A non-invasive method to monitor respiratory muscle effort during mechanical ventilation.

PURPOSE

This study introduces a method to non-invasively and automatically quantify respiratory muscle effort (P) during mechanical ventilation (MV). The methodology hinges on numerically solving the respiratory system's equation of motion, utilizing measurements of airway pressure (P) and airflow (F). To evaluate the technique's effectiveness, P was correlated with expected physiological responses. In volume-control (VC) mode, where tidal volume (V) is pre-determined, P is expected to be linked to P fluctuations. In contrast, during pressure-control (PC) mode, where P is held constant, P should correlate with V variations.

METHODS

The study utilized data from 250 patients on invasive MV. The data included detailed recordings of P and F, sampled at 31.25 Hz and saved in 131.1-second epochs, each covering 34 to 41 breaths. The algorithm identified 51,268 epochs containing breaths on either VC or PC mode exclusively. In these epochs, P and its pressure-time product (PPTP) were computed and correlated with P's pressure-time product (PPTP) and V, respectively.

RESULTS

There was a strong correlation of PPTP with PPTP in VC mode (R² = 0.91 [0.76, 0.96]; n = 17,648 epochs) and with V in PC mode (R² = 0.88 [0.74, 0.94]; n = 33,620 epochs), confirming the hypothesis. As expected, negligible correlations were observed between PPTP and V in VC mode (R² = 0.03) and between PPTP and PPTP in PC mode (R² = 0.06).

CONCLUSION

The study supports the feasibility of assessing respiratory effort during MV non-invasively through airway signal analysis. Further research is warranted to validate this method and investigate its clinical applications.