Ultralow-Dose Dynamic Expiratory CT and Repeated Imaging Enhance Evaluation for Tracheomalacia.

OBJECTIVE: This study aims to determine if a novel imaging protocol (ultralow-dose dynamic expiratory computed tomography [CT] with repeated imaging) identifies tracheomalacia (TM) more reliably than traditional dynamic tracheal CT. METHODS: We performed a retrospective evaluation of 184 consecutive ultralow-dose dynamic CTs for TM during 2017. The protocol obtains images during 1 inspiration and 2 forced expirations. Tracheal narrowing during both expirations (airway narrowing [percentage] during first dynamic expiration CT [DE1], airway narrowing [percentage] during second dynamic expiration CT [DE2]) was reported as a percentage of inspiratory area. We identified maximum narrowing of each patient's sequence (maximum narrowing [percentage] on either dynamic expiration CT [DEmax] = greatest narrowing of DE1 or DE2) and compared DE1, DE2, and DEmax in individual studies and between patients. Outcomes included frequency of TM, tracheal narrowing, and severity. Reliability was assessed by comparing tracheal area narrowing and TM grade. RESULTS: There was significantly more airway narrowing using 2 expiratory image acquisitions. Average DEmax tracheal area was 12% narrower than DE1 alone and 21% worse than DE2 alone (both P < 0.001). Using DEmax, TM was diagnosed 35% more often than DE1 alone and 31% more often than DE2 alone ( P < 0.001). DEmax identified more severe distribution of TM compared with DE1 or DE2 alone ( P < 0.001). Reliability between DE1 and DE2 was good for tracheal narrowing and moderate for TM grade. The mean effective radiation dose was 2.41 millisievert (mSv) for routine inspiration CT and 0.07 mSv for each dynamic expiration CT (total effective radiation, 2.55 mSv). CONCLUSIONS: Dynamic expiration CT with 2 expiratory image acquisitions enhanced evaluation of TM, minimally increased radiation dose, and should be considered as a noninvasive screening option.

Improvement in postoperative lung function in patients with moderate to severe airway obstruction after robotic-assisted thoracoscopic tracheobronchoplasty.

OBJECTIVE: The study objective was to examine pulmonary function and quality of life improvement after robotic-assisted thoracoscopic tracheobronchoplasty for patients with different degrees of obstructive airway disease. METHODS: We performed a retrospective review of a prospective database of patients who underwent robotic-assisted thoracoscopic tracheobronchoplasty between 2013 and 2020. RESULTS: A total of 118 patients underwent robotic-assisted thoracoscopic tracheobronchoplasty. Preoperative and postoperative pulmonary function tests were available for 108 patients. Postoperative pulmonary function tests at a median of 16 months demonstrated a significant increase in percent predicted forced expiratory volume in 1 second (preoperative median: 76.76% predicted, postoperative: 83% predicted, P = .002). Preoperative and postoperative St George Respiratory Questionnaires were available for 64 patients with a significant decrease in postoperative score at a median of 7 months (preoperative median: 61, postoperative: 41.60, P < .001). When stratified by preoperative degree of obstruction, robotic-assisted thoracoscopic tracheobronchoplasty improved forced expiratory volume in 1 second in moderate to very severe obstruction with a statistically significant improvement in moderate (preoperative median: 63.91% predicted, postoperative median: 73% predicted, P = .001) and severe (preoperative median: 44% predicted, postoperative median: 57% predicted, P = .007) obstruction. St George Respiratory Questionnaire scores improved for all patients. Improvement for mild (preoperative median: 61.27, postoperative median: 36.71, P < .001) and moderate (preoperative median: 57.15, postoperative median: 47.52, P = .03) obstruction was statistically significant. CONCLUSIONS: Robotic-assisted thoracoscopic tracheobronchoplasty improves obstruction and symptoms. With limited follow-up, subgroup analysis showed forced expiratory volume in 1 second improved in severe preoperative obstruction and quality of life improved in moderate obstruction. Future follow-up is required to determine robotic-assisted thoracoscopic tracheobronchoplasty effects on the most severe group, but we cannot conclude that increased degree of preoperative obstruction precludes surgery.

Robotic-assisted tracheobronchoplasty: Quality of life and pulmonary function assessment on intermediate follow-up.

OBJECTIVE: The initial description of robotic tracheobronchoplasty for the treatment of tracheobronchomalacia demonstrated feasibility, safety, and short-term symptomatic and functional improvement. The purpose of the current study was to demonstrate intermediate outcomes in postoperative pulmonary function and quality of life after robotic tracheobronchoplasty. METHODS: We retrospectively reviewed prospectively collected clinical data from 42 patients who underwent robotic tracheobronchoplasty from May 2016 to December 2017. The Institutional Review Board or equivalent ethics committee of the Northwell Health approved the study protocol and publication of data. Patient written consent for the publication of the study data was waived by the Institutional Review Board. RESULTS: A total of 42 patients underwent robotic tracheobronchoplasty during the study period. Median total follow-up is 40 months. There was 1 death since surgery from an unrelated disease. Significant decreases in St George's Respiratory Questionnaire total score (preoperative mean: 64.01, postoperative mean: 38.91, P = .002), St George's Respiratory Questionnaire symptom score (preoperative median: 82.6, postoperative median: 43.99, P < .001), and St George's Respiratory Questionnaire impact score (preoperative median: 55.78, postoperative median: 25.95, P < .001) were apparent at a median follow-up of 13 months. Comparison of preoperative and postoperative pulmonary function tests revealed a significant increase in percent predicted forced expiratory volume in 1 second (preoperative median: 74% vs postoperative median: 82%, P = .001), forced vital capacity (preoperative median: 68.5% vs postoperative median: 80.63%, P < .001), and peak expiratory flow (preoperative median: 61.5% vs postoperative median: 75%, P = .02) measured at a median follow-up of 29 months. CONCLUSIONS: Robotic tracheobronchoplasty is associated with low intermediate-term mortality. Robotic tracheobronchoplasty results in significant improvement in quality of life and postoperative pulmonary function. Longer-term follow-up is necessary to continue to elucidate the effect of robotic tracheobronchoplasty on halting pathologic progression of tracheobronchomalacia and to determine the long-term impact of tracheobronchoplasty on symptomatic and functional improvement.

First series of minimally invasive, robot-assisted tracheobronchoplasty with mesh for severe tracheobronchomalacia.

OBJECTIVE: Tracheobronchomalacia is a progressive, debilitating disease with limited treatment options. Open tracheobronchoplasty (TBP) is an accepted surgical option for management of severe tracheobronchomalacia. This study examined the outcomes of the first reported series of robot-assisted TBP (R-TBP). METHODS: We retrospectively reviewed the records of patients with clinical suspicion for tracheobronchomalacia who had dynamic computed tomography scan and subsequent R-TBP from May 2016 to December 2017. RESULTS: Four hundred thirty-five patients underwent dynamic computed tomography scan for suspicion of tracheobronchomalacia. Of this group, 42 patients underwent R-TBP. In the surgery group, the median age was 66 years (interquartile range, 39-72 years) and there were 30 women (71%). Respiratory comorbidities included asthma (88%) and chronic obstructive pulmonary disease (52%). The median operative time was 249 minutes (interquartile range, 266-277 minutes). Median hospital length of stay was 3 days (interquartile range, 2-4.75 days), and there were 19 postoperative complications (11 minor and 8 major). There were no mortalities at 90 days. Comparison of preoperative and postoperative pulmonary function testing demonstrated improvement in forced expiratory volume at 1 second by 13.5% (P = .01), forced vital capacity by 14.5% (P < .0001), and peak expiratory flow rate by 21.0% (P < .0001). Quality of life questionnaires also showed improvement with 82% reporting overall satisfaction with the procedure. CONCLUSIONS: R-TBP can be performed with low morbidity and mortality. Early follow-up reveals significant improvement in pulmonary function testing and high patient satisfaction when compared with preoperative baseline. Long-term follow-up is needed to demonstrate the durability of R-TBP and substantiate its role in the management of patients with symptomatic, severe tracheobronchomalacia.

Ultralow Dose Dynamic Expiratory Computed Tomography for Evaluation of Tracheomalacia.

OBJECTIVE: The aim of this study was to determine the average effective radiation dose and feasibility of ultralow dose dynamic expiratory computed tomography (CT) for evaluation of tracheomalacia (ULD) and to evaluate factors that impact image quality. METHODS: This is a retrospective study of 64 consecutive patients from September to October 2016 for the evaluation of tracheomalacia. All studies were performed with routine inspiration chest CT followed by ULD z(kilovoltage peak (kVp) 80, 100, or 120 and fixed milliamperage 10) or typical dose CT (TD) (kVp 100 or 120 with automated milliamperage) dynamic expiration CT. Image quality was considered diagnostic if the trachea area could be accurately measured for tracheomalacia assessment, and diagnostic studies were graded fair, good, or excellent. Scan length, image quality, and effective radiation dose were compared for ULD versus TD and ULD at 100 kVp versus ULD at 80 kVp. For ULD studies, patient factors were compared across image quality. RESULTS: The ULD had a mean effective radiation dose of 0.08 mSv, with all studies of diagnostic image quality. The ULD showed 95% reduction in effective radiation dose (P < 0.001), 14% significant reduction in scan length (P = 0.029), and qualitatively decreased image quality compared w2 ith TD (P < 0.001). The ULD at 100 kVp had significantly better image quality compared with ULD at 80 kVp (P = 0.041) with higher effective radiation dose (0.09 vs 0.05 mSv) (P < 0.001). Body mass index significantly impacted image quality for all ULD studies but not for ULD at 80 or 100 kVp. CONCLUSION: For evaluation of tracheomalacia, ULD showed low effective radiation dose less than 0.1 mSv and maintained diagnostic image quality.

The sustainability of VO2max: effect of decreasing the workload.

The study examined the maintenance of VO(2max) using VO(2max) as the controlling variable instead of power. Therefore, ten subjects performed three exhaustive cycling exercise bouts: (1) an incremental test to determine VO(2max) and the minimal power at VO(2max) (PVO(max)), (2) a constant-power test at PVO(max) and (3) a variable-power test (VPT) during which power was varied to control VO(2) at VO(2max). Stroke volume (SV) was measured by impedance in each test and the stroke volume reserve was calculated as the difference between the maximal and the average 5-s SV. Average power during VPT was significantly lower than PVO(max) (238 ± 79 vs. 305 ± 86 W; p < 0.0001). All subjects, regardless of their VO(2max) values and/or their ability to achieve a VO(2max) plateau during incremental test, were able to sustain VO(2max) for a significantly longer time during VPT compared to constant-power test (CPT) (958 ± 368 s vs. 136 ± 81 s; p < 0.0001). Time to exhaustion at VO(2max) during VPT was correlated with the power drop in the first quarter of the time to exhaustion at VO(2max) (r = 0.71; p < 0.02) and with the stroke volume reserve (r = 0.70, p = 0.02) but was not correlated with VO(2max). This protocol, using VO(2max) rather than power as the controlling variable, demonstrates that the maintenance of exercise at VO(2max) can exceed 15 min independent of the VO(2max) value, suggesting that the ability to sustain exercise at VO(2max) has different limiting factors than those related to the VO(2max) value.

Two-axis solar tracking accomplished through small lateral translations.

High-concentration solar-power optics require precise two-axis tracking. The planar micro-optic solar concentrator uses a lenslet array over a planar waveguide with small reflective facets at the focal point of each lenslet to couple incident light into the waveguide. The concentrator can use conventional tracking, tilting the entire assembly, but the system geometry also allows tracking by small lateral translation of the lenslet relative to the waveguide. Here, we experimentally demonstrate such microtracking with the existing concentrator optics and present optimized optical designs for systems with higher efficiency and angle range.

Reactive self-tracking solar concentrators: concept, design, and initial materials characterization.

Étendue limits angular acceptance of high-concentration photovoltaic systems and imposes precise two-axis mechanical tracking. We show how a planar micro-optic solar concentrator incorporating a waveguide cladding with a nonlinear optical response to sunlight can reduce mechanical tracking requirements. Optical system designs quantify the required response: a large, slow, and localized increase in index of refraction. We describe one candidate materials system: a suspension of high-index particles in a low-index fluid combined with a localized space-charge field to increase particle density and average index. Preliminary experiments demonstrate an index change of aqueous polystyrene nanoparticles in response to a low voltage signal and imply larger responses with optimized nanofluidic materials.

Group training in adolescent runners: influence on VO2max and 5-km race performance.

The aims of this study were to (a) examine the interrelationships between training intensity, VO2max, and race performance in adolescent crosscountry runners and (b) determine if adolescent runners participating in a group crosscountry training program differ in the amount of training time at various intensities. In this study, 7 adolescent runners performed a laboratory-based VO2max test before and after a 9-week high-school crosscountry season. Heart rate (HR) and ventilatory threshold (VT) were used to identify 3 training zones for each runner based on the HR at ventilator threshold (HR(VT)): zone 1: >15 b·min(-1) below HR(VT); zone 2: between zone 1 and HR(VT); zone 3: >HR(VT). During each training session throughout the season, HR was measured to quantify the amount of training time in each of these 3 intensity zones. Results showed that the time in each of the 3 zones was not significantly associated with 5-km race performance. Zone 3 training time was positively associated with postseason VO2max (r = 0.73, p = 0.06); VO2max was significantly inversely associated with 5-km race performance (r = -0.77, p = 0.04). Each week, the amount of training time at, above, and below the VT was significantly different among the participants even though the training prescription for the group was standardized. The results suggest that, among adolescent crosscountry runners, training above the VT may be important in increasing VO2max and ultimately, race performance. Given the between-participant differences in the amount of training time in each HR zone, coaches should apply individual, rather than group, training programs.

Orthogonal and secondary concentration in planar micro-optic solar collectors.

Planar micro-optic concentrators are passive optical structures which combine a lens array with faceted microstructures to couple sunlight into a planar slab waveguide. Guided rays propagate within the slab to edge-mounted photovoltaic cells. This paper provides analysis and preliminary experiments describing modifications and additions to the geometry which increase concentration ratios along both the vertical and orthogonal waveguide axes. We present simulated results for a 900x concentrator with 85% optical efficiency, measured results for small-scale experimental systems and briefly discuss implementations using low-cost fabrication on continuous planar waveguides.

Planar micro-optic solar concentrator.

We present a new approach to solar concentration where sunlight collected by each lens in a two-dimensional lens array is coupled into a shared, planar waveguide using localized features placed at each lens focus. This geometry yields a thin, flat profile for moderate concentration systems which may be fabricated by low-cost roll manufacture. We provide analyses of tradeoffs and show optimized designs can achieve 90% and 82% optical efficiency at 73x and 300x concentration, respectively. Finally, we present preliminary experimental results of a concentrator using self-aligned reflective coupling features fabricated by exposing molded SU-8 features through the lens array.

Anatomy-driven design of a prototype video laryngoscope for extremely low birth weight infants.

Extremely low birth weight (ELBW) infants frequently require endotracheal intubation for assisted ventilation or as a route for administration of drugs or exogenous surfactant. In adults and less premature infants, the risks of this intubation can be greatly reduced using video laryngoscopy, but current products are too large and incorrectly shaped to visualize an ELBW infant's airway anatomy. We design and prototype a video laryngoscope using a miniature camera set in a curved acrylic blade with a 3×6-mm cross section at the tip. The blade provides a mechanical structure for stabilizing the tongue and acts as a light guide for an LED light source, located remotely to avoid excessive local heating at the tip. The prototype is tested on an infant manikin and found to provide sufficient image quality and mechanical properties to facilitate intubation. Finally, we show a design for a neonate laryngoscope incorporating a wafer-level microcamera that further reduces the tip cross section and offers the potential for low cost manufacture.

Mountaineering experience decreases the net oxygen cost of climbing Mont Blanc (4,808 m).

The purpose of this study was to test the hypothesis that mountaineering experience decreases the net oxygen cost of uphill walking (OCw) on steep mountain trails and in ice and snow conditions. OCw was measured during an ascent of Mont Blanc in eight experienced alpinists and eight non-alpinists who were matched for sex (4 + 4) and low-altitude aerobic power (V(O)(2)(max) 50-55 ml kg(-1) min(-1)). Subjects carried a breath-by-breath gas exchange analyzer and a GPS. V(O)(2)(max) at altitude was estimated from measured low-altitude V(O)(2)(max) using Bassett's equation to calculate fractional use of V(O)(2)(max) during the ascent (FV(O)(2)(max)). OCw was calculated as the difference between V(O)(2) while climbing minus resting V(O)(2). At all elevations, Alpinists exhibited a lower OCw (P < 0.01). In all subjects, OCw increased when encountering ice and snow conditions. FV(O)(2)(max) remained stable around 75% at all elevations independent of experience or sex. In conclusion, the OCw is lower in experienced mountaineers compared to non-experienced subjects, and increases when going from steep rocky mountain terrain to ice and snow conditions, independent of mountaineering experience or sex.

Ultrathin four-reflection imager.

We present the design and experimental demonstration of an ultrathin four-reflection imager. The F/1.15 prototype imager achieves a focal length of 18.6 mm in a track length of just 5.5 mm, providing a 17 degrees field of view over 1.92 megapixels of a color image sensor with 3 microm pixels. We also present the design and experimental results of pupil-phase encoding and postprocessing, which were applied to extend the depth of field and compensate a small amount of axial chromatic aberration present in the four-reflection imager prototype.

Integrated diffractive shearing interferometry for adaptive wavefront sensing.

We present theory, design, and preliminary experimental studies for a compact wavefront sensor based on lateral shearing interferometry using a binary phase grating, image sensor, and Fourier-based processing. The integrated system places a diffractive element directly onto an image sensor to generate interference fringes within overlapping diffraction orders. The shearing ratio and the interferogram signal-to-noise ratio directly affect the reconstruction accuracy of wavefronts with differing spatial variations. Optimal shearing parameters associated with the autocorrelation of the input encourage placing a spatial light modulator as the diffractive element allowing adaptive wavefront sensing. Experimental results from a fixed-grating system are presented as well as requirements for next-generation adaptive systems.

Training characteristics of qualifiers for the U.S. Olympic Marathon Trials.

PURPOSE: To describe and compare training characteristics of the 2004 U.S. Olympic Marathon Trials qualifiers. METHODS: All qualifiers (104 men, 151 women) received questionnaires. Ninety-three (37 men, 56 women) responded and were categorized as elite (men <2 hours 15 min, women <2 hours 40 min) or national class. RESULTS: Men and women ran 75% and 68% of their weekly training distance, respectively, below marathon race pace. Men trained longer than women (12.2 +/- 5.3 vs 8.8 +/- 5.6 years), ran more often (8.7 +/- 2.8 vs 7.1 +/- 2.5 times/wk), and ran farther (145.3 +/- 25.6 vs 116.0 +/- 26.5 km/wk). Elite women ran more than national-class women (135.8 +/- 31.5 vs 111.3 +/- 23.3 km/wk). Distances run at specific intensities were similar between sexes. For men and women, respectively, 49% and 31% did not have a coach and 65% and 68% trained alone. Marathon performance correlated to 5-km, 10-km, and half-marathon performance and to years training, average and peak weekly distance, number of weekly runs, and number of runs > or = 32 km for women. CONCLUSIONS: Among U.S. Olympic Marathon Trials qualifiers, there is no consensus as to how to prepare for the marathon beyond running at a pace slower than race pace. Weekly training distance seems to influence women's marathon performance more than it does men's. Because many of these athletes train alone and without a coach, further research is warranted on the reasons that these athletes train the way they do.

Chocolate milk as a post-exercise recovery aid.

Nine male, endurance-trained cyclists performed an interval workout followed by 4 h of recovery, and a subsequent endurance trial to exhaustion at 70% VO2max, on three separate days. Immediately following the first exercise bout and 2 h of recovery, subjects drank isovolumic amounts of chocolate milk, fluid replacement drink (FR), or carbohydrate replacement drink (CR), in a single-blind, randomized design. Carbohydrate content was equivalent for chocolate milk and CR. Time to exhaustion (TTE), average heart rate (HR), rating of perceived exertion (RPE), and total work (WT) for the endurance exercise were compared between trials. TTE and WT were significantly greater for chocolate milk and FR trials compared to CR trial. The results of this study suggest that chocolate milk is an effective recovery aid between two exhausting exercise bouts.