Measurements

Height (in cm) and weight (in kg) were measured with a wall-mounted stadiometer and a body composition analyzer (BC-118D; Tanita Co., Ltd., Tokyo, Japan), respectively. Body mass index (BMI) was calculated by dividing the body weight (in kg) by the height (in m) squared.

A standard adjustable-handle dynamometer (T.K.K. 5101; TAKEI Scientific instruments Co. Ltd., Niigata, Japan) was used for measuring handgrip strength as the index of upper-limb muscle strength and was set at the second grip position for all patients. Grip strength was measured with the same handgrip dynamometer, and the examination was performed by the same physical therapist. Attention was paid to a possible Valsalva effect, and the grip strength of both the hands was measured. The measured data were used as the index of handgrip strength (kilogram-force [kgf]).

Hand-held dynamometers (HHD; μ-tas MT1; ANIMA Co., Tokyo, Japan) were used for measuring knee extensor muscle strength as an index of lower-limb muscle strength. In all sessions, a HHD equipped with a stabilizing belt that the tester held was used when applying resistance. The HHD was used in the manual mode using kgf units. A previous study showed that the intraclass correlation coefficients (ICC) was .98 with a belt and .04 without a belt.²² In a reliability test-retest of the belt-restrained HHD, ICCs ranged from .94 to .96.²³ Knee extension force was tested in a sitting position with the knee flexed at approximately 90°. The dynamometer was applied just proximal to the malleoli. The maximum force during 10 seconds of effort was recorded in kgf. The HHD was reset to kgf at the start of each measurement. Two measurements were conducted for each leg, and the higher value of the 2 measurements was selected for analysis.

Submaximal exercise capacity was assessed using the 6MWD measured according to the American Thoracic Society guidelines.²⁴ Patients walked up and down a 20-m corridor for 6 minutes at their own pace. They were encouraged to cover as much distance as possible but were permitted to rest as required and to continue walking as soon as they felt able to or to stop if they experienced symptoms of dyspnea or leg pain.²⁵ The following data were collected and analyzed: distance after 6 minutes (in m), duration (in minutes), and heart rate at initiation and 6 minutes.²⁶

Pulmonary function was assessed with spirometry (Minato Autospiro AS-302; Minato Medical Science Co., Ltd., Osaka, Japan) and was measured according to the American Thoracic Society guidelines.²⁷ FVC and FEV1 were expressed in liters.

HRQOL was assessed with the SF-36 by the direct questioning of participants. Thus, those who were too confused or too dysphasic to answer were excluded. This self-administered questionnaire has been widely used and validated in the Japanese general population²⁸ and in patients who underwent P/D. The SF-36 assesses physical and mental health components in 8 domains: physical functioning (PF), physical role functioning (RP), bodily pain (BP), general health perceptions, vitality (VT), social role functioning (SF), emotional role functioning, and mental health (MH). The SF-36 measures the multidimensional properties of HRQOL on a scale of 0–100, with higher scores indicating better HRQOL. Health utility was assessed using the Short-Form Six-Dimension (SF-6D). The SF-6D measures the strength of preference for a particular health state and are represented as a number between 0 and 1, with 0 equivalent to death and 1 equivalent to being alive for a year in perfect health. After patients were assessed with the SF-36, the scores were converted to mean SF-6D utility scores by iHope International Co. Ltd. (Kyoto, Japan) based on techniques used in previous reports.^29-31