Chest Wall Influence on Respiratory System Mechanics in Morbidly Obese Patients

Completed

• Conditions: Intra-Abdominal Hypertension; Obesity
• Interventions: Other: Respiratory mechanics assessment

• Registration Number: NCT02105220
• Lead Sponsor: Massachusetts General Hospital

Brief Summary

The goal of this study is to describe the influence of the chest wall on the respiratory system mechanics in morbidly obese patients and in patients with high intra-abdominal pressure.

The effects of increasing and decreasing positive end-expiratory pressure (PEEP) on chest wall and total respiratory system mechanics, lung volumes and gas exchange will be evaluated, both during controlled and assisted mechanical ventilation.

Patients will be studied, first, during the acute phase of respiratory failure, when requiring intubation and controlled mechanical ventilation. Then, patients will be evaluated again during weaning from the ventilator to assess the influence of PEEP in assisted ventilation prior to extubation.

Detailed Description

The goal of this study is to describe the influence of the chest wall on the respiratory system mechanics. Investigators want to describe how extreme obesity and Intra-Abdominal Hypertension (IAH) affect normal respiratory system behavior. The effects of increasing and decreasing positive end-expiratory pressure (PEEP) on respiratory system mechanics, lung volumes and gas exchange will be evaluated, both during controlled and assisted mechanical ventilation.

Investigators will record and compare lung volumes, airway and transpulmonary pressure, gas exchange and hemodynamic changes caused by variations of PEEP. Patients will be studied, first, during the acute phase of respiratory failure, when requiring intubation and controlled mechanical ventilation. Patients will then again be evaluated during weaning from the ventilator to assess the influence of PEEP in assisted ventilation prior to extubation.

Investigators believe that assessment of the transpulmonary pressure and lung volumes is essential to correctly evaluate respiratory system function in patients in which the relationship between the lung and chest wall is altered. Improper mechanical ventilation leads to lung damage. High ventilatory volume/pressure are associated with lung overdistension, while low volume/pressure leads to lung collapse and cyclic opening and closing of alveoli. All of these mechanisms have been associated with ventilator induced lung injury and poorer outcomes. Adequate PEEP and transpulmonary pressure are fundamental in preventing this vicious cycle.

Study Timeline

• Study Start: 2013-08
• Study First Submitted: 2014-02-12
• Study First Submitted QC: 2014-04-02
• Study First Posted: 2014-04-07
• Primary Completion: 2015-01
• Status Verified: 2015-03
• Study Completion: 2015-03
• Last Update Submitted: 2015-03-24
• Last Update Posted: 2015-03-25

Recruitment & Eligibility

• Status: COMPLETED
• Sex: All
• Target Recruitment: 14

Inclusion Criteria

• 18 years or older
• Requiring intubation and mechanical ventilation
• BMI≥40 kg/m2 or IAP≥12 mmHg

Exclusion Criteria

• Known presence esophageal varices
• Recent esophageal trauma or surgery
• Severe thrombocytopenia (PTL≤10,000/mm3)
• Severe coagulopathy (INR≥2)
• Presence of pneumothorax
• Pregnancy
• Patients with diagnosed moderate to severe ARDS or with poor oxygenation index (PaO2/FiO2 < 200 mmHg)

Study & Design

• Study Type: OBSERVATIONAL
• Study Design: Not specified

Arm && Interventions

Group	Intervention	Description
Obese	Respiratory mechanics assessment	We will enroll patients with BMI≥40 kg/m2 to describe the impact of obesity on chest wall compliance and respiratory mechanics. Respiratory mechanics assessment: We will assess respiratory mechanics through different end expiratory pressure settings and recording airway and esophageal pressure tracings.
Intraabdominal Hypertension	Respiratory mechanics assessment	We will enroll patients with IAP≥12 mmHg to describe the impact of intraabdominal hypertension on chest wall compliance and respiratory mechanics. Respiratory mechanics assessment: We will assess respiratory mechanics through different end expiratory pressure settings and recording airway and esophageal pressure tracings.

Primary Outcome Measures

Name	Time	Method
End Expiratory Lung Volumes	2 hours	EELV variation at different levels of PEEP in mechanically ventilated and sedated morbidly obese patients and patients with intraabdominal hypertension

Secondary Outcome Measures

Name	Time	Method
Gas exchange	20 minutes	Evaluation of gas exchange variation at different level of PEEP during spontaneous breathing and ventilation weaning in morbidly obese patients
Gas Exchange	24 hours	Evaluation of effects of PEEP level set by ICU staff on gas exchange after 24 hours from enrollment
Work of breathing	20 minutes	Evaluation of work of breathing variation at different level of PEEP during spontaneous breathing and ventilation weaning in morbidly obese patients
End Expiratory Lung Volume	24 hours	Evaluation of effects of PEEP level set by ICU staff on EELV after 24 hours from enrollment
Respiratory mechanics	20 minutes	Evaluation of respiratory mechanics at different level of PEEP during spontaneous breathing and ventilation weaning in morbidly obese patients

Trial Locations

Locations (1)

Massachusetts General Hospital; 🇺🇸 Boston, Massachusetts, United States