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Biomedical subjects

A F Wilson

Publications and source records attributed to A F Wilson.

At least 37 records · Page 2Linked to original sources
PubMed1999

Survival following bilateral staple lung volume reduction surgery for emphysema.

STUDY OBJECTIVES: Despite numerous reports of short-term response to lung volume reduction surgery (LVRS) for treatment of emphysema, to our knowledge, longer-term survival has not been reported. We describe survival following LVRS in a large cohort of 256 patients treated with bilateral staple LVRS (n = 236 video-assisted thoracic surgery [VATS] approaches, n = 20 median sternotomy) by a single group of physicians over a 3 1/2-year period from April 1994 to November 1997. DESIGN: Prospective survival study. Overall survival, survival stratified by preoperative presentation, and acute postoperative response were investigated using Kaplan-Meier methods. The simultaneous effects of preoperative predictors and postoperative response variables on survival were examined using a Cox proportional hazards model. SETTING: Community hospital and university medical center. PATIENTS: We studied 256 consecutive patients with severe emphysema treated with LVRS. INTERVENTIONS: Bilateral staple LVRS by VATS. MEASUREMENTS AND RESULTS: Overall survival information was known with certainty for 246 of 256 patients as of February 1, 1998. Median follow-up time was 623 days (range, 0 to 1,545 days). Mean FEV1 was 0.635L+/-0.015 L preoperatively and rose to 1.068L+/-0.029 L postoperatively. By standard analysis methods (missing patients censored at the time of last contact), 1-year survival was 85+/-2.3% compared with 83+/-2.4% 1-year survival with "worst case" analytic methods (assuming all missing patients died). Two-year survival averaged 81+/-2.7% by standard analysis vs 76+/-2.9% by worst case evaluation. Survival was significantly better for patients who were younger (< or = 70 years old, p = 0.02) and with higher baseline FEV1 (> 0.5, p < 0.03) and PO2 (> 54, p < 0.001). Patients who had greatest short-term improvement in FEV1 following surgery (> 0.56 L increase) also had significantly better longer-term survival following LVRS. CONCLUSIONS: To our knowledge, this is the first longer-term survival analysis of a large series of patients who underwent bilateral staple LVRS for emphysema. Substantial long-term mortality is seen, particularly within identifiable high-risk subgroups. Careful comparison to comparably matched control patients will be needed to definitively assess the benefits and risks of LVRS. This study suggests that prospective, controlled trials may need to stratify patient randomization based on preoperative risk factors to obtain meaningful results.

Aged↗
PubMed1998

Effect of lung volume reduction surgery on pulmonary diffusion capacity in a rabbit model of emphysema.

BACKGROUND: While there is renewed interest in lung volume reduction surgery (LVRS) for treatment of emphysema, many aspects of the operation such as patient selection and surgical end points of excision are uncertain. We studied the effects of LVRS on measured lung volumes and diffusion capacity in an animal model to investigate optimal resection volumes. METHODS: Emphysema was induced in 32 New Zealand white (NZW) rabbits using aerosolized elastase. Helium dilution lung volumes and single breath DLCO were measured concurrently at baseline, following induction of emphysema (preop), and 1 week postoperatively (postop) following LVRS. Bilateral upper and middle lobe stapled lung resections were performed through midline sternotomies with excision of variable amounts of lung tissue from 1.8 to 5.8 g. RESULTS: FRC increased following induction of emphysema and decreased postoperatively. DLCO improved with increasing lung tissue resection up to 3 g of tissue and then decreased as even greater amounts were removed (r = 0.54). CONCLUSIONS: Measured lung volumes increase with development of emphysema and appropriately decrease in response to LVRS in this rabbit model. DLCO improves with moderate resection but then decreases with excessive excision of lung quantities and may help define one physiologic operative end point. In this rabbit model, excision of approximately 30% of lung volume was optimal and prevented further decrease in diffusion capacity.

Animals↗
PubMed1998

Changes in pulmonary physiology after lung volume reduction surgery in a rabbit model of emphysema.

OBJECTIVE: The purpose of this study is to investigate the effects of lung volume reduction surgery on pulmonary compliance, airway flow, and helium lung volumes in an elastase-induced emphysema animal model. METHODS: A 15,000-unit bolus of elastase was aerosolized through an endotracheal tube in 14 New Zealand White rabbits to induce emphysema. Stapled lung volume reduction of bilateral upper and middle lobes was performed through a midline sternotomy at 4 weeks after induction of emphysema. Lung functions were measured at baseline before induction of emphysema, preoperatively at 4 weeks, and 1 week postoperatively. RESULTS: Compliance increased after induction of emphysema and decreased in response to lung volume reduction surgery. Functional residual capacity decreased after lung volume reduction surgery in proportion to the amount of excised lung tissue. Expired flows suggested improvement in response to lung volume reduction surgery. Histologic examination confirmed presence of diffuse heterogeneous emphysema in each animal at necropsy. CONCLUSIONS: The decreased compliance and increased airway flow after volume reduction surgery in this model parallels findings in human studies and suggests that similar mechanisms of increased elastic recoil and airway support contribute to improvement.

Animals↗
PubMed1998

Single-exhalation profiles of NO and CO2 in humans: effect of dynamically changing flow rate.

Endogenous production of nitric oxide (NO) in the human lungs has many important pathophysiological roles and can be detected in the exhaled breath. An understanding of the factors that dictate the shape of the NO exhalation profile is fundamental to our understanding of normal and diseased lung function. We collected single-exhalation profiles of NO and CO2 from normal human subjects after inhalation of ambient air (approximately 15 parts/billion) and examined the effect of a 15-s breath hold and exhalation flow rate (VE) on the following features of the NO profile: 1) series dead space, 2) average concentration in phase III with respect to time and volume, 3) normalized slope of phase III with respect to time and volume, and 4) elimination rate at end exhalation. The dead space is approximately 50% smaller for NO than for CO2 and is substantially reduced after a breath hold. The concentration of exhaled NO is inversely related to VE, but the average NO concentration with respect to time has a stronger inverse relationship than that with respect to volume. The normalized slope of phase III NO with respect to time and that with respect to volume are negative at a constant VE but can be made to change signs if the flow rate continuously decreases during the exhalation. In addition, NO elimination at end exhalation vs. VE produces a nonzero intercept and slope that are subject dependent and can be used to quantitate the relative contribution of the airways and the alveoli to exhaled NO. We conclude that exhaled NO has an airway and an alveolar source.

Adult↗
PubMed1998

Rate of FEV1 change following lung volume reduction surgery.

INTRODUCTION: Lung volume reduction surgery (LVRS) improves pulmonary function and dyspnea symptoms acutely in selected patients with heterogeneous emphysema. Limited data are available regarding long-term function following LVRS. We analyzed short-term (<6 months) and long-term rate of change of pulmonary function in 376 patients who underwent unilateral or bilateral LVRS using thoracoscopic or median sternotomy, staple, laser, or combined techniques. We hypothesized that the long-term rate of deterioration in lung function would be dependent on the surgical procedure used and would be greatest in those with the largest short-term postoperative improvement. METHODS: Pulmonary function was assessed preoperatively and at repeated intervals following LVRS. The change in pulmonary function over time was assessed for each patient by determining the individual change in FEV1 using linear regression analysis short and long term. Overall rate of change in pulmonary function was calculated for the composite group of patients and subgrouped by operative procedure. RESULTS: Lung function appears to improve in the first few months following LVRS in most patients, maximizing at approximately 3 to 6 months and declining thereafter. The short-term incremental improvement following staple procedures is superior to improvements following laser procedures or unilateral surgery: FEV1 increase (mean+/-SD) of 0.39+/-0.03 L for bilateral staple, 0.25+/-0.03 L for unilateral staple, 0.10+/-0.03 L for unilateral laser, and 0.22+/-0.1 L for mixed unilateral staple/laser procedures. However, the long-term rate of decline in FEV1 was greatest for bilateral staple LVRS procedures as well: 0.255+/-0.057 L/yr for bilateral staple, 0.107+/-0.068 L/yr for unilateral staple, 0.074+/-0.034 L/yr for unilateral laser, and 0.209+/-0.12 L/yr for mixed staple laser procedures. There was a general correlation between the magnitude of short-term incremental improvement and the rate of deterioration in FEV1 (r=0.292, p=0.003). CONCLUSIONS: While bilateral staple LVRS procedures lead to greater short-term improvement in FEV1, the more rapid rate of FEV1 decline in these patients and the general association between greater short-term incremental improvement and higher rates of deterioration raise questions regarding optimal long-term procedures. Further studies will be needed to answer these important questions.

Aged↗
PubMed1997

Comparison of sib-pair and variance-components methods for genomic screening.

The statistical properties of sib-pair and variance-components linkage methods were compared using the nuclear family data from Problem 2. Overall, the power to detect linkage was not high for either method. The variance-components method had better power for detection of linkage, particularly when covariates were included in the model. Type I error rates were similar to nominal error rates for both methods.

Analysis of Variance↗
PubMed1997

Comparison of Ho:YAG versus Nd:YAG thoracoscopic laser treatment of pulmonary bullae in a rabbit model.

OBJECTIVE: To determine the relative efficacy and morbidity of Ho:YAG versus Nd:YAG laser treatment of bullous lung disease in an animal model. SUMMARY BACKGROUND DATA: Laser coagulation procedures for treatment of emphysematous pulmonary bullae and heterogeneous emphysema continue to evolve. The role of lasers in lung volume reduction surgery remains controversial due to issues of relative efficacy and morbidity. The Nd:YAG laser is most commonly used for these procedures. We hypothesized that the shallower penetration of the Ho:YAG laser may be better suited for laser bullae coagulation and emphysema lung volume reduction with increased efficacy and reduced lung injury. METHODS: Thirty New Zealand White rabbits (15 normal rabbits; 15 with bullous lung disease) were evaluated with Ho:YAG compared to Nd:YAG laser exposures. Bullae were coagulated by either Ho:YAG or Nd:YAG treatment. In all animals (bullous-induced and normals), unaffected lung tissue in the upper lobes and contralateral lungs were treated with 5 spot exposures of Nd:YAG and Ho:YAG, each to assess depth of lung injury. Animals were sacrificed at Days 0, 7, and 21 and their lungs were examined histologically. RESULTS: Ho:YAG and Nd:YAG exposures caused equivalent lung injury to normal lung tissue. In the acute phase, parenchymal necrosis depth was similar for both Ho:YAG and Nd:YAG (850 +/- 273 microns vs. 900 +/- 270 microns respectively, p = 0.7). By Day 7, lung necrosis depth was 925 +/- 133 microns Ho:YAG vs. 1225 +/- 235 microns Nd:YAG (p = 0.33), and lung fibrosis depth was 300 +/- 134 microns Ho:YAG vs. 558 +/- 127 microns Nd:YAG (p = 0.11). By Day 21, pulmonary parenchymal necrosis was not seen. Pleural fibrosis depth was maximal at Day 21, reaching 250 +/- 102 microns for Ho:YAG vs. 300 +/- 156 microns Nd:YAG (P = 0.88). Pleural necrosis depth was 67 +/- 42 microns Ho:YAG vs 48 +/- 34 microns Nd:YAG (p = 0.42) on Day 7 and resolved by Day 21. During surgical coagulation procedures, the Ho:YAG laser was dramatically more efficient in coagulating bullae. The Ho:YAG laser required less exposure at equivalent power and resulted in immediate desiccation of bullae, in sharp contrast to the Nd:YAG laser. CONCLUSIONS: Because the Ho:YAG was more effective and did not result in more acute lung injury than the standard Nd:YAG laser in this study, Ho:YAG lasers may have improved potential for laser treatment of bullae or lung volume reduction surgery (LVRS) compared to Nd:YAG lasers.

Animals↗
PubMed1997

Preliminary evidence of linkage of salt sensitivity in black Americans at the beta 2-adrenergic receptor locus.

Salt sensitivity is a heritable trait that is a hallmark of hypertension in black Americans. Genes encoding adrenergic receptors are candidate loci for the inheritance of this hypertension-related trait because of the role of these receptors in the regulation of renal sodium excretion and vascular tone. We performed this study to determine whether these loci are responsible for some of the phenotypic variation in salt sensitivity. Hypertensive black American probands were ascertained, followed by sequential ascertainment of adult sib pairs among the first-, second- and third-degree relatives of the proband. Both hypertensive and normotensive siblings were tested for salt sensitivity by an intravenous sodium-loading, lasix volume-depletion protocol. Genotyping was performed with restriction fragment length polymorphisms in genomic DNA probed with clones containing the beta 2- and alpha 2c10-adrenergic receptor genes. A total of 109 sib pairs was evaluated. Salt sensitivity was defined as the change in blood pressure in each individual, comparing the sodium-loaded with the volume-depleted state. Systolic pressure decreased by an average of 9.0 +/- 9%, diastolic pressure by 1.5 +/- 11%, and mean arterial pressure by 5.0 +/- 9%. Neither blood pressure nor salt sensitivity was linked at the alpha 2c10-adrenergic receptor locus. No evidence suggested that systolic salt sensitivity and baseline blood pressure were linked at the beta 2-adrenergic receptor locus. Model-independent sib pair linkage analysis suggested that diastolic blood pressure response to sodium loading/volume depletion is linked at the beta 2-adrenergic receptor locus (P < .006). Evidence for linkage was significant at the .05 level after adjustment for the number of phenotypic traits examined.

Adult↗
PubMed1997

Objective predictors of response for staple versus laser emphysematous lung reduction.

Recently described surgical approaches to the treatment of emphysema, including buttressed stapled volume reduction and laser coagulation, are associated with variable clinical outcomes. We examined objective preoperative factors as predictors of response to treatment in patients enrolled in a randomized trial of staple versus laser volume-reduction surgery in order to help define patient selection criteria for these procedures. Seventy-two patients with severe symptomatic emphysema without bullae were entered into the protocol (39 staple, 33 laser). Preoperative objective variables (pulmonary function tests, smoking history, demographics, and graded chest computed tomographic [CT] scans) were evaluated as predictors of response to treatment (defined as a change in FEV1) at 3- to 6-mo follow-up, using linear and multivariate regression analysis. Follow-up pulmonary function was obtained on 90% of the 68 patients surviving at 6 mo. Overall improvement was significant only for staple-treated patients, and improved outcome correlated with greater smoking history and younger age for staple-treated patients. When physiologic variables were analyzed, greater smoking history, lower DL(CO), and younger age predicted improved outcome for laser-treated patients. Preoperative FEV1 and gas-exchange variables did not predict outcome in staple-treated patients. When CT scan grading was included in multivariate regression analysis, hyperinflation (increased thoracic gas volume) was the primary predictor of response for laser-treated patients. These findings suggest that younger patients with evidence of advanced emphysematous lung disease and hyperinflation are optimal candidates for lung-volume-reduction surgery, particularly by staple-reduction techniques. Additional studies with long-term follow-up, bilateral procedures, and assessment of other outcome measures must be performed to further define operative criteria for lung-volume-reduction surgery for emphysema.

Age Factors↗
PubMed1997

Effects of blood pH and blood lactate on growth hormone, prolactin, and gonadotropin release after acute exercise in male volunteers.

It has recently been found that prevention of the acidosis of anaerobic exercise blocks beta-endorphin release. Because heavy exercise affects secretion of other anterior pituitary hormones, we studied the results of alkali infusion and ingestion upon blood levels of four hormones: luteinizing hormone (LH), follicle-stimulating hormone (FSH), growth hormone (GH), and prolactin (PRL). Eight male subjects were studied after either 2 mEq/kg placebo (NaCl) or alkali (NaHCO3) administered before and during exercise to exhaustion. Blood samples were obtained before exercise and then 15, 30, 60, 90, 120, and 180 min postexercise. GH and PRL but not FSH or LH increased significantly postexercise, with a peak at 60 min, and subsequently declined back to baseline by 180 min. Base treatment reduced GH at baseline and postexercise (except at 60 min) and increased PRL significantly, particularly at 60 min. While the precise mechanisms on how acid/base changes affect hormone release remain to be defined, there are possible consequences on gonadal function and substrate availability during exercise.

Acidosis↗
PubMed1996

Absence of association or genetic linkage between the angiotensin-converting-enzyme gene and left ventricular mass.

BACKGROUND: Homozygous carries of the D allele of the angiotensin-converting-enzyme (ACE) gene have been reported to be at increased risk for various cardiovascular disorders, including left ventricular hypertrophy. We investigated the potential role of the ACE gene in influencing left ventricular mass. METHODS: Quantitative echocardiographic data and DNA samples were available for 2439 subjects from the Framingham Heart Study. ACE genotypes were determined by an assay based on the polymerase chain reaction. (The D allele of the ACE gene contains a deletion, whereas the I [insertion] allele does not.) Left ventricular mass and the prevalence of left ventricular hypertrophy, adjusted for clinical covariates, were analyzed according to genotype. Genetic linkage between the ACE locus and left ventricular mass was evaluated by quantitative analysis of pairs of siblings. RESULTS: The ACE genotype was associated neither with left ventricular mass nor with the prevalence of left ventricular hypertrophy. Mean (+/-SE) left ventricular mass (adjusted for sex) among subjects carrying the DD, DI, and II genotypes was 165+/-1.6, 165+/-1.3, and 166+/-2.0 g, respectively (P=0.90). The prevalence of left ventricular hypertrophy among the three genotype groups was 15.6 percent, 13.6 percent, and 15.6 percent, respectively (P=0.36), and the adjusted relative risk of left ventricular hypertrophy associated with the DD genotype was 1.10 (95 percent confidence interval, 0.86 to 1.19). Linkage analysis in 759 pairs of siblings using both the ACE D/I marker and a microsatellite polymorphism at the neighboring locus for the human growth hormone gene failed to support any role of ACE in influencing left ventricular mass. CONCLUSIONS: The ACE genotype showed no association with echocardiographically determined left ventricular mass, nor did it confer an increased risk of left ventricular hypertrophy. We found no appreciable role of the ACE gene in influencing left ventricular mass.

Adult↗
PubMed1996

Animal model for thoracoscopic laser ablation of emphysematous pulmonary bullae.

BACKGROUND AND OBJECTIVE: Thoracoscopic laser techniques have been described for treatment of pulmonary bullae. Clinical application of this procedure has proliferated despite limited data regarding efficacy or optimal techniques. The objective of this study was to develop an animal model for investigating laser treatment of bullous lung disease. STUDY DESIGN/MATERIALS AND METHODS: Sixty-two New Zealand White rabbits (3-5 kg) were injected intravenously with 0.35 cc sterile-filtered Sephadex G-100 beads (1 g/100 cc suspension). Three hours later, rabbits were anesthetized, intubated, and 10 cc 0.7% heat-treated or 1% untreated carrageenan solution was instilled endotracheally into a catheter wedged in a mainstem bronchus. RESULTS: Bullae formed over 4-6 weeks in 33% of the animals treated with 0.7% heat-treated carrageenan, and 90% of animals receiving 1% untreated carrageenan (P < 0.005) as demonstrated by serial thoracoscopy. Thoracoscopy was performed at 6-8 weeks using 5 mm trocars under general anesthesia and mechanical ventilatory support. Animals developed pulmonary bullae ranging in size from 0.5 to 2 cm. Bullae were ablated under thoracoscopic visualization using a CO2 laser with a 4 mm OD rigid probe and short focal length in a defocused mode, or an Nd:YAG laser with a 0.4 mm diameter flexible fiberoptic probe. Animals recovered quickly following thoracoscopy. CONCLUSION: We have successfully developed an animal model for thoracoscopic laser ablation of emphysematous pulmonary bullae. This animal model should be useful in investigating treatment of bullous lung disease in humans.

Animals↗
PubMed1996

Comparison of continuous versus pulsed CO2 and Nd:YAG laser-induced pulmonary parenchymal lung injury in a rabbit model.

BACKGROUND AND OBJECTIVE: Laser techniques have recently been described for treatment of patients with emphysema and bullous lung disease. Laser exposure of the pulmonary parenchyma during these procedures is complicated by laser-induced lung injury with substantial associated morbidity. Animal investigations are needed to develop methods that reduce lung injury. We hypothesized that the depth of injury could be reduced by pulsing laser exposures, with the goal of limiting thermal effects to more superficial tissue levels. In this study, we compared acute and chronic histologic injury resulting from pulsed- versus continuous-mode CO2 and Nd:YAG laser pulmonary parenchymal exposures in rabbits. STUDY DESIGN/MATERIALS AND METHODS: A total of 40 New Zealand White (NZW) rabbits underwent thoracotomy followed by exposure with CO2 laser (n = 10 continuous vs. n = 10 pulsed at 250 Hz with duty cycle 0.15 ms) or ND:YAG laser (n = 10 continuous vs. n = 10 pulsed at 10 Hz with duty cycle 0.10 sec) to the visceral pleural surface using 1 minute of laser exposure (5 watts, defocused to 70 W/cm2 power density) to the exposed lung surface. Rabbits were sacrificed at 4 and 21 days post-injury, and lungs were examined histologically. RESULTS: CO2 and Nd:YAG laser treatment resulted in substantial pulmonary parenchymal injury. While CO2 laser-induced damage was distinct from Nd:YAG histologically, pulsed-mode laser exposures did not reduce lung injury for either laser. Acute edema occurred to depths of 1180 +/- 338 microns for continuous-mode CO2 laser exposures compared to 1,340 +/- 430 microns in pulsed mode (p = .77). For Nd:YAG laser exposure, acute edema depth was 750 +/- 748 microns continuous versus 1120 +/- 367 microns pulsed mode (p = .65). Chronic lung fibrosis depth was 450 +/- 164 microns for CO2 continuous mode compared to 575 +/- 170 microns in pulsed mode (p = .61). Lung fibrosis depth for Nd:YAG was 550 +/- 96 microns, continuous versus 484 +/- 180 microns pulsed mode (p = .76). CONCLUSION: The similarity in injury between pulsed- and continuous-mode exposures suggests that thermal relaxation times are long relative to the selected pulse frequencies in intact living rabbit lungs. Alternatively, brief high-energy pulsations may increase focal temperatures with a tendency to increase injury depth relative to the penetration of the laser light. Thus, pulsed laser modes in these settings appear to be ineffective in reducing laser-induced lung injury in clinical settings.

Animals↗
PubMed1996

Doppler grid surface scanning applications for pulmonary subsurface parenchymal perfusion assessment.

Subsurface perfusion to lung parenchyma underlying the pleura is difficult to assess in live ventilated animals. The purpose of this study was to assess applicability of a newly developed laser Doppler grid scanning imaging technology that measures perfusion of pleural subsurface lung regions in intact normal and abnormal animal lungs. Eighty-six Doppler grid perfusion measurements were performed in five New Zealand White Rabbits (3-5 kg); four with unilateral bullous lung disease, one normal control. Left upper lobe lung surface was exposed to 10 1-sec spot Nd:YAG exposures (70 W/cm2). One week following laser exposure, all rabbits underwent sequential bilateral open thoracotomy. Unaffected left lower lobes in these animals and all four lobes of a previously untreated rabbit were used as controls. Pleural subsurface perfusion measurements were recorded over a contiguous 900-pixel square surface grid using quantitative noncontact laser Doppler imaging during open thoracotomy procedures. Scans were obtained in a normal volume ventilation mode, at 30 cm of inspiratory hold airway pressure, and postinflation. A perfusion-pressure response curve was obtained in normal lung at 10-, 20-, and 30-cm static airway pressure. Post mortem measurements were used as 0 flow controls. Normal lung tissue was found to have relatively high pleural subsurface perfusion (1362 +/- 328 corrected units on a scale of 0-4095). Areas of atelectasis had decreased perfusion (659 +/- 512 U., 48.4 +/- 12.5% compared to normal lung, p < 0.02), but returned to normal levels after inflation of the lung (1253 +/- 363 U., p = 0.21 compared to normal). Pleural subsurface perfusion decreased uniformly and progressively as lung inflation pressure increased (p < 0.0001). Perfusion increased immediately to supranormal values following release of high inspiratory inflation pressure holds (1603 +/- 626 U., 117 +/- 18% compared to normal lung, p = 0.03). Bullae had markedly decreased perfusion (541 +/- 68 U.) that was not further reduced by increased inflation pressures. Noncontact laser Doppler grid perfusion imaging appears to provide a new tool for measuring pleural subsurface perfusion over a large area of lung surface in clinical experimental settings. Results are rapid, reproducible, and consistent. Sampling errors inherent in current point sampling Doppler flow techniques are reduced by the multiple contiguous measurements. We have used this technique to demonstrate inspiratory pressure-related reduction in pleural subsurface perfusion in normal lung, reversible decreased perfusion in atelectatic regions, and reduced perfusion in bullous and laser-treated lung regions.

Analysis of Variance↗
PubMed1996

Almost simultaneous measurement of cardiovascular and gas exchange variables during maximal exercise.

We measured gas exchange variables such as oxygen uptake, carbon dioxide output, and lung diffusing capacity using noninvasive techniques almost simultaneous with assessment of cardiovascular variables such as pulmonary blood flow at several levels of treadmill exercise up to and including maximal capacity. We utilized a single breath exhalation technique for measurement of diffusing capacity and cardiac output and breath by breath methodology for evaluating oxygen uptake. The equipment required for these measurements--rapid gas analyzers, oximeters, on-line computation, and pneumatic valves--are well within the capabilities of many exercise laboratories and are not difficult to use with subjects even at the heaviest levels of exercise. The results agreed well with values reported in the literature. From these entirely noninvasive measures, we calculated mixed venous oxygen saturation and maximal tissue oxygen diffusing capacity.

Adult↗
PubMed1996

Heritability of salt sensitivity in black Americans.

Salt sensitivity is defined as a change in blood pressure in response to changes in salt and water homeostasis. Found in 73% of hypertensive and 36% of normotensive blacks, it is generally considered a hallmark of hypertension in blacks. The higher prevalence of salt sensitivity in blacks compared with whites suggests a genetic influence on this trait, but there is little direct evidence of heritability. We determined the extent to which salt sensitivity is correlated in black families and estimated the heritability of this phenotype. Black families were recruited through a hypertensive proband. Both hypertensive and normotensive adults were phenotyped with respect to salt sensitivity with an intravenous sodium-loading, furosemide volume-depletion protocol. Salt sensitivity was defined as the difference between sodium-loaded and volume-depleted blood pressure. We enrolled 20 families, comprising 30 parent-offspring pairs and 115 adult sibling pairs. Age-adjusted familial correlations ranged from .33 to .44, .19 to .37, and .12 to .21 for mean arterial and systolic and diastolic pressure responses to the salt sensitivity maneuver, respectively. Corresponding heritability estimates were 0.26 to 0.84, 0.26 to 0.74, and 0.004 to 0.24, respectively. These data strongly suggest a heritable component of salt sensitivity.

Adult↗
PubMed1996

CO2 and Nd:YAG laser-induced pulmonary parenchymal lung injury in a rabbit model.

Laser exposure of the pulmonary parenchyma during treatment of emphysema and other clinical indications causes acute lung injury. Animal investigations are needed to understand and control laser-induced lung injury. We hypothesized that lung injury is deeper from Nd:YAG laser exposures than CO2 exposures because of deeper penetration of Nd:YAG wavelength light. We compared the temporal evolution of histologic injury in rabbits resulting from continuous mode shallow CO2 and Nd:YAG laser pulmonary parenchymal exposures applied in rabbits. Forty-six New Zealand white (NZW) rabbits underwent treatment with CO2 laser (n=18), Nd:YAG laser (n=18), or sham thoracotomy control (n=10) to the visceral pleural surface using 1 min of exposure (5 watts, defocused to 70 W/cm2 power density for both lasers). Animals were killed at 0, 4, 7, 21, and 49 d after exposure. Lung injury, similar to that seen clinically in humans, developed in all laser-treated animals. Injury progressed from ischemia and vascular congestion, to edema and necrosis, followed by pleural and parenchymal fibrosis. The acute injury was qualitatively distinct and slightly deeper in CO2 than Nd:YAG-treated animals (p<0.02) despite the shallower depth of penetration of the CO2 laser. These findings may imply that higher absorption coefficient for CO2 laser energy results in greater focal temperatures and injury in the areas of direct exposure, and suggest that Nd:YAG laser exposure at these settings may cause shallower injury than CO2 lasers in humans undergoing clinical treatment.

Absorption↗