The effect of increased lung volume in chronic obstructive pulmonary disease on upper airway obstruction during sleep.

Patients with chronic obstructive pulmonary disease (COPD) exhibit increases in lung volume due to expiratory airflow limitation. Increases in lung volumes may affect upper airway patency and compensatory responses to inspiratory flow limitation (IFL) during sleep. We hypothesized that COPD patients have less collapsible airways inversely proportional to their lung volumes, and that the presence of expiratory airflow limitation limits duty cycle responses to defend ventilation in the presence of IFL. We enrolled 18 COPD patients and 18 controls, matched by age, body mass index, sex, and obstructive sleep apnea disease severity. Sleep studies, including quantitative assessment of airflow at various nasal pressure levels, were conducted to determine upper airway mechanical properties [passive critical closing pressure (Pcrit)] and for quantifying respiratory timing responses to experimentally induced IFL. COPD patients had lower passive Pcrit than their matched controls (COPD: -2.8 ± 0.9 cmH2O; controls: -0.5 ± 0.5 cmH2O, P = 0.03), and there was an inverse relationship of subject's functional residual capacity and passive Pcrit (-1.7 cmH2O/l increase in functional residual capacity, r(2) = 0.27, P = 0.002). In response to IFL, inspiratory duty cycle increased more (P = 0.03) in COPD patients (0.40 to 0.54) than in controls (0.41 to 0.51) and led to a marked reduction in expiratory time from 2.5 to 1.5 s (P < 0.01). COPD patients have a less collapsible airway and a greater, not reduced, compensatory timing response during upper airway obstruction. While these timing responses may reduce hypoventilation, it may also increase the risk for developing dynamic hyperinflation due to a marked reduction in expiratory time.

A multicenter study of preventable contact burns from glass fronted gas fireplaces.

Glass fronted gas fireplaces (GFGFs) have exterior surfaces that can reach extremely high temperatures. Burn injuries from contact with the glass front can be severe with long-term sequelae. The Consumer Product Safety Commission reported that these injuries are uncommon, whereas single-center studies indicate a much higher frequency. The purpose of this multi-institutional study was to determine the magnitude and severity of GFGF injuries in North America. Seventeen burn centers elected to participate in this retrospective chart review. Chart review identified 402 children ≤10 years of age who sustained contact burns from contact with GFGF, who were seen or admitted to the study hospitals from January 2006 to December 2010. Demographic, burn, treatment, and financial data were collected. The mean age of the study group was 16.8 ± 13.3 months. The majority suffered burns to their hands (396, 98.5%), with burns to the face being the second, much less common site (14, 3.5%). Two hundred and sixty-nine required rehabilitation therapy (66.9%). The number of GFGF injuries reported was 20 times greater than the approximately 30 injuries estimated by the Consumer Product Safety Commission's 10-year review. For the affected children, these injuries are painful, often costly and occasionally can lead to long-term sequelae. Given that less than a quarter of burn centers contributed data, the injury numbers reported herein support a need for broader safety guidelines for gas fireplaces in order to have a significant impact on future injuries.

Approach for streamlining measurement of complex physiological phenotypes of upper airway collapsibility.

UNLABELLED: The critical closing pressure (PCRIT), a quantitative assessment of upper airway collapsibility, is derived from pressure flow relationship during sleep. The analytic generation of the pressure flow relationships are non-standardized due to various regression models (linear, spline, median), breath characteristics (flow limited, non-flow limited) or known covariates (sleep stage, body position). We propose a GUI based PCRIT Analysis Software (PAS) to streamline PCRIT analysis and validate its reliability and accuracy compared to current analysis procedures. METHODS: Seventeen subjects underwent a physiology sleep study in which the PCRIT was determined during NREM sleep. Data analysis was performed independently using three paradigms: (1) PAS (Igor Pro; median regression), (2) non-graphic statistics application (SAS; spline regression), and (3) manual spreadsheet calculations (Excel; linear regression). The reliability and accuracy of the PAS was examined through the agreement between each approach using Bland-Altman plots of the mean difference and within-individual variation using intra-class correlation (ICC). RESULTS: There was no difference in the group mean values for PCRIT using the PAS (-1.7 ± 0.7 cm H2O) compared to spline regression (-1.6 ± 0.7 cm H2O; p=0.69) or linear regression (-2.1 ± 0.7 cm H2O; p=0.92). The Bland-Altman analysis did not demonstrate a systematic bias between the PAS and either approach. There was a mean difference of 0.39 ± 0.2 cm H2O between the PAS and linear regression approaches, with upper and lower limits of agreement of 1.81 and -1.02 cm H2O, respectively. The PAS and spline analyses demonstrated an even smaller mean difference of -0.10 ± 0.1cm H2O, with upper and lower limits of 0.90 and -1.08 cm H2O, respectively. CONCLUSION: PAS preserves the reliability and accuracy of the original PCRIT analysis methods while vastly improving their efficiency through graphic user interface and automation of analytic processes. Providing a standardized platform for physiologic data processing offers the ability to implement quality assurance and control procedures for multicenter studies as well as cost saving by improving the efficiency of complex repetitive tasks.

Evaluation of clinical results, histological architecture, and collagen expression following treatment of mature burn scars with a fractional carbon dioxide laser.

OBJECTIVE: To assess mature burn scars treated with a fractional carbon dioxide laser for changes in histological architecture, type I to III collagen ratios, density of elastic tissue, and subjective measures of clinical improvements. DESIGN: Uncontrolled, prospective study of patients with mature burn scars, from a clinical and histological perspective. Biopsy specimens were obtained before and 2 months after 3 treatment sessions. The tissue was prepared with Verhoff von Giesen (VVG) stain to discern elastic tissue and Herovici stain to differentiate types I and III collagen. SETTING: Subjects were recruited from the Grossman Burn Centers. PARTICIPANTS: Of 18 patients with mature burn scars, 10 completed the entire treatment protocol. INTERVENTION: Participants received 3 treatments with a fractional carbon dioxide laser. MAIN OUTCOME MEASURES: Vancouver Scar Scale and Patient and Observer Scar Assessment Scale survey scores. In histological analysis, imaging software was used to measure changes in collagen subtype and elastic tissue. A rating scale was developed to assess normal vs scar architecture. RESULTS: The first hypothesis that significant histological improvement would occur and the second hypothesis of a statistically significant increase in type III collagen expression or a decrease in type I collagen expression were confirmed. There were no significant changes in elastic tissue. Statistically significant improvements were seen in all survey data. CONCLUSIONS: Treatment with a fractional carbon dioxide laser improved the appearance of mature burn scars and resulted in a significant improvement in collagen architecture following treatment. Furthermore, in treated skin specimens, a collagen subtype (types I and III collagen) profile resembling that of nonwounded skin was found.

Clinical and molecular effects on mature burn scars after treatment with a fractional CO(2) laser.

BACKGROUND AND OBJECTIVE: There have been several case reports of improvement in the appearance of mature burn scars following treatment with fractional CO(2) lasers. However, the biochemical mechanisms responsible for these improvements have not been elucidated. MATERIALS AND METHODS: Ten patients with mature, full-thickness, hypertrophic burn scars received initial treatment with a fractional CO(2) laser. Clinical improvement was measured with Vancouver Scar Scale as well as Patient and Observer Scar Assessment Scale. Fresh tissue samples were obtained before the initial treatment and 48 hours after the first treatment for TaqMan Real-time RT-PCR analyses. Expressions of several scar-related biological markers, including types I and III procollagen, matrix metalloproteinase (MMP)-1, -13, transforming growth factor (TGF)-ß1, ß2, ß3, and basic fibroblast growth factor (bFGF), as well as microRNA miR-17-92 cluster, were investigated. RESULTS: There were significant improvements in both observer and subject ratings in all scales. Both types I and III procollagen mRNA levels were dramatically down-regulated after treatment, but the ratio of types I/III procollagen mRNA was not different. The expression of MMP-1 was significantly up-regulated after treatment, while TGF-ß2, -ß3, and bFGF levels were significantly down-regulated. Expression of miR-18a and miR-19a were dramatically up-regulated (P < 0.05) after treatment. CONCLUSIONS: Our study indicated that fractional CO(2) resulted in clinical improvement of mature burn scar. Alteration of types I and III procollagen, MMP-1, TGF-ß2, -ß3, bFGF, as well as miRNAs miR-18a and miR-19a expression may be responsible for the clinical improvement after treatment. Our finding may have implications for novel treatments and further our understanding of fractional CO(2) laser treatment.

The use of acellular dermal matrix in release of burn contracture scars in the hand.

BACKGROUND: Contracture deformities of the upper extremity are encountered frequently in burn victims. Surgical repair of this problem is challenged by a paucity of soft tissue, poor functional outcome, and a high rate of recurrence. Acellular dermal matrix has become increasingly popular in reconstructive surgery--at times--as an alternative to local and free tissue transfer in different parts of the body. However, its applicability in contracture release, particularly in hand surgery, has not been widely explored. METHODS: Nine patients with burn contracture scars involving different locations in the hand and the wrist underwent two-stage reconstruction consisting of contracture release and use of acellular dermal matrix followed by definitive coverage with skin graft at the second stage. Patients were followed up for a period of at least 10 months (range, 10 to 25 months), during which time the passive range of motion of the hand was used as a quantitative measure of surgical outcome. RESULTS: All nine patients retained at least 83 percent of the corrected range of motion involving the affected joints by 1 year and at least 89 percent of correction at each webspace. No patient required a revision procedure. CONCLUSION: Acellular dermal matrix can be an effective tool in surgical treatment of difficult burn contracture deformity in the hand, with lasting results.