Diffusing Capacity and Mortality in Chronic Obstructive Pulmonary Disease

Rationale: Chronic obstructive pulmonary disease (COPD) mortality risk is often estimated using the BODE (body mass index, obstruction, dyspnea, exercise capacity) index, including body mass index, forced expiratory volume in 1 second, dyspnea score, and 6-minute walk distance. Diffusing capacity of the lung for carbon monoxide (DlCO) is a potential predictor of mortality that reflects physiology distinct from that in the BODE index. Objectives: This study evaluated DlCO as a predictor of mortality using participants from the COPDGene study. Methods: We performed time-to-event analyses of individuals with COPD (former or current smokers with forced expiratory volume in 1 second/forced vital capacity < 0.7) and DlCO measurements from the COPDGene phase 2 visit. Cox proportional hazard methods were used to model survival, adjusting for age, sex, pack-years, smoking status, BODE index, computed tomography (CT) percent emphysema (low attenuation areas below -950 Hounsfield units), CT airway wall thickness, and history of cardiovascular or kidney diseases. C statistics for models with DlCO and BODE scores were used to compare discriminative accuracy. Results: Of 2,329 participants, 393 (16.8%) died during the follow-up period (median = 4.9 yr). In adjusted analyses, for every 10% decrease in DlCO percent predicted, mortality increased by 28% (hazard ratio = 1.28; 95% confidence interval, 1.17-1.41, P < 0.001). When compared with other clinical predictors, DlCO percent predicted performed similarly to BODE (C statistic DlCO = 0.68; BODE = 0.70), and the addition of DlCO to BODE improved its discriminative accuracy (C statistic = 0.71). Conclusions: Diffusing capacity, a measure of gas transfer, strongly predicted all-cause mortality in individuals with COPD, independent of BODE index and CT evidence of emphysema and airway wall thickness. These findings support inclusion of DlCO in prognostic models for COPD.

Pulmonary arterial pruning is associated with CT-derived bronchiectasis progression in smokers

Loss of small pulmonary arteries measured as the ratio of blood vessel volume in arteries <5 mm2 in cross-section to total arterial blood vessel volume (BV5a/TBVa), with lower values indicating more pruning, was associated with 5-yr progressing CT-derived bronchiectasis in smokers (Odds Ratio (OR) [95% Confidence interval], 1.28 [1.07-1.53] per 5% lower BV5a/TBVa, P = 0.007). Corresponding results in smokers with COPD were: OR 1.45 [1.11-1.89] per 5% lower BV5a/TBVa, P = 0.007. The results support a vascular factor for structural progression of bronchiectasis.

Transforaminal Endoscopic Lumbar Discectomy and Foraminotomy with Modified Radiofrequency Nerve Stimulator and Continuous Electromyography Under General Anesthesia

BACKGROUND

Transforaminal endoscopic lumbar approaches involve working in Kambin's triangle. These procedures are performed on awake patients or under general anesthesia with continuous electromyography. Potential morbidity of this approach includes injury to exiting and traversing nerve roots, as substantial dissection or cauterization of overlying tissues is required for visualization.

METHODS

We developed a novel connection system that accepts input from a bipolar radiofrequency probe to allow direct nerve stimulation in conjunction with electromyography. This study included 30 consecutive patients undergoing transforaminal endoscopic lumbar approaches for discectomies (73.3%), foraminal stenosis (23.3%), or lateral recess stenosis (3.3%). Demographic, operative, and outcomes data were collected.

RESULTS

Average age of patients was 61.4 years, and the L4-5 segment was most commonly treated (65.6%). Electrophysiologic mapping of the exiting nerve root was attempted in 28 patients with an average stimulation threshold of 8.6 ± 0.9 mA. Mapping of the traversing nerve root was attempted in 12 patients with an average stimulation threshold of 6.0 ± 0.8 mA. There were no instances of new postoperative sensorimotor deficits or dysesthesia. These findings persisted through mean and median follow-up of 294 days and 165 days, respectively. No patient required subsequent lumbar surgery.

CONCLUSIONS

Our modified instrumentation and technique allow for accurate identification of the exiting and traversing nerve roots with minimal changes to the workflow of transforaminal endoscopic lumbar approaches. Modification of a bipolar radiofrequency device connection arrangement is simple, inexpensive, and reusable. In this study, no patients developed injury or pain related to nerve root dysfunction.

Diffusing Capacity of Carbon Monoxide in Assessment of COPD

BACKGROUND

Diffusing capacity of the lung for carbon monoxide (Dlco) is inconsistently obtained in patients with COPD, and the added benefit of Dlco testing beyond that of more common tools is unknown.

OBJECTIVE

The goal of this study was to determine whether lower Dlco is associated with increased COPD morbidity independent of emphysema assessed via spirometry and CT imaging.

METHODS

Data for 1,806 participants with COPD from the Genetic Epidemiology of COPD (COPDGene) study 5-year visit were analyzed, including pulmonary function testing, quality of life, symptoms, exercise performance, and exacerbation rates. Dlco percent predicted was primarily analyzed as a continuous variable and additionally categorized into four groups: (1) Dlco and FEV₁ > 50% (reference); (2) only Dlco ≤ 50%; (3) only FEV₁ ≤ 50%; and (4) both ≤ 50% predicted. Outcomes were modeled by using multivariable linear and negative binomial regression, including emphysema and FEV₁ percent predicted among other confounders.

RESULTS

In multivariable analyses, every 10% predicted decrease in Dlco was associated with symptoms and quality of life (COPD Assessment Test, 0.53 [P < .001]; St. George's Respiratory Questionnaire, 1.67 [P < .001]; Medical Outcomes Study Short Form 36 Physical Function, -0.89 [P < .001]), exercise performance (6-min walk distance, -45.35 feet; P < .001), and severe exacerbation rate (rate ratio, 1.14; P < .001). When categorized, severe impairment in Dlco alone, FEV₁ alone, or both Dlco and FEV₁ were associated with significantly worse morbidity compared with the reference group (P < .05 for all outcomes).

CONCLUSIONS

Impairment in Dlco was associated with increased COPD symptoms, reduced exercise performance, and severe exacerbation risk even after accounting for spirometry and CT evidence of emphysema. These findings suggest that Dlco should be considered for inclusion in future multidimensional tools assessing COPD.

Infra-Conus Single-Level Laminectomy for Selective Dorsal Rhizotomy: Technical Advance

BACKGROUND/AIMS

Selective dorsal rhizotomy for spastic cerebral palsy is an effective and well-validated surgical approach. Multiple techniques have been described in the past including multiple laminectomies and a single-level laminectomy at the level of the conus. There is considerable technical challenge involved with a single-level laminectomy approach.

METHODS

We report here a modification of the single-level laminectomy that selectively analyzes each individual nerve root with electromyography to separate dorsal and ventral nerve roots through comparison of stimulus responses.

RESULTS

In 18 children with cerebral palsy who underwent this operation there was a mean improvement in the Modified Ashworth Scale of 2.0 with no reported incidence of muscle weakness, sensory loss, or neurogenic bladder.

CONCLUSION

This approach allows for a modification of selective dorsal rhizotomy through a single-level laminectomy and tailors the selection of nerve root sectioning to the individual patient of interest while still maintaining its effectiveness.

Human motor evoked potential responses following spinal cord transection: an in vivo study

Motor evoked potential (MEP) monitoring has been used increasingly in conjunction with somatosensory evoked potential monitoring to monitor neurological changes during complex spinal operations. No published report has demonstrated the effects of segmental spinal cord transection on MEP monitoring.

The authors describe the case of an 11-year-old girl with lumbar myelomeningocele and worsening thoracolumbar scoliosis who underwent a T11–L5 fusion and spinal transection to prevent tethering. Intraoperative MEP and somatosensory evoked potential monitoring were performed, and the spinal cord was transected in 4 quadrants. The MEPs were lost unilaterally as each anterior quadrant was sectioned.

This is the first reported case that demonstrates the link between spinal cord transection and MEP signaling characteristics. Furthermore, it demonstrates the relatively minor input of the ipsilateral ventral corticospinal tract in MEP physiology at the thoracolumbar junction. Finally, this study further supports the use of MEPs as a specific intraoperative neuromonitoring tool.

Left iliac artery injury during anterior lumbar spine surgery diagnosed by intraoperative neurophysiological monitoring

Serious vascular injury is a rare, but potentially devastating complication during anterior lumbar spinal surgery. The authors describe the first reported case where vascular injury was detected by multimodality neurophysiological monitoring during an L3-S1 anterior lumbar interbody fusion. The case demonstrates the need for multi-modality monitoring and the combined use of somatosensory-evoked potentials and motor-evoked potentials.

Prevalence and correlates of depression in individuals with and without type 1 diabetes

OBJECTIVE

Depression is associated with poor glycemic control and complications in people with type 1 diabetes. We assessed the prevalence of depression and antidepressant medication use among adults with and without type 1 diabetes and the association between depression and diabetes complications.

RESEARCH DESIGN AND METHODS

In 2006-2008, the Coronary Artery Calcification in Type 1 Diabetes Study applied the Beck Depression Inventory II (BDI-II) to 458 participants with type 1 diabetes (47% male, aged 44 +/- 9 years, type 1 diabetes duration 29 +/- 9 years) and 546 participants without diabetes (nondiabetic group) (51% male, aged 47 +/- 9 years). Use of antidepressant medication was self-reported. Depression was defined as a BDI-II score >14 and/or use of antidepressant medication. Occurrence of diabetes complications (retinopathy, blindness, neuropathy, diabetes-related amputation, and kidney or pancreas transplantation) was self-reported.

RESULTS

Mean BDI-II score, adjusted for age and sex, was significantly higher in participants with type 1 diabetes than in nondiabetic participants (least-squares mean +/- SE: 7.4 +/- 0.3 vs. 5.0 +/- 0.3; P < 0.0001). Type 1 diabetic participants reported using more antidepressant medications (20.7 vs. 12.1%, P = 0.0003). More type 1 diabetic than nondiabetic participants were classified as depressed by BDI-II cut score (17.5 vs. 5.7%, P < 0.0001) or by either BDI-II cut score or antidepressant use (32.1 vs. 16.0%, P < 0.0001). Participants reporting diabetes complications (n = 209) had higher mean BDI-II scores than those without complications (10.7 +/- 9.3 vs. 6.4 +/- 6.3, P < 0.0001).

CONCLUSIONS

Compared with nondiabetic participants, adults with type 1 diabetes report more symptoms of depression and more antidepressant medication usage. Depression is highly prevalent in type 1 diabetes and requires further study on assessment and treatment.

Polymorphisms of the renin-angiotensin system genes predict progression of subclinical coronary atherosclerosis

Premature coronary artery disease (CAD) in subjects with type 1 diabetes dramatically affects quality of life and morbidity and leads to premature death, but there is still little known about the mechanisms and predictors of this complication. In the present study, we explored the role of genetic variants of angiotensinogen (AGT, M235T), ACE (I/D), and angiotensin type 1 receptor (ATR1, A1166C) as predictors of rapid progression of subclinical coronary atherosclerosis. Five-hundred eighty-five type 1 diabetic patients and 592 similar age and sex control subjects were evaluated for progression of coronary artery calcification (CAC), a marker of subclinical CAD, before and after a 2.5-year follow-up. In logistic regression analysis, CAC progression was dramatically more likely in type 1 diabetic subjects not treated with ACE inhibitor/angiotensin receptor blocker who had the TT-ID-AA/AC genotype combination than in those with other genotypes (odds ratio 11.6 [95%CI 4.5-29.6], P < 0.0001) and was even stronger when adjusted for cardiovascular disease risk factors and the mean A1C (37.5 [3.6-388], P = 0.002). In conclusion, a combination of genotype variants of the renin-angiotensin system genes is a powerful determinant of subclinical progression of coronary artery atherosclerosis in type 1 diabetic patients and may partially explain accelerated CAD in type 1 diabetes.

Evaluating Changes in Coronary Artery Calcium: An Analytic Method That Accounts for Interscan Variability

OBJECTIVE

Coronary calcium measured by electron beam CT is associated with coronary disease and can be used to predict coronary disease events. Studies investigating changes in coronary calcium need to address interscan variability as it relates to the overall coronary calcium score in defining progression or regression of coronary calcium over time. SUBJECTS AND METHODS. Electron beam CT was performed on 1,074 participants. Coronary calcium volume scores were repeated 5 min apart. Interscan variability was examined using Bland-Altman plots and homogeneity tests. Transformations of the Box-Cox family (including power, roots, and logarithm) were applied to calcium volume scores. The transformation that stabilized the variation in calcium volume scores was applied to progression of calcium volume scores in 109 subjects with diabetes.

RESULTS

The variability in calcium volume score increased as the level of coronary calcium increased (rho = 0.67, p < 0.001 for the relation between the absolute difference and the mean value of calcium volume scores). This heterogeneity was removed using the square root transformation of the calcium volume score (rho = 0.09, p < 0.15 for the relation between the absolute difference in the square root of the calcium volume score and the mean square root of the calcium volume score). This transformation was applied to calcium volume scores taken a mean of 2.7 years apart in 109 subjects with diabetes. A significant change in calcium volume score was defined as a difference between the square root-transformed to calcium volume scores greater than or equal to 2.5 mm(3) (> 99th percentile of interscan variability). Significant progression was observed in 10% of the subjects. The square root of the calcium volume score corrected for the bias in progression of calcium volume because of the level of coronary calcium.

CONCLUSION

Using the square root of the calcium volume score stabilized interscan variability across the range of coronary calcium. Defining change in coronary calcium as greater than or equal to 2.5 mm(3) of the difference in the square root-transformed calcium volume scores provided an estimate that was unbiased with respect to baseline coronary calcium. This analytic technique may facilitate investigations of the relevance of changes in coronary calcium to clinical outcomes and the use of changes in coronary calcium as a measure of the therapeutic impact on subclinical disease in clinical trials.

Effect of type 1 diabetes on the gender difference in coronary artery calcification: a role for insulin resistance? The Coronary Artery Calcification in Type 1 Diabetes (CACTI) Study

The objective of this is study was to examine whether estimated insulin resistance and insulin resistance-related factors are associated with coronary artery calcification (CAC) in 1,420 asymptomatic participants in the Coronary Artery Calcification in Type 1 Diabetes (CACTI) study. A total of 656 patients with type 1 diabetes and 764 control subjects aged 20-55 years were examined. CAC was assessed by electron-beam computed tomography. Insulin resistance was computed with linear regression based on an equation previously validated in clamp studies on type 1 diabetic adults. Insulin resistance was associated with CAC (OR 1.6 in type 1 diabetes and 1.4 in control subjects, P < 0.001), independent of coronary artery disease risk factors. There was a male excess of CAC in control subjects (OR 2.7, adjusted for age, smoking, and LDL and HDL cholesterol levels) and in type 1 diabetic patients (OR 2.2, adjusted for the same factors and diabetes duration). After adjusting for insulin resistance, the CAC male excess in diabetic patients decreased from OR 2.2 (P < 0.001) to 1.8 (P = 0.04). After adjustment for waist-to-hip ratio, waist circumference, or visceral fat, the gender difference in CAC was not significant in diabetic subjects. In conclusion, gender differences in insulin resistance-associated fat distribution may explain why type 1 diabetes increases coronary calcification in women relatively more than in men.

Progression of coronary artery calcification in type 1 diabetes: the importance of glycemic control

OBJECTIVE

Coronary artery disease (CAD) occurs earlier in life and is more often fatal in people with type 1 diabetes. This excess risk seems to be higher than in those with type 2 diabetes and is poorly explained by conventional risk factors. The role of glycemic control is controversial and has not been previously addressed in a prospective manner using a reliable marker for subclinical CAD, such as coronary artery calcification (CAC), measured by electron beam computed tomography (EBCT).

RESEARCH DESIGN AND METHODS

We measured CAC twice during an interval of 2.7 years in 109 men and women with type 1 diabetes (aged 22-50 years). Progression of CAC was found in 21 patients, based on change in the square root-transformed volume score.

RESULTS

In multiple logistic regression, CAC progression was associated with baseline hyperglycemia (odds ratio [OR] 7.11, 95% CI 1.38-36.6, P = 0.02), adjusted for the presence of CAC at baseline (P = 0.01), duration of diabetes (P = 0.02), sex (P = 0.09), and age (P = 0.27). There was also a significant interactive effect of higher insulin dose and higher BMI (P = 0.03).

CONCLUSIONS

In conclusion, in this young cohort with type 1 diabetes, suboptimal glycemic control (HbA(1c) >7.5%) was a strong risk factor for progression of CAC. Insulin resistance may also play a role.

Reaction of enzyme-bound 5-deazaflavin with peroxides. Pyrimidine ring contraction via an epoxide intermediate

Reaction of peroxides with 5-deazaflavin bound to glucose oxidase, lactate oxidase, or D-amino acid oxidase results in the formation of 5-deazaflavin 4a, 5-epoxide. The reaction of D-amino acid oxidase with m-chloroperoxybenzoate is an exception since the reagent reacts rapidly with the protein moiety to form m-chlorobenzoate which then binds noncovalently near the unmodified coenzyme. Epoxide bound to glucose oxidase is converted to deazaFAD X X in a reaction similar to that observed previously with oxynitrilase and glycolate oxidase. With lactate oxidase the epoxide is quite stable in the absence of light. With D-amino acid oxidase, denaturation of the protein is accompanied by the release of the epoxide into solution where it decomposes in a manner similar to that observed with model epoxide compounds at neutral pH. Reaction of deazaFAD X X with phosphodiesterase and alkaline phosphatase yields deazariboflavin X X. The same compound has been formed in model studies by exposing 5-deazariboflavin 4a,5-epoxide to alkaline conditions. Structural studies indicate that this reaction involves contraction of the pyrimidine ring to yield 4-ribityl-6,7-dimethyloxazolo[ 4,5-b ]quinolin-2(4H)-one. Model reaction studies are consistent with a mechanism initiated by alkaline hydrolysis of the pyrimidine ring at position 4 followed by two additional steps which proceed at neutral pH. A similar mechanism for the enzyme reactions appears likely since analogous intermediates are detected in the glycolate oxidase and the model reactions. The results suggest that position 4 of the coenzyme in oxynitrilase, glycolate oxidase, and glucose oxidase must be accessible to solvent and that the protein moiety must facilitate the initial hydrolysis of the pyrimidine ring since the enzyme reactions occur at neutral pH. Failure to observe formation of deazaFMN X X with lactate oxidase is attributed, at least in part, to the inaccessibility of the pyrimidine ring to solvent.