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.

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

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.