumonectomy (Sham) in matched foxhounds at 2 mo of age. At 4, 8, 20, 40, and 60 wk after surgery, static transpulmonary pressure-lung volume relationships were determined. Lung diffusing capacity, membrane diffusing capacity, pulmonary capillary blood volume, pulmonary blood flow, septal lung tissue volume, and lung volumes were measured simultaneously by a rebreathing technique. During maturation, total lung capacity, lung volume at a given distending pressure, and compliance were lower in the R-Pnx group than in the Sham group (P < 0.05). Pulmonary viscous resistance at maturity was elevated after R-Pnx. There were no significant differences in total lung diffusing capacity, membrane diffusing capacity, pulmonary capillary blood volume, pulmonary blood flow, and septal lung tissue volume between groups. Compensation of alveolar-capillary gas exchange was complete by 4-8 wk after R-Pnx, but compensation of mechanical properties remained incomplete throughout maturation. Relative magnitude of compensation after R-Pnx was greater in immature dogs than in adult dogs studied previously by similar techniques.

Ventilation-perfusion inequality during constant-flow ventilation

1987 ◽  
Vol 62 (3) ◽  
pp. 1255-1263 ◽  
Author(s):  
P. T. Schumacker ◽  
J. I. Sznajder ◽  
A. Nahum ◽  
L. D. Wood
Keyword(s):  
Blood Flow ◽  
Gas Exchange ◽  
Lung Volume ◽  
Intermittent Positive Pressure Ventilation ◽  
Positive Pressure ◽  
Asymmetric Distribution ◽  
Constant Flow ◽  
Arterial Pco2 ◽  
Continuous Stream ◽  
Anesthetized Dogs

Previous work by Lehnert et al. (J. Appl. Physiol. 53:483–489, 1982) has demonstrated that adequate alveolar ventilation can be maintained during apnea in anesthetized dogs by delivering a continuous stream of inspired ventilation through cannulas aimed down the main-stem bronchi. Because an asymmetric distribution of ventilation might introduce ventilation-perfusion (VA/Q) inequality, we compared gas exchange efficiency in nine anesthetized and paralyzed dogs during constant-flow ventilation (CFV) and conventional ventilation (intermittent positive-pressure ventilation, IPPV). Gas exchange was assessed using the multiple inert gas elimination technique. During CFV at 3 l X kg-1 X min-1, lung volume, retention-excretion differences (R-E*) for low- and medium-solubility gases, and the log standard deviation of blood flow (log SD Q) increased, compared with the findings during IPPV. Reducing CFV flow rate to 1 l X kg-1 X min-1 at constant lung volume improved R-E* and log SD Q, but significant VA/Q inequality compared with that at IPPV remained and arterial PCO2 rose. Comparison of IPPV and CFV at the same mean lung volume showed a similar reversible deterioration in gas exchange efficiency during CFV. We conclude that CFV causes significant VA/Q inequality which may be due to nonuniform ventilation distribution and a redistribution of pulmonary blood flow.

Analysis of the effects of pulsatile capillary blood flow and volume on gas exchange

1978 ◽  
Vol 35 (1) ◽  
pp. 27-42 ◽  
Author(s):  
A. Bidani ◽  
R.W. Flumerfelt ◽  
E.D. Crandall
Keyword(s):  
Blood Flow ◽  
Gas Exchange ◽  
Capillary Blood ◽  
Capillary Blood Flow

scholarly journals THE EFFECTS OF POSTURE ON CAPILLARY BLOOD FLOW PULSE AND GAS EXCHANGE IN THE LUNGS OF MAN

1980 ◽  
Vol 44 (5) ◽  
pp. 327-333 ◽  
Author(s):  
YOSHIKAZU KAWAKAMI ◽  
AKIRA SHIDA ◽  
MAKOTO MURAO
Keyword(s):  
Blood Flow ◽  
Gas Exchange ◽  
Capillary Blood ◽  
Capillary Blood Flow ◽  
Flow Pulse

Effect of posture on regional gas exchange in pigs

2004 ◽  
Vol 97 (6) ◽  
pp. 2104-2111 ◽  
Author(s):  
William A. Altemeier ◽  
Steve McKinney ◽  
Melissa Krueger ◽  
Robb W. Glenny
Keyword(s):  
Blood Flow ◽  
Gas Exchange ◽  
Oxygen Tension ◽  
Regional Blood Flow ◽  
Flow Distribution ◽  
Regional Ventilation ◽  
Total Blood ◽  
Ventilation Heterogeneity ◽  
Alveolar Oxygen ◽  
Ventilation And Perfusion

Although recent high-resolution studies demonstrate the importance of nongravitational determinants for both pulmonary blood flow and ventilation distributions, posture has a clear impact on whole lung gas exchange. Deterioration in arterial oxygenation with repositioning from prone to supine posture is caused by increased heterogeneity in the distribution of ventilation-to-perfusion ratios. This can result from increased heterogeneity in regional blood flow distribution, increased heterogeneity in regional ventilation distribution, decreased correlation between regional blood flow and ventilation, or some combination of the above (Wilson TA and Beck KC, J Appl Physiol 72: 2298–2304, 1992). We hypothesize that, although repositioning from prone to supine has relatively small effects on overall blood flow and ventilation distributions, regional changes are poorly correlated, resulting in regional ventilation-perfusion mismatch and reduction in alveolar oxygen tension. We report ventilation and perfusion distributions in seven anesthetized, mechanically ventilated pigs measured with aerosolized and injected microspheres. Total contributions of pulmonary structure and posture on ventilation and perfusion heterogeneities were quantified by using analysis of variance. Regional gradients of posture-mediated change in ventilation, perfusion, and calculated alveolar oxygen tension were examined in the caudocranial and ventrodorsal directions. We found that pulmonary structure was responsible for 74.0 ± 4.7% of total ventilation heterogeneity and 63.3 ± 4.2% of total blood flow heterogeneity. Posture-mediated redistribution was primarily oriented along the caudocranial axis for ventilation and along the ventrodorsal axis for blood flow. These mismatched changes reduced alveolar oxygen tension primarily in the dorsocaudal lung region.

Imaging regional PaO2 and gas exchange

2012 ◽  
Vol 113 (2) ◽  
pp. 340-352 ◽  
Author(s):  
Johan Petersson ◽  
Robb W. Glenny
Keyword(s):  
Blood Flow ◽  
Gas Exchange ◽  
Spatial Resolution ◽  
Photon Emission ◽  
Repeated Measurements ◽  
Emission Computed Tomography ◽  
Regional Ventilation ◽  
Imaging Methods ◽  
Stage Of Development ◽  
Ventilation And Perfusion

Several methods allow regional gas exchange to be inferred from imaging of regional ventilation and perfusion (V/Q) ratios. Each method measures slightly different aspects of gas exchange and has inherent advantages and drawbacks that are reviewed. Single photon emission computed tomography can provide regional measure of ventilation and perfusion from which regional V/Q ratios can be derived. PET methods using inhaled or intravenously administered nitrogen-13 provide imaging of both regional blood flow, shunt, and ventilation. Electric impedance tomography has recently been refined to allow simultaneous measurements of both regional ventilation and blood flow. MRI methods utilizing hyperpolarized helium-3 or xenon-129 are currently being refined and have been used to estimate local PaO2 in both humans and animals. Microsphere methods are included in this review as they provide measurements of regional ventilation and perfusion in animals. One of their advantages is their greater spatial resolution than most imaging methods and the ability to use them as gold standards against which new imaging methods can be tested. In general, the reviewed methods differ in characteristics such as spatial resolution, possibility of repeated measurements, radiation exposure, availability, expensiveness, and their current stage of development.

Lutein Complex Supplementation Increases Ocular Blood Flow Biomarkers in Healthy Subjects

2019 ◽  
Vol 89 (1-2) ◽  
pp. 5-12
Author(s):  
Alon Harris ◽  
Brent Siesky ◽  
Amelia Huang ◽  
Thai Do ◽  
Sunu Mathew ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Blood Flow ◽  
Diastolic Blood Pressure ◽  
Healthy Subjects ◽  
Ocular Blood Flow ◽  
Capillary Blood ◽  
Post Treatment ◽  
Capillary Blood Flow ◽  
Doppler Imaging ◽  
Retinal Capillary

Abstract. Introduction: To investigate the effects of a lutein complex supplementation on ocular blood flow in healthy subjects. Materials and Methods: Sixteen healthy female patients (mean age 36.8 ± 12.1 years) were enrolled in this randomized, placebo-controlled, double-blinded, two-period crossover study. Subjects received daily an oral dose of the lutein with synergistic phytochemicals complex (lutein (10 mg), ascorbic acid (500 mg), tocopherols (364 mg), carnosic acid (2.5 mg), zeaxanthin (2 mg), copper (2 mg), with synergistic effects in reducing pro-inflammatory mediators and cytokines when administered together in combination) and placebo during administration periods. Measurements were taken before and after three-week supplementation periods, with crossover visits separated by a three-week washout period. Data analysis included blood pressure, heart rate, intraocular pressure, visual acuity, contrast sensitivity detection, ocular perfusion pressure, confocal scanning laser Doppler imaging of retinal capillary blood flow, and Doppler imaging of the retrobulbar blood vessels. Results: Lutein complex supplementation produced a statistically significant increase in mean superior retinal capillary blood flow, measured in arbitrary units (60, p = 0.0466) and a decrease in the percentage of avascular area in the superior (−0.029, p = 0.0491) and inferior (−0.023, p = 0.0477) retina, as well as reduced systolic (−4.06, p = 0.0295) and diastolic (−3.69, p = 0.0441) blood pressure measured in mmHg from baseline. Data comparison between the two supplement groups revealed a significant decrease in systemic diastolic blood pressure (change from pre- to post-treatment with lutein supplement (mean (SE)): −3.69 (1.68); change from pre- to post-treatment with placebo: 0.31 (2.57); p = 0.0357) and a significant increase in the peak systolic velocity (measured in cm/sec) in the central retinal artery (change from pre- to post-treatment with lutein supplement: 0.36 (0.19); change from pre- to post-treatment with placebo: −0.33 (0.21); p = 0.0384) with lutein complex supplement; data analyses from the placebo group were all non-significant. Discussion: In healthy participants, oral administration of a lutein phytochemicals complex for three weeks produced increased ocular blood flow biomarkers within retinal vascular beds and reduced diastolic blood pressure compared to placebo.

Sign in / Sign up

Export Citation Format

Share Document