Development of a method to measure regional perfusion of the lung in anesthetized ponies using computed tomography angiography and the maximum slope model

Abstract OBJECTIVE To develop a method based on CT angiography and the maximum slope model (MSM) to measure regional lung perfusion in anesthetized ponies. ANIMALS 6 ponies. PROCEDURES Anesthetized ponies were positioned in dorsal recumbency in the CT gantry. Contrast was injected, and the lungs were imaged while ponies were breathing spontaneously and while they were mechanically ventilated. Two observers delineated regions of interest in aerated and atelectatic lung, and perfusion in those regions was calculated with the MSM. Measurements obtained with a computerized method were compared with manual measurements, and computerized measurements were compared with previously reported measurements obtained with microspheres. RESULTS Perfusion measurements obtained with the MSM were similar to previously reported values obtained with the microsphere method. While ponies were spontaneously breathing, mean ± SD perfusion for aerated and atelectatic lung regions were 4.0 ± 1.9 and 5.0 ± 1.2 mL/min/g of lung tissue, respectively. During mechanical ventilation, values were 4.6 ± 1.2 and 2.7 ± 0.7 mL/min/g of lung tissue at end expiration and 4.1 ± 0.5 and 2.7 ± 0.6 mL/min/g of lung tissue at peak inspiration. Intraobserver agreement was acceptable, but interobserver agreement was lower. Computerized measurements compared well with manual measurements. CLINICAL RELEVANCE Findings showed that CT angiography and the MSM could be used to measure regional lung perfusion in dorsally recumbent anesthetized ponies. Measurements are repeatable, suggesting that the method could be used to determine efficacy of therapeutic interventions to improve ventilation-perfusion matching and for other studies for which measurement of regional lung perfusion is necessary.

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Blood flow distribution in the duck lung and its control by respiratory gases

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.1978.234.3.r146 ◽

1978 ◽

Vol 234 (3) ◽

pp. R146-R154

Author(s):

J. P. Holle ◽

N. Heisler ◽

P. Scheid

Keyword(s):

Blood Flow ◽

Gas Flow ◽

Flow Distribution ◽

Lung Perfusion ◽

Blood Flow Distribution ◽

Local Blood Flow ◽

Regional Lung ◽

Unanesthetized Animals ◽

Respiratory Gases ◽

Spontaneously Breathing

Blood flow to subunits of the lung was studied in the duck by use of radioactive microspheres. In spontaneously breathing, unanesthetized animals (series I) neopulmo was slightly better perfused than the average lung and along the paleopulmonic parabronchi, blood flow was found to decrease in the direction of ventilatory gas flow and thus of decreasing PO2 and increasing PCO2 in lung gas. The effects of respiratory gases on regional lung perfusion were investigated in unidirectionally ventilated animals (series II) in which gas mixtures offered to both lungs could be controlled independently. Local hypoxia resulted in reduction of local blood flow, whereas effects from hyperoxia or CO2 could not be substantiated. Reversal of the direction of unidirectional ventilatory flow (series III), and thus reversal of the profiles of respired gas concentrations along the parabronchi, suggest that the inhomogeneity in blood flow observed in spontaneously breathing animals of series I can only in part be explained as an acute adjustment to the local hypoxia. Calculations show that this inhomogeneity of blood flow constitutes an only minor impairment of the overall gas exchange efficacy of the parabronchial lung.

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EXPRESS: Rapid dynamic bedside assessment of pulmonary perfusion defect by electrical impedance tomography in a patient with acute massive pulmonary embolism

Pulmonary Circulation ◽

10.1177/2045894020984043 ◽

2020 ◽

pp. 204589402098404

Author(s):

Siyi Yuan ◽

Huaiwu He ◽

Yun Long ◽

Yi Chi ◽

InÃ©z Frerichs ◽

...

Keyword(s):

Pulmonary Embolism ◽

Electrical Impedance Tomography ◽

Perfusion Defect ◽

Electrical Impedance ◽

Massive Pulmonary Embolism ◽

Lung Perfusion ◽

Regional Perfusion ◽

Pulmonary Perfusion ◽

Impedance Tomography ◽

Regional Lung

Background: Several animal studies have shown that regional lung perfusion could be effectively estimated by the hypertonic saline contrast electrical impedance tomography (EIT) method. Here, we reported an application of this method to dynamically assess regional pulmonary perfusion defect in a patient with acute massive pulmonary embolism. Case presentation: A 68-year-old man experienced sudden dyspnea and cardiac arrest during out-of-bed physical activity on the first day after partial mediastinal tumor resection. Acute pulmonary embolism (PE) was suspected due to acute enlargement of right heart and fixed inferior venous cava measured with bedside ultrasound. The computed tomography pulmonary angiography further confirmed large embolism in both left and right main pulmonary arteries and branches. The regional time impedance curves, which were obtained by a bolus of 10ml 10% NaCl through the central venous catheter, were then analyzed to quantitatively assess regional perfusion. Normal ventilation distribution with massive defects in regional perfusion in both lungs was observed, leading to a ventilation-perfusion mismatch and low oxygenation index (PaO2/FiO2=86 mmHg) at the first day of PE. The anticoagulation was performed with heparin, and the patientâs condition (such as shock, dyspnea, hypoxemia etc.), regional lung perfusion defect and ventilation-perfusion mismatch continuously improved in the following days. Conclusions: This case implies that EIT might have the potential to assess and monitor regional perfusion for rapid diagnosis of fatal PE in clinical practice.

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Respiratory variation of inferior vena cava diameter and central venous pressure in ventilated and non-ventilated children in fluid refractory septic shock: an observational study

International Journal of Contemporary Pediatrics ◽

10.18203/2349-3291.ijcp20193691 ◽

2019 ◽

Vol 6 (5) ◽

pp. 1947

Author(s):

Mohd Kashif Ali ◽

Eeman Naim

Keyword(s):

Septic Shock ◽

Inferior Vena Cava ◽

Central Venous Pressure ◽

Inferior Vena ◽

Venous Pressure ◽

Vena Cava ◽

Central Venous ◽

Mechanically Ventilated ◽

Spontaneously Breathing ◽

Ventilated Patients

Background: Ultrasound guided fluid assessment in management of septic shock has come up as an adjunct to the current gold standard Central Venous Pressure monitoring. This study was designed to observe the respiro-phasic variation of IVC diameter (RV-IVCD) in invasively mechanically ventilated and spontaneously breathing paediatric patients of fluid refractory septic shock.Methods: This was a prospective observational study done at Paediatric intensive Care Unit (PICU) in Paediatric ward of Jawaharlal Nehru Medical College and Hospital (JNMCH) from February 2016 to June 2017. 107 consecutive patients between 1 year to 16 years age who were in shock despite 40ml/kg of fluid administration were included. Inferior Vena Cava (IVC) diameters were measured at end-expiration and end inspiration and the IVC collapsibility index was calculated. Simultaneously Central Venous Pressure (CVP) was recorded. Both values were obtained in ventilated and non-ventilated patients. Data was analysed to determine to look for the profile of RV-IVCD and CVP in ventilated and non-ventilated cases.Results: Out of 107 patients, 91 were on invasive mechanical ventilation and 16 patients were spontaneously breathing. There was a strong negative correlation between central venous pressure (CVP) and inferior vena cava collapsibility (RV-IVCD) in both spontaneously breathing (-0.810) and mechanically ventilated patients (-0.700). Negative correlation was significant in both study groups in CVP <8 mmHg and only in spontaneously breathing patients in CVP 8-12 mmHg range. IVC collapsibility showed a decreasing trend with rising CVP in both spontaneously breathing and mechanically ventilated patients.Conclusion: Ultrasonography guided IVCCI appears to be a valuable index in assessing fluid status in both spontaneously breathing and mechanically ventilated septic shock patients. However, more data is required from the paediatric population so as to define it as standard of practice.

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Electrical Impedance Tomography for Assessment of Pendelluft and Work of Breathing in Spontaneously Breathing Mechanically Ventilated Patients

10.1164/ajrccm-conference.2021.203.1_meetingabstracts.a2803 ◽

2021 ◽

Author(s):

E. Kistler ◽

M.S. Schaefer ◽

E. Baedorf Kassis

Keyword(s):

Electrical Impedance Tomography ◽

Electrical Impedance ◽

Work Of Breathing ◽

Impedance Tomography ◽

Mechanically Ventilated ◽

Mechanically Ventilated Patients ◽

Spontaneously Breathing ◽

Ventilated Patients

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Comparison of regional lung perfusion response on longitudinal MAA SPECT/CT in lung cancer patients treated with and without functional tissue-avoidance radiation therapy

British Journal of Radiology ◽

10.1259/bjr.20190174 ◽

2019 ◽

Vol 92 (1103) ◽

pp. 20190174 ◽

Cited By ~ 1

Author(s):

Hannah Mary T Thomas ◽

Jing Zeng ◽

Howard J Lee, Jr ◽

Balu Krishna Sasidharan ◽

Paul E Kinahan ◽

...

Keyword(s):

Lung Cancer ◽

Radiation Therapy ◽

Cancer Patients ◽

Dose Response ◽

Lung Perfusion ◽

Ct Scans ◽

Lung Dose ◽

Lung Cancer Patients ◽

Response Slope ◽

Regional Lung

Objective: The effect of functional lung avoidance planning on radiation dose-dependent changes in regional lung perfusion is unknown. We characterized dose-perfusion response on longitudinal perfusion single photon emission computed tomography (SPECT)/CT in two cohorts of lung cancer patients treated with and without functional lung avoidance techniques. Methods: The study included 28 primary lung cancer patients: 20 from interventional (NCT02773238) (FLARE-RT) and eight from observational (NCT01982123) (LUNG-RT) clinical trials. FLARE-RT treatment plans included perfused lung dose constraints while LUNG-RT plans adhered to clinical standards. Pre- and 3 month post-treatment macro-aggregated albumin (MAA) SPECT/CT scans were rigidly co-registered to planning four-dimensional CT scans. Tumour-subtracted lung dose was converted to EQD2 and sorted into 5 Gy bins. Mean dose and percent change between pre/post-RT MAA-SPECT uptake (%ΔPERF), normalized to total tumour-subtracted lung uptake, were calculated in each binned dose region. Perfusion frequency histograms of pre/post-RT MAA-SPECT were analyzed. Dose–response data were parameterized by sigmoid logistic functions to estimate maximum perfusion increase (%ΔPERFmaxincrease), maximum perfusion decrease (%ΔPERFmaxdecrease), dose midpoint (Dmid), and dose-response slope (k). Results: Differences in MAA perfusion frequency distribution shape between time points were observed in 11/20 (55%) FLARE-RT and 2/8 (25%) LUNG-RT patients (p < 0.05). FLARE-RT dose response was characterized by >10% perfusion increase in the 0–5 Gy dose bin for 8/20 patients (%ΔPERFmaxincrease = 10–40%), which was not observed in any LUNG-RT patients (p = 0.03). The dose midpoint Dmid at which relative perfusion declined by 50% trended higher in FLARE-RT compared to LUNG-RT cohorts (35 GyEQD2 vs 21 GyEQD2, p = 0.09), while the dose-response slope k was similar between FLARE-RT and LUNG-RT cohorts (3.1–3.2, p = 0.86). Conclusion: Functional lung avoidance planning may promote increased post-treatment perfusion in low dose regions for select patients, though inter-patient variability remains high in unbalanced cohorts. These preliminary findings form testable hypotheses that warrant subsequent validation in larger cohorts within randomized or case-matched control investigations. Advances in knowledge: This novel preliminary study reports differences in dose-response relationships between patients receiving functional lung avoidance radiation therapy (FLARE-RT) and those receiving conventionally planned radiation therapy (LUNG-RT). Following further validation and testing of these effects in larger patient populations, individualized estimation of regional lung perfusion dose-response may help refine future risk-adaptive strategies to minimize lung function deficits and toxicity incidence.

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Vibrating Mesh Nebulisation of Pro-Antimicrobial Peptides for Use in Cystic Fibrosis

Pharmaceutics ◽

10.3390/pharmaceutics11050239 ◽

2019 ◽

Vol 11 (5) ◽

pp. 239 ◽

Cited By ~ 3

Author(s):

Éanna Forde ◽

Graeme Kelly ◽

Louise Sweeney ◽

Deirdre Fitzgerald-Hughes ◽

Ronan MacLoughlin ◽

...

Keyword(s):

Cystic Fibrosis ◽

Antimicrobial Peptides ◽

Droplet Size ◽

Droplet Size Distribution ◽

Antimicrobial Activities ◽

Physical Characteristics ◽

Mechanically Ventilated ◽

Delivery Times ◽

Before And After ◽

Spontaneously Breathing

Background: There has been considerable interest in the use of antimicrobial peptides (AMPs) as antimicrobial therapeutics in many conditions including cystic fibrosis (CF). The aim of this study is to determine if the prodrugs of AMPs (pro-AMPs) can be delivered to the lung by a vibrating mesh nebuliser (VMN) and whether the pro-AMP modification has any effect on delivery. Methods: Physical characteristics of the peptides (AMP and pro-AMP) and antimicrobial activity were compared before and after nebulisation. Droplet size distribution was determined by laser diffraction and cascade impaction. Delivery to a model lung was determined in models of spontaneously-breathing and mechanically-ventilated patients. Results: The physical characteristics and antimicrobial activities were unchanged after nebulisation. Mean droplet size diameters were below 5 μm in both determinations, with the fine particle fraction approximately 67% for both peptides. Approximately 25% of the nominal dose was delivered in the spontaneously-breathing model for both peptides, with higher deliveries observed in the mechanically-ventilated model. Delivery times were approximately 170 s per mL for both peptides and the residual volume in the nebuliser was below 10% in nearly all cases. Conclusions: These results demonstrate that the delivery of (pro-)AMPs to the lung using a VMN is feasible and that the prodrug modification is not detrimental. They support the further development of pro-AMPs as therapeutics in CF.

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A reproducible model of chronic hypoxemia

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.1983.244.5.h730 ◽

1983 ◽

Vol 244 (5) ◽

pp. H730-H733

Author(s):

H. G. Erath ◽

T. P. Graham ◽

J. W. Hammon ◽

H. W. Bender

Keyword(s):

Pulmonary Veins ◽

Vena Cava ◽

Prosthetic Graft ◽

Pulmonary Tissue ◽

Mechanically Ventilated ◽

Persistent Depression ◽

The Right ◽

Chronic Hypoxemia ◽

Breathing Room ◽

Spontaneously Breathing

This report presents our experience with producing a stable chronic hypoxemia preparation in the dog without the disadvantages of prosthetic graft insertion or sacrifice of pulmonary tissue. In 28 adult dogs, the intrapericardial inferior vena cava and the area of junction of the right and left inferior pulmonary veins were exposed through a right thoracotomy. The cava was clamped at the diaphragm and at the right atrium, divided at the atrial clamp, and quickly anastomosed to the inferior pulmonary veins. The mean arterial O2 tension (PaO2) decreased from 83.2 +/- 1.6 mmHg preoperatively in mechanically ventilated (room air) animals to 35.3 +/- 1.5 mmHg postoperatively in awake animals spontaneously breathing room air (P less than 0.001). There was persistent depression of the PaO2 (49.1 +/- 1.8 mmHg) and elevation of the hematocrit (64.8 +/- 2.0%) in six animals tested at 18.5 mo postoperatively. Shunt patency without significant stenosis was confirmed in each animal at autopsy. This method attains predictable and persistent hypoxemia and polycythemia and is simple to perform. It may be useful in studying various aspects of ventricular function and ventricular histological and biochemical changes with chronic cyanosis.

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Rat Model to Investigate the Treatment of Acute Nitrogen Dioxide Intoxication

Human & Experimental Toxicology ◽

10.1177/096032719201100306 ◽

1992 ◽

Vol 11 (3) ◽

pp. 179-187 ◽

Cited By ~ 6

Author(s):

J. Meulenbelt ◽

J.A.M.A. Dormans ◽

M. Marra ◽

P.J.A. Rombout ◽

B. Sangster

Keyword(s):

Lung Injury ◽

Nitrogen Dioxide ◽

Lung Tissue ◽

Rat Model ◽

Therapeutic Interventions ◽

Nitrite Concentration ◽

Therapeutic Measures ◽

Severe Lung

1 The pulmonary toxic events induced by acute nitrogen dioxide (NO)2 exposure were studied in the rat to develop an inhalation model to investigate therapeutic measures. 2 A good correlation was observed between the lung weights and severity of the atypical pneumonitis. The pulmonary effects observed, became more pronounced with increasing NO 2 concentrations (0, 25, 75, 125, 175 or 200 ppm, 1 ppm NO2=1.88 mg m-3 NO2) and exposure times (5, 10, 20 or 30 min). 3 An adequate NO 2 concentration is 175 ppm, because it can induce a severe lung injury without mortality. This makes it possible to investigate suitable therapeutic interventions for several days. 4 Following acute inhalatory NO2 intoxication, transformation of NO2 to nitrate is presumably more notable than transformation to nitrite. 5 The transformation of NO2 to nitrate in lung tissue causes a slight increase in the serum nitrite concentration, which does not induce measurable formation of methaemoglobin. 6 Presumably, methaemoglobin does not contribute to the toxicity of NO2 intoxication.

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