Clinical Research Directory

Association of Inspiratory Effort With Dyspnea During Assisted Mechanical Ventilation in Critically Ill Patients

During assisted mechanical ventilation, breathing results from the interaction between the patient and the ventilator. Optimal titration of pressure support is essential to maintain a balance between over-assistance and under-assistance. Excessive respiratory may lead to dyspnea and cause respiratory muscle fatigue, whereas excessive assistance promotes muscle atrophy and delays weaning. Although normal inspiratory effort values in healthy subjects are well defined, acceptable limits in critically ill patients remain unclear. Inspiratory effort is traditionally quantified by the pressure-time product (PTP), but its measurement is technically demanding. Simpler indices such as swings of esophageal pressure (δPes) and airway occlusion pressure at 100 ms (P0.1) are used more often, both with important limitations. Dyspnea, a frequent and distressing symptom among mechanically ventilated critically ill patients, may serve as a physiological marker of unacceptably high effort. This single-center prospective observational study conducted in the intensive care unit (ICU) of the University Hospital of Heraklion aims to (1) determine whether the ratio mean to maximal inspiratory pressure (Pmean/Pmax) correlates more strongly with dyspnea intensity than PTP, δPmus, P0.1 and (2) identify a Pmean/Pmax threshold predictive of clinically significant dyspnea. These findings are expected to define objective upper limits of acceptable inspiratory effort and guide ventilator titration to improve patient comfort and safety.

Mechanical Ventilator Adjustments and Patient Dyspnea

In the past 5 years, there are increasing data suggesting that patients treated with mechanical ventilation experience shortness of breath, despite appropriate sedation. This adverse experience is believed to contribute to the finding that up to 25% of patients who survive severe respiratory diseases experience mental health problems including post traumatic distress syndrome (PTSD). The purpose of this study is to evaluate if/how sequential changes in the delivery of mechanical ventilation affect shortness of breath sensation in awake patients requiring mechanical ventilation. Improving the knowledge of the impact of the patient-ventilator interaction on shortness of breath sensation may lead to strategies to improve the comfort of non-sedated and sedated ventilated patients, and thereby reduce mental health sequelae in survivors of acute severe respiratory diseases The investigators hypothesize that current ventilator strategies, particularly reduced tidal volume (size of breath given by the ventilator) utilized in managing patients with severe respiratory diseases, contribute to shortness of breath in patients with increased drive to breathe. In this setting, some safe ventilator changes may improve or worsen the shortness of breath sensation in awake patients on mechanical ventilation.

Automatic Detection of Dyspnea in Mechanically Ventilated, Critically Ill Patients

The investigators will conduct a prospective, observational, two-center ICU study of 60 subjects on mechanical ventilation with respiratory failure of any cause.