scholarly journals High-resolution spatial measurements of ventilation-perfusion heterogeneity in rats

2010 ◽  
Vol 108 (5) ◽  
pp. 1395-1401 ◽  
Author(s):  
H. Thomas Robertson ◽  
Melissa A. Krueger ◽  
Wayne J. E. Lamm ◽  
Robb W. Glenny
Keyword(s):  
High Resolution ◽  
Regional Blood Flow ◽  
Laboratory Animals ◽  
Fluorescence Signal ◽  
Method Error ◽  
Mechanically Ventilated ◽  
Before And After ◽  
The Mean ◽  
Induced Changes ◽  
High Resolution Method

This study was designed to validate a high-resolution method to measure regional ventilation (V̇a) in small laboratory animals, and to compare regional V̇a and perfusion (Q̇) before and after methacholine-induced bronchoconstriction. A mixture of two different colors of 0.04-μm fluorescent microspheres (FMS) was aerosolized and administered to five anesthetized, mechanically ventilated rats. Those rats also received an intravenous injection of a mixture of two different colors of 15-μm FMS to measure regional blood flow (Q̇). Five additional rats were labeled with aerosol and intravenous FMS, injected with intravenous methacholine, and then relabeled with a second pair of aerosol and intravenous FMS colors. After death, the lungs were reinflated, frozen, and sequentially sliced in 16-μm intervals on an imaging cryomicrotome set to acquire signal for each of the FMS colors. The reconstructed lung images were sampled using randomly placed 3-mm radius spheres. V̇a within each sphere was estimated from the aerosol fluorescence signal, and Q̇ was estimated from the number of 15-μm FMS within each sphere. Method error ranged from 6 to 8% for Q̇ and 0.5 to 4.0% for V̇a. The mean coefficient of variation for Q̇ was 17%, and for V̇a was 34%. The administration of methacholine altered the distribution of both V̇a and Q̇ within lung regions, with a change in V̇a distribution nearly twice as large as that seen for Q̇. The methacholine-induced changes in V̇a were not associated with compensatory shifts in Q̇. Cryomicrotome images of FMS markers provide a high-resolution, anatomically specific means of measuring regional V̇a/Q̇ responses in the rat.

OCT-Angiography as a reliable prognostic tool in laser-treated proliferative diabetic retinopathy: The RENOCTA Study

2020 ◽  
pp. 112067212096345
Author(s):  
Marco Lupidi ◽  
Ramkailash Gujar ◽  
Alessio Cerquaglia ◽  
Jay Chhablani ◽  
Daniela Fruttini ◽  
...  
Keyword(s):  
Diabetic Retinopathy ◽  
Proliferative Diabetic Retinopathy ◽  
Additional Treatment ◽  
Post Treatment ◽  
Vascular Perfusion ◽  
Significant Difference ◽  
Before And After ◽  
The Mean ◽  
Pre Treatment ◽  
Induced Changes

Purpose: To quantitatively assess retinal neovascularizations (RNVs) in proliferative diabetic retinopathy (PDR) before and after photocoagulative laser treatment (PLT) using Optical Coherence Tomography Angiography (OCT-A). Methods: Consecutive patients with PDR were examined with fluorescein angiography (FA) and OCT-A before and after PLT. Baseline and after-treatment FA images were quantitatively analyzed to assess both the RNVs area and leakage area. On OCT-A RNVs area, vascular perfusion density (VPD), vessel length density (VLD) and fractal dimension were computed. VPD of the full-retina OCT-A underneath the RNV was determined to evaluate potential laser-induced changes in vascular perfusion. Results: Fifteen eyes of 13 patients with PDR were enrolled. The mean area of the RNVs was 0.47 ± 0.50 mm2 in the baseline OCT-A and 0.32 ± 0.40 mm2 in the post-treatment assessment ( p = 0.0002). The mean RNV VPD of RNV was 2% ± 4% in pre-treatment and 1% ± 1% for the post-treatment ( p = 0.0001). The mean VLD of RNV was 7.26 ± 1.53 at baseline and 6.64 ± 1.65 in the post treatment ( p = 0.0002). A significant difference in terms of mean RNVs area and VPD reduction between eyes that needed additional treatment and those that did not (~40% vs ~20%; p < 0.05), was observed. Mean VPD of full-retinal thickness OCT-angiogram was 55% ± 10% for the pre-treatment and 53% ± 8% for the post treatment scan ( p = 0.02). Conclusion: The quantitative OCT-A assessment of laser-induced changes of RNVs can be a useful non-invasive approach for determining treatment efficacy. A reduction of RNVs area or VPD ⩾ 40% might reveal those eyes that won’t require additional treatment. Retinal perfusion impairment seemed to progress independently from the treatment.

Vascular and airway effects of endogenous cyclooxygenase products during lung inflation

1985 ◽  
Vol 59 (3) ◽  
pp. 884-889 ◽  
Author(s):  
H. Baier ◽  
L. Yerger ◽  
R. Moas ◽  
A. Wanner
Keyword(s):  
Transpulmonary Pressure ◽  
Mean Value ◽  
Base Line ◽  
Pulmonary Resistance ◽  
Flow Probe ◽  
Lung Inflation ◽  
Mechanically Ventilated ◽  
Before And After ◽  
Electromagnetic Flow Probe ◽  
Induced Changes

The influence of lung inflation on lung elasticity and pulmonary resistance (RL) and on pulmonary and bronchial hemodynamics was examined in five anesthetized, mechanically ventilated adult sheep before and after treatment with the cyclooxygenase inhibitor indomethacin (2 mg/kg). Lung inflation was accomplished by increasing levels of positive end-expiratory pressure (PEEP). Measurements of pulmonary vascular resistance (PVR), bronchial blood flow (Qbr), and RL were obtained with a Swan-Ganz catheter, with an electromagnetic flow probe placed around the carinal artery, and by relating airflow to transpulmonary pressure (Ptp), respectively. Before indomethacin, increasing PEEP from 5 to 15 cmH2O increased mean lung volume (VL) to 135% (P less than 0.01), Ptp to 165% (P less than 0.005), and PVR to 132% (P less than 0.05) of base line and decreased mean Qbr (normalized for cardiac output) to 53% (P less than 0.05) of base line. Mean RL showed a tendency to decrease with a mean value of 67% of base line at 15 cmH2O PEEP. After indomethacin the corresponding values were 121% for VL, 155% for Ptp, 124% for PVR, 35% for Qbr, and 31% for RL. The PEEP-dependent changes were not different before and after indomethacin except for mean VL, which increased less (P less than 0.05) after indomethacin. The failure of indomethacin to modify PEEP-induced changes in RL, PVR, and Qbr was also present when these parameters were expressed as a function of Ptp. These findings suggest that the cyclooxygenase products elaborated during lung inflation reduce lung elasticity but fail to influence airflow resistance and pulmonary and bronchial hemodynamics.

Pulmonary embolization causes hypoxemia by redistributing regional blood flow without changing ventilation

1998 ◽  
Vol 85 (6) ◽  
pp. 2337-2343 ◽  
Author(s):  
William A. Altemeier ◽  
H. Thomas Robertson ◽  
Steve McKinney ◽  
Robb W. Glenny
Keyword(s):  
Blood Flow ◽  
Regional Blood Flow ◽  
Alveolar Ventilation ◽  
Regional Perfusion ◽  
Regional Ventilation ◽  
Fluorescent Microspheres ◽  
Mechanically Ventilated ◽  
Before And After ◽  
Pulmonary Embolization ◽  
Ventilation And Perfusion

To explore mechanisms of hypoxemia after acute pulmonary embolism, we measured regional pulmonary blood flow and alveolar ventilation before and after embolization with 780-μm beads in five anesthetized, mechanically ventilated pigs. Regional ventilation and perfusion were determined in ∼2.0-cm3 lung volumes by using 1-μm-diameter aerosolized and 15-μm-diameter injected fluorescent microspheres. Hypoxemia after embolization resulted from increased perfusion to regions with low ventilation-to-perfusion ratios. Embolization caused an increase in perfusion heterogeneity and a fall in the correlation between ventilation and perfusion. Correlation between regional ventilation pre- and postembolization was greater than correlation between regional perfusion pre- and postembolization. The majority of regional ventilation-to-perfusion ratio heterogeneity was attributable to changes in regional perfusion. Regional perfusion redistribution without compensatory changes in regional ventilation is responsible for hypoxemia after pulmonary vascular embolization in pigs.

Temporal profile of vascular changes induced by systemic nitroglycerin in the meningeal and cortical districts

Cephalalgia ◽  
2010 ◽  
Vol 31 (2) ◽  
pp. 190-198 ◽  
Author(s):  
Rosaria Greco ◽  
Cristina Meazza ◽  
Antonina Stefania Mangione ◽  
Marta Allena ◽  
Monica Bolla ◽  
...  
Keyword(s):  
Blood Flow ◽  
Regional Blood Flow ◽  
Sprague Dawley ◽  
No Donor ◽  
Doppler Flowmetry ◽  
Additional Information ◽  
Sprague Dawley Rats ◽  
Before And After ◽  
Pre Treatment ◽  
Induced Changes

Background: Clinical studies indicated that nitric oxide (NO) donors cause regional changes in cerebral blood flow (CBF), similar to those reported in spontaneous migraine. Systemic nitroglycerin (NTG), a NO donor, is a well-accepted experimental model of migraine. In this study we have examined the effects of NTG on the meningeal and cortical blood flow in rats. Methods: Regional blood flow was monitored in male Sprague-Dawley rats using laser Doppler flowmetry before and after NTG/saline injection over 150 minutes. The effect of pre-treatment with Nω-nitro-L-arginine ester (L-NAME) or 7-nitroindazole (7-NI) on NTG-induced changes on blood flow was also investigated. Results: In the dura NTG caused a biphasic response represented by an initial decrease in blood flow followed by a significant increase. At variance, in the cortex NTG caused only an increase in blood flow. Pre-treatment with either L-NAME or 7-NI prevented NTG-induced increase in blood flow in both districts, while only L-NAME also prevented NTG-induced decrease in dural blood flow. Conclusion: The present findings provide additional information on the timing of effects of NTG on blood flow at both the meningeal and cortical levels. These effects seem to be related to vasoregulatory mechanisms and/or metabolic activity in response to the synthesis of endogenous NO.

Vasomotor tone does not affect perfusion heterogeneity and gas exchange in normal primate lungs during normoxia

2000 ◽  
Vol 89 (6) ◽  
pp. 2263-2267 ◽  
Author(s):  
Robb W. Glenny ◽  
H. Thomas Robertson ◽  
Michael P. Hlastala
Keyword(s):  
Blood Flow ◽  
Gas Exchange ◽  
Regional Blood Flow ◽  
Flow Distribution ◽  
Regional Perfusion ◽  
Vasomotor Tone ◽  
Heterogeneous Distribution ◽  
Mechanically Ventilated ◽  
Before And After ◽  
Spatial Coordinates

To determine whether vasoregulation is an important cause of pulmonary perfusion heterogeneity, we measured regional blood flow and gas exchange before and after giving prostacyclin (PGI2) to baboons. Four animals were anesthetized with ketamine and mechanically ventilated. Fluorescent microspheres were used to mark regional perfusion before and after PGI2 infusion. The lungs were subsequently excised, dried inflated, and diced into ∼2-cm3 pieces ( n = 1,208–1,629 per animal) with the spatial coordinates recorded for each piece. Blood flow to each piece was determined for each condition from the fluorescent signals. Blood flow heterogeneity did not change with PGI2 infusion. Two other measures of spatial blood flow distribution, the fractal dimension and the spatial correlation, did not change with PGI2 infusion. Alveolar-arterial O2 differences did not change with PGI2 infusion. We conclude that, in normal primate lungs during normoxia, vasomotor tone is not a significant cause of perfusion heterogeneity. Despite the heterogeneous distribution of blood flow, active regulation of regional perfusion is not required for efficient gas exchange.

scholarly journals Effect of Mechanical Ventilation Mode Type on Prioperative Blood Loss in Patients Undergoing Posterior Lumbar Inter body Fusion Surgery: A Randomized Controlled Trial

2021 ◽  
Author(s):  
Manoochehr Salimian ◽  
Mohammad Hajijafari ◽  
Esmaeil Fakharian ◽  
Meghdad Rahati
Keyword(s):  
Mechanical Ventilation ◽  
Controlled Trial ◽  
Fusion Surgery ◽  
Mechanically Ventilated ◽  
Volume Controlled Ventilation ◽  
Respiratory Parameters ◽  
Significant Difference ◽  
Before And After ◽  
Surgical Bleeding ◽  
The Mean

Abstract Background this study has examined modes of mechanical ventilation, pressure or volume-controlled ventilation (PCV or VCV) on intra- and post-operative surgical bleeding in posterior lumbar inter body fusion (PLIF) surgery Methods This research was a randomized, single-blinded, and parallel study, that 78 patients were selected. They mechanically ventilated using either PCV or VCV in PLIF surgery. In this regard, a permuted block randomization was used with a computer-generated list. After induction of anesthesia in supine position, the hemodynamic and respiratory parameters were measured Results The mean bleeding was 431.281 ± 361.04cc in the PCV group and 465.26 ± 338.16 cc in the VCV group (p = 0.669). Moreover, blood transfusion rates in the PCV and VCV groups were 0.40 ± 0.74 and 0.43±78 0.78 pack cell (p = 0.836), respectively. Notably, surgeon satisfaction was more observed in the PCV group (82.1% vs. 74.4%, p = 0.548). In addition, the other variables were similar in these two groups. Conclusions The mean bleeding volume was higher in the VCV group compared to the PCV group; however, no significant difference was observed between these two groups. Hemoglobin levels in the patients included before and after surgery showed that the two groups were in a similar condition.

scholarly journals Evidence of Increased Vehicle Speeding in Ohio’s Major Cities during the COVID-19 Pandemic

2020 ◽  
Author(s):  
Jinhyung Lee ◽  
Adam Porr ◽  
Harvey J. Miller
Keyword(s):  
High Resolution ◽  
Real Time ◽  
Spatial Extent ◽  
Average Level ◽  
Traffic Data ◽  
Before And After ◽  
The Mean ◽  
Mean Differences

This paper compares the speeding patterns before and after the COVID-19 pandemic in three major cities in Ohio, USA: Columbus, Cincinnati, and Cleveland. Using high-resolution and real-time INRIX traffic data, we find evidence of increased speeding in all three cities. In particular, we observe an increase in the spatial extent of speeding as well as in the average level of speeding. We also find the mean differences in speeding before and after the COVID-19 outbreak are statistically significant within the study areas.

Gravity is an important but secondary determinant of regional pulmonary blood flow in upright primates

1999 ◽  
Vol 86 (2) ◽  
pp. 623-632 ◽  
Author(s):  
Robb W. Glenny ◽  
Susan Bernard ◽  
H. Thomas Robertson ◽  
Michael P. Hlastala
Keyword(s):  
Blood Flow ◽  
Pulmonary Blood Flow ◽  
Stepwise Regression ◽  
Regional Blood Flow ◽  
Laboratory Animals ◽  
Pulmonary Perfusion ◽  
Fluorescent Microspheres ◽  
Mechanically Ventilated ◽  
Gravitational Model ◽  
Spatial Coordinates

Original studies leading to the gravitational model of pulmonary blood flow and contemporary studies showing gravity-independent perfusion differ in the recent use of laboratory animals instead of humans. We explored the distribution of pulmonary blood flow in baboons because their anatomy, serial distribution of vascular resistances, and hemodynamic responses to hypoxia are similar to those of humans. Four baboons were anesthetized with ketamine, intubated, and mechanically ventilated. Different colors of fluorescent microspheres were given intravenously while the animals were in the supine, prone, upright (repeated), and head-down (repeated) postures. The animals were killed, and their lungs were excised, dried, and diced into ∼2-cm3 pieces with the spatial coordinates recorded for each piece. Regional blood flow was determined for each posture from the fluorescent signals of each piece. Perfusion heterogeneity was greatest in the upright posture and least when prone. Using multiple-stepwise regression, we estimate that 7, 5, and 25% of perfusion heterogeneity is due to gravity in the supine, prone, and upright postures, respectively. Although important, gravity is not the predominant determinant of pulmonary perfusion heterogeneity in upright primates. Because of anatomic similarities, the same may be true for humans.

High-resolution maps of regional ventilation utilizing inhaled fluorescent microspheres

1997 ◽  
Vol 82 (3) ◽  
pp. 943-953 ◽  
Author(s):  
H. Thomas Robertson ◽  
Robb W. Glenny ◽  
Derek Stanford ◽  
Lynn M. McInnes ◽  
Daniel L. Luchtel ◽  
...  
Keyword(s):  
High Resolution ◽  
Radioactive Microspheres ◽  
Regional Ventilation ◽  
Fluorescent Microspheres ◽  
Tissue Samples ◽  
Mechanically Ventilated ◽  
Gravitational Gradient ◽  
Regional Deposition ◽  
Spatial Coordinates ◽  
The Mean

Robertson, H. Thomas, Robb W. Glenny, Derek Stanford, Lynn M. McInnes, Daniel L. Luchtel, and David Covert. High-resolution maps of regional ventilation utilizing inhaled fluorescent microspheres. J. Appl. Physiol. 82(3): 943–953, 1997.—The regional deposition of an inhaled aerosol of 1.0-μm diameter fluorescent microspheres (FMS) was used to produce high-resolution maps of regional ventilation. Five anesthetized, prone, mechanically ventilated pigs received two 10-min inhalations of pairs of different FMS labels, accompanied by intravenous injection of 15.0-μm radioactive microspheres. The lungs were air dried and cut into 1.9-cm3 pieces, with notation of the spatial coordinates for each piece. After measurement of radioactive energy peaks, the tissue samples were soaked in 2-ethoxyethyl acetate, and fluorescent emission peaks were recorded for the wavelengths specific to each fluorescence label. The correlation of fluorescence activity between simultaneously administered inhaled FMS ranged from 0.98 to 0.99. The mean coefficient of variation for ventilation for all 10 trials (47.9 ± 8.1%) was similar to that for perfusion (46.2 ± 6.3%). No physiologically significant gravitational gradient of ventilation or perfusion was present in the prone animals. The strongest predictor of the magnitude of regional ventilation among all animals was regional perfusion ( r = 0.77 ± 0.13).

scholarly journals Comparison of Corneal Power and Astigmatism between Simulated Keratometry, True Net Power, and Total Corneal Refractive Power before and after SMILE Surgery

2017 ◽  
Vol 2017 ◽  
pp. 1-8 ◽  
Author(s):  
Yishan Qian ◽  
Yan Liu ◽  
Xingtao Zhou ◽  
Rajeev Krishnan Naidu
Keyword(s):  
Accurate Method ◽  
Cross Sectional Study ◽  
Cross Sectional ◽  
Corneal Power ◽  
Refractive Power ◽  
Before And After ◽  
Lenticule Extraction ◽  
The Mean ◽  
Induced Changes ◽  
Corneal Refractive Power

Purpose. To compare the mean corneal power (Km) and total astigmatism (Ka) estimated by three methods: simulated keratometry (simK), true net power (TNP), and total corneal refractive power (TCRP) before and after femtosecond laser small incision lenticule extraction (SMILE) surgery.Methods. A retrospective, cross-sectional study. SimK, TNP, and TCRP from a Scheimpflug analyzer were obtained from 144 patients before and 6 months after SMILE surgery. Km and Ka were recorded as the mean of individual paracentral rings of 1.0 to 8.0 mm (R1 to R8). The surgically induced changes in Km (delta-simK, delta-TNP, and delta-TCRP) and Ka (delta-simKa, delta-TNPa, and delta-TCRPa) were compared to the changes in spherical equivalent of the cycloplegic refraction (delta-SE) and astigmatism (delta-RA).Results. Preoperatively, astigmatism values were greatest with simKa from R1 to R5 and greatest with TCRPa from R6 to R8. Astigmatism values were smallest with TNPa from R1 to R7. Postoperatively, astigmatism values were greatest with simKa from R1 to R5 and greatest with TCRPa from R6 to R8. Delta-TCRP3and Delta-TCRP4matched delta-SE most closely, and delta-TCRPa3matched delta-RA most closely.Conclusions. TCRP proved to be the most accurate method in estimating corneal power and astigmatism both before and after SMILE surgery.

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