The capillary bed offers the largest hemodynamic resistance to the cortical blood supply.

The cortical angioarchitecture is a key factor in controlling cerebral blood flow and oxygen metabolism. Difficulties in imaging the complex microanatomy of the cortex have so far restricted insight about blood flow distribution in the microcirculation. A new methodology combining advanced microscopy data with large scale hemodynamic simulations enabled us to quantify the effect of the angioarchitecture on the cerebral microcirculation. High-resolution images of the mouse primary somatosensory cortex were input into with a comprehensive computational model of cerebral perfusion and oxygen supply ranging from the pial vessels to individual brain cells. Simulations of blood flow, hematocrit and oxygen tension show that the wide variation of hemodynamic states in the tortuous, randomly organized capillary bed is responsible for relatively uniform cortical tissue perfusion and oxygenation. Computational analysis of microcirculatory blood flow and pressure drops further indicates that the capillary bed, including capillaries adjacent to feeding arterioles (d < 10 µm), are the largest contributors to hydraulic resistance.

Changes in pulsatility and resistance indices of cerebral arteriovenous malformation feeder arteries after embolization and surgery.

OBJECTIVES: Embolization reduces flow in cerebral arteriovenous malformations (AVMs) before surgical resection, but changes in pulsatility and resistance indices (PI, RI) are unknown. Here, we measure PI, RI in AVM arterial feeders before and after embolization/surgery. METHODS: Records of patients who underwent AVM embolization and surgical resection at our institution between 2007 and 2014 and had PI, RI, and flows obtained using quantitative magnetic resonance angiography were retrospectively reviewed. PI = [(systolic - diastolic flow velocity)/mean flow velocity] and RI = [(systolic - diastolic flow velocity)/systolic flow velocity]. Hemodynamic parameters were compared between the feeder and contralateral artery before and after embolization/surgery. RESULTS: 38 patients were included (6 embolization only, 24 embolization and surgery, 8 surgery only). After embolization, flow volume rates within feeders decreased significantly (p < 0.001) to match flows in their contralateral counterparts (p = 0.78). On the other hand, mean, systolic, and diastolic flow velocities (p = 0.60, 0.32, 0.34, respectively) as well as PI, RI (p = 0.99, 0.68) did not change significantly after embolization. However, after surgery mean, systolic, and diastolic flow velocities within feeders decreased significantly (p = 0.001, 0.002, 0.001, respectively) and PI, RI normalized to match the indices of their contralateral counterparts (p = 0.46, 0.46). CONCLUSION: Following partial AVM embolization, PI, RI are unchanged and flow velocities in feeder arteries also remain unchanged likely due to redistribution of flow through residual nidus. Thus, staged management of AVMs is unlikely to increase outflow resistance and offers a safe treatment strategy.

Lung function, transfusion, pulmonary capillary blood volume and sickle cell disease.

Lung function abnormalities occur in children with sickle cell disease (SCD) and may be associated with elevated pulmonary blood volume. To investigate that association, we determined whether blood transfusion in SCD children acutely increased pulmonary capillary blood volume (PCBV) and increased respiratory system resistance (Rrs5). Measurements of Rrs5 and spirometry were made before and after blood transfusion in 18 children, median age 14.2 (6.6-18.5) years. Diffusing capacity for carbon monoxide and nitric oxide were assessed to calculate the PCBV. Post transfusion, the median Rrs5 had increased from 127.4 to 141.3% predicted (p<0.0001) and pulmonary capillary blood volume from 39.7 to 64.1 ml/m2 (p<0.0001); forced expiratory volume in one second (p=0.0056) and vital capacity (p=0.0008) decreased. The increase in Rrs5 correlated with the increase in PCBV (r=0.50, p=0.0493). Increased pulmonary capillary blood volume may at least partially explain the lung function abnormalities in SCD children.

Lowering Pulmonary Wedge Pressure after Heart Transplant: Pulmonary Compliance and Resistance Effect / Redução da Pressão Capilar Pulmonar após Transplante Cardíaco: Complacência Pulmonar e Efeito Resistência

AbstractBackground:Right ventricular (RV) afterload is an important risk factor for post-heart transplantation (HTx) mortality, and it results from the interaction between pulmonary vascular resistance (PVR) and pulmonary compliance (CPA). Their product, the RC time, is believed to be constant. An exception is observed in pulmonary hypertension because of elevated left ventricular (LV) filling pressures.Objective:Using HTx as a model for chronic lowering of LV filling pressures, our aim was to assess the variations in RV afterload components after transplantation.Methods:We retrospectively studied 159 patients with right heart catheterization before and after HTx. The effect of Htx on hemodynamic variables was assessed.Results:Most of the patients were male (76%), and the mean age was 53 ± 12 years. HTx had a significant effect on the hemodynamics, with normalization of the LV and RV filling pressures and a significant increase in cardiac output and heart rate (HR). The PVR decreased by 56% and CPA increased by 86%. The RC time did not change significantly, instead of increasing secondary to pulmonary wedge pressure (PWP) normalization after HTx as expected. The expected increase in RC time with PWP lowering was offset by the increase in HR (because of autonomic denervation of the heart). This effect was independent from the decrease of PWP.Conclusion:The RC time remained unchanged after HTx, notwithstanding the fact that pulmonary capillary wedge pressure significantly decreased. An increased HR may have an important effect on RC time and RV afterload. Studying these interactions may be of value to the assessment of HTx candidates and explaining early RV failure after HTx.

ResumoFundamento:A pós-carga do ventrículo direito (VD) é um fator de risco importante para avaliar a mortalidade decorrente de transplante cardíaco (HTx) e resulta da interação entre a resistência vascular pulmonar (RVP) e a complacência pulmonar (CPA). Acredita-se que o produto da interação, o RC-time, seja constante. Entretanto, é exceção a hipertensão pulmonar devido às elevadas pressões de preenchimento do ventrículo esquerdo (VE).Objetivos:Ao utilizar o HTx como modelo para redução crônica das pressões de preenchimento do VE, nosso objetivo foi avaliar as variações nos componentes pós-carga do VD após o transplante.Métodos:Foram estudados, retrospectivamente, 159 pacientes com cateterismo cardíaco direito realizado antes e após o HTx. O impacto do HTx nas variáveis hemodinâmicas foi avaliado.Resultados:A maioria dos pacientes foi do sexo masculino (76%) e a média de idade foi 53 ± 12 anos. O HTx teve um efeito significativo na hemodinâmica, com normalização do VE e das pressões de preenchimento de VD e no aumento significativo do débito cardíaco e da freqüência cardíaca (FC). A RVP diminuiu 56% e a CPA aumentou 86%. Em vez de aumentar como era esperado, o RC-time não alterou significativamente e teve papel secundário em relação à normalização da pressão capilar pulmonar (PECP) após o HTx. O aumento esperado no RC timecom PWP reduzido foi atenuado pelo aumento da FC (devido à denervação autonômica do coração). Esse efeito ocorreu independentemente da diminuição da PCPConclusões:O RC-time permaneceu inalterado após HTx, entretanto a PECP diminuiu significativamente. O aumento da FC pode ter impacto importante no RC-time e na pós-carga do VD. O estudo dessas interações pode ser de grande valor para avaliar os candidatos HTx e explicar a falência do VD ocorrida logo após o HTx.

Lowering pulmonary wedge pressure after heart transplant: pulmonary compliance and resistance effect.

BACKGROUND: Right ventricular (RV) afterload is an important risk factor for post-heart transplantation (HTx) mortality, and it results from the interaction between pulmonary vascular resistance (PVR) and pulmonary compliance (CPA). Their product, the RC time, is believed to be constant. An exception is observed in pulmonary hypertension because of elevated left ventricular (LV) filling pressures. OBJECTIVE: Using HTx as a model for chronic lowering of LV filling pressures, our aim was to assess the variations in RV afterload components after transplantation. METHODS: We retrospectively studied 159 patients with right heart catheterization before and after HTx. The effect of Htx on hemodynamic variables was assessed. RESULTS: Most of the patients were male (76%), and the mean age was 53 ± 12 years. HTx had a significant effect on the hemodynamics, with normalization of the LV and RV filling pressures and a significant increase in cardiac output and heart rate (HR). The PVR decreased by 56% and CPA increased by 86%. The RC time did not change significantly, instead of increasing secondary to pulmonary wedge pressure (PWP) normalization after HTx as expected. The expected increase in RC time with PWP lowering was offset by the increase in HR (because of autonomic denervation of the heart). This effect was independent from the decrease of PWP. CONCLUSION: The RC time remained unchanged after HTx, notwithstanding the fact that pulmonary capillary wedge pressure significantly decreased. An increased HR may have an important effect on RC time and RV afterload. Studying these interactions may be of value to the assessment of HTx candidates and explaining early RV failure after HTx.

[Raynaud's phenomenon and other circulatory disorders of the fingers]. / Das Raynaud-Phänomen und andere Durchblutungsstörungen der Finger.

Raynaud's phenomenon (RP) is defined as attacks of blanking, subsequent cyanosis and rubeosis of fingers due to vasospasms in response to cold or emotional stimuli. Primary RP has no known underlying cause and occurs mainly in young and otherwise healthy women. Secondary RP goes along with various causes such as connective tissue diseases, toxic substances, drugs, physical trauma or organic finger artery occlusions, and occurs at any age and in both genders. Related affections are acrocyanosis and finger artery occlusions either due to arteriosclerosis or vasculitis. Also spontaneous finger hematoma may provoke an episode of RP. Therapeutically strict cold protection and avoidance of possible noxa is recommended besides the treatment of underlying diseases. No standard vasoactive drug has proven ideal for RP due to side effects. In cases with rest pain or ulcerations the same principles are applied as in ischemic diseases with no possibility for revascularization.

Le phénomène de Raynaud(PR) est défini comme des attaques de blancheur suivie d'une cyanose et d'une rougeur des doigts dues à un vasospasme en réponse au froid ou à un stimulus émotionnel. Le PR primaire n'a pas de cause connue et atteint surtout des jeunes femmes qui sont par ailleurs en bonne santé. Le PR secondaire se rencontre avec des causes variées comme la sclérodermie, des substances toxiques, des médicaments, des traumatismes physiques ou des occlusions artérielles au niveau des doigts. Cette forme de PR peut survenir à tout âge, tant chez l'homme que chez la femme. Des affections relatées au PR sont l'acrocyanose et les occlusions des artères digitales dues à l'artériosclérose ou une vasculite. Enfin, un hématome spontané au niveau d'un doigt peut provoquer un PR. Une protection stricte contre le froid et l'évitement autant que possible des facteurs favorisants est recommandé, ceci en plus du traitement de la maladie sous-jacente. Il n'y a pas de médicament vasoactif standard idéal pour traiter le PR, particulièrement en raison de leurs effets secondaires. En cas de douleur au repos ou en présence d'ulcérations les mêmes principes de traitement sont appliqués que lors d'affections ischémiques, avec cependant l'impossibilité d'effectuer une revascularisation.

Capillary refill time is a predictor of short-term mortality for adult patients admitted to a medical department: an observational cohort study.

BACKGROUND: Capillary refill time (CRT) has been advocated as a tool for rapid assessment of circulatory status. The correlation between neither CRT and mortality nor CRT and markers of circulatory status has been assessed. We performed a prospective observational cohort study to assess the relationship between CRT (using two existing definitions and as a continuous variable) and short-term mortality. METHODS: We included all acutely admitted adult patients to a medical admission unit. We measured CRT, blood pressure, pulse, temperature and peripheral oxygen saturation. We presented the data descriptively. Difference between continuous data was analysed using Wilcoxon Rank Sum Test and categorical data using χ(2) test. The primary endpoint was 1-day all-cause mortality. RESULTS: 3046 patients were enrolled and CRT was measured on 1935. In univariate analyses, we found increasing all-cause 1-day mortality with all definitions of CRT. Performing multivariable analysis, controlling for age, sex, mean blood pressure, pulse, temperature and peripheral oxygen saturation, we found increasing CRT as a continuous variable and according to the Schriger and Baraff definition to be associated with increased mortality. Both the Trauma score and Schriger and Baraff definitions had high negative predictive values. The calculations on the Schriger and Baraff definition were based on limited power. CONCLUSIONS: We found a significant association between CRT measured as a continuous variable and short-term mortality. Using the definition of Schriger and Baraff also seems appropriate, but this is based on calculations of limited power.

Systemic sclerosis patients with and without pulmonary arterial hypertension: a nailfold capillaroscopy study.

OBJECTIVE: Pulmonary arterial hypertension (PAH) is a complication of SSc due to increased vascular resistance, and abnormal vascularity is a well-known feature of the disease as shown by nailfold videocapillaroscopy (NVC). This study investigated for specific NVC changes in SSc patients with and without PAH to assess any useful difference. METHODS: Twenty-four SSc patients, 12 with PAH and 12 without, entered the study. Evidence of PAH was defined as increased systolic pulmonary artery pressure (PAP) (≥35 mmHg), indirectly assessed by echocardiography and confirmed by right heart catheterization (mPAP > 25 mmHg). NVC was performed, and a semi-quantitative rating scale, a rating system for avascular areas and a specific NVC pattern evaluation, namely early, active and late, were used. RESULTS: An NVC score >1 was more frequently found in patients with PAH than those without, 11 cases (92%) vs 5 cases (42%) (P = 0.03); an avascular areas grade >1 was present in 10 (83%) and 2 (17%) cases, respectively (P = 0.003); and a more severe NC pattern (active/late) was described in 11 (92%) and 5 (42%) patients, respectively (P = 0.03). When we compared the mPAP with NVC parameters, we found significant correlations between mPAP values and the NVC score (P < 0.005) and with the avascular areas score (P < 0.001). CONCLUSION: Our results underline the relevance of early microvascular assessment in patients at risk of developing a severe complication such as PAH that can amplify the systemic microvascular impairment in SSc. More severe NVC abnormalities should lead to strict cardiopulmonary surveillance and a complete NVC study is indicated.

[Optimization approach to arterial hemodynamics in elastic capillaries].

The article considers a number of ways of optimizing arterial hemodynamics including finding of the best value of capillary resistance or coefficient of elasticity.

The two layer method does not improve the preservation of porcine kidneys.

BACKGROUND: The Two layer method (TLM) has been extremely successful in the preservation of the pancreas. However, this has not been thoroughly investigated in other organs or in clinically relevant large animal models. The aim of this study was to assess the effects of TLM in a large animal model of kidney preservation. MATERIAL/METHODS: Porcine kidneys were retrieved after 10 minutes of warm ischaemic injury and flushed with 300 ml UW solution at 4°C. Kidneys were then either placed in University of Wisconsin solution (UW) or TLM using pre-oxygenated perfluorodecalin and UW. Kidneys were stored for 18 hours at 4°C then reperfused with oxygenated autologous blood to assess renal function. RESULTS: Renal blood flow (RBF) was significantly lower and intra-renal resistance (IRR) higher in TLM compared to UW group [Area under the curve (AUC) RBF, UW; 427±168 vs TLM; 247±55 ml/min/100g.h; P=0.041, AUC IRR, UW; 7.7±2.2 vs TLM; 10.5±1.9 ml/min/mmHg; P=0.041]. Levels of creatinine clearance (CrCl) were significantly lower in TLM group [AUC CrCl, UW; 1.8±1.0 vs TLM; 0.6±0.4 ml/min/100 g.h; P=0.034]. Levels of lipid peroxidation were significantly lower in TLM group [8-isoprostane/Cr ratio 3h; UW 3338±896 vs TLM 2072±886 pg/ml/mmol/L; P=0.04]. Levels of total nitric oxide were significantly higher in TLM group (P=0.009). CONCLUSIONS: TLM did not improve the preservation condition of porcine kidneys. Furthermore, there appeared to be increased inflammation, endothelial injury and reduced renal function compared to preservation with UW. Further experimental work is needed to determine the role of PFC in kidney preservation.

Intermittent versus constant aerobic exercise: effects on arterial stiffness.

Aerobic exercises (of sufficient duration and intensity) decreases arterial stiffness. However, the direct relationship between the type of aerobic exercise (i.e. constant versus interval) and the alteration in arterial stiffness has been poorly explored. We evaluated the hemodynamic responses of 11 healthy males (22.5 +/- 0.7 years, height 177.7 +/- 1.1 cm, body mass 70.5 +/- 2.4 kg) following acute constant (CE) and intermittent cycling exercise (IE). Exercise duration and intensity (mean heart rate) were matched during both exercises (142.9 +/- 2.4 bpm for CE and 144.2 +/- 2.4 bpm for IE). Heart rate (HR) and cardiac output (CO) were measured throughout the whole session, while blood pressure and pulse wave velocity (PWV) were measured during pre exercise and 30 min recovery. Arterial stiffness and cardiac autonomic control were assessed through PWV and heart rate variability, respectively. After IE, lower limb arterial stiffness was significantly and steadily decreased compared to pre exercise value (from 8.6 +/- 0.1 to m s(-1) to 7.6 +/- 0.3 to m s(-1) at 30 min) and was lower than after CE (8.2 +/- 0.3 m s(-1) at 30 min, which did not significantly change compared to pre exercise: 8.7 +/- 0.2 m s(-1)). We hypothesized that the higher HR and lower arterial stiffness after IE were likely due to variations in peripheral vascular changes during the exercise which may trigger the release of endothelial or metabolic vasoactive factors. These data appear to show that IE may result in a greater stimulus for vascular adaptations when compared to CE.

Pulsatile stress correlates with (micro-)albuminuria in renal transplant recipients.

Pulsatile stress is defined as product of pulse pressure (PP) and heart rate (HR) and is largely regulated by arterial stiffness in general and specifically with reference to patients with renal insufficiency by sympathetic nerve activity. Direct effects of the pulsatile stress on heart, coronary system and ultimately cardiovascular survival have been documented whereas no data exist relating to renal transplant patients. We analysed the relation of macrocirculatory disturbance to microcirculatory defects in 92 renal transplant recipients. Therefore, we investigated aortic stiffness by carotid-femoral pulse wave velocity (PWV), pulsatile stress and albuminuria. Pulsatile stress, not PWV was associated with the extent of albuminuria (r = 0.29; P < 0.01 and r = 0.06; P = 0.6 respectively), which was confirmed in multivariate stepwise regression analysis (P = 0.008). Dividing the data in tertiles of pulsatile stress revealed an eightfold increased risk for microalbuminuria and 12.2-fold increased risk for macroalbuminuria comparing upper with lower tertile of pulsatile stress. Pulsatile stress, not PWV correlates with albuminuria and predicts the degree of albuminuria in renal transplant recipients. Therefore, pulsatile stress reflects an easy and cost-effective marker for renal microcirculatory defects in renal transplant patients.

Mortality and functional morbidity after use of PALS/APLS by community physicians.

OBJECTIVES: To test the hypothesis that pediatric shock is a common cause of death and functional morbidity and that pediatric advanced life support (PALS)/advanced pediatric life support (APLS) resuscitation in the community hospital setting improves child health outcomes. METHODS: This study included all children consecutively transported to 5 regional, tertiary care children's hospitals over 4 years, and is a prospective cohort study comparing outcomes in children who did or did not receive PALS/APLS resuscitation in the community hospital. RESULTS: Shock occurred in 37% of the patients transferred to the tertiary centers. Regardless of trauma status, children with shock had an increased mortality rate compared with those without shock (all patients: 11.4% vs 2.6%), trauma patients (28.3% vs 1.2%), and nontrauma patients (10.5% vs 2.8%). Early shock reversal was associated with reduced mortality (5.06% vs 16.37%) and functional morbidity (1.56% vs 4.11%) rates. Early use of PALS/APLS-recommended interventions was associated with reduced mortality (8.69% vs 15.01%) and functional morbidity (1.24% vs 4.23%) rates. After controlling for center, severity of illness, and trauma status, early reversal of shock and use of PALS/APLS-recommended interventions remained associated with reduced morbidity and mortality rates. CONCLUSIONS: Shock is common in children who are transferred for tertiary care. Pediatric shock recognition and resuscitation in the community hospital improves survival and functional outcome regardless of diagnostic category. The development of shock/trauma systems for children with and without trauma seems prudent.

Effects of lifestyle modification on central artery stiffness in metabolic syndrome subjects with pre-hypertension and/or pre-diabetes.

AIMS: To examine the effects of a 24-week lifestyle intervention prescribed by family doctors on carotid artery stiffness in metabolic syndrome (MS) subjects with pre-hypertension and/or pre-diabetes. METHODS: Sixty-three middle-aged and older subjects with pre-hypertension and/or pre-diabetes were divided into subjects without MS (MS-) and with MS (MS+). MS components and carotid artery stiffness by ultrasound were determined at baseline, at 8 weeks, and following the 24 weeks of lifestyle intervention. Family doctors prescribed an individually customized lifestyle prescription for aerobic exercise and Mediterranean-style diet. RESULTS: Carotid artery distensibility significantly increased in MS+ following the 24 weeks of intervention compared with baseline (0.191+/-0.012 vs. 0.143+/-0.011, 1/mmHg x 10(-2), p<0.05). Similarly, beta stiffness index decreased in MS+ following the 24 weeks of intervention (9.8+/-1.1 vs. 12.5+/-1.1 AU, p<0.05). Following the intervention, waist circumference, BP and fasting glucose levels reduced in MS+ (all p<0.05), and 13 MS+ subjects were free from MS. CONCLUSIONS: The results show the reduction of carotid artery stiffness and the improvement of some MS components in MS subjects, suggesting a favorable effect of our lifestyle modification strategy on central artery stiffness as well as MS components in MS subjects.

Arterial elasticity and plasma levels of adiponectin and leptin in type 2 diabetic patients treated with thiazolidinediones.

BACKGROUND: Thiazolidinediones (TZDs) improve peripheral insulin sensitivity, but the effect on arterial stiffness is less clear. The aim of the present study was to assess the differential effect of pioglitazone or rosiglitazone on arterial stiffness and plasma levels of adiponectin and leptin in patients with type 2 diabetes mellitus. METHODS: Thirty-five type 2 diabetic subjects were randomly assigned to receive pioglitazone (30 mg/day; n = 14), rosiglitazone (4 mg/day; n = 11), or placebo (medical nutrition therapy; n = 10) for 12 weeks. Changes in plasma glucose, glycosylated hemoglobin, insulin resistance (HOMA-IR), total cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, triglycerides, adiponectin, and leptin were evaluated at baseline and after 12 weeks. In parallel, large arterial compliance (C1) and small arterial compliance (C2) were measured at baseline and at the end of treatment period. RESULTS: At 12 weeks, the rosiglitazone (P = 0.026) and pioglitazone (P = 0.004) groups had a significant increase from baseline in adiponectin that was not seen in the medical nutrition therapy group. No significant changes in plasma leptin and in C1 and C2 elasticity indexes were observed over the entire study period in any of the treatment groups. CONCLUSIONS: In this study of patients with type 2 diabetes, treatment with TZDs was associated with a significant improvement in adiponectin levels, although no significant effects were seen on leptin levels and arterial elasticity.

Relationship between electrocardiographic RR and QT interval variabilities and indices of ventricular function in healthy subjects.

To date there has been no simultaneous characterization of the influence of physical exercise on cardiac ventricular function and cardiac electrical variability. Consequently, little is known about the relationship between the ventricular function and either heart rate (RR) or repolarization (QT) variability. In particular, the relationship between the QT variability index (QTVI) and ventricular function would be of clinical interest. Eight males of similar age (20.7 +/- 0.4 years (mean +/- SD)), mass (78.4 +/- 7.7 kg) and aerobic fitness (50.7 +/- 4.9 ml kg(-1) min(-1)) undertook progressive bicycle exercise. A three-lead Holter ECG was recorded continuously during pre-exercise, exercise and recovery, and mean values of RR and QT, their variabilities (RMSSD and SDNN) and their relative variability (QTVI) were determined. Traditional indices of ventricular function were determined beat to beat via impedance cardiography, and beat-to-beat blood pressure was recorded via photoplethysmography. Multiple linear regression analysis using the stepwise method resulted in significant models for each of the dependent variables (RR, QT, RR and QT variabilities, QTVI), using indices of the ventricular function as predictor variables. Notably, the QTVI reflected both the stroke volume index (SVI) and the acceleration index (ACI), which are measures of cardiac 'output' per contraction and the force of contraction, respectively. This relationship was largely unperturbed by physical exercise, in contrast with the results for all other dependent variables. We conclude that the QTVI is a reasonably consistent measure of the cardiac ventricular function, and as such is a more useful index than other parameters based on RR or QT interval alone.

Minimal distensibility of pulmonary capillaries in avian lungs compared with mammalian lungs.

Previous physiological studies suggest that avian pulmonary capillaries behave like almost rigid tubes. We made morphometric measurements to determine the diameter of the capillaries in chicken lungs when the transmural pressure was altered over a wide range. The diameter of avian pulmonary capillaries increased by only 13% when the pressure inside them was raised from 0 to 25 cmH(2)O. In contrast, other studies have shown that the mean width of the pulmonary capillaries in dogs increased by about 125% and in cats by 128% for the same pressure change. Furthermore, raising the pressure 35 cmH(2)O outside the capillaries compared to the pressure inside the capillaries in chicken lungs caused little change in diameter whereas under the same conditions in mammal lungs the capillaries are completely collapsed. We conclude that the epithelial bridges between the blood capillaries in the bird lung provide strong support to the capillaries both in expansion and compression.

Resistance and pulsatility index increase in capsular branches of testicular artery: indicator of impaired testicular microcirculation in varicocele?

PURPOSE: To evaluate the effect of clinical varicocele on testicular microcirculation using spectral Doppler analysis. METHODS: Forty-nine young and healthy volunteers were enrolled in this prospective study. Varicocele grades were determined according to sonographic parameters. Patients with left-sided clinical varicocele were classified as the patient group (n = 15), while the remaining patients served as controls (n = 34). Spectral Doppler measurements of testicular arteries (peak systolic/end diastolic velocity, resistance index, pulsatility index) were measured from capsular and intratesticular branches. RESULTS: No statistically significant difference was found between the Doppler parameters obtained from the intratesticular branches of both testes and the capsular branches of the right testis. On the other hand, in left-sided clinical varicocele cases, the average resistance index (RI) and pulsatility index (PI) of capsular branches of the left testes (RI, 0.68 +/- 0.04; PI, 1.22 +/- 0.15) were significantly greater than in the control group (RI, 0.64 +/- 0.06; PI, 1.07 +/- 0.18) (p < 0.05 and p < 0.01, respectively). CONCLUSIONS: Increased RI and PI of capsular branches of testicular arteries on spectral Doppler examination may be an indicator of impaired testicular microcirculation in patients with clinical varicocele. Further studies addressing the correlations with sperm counts are needed to determine the cut-off values for these indices.