Preoperative Respiratory Training, Exercise Benefit Patients With MG Undergoing Thymectomy

Preoperative respiratory muscle training (RMT) and aerobic exercise appear to lead to postoperative benefits for people with myasthenia gravis (MG) who undergo thymectomy, according to a new study.

The findings, published in Journal of Cardiothoracic Surgery, provide clarity to an issue that has historically been opaque, according to the investigators.

For many patients with MG, the removal of the thymus gland is an important cornerstone of treatment, often leading to significant or complete remission of symptoms. However, despite minimally invasive techniques, the procedure can lead to postoperative weakness in respiratory and limb skeletal muscles.

“This can result in weak cough and expectoration, respiratory weakness, dyspnea, pneumonia, and atelectasis, and can even induce MG crisis,” wrote the study’s authors.

Early postoperative pulmonary rehabilitation training and aerobic exercise have been shown to provide benefits to patients with MG, the investigators notes, so they sought to find out whether such interventions might provide meaningful benefits when used prior to thymectomy.

The authors used a pool of 80 patients with MG who were scheduled to undergo thymectomy. Half of the patients received moderate to intense preoperative RMT along with aerobic exercise and respiratory physiotherapy and the other 40 patients were considered the control group and received only chest physiotherapy. The authors then compared postoperative outcomes between the groups, including respiratory vital capacity and ability to conduct regular daily activities.

The investigators found significant postoperative drops in vital capacity (VC), forced VC (FVC), FVC in the first second (FEV₁), peak expiratory flow (PEF), and 6-minute walking test scores (6MWT) in the control group, although the FEV₁/FVC ratio was not significantly changed. The intervention group, meanwhile, had significantly higher postoperative VC, FVC, FEV₁, and PEF scores vs the control group. In addition, the authors said patients in the intervention group had higher activity of daily living scores 5 days following surgery compared with the control group. The differences were not significant, however, 1 or 3 days after surgery.

Yet, although the study showed that RMT and exercise had positive effects on respiratory vital capacity and daily life activity, they did not affect the decreases in limb skeletal muscle and exercise capacity following surgery. Likewise, intervention group patients did not have superior 6MWT scores compared with the control group.

This lack of a difference may have to do with the “relatively short” duration of RMT, the authors said. In the intervention group, patients underwent three 15-minute preoperative RMT sessions per day for 5 days. Aerobic training included two 45-minute exercise sessions per day for 5 days.

The investigators conceded that their sample size was small, and they said larger studies will be needed to validate the apparent benefits of preoperative RMT and exercise. For now, however, they said the data suggest RMT and exercise are beneficial and come without the risk of significant adverse effects.

“RMT and aerobic exercise can have positive effects on postoperative respiratory vital capacity and daily life activity and would enhance recovery after surgery in MG patients,” they concluded.

Reference

Chen S, Li X, Wu Y, et al. Preoperative respiratory muscle training combined with aerobic exercise improves respiratory vital capacity and daily life activity following surgical treatment for myasthenia gravis. J Cardiothorac Surg. Published online April 24, 2023. doi:10.1186/s13019-023-02283-5