Accuracy of Physical Examination for Assessing Inspiratory Effort During Assisted Ventilation

Insufficient or excessive respiratory effort during assisted ventilation contributes to diaphragm injury and patient self-inflicted lung injury (P-SILI), both of which worsen outcomes. Patients in the transition phase from controlled ventilation to assisted modes are particularly vulnerable because persistent lung injury may drive elevated respiratory effort, pendelluft, and large swings in alveolar pressure. One of the main goals of assisted ventilation is therefore to maintain effort within a physiological range that avoids both over- and under-assistance.

During pressure support ventilation (PSV), direct measurement of respiratory effort requires esophageal pressure monitoring, which is rarely feasible in routine care. Other noninvasive approaches, such as diaphragm ultrasound, lack reproducibility and cannot provide continuous monitoring. Airway occlusion pressure has shown promise for identifying both insufficient and excessive effort, but its performance varies across ventilator models. Additional indices, such as the maximal negative swing of airway pressure during end-expiratory occlusion (∆Pocc), or the pressure-muscle index (PMI), are limited by ventilator constraints.

In clinical practice, respiratory effort is usually judged clinically at the bedside. However, the accuracy of clinical examination for detecting abnormal effort has never been validated. The investigators hypothesize that bedside clinical assessment is unreliable and may expose patients to inappropriate levels of assistance. The primary aim of this investigation was to determine the accuracy of clinical examination in diagnosing abnormal respiratory effort during PSV.

Inclusion criteria

• patients mechanically ventilated for at least 48 hours
• switched to pressure support ventilation within the previous 48 hours

Exclusion criteria

• pregnancy
• legal protection status
• refusal by the patient or relatives to participate