Prevalence, Determinants and Consequences of Dyspnea During Weaning in Critically Ill Obese Patients

Research Justification:

ICU patients face numerous sources of discomfort, among which dyspnea- the subjective sensation of breathlessness-stands out as especially distressing. Unlike pain, dyspnea has historically received limited attention, despite its severe psychological impact, including feelings of panic and death anxiety. Dyspnea integrates both physical and psychological suffering, often leading patients to report it as one of the most unbearable experiences, highlighting its significance for ICU caregivers. The subjective nature of dyspnea presents a diagnostic challenge, as it may occur without visible respiratory distress, which complicates detection and management. Dyspnea arises from complex mechanisms, including increased respiratory muscle load from airway resistance or thoracic compliance reduction. Additionally, dyspnea can be induced by an increased need for air due to elevated carbon dioxide levels or reduced oxygen levels, triggering chemoreceptor responses.

For ICU patients mechanically ventilated, the prevalence of dyspnea has been reported between 34 and 47%. Dyspnea assessment tools, such as the Dyspnea-VAS (Visual Analog Scale) and the MV-RDOS (Respiratory Distress Observation Scale), are employed to measure dyspnea, even in intubated patients. These tools are especially useful during ventilator weaning, a critical phase when patients transition to spontaneous breathing. The weaning process, and particularly the spontaneous breathing test (SBT), a test during which the patient breath with the assistance of the ventilator, is critical. The failure of a SBT can increase mortality risk, length of mechanical ventilation and ICU stay.

In this study, the investigators focus in obesity. The growing prevalence of obesity adds an additional layer of complexity to ICU care, as obese patients present distinct challenges during ventilation and weaning. With physiological changes such as reduced lung compliance and increased airway resistance, obese patients have an elevated risk for dyspnea and ventilator weaning complications. Obesity prevalence surged during the COVID-19 pandemic until 40% of ICU patients, and today, up to 50% of obese ICU patients require mechanical ventilation.

In ICU obese patients and mechanically ventilated, there is no assessment of dyspnea, its determinants and its impact during ventilatory weaning. The pathophysiology of dyspnea and SBT failure is complex and primarily involves cardiac function and respiratory muscle function. Pulmonary edema is found in more than half of cases and is linked to the transition from a positive pressure ventilation regime to a negative pressure regime, which creates unfavorable loading conditions for the heart. The second cause described is diaphragmatic dysfunction characterized by atrophy of the respiratory muscles which can occur rapidly under mechanical ventilation. More recently, dyspnea has been described as a cause of SBT and extubation failure in its own right. Other causes have also been described such as intensive care neuropathy, iatrogenic causes (agitation, pain), anxiety, or even impaired ventilatory control.

In addition, the consequences of dyspnea and failure of SBT as well as their management are not described, such as the duration of mechanical ventilation, mortality, length of stay, intercurrent events such as new sepsis. or the administration of new treatments during the period from weaning to extubation.

Finally, the evolution of dyspnea after successful SBT and after extubation has never been described.

The prevalence, determinants and consequences of dyspnea and failure of the first SBT as well as their management in ICU patients with obesity have never been described. Likewise, improving the diagnostic performance of the clinical criteria for SBT failure with the contribution of dyspnea scales is a real challenge in these patients.

Research Design and Methodology:

Study Type: This is a descriptive, monocentric and comparative study.

• Measure of the affective component of dyspnea using the simple numerical dyspnea scale [Срок оценки: Baseline]
• : Presence or onset of dyspnea detected by the Mechanical Ventilation - Respiratory Distress Observation Scale [Срок оценки: Baseline]
• Measure of Rapid Shallow Breathing Index (RSBI) (the ratio of respiratory frequency (f) to tidal volume (TV)) measured at 1 minute of SBT > 105 breaths/min/L. [Срок оценки: Baseline]
• Measure of Pain with Visual Analog Scale (VAS) for pain from 1 to 100 mm (1 means no pain, 100 means major pain) [Срок оценки: Baseline]
• Research of anxiety with Hospital Anxiety and Depression Scale (HADS) from 0 to 21, 0 means no anxiety, 21 means major anxiety, anxiety if HADS > 8 [Срок оценки: Baseline]
• Number of patients with Respiratory Control Impairment: [Срок оценки: Baseline]
• Measure of the number of treatments added during SBT [Срок оценки: Baseline]
• Measure of the number of patients with early cessation of SBT at the patient's request for reasons unrelated to the validated clinical objective criteria for SBT failure; [Срок оценки: Length of the ICU hospitalization (2 months maximum)]
• Measure of number of SBT performed until extubation [Срок оценки: Length of the ICU hospitalization (2 months maximum)]
• Measure of the duration between the first SBT and the extubation [Срок оценки: Length of the ICU hospitalization (2 months maximum)]
• Measure of the number of extubation failure defined by reintubation or death [Срок оценки: Within 7 days following extubation;]
• Measure of the duration of invasive and non-invasive mechanical ventilation [Срок оценки: Length of the ICU hospitalization (2 months maximum)]