Dead Space Evaluation in Pulmonary Hypertension

Study Overview
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Brief Summary
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Aim of the study is to evaluate the role of chemoreceptor activity and ventilation perfusion mismatch on the genesis of exercise induced hyperventilation in Pulmonary hypertension patients. So the investigators tested the chemoreceptor response at rest, both with hypoxic and hypercapnic stimuli, and the ventilatory response during exercise analyzing its two components, alveolar and dead space ventilation.

Official Title
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Dead Space Evaluation During Exercise in Patients With Pulmonary Hypertension

Conditions
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Pulmonary Hypertension

Intervention / Treatment
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* Other: cardiopulmonary exercise test,hypoxia and hypercapnia test


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: age ≥18 and ≤ 80 years ability to understand the research protocol and willing to sign the study informed consent diagnosis of pulmonary arterial hypertension belonging to Class I and IV stable haemodynamic status and optimized medical treatment since at least 2 months ability to perform maximal cardiopulmonary exercise test and pulmonary diffusing capacity for carbon monoxide evaluation Exclusion Criteria: relevant comorbidities usual contraindications for cardiopulmonary exercise test pulmonary hypertension associated to left heart and pulmonary disease, congenital heart diseases with evident cardiac shunts.

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 80 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Diagnostic
Intervention Model: Single Group Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Other: Pulmonary hypertension patients<br>All Pulmonary hypertension patients enrolled in the study underwent a cardiopulmonary exercise test and hypoxia and hypercapnia tests | Other: cardiopulmonary exercise test,hypoxia and hypercapnia test<br>* class I and IV Pulmonary hypertension patients in stable haemodynamic status and optimized medical therapy underwent cardiopulmonary test and hypoxia and hypercapnia tests to evaluate the chemoreceptor sensitivity<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| dead space ventilation (measured in L/min) | Dead space ventilation is calculated through the equation: VT* [1- (863*VCO2)/(VE*PaCO2)], where VT = tidal volume, VCO2= CO2 output, VE= pulmonary ventilation,PaCO2 is the arterial partial pressure of CO2 and 863 is a constant. | 1 week | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| peripheral response to hypoxia (measured in L/min/O2) | the hypoxic test is based on the transient hypoxia (the patient inhales a mixture of nitrogen for 2-8 breaths, for 10-15 times); pulmonary ventilation (VE) and arterial oxygen saturation (O2 Saturation) by peripheral pulse oximetry is measured. The chemoreceptor sensitivity value is calculated as the slope of the trend line built on the two maximum consecutive VE and minimum O2 Saturation of each test. | 1 week | 
| peripheral response to hypercapnia (measured in L/min/mmHg) | the peripheral response to hypercapnia is evaluated through the single-breath technique (the patient inhales a mixture of 13% CO2 in air for a single breath); pulmonary ventilation (VE) and end-expiratory CO2 fraction (FetCO2) are measured and then they will be used to calculate the peripheral chemoreceptor sensitivity.In fact, the sensitivity of the chemoreceptor is calculated using the following formula VEs-VEc / (FetCO2s-FetCO2c) * (PB-47), where s and c indicate the data collected after hypercapnic stimulus and those collected during control air breathing ,respectively; PB is the atmospheric pressure in mmHg | 1 week | 
| central hypercapnic chemosensitivity (measured in L/min/mmHg) | the evaluation of the central response to hypercapnia is made through the re-breathing technique (the patient breathes through a reservoir containing 7% CO2 and 93% O2 for 4 minutes); pulmonary ventilation (VE) and partial pressure of end-tidal carbon dioxide (PetCO2) are evaluated. The slope of the curve describing the relationship between VE and PetCO2 identifies the central chemoreceptor sensitivity | 1 week |