Physiological impact of non-invasive respiratory support during acute exacerbation of interstitial lung disease

<bold>Introduction:</bold> Acute exacerbation (AE) is a fatal complication of interstitial lung pneumonia (ILD). We have studied the risk of patient self-inflicted lung injury (P-SILI) with non-invasive respiratory support (NIRS) in AE-ILD, according to the severity of acute respiratory failure (ARF). <bold>Methods:</bold> We conducted a study on a computerized lung representing the characteristics of severe ILD in AE. We studied the impact of face mask (FM), continuous positive airway pressure (CPAP), non-invasive ventilation (NIV) and high flow oxygen therapy (HFOT) according to the severity of ARDS. We studied : tidal volume (TV), end-expiratory lung volume (EELV), lung volume due to positive expiratory pressure (VPEP), total PEEP (PEEP_tot), end-inspiratory transpulmonary pressure (TP_end-inspi) and expiratory (TP_end-exp), total transpulmonary pressure (ΔPTP), driving pressure (ΔP), alveolar strain (strain_alv), mechanical power (MP), work of breathing (WOB) and end-tidal carbon dioxide (ETCO₂). <bold>Results:</bold> In severe ARF, VPEP, PEP_tot, TP_end-exp, TP_end-inspi and ΔP were higher under CPAP and NIV compared with other NIRS. Strainalv and PM exceeded the thresholds of 1.5 ml and 17 J/min, respectively, for all NIRS. For moderate ARF, the trends of the previous parameters were identical except for strain_alv (< 1.5 ml for all NIRS) and PM < 17 J/min for CPAP. For mild ARF, PM and strain_alv were lower under HFOT while ETCO₂ was higher. <bold>Conclusion:</bold> Our results show that the risk of P-SILI under NIRS depends on the severity of the underlying ARF. The assesment of patient's response under NIRS appears essential to reduce the risk of P-SILI and may be estimate by the ETCO₂.