Search

Heart failure with preserved ejection fraction (HFpEF) is associated with cardiopulmonary abnormalities that may increase physiological dead space to tidal volume (VD/VT) during exercise. However, studies have not corrected VD/VT for apparatus mechanical dead space (VDM), which may confound the accurate calculation of VD/VT. We evaluated whether calculating physiological dead space with (VD/VT(VDM)) and without (VD/VT) correcting for VDM impacts the interpretation of gas exchange efficiency during exercise in HFpEF. Fifteen HFpEF (age: 69 ± 6 yr; V̇o(2peak): 1.34 ± 0.45 L/min) and 12 controls (70 ± 3 yr; V̇o(2peak): 1.70 ± 0.51 L/min) were studied. Pulmonary gas exchange and arterial blood gases were analyzed at rest, submaximal (20 W for HFpEF and 40 W for controls), and peak exercise. VD/VT was calculated as [Formula: see text] – [Formula: see text] / [Formula: see text]. VD/VT(VDM) was calculated as [Formula: see text] – [Formula: see text] / [Formula: see text] – VDM/VT. VD/VT decreased from rest (HFpEF: 0.54 ± 0.07; controls: 0.32 ± 0.07) to submaximal exercise (HFpEF: 0.46 ± 0.07; controls: 0.25 ± 0.06) in both groups (P < 0.05), but remained stable (P > 0.05) thereafter to peak exercise (HFpEF: 0.46 ± 0.09; controls: 0.22 ± 0.05). In HFpEF, VD/VT(VDM) did not change (P = 0.58) from rest (0.29 ± 0.07) to submaximal exercise (0.29 ± 0.06), but increased (P = 0.02) thereafter to peak exercise (0.33 ± 0.06). In controls, VD/VT(VDM) remained stable such that no change was observed (P > 0.05) from rest (0.17 ± 0.06) to submaximal exercise (0.14 ± 0.06), or thereafter to peak exercise (0.14 ± 0.05). Calculating physiological dead space with and without a VDM correction yields quantitively and qualitatively different results, which could have impact on the interpretation of gas exchange efficiency in HFpEF. Further investigation is required to uncover the clinical consequences and the mechanism(s) explaining the increase in VD/VT(VDM) during exercise in HFpEF. NEW & NOTEWORTHY Calculating VD/VT with and without correcting for VDM yields quantitively and qualitatively different results, which could have an important impact on the interpretation of V/Q mismatch in HFpEF. The finding that V/Q mismatch and gas exchange efficiency worsened, as reflected by an increase in VD/VT(VDM) during exercise, has not been previously demonstrated in HFpEF. Thus, further studies are needed to investigate the mechanisms explaining the increase in VD/VT(VDM) during exercise in patients with HFpEF.

Background: Exercise intolerance is a defining characteristic of heart failure with preserved ejection fraction (HFpEF). A marked rise in pulmonary capillary wedge pressure (PCWP) during exertion is pathognomonic for HFpEF and is thought to be a key cause of exercise intolerance. If true, acutely lowering PCWP should improve exercise capacity. To test this hypothesis, we evaluated peak exercise capacity with and without nitroglycerin to acutely lower PCWP during exercise in patients with HFpEF. Methods: Thirty patients with HFpEF (70±6 years of age; 63% female) underwent 2 bouts of upright, seated cycle exercise dosed with sublingual nitroglycerin or placebo control every 15 minutes in a single-blind, randomized, crossover design. PCWP (right heart catheterization), oxygen uptake (breath × breath gas exchange), and cardiac output (direct Fick) were assessed at rest, 20 Watts (W), and peak exercise during both placebo and nitroglycerin conditions. Results: PCWP increased from 8±4 to 35±9 mm Hg from rest to peak exercise with placebo. With nitroglycerin, there was a graded decrease in PCWP compared with placebo at rest (–1±2 mm Hg), 20W (–5±5 mm Hg), and peak exercise (–7±6 mm Hg; drug × exercise stage P =0.004). Nitroglycerin did not affect oxygen uptake at rest, 20W, or peak (placebo, 1.34±0.48 versus nitroglycerin, 1.32±0.46 L/min; drug × exercise P =0.984). Compared with placebo, nitroglycerin lowered stroke volume at rest (–8±13 mL) and 20W (–7±11 mL), but not peak exercise (0±10 mL). Conclusions: Sublingual nitroglycerin lowered PCWP during submaximal and maximal exercise. Despite reduction in PCWP, peak oxygen uptake was not changed. These results suggest that acute reductions in PCWP are insufficient to improve exercise capacity, and further argue that high PCWP during exercise is not by itself a limiting factor for exercise performance in patients with HFpEF. Registration: URL: https://www.clinicaltrials.gov ; Unique identifier: NCT04068844.

Rationale: Obesity presents a mechanical load to the thorax, which could perturb the generation of minute ventilation (V̇e) during exercise. Because the respiratory effects of obesity are not homogenous among all individuals with obesity and obesity-related effects could vary depending on the magnitude of obesity, we hypothesized that the exercise ventilatory response (slope of the V̇e and carbon dioxide elimination [V̇co (2)] relationship) would manifest itself differently as the magnitude of obesity increases. Objectives: To investigate the V̇e/V̇co (2) slope in an obese population that spanned across a wide body mass index (BMI) range. Methods: A total of 533 patients who presented to a surgical weight loss center for pre–bariatric surgery testing performed an incremental maximal cycling test and were studied retrospectively. The V̇e/V̇co (2) slope was calculated up to the ventilatory threshold. Patients were examined in groups based on BMI (category 1: 30–39.9 kg/m(2), category 2: 40–49.9 kg/m(2), and category 3: ≥50 kg/m(2)). Because the respiratory effects of obesity could be sex and/or age specific, we further examined patients in groups by sex and age (younger

Patients with heart failure with preserved ejection fraction (HFpEF) exhibit many cardiopulmonary abnormalities that could result in V˙/Q˙ mismatch, manifesting as an increase in alveolar dead space (VDDo patients with HFpEF develop VDTwenty-three patients with HFpEF and 12 control participants were studied. Gas exchange (ventilation [V˙VDThese data suggest that the increase in V˙/Q˙ mismatch may be explained by increases in VD

Introduction: Heart failure with preserved ejection fraction (HFpEF) patients exhibit a marked rise in PCWP during exercise, which may contribute to ventilation-perfusion (V/Q) mismatch and manifest as an increase in alveolar dead space (alveolar V D ) and alveolar-arterial PO 2 difference (AaPO 2 ). Nitrates reduce PCWP during exercise in HFpEF, but whether nitrates also reduce V/Q mismatch during exercise is unknown. Hypothesis: The increase in PCWP and V/Q mismatch during exercise would be attenuated with acute nitroglycerin (NTG) treatment compared with placebo in HFpEF patients. Methods: 13 patients performed a 6min cycling test at 20W and an incremental cycling test (with right-heart and arterial catheterization) with placebo and NTG treatment. The physiologic dead space to tidal volume (V D /V T ) was calculated using the Enghoff modification of the Bohr equation. Alveolar V D was calculated as: V D /V T x V T - anatomic dead space (anatomic V D , estimated as 2mL/kg lean body mass). AaPO 2 was calculated using the alveolar gas equation. Data were analyzed using a 2-way ANOVA. Results: PCWP decreased with NTG at 20W (placebo: 21.1±6.2 vs. NTG: 16.5±6.1mmHg, p=0.02) and peak exercise (placebo: 33.7±7.1 vs. NTG: 26.2±5.6mmHg, pD did not differ between treatments at rest (placebo: 0.11±0.07 vs. NTG:0.12±0.06L/breath, p=0.91), 20W (placebo: 0.22±0.09 vs. NTG: 0.24±0.10L/breath, p=0.62), or peak exercise (placebo: 0.34±0.14 vs. NTG:0.36±0.16L/breath, p=0.83). Nor did AaPO 2 differ between treatments at rest (placebo: 17.6±4.3 vs. NTG: 18.3±5.7mmHg, p=0.76), 20W (placebo: 22.0±6.9 vs. NTG: 22.1±8.1mmHg, p=0.99), or peak exercise (placebo: 25.1±9.1 vs. NTG: 27.8±9.9mmHg, p=0.41). No significant exercise-by-treatment interaction was detected for V D /V T (p=0.80). Conclusions: This study showed that NTG attenuated the increase in PCWP, but had no effect on the increase in alveolar V D or AaPO 2 during exercise. These findings suggest that the exercise-induced increase in V/Q mismatch may not be exclusively related to abnormal exercise hemodynamics. Further study is required to determine the clinical consequences and the mechanism(s) responsible for the progressive increase in V/Q mismatch during exercise in HFpEF patients.

Patients with heart failure with preserved ejection fraction (HFpEF) exhibit cardiopulmonary abnormalities that could affect the predictability of exercise [Formula: see text] from the Jones corrected partial pressure of end-tidal CO(2) (PJ(CO(2))) equation (PJ(CO(2)) = 5.5 + 0.9 × [Formula: see text] − 2.1 × V(T)). Since the dead space to tidal volume (V(D)/V(T)) calculation also includes [Formula: see text] measurements, estimates of V(D)/V(T) from PJ(CO(2)) may also be affected. Because using noninvasive estimates of [Formula: see text] and V(D)/V(T) could save patient discomfort, time, and cost, we examined whether partial pressure of end-tidal CO(2) ([Formula: see text]) and PJ(CO(2)) can be used to estimate [Formula: see text] and V(D)/V(T) in 13 patients with HFpEF. [Formula: see text] was measured from expired gases measured simultaneously with radial arterial blood gases at rest, constant-load (20 W), and peak exercise. V(D)/V(T[art]) was calculated using the Enghoff modification of the Bohr equation, and estimates of V(D)/V(T) were calculated using [Formula: see text] (V(D)/V(T[ET])) and PJ(CO(2)) (V(D)/V(T[J])) in place of [Formula: see text]. [Formula: see text] was similar to [Formula: see text] at rest (−1.46 ± 2.63, P = 0.112) and peak exercise (0.66 ± 2.56, P = 0.392), but overestimated [Formula: see text] at 20 W (−2.09 ± 2.55, P = 0.020). PJ(CO(2)) was similar to [Formula: see text] at rest (−1.29 ± 2.57, P = 0.119) and 20 W (−1.06 ± 2.29, P = 0.154), but underestimated [Formula: see text] at peak exercise (1.90 ± 2.13, P = 0.009). V(D)/V(T[ET]) was similar to V(D)/V(T[art]) at rest (−0.01 ± 0.03, P = 0.127) and peak exercise (0.01 ± 0.04, P = 0.210), but overestimated V(D)/V(T[art]) at 20 W (−0.02 ± 0.03, P = 0.025). Although V(D)/V(T[J]) was similar to V(D)/V(T[art]) at rest (−0.01 ± 0.03, P = 0.156) and 20 W (−0.01 ± 0.03, P = 0.133), V(D)/V(T[J]) underestimated V(D)/V(T[art]) at peak exercise (0.03 ± 0.04, P = 0.013). Exercise [Formula: see text] and V(D)/V(T[ET]) provides better estimates of [Formula: see text] and V(D)/V(T[art]) than PJ(CO(2)) and V(D)/V(T[J]) does at peak exercise. Thus, estimates of [Formula: see text] and V(D)/V(T) should only be used if sampling arterial blood during CPET is not feasible. NEW & NOTEWORTHY [Formula: see text] provides a better estimate of [Formula: see text] than PJ(CO(2)) at peak exercise, and V(D)/V(T[ET]) provides a better estimate of V(D)/V(T[art]) than V(D)/V(T[J]) at peak exercise. Although we reported significant correlations, we did not find an identity between [Formula: see text] and estimates of [Formula: see text] , nor did we find an identity between V(D)/V(T[art]) and estimates of V(D)/V(T[art]). Thus, caution should be taken and estimates of [Formula: see text] and V(D)/V(T) should only be used if sampling arterial blood during CPET is not feasible.

OBJECTIVE To compare temporal bone thickness along a three-dimensional arc of potential osseointegrated implant sites for bone-anchored hearing aids in children with and without aural atresia using computed tomographic imaging (CT). STUDY DESIGN Retrospective case review. SETTING Tertiary children's hospital. PATIENTS Children with or without aural atresia aged less than 11 years who had a temporal bone CT. INTERVENTION (S) Calvarial bone volume on CT was rendered in three-dimensional and thickness was reconstructed and measured at up to 12 defined sites along an arc of recommended implant sites. MAIN OUTCOME MEASURE (S) Determining whether a majority of observed potential implant sites have 2, 3, or 4 mm of bone thickness while controlling for age differences and atresia status. RESULTS A total of 40 atretic (from 34 patients) and 34 control (from 34 patients) temporal bones were compared using CT. Likelihood ratio tests indicated that diagnosis did not have a statistically significant effect on whether patients reached thresholds of 2, 3, or 4 mm at most observed sites (p = 0.781, 0.773, and 0.529, respectively) when adjusting for age. For all children measured, 93% had >50% of measured points greater than or equal to 2 mm thick. CONCLUSION Most children had greater than 2 mm of temporal bone thickness at >50% of the sites measured regardless of age or atresia diagnosis. The likelihood of reaching 4 mm of thickness at most sites improves with age. In unilateral patients, there was not a significant difference in thickness between affected and unaffected sides. There was also no significant difference in thickness when comparing patients with atresia to those without.

We investigated the contributions of obesity on multidimensional aspects of dyspnea on exertion (DOE) in patients referred for clinical cardiopulmonary exercise testing (CPET). Ratings of perceived breathlessness (RPB, Borg scale 0–10) were collected in obese (BMI ≥ 30; n = 47) and nonobese (BMI ≤ 25; n = 27) patients during two (one lower: ~30 W; and one higher: ~50 W) 4–6 min constant load cycling bouts. Multidimensional dyspnea profiles (MDP) were collected in the final 26 obese and 14 nonobese patients of the sample. RPB was greater (p < 0.05) in obese (3.3 ± 2.2 vs 2.4 ± 1.4) at lower work rates, but similar at higher work rates (4.9 ± 2.2 vs 4.4 ± 1.8). MDP sensory score including unpleasantness was 4.3 ± 2.2 in obese vs 2.5 ± 1.9 in nonobese (p < 0.001). The affective score was 1.9 ± 2.2 vs 0.7 ± 0.7, respectively (p < 0.01). Breathing sensations including ‘air hunger’, ‘effort’, and ‘breathing at lot’ were greater (p < 0.05) in obese, making these patients more frustrated/angry (p < 0.05). Obesity should be considered as a potential independent influencing factor that provokes DOE and unpleasantness when assessing breathlessness during CPET.

Most diagnostic tests assess the function of a single organ or organ system at rest. Conversely, exercise requires the integrated function of multiple systems under stress, including the cardiovascular, pulmonary, and musculoskeletal systems. The physical stress of exercise can expose physiological limitations not otherwise apparent at rest. This is particularly relevant for patients with respiratory and/or heart diseases in whom the increased physical demands of exercise quickly exhaust their reduced functional reserves, leading to the disabling symptoms of dyspnea, leg discomfort, and fatigue. The present chapter provides a framework for CPET performance and interpretation aimed at maximizing its clinical relevance. This approach underscores the principle that measurement of exertional symptoms, using validated scales and parameters of ventilatory control and dynamic respiratory mechanics, should be routinely used to optimize clinical CPET interpretation.

Background Near-peer teaching is effective in graduate medical education, but it has not been compared with faculty member teaching in resident simulation. In this study, we sought to compare debriefing sessions of internal medicine (IM) intern simulation sessions led by academic faculty doctors with those led by senior IM residents in order to measure the effectiveness of near-peer teaching in this setting. Near-peer teaching is effective in graduate medical education, but has not been compared with faculty member teaching in resident simulation METHOD: Internal medicine interns participated in four simulation cases, two of which were debriefed by faculty members and two of which were debriefed by residents. Pre-simulation knowledge assessment was completed prior to the case. Following each debriefing, interns completed a Debriefing Assessment for Simulation in Healthcare (DASH) survey. Post-simulation knowledge assessments were completed 6 months after simulation. Debriefings were recorded and transcribed. Each statement made during debriefing was classified as either correct or erroneous by blinded reviewers. Results Fifty interns participated in simulation, and the response rate on the DASH survey was 88%. There was no difference between DASH scores (p = 0.13), post-simulation knowledge assessments or error rates during debriefing (p = 0.31) for faculty member and resident instructors. Conclusion Our study suggests that residents and faculty members provide a similar quality of simulation instruction based on qualitative and quantitative evaluation.

Importance We present what we believe to be the first case series in which the teres major muscle is used as a free flap in head and neck reconstruction. Objectives To describe our experience with the teres major muscle in free flap reconstruction of head and neck defects and to identify advantages of this approach. Design, Setting, and Participants A retrospective review was performed at 2 tertiary care centers between February 1, 2007, and June 30, 2012. Data analysis was conducted from July 31, 2014, through December 1, 2014. Intervention Teres major muscle free flap for use in head and neck reconstruction. Main Outcomes and Measures Indications for use, complications, and outcomes including donor site morbidity. Results The teres major free flap was used in 11 patients as a component of chimeric subscapular system free flaps for a variety of complex head and neck defects. The teres major muscle was used to fill soft-tissue defects of the neck, face, and nasal cavity; it provided substantial soft-tissue volume but was less bulky than the latissimus dorsi muscle. The teres major muscle was also used to provide protection for vascular anastomoses and/or great vessels and to enhance soft-tissue coverage of the mandibular reconstruction plate. In addition, the muscle was selected as a substrate for skin grafting where inadequate neck skin remained. Flap survival occurred in 10 of 11 flaps (91%). Two flaps (18%) demonstrated venous congestion that was managed successfully. Two patients (18%) developed minor recipient-site complications (submental fistula and infection with recurrent wound dehiscence and plate exposure). All donor sites healed well, with chronic, mild shoulder pain noted in 2 patients (18%) and no postoperative seromas observed in any patient. Conclusions and Relevance Addition of the teres major muscle to a subscapular system free flap is an option for reconstruction of a variety of complex head and neck defects, particularly when a moderate amount of soft tissue is required. In select cases, the teres major muscle may have advantages over the latissimus dorsi muscle.

n a democratic society, education in the values and operation of the political system takes on a high level of importance. Citizens must be made conscious of the system within which policy is created and, as instructors at the college level, we face the task of presenting students with facts, theories, and opinions about government. Although instructors can introduce students to important ideas through lectures, readings, and discussions, many students best learn political concepts when given opportunities to apply those ideas in the context of the real world of politics. For these students, a particularly effective political science course is one that allows them to interact with political professionals so that the students can explore the meaning of the subject matter first-hand. Although this type of course is rare among the offerings of political science departments, the information that students glean from this sort of interaction can increase their knowl

We argue that fractional integration methods have the potential to unify and simplify time series analysis. Estimation of the d parameter in an ARFIMA (p, d, q) model is no longer difficult and multivariate extensions are proving useful. In particular, we discuss and illustrate the most promising route, fractional cointegration and the innovation of relaxing the assumption that the parent series are I(1). We illustrate the technique with an analysis of congressional approval, a topic of great interest to institutional scholars, and its relationship with economic expectations. © 1999 Elsevier Science Ltd. All rights reserved.