# Continuous and bilevel positive airway pressure may improve radiotherapy delivery in patients with intra-thoracic tumors

## TL;DR

Using CPAP and BiPAP in patients with chest tumors is feasible and may help reduce tumor movement during radiotherapy.

## Contribution

Demonstrates that BiPAP with a higher backup respiratory rate may be more effective than CPAP in reducing tumor motion during radiotherapy.

## Key findings

- Nine out of ten patients tolerated CPAP and BiPAP settings without major issues.
- CPAP-15 showed the highest increase in end-expiratory lung volume.
- BiPAP with a higher backup respiratory rate may offer the best potential for reducing tumor motion.

## Abstract

•Application of CPAP and BiPAP in patients with intra-thoracic tumors is feasible and tolerable.•Both CPAP and BiPAP may increase end-expiratory lung volume.•Notably, BiPAP with a frequency 3.5 breath/min above spontaneous breathing shows promise, as it may reduce tidal volumes.

Application of CPAP and BiPAP in patients with intra-thoracic tumors is feasible and tolerable.

Both CPAP and BiPAP may increase end-expiratory lung volume.

Notably, BiPAP with a frequency 3.5 breath/min above spontaneous breathing shows promise, as it may reduce tidal volumes.

Minimizing tumor motion in radiotherapy for intra-thoracic tumors reduces side-effects by limiting radiation exposure to healthy tissue. Continuous or Bilevel Positive Airway Pressure (CPAP/BiPAP) could achieve this, since it could increase lung inflation and decrease tidal volume variability. We aim to identify the better CPAP/BiPAP setting for minimizing tumor motion.

In 10 patients (5 with lung cancer, 5 with other intra-thoracic tumors), CPAP/BiPAP was tested with the following settings for 10 min each: CPAP 5, 10 and 15 cmH2O and BiPAP 14/10 cmH2O with a lower (7 breaths/min) and higher back-up respiratory rate (BURR initially 1 breath/min above the spontaneous breathing frequency, with the option to adjust if the patient continued to initiate breaths). Electrical impedance tomography was used to analyse end-expiratory lung impedance (EELI) as an estimate of end-expiratory lung volume and tidal impedance variation (TIV) as an estimate of tidal volume.

Nine out of ten patients tolerated all settings; one patient could not sustain CPAP-15. A significant difference in EELI was observed between settings (χ2 22.960, p < 0.001), with most increase during CPAP-15 (median (IQR) 1.03 (1.00 – 1.06), normalized to the EELI during spontaneous breathing). No significant differences in TIV and breathing variability were found between settings.

This study shows that the application of different settings of CPAP/BiPAP in patients with intra-thoracic tumors is feasible and tolerable. BiPAP with a higher BURR may offer the greatest potential for mitigating tumor motion among the applied settings, although further research investigating tumor motion should be conducted.