Recurrence of perforation and overall patient survival after penetrating keratoplasty versus amniotic membrane transplantation in corneal perforation.

PURPOSE: The following is a comparative analysis on the treatment outcomes of corneal perforations using amniotic membrane transplantation (AMT) or penetrating keratoplasty (PK). METHODS: This monocentric retrospective study was performed at the Department of Ophthalmology, University Hospital Ulm, Germany. A total of 78 eyes of 78 patients were included. Thirty-nine eyes received an AMT, and 39 patients were treated with a PK. Primary outcome was recurrence of perforation. Secondary outcomes were patient mortality and visual acuity. RESULTS: No statistically significant difference was observed with regard to a recurrence of perforation between the two groups (26% in AMT vs 23% in PK, p > 0.99). The time of recurrences was within the first two years and did not differ statistically (p = 0.97). In addition, a proportional hazards model with cox regression regarding recurrent perforation showed no significant differences (p = 0.5). After AMT, 41% and after KP, 28% of the patients died during follow-up (p = 0.2), respectively. The Charlson Comorbidity Index (p < 0.0001) and the age at the time of surgery (p = 0.0002) were statistically significantly higher in those who were deceased. A mean follow-up of 485 ± 517 days was recorded. CONCLUSION: Both surgical methods show good results and no statistically significant difference regarding recurrent perforation rate. About a third of the patients died during the follow-up period. The decision regarding the appropriate method should therefore be based on a combination of all factors.

Differences in V˙O2max Measurements Between Breath-by-Breath and Mixing-Chamber Mode in the COSMED K5.

PURPOSE: Automated metabolic analyzers are frequently utilized to measure maximal oxygen consumption (V˙O2max). However, in portable devices, the results may be influenced by the analyzer's technological approach, being either breath-by-breath (BBB) or dynamic micro mixing chamber mode (DMC). The portable metabolic analyzer K5 (COSMED, Rome, Italy) provides both technologies within one device, and the authors aimed to evaluate differences in V˙O2max between modes in endurance athletes. METHODS: Sixteen trained male participants performed an incremental test to voluntary exhaustion on a cycle ergometer, while ventilation and gas exchange were measured by 2 structurally identical COSMED K5 metabolic analyzers synchronously, one operating in BBB and the other in DMC mode. Except for the flow signal, which was measured by 1 sensor and transmitted to both devices, the devices operated independently. V˙O2max was defined as the highest 30-second average. RESULTS: V˙O2max and V˙CO2@V˙O2max were significantly lower in BBB compared with DMC mode (-4.44% and -2.71%), with effect sizes being large to moderate (ES, Cohen d = 0.82 and 1.87). Small differences were obtained for respiratory frequency (0.94%, ES = 0.36), minute ventilation (0.29%, ES = 0.20), and respiratory exchange ratio (1.74%, ES = 0.57). CONCLUSION: V˙O2max was substantially lower in BBB than in DMC mode. Considering previous studies that also indicated lower V˙O2 values in BBB at high intensities and a superior validity of the K5 in DMC mode, the authors conclude that the DMC mode should be selected to measure V˙O2max in athletes.

Inter- and intra-unit reliability of the COSMED K5: Implications for multicentric and longitudinal testing.

PURPOSE: To evaluate the intra-unit (RELINTRA) and inter-unit reliability (RELINTER) of two structurally identical units of the metabolic analyser K5 (COSMED, Rome, Italy) that allows to utilize either breath-by-breath (BBB) or dynamic mixing chamber (DMC) technology. METHODS: Identical flow- and gas-signals were transmitted to both K5s that always operated simultaneously either in BBB- or DMC-mode. To assess RELINTRA and RELINTER, a metabolic simulator was applied to simulate four graded levels of respiration. RELINTRA and RELINTER were expressed as typical error (TE%) and Intraclass Correlation Coefficient (ICC). To assess also inter-unit differences via natural respiratory signals, 12 male athletes performed one incremental bike step test each in BBB- and DMC-mode. Inter-unit differences within biological testing were expressed as percentages. RESULTS: In BBB, TE% of RELINTRA ranged 0.30-0.67 vs. RELINTER 0.16-1.39 and ICC ranged 0.57-1.00 vs. 0.09-1.00. In DMC, TE% of RELINTRA ranged 0.38-0.90 vs. RELINTER 0.03-0.86 and ICC ranged 0.22-1.00 vs. 0.52-1.00. Mean inter-unit differences ranged -2.30-2.20% (Cohen's ds (ds) 0.13-1.52) for BBB- and -0.55-0.61% (ds 0.00-0.65) for DMC-mode, respectively. Inter-unit differences for [Formula: see text] and RER were significant (p < 0.05) at each step. CONCLUSION: Two structurally identical K5-units demonstrated accurate RELINTRA with TE < 2.0% and similar RELINTER during metabolic simulation. During biological testing, inter-unit differences for [Formula: see text] and RER in BBB-mode were higher than 2% with partially large ES in BBB. Hence, the K5 should be allocated personally wherever possible. Otherwise, e.g. in multicenter studies, a decrease in total reliability needs to be considered especially when the BBB-mode is applied.