Ventilatory Responses to Hypercapnic and Hypoxic Conditions in Hyperventilants

Not Applicable

Completed

• Conditions: Hyperventilation Syndrome; Hypercapnia; Hypoxia
• Interventions: Diagnostic Test: Hypercapnic hyperoxic ventilatory response; Diagnostic Test: Hypoxic eucapnic ventilatory response

• Registration Number: NCT05189158
• Lead Sponsor: Centre Hospitalier Universitaire Saint Pierre

Brief Summary

For almost a century, many hypotheses have converged on the idea of altered chemosensitivity in patients suffering from hyperventilation syndrome (HVS).

Given the evolution of current technical equipment and the ability to maximise true positives in HVS ( using the revised hyperventilation provocation test), it seems reasonable to investigate central and peripheral chemosensitivities in HVS subjects.

Detailed Description

In the inter-war period, many medical investigators who studied the hyperventilation syndrome (HVS) had already questioned the chemosensitivity to CO2 in HVS patients, without being able to explore it for all intents and purposes.

It was subsequently observed that although HVS is not systematically linked to manifest resting hypocapnia, it is nevertheless systematically correlated with significant variability and complexity of ventilation.

This is consistent with the observations of an increased plant gain in HVS, to be related to an increased loop gain (due to instability of controller gain feedback).

On the other hand, some authors already noted that, when capnia is chronically compromised in HVS, it can be greatly altered by small, transient and barely perceptible increases in VE: a 10% increase in VE could indeed halve PetCO2, while a sigh would be able to decrease PetCO2 by up to 15mmHg.

More recently, teh assumption was made that peripheral chemosensitivity may be impaired in HVS patients.

For all these considerations, it seems reasonable to investigate central and peripheral chemosensitivities in identified HVS subjects on the basis of an objective test, such as the induced hyperventilation test.

Study Timeline

• Study Start: 2021-10-15
• Primary Completion: 2021-10-15
• Study Completion: 2021-10-15
• Study First Submitted: 2021-10-18
• Status Verified: 2021-12
• Study First Submitted QC: 2021-12-22
• Last Update Submitted: 2021-12-22
• Study First Posted: 2022-01-12
• Last Update Posted: 2022-01-12

Recruitment & Eligibility

• Status: COMPLETED
• Sex: All
• Target Recruitment: 24

Inclusion Criteria

• A plethysmography within subject's predicted values
• A negative metacholine test (no documented allergy)
• A hyperventilation provocation test result that is consistent with the Nijmegen questionnaire score, confirming either group classification (HVS+ or HVS-)

Exclusion Criteria

• Each of the following known or documented conditions: chronic bronchitis (COPD), emphysema, asthma, cardiac disorder, neurological disorder, gastrointestinal disorder, thyroid disorder or psychological/psychiatric disorder
• Suspicious cardio-pulmonary exercise testing (CPET) with cardiac or respiratory limitation
• Pregnant women or women in the process of becoming pregnant
• Persons with a diving practice (amateur or professional),
• High-level athletes,
• Active smokers and
• persons using morphine, and/or barbiturates, and/or anxiolytics and/or sleeping pills

Study & Design

• Study Type: INTERVENTIONAL
• Study Design: PARALLEL

Arm && Interventions

Group	Intervention	Description
HVS-	Hypercapnic hyperoxic ventilatory response	subjects with no complaint AND a Nijmegen questionnaire score of \< 23/64 AND a negative hyperventilation provocation test (criteria revised in 2021) (HVS-)
HVS+	Hypercapnic hyperoxic ventilatory response	subjects with complaints AND a Nijmegen questionnaire score of ≥23/64 AND a negative hyperventilation provocation test (criteria revised in 2021) (HVS+)
HVS+	Hypoxic eucapnic ventilatory response	subjects with complaints AND a Nijmegen questionnaire score of ≥23/64 AND a negative hyperventilation provocation test (criteria revised in 2021) (HVS+)
HVS-	Hypoxic eucapnic ventilatory response	subjects with no complaint AND a Nijmegen questionnaire score of \< 23/64 AND a negative hyperventilation provocation test (criteria revised in 2021) (HVS-)

Primary Outcome Measures

Name	Time	Method
The slope of the ventilatory response to hypoxia (HOVR)	baseline - during the test	Ventilation increase (litres/min) per unit decrease in SpO2 (%) using Read's method
Ventilatory recruitment threshold (VRT) of the HCVR	baseline - during the test	From the average baseline ventilation and PetCO2, the VRT id the PetCO2 level at which the ventilatory response is activated
Ventilatory recruitment threshold (VRT) of the HOVR	baseline - during the test	From the average baseline ventilation and SpO2, the VRT is the level of SpO2 at which the ventilatory response is activated
The slope of the ventilatory response to hypercapnia (HCVR)	baseline - during the test	Ventilation increase (litres/min) per unit increase in PetCO2 (mmHg) using Read's method

Secondary Outcome Measures

Name	Time	Method
Extrapolated apnoeic threshold of the HCVR	baseline - during the test	PetCO2 level above which apnoea (zero ventilation) is disrupted, obtained from the extrapolation of the HCVR at the X-axis intersection (when VE=0 l/min)
Dyspnea	baseline, end of the test	Visual analogic scale (VAS) of dyspnea, from 0 (no dyspnea) to 10 (maximal dyspnea)

Trial Locations

Locations (1)

CHU St Pierre; 🇧🇪 Bruxelles, Brabant, Belgium