Participants in the intervention group were using a handheld device, Powerbreathe K3, aiming at increasing inspiratory muscle strength by applying an inspiratory resistance. They were instructed to use it twice a day for at least 14 days. Starting load was based on the baseline assessment of the participant's inspiratory muscle strength and increased during the intervention period.

Participants in the control arm were instructed to use a handheld PEP-device traditionally used to facilitate deep breathing. The PEP-device does not provide any inspiratory resistance and therefore, it was considered a sham treatment. The control group were also instructed to use the device twice a day for at least two weeks.

Feasibility will be assessed using two domains: process and scientific feasibility. These domains include several parts such as recruitment rates, time available for training, intervention adherence, patient acceptability, pre-and postoperative respiratory muscle and lung function assessments, reproducibility of assessments, preliminary treatment effect, incidence of PPCs, and adverse events.