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Funding Acknowledgements Type of funding sources: None. Background Current guidelines advocate for a multi-parametric approach to echocardiographic quantitation of tricuspid regurgitation (TR). The primary quantitative measure of TR severity uses the proximal isovelocity surface area (PISA) method to calculate effective regurgitant orifice area (EROA) and regurgitant volume (RegVol). However, EROA-PISA may underestimate TR severity due to low flow and tethering of the tricuspid leaflets. Purpose The purpose of this study was to compare standard EROA-PISA quantitation of TR to alternative quantitative measures, including quantitative Doppler (EROA-Doppler), flow- and angle-corrected PISA method (EROA-Corrected), and three-dimensional vena contracta area (3D-VCA), in addition to the comparison of calculated RegVol-PISA, RegVol-Doppler, and RegVol-3DVCA. Methods Patients undergoing both transthoracic (TTE) and transesophageal (TEE) echocardiographic evaluation of TR severity for transcatheter treatment were included in this study. Patients were excluded if they had ≥ moderate aortic regurgitation. TTE measurements of EROA-PISA and RegVol-PISA were performed as per American Society of Echocardiography guidelines. EROA-Doppler was performed by quantifying RegVol-Doppler (diastolic stroke volume using biplane annular area, minus left ventricular outflow stroke volume) and deriving EROA. EROA-Corrected was calculated by adjusting for both aliasing velocity and leaflet angle as per published methods. 3D-VCA was measured on TEE performed within 14 days of TTE. Results Of 44 consecutive patients, the median age was 80 ± 9 years, 61% were female, and 89% had atrial fibrillation. Most patients (86%) had functional TR, 71% had a EROA-PISA ≥ 0.4 cm2. Table 1 shows the EROA and RegVol results for each method. EROA-PISA and RegVol-PISA were significantly lower than EROA-Doppler and RegVol-Doppler, as well as 3D-VCA and RegVol-3DVCA (all p < 0.0001). There was no significant difference between EROA-Doppler and 3D-VCA (p = 0.51), and RegVol-Doppler and RegVol-3DVCA (p = 0.66). EROA-Corrected reduced the absolute difference with EROA-Doppler (51% to 33%, p < 0.0001) and 3D-VCA (52% to 32%, p < 0.0001), but remained statistically lower than EROA-Doppler and 3D-VCA. Although EROA-PISA was strongly correlated to EROA-Doppler (r = 0.75, p < 0.0001) and 3D-VCA (r = 0.68, p < 0.0001), the correlation between EROA-Doppler and 3D-VCA was greatest (r = 0.77, p < 0.0001). Adjusting EROA-PISA for angle and flow demonstrated improved correlation to EROA-Doppler without affecting correlation to 3D-VCA (Figure 1). Conclusion Our study demonstrated that EROA-PISA significantly underestimates the severity of TR by EROA-Doppler and 3D-VCA. Although PISA correction methods reduced the underestimation, both EROA-Corrected and RegVol-Corrected remained significantly lower. EROA-Doppler and 3D-VCA and the calculated RegVol by each method, were closely correlated and not significantly different. Abstract Table 1 Abstract Figure 1

Funding Acknowledgements Type of funding sources: None. Background The proximal isovelocity surface area (PISA) method to quantify tricuspid regurgitation (TR) severity relies on the geometric assumption of a circular, planar regurgitant orifice. However, the TR orifice is often non-circular resulting in underestimation of TR severity when calculating the effective regurgitant orifice area (EROA) and regurgitant volume (RegVol). Purpose To evaluate the effect of ellipticity of the tricuspid annulus on EROA-PISA correlation with quantitative Doppler (EROA-Dopp), and three-dimensional vena contracta area (VCA-3D). Methods Patients undergoing both transthoracic (TTE) and transesophageal (TEE) echo evaluation of TR severity were included in this study. Regurgitant orifice ellipticity was calculated as the ratio of the vena contracta maximum and minimum widths (VC-Ratio). Quantification of EROA and RegVol were performed on TTE for EROA-PISA and EROA-Dopp. Vena contract area was measured on TEE (VCA-3D). Results Of 44 total pts, the median age was 80 ± 9, 61% were female, 89% had atrial fibrillation, (86%) had functional TR, 32% were graded as severe, and 71% had a EROA-PISA ≥ 0.4 cm2. Median VC-Ratio was 1.3 (IQR 1.1-1.8) and was used to differentiate more circular orifices (VC-Ratio 0.5 for all). EROA-PISA correlated better with both EROA-Dopp and VCA-3D in circular compared to elliptical orifices (Table). EROA-Dopp and VCA-3D demonstrated high correlation for both circular and elliptical orifices (r = 0.76, p < 0.0001 and r = 0.77, p < 0.0001 respectively). Conclusion Our study demonstrated that there is a significant difference in quantitative measurements of tricuspid regurgitant orifice area, with EROA-PISA significantly underestimating both EROA-Dopp and VCA-3D. In more circular orifices, the EROA-PISA correlation was higher, however EROA-Dopp and VCA-3D were still significantly larger. Whether EROA-Dopp and VCA-3D are more predictive of outcomes requires further study. Abstract Table 1 Abstract Figure 1

While it is reasonable to predict that photosynthetic rates are inhibited while leaves are wet, leaf gas exchange measurements during wet conditions are challenging to obtain due to equipment limitations and the complexity of canopy-atmosphere interactions in forested environments. Thus, the objective of this study was to evaluate responses of seven tropical and three semiarid savanna plant species to simulated leaf wetness and test the hypotheses that (i) leaf wetness reduces photosynthetic rates (Anet), (ii) leaf traits explain different responses among species and (iii) leaves from wet environments are better adapted for wet leaf conditions than those from drier environments. The two sites were a tropical rainforest in northern Costa Rica with ~4200 mm annual rainfall and a savanna in central Texas with ~1100 mm. Gas exchange measurements were collected under dry and wet conditions on five sun-exposed leaf replicates from each species. Additional measurements included leaf wetness duration and stomatal density. We found that Anet responses varied greatly among species, but all plants maintained a baseline of activity under wet leaf conditions, suggesting that abaxial leaf Anet was a significant percentage of total leaf Anet for amphistomatous species. Among tropical species, Anet responses immediately after wetting ranged from -31% (Senna alata (L.) Roxb.) to +21% (Zamia skinneri Warsz. Ex. A. Dietr.), while all savanna species declined (up to -48%). After 10 min of drying, most species recovered Anet towards the observed status prior to wetting or surpassed it, with the exception of Quercus stellata Wangenh., a savanna species, which remained 13% below Anet dry. The combination of leaf wetness duration and leaf traits, such as stomatal density, trichomes or wax, most likely influenced Anet responses positively or negatively. There was also overlap between leaf traits and Anet responses of savanna and tropical plants. It is possible that these species converge on a relatively conservative response to wetness, each for divergent purposes (cooling, avoiding stomatal occlusion, or by several unique means of rapid drying). A better understanding of leaf wetness inhibiting photosynthesis is vital for accurate modeling of growth in forested environments; however, species adapted for wet environments may possess compensatory traits that mitigate these effects.

The Volume Diffusive Respirator® (VDR) is a high-frequency time cycled pressure ventilator that can ventilate, oxygenate, and promote secretion removal. The VDR provides ventilation at lower airway pressures than those required for conventional ventilation in the pressure control mode (PCV). A prospective, randomized, institutional review board–approved study was conducted comparing the VDR to PCV in burned children with respiratory failure from all causes. Methods: Pediatric burn patients requiring ventilation were stratified by presence of inhalation injury and ventilated by VDR or PCV to achieve predefined arterial blood gases. Results: Sixty-four patients were prospectively assigned ventilator type; 32 to VDR, 32 to PCV. Data are reported as mean + SEM. Patient age was 7.4 + 0.7 years, TBSA was 56 + 3%, and number of patients with inhalation injuries was 55 (86%). Maximum peak inspiratory pressure with the VDR was significantly less than with PCV (30.9 + 0.8 cm H2O vs 39.5 + 1.8 cm H2O, P < 0.05) and the best PaO2/FIO2 ratio was significantly higher with the VDR compared with PCV (563 + 15 vs 507 + 13, P < 0.05). No patient in the VDR group had evidence of barotrauma compared with two in the PCV group. Five patients in the PCV group died compared with two in the VDR group. Conclusion: Patients ventilated with the VDR required significantly lower peak inspiratory pressure and achieved a significantly higher PaO2/FIO2 ratio compared with PCV. This demonstrates the VDR is a safe and effective method of ventilation for pediatric burn patients and it offers advantages when compared with conventional ventilation.