A small-scale pilot randomized controlled trial conducted by the investigators demonstrated some preliminary evidence that inspiratory muscle training (IMT) could be a promising self-management method for alleviating breathlessness. Hence, the aim of this study is to assess the effectiveness of IMT in patients with thoracic malignancies on dyspnea.

The hypothesis of this study is that inspiratory muscle training (IMT) for a three-month treatment will improve dyspnea in lung cancer patients with stable disease experiencing breathlessness.

Plan of Investigation Subjects The sample will be a heterogeneous group of outpatients cared for in a large university medical center in China (Southwest Medical University Hospital).

Methods The trial will be a two-arm, non-blinded, randomized controlled study. Patients will be randomly assigned through a computer program to IMT or a control group by an independent statistician. The IMT group will receive standard care and additionally the IMT intervention. The control group will receive standard treatment.

Study Design Intervention: A pressure threshold device will be used to deliver IMT, which is commercially available by Phillips Respironics. When patients inhale through the IMT device, the valve blocks air flow until the patient generates sufficient inspiratory pressure to overcome the resistance provided by the spring-loaded valve. The patient must generate the inspiratory pressure, in order for the valve to open and allow inhalation of air. The IMT protocol will have five sessions weekly for 12 weeks for 30 mins/day, divided over two sessions.

Procedures Participants will be recruited at the outpatients' clinic of Southwest Medical University Hospital or referred to the research team by the clinicians. Patients allocated to the experimental arm will have training in the IMT use and the trainer (device) will be adjusted to a level which is comfortable to each patient. In the control arm, patients will be visited for completing the study assessments at the same times as in the experimental arm (months 2 & 3).

Sample Size The investigators have used the mBorg score change [primary outcome] in baseline to month three assessment of 0.80 obtained in the pilot study and the established minimally important difference of 1 for the mBorg to calculate sample size requirements, adding a 25% attrition observed in the pilot study. This corresponds to a sample size of 196 subjects.

Data Processing and Analysis The statistical software package IBM SPSS version 23.0 will be used. Descriptive statistics will summarize the sample characteristics. Generalized estimating equations (GEE) models will be used to compare differential changes in the outcomes between the two study arms across multiple time points (baseline-month 2 and month 3 assessment). A p-value of <0.05 was considered statistically significance. Intention-to-treat analysis will be carried out.

Inclusion Criteria:

• adults with histological diagnosis of primary LC or mesothelioma;
• refractory dyspnea not responding to current treatment for the past 2 weeks;
• expected prognosis of >3 months as judged by the clinicians,
• oxygen saturation above 85% at rest.

Exclusion Criteria:

• Those with unstable COPD with frequent or acute exacerbations,
• rapidly worsening dyspnea requiring urgent medical intervention,
• treatment with palliative radiotherapy to the chest received within 4 weeks or chemotherapy within 2 weeks;
• experiencing intractable cough, and those having unstable angina or clinically significant pleural effusion needing drainage