Background <p>Ventilatory support levels in ICU patients should be tailored to both optimal gas exchange and respiratory muscle loading, as over- and underassistance may cause diaphragm dysfunction. The diaphragm’s capacity to overcome mechanical load and deliver ventilatory output is reflected by the patient’s neural respiratory drive (NRD), tidal volume (TV) and respiratory rate (RR). Surface electromyography of the diaphragm (sEMGdi) offers a continuous, non-invasive measure of NRD. We investigated the effect of pressure support (PS) level on the coupling of diaphragm electrical activity (sEAdi) and ventilatory output during the ICU stay.</p> Methods <p>In clinically stable ICU patients (<i>N</i> = 17), four PS-levels were applied on alternate days, based on the clinical value (− 3, + 0, + 3, and + 6 cmH₂O). sEAdi time-product (ETPdi) was calculated from high-quality sEAdi waveforms, using a novel, advanced signal analysis approach. The breath-by-breath correlation between ETPdi and TV was defined as neuro-ventilatory coupling (NVC), enabling quantification of the neuro-ventilatory response.</p> Results <p>On group level (13 patients, 26 PS-trials), ETPdi and RR increased with decreasing PS-levels (2.4 and 1.6 percentage point (pp)/cmH₂O), whereas TV decreased (2.5&#xa0;pp/cmH₂O). Longitudinal analysis (4 patients, 14 PS-trials) showed strengthened coupling between ETPdi and TV during weaning, reflected by an increase in median NVC from 3.4% (IQR 2.9) to 26.3% (IQR 21.7) between the first and last PS-trial.</p> Conclusion <p>Advanced sEMGdi analysis allows for non-invasive quantification of NVC, reflecting the diaphragm’s capacity to overcome mechanical load. In patients approaching liberation from MV, increasing NVC indicates the shift from near-passive to active breathing. This study demonstrates the potential of NVC to inform tailoring of ventilatory support levels.</p> <p><i>Trial registration</i> number: Dutch Trial Register NL9654. Registered August 05, 2021.</p>