Evaluation of Microcirculation With Photoplethysmography (Pulse Oximetry) in Healthy Volunteers and Ventilated Patients

Study Overview
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Brief Summary
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The objective of this observational study is to explore microcirculation in healthy volunteers and in ventilated patients in the operating room and in critical care. The general objective of this study is to evaluate microcirculation with photoplethysmography (PPG) in different pathophysiological situations and to compare PPG with available standard methods. Specifically, evaluate the correlation between the determinations of AC-DC waves obtained by Photoplethysmography (PPG) and those obtained in different dynamic tests in healthy volunteers. To compare microcirculation assessments [capillary refill time (CRT), perfusion index (PI), perfusion index variability (PIV)] with measurements obtained by PPG in the context of critically ill patients. To compare microcirculation assessments (CRT, PI PVI) with measurements obtained by PPG in the context of patients on invasive mechanical ventilation (IMV) in the operating room and in critical care.

Detailed Description
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An attempt is made to explore different physiological aspects that affect microcirculation such as vascular tone and blood volume. Photoplethysmography usually examines the AC wave equivalent to the pulsatile wave, however the DC component has been less explored and can account for the microcirculation and volemia status of the subjects. Since there is no gold standard, it will be compared against different validated methods.

Official Title
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Evaluation of Microcirculation With Photoplethysmography (Pulse Oximetry) in Healthy Volunteers and Ventilated Patients

Conditions
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Microcirculation, Photoplethysmography

Intervention / Treatment
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* Other: photoplethysmography


Participation Criteria
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Eligibility Criteria
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Healthy Volunteers: Inclusion Criteria: Written informed consent. Age > 18 years. Exclusion Criteria: Pregnancy. Smokers. Respiratory and/or cardiovascular pathologies. Peripheral vascular disease. Operation room or Critical care Unit patients Inclusion criteria: Written informed consent. Age > 18 years. Critical patients ventilated in the ICU of any origin. Exclusion criteria: Known peripheral vascular disease. Burns on both upper limbs. Trauma to both upper limbs.

Ages Eligible for Study
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Minimum Age: 18 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Healthy volunteers<br>>18 years old healthy | Other: photoplethysmography<br>* Photoplethysmography (BluePoint, Frankfurt, Germany) is the pulse wave measured by a pulse oximeter. It is obtained based on the absorbance of red/infrared light in a given tissue. The signal is made up of two components: 1) the alternating component (AC), which is the pulse wave itself, which is determined by the absorbance of pulsatile arterial blood. 2) The continuous component (DC), which represents the absorbance of venous blood and the rest of the tissues. Within these tests the investigators find vascular occlusion, elevation of the legs, raising or lowering the tested hand above/below the phlebostatic level, cold/heat test, etc. Each of them evaluates different aspects of circulation such as endothelial function, myogenic response to blood flow, perfusion pressure, autonomic reflexes, preload-dependence, or venous flow among other aspects of microcirculation.<br>|
| Patients in critical care unit<br>patient in ICU with requirement for hemodynamic monitoring | Other: photoplethysmography<br>* Photoplethysmography (BluePoint, Frankfurt, Germany) is the pulse wave measured by a pulse oximeter. It is obtained based on the absorbance of red/infrared light in a given tissue. The signal is made up of two components: 1) the alternating component (AC), which is the pulse wave itself, which is determined by the absorbance of pulsatile arterial blood. 2) The continuous component (DC), which represents the absorbance of venous blood and the rest of the tissues. Within these tests the investigators find vascular occlusion, elevation of the legs, raising or lowering the tested hand above/below the phlebostatic level, cold/heat test, etc. Each of them evaluates different aspects of circulation such as endothelial function, myogenic response to blood flow, perfusion pressure, autonomic reflexes, preload-dependence, or venous flow among other aspects of microcirculation.<br>|
| Patients with ventilatory support in the operating room or critical care unit<br>patient in the ICU or operating room with a requirement for hemodynamic monitoring and ventilatory support | Other: photoplethysmography<br>* Photoplethysmography (BluePoint, Frankfurt, Germany) is the pulse wave measured by a pulse oximeter. It is obtained based on the absorbance of red/infrared light in a given tissue. The signal is made up of two components: 1) the alternating component (AC), which is the pulse wave itself, which is determined by the absorbance of pulsatile arterial blood. 2) The continuous component (DC), which represents the absorbance of venous blood and the rest of the tissues. Within these tests the investigators find vascular occlusion, elevation of the legs, raising or lowering the tested hand above/below the phlebostatic level, cold/heat test, etc. Each of them evaluates different aspects of circulation such as endothelial function, myogenic response to blood flow, perfusion pressure, autonomic reflexes, preload-dependence, or venous flow among other aspects of microcirculation.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| variations in AC signal of photoplethysmography | Changes in the AC wave of photoplethysmography (it does not currently have standardized measurement units) will be evaluated in each functional test (CRT, LPR, venous occlusion test, progressive arterial occlusion test). It will be treated as a continuous numerical variable. | Through study completion, an average of 1 year | 
| variations in DC signal of photoplethysmography | Changes in the DC wave of photoplethysmography (it does not currently have standardized measurement units) will be evaluated in each functional test (CRT, LPR, venous occlusion test, progressive arterial occlusion test). It will be treated as a continuous numerical variable. | Through study completion, an average of 1 year |