The impact of obstructive sleep apnea on exercise capacity in a cardiac rehabilitation program

PURPOSE

Cardiac rehabilitation (CR) improves clinical outcomes in patients with cardiovascular disease (CDV). Patients with CVD often have multiple comorbidities, including obstructive sleep apnea (OSA), potentially affecting their ability to participate and achieve functional improvement during CR. We aimed to test the hypothesis that OSA reduces peak exercise capacity (EC) in patients undergoing CR and to explore if OSA treatment modifies this relationship.

METHODS

Data from a retrospective cohort of CR patients was analyzed. OSA was defined as a respiratory event index > 5/h or physician diagnosis. Patients with OSA were considered "treated" if using continuous positive airway pressure regularly during the CR period. Change in METs was the primary study outcome.

RESULTS

Among 312 CR patients, median age of 67 years, 103 (33%) had known OSA (30 treated, 73 untreated). Patients with OSA vs. those with no OSA were more likely to be obese and male; otherwise, groups were similar. Compared with the no OSA group, patients with OSA had lower pre-CR METs (3.3 [2.9-4.5] vs. 3.9 [3.1-5], P = .01) and lower post-CR METs (5.3 [4-7] vs. 6 [4.6-7.6], P = .04), but achieved a similar increase in METs post-CR (1.8 [0.6-2.6] vs. 2.0 [0.9-3], P = .22). Furthermore, compared to no OSA, pre-CR and post-CR METs tended to be similar in patients with treated OSA, but lower in untreated patients, with similar increases in METs across all groups, even when adjusting for covariates via multivariable regression.

CONCLUSION

OSA is prevalent in patients with CVD undergoing CR. CR substantially improves exercise capacity independent of OSA status, but screening for-and treatment of-OSA may improve the absolute exercise capacity achieved through CR.

A multicentre study comparing two methods for serum free light chain analysis

Background

Serum free light chain analysis is now well established in the investigation of monoclonal gammopathies. In the UK there has, until recently, been a single supplier of kits for such analysis. Recently, a second method using monoclonal antisera was introduced. We have compared the performance of these two kits in four routine laboratories.

Method

Samples submitted for routine analysis (327 samples, 258 [79%] from patients with B-cell lymphoproliferative disease) for serum free light chains were tested by both technologies (Freelite, Binding Site and N Latex FLC, Siemens), according to the manufacturers’ instructions.

Results

Qualitative data were available by both methods on 313 samples for serum free kappa chains and 324 samples for lambda free light chains. We found poor correspondence of 81% for kappa and 74% for lambda. Five percent of samples were significantly discordant in these assays.

Conclusions

These assays perform very differently in clinical practice. They cannot be used interchangeably, especially if monitoring patient responses to therapy.

Susceptibility of selected freshwater fish species to a UK Lactococcus garvieae isolate

Gram-positive cocci recovered from diseased rainbow trout from a farm in England were characterized by different methods, including pulsed field gel electrophoresis, as virulent Lactococcus garvieae serogroup 2 (pulsotype A1). Groups of rainbow trout were kept at a range of temperatures and injected intraperitoneally (i.p.) with one of the UK isolates, L. garvieae 00021. The 18 degrees C and 16 degrees C groups showed 67% and 28% mortality, respectively, by day 27 post-injection. Fish kept at 14 degrees C or lower were less susceptible (< or =3% mortality). Raising the temperature of all groups to 18 degrees C at day 27 post-injection did not result in recurrence of the disease, even though viable bacteria were recovered from all groups 42 days later. Grayling were highly susceptible, with 65% mortalities when challenged with 200 colony forming unit fish(-1) by i.p. injection and 37% mortalities when exposed to effluent water from tanks containing affected rainbow trout. Other fish species tested, Atlantic salmon, brown trout and seven cyprinid species, were less susceptible. Viable L. garvieae was isolated from the internal organs of all species tested at the end of the trials, suggesting that they may pose a threat as possible carriers to susceptible farmed and wild fish.