Distribution of Ventilation, Respiratory Drive and Gas Exchange: Measurements and Monitoring

Respiratory physiology involves a complex interplay of elements including control of breathing, respiratory drive, pulmonary mechanics, distribution of ventilation and gas exchange. Body position may also play an important role in respiratory mechanics. While effective methods exist for measuring these variables, they are typically measured in isolation rather than in combination. In pulmonary disease, decreasing mechanical stress and strain and optimizing transpulmonary pressure or the distending pressure across the lung, minimizing overdistention and collapse are central to clinical management. Obesity has a significant impact on pulmonary mechanics and is a risk factor for obstructive sleep apnea (OSA). However, our understanding of these elements is limited even in the general population. The investigators plan to use various validated methods to assess control of breathing, respiratory drive, distribution of ventilation and gas exchange to obtain a better understanding of underlying physiologic signatures in patients with and without obesity and the role of posture/position, with a secondary analysis comparing participants with and without obstructive sleep apnea.

Study Overview

• Status: Enrolling by invitation
• Conditions: Respiratory Failure; Pulmonary Disease; OSA; Respiratory System Abnormalities
• Intervention / Treatment: Other: Position change

• Study Type: Observational
• Enrollment (Estimated): 40

Contacts and Locations

Study Locations

• United States
  • California
    • La Jolla, California, United States, 92037
      • University of California San Diego Health

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 18 years and older (Adult, Older Adult)
• Accepts Healthy Volunteers: Yes

• Sampling Method: Non-Probability Sample

Study Population

Investigators will enroll 20 subjects with BMI 18.5-24.9 and 20 subjects with BMI 25 or more. The detailed inclusion criteria for subjects are listed below.

Description

Inclusion Criteria:

• 18 years or older
• Non-smokers

Exclusion Criteria:

• <18 years old
• Significant history of pulmonary disease
• Chest wall, anatomical, physical abnormalities, skin integrity issues precluding placement of electrode belt in direct contact with skin
• Skin integrity issues precluding placement of nose clips, or transcutaneous carbon dioxide monitoring
• Inability to form a seal around a mouthpiece
• Known esophageal strictures, webs, or varices (if esophageal manometry to be included)
• Known platelet count < 100,000 (if esophageal manometry to be included)
• On therapeutic anticoagulation (if esophageal manometry to be included)
• Known multidrug resistant (MDR) pulmonary infection
• Non-English language speakers
• Chronic hypoxemic respiratory failure
• Confirmed or suspected intracranial bleed, stroke, edema
• Active implants (i.e. implantable electronic devices such as pacemakers, cardioverter defibrillators or neurostimulators) or if device compatibility is in doubt
• Pregnant or lactating patients as safety and efficacy for use of EIT in such cases has not been verified

Study Plan

How is the study designed?

Number of groups / cohorts

2

Cohorts and Interventions

Group / Cohort	Intervention / Treatment
BMI>24.9 kg/m2	Other: Position change; Distribution of ventilation, respiratory drive, pulmonary mechanics and gas exchange will be measured in 3 unique positions: prone, head of bed (HOB) flat (i.e. 0 degrees) and HOB elevated (i.e. 30 degrees).
BMI 18-24.9 kg/m2	Other: Position change; Distribution of ventilation, respiratory drive, pulmonary mechanics and gas exchange will be measured in 3 unique positions: prone, head of bed (HOB) flat (i.e. 0 degrees) and HOB elevated (i.e. 30 degrees).

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Distribution of ventilation	Change in regional ventilation distribution (ventral/dorsal) measured through electrical impedance tomography (EIT)	3 hours
Respiratory drive	Respiratory drive differences will be measured by mean desaturation (change from baseline percent oxygen saturation) following breath-hold maneuvers	3 hours
Respiratory drive	Respiratory drive differences will be assessed by the duration of maximal breath-hold (seconds)	3 hours
Respiratory drive	Respiratory drive will also be assessed by measurement of occlusion pressure (cm H2O) at 100 ms (P0.1) after the initiation of an inspiratory effort against a closed circuit.	3 hours

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Pulmonary mechanics	Pulmonary mechanics will be measured by transpulmonary pressure (cmH2O)obtained from esophageal manometry (transpulmonary pressure= airway pressure- esophageal pressure)	3 hours
Dead space fraction	Dead space fraction will be calculated by partial pressure arterial/transcutaneous CO2 (PCO2) minus partial pressure of CO2 in mixed expired gas divided by the partial pressure of arterial/transcutaneous CO2	3 hours
Ventilatory ratio	Ventilatory ratio will be calculated as measured minute ventilation multiplied by the measured partial pressure of PCO2 divided (transcutaneous) by the predicted minute ventilation based on ideal body weight multiplied by the ideal PaCO2	3 hours

Collaborators and Investigators

• Sponsor: University of California, San Diego
• Investigators: Principal Investigator: Alex Pearce, University of California, San Diego

Study record dates

Study Major Dates

• Study Start (Actual): July 19, 2022
• Primary Completion (Estimated): December 30, 2026
• Study Completion (Estimated): December 30, 2026

Study Registration Dates

• First Submitted: June 30, 2022
• First Submitted That Met QC Criteria: July 15, 2022
• First Posted (Actual): July 18, 2022

Study Record Updates

• Last Update Posted (Actual): April 11, 2025
• Last Update Submitted That Met QC Criteria: April 8, 2025
• Last Verified: June 1, 2024

More Information

Terms related to this study

• Additional Relevant MeSH Terms: Respiratory Tract Diseases; Respiration Disorders; Congenital Abnormalities; Respiratory Insufficiency; Respiratory System Abnormalities
• Other Study ID Numbers: 801980

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: UNDECIDED

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No
• product manufactured in and exported from the U.S.: No