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

Inclusion criteria:

• Adults of either sex (≥18 years)
• Non-c0mmunicative, endotracheally intubated in the past 24 hours.
• Expected to require ≥24 hours of mechanical ventilation.

Exclusion criteria:

• Continuous neuromuscular blockade.
• Ventilated on Airway Pressure Release Ventilation mode.

Ventilator measured airway pressure and flow signals will be streamed at 31.25 Hz into 131.1-s time windows (epochs) for up to 5 days. A recursive algorithm will compute individual breath's inspiratory effort (Pmus) and calculate the inspiratory effort time-pressure product (PmusPTP cmH₂O·s·min-¹).

Trained staff will assess the Mechanical Ventilation-Respiratory Distress Observation Scale (MV-RDOS), an intermittent and subjective assessment of dyspnea, at least twice daily. These will be time-matched to the airway signal epochs to determine their degree of correlation by Pearsons R2.

Using receiver operating characteristic (ROC) area under the curve (AUC) analysis, the investigators will determine a dyspnea threshold for PmusPTP equivalent to the dyspnea cut-off for MV-RDOS > 2.6, and report sensitivity/specificity.

To address possible label misclassification, the investigators will train six supervised classifiers on concordant data pairs and apply a unanimity ensemble to label discordant pairs as "dyspneic", not dyspneic" and undetermined". Ensemble determined labels conflicting with those classified by MV-RDOS will be excluded from a secondary analysis.

Primary outcome will be Pearson's R2 (PmusPTP vs MV-RDOS). Secondary outcome will be 28-day ventilator-free days.

Inclusion criteria:

• Adults of either sex (≥18 years)
• Endotracheally intubated in the past 24 hours.
• Expected to require ≥24 hours of mechanical ventilation.

Exclusion criteria:

• Continuous neuromuscular blockade.
• Ventilated on Airway Pressure Release Ventilation mode.

Adults of either sex with respiratory failure of any cause on invasive mechanical ventilation.

1. Excel workbook containing deidentified enrollment information including demographics, mode of ventilation, adverse events during monitoring and outcomes. Also provided will be individual MV-RDOS measurements with time and day after enrollment.
2. Excel workbook containing paired MV-RDOS measurements and calculated PmusPTP.
3. Results of machine learning models application to study data.
4. Program used to develop the machine learning models.

January 1, 2026 through December 31, 2026

Data are available to qualified investigators on reasonable request by emailing the principal investigator