2249 - Breathing Control in RadioTHerapy Using Non-Invasive Mechanical Ventilation; The BreaCoRTH Study
Presenter(s)
I. W. van Dijk1, J. K. Veldman1, M. Parkes1, M. F. Stevens2, J. G. van den Aardweg3, N. Bijker1, P. Cobussen1, E. Versteijne1, J. Visser4, Z. van Kesteren1, and A. Bel4; 1Department of Radiation Oncology, Cancer Center Amsterdam, Amsterdam UMC, University of Amsterdam, Amsterdam, Netherlands, 2Department of Anesthesiology, Amsterdam UMC, University of Amsterdam, Amsterdam, Netherlands, Amsterdam, Netherlands, 3Department of Pulmonology, Amsterdam UMC – location University of Amsterdam, Amsterdam, Netherlands, 4Radiation Oncology, Amsterdam UMC location University of Amsterdam, Meibergdreef 9, Amsterdam, Netherlands
Purpose/Objective(s): For respiratory motion management in thoracic and upper abdominal radiotherapy PTV margins are enlarged and/or patients receive breath hold instructions. Alternatively, we aim to account for this motion during radiotherapy by applying non-invasive mechanical ventilation (NIMV) supported breathing control.
Materials/Methods: In 22 healthy volunteers (median age 50, range 19–67 years), we investigated the effect of NIMV-induced regularized breathing at 60 breaths per minute (brpm) with 15cmH2O positive end expiratory pressure (RB60+PEEP), and prolonged breath-holding (PBH) of =5 minutes. During the PBH, volunteers were instructed to take a sip of air to compensate (i.e. cPBH) for the gradual lung deflation as an effect of blood gas exchange, causing a diaphragm drift in cranial direction. Volunteers practiced NIMV in two sessions. Thereafter, MR images were acquired to assess which breathing control strategy maximally reduced motion of the right diaphragm dome. RB60+PEEP was further investigated in 18 patients (median age 59, range 44-77 years) with left-sided breast cancer, who had one training session and one MRI session. Oxygen saturation (SpO2), and end-tidal carbon dioxide (petCO2) were monitored throughout all interventions. Comfort was assessed using a 5-points Likert scale (0, uncomfortable; 4, very comfortable).
Results: Although regular triggering of the ventilator during cPBH (mean duration 5.9, range 1.6-9.5 minutes) partly compensated the gradual lung deflation, substantial intrafraction position variation of the diaphragm occurred. RB60+PEEP reduced the median motion of the right diaphragm by 70% (IQR 59%-80%). Imaging also showed stable diaphragm and organ positions resulting from increased lung volumes. Hence, in 16 patients RB60+PEEP was considered the most promising strategy and appeared to be equally effective as multiple short breath holds. Moreover, two patients who were not able to repeatedly breath hold for 20s, tolerated RB60+PEEP without problems. SpO2 and petCO2 levels never violated the predefined safety limits during RB60+PEEP and PBH. Over all sessions, healthy volunteers rated RB60+PEEP (mean score 2.7) slightly less comfortable than cPBH (mean score, 3.3). In 80% of the sessions, patients scored RB60+PEEP as comfortable to very comfortable (scores 3 to 4).
Conclusion: Regularized breathing at 60 brpm with PEEP was well tolerated by all volunteers and patients, also by the two patients who were unable to breath hold repeatedly for 20s. The optimal strategy appeared to be regularized breathing at 60 brpm with PEEP, representing an excellent compromise between patient comfort and minimizing respiratory motion.