Clinical Trial: Chest Wall Influence on Respiratory System Mechanics in Morbidly Obese Patients

Study Status: Completed
Recruit Status: Completed
Study Type: Observational

Official Title: Chest Wall Influence on Respiratory System Mechanics in Morbidly Obese Patients

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 Summary:

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.


Sponsor: Massachusetts General Hospital

Current Primary Outcome: End Expiratory Lung Volumes [ Time Frame: 2 hours ]

EELV variation at different levels of PEEP in mechanically ventilated and sedated morbidly obese patients and patients with intraabdominal hypertension


Original Primary Outcome: Same as current

Current Secondary Outcome:

  • Respiratory mechanics [ Time Frame: 24 hours ]
    Evaluation of effects of PEEP level set by ICU staff on respiratory mechanics after 24 hours from enrollment Evaluation of PEEP level set by ICU staff
  • Work of breathing [ Time Frame: 20 minutes ]
    Evaluation of work of breathing variation at different level of PEEP during spontaneous breathing and ventilation weaning in morbidly obese patients
  • Respiratory mechanics [ Time Frame: 2 hours ]
    Respiratory mechanics variation at different levels of PEEP in mechanically ventilated and sedated morbidly obese patients and patients with intraabdominal hypertension
  • Gas Exchange [ Time Frame: 2 hours ]
    Gas exchange variation at different levels of PEEP in mechanically ventilated and sedated morbidly obese patients and patients with intraabdominal hypertension
  • Respiratory mechanics [ Time Frame: 20 minutes ]
    Evaluation of respiratory mechanics at different level of PEEP during spontaneous breathing and ventilation weaning in morbidly obese patients
  • Gas exchange [ Time Frame: 20 minutes ]
    Evaluation of gas exchange variation at different level of PEEP during spontaneous breathing and ventilation weaning in morbidly obese patients
  • End Expiratory Lung Volume [ Time Frame: 24 hours ]
    Evaluation of effects of PEEP level set by ICU staff on EELV after 24 hours from enrollment
  • Gas Exchange [ Time Frame: 24 hours ]
    Evaluation of effects of PEEP level set by ICU staff on gas exchange after 24 hours from enrollment


Original Secondary Outcome: Same as current

Information By: Massachusetts General Hospital

Dates:
Date Received: February 12, 2014
Date Started: August 2013
Date Completion:
Last Updated: March 24, 2015
Last Verified: March 2015