A55-52 Inspiratory Effort as a Continuous Marker of Dyspnea During Mechanical Ventilation

Rationale

Dyspnea is common during invasive mechanical ventilation but is difficult to assess in non-communicative patients. The Mechanical Ventilation-Respiratory Distress Observation Scale (MV-RDOS) is validated for observational assessment in this population but is intermittent and observer-dependent.Objectives: To evaluate whether inspiratory muscle effort, quantified as the pressure-time product of respiratory muscle pressure (PmusPTP) and derived continuously and noninvasively from ventilator waveforms, is associated with intermittent MV-RDOS assessments.

Methods

Two-center prospective observational study in 45 adults receiving invasive mechanical ventilation unable to reliably self-report dyspnea. MV-RDOS was assessed at least twice daily for up to five days. Airway flow and pressure were recorded continuously, and PmusPTP was computed for sequential 131-second airway waveform epochs and time-matched to MV-RDOS assessments. We evaluated discrimination of MV-RDOS-defined respiratory distress (MV-RDOS >2.6) using receiver-operating-characteristic analysis and described the association between PmusPTP and MV-RDOS.

Measurements and Main Results

Among 281 time-matched MV-RDOS-PmusPTP pairs, PmusPTP showed discrimination for MV-RDOS >2.6 with an area under the curve of 0.741 (95% CI 0.663-0.820). Youden-optimal operating point was PmusPTP = 20 cmH₂O·s·min⁻¹ (sensitivity 0.59; specificity 0.88). The linear association between MV-RDOS and PmusPTP was moderate (R² = 0.36; p < 0.001), with substantial dispersion.

Conclusions

Continuous noninvasive estimation of inspiratory PmusPTP from ventilator waveforms yields a physiological index that is moderately associated with intermittent MV-RDOS in non-communicative mechanically ventilated adults. These findings support the feasibility of continuous inspiratory-effort monitoring and suggest further studies to determine how such measures may complement observational and patient-reported dyspnea assessments.

This abstract is funded by: None