Assessing Variability of the Ventilatory Response to Duffin's Rebreathing Procedure

This study will combine Duffin's rebreathing procedure with additional study procedures, such as quantitative pupillometry, that are planned for subsequent clinical studies in order to confirm feasibility and gather reproducibility data using the procedure. The reproducibility of Duffin rebreathing has been assessed previously by Mahamed and Duffin (2001) performing hyperoxic and hypoxic rebreathing procedures measured once daily for 14 consecutive days and then by Jensen et al. (2010) performing 4 pairs of hyperoxic and hypoxic rebreathing procedures in 1 day followed by 1 pair on 4 additional days separated by weeks to more than a month.

The present study is an unblinded reproducibility assessment to assess variability of the ventilatory response to Duffin's rebreathing procedure. Subjects will report to the study site for screening between Days -28 to -2 and then will return to the site on Day -1 for baseline assessments and check-in. After check-in (Day -1), subjects will remain in study site for PD assessments on Day 1 and check out on Day 2.

Paired rebreathing procedures (i.e., at two different isoxic end tidal PO2 [partial pressure oxygen] levels) will be performed on Day 1 at 0, 2, 4, and 6 hours. An additional pair of rebreathing procedures will be performed on Day 2 before checkout (approximately 24 hours). Subjects will not be administered any drugs in this study.

Study Overview

• Status: Completed
• Conditions: Ventilation; Physiology; Reproducibility
• Intervention / Treatment: Other: Rebreathing procedure

• Study Type: Interventional
• Enrollment (Actual): 7
• Phase: Not Applicable

Contacts and Locations

Study Locations

• United States
  • Wisconsin
    • West Bend, Wisconsin, United States, 53095
      • Spaulding Clinical Research

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 18 years to 50 years (Adult)
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

1. Subject signs an Institutional Review Board (IRB)-approved written informed consent and privacy language as per national regulations (e.g., Health Insurance Portability and Accountability Act authorization) before any study related procedures are performed.
2. Subject is a healthy, non-smoking man or woman, 18 to 50 years of age, inclusive, who has a body mass index of 18.5 to 32 kg/m2, inclusive, at Screening.
3. Subject has normal medical history findings, clinical laboratory results, vital sign measurements, 12 lead ECG results, and physical examination findings at screening or, if abnormal, the abnormality is not considered clinically significant (as determined and documented by the investigator or designee).
4. Subject must have a negative test result for alcohol and drugs of abuse at screening and Check-in (Day -1).
5. Subject must test negative for severe acute respiratory syndrome coronavirus (SARS-CoV-2) by a molecular diagnostic test at check-in (Day -1). If a subject's test comes back inconclusive, it can be repeated at Check-in.
6. Female subjects must be of non-childbearing potential or, if they are of childbearing potential, they must: 1) have been strictly abstinent for 1 month before Check in (Day -1) and agree to remain strictly abstinent for the duration of the study and for at least 1-month after the last rebreathing procedure; OR 2) be practicing 2 highly effective methods of birth control (as determined by the investigator or designee; one of the methods must be a barrier technique) from at least 1 month before Check in (Day -1) until at least 1 month after the end of the study.
7. Male subjects must agree to practice 2 highly effective methods of birth control (as determined by the investigator or designee) from at least 1 month before Check In (Day -1) until at least 1 month after the last rebreathing procedure.
8. Subject is highly likely (as determined by the investigator) to comply with the protocol defined procedures and to complete the study.

Exclusion Criteria:

1. Subject has non-reactive or misshapen pupil(s) or damaged orbit structure or surrounding soft tissue is edematous or has an open lesion.
2. Subject Duffin rebreathing data is of poor quality or subject does not agree to remain clean-shaven for all days when the Duffin rebreathing procedure is being performed.
3. Subject has used any prescription or nonprescription drugs (including aspirin or NSAIDs and excluding oral contraceptives and acetaminophen) within 14 days or 5 half-lives (whichever is longer) or complementary and alternative medicines within 28 days before check-in.
4. Subject has used nicotine-containing products (e.g., cigarettes, cigars, chewing tobacco, snuff) within 6 weeks of Screening
5. Subject has a history or evidence of a clinically significant disorder, condition, or disease (e.g., cancer, human immunodeficiency virus [HIV], hepatic or renal impairment) that, in the opinion of the investigator would pose a risk to subject safety or interfere with the study evaluation, procedures, or completion. This includes subjects with any underlying medical conditions that the Investigator believes would put subjects at increased risk of severe illness from COVID-19 based on the Centers for Disease Control and Prevention (CDC) guidelines.
6. Subject has any signs or symptoms that are consistent with COVID-19. These include subjects with fever or chills, cough, shortness of breath or difficulty breathing, fatigue, muscle or body aches, headache, new loss of taste or smell, sore throat, congestion or runny nose, nausea or vomiting, or diarrhea may have COVID-19. In addition, the subject has any other findings suggestive of COVID-19 risk in the opinion of the investigator.
7. Subject tests positive for SARS-CoV-2 by a molecular diagnostic test performed prior to admission.
8. Subject has clinical laboratory test results (hematology, serum chemistry and urinalysis) at Screening or Check-In that are outside the reference ranges provided by the clinical laboratory and considered clinically significant by the investigator.
9. Subject has a positive test result at Screening for HIV 1 or 2 antibody, hepatitis C virus antibodies, or hepatitis B surface antigen.
10. Female subject is pregnant or lactating before enrollment in the study.
11. Subject has a history of or currently has hypoventilation syndrome, sleep apnea, or chronic obstructive pulmonary disease (COPD) and is on non-invasive ventilation.
12. Subject has a history of asthma that has required medication within the last five years.
13. Subject has a history of sleep disorders, Panic Disorder, Panic Attacks, Generalized Anxiety Disorder, or any associated DSM diagnosis or condition.

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Other
• Allocation: N/A
• Interventional Model: Single Group Assignment
• Masking: None (Open Label)

Number of Arms

1

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Lead-In; Multiple rebreathing procedures using methodology developed by Duffin (referred to as Duffin's rebreathing procedure) will be conducted under hyperoxic and hypoxic conditions over the course of a day to confirm feasibility and gather reproducibility data using the procedure.	Other: Rebreathing procedure; Paired Duffin's rebreathing procedures performed two different isoxic end tidal PO2 levels (i.e., hyperoxic and hypoxic conditions) will be performed on Day 1 at 0, 2, 4, 6, and 24 hours.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Baseline Minute Ventilation	Minute ventilation during the rebreathing assessment when end tidal PCO2 (partial pressure carbon dioxide) is less than the ventilatory recruitment threshold (represents non-chemoreflex drives to breathe; 'flat' portion of minute ventilation versus end tidal PCO2 relationship). Data was analyzed using linear-mixed effects regression of baseline minute ventilation with random effects for between subject, between day, and between occasion variability. Reported value is the mean for the treatment group across all individuals, days, and times.	0, 2, 4, 6 and 24 hours
Ventilatory Recruitment Threshold	The end tidal PCO2 point above which minute ventilation starts to increase linearly with further increases in end tidal PCO2. Data was analyzed using linear-mixed effects regression of ventilatory recruitment threshold with random effects for between subject, between day, and between occasion variability. Reported value is the mean for the treatment group across all individuals, days, and times.	0, 2, 4, 6 and 24 hours
Slope of the PCO2-ventilatory Response Curve	Slope of the minute ventilation versus end tidal PCO2 curve that reflects the increase in minute ventilation relative to the increase in end tidal PCO2. Data was analyzed using linear-mixed effects regression of Slope of the PCO2-ventilatory response curve with random effects for between subject, between day, and between occasion variability. Reported value is the mean for the treatment group across all individuals, days, and times.	0, 2, 4, 6 and 24 hours
Extrapolated Ventilatory Recruitment Threshold	Intersection of the slope of the PCO2-ventilation response curve with the X axis. Data was analyzed using linear-mixed effects regression of extrapolated ventilatory recruitment threshold with random effects for between subject, between day, and between occasion variability. Reported value is the mean for the treatment group across all individuals, days, and times.	0, 2, 4, 6 and 24 hours

Collaborators and Investigators

• Sponsor: Food and Drug Administration (FDA)
• Collaborators: Spaulding Clinical Research LLC
• Investigators: Principal Investigator: Jan Matousek, D.O., Spaulding Clinical Research LLC

Publications and helpful links

General Publications

• Duffin J. Measuring the respiratory chemoreflexes in humans. Respir Physiol Neurobiol. 2011 Jul 31;177(2):71-9. doi: 10.1016/j.resp.2011.04.009. Epub 2011 Apr 14.
• Mahamed S, Duffin J. Repeated hypoxic exposures change respiratory chemoreflex control in humans. J Physiol. 2001 Jul 15;534(Pt. 2):595-603. doi: 10.1111/j.1469-7793.2001.00595.x.
• Jensen D, Mask G, Tschakovsky ME. Variability of the ventilatory response to Duffin's modified hyperoxic and hypoxic rebreathing procedure in healthy awake humans. Respir Physiol Neurobiol. 2010 Feb 28;170(2):185-97. doi: 10.1016/j.resp.2009.12.007. Epub 2009 Dec 24.

Study record dates

Study Major Dates

• Study Start (Actual): December 27, 2021
• Primary Completion (Actual): February 18, 2022
• Study Completion (Actual): February 18, 2022

Study Registration Dates

• First Submitted: December 13, 2021
• First Submitted That Met QC Criteria: December 13, 2021
• First Posted (Actual): December 23, 2021

Study Record Updates

• Last Update Posted (Actual): July 15, 2024
• Last Update Submitted That Met QC Criteria: April 10, 2024
• Last Verified: December 1, 2021

More Information

Terms related to this study

• Keywords: Ventilation; Physiology; Pupillometry; Duffin's rebreathing procedure
• Other Study ID Numbers: SCR-013

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No