Peripheral Blood Volume Research Articles

Postural hypocapnic hyperventilation is associated with enhanced peripheral vasoconstriction in postural tachycardia syndrome with normal supine blood flow.

Previous investigations have demonstrated a subset of postural tachycardia syndrome (POTS) patients characterized by normal peripheral resistance and blood volume while supine but thoracic hypovolemia and splanchnic blood pooling while upright secondary to splanchnic hyperemia. Such "normal-flow" POTS patients often demonstrate hypocapnia during orthostatic stress. We studied 20 POTS patients (14-23 yr of age) and compared them with 10 comparably aged healthy volunteers. We measured changes in heart rate, blood pressure, heart rate and blood pressure variability, arm and leg strain-gauge occlusion plethysmography, respiratory impedance plethysmography calibrated against pneumotachography, end-tidal partial pressure of carbon dioxide (Pet(CO2)), and impedance plethysmographic indexes of blood volume and blood flow within the thoracic, splanchnic, pelvic (upper leg), and lower leg regional circulations while supine and during upright tilt to 70 degrees. Ten POTS patients demonstrated significant hyperventilation and hypocapnia (POTS(HC)) while 10 were normocapnic with minimal increase in postural ventilation, comparable to control. While relative splanchnic hypervolemia and hyperemia occurred in both POTS groups compared with controls, marked enhancement in peripheral vasoconstriction occurred only in POTS(HC) and was related to thoracic blood flow. Variability indexes suggested enhanced sympathetic activation in POTS(HC) compared with other subjects. The data suggest enhanced cardiac and peripheral sympathetic excitation in POTS(HC).

Persistent splanchnic hyperemia during upright tilt in postural tachycardia syndrome

Previous investigations have allowed for stratification of patients with postural tachycardia syndrome (POTS) on the basis of peripheral blood flow. One such subset, comprising "normal-flow POTS" patients, is characterized by normal peripheral resistance and blood volume in the supine position but thoracic hypovolemia and splanchnic blood pooling in the upright position. We studied 32 consecutive 14- to 22-yr-old POTS patients comprising 13 with low-flow POTS, 14 with normal-flow POTS, and 5 with high-flow POTS and 12 comparably aged healthy volunteers. We measured changes in impedance plethysmographic (IPG) indexes of blood volume and blood flow within thoracic, splanchnic, pelvic (upper leg), and lower leg regional circulations in the supine posture and during incremental tilt to 20 degrees, 35 degrees, and 70 degrees. We validated IPG measures of thoracic and splanchnic blood flow against indocyanine green dye-dilution measurements. We validated IPG leg blood flow against venous occlusion plethysmography. Control subjects developed progressive vasoconstriction with incremental tilt. Splanchnic blood flow was increased in the supine position in normal-flow POTS, despite marked peripheral vasoconstriction, and did not change during incremental tilt, producing progressive splanchnic hypervolemia. Absolute hypovolemia was present in low-flow POTS, all supine flows and volumes were reduced, there was no vasoconstriction with tilt in all segments, and segmental volumes tended to increase uniformly throughout tilt. Lower body (pelvic and leg) flows were increased in high-flow POTS at all angles, with consequent lower body hypervolemia during tilt. Our main finding is selective and maintained orthostatic splanchnic vasodilation in normal-flow POTS, despite marked peripheral vasoconstriction in these same patients. Local splanchnic vasoregulatory factors may counteract vasoconstriction and venoconstriction in these patients. Lower body vasoconstriction in high-flow POTS was abnormal, and vasoconstriction in low-flow POTS was sustained at initially elevated supine levels.

Quantification of fetal nucleated cells in maternal blood of pregnant women with a male trisomy 21 fetus using molecular cytogenetic techniques

Prenatal diagnosis of trisomy 21 is based on fetal karyotyping generally obtained using invasive methods. During pregnancy, the circulating fetal cells in maternal blood constitute a potential source for development of a noninvasive prenatal diagnosis. The objective of this study was the identification and quantification of all fetal nucleated cells per unit volume of peripheral blood of pregnant women carrying male fetuses with trisomy 21 using molecular cytogenetic techniques. Peripheral blood samples were obtained from 16 women carrying male fetuses with trisomy 21. We used a simple and rapid method of harvesting blood without recourse to any enrichment procedures or cell-separation techniques. To evaluate the potential of this method, 16 specimens were analyzed by molecular cytogenetic techniques such as fluorescence in situ hybridization (FISH) and primed in situ labeling (PRINS) using specific probes to chromosomes X, Y and 21. The number of fetal cells varied between 6 and 32 per mL of maternal blood. This number is 3-5 times higher than that from normal pregnancies. Our current results are in agreement with the results previously reported by other groups showing that the number of fetal cells in maternal blood in trisomic 21 pregnancies is higher than in normal pregnancies. This high number of fetal cells is regarded as an advantage for the development of a noninvasive prenatal diagnostic test.

Pulse Pressure Determinants in Chronic Hemodialysis Patients

Cardiovascular disease is the leading cause of morbidity and mortality in end-stage renal disease. Hypertension contributes to the high cardiovascular morbidity in patients undergoing chronic hemodialysis therapy (PCHD). Optimal blood pressure (BP) in dialysis patients is not different from recommendations for the general population. The definition of hypertension in patients undergoing chronic hemodialysis therapy is still under debate. Predialysis systolic and diastolic BP is of particular importance. The mean arterial pressure (MAP) also serves as an expression of BP in hemodialysis patients, instead of systolic or diastolic BP. Investigations in the general population have demonstrated the predictive utility of pulse pressure (systolic minus diastolic blood pressure), a measure reflecting the pulsatile nature of the cardiac cycle. Recent recognition of pulse pressure (PP) as an important correlate of mortality in patients receiving dialysis highlights the need to investigate the relationship between PP and clinical outcomes in patients with end-stage renal disease. We conducted this study to demonstrate clinical and biochemical determinants of predialysis and postdialysis PP values during a 15-month period in a group of patients undergoing chronic hemodialysis therapy.

Central, peripheral, and other blood volume changes during hemodialysis.

Volume overload is a factor in development of hypertension in hemodialysis patients. Fluid removal by hemodialysis (HD), however, may cause intradialytic hypotension and associated symptoms. A better understanding of the relationships between blood pressure volume status and the pathophysiology of fluid removal during HD are, therefore, necessary to control blood pressure and to eliminate intradialytic hypotension. The objectives of the study were to determine the amount and direction of change of body fluid compartments after ultrafiltration (UF) and to determine whether any correlations exist between mean arterial pressure (MAP), change in circulating blood volume (deltaBV), total body water (TBW), central blood volume (which constitutes the volume of blood in the lungs, heart, and great vessels [CBV]), and intracellular and extracellular fluid volumes (ICF, ECF). The study population included 20 patients on regular HD. Each individual had their CBV, cardiac output, and peripheral vascular resistance (PVR) measured by means of saline dilution technique and deltaBV monitored by an online hematocrit sensor (Crit Line). MAP was calculated from measured blood pressure and ICF and ECF were measured using bioelectric impedance analysis techniques. Measurements were obtained before and after maximum UF measured by deltaBV (reduction of 6-10% by Crit Line). Ten healthy controls also had ECF and ICF values measured by bioelectric impedance analysis. Before HD, MAP correlated with TBW (r = 0.473, p = 0.035) and CBV (r = 0.419, p = 0.066), suggesting that hypertension here may be due to volume overload. Patients were ECF expanded before HD with an ECF:ICF ratio of 0.96, which was significantly higher than the control ratio of 0.74 (p < 0.0001). During UF, fluid was removed from both ECF and ICF, but more from the ECF volume ratio 0.92 post UF, a significant reduction (p < 0.0001). After UF, MAP no longer correlated with TBW or CBV but correlated with peripheral vascular resistance (r = 0.4575, p = 0.043). After UF, deltaBV correlated inversely with PVR (r = -0.50, p = 0.024). Despite the fall in deltaBV (7.11+/-2.49%) with UF, CBV was maintained. CBV were 0.899 L and 0.967 L pre and post UF, respectively. These data suggest that in hemodialysis patients, predialysis volume status influences predialysis blood pressure. UF causes BV to fall, but CBV is preferentially conserved by increasing PVR, which also maintains blood pressure. Failure of a PVR response likely leads to intradialytic hypotension.

Blood-sample processing for the study of age-dependent gene expression in peripheral blood mononuclear cells.

Although most new biogerontological studies seeking to identify longevity candidate genes and factors involved in successful human aging are population based, and likely to involve the collection of blood from extremely old individuals, to our knowledge no unified protocols have yet been published to describe a methodology permitting the simultaneous generation of different kinds of biological specimens derived from a single source of a very small volume of peripheral blood. Here we describe a method permitting the simultaneous generation of plasma, RNA, DNA, protein, fixed lymphocytes, and frozen blood aliquots from a single 10- to 30-ml blood sample obtained from donors of any age (10-102 years old), and we show that the quality and quantity of DNA, RNA, protein, and fixed lymphocytes obtained do not vary significantly with age. As is frequently observed, the older individuals have higher plasma proportions.

Objective emotional assessment of tactile hair properties and their modulation by different product worlds

Tactile properties of cosmetic products constitute weak stimuli and thus can be expected to be easily modified by mental images. In order to enhance an intended positive-emotion-inducing effect of such a product, its experience can be embedded in a certain 'world' that generates a positive emotional imagination. The present study investigated such an influence in 12 males and 12 females, half of each being laymen and experts in sensory assessment. Two product worlds (emotional and technical) and three different hair samples, two of them treated with different shampoos and an untreated one as control, were presented to each subject in counter-balanced order of all six combinations. An objective emotional assessment using a psychophysiological technique developed in an earlier study was applied and compared with a traditional sensory assessment. Among the physiological measures, peripheral blood volume and facial muscular activity were the most sensitive in revealing effects of and interactions between the product worlds and hair samples. A multivariate evaluation of the physiological data revealed three discriminant functions that explained 78.4% of the total variance and enabled a re-classification considerably better than chance. The first discriminant function clearly separated the treated from the untreated hair samples which was not possible by subjective ratings or traditional sensory assessment. The two other discriminant functions comprised a hedonistic and a product world factor. The emotional product world exerted the largest influence in case of the weakest tactile differences between the hair samples, and its influence was larger on laymen than on experts. Gender effects were most prominent in the subjective domain. In conclusion, multivariate psychophysiological methodology is superior to traditional sensory assessment in revealing subtle differences in the tactile perception of cosmetic products.

Analysis of IgE heavy chain sequences from a small volume of peripheral blood from a mildly atopic individual

Analysis of IgE heavy chain sequences from a small volume of peripheral blood from a mildly atopic individual

Calcium supplement increase on the second day of sequential two day leukapheresis.

Peripheral blood progenitor cells are collected effectively by leukapheresis of a large volume of peripheral blood. However, protection must be taken for patients or donors from hypocalcemia due to continuous infusion of citric acid. We found a tendency for hypocalcemic symptoms in patients or donors to occur more often on the second day than the first day of the sequential 2 days of leukapheresis. The doses of calcium gluconate supplement and the acid citrate dextrose-A solution administration significantly increased on the second day compared to that of the first day. The blood levels of c-terminal parathormone (PTH), phosphorus, and alkaline phosphatase did not show remarkably abnormal change. However, urine calcium excretion just after leukapheresis was higher than in the period before or after leukapheresis compared to the phosphorus or creatinine excretion. These findings indicate that the cause of a higher tendency to hypocalcemic symptoms on the second day of the sequential 2 days of leukapheresis is due to the higher metabolism of calcium being excreted in the urine during leukapheresis.

Uptake and killing ofListeria monocytogenesby normal human peripheral blood granulocytes and monocytes as measured by flow cytometry and cell sorting

Cellular components of innate immunity (NK cells, monocytes and granulocytes) play an important role in early resistance to Listeria monocytogenes in the mouse model. Minimally invasive methods of measuring the bacteriocidal capacity of these cells may be useful as a biomarker of susceptibility in humans. A technique was developed whereby the uptake and survival of L. monocytogenes could be measured in human granulocytes and monocytes using small volumes of peripheral blood. This method used flow cytometry to detect the presence of PKH-2-labeled bacteria within these cells. Survival of bacteria was determined by sorting of infected cells based on a combination of fluorescence and light scattering properties. Considerable variation in bacterial recovery was seen between normal volunteers. There was consistently greater survival of a fully virulent strain of L. monocytogenes within monocytes and granulocytes compared with an isogenic strain lacking the hemolysin, listeriolysin O, when measured at baseline. There was no evidence of longer-term bacterial survival or growth at 2 or 24 h. This technique may be useful for assessment of both host resistance and pathogen virulence.

Uptake and killing of Listeria monocytogenes by normal human peripheral blood granulocytes and monocytes as measured by flow cytometry and cell sorting

Cellular components of innate immunity (NK cells, monocytes and granulocytes) play an important role in early resistance to Listeria monocytogenes in the mouse model. Minimally invasive methods of measuring the bacteriocidal capacity of these cells may be useful as a biomarker of susceptibility in humans. A technique was developed whereby the uptake and survival of L. monocytogenes could be measured in human granulocytes and monocytes using small volumes of peripheral blood. This method used flow cytometry to detect the presence of PKH-2-labeled bacteria within these cells. Survival of bacteria was determined by sorting of infected cells based on a combination of fluorescence and light scattering properties. Considerable variation in bacterial recovery was seen between normal volunteers. There was consistently greater survival of a fully virulent strain of L. monocytogenes within monocytes and granulocytes compared with an isogenic strain lacking the hemolysin, listeriolysin O, when measured at baseline. There was no evidence of longer-term bacterial survival or growth at 2 or 24 h. This technique may be useful for assessment of both host resistance and pathogen virulence.

Quantification of all fetal nucleated cells in maternal blood between the 18th and 22nd weeks of pregnancy using molecular cytogenetic techniques.

Different types of nucleated fetal cells (trophoblasts, erythroblasts, lymphocytes, and granulocytes) have been recovered in maternal peripheral blood. In spite of many attempts to estimate the number of fetal cells in maternal circulation, there is still much controversy concerning this aspect. The numbers obtained vary widely, ranging from 1 nucleated cell per 104 to 1 per 109 nucleated maternal cells. The purpose of our project was to determine the absolute number of all different types of male fetal nucleated cells per unit volume of peripheral maternal blood. Peripheral blood samples were obtained from 12 normal pregnant women known to carry a male fetus between 18 and 22 weeks of pregnancy. Three milliliters (3 ml) of maternal blood has been processed without any enrichment procedures. Fluorescence in situ hybridization (FISH) and primed in situ labeling (PRINS) were performed, and fetal XY cells were identified (among maternal XX cells) and scored by fluorescent microscopy screening. The total number of male fetal nucleated cells per milliliter of maternal blood was consistent in each woman studied and varied from 2 to 6 cells per milliliter within the group of normal pregnancies. The number of fetal cells in maternal blood, at a given period, is reproducible and can therefore be assessed by cytogenetic methods. This confirms the possibility of developing a non-invasive prenatal diagnosis test for aneuploidies. Furthermore, we demonstrate that it is possible to repeatedly identify an extremely small number of fetal cells among millions of maternal cells.

Erythrocyte transfusion: friend or foe?

M ORE than 13 million units of red blood cells (RBC) are collected in the United States and over 1 1 million units are transfused to 3.4 million patients annually. It is estimated that 60 70% of these RBC units are transfused in the perioperative period. Such considerable numbers are in sharp contrast with the little knowledge we have on the true benefits of ery throcyte transfusions. In this refresher course lecture, we will discuss the risks of anemia and the benefits of RBC transfusions in the perioperative context. For a more detailed and formal review of the literature, the reader is referred to a recently published text by the same authors. 1 Conceptually, the risk/benefit ratio of erythrocyte transfusions must take three factors into account: 1) the risks secondary to anemia which depend, in turn, on the patient's capacity to compensate for it; 2) the capacity of allogeneic RBC to correct these risks, a consideration which is all too often assumed but has not been well demonstrated; 3) the risks of transfusions themselves. While the infectious risks of blood products, specially HIV, have brought about a major reconsideration of the way we should be administering transfusions, the risks associated with the immunomodulating effects of blood products, as well as the "classic" complications (volume overload, ABO incompatibility, etc.) of RBC transfusions should be kept in mind. Given the inherent complexity of this risk/benefit analysis, it becomes rapidly apparent that any attempt to define a universal "transfusion trigger" is overly simplistic and unrealistic from a scientific standpoint. The analogy with a "fever trigger" illustrates why the attempt to define a "transfusion trigger" is doomed to fail clinically. Attempting to define a "fever trigger", i.e., the fixed body temperature above which penicillin should be administered would, nowadays, be consid ered absurd. Yet, this is the approach adopted by sever al when transfusing RBC. Erythrocytes (penicillin) are administered for anemia (fever) without knowing if the underlying disease will respond to the elected therapeu tic approach. Adopting a universal "fever trigger" would certainly cure a few individuals, but would need lessly expose a considerable number of patients to peni cillin and result in a significant number of untoward events, allergic or other. Erythrocyte transfusions: the arguments In contrast with the paucity of objective data on the risks of anemia or the benefits of RBC transfusions, several arguments have been put forward either to support or to condone erythrocyte transfusions in the perioperative period. RaHonale in favour of IP~BC transfusions to maintain a high hemoglobin concentvaHon Classically, several arguments have supported the use of RBC transfusions to maintain a high hemoglobin concentration ([Hb]" above 100 g.L 1). • Transfusions are thought to be safer than ever. While this is true in part, the growing concern in Europe with new variant Creutzfeldt Jakob disease illustrates how fragile the situation really is. 2 • Increased 0 2 delivery may improve survival in the intensive care setting. Yet, it remains unclear if the best way to achieve increased 02 delivery is by increasing cardiac output or by increasing [Hb]. • Patients with cardiovascular disease may not be able to compensate for anemia and a high [Hb] will decrease the risk of morbidity and mortality. • Similarly, advanced age, disease and drugs will diminish the adaptation to anemia and a high [Hb] will decrease the risk of morbidity and mortality. • A high [Hb] is required for optimal hemostasis. The contribution of RBC to coagulation is impor tant and all too often overlooked. • A high [Hb] will restore peripheral blood volume and decrease the risks associated with under perfu sion of the gastrointestinal tract. • A high [Hb] will improve the margin of safety, should further bleeding occur. • Finally, a high [Hb] is associated with improved From the Departments of Anesthesiology, Centre Hospitalier de l'Universit6 de Montr6al and Institut de CaJdiologie de Montr6al, Universit6 de Montr6al, Montreal, Quebec, Canada. Address correspondence to'. Dr. Jean Francois Hardy, CHUM HOtel Dieu de Montreal, Pavillon de Bouillon, local 6 521, 3840 me St Urbain, Montreal, Quebec, Canada H2W 1T8. Phone: 514 8908000, ext. 15578; Fax: 514 412 7143; E mail: jean francois.hardy@umontreal.ca CAN J ANESTH 2001 / 48:6 / pp R1 R7

Modelling the relationship between peripheral blood pressure and blood volume pulses using linear and neural network system identification techniques

The relationships between peripheral blood pressure and blood volume pulse waveforms can provide valuable physiological data about the peripheral vascular system, and are the subject of this study. Blood pressure and volume pulse waveforms were collected from 12 normal male subjects using non-invasive optical techniques, finger arterial blood pressure (BP, Finapres: Datex-Ohmeda) and photoelectric plethysmography (PPG) respectively, and captured to computer for three equal (1 min) measurement phases: baseline, hand raising and hand elevated. This simple physiological challenge was designed to induce a significant drop in peripheral blood pressure. A simple first order lag transfer function was chosen to study the relationship between blood pressure (system input) and blood volume pulse waveforms (system output), with parameters describing the dynamics (time constant, ) and input-output gain (K). and K were estimated for each subject using two different system identification techniques: a recursive parameter estimation algorithm which calculated and K from a linear auto-regressive with exogenous variable (ARX) model, and an artificial neural network which was trained to learn the non-linear process input-output relationships and then derive a linearized ARX model of the system. The identification techniques allowed the relationship between the blood pressure and blood volume pulses to be described simply, with the neural network technique providing a better model fit overall (p<0.05, Wilcoxon). The median falls in following the hand raise challenge were 26% and 31% for the linear and neural network based techniques respectively (both p<0.05, Wilcoxon). This preliminary study has shown that the time constant and gain parameters obtained using these techniques can provide physiological data for the clinical assessment of the peripheral circulation.

Molecular analysis of highly enriched populations of T-cell-depleted monocytes

CD4+ T lymphocytes and monocytes/macrophages are important components of the immune system. Blood monocytes are usually targeted for studies of the human macrophage lineage cells because of their accessibility through blood sampling. Most separation techniques currently available to obtain human monocytes either require large volumes of blood or do not yield a monocyte fraction sufficiently depleted of other cell types. We have developed a simple strategy to isolate a highly enriched population of monocytes from small volumes (< 6 ml) of peripheral blood by using an anti-CD14 monoclonal antibody and magnetic microspheres. Yields of monocytes ranged from 75 to 80% of CD14+ cells in peripheral blood. CD4+ T cells were subsequently selected from the monocyte-depleted peripheral blood by using an anti-CD4 monoclonal antibody and immunomagnetic beads. The effectiveness of immunomagnetic selection to yield a monocyte population highly depleted of T cells was analyzed by using a sensitive molecular strategy based on PCR amplification and detection of T-cell receptor (TCR) gene rearrangements. The relative frequency of rearranged TCRs within the monocyte population was compared with the frequency of rearranged TCRs within the CD4+ T-cell fraction from the same individual. Molecular analysis indicated that a viable monocyte population which contains fewer than 2% residual T lymphocytes can be consistently selected from small aliquots of blood.

The role of body fluid volume and osmolality in thermoregulation and cardiovascular adjustment

Body temperature regulation at rest in a hot environment and/or during exercise requires marked increases in skin blood flow (BF). This is achieved by increasing cardiac output and redistributing BF away from splanchuic, renal, fat and non-exercising muscle tissues, so there is a balance between competing demands for regulation of blood pressure and body temperature. As the heat load increases, central venous pressure (CVP) decreases due to reduced central blood volume brought about by the above increase in peripheral blood volume and by reduced total blood volume due to sweat loss. Skin BF becomes sub-maximal, purportedly due to the falling CVP acting via low-pressure baroreceptors in a feed-forward manner to minimise changes in arterial pressure. That is, the thermoregulatory demands become so great that disturbance of cardiovascular function becomes intolerable. Therefore, there is a conflict in which cardiovascular control ultimately dominates body temperature control to the extent that the rising core temperature is aggravated by reductions in sweating and in skin BF and volume. An important role may also be played by endotoxaemia due to the high temperature and low gastrointestinal BF allowing increased quantities of lipepolysaccharide to cross from the gastrointestinal lumen; this could act as in fever to inhibit heat loss and increase heat production. 'Collapse' occurs due to CNS or other secondary non-cardiovascular effects of the severe hyperthermia etythrocyte sphering and disseminated intravascular coagulation result in microthrombosns and coagulative necrosis in nervous and other tissues, leading to death. The concept of an adjustable critical thermal maximum may explain the apparent association of 'physiological failure' with widely varying levels of body temperature during severe heat stress.

Conjunctival oxygen tension is influenced by plasma and blood volume, and flow through the external carotid artery

An investigation of the feasibility and validity of measurement of the conjunctival oxygen tension as a monitor of peripheral circulation, blood and extracellular fluid volume and cerebral circulation was carried out in 7 healthy volunteers and 5 unconscious critical care patients with proven total cerebral infarction. The healthy volunteers were subjected to changes in hydration achieved by the administration of furosemide and subsequent rehydration by administration of normal saline. Conjunctival oxygen tension was found to be a sensitive indicator of changes in the degree of hydration presumably by its ability to detect changes in peripheral circulation depending upon circulating blood and extracellular fluid volume. A drawback is that other stimuli of the sympatho-adrenergic system such as temperature and pain, interfere with measurement in the conscious volunteer. In patients with presumed total brain infarction the conjunctival PO2 cannot be used as a reliable monitor of cerebral blood flow because of varying perfusion of the palpebral conjunctiva from the external carotid artery in the occasional patient.

脳動脈瘤クリップ時における末梢側動脈の継続的血流速モニターの有用性

脳動脈瘤クリップ時における末梢側動脈の継続的血流速モニターの有用性

Tissue gas stores of the body and head-out immersion in humans

Breath-by-breath gas exchange was studied in 10 subjects during and after transitions between dry conditions and head-out immersion in thermoneutral conditions. Cardiac index (CI) was estimated by means of impedance cardiography. Previous largely qualitative models of changes in tissue gas stores after blood volume shifts could be confirmed and extended to include a quantitative analysis of O2 and CO2 tissue stores. An increase in CI by 47.0% during immersion was associated with an increase in the tissue O2 stores by 122 ml/m2 and a decrease in the tissue CO2 stores by 148 ml/m2. The time constants for the recovery of O2 uptake (tau O2) and CO2 elimination after initial increases after the dry-to-immersion transition were 32.4 and 79.3 s, respectively. The decrease in CI on return to the dry conditions was associated with a drop in tissue O2 stores and a tau O2 of 144 s. The increase in tissue O2 stores during immersion as well as the difference in tau O2 between the two transitions were larger than could be explained by the change in CI only. This was attributed to changes in the distributions of peripheral blood flow and venous blood volume. Compared with the O2 stores, the decrease in CO2 stores was better predicted by the change in CI. The present results emphasize that the changes in pulmonary and tissue gas exchange imposed by head-out immersion transients mainly reflect movement of gas in and out of body stores.

The Method of Lymphocyte Transformation Test with Small Volume of Peripheral Blood in Serum-Free Medium

The Method of Lymphocyte Transformation Test with Small Volume of Peripheral Blood in Serum-Free Medium