Author: Sophie Boisbouvier, David Cobben, Anthony L Criscuolo, Michael W. Kissick, Mark Ramtohul, Gordon Sands, Tracy Underwood 👨🔬
Affiliation: University of Surrey, Department of Medical Physics, Queen Elizabeth Hospital, Lung Cancer and Sarcoma Radiotherapy, The Clatterbridge Cancer Centre, Leo Cancer Care, Radiotherapy department, Centre Léon Bérard 🌍
Purpose:
Pulmonary function tests (PFTs) help assess treatment options for lung cancer patients. Conventionally, these are undertaken upright, whereas radiotherapy is administered supine. This study compared the impact of supine and upright RT treatment positions on the differences between PFTs, deep inspiration breath hold (DIBH) lengths, and chest surface motion.
Methods:
Following Research Ethics Committee approval, participants (10 male, 11 female, aged 22-66, no COPD or asthma) were immobilised with arm supports on a demonstration version on an upright patient positioning system (Leo Cancer Care) and on a radiotherapy couch top, completing supine and upright positions in each session. To prevent bias from practice or fatigue, the position was alternated.
The protocol included tidal breathing (two minutes), three vital capacity (VC), DIBH at 80% of inspiratory capacity (IC) ±0.2L for maximum duration, four peak expiratory flow (PEF), and four forced expiratory volume in one second (FEV1). An Asma-1 respiratory monitor (Vitalograph) and SDX spirometer (DYN’R) were used to conduct PFTs. A structured light grid, Thora-3Di (PneumaCare), was used for surface motion capture.
Results:
All participants achieved 25-second DIBHs in both positions, yet the maximum duration was greater in supine (p=0.003). Two-tailed t-tests found that expiratory reserve volume (p<0.001), VC (p=0.003), FEV1 (p<0.001) and FEV1/VC (p<0.001) were all statistically larger upright. IC (p<0.001) was greater supine. There was no difference (p=0.63) in breath-hold stability between positions
Conclusion:
This study was the first that combined spirometry-guided and surface-guided radiotherapy methods in the to characterise and compare breathing volumes and surface motions in upright and supine radiotherapy treatment positions. Treatments in the upright position could lead to easier breathing and less respiratory obstruction.. During tidal breathing, lung volume is greater in upright than supine, which could result in a lower mean lung dose for patients. The maximum length DIBH is greater in supine.