Exercise improvement after pectus excavatum repair is not related to chest wall function.

OBJECTIVES: In patients undergoing corrective surgery for pectus excavatum, there is evidence of improvement in cardiopulmonary function. It is unclear how much of this improvement is attributable to improved chest wall function. Thus, we observed changes in chest wall function in response to an incremental load exercise pre- and postoperatively. METHODS: Using optoelectronic plethysmography, total and regional chest wall volumes were measured in 7 male patients with severe pectus excavatum who underwent a Nuss correction. Rib cage and abdominal volumes were recorded at rest and during exercise (incremental cycle ergometry), pre- and postoperatively in conjunction with spirometry. RESULTS: Tidal volume increases during exercise are blunted compared with baseline measurements at 6 days (-36 ± 7%) partially recovering at 6 months postoperatively (-18 ± 22%). This is mirrored by changes in spirometry. Tidal volume decreased during exercise initially in all compartments, but persisted in the rib cage compartment. An increase of 44% (P = 0.009) in exercise tolerance was found 6 months after surgical correction. CONCLUSIONS: Six months after Nuss correction in pectus patients, there was a decrease in rib cage mobility. Despite reduction, patients had a significant improvement in exercise tolerance. Therefore, we conclude that early postoperative improvement in exercise capacity is not due to changes in chest wall function. The longer term effects on chest wall function are yet to be defined.

Verbal protocols for assessing the usability of clinical decision support: the retrospective sense making protocol.

We compare the effectiveness of two types of verbal protocol, concurrent think aloud vs. retrospective sense making, for evaluating the usability of a clinical decision support tool. Thirty-five medical and nursing students participated in a usability experiment. Participants were asked to complete seven tasks using the system under evaluation. Eighteen students were allocated to the concurrent think aloud group and the remainder followed the retrospective protocol. The retrospective protocol was significantly more sensitive than the concurrent protocol in recording unique usability problems related to users' cognitive behaviour. These problems concerned the interpretation and comprehension of statistical output, search results and system messages. These findings can be explained by the retrospective protocol's greater ability to detect compound usability problems, capturing the cognitive dimensions of users' interactions with the interface in greater depth. Evaluations of clinical decision support systems should take an evidence-based approach to selecting protocols.