The goal of this pilot clinical trial is to assess the feasibility of smartphone-based telerehabilitation for inspiratory muscle training (IMT) and to explore its preliminary effects on postoperative recovery in high-risk adult patients after lung resection. Eligible participants are adults aged 19 years or older who underwent lung resection and met at least one high-risk criterion: preoperative forced expiratory volume in 1 second (FEV1) or diffusing capacity of the lung for carbon monoxide (DLCO) of 70% predicted or less, or age 65 years or older. The main questions it aims to answer are:

Is smartphone-based telerehabilitation for IMT feasible and safe in this patient population? Does smartphone-based telerehabilitation for IMT show preliminary effects on functional exercise capacity, as measured by the 6-minute walk test (6MWT)? Researchers will compare smartphone-based telerehabilitation IMT with unsupervised home-based IMT to see whether remote supervision provides additional benefit after lung resection.

Participants will:

be randomized to either smartphone-based telerehabilitation IMT or unsupervised home-based IMT perform IMT 5 days per week for 6 weeks, starting at 20% of postoperative maximal inspiratory pressure (MIP) with progression according to tolerance complete outcome assessments at postoperative weeks 2-4, 8-10, and 14-16, including the 6MWT, pulmonary function tests (FVC, FEV1, MIP, and peak expiratory flow), handgrip strength, body composition, patient-reported outcomes, and cardiopulmonary exercise testing at final follow-up

Eligible patients who undergo lung resection will be screened during postoperative hospitalization and before their first outpatient visit to the Department of Rehabilitation Medicine. To be eligible, participants must be adults aged 19 years or older, have undergone lung resection, meet at least one of the following high-risk criteria: preoperative forced expiratory volume in 1 second (FEV1) or diffusing capacity of the lung for carbon monoxide (DLCO) of 70% predicted or less, or age 65 years or older, and be able to understand the study procedures and provide written informed consent. Within 7 days after surgery and before hospital discharge, informed consent will be obtained and participants will be randomized in a 1:1 ratio to either the intervention or control group.

At postoperative weeks 2-4 (Visit 1), both groups will attend an outpatient visit for baseline assessments, including the 6-minute walk test (6MWT), pulmonary function tests (FVC, FEV1, MIP, and peak expiratory flow [PEF]), handgrip strength, body composition (InBody), EQ-5D, the Korean version of the Physical Activity Scale for the Elderly (K-PASE), and the Numeric Rating Scale (NRS) for pain. All participants will be instructed to continue the standard pulmonary rehabilitation program initiated during hospitalization, including breathing exercises, coughing techniques, early ambulation, and low-intensity aerobic exercise.

The intervention group will perform inspiratory muscle training (IMT) 5 days per week (10 repetitions × 10 sets per day) for 6 weeks. Training will begin at 20% of postoperative maximal inspiratory pressure (MIP) and will be adjusted according to tolerance and symptoms, with a target of 50% of postoperative MIP and an upper limit of 4 on the Borg Dyspnea Scale. Smartphone-based telerehabilitation will be delivered through a mobile messenger application (e.g., KakaoTalk) and will include twice-weekly adherence and symptom monitoring, therapist feedback, and remote support for training progression. Communication will primarily be conducted through messaging, with telephone contact used as needed. Participants will also be able to contact the research team to ask questions or report adverse events during the intervention period, and the research team will respond within 24 hours.

The control group will perform the same IMT protocol for 6 weeks after a one-time instruction session at Visit 1, but without additional remote monitoring. Training will also begin at 20% of postoperative MIP, and participants will adjust the intensity independently based on tolerance. They will be instructed to reduce the load if they are unable to complete the prescribed training volume at the increased intensity.

Follow-up assessments will be conducted at postoperative weeks 8-10 (Visit 2) and 14-16 (Visit 3). Visit 2 will include reassessment of the same parameters measured at Visit 1 and review of exercise adherence. Visit 3 will include final outcome assessments and cardiopulmonary exercise testing (CPET).

Inclusion Criteria:

1. Adults aged 19 years or older

2. Patients who underwent lung resection

3. Patients who met at least one of the following high-risk criteria:

   • preoperative FEV1 or DLCO ≤70% predicted
   • age ≥65 years

4. Patients who understood the study procedures and provided written informed consent

Exclusion Criteria:

1. Pregnant women or other vulnerable populations considered inappropriate for study participation
2. Patients with limited mobility due to other conditions that could interfere with the exercise stress test or 6-minute walk test (e.g., osteoarthritis, spinal disorders, or cerebral infarction)
3. Patients with an implanted pacemaker or defibrillator that precluded bioelectrical impedance analysis
4. Patients participating in other clinical studies that could affect exercise capacity
5. Patients unable to independently use the messenger application (KakaoTalk) after standardized instruction
6. Patients judged by the investigator to be unsuitable for participation