The effects of high-frequency chest compression on end-tidal CO2.

INTRODUCTION: High-frequency chest compression (HFCC) is used for airway clearance, but may have other effects. We sought to determine if HFCC provides augmented ventilation. METHODS: During treatment, capnometry was measured with the HFCC vest set to 6-20 Hz. End-tidal CO2 (etCO2 ) was compared using generalized estimating equations. RESULTS: Twenty-four measurements were obtained from 15 subjects with mean age 15.2 ± 2.5 years and forced expiratory volume in one second (FEV1 ) % predicted 70 ± 23. EtCO2 decreased with HFCC at 6 Hz when compared with baseline (P < .001), with small changes with increasing oscillation frequency. Change in etCO2 was not predicted by FEV1 , body mass index, age, or sex. CONCLUSIONS: While HFCC has been shown to be a suitable method of airway clearance, investigators have failed to demonstrate differences between techniques. Assessment of these methodologies will become important as new airway clearance devices are proposed. Other outcome measures (besides FEV1 ) may be needed to assess effects of airway clearance, and we propose that physiologic measures might be one such measure which deserves further exploration.

Glycemic control and FEV1 recovery during pulmonary exacerbations in pediatric cystic fibrosis-related diabetes.

RATIONALE: Whether short-term glucose control in cystic fibrosis-related diabetes (CFRD) is associated with FEV1 recovery during acute pulmonary exacerbations is unclear. METHODS: Data from all patients with CFRD ages 6-21 years hospitalized in 2010-2016 for pulmonary exacerbations at our CF Center were analyzed, including CFRD status at each encounter, all FEV1 recorded during each exacerbation, and relevant clinical covariates. Glucose control was analyzed using meter blood glucose area under the curve (AUC) indices. The primary outcome was FEV1 recovery. RESULTS: Patients with CFRD who finished IV antibiotics at home were treated for longer than those fully treated in the hospital (22.2 vs. 13.8 days). In those who finished treatment at home, poor inpatient glycemic control was associated with lower lung function improvement: when comparing the 75th to the 25th percentile of each glycemic index (i.e., "poorer" vs. "better" glycemic control), FEV1 recovery at discharge was 20.1% lower for glucose AUC (95%CI -0.4%, -39.9%); 20.9% lower for 48-h AUC (95%CI -2.7%, -39.1%); and 28.2% lower for AUC/day (95%CI -7.1%, -49.3%). Similar results were found at the end of IV antibiotics and at clinic follow-up. Likewise, patients with poor glycemic control had a lower slope of inpatient FEV1 recovery. Analysis in patients with normal glucose tolerance was largely non-significant. No associations were found between hemoglobin A1c and FEV1 recovery. CONCLUSIONS: In patients with CFRD who complete IV antibiotic treatment at home, poor inpatient glycemic control is associated with worse FEV1 recovery despite longer duration of treatment.

Subjective and Objective Assessments of Flow-Volume Curve Configuration in Children and Young Adults.

RATIONALE: Analysis of maximal expiratory flow-volume curves (MEFVCs) allows for determination of airway obstruction, but quantitative methods to describe these curves are not commonly used. OBJECTIVES: We sought to determine the variability in MEFVC concavity assessment by pulmonary physicians, whether objective indices of concavity can be substituted for subjective expert impression, and whether MEFVC concavity correlates with clinical outcomes. METHODS: A survey of 37 MEFVCs (plus 3 duplicates) was sent to pulmonologists for quantitative assessment of MEFVC concavity. Objective indices (ß-angle, ratio forced expiratory flow at 50% of total lung volume to peak expiratory flow rate [FEF50/PEFR], ratio of maximum mid-expiratory flow to FVC [MMEF/FVC], kmax, and averaged flow-volume second derivatives) were calculated for each MEFVC and were correlated with the mean expert score. Both the mean expert scores and the best-performing index were then correlated with hospitalizations. MEASUREMENTS AND MAIN RESULTS: Ninety-two respondents provided usable data. There was substantial variability in concavity scores between subjects, but strong intrasubject reliability. Mean expert score did not differ by physician years of experience. Several indices (ß-angle, FEF50/PEFR, FEV1/FVC, MMEF/FVC, FEF50, and forced expiratory flow between 25 and 75% of total lung volume) correlated strongly with mean expert scores. A new variable (ß-MMEF) was constructed using coefficients from stepwise linear regression and accurately predicted the mean expert score (R(2) = 0.96). Mean expert score and ß-MMEF showed similar odds ratios for hospitalization (2.13 and 2.32, respectively) with identical positive (∼71%) and negative (87%) predictive values. The ß-MMEF was also associated with hospitalizations in two independent cohorts of children with asthma and cystic fibrosis. CONCLUSIONS: The ß-MMEF is an objective measure of maximal expiratory flow-volume curve concavity and highly correlates with expert impression. Both the mean expert score for expiratory curve concavity and the ß-MMEF were associated with increased risk of subsequent hospitalization. The ß-MMEF may be a useful biomarker for disease severity in asthma and cystic fibrosis.

Effects of load and indicator type upon occlusal contact markings.

STATEMENT OF PROBLEM: Clinicians use occlusal indicators to identify tooth contacts. However, the reliability of these indicators has been questioned. At times occlusal contacts are not identified or false positive occlusal contacts are observed. PURPOSE OF STUDY: This study was designed to compare the number and size of occlusal indicator marks from both thick and thin occlusal indicator materials with different loads. MATERIALS AND METHODS: Ivorine casts were articulated and mounted on an Hana Mate nonadjustable articulator. Loads of 100N, 150N, and 200N were applied with Accufim (25 microm thick, Parkell, Farmingdale, NY) and Articulating Paper (60 microm thick, G.E. Rudischauer Dental Articulating Paper, Brooklyn, NY) as the occlusal indicators. A fresh piece of indicator was used for each trial. Comparisons were made of the number and size of the contacts for both the thick and thin occlusal indicators at the different loads. RESULTS: Observation of the marks recorded with the thicker occlusal indicator demonstrated both a greater number marks and a larger size to the marks when compared to the thinner Accufilm, p < or = 0.02-0.0001. However, there was no significant increase in the number or size of the marks with an increased load for either material.

Long-term effects of storage and thermal cycling on the marginal adaptation of provisional resin crowns: a pilot study.

STATEMENT OF PROBLEM: Provisional resin crowns may be used for an extended period while complex treatments are completed. The crowns function intraorally; therefore, moisture absorption and thermal cycling may affect the physical properties of acrylic resin, causing a change in marginal gap size. PURPOSE: The purpose of this pilot study was to examine the effect of long-term water absorption and thermal cycling on marginal gap size of polymethyl methacrylate copolymer and bis-acrylic composite resin crowns. MATERIAL AND METHODS: Specimens (n = 10) were fabricated from 2 acrylic resins: a polymethyl methacrylate (Alike) and a bis-acrylic composite resin (Provitec). Specimens were first fabricated on a metal master die. Custom die stems were fabricated for each specimen from a low-fusing alloy (Cerroblend) to eliminate the factor of polymerization shrinkage. Specimens were then fitted to assure a standardized, pre-experimental marginal gap range of < or = 25 microm. Specimens were stored in a humidor at 37 degrees C and 97% relative humidity for 1 year and subsequently thermal cycled (5 degrees C to 60 degrees C, 6-second dwell time, for 8000 cycles). Measurements in micrometers of the marginal gap were recorded using a microscope equipped with a digital video camera and image analysis software before and after treatment. A 2-way analysis of variance with a split design was performed for factors of materials and treatment (alpha = .05). RESULTS: For the factor of material, there was no significant difference; however, there was a significant difference between treatments, with a significantly greater increase in marginal gap size after thermal cycling (P < .002). CONCLUSION: Provisional crowns made from either a bis-acrylic resin composite or a polymethyl methacrylate copolymer demonstrated loss of marginal adaptation during a simulated long-term period of service.