Cerebral oxygenation responses to standing in elderly patients with predominantly diastolic dysfunction

Patients with left ventricular dysfunction may have different orthostatic responses of blood pressure (BP) and cerebral oxygenation than healthy elderly subjects. We investigated orthostatic changes in systemic haemodynamic variables and cerebral oxygenation in 21 elderly patients with heart failure New York Heart Association class I-III in stable condition (age 70-83 years) after withdrawal of furosemide and captopril for 2 weeks, and in 18 healthy elderly subjects (age 70-84 years). Frontal cortical concentration changes of oxyhaemoglobin ([O2Hb]) and deoxyhaemoglobin ([HHb]) were continuously measured by near-infrared spectrophotometry and BP changes by Finapres before and during 10 min of standing. Upon standing [O2Hb] reflecting blood flow, changed by -1.2 +/- 0.9 micromol L-1 (mean +/- SEM) in the patients, whereas it decreased by -4.5 +/- 0.6 micromol L-1 (P<0.01) in the healthy subjects after standing (P<0.05 between groups). [HHb] reflecting the sum of cerebral blood flow, arterial oxygen saturation and cerebral oxygen uptake, increased by 1.5 +/- 0.5 micromol L-1 (P<0.05) and 1.7 +/- 0.6 micromol L-1 (P<0.05), respectively. Compared with healthy elderly subjects, elderly patients with left ventricular dysfunction showed smaller orthostatic [O2Hb] decreases (P<0.01), in relation to higher orthostatic BP rises (P<0.05). These findings indicate that BP changes and an altered cardiovascular balance may influence orthostatic cortical haemodynamic responses in elderly subjects.     

Altered balance in the autonomic nervous system in schizophrenic patients

Summary. The aim of the present study was to evaluate the autonomic nervous function in schizophrenic patients. Twenty-eight patients (29 ± 6 years) diagnosed as schizophrenics and in stable medication were included, together with ten schizophrenic patients (25 ± 5 years) who were unmedicated. Eleven healthy subjects (32 ± 7 years) served as controls. Immediate heart-rate responses to a single deep inspiration was used as a measure of parasympathetic function. Heart-rate response to standing was used as a measure of sympathetic function. Supine blood pressure, heart-rate and orthostatic changes in blood pressure did not differ between groups. Heart-rate response to standing was greater in both medicated and non-medicated schizophrenics compared to normal subjects (P<0·01). Heart-rate response to standing was greater in non-medicated compared to medicated schizophrenics (P<0·05). Heart-rate response to inspiration was greater in non-medicated schizophrenics compared to normal subjects (P<0·05), whereas no difference was found between medicated and non-medicated schizophrenics. The results show that the balance in the autonomic nervous system is altered in schizophrenic patients with a hyperexcitability in both the sympathetic and the parasympathetic division. Our study has thus indicated a dysfunction in the autonomic nervous system per se and the previous interpretations of attentional orienting responses in schizophrenia is questioned. Medication with neuroleptics seems to partly normalize the autonomic reactivity rather than being the cause of autonomic dysfunction.     

Influence of skin blood flow and source‐detector distance on near‐infrared spectroscopy‐determined cerebral oxygenation in humans

Most near‐infrared spectroscopy (NIRS) apparatus fails to isolate cerebral oxygenation from an extracranial contribution although they use different source‐detector distances. Nevertheless, the effect of different source‐detector distances and change in extracranial blood flow on the NIRS signal has not been identified in humans. This study evaluated the extracranial contribution, as indicated by forehead skin blood flow (SkBF) to changes in the NIRS‐determined cerebral oxyhaemoglobin concentration (O₂Hb) by use of a custom‐made multidistance probe. Seven males (age 21 ± 1 year) were in a semi‐recumbent position, while extracranial blood flow was restricted by application of four different pressures (+20 to +80 mmHg) to the left temporal artery. The O₂Hb was measured at the forehead via a multidistance probe (source‐detector distance; 15, 22·5 and 30 mm), and SkBF was determined by laser Doppler. Heart rate and blood pressure were unaffected by application of pressure to the temporal artery, while SkBF gradually decreased (P<0·001), indicating that extracranial blood flow was manipulated without haemodynamic changes. Also, O₂Hb gradually decreased with increasing applied pressure (P<0·05), and the decrease was related to that in SkBF (r = 0·737, P<0·01) independent of the NIRS source to detector distance. These findings suggest that the NIRS‐determined cerebral oxyhaemoglobin is affected by change in extracranial blood flow independent of the source‐detector distance from 15 to 30 mm. Therefore, new algorithms need to be developed for unbiased NIRS detection of cerebral oxygenation.     

The age‐related reduction in cerebral blood flow affects vertebral artery more than internal carotid artery blood flow

Ageing reduces cerebral blood flow (CBF), while mean arterial pressure (MAP) becomes elevated. According to ‘the selfish brain’ hypothesis of hypertension, a reduction in vertebral artery blood flow (VA) leads to increased sympathetic activity and thus increases MAP. In twenty‐two young (24 ± 3 years; mean ± SD) and eleven elderly (70 ± 5 years) normotensive men, duplex ultrasound evaluated whether the age‐related reduction in CBF affects VA more than internal carotid artery (ICA) blood flow. Pulse‐contour analysis evaluated MAP while near‐infrared spectroscopy determined frontal lobe oxygenation and transcranial Doppler middle cerebral artery mean blood velocity (MCA V_mean). During supine rest, MAP (90 ± 13 versus 78 ± 9 mmHg; P<0·001) was elevated in the older subjects while their frontal lobe oxygenation (68 ± 7% versus 77 ± 7%; P<0·001), MCA V_mean (49 ± 9 versus 60 ± 12 cm s^?1; P = 0·016) and CBF (754 ± 112 versus 900 ± 144 ml min^?1; P = 0·004) were low reflected in VA (138 ± 48 versus 219 ± 50 ml min^?1; P<0·001) rather than in ICA flow (616 ± 96 versus 680 ± 120 ml min^?1; P = 0·099). In conclusion, blood supply to the brain and its oxygenation are affected by ageing and the age‐related decline in VA flow appears to be four times as large as that in ICA and could be important for the age‐related increase in MAP.     

Changes in cardiac autonomic regulation after prolonged maximal exercise

Harmful cardiac events occurs frequently after exercise. However, the cardiac autonomic regulation after vigorous exercise is not well known. This study was designed to assess heart rate (HR) variability before and after a 75 km cross‐country skiing race. HR variability was assessed by using standard statistical measures along with spectral and quantitative Poincarè plot analysis of HR variability in 10 healthy male subjects (age 36 ± 11 years). The average HR was at the same level 1 day after the race as before the race, but on the second day, HR was significantly lower (P<0·001) compared with the prerace and 1 day after values. The normalized high‐frequency (HF) spectral component of HR variability (nuHF) was lower (P<0·01) on the first day after the maximal exercise compared with the pre‐exercise values but returned to or even exceeded the prerace level on the second day (P<0·01). The changes in short‐term R‐R interval variability analysed from the Poincaré plot were similar to those observed in the HF spectral component. The normalized low‐frequency (LF) spectral component of HR variability (nuLF) was higher (P<0·01) on the first day after the exercise compared with the prerace levels and it also returned to the pre‐exercise level or even dropped below it on the second day after the race. The mean time it took the HF spectral component to return to the pre‐exercise level was 4·2 ± 4·2 h (ranging from 0 to 12 h). This recovery time correlated inversely with the maximal oxygen consumption (VO_2max) measured during the bicycle exercise test before the skiing race (r=?0·712, P<0·016). The cardiac vagal outflow is blunted for several hours after prolonged vigorous exercise. The recovery time of reduced vagal outflow depends on individual cardiorespiratory fitness and there is an accentuated rebound of altered autonomic regulation on the second day after prolonged exercise.     

Serum sialic acid changes in type 2 diabetic patients on metformin or rosiglitazone treatment

What is known and objective: Serum sialic acid is a recently investigated potential risk‐marker for cardiovascular complications. There is a known association between sialic acid and cardiovascular complications in diabetes mellitus. We aimed to investigate the effect of antidiabetic drugs on the serum concentration of sialic acid. Methods: We investigated the effect of metformin and rosiglitazone on the concentration of sialic acid in 120 type 2 diabetic patients, divided into a group (n = 60) receiving metformin and a group (n = 60) receiving rosiglitazone treatment. Results: Serum sialic acid was significantly higher in patients on rosiglitazone (66·90 ±8·80 mg/dL vs. 57·6 ± 8·46 mg/dL, P <0·01) and metformin (61·95 ± 10·49 mg/dL vs. 57·6 ±8·46mg/dL, P < 0·04) when compared with control subjects. In addition, rosiglitazone‐treated patients showed a significant increase in cardiovascular risk factors, notably total cholesterol (246·45 ± 20·2 mg/dL vs. 170·6 ± 15·1 mg/dL, P =0·01), triglyceride (178 ± 9·20 mg/dL vs. 149·35 ±6·31 mg/dL, P < 0·04) and glycohemoglobin (HbA1‐c) concentration (8·17 ± 1·43% vs. 4·38 ±0·96%, P < 0·02) compared with normal control subjects. The patients on metformin also showed significantly higher levels of serum glucose (133·7 ± 9·63 mg/dL vs. 88·35 ± 6·31 mg/dL, P <0·04) and glycohemoglobin (HbA1‐c) (8·23 ±1·75% vs. 4·38 ± 0·96%, P < 0·02) when compared with control subjects. Comparison of the two groups of patients revealed a significantly higher serum sialic acid (66·90 ± 8·80 mg/dL vs. 61·95 ±10·49 mg/dL, P < 0·05), total cholesterol (246·45 ±20·2 mg/dL vs. 192 ± 14·23 mg/dL, P <0·02) and triglyceride (178 ± 9·20 mg/dL vs. 158 ± 14·51mg/dL, P < 0·05) concentrations in the rosiglitazone‐treated patients. What is new and conclusions: This study suggests significantly higher levels of serum sialic acid and other cardiovascular risk factors in rosiglitazone‐treated patients than in metformin‐treated patients. The lower sialic acid concentration may explain a better metformin antidiabetic effect than with rosiglitazone.     

Functional near‐infrared spectroscopy to probe sensorimotor region activation during electrical stimulation‐evoked movement

This study used non‐invasive functional near‐infrared spectroscopy (fNIRS) neuroimaging to monitor bilateral sensorimotor region activation during unilateral voluntary (VOL) and neuromuscular electrical stimulation (NMES)‐evoked movements. Methods. In eight healthy male volunteers, fNIRS was used to measure relative changes in oxyhaemoglobin (O₂Hb) and deoxyhaemoglobin (HHb) concentrations from a cortical sensorimotor region of interest in the left (LH) and right (RH) hemispheres during NMES‐evoked and VOL wrist extension movements of the right arm. Results. NMES‐evoked movements induced significantly greater activation (increase in O₂Hb and concomitant decrease in HHb) in the contralateral LH than in the ipsilateral RH (O₂Hb: 0·44 ± 0·16 μM and 0·25 ± 0·22 μM, P = 0·017; HHb: ?0·19 ± 0·10 μM and ?0·12 ± 0·09 μM, P = 0·036, respectively) as did VOL movements (0·51 ± 0·24 μΜ and 0·34 ± 0·21 μM, P = 0·031; HHb: ?0·18 ± 0·07 μΜ and ?0·12 ± 0·04 μΜ, P = 0·05, respectively). There was no significant difference between conditions for O₂Hb (P = 0·144) and HHb (P = 0·958). Conclusion. fNIRS neuroimaging enables quantification of bilateral sensorimotor regional activation profiles during voluntary and NMES‐evoked wrist extension movements.     

Tissue oxygenation,strength and lactate response to different blood flow restrictive pressures

This study aimed to determine whether changes in initial restrictive pressures (IRP, tightness of the cuff before inflation with air) affect tissue oxygenation, lactate production and leg strength before, during and after knee extension exercises. The cuff was positioned on the right thigh, and the IRP of either 40–45 or 60–65 mmHg were applied randomly prior to inflating the cuff to the final restrictive pressure (the pressure reached after inflating the cuff with air). Subjects performed four sets (30, 15, 15 and 15 reps) of isotonic knee extensions with 1‐min rest between sets. Tissue oxygenation and blood lactate levels were assessed prior to, during and after exercise, and leg strength was assessed pre‐ and postexercise. There were significant condition by time interactions (P<0·01) and main effects for both condition (P<0·01) and time (P<0·01) for tissue oxygenation, deoxyhaemoglobin, total haemoglobin. Significant main effects were detected for both condition (P<0·01) and time (P<0·01) for leg strength values. There was only a significant time main effect for lactate concentrations. This study is the first to show that a higher IRP had a significant impact on percent tissue oxygenation, leg strength and deoxygenated haemoglobin accumulation during exercise.     

Differential effects of age on large artery stiffness and minimal vascular resistance in normotensive and mildly hypertensive individuals

Large artery stiffness and small artery structural changes are both cardiovascular risk factors. Arterial stiffness increases with age and blood pressure (BP), but it is unclear in which way large artery pulse wave velocity (PWV) and peripheral vascular resistance are related and whether age has any influence. In a cross‐sectional study, PWV and forearm minimum vascular resistance (R_min) was compared with emphasis on the impact of age. Normotensive (n = 53) and untreated hypertensive (n = 23) subjects were included based on 24‐h BP measurements. Age ranged from 21 to 79 years with an even distribution from each age decade. PWV was assessed using tonometry. Forearm R_min was measured by venous occlusion plethysmography at maximal vasodilatation induced by 10 min of ischaemia in combination with skin heating and hand grip exercise. In both normotensive and hypertensive subjects, PWV correlated significantly with age and BP. Based on median age, both groups were assigned into two equally large subgroups. Normotensive older (66 ± 7 years) and younger (35 ± 10 years) persons had different carotid‐femoral PWV (7·9 ± 1·8 versus 5·7 ± 0·9 m/s, P<0·01), but similar R_min values (3·7 ± 0·9 versus 3·6 ± 1·2 mmHg/ml/min/100 ml). Hypertensive older (63 ± 6 years) and younger (40 ± 10 years) also had different PWV (8·0 ± 1·5 versus 6·7 ± 1·1 m/s, P<0·05), but the older had lower R_min (3·1 ± 0·8 versus 4·7 ± 2·2 mmHg/ml/min/100 ml, P<0·05). In a regression analysis adjusting for age, BP, gender and heart rate, no correlation was seen between PWV and R_min. The data suggest that age differentially affects PWV and R_min and that BP can increase in older persons without affecting R_min.     

The effect of systemic blood pressure on cardio‐vascular reflexes in elderly subjects

The evidence for impairment of cardiovascular reflexes by hypertension in elderly subjects is mixed. This study tested the hypothesis that baroreceptor‐ and non‐baroreceptor‐mediated responses in elderly subjects differed with hypertension. 54 elderly subjects were studied: 16 with combined hypertension (CT) (blood pressure 184 ± 4/102 ± 2 mmHg), 16 with isolated systolic hypertension (180 ± 3/85 ± 1 mmHg) and 22 normotensives (NT) (138 ± 2/76 ± 1 mmHg). All subjects performed isometric exercise with a handgrip dynamometer. Heart rate (HR), blood pressure and forearm vascular resistance (FVR) responses were then studied to 60° head‐up tilt and the cold face stimulus. Baseline FVR, and the response to isometric handgrip, were similar in all groups. Subjects with isolated systolic hypertension manifested greater increases in FVR with tilt (P<0·001), whilst the HR increment was greater in the NT group (P<0·001). Blood pressure changes with tilt were similar in the three groups. With the cold face stimulus (CFS) a rise in FVR of approximately 30% was seen in all groups and blood pressure rose modestly, with the largest increases being seen in the combined hypertensives. This study in elderly subjects indicates significant differences with hypertension in the response to tilt, with an impaired baroreceptor‐cardiac reflex being compensated by an augmented baroreceptor‐vascular response.     

Temporal age‐related changes in spectral,fractal and complexity characteristics of heart rate variability

Cross‐sectional studies have suggested that heart rate (HR) variability, analysed using traditional time and frequency domain methods, is related to ageing, but no longitudinal studies have estimated the age dependence of HR fluctuation. This study evaluated temporal age‐related changes in 12‐h measures of HR variability among 109 patients with coronary artery disease (CAD), who underwent repeat Holter recordings at 32‐month intervals. Time and frequency domain measures, along with fractal and complexity measures of HR variability, were determined at the baseline and after 32 months. Changes in HR dynamics were compared with various laboratory variables, exercise data and angiographic progression of CAD. Traditional time and frequency domain measures of HR variability did not change significantly during the follow‐up, but the power‐law scaling slope decreased from ?1·29 ± 0·20 to ?1·36 ± 0·23 (P<0·01) and the short‐term fractal exponent (α₁) of HR dynamics from 1·29 ± 0·14–1·22 ± 0·18 (P<0·001). The approximate entropy value also decreased from 1·00 ± 0·19 to 0·95 ± 0·18 (P<0·05). The changes in HR behaviour were not related to demographic data, laboratory values or angiographic progression of CAD. Only a weak correlation was observed between the change in the power‐law slope and the baseline glucose value (P<0·05). This longitudinal study shows that the fractal characteristics of HR dynamics and the complexity properties of R‐R intervals undergo rapid changes along with ageing, and that fractal and complexity analysis techniques are more sensitive than traditional analysis methods in documenting temporal age‐related changes in HR behaviour.     

Office and laboratory blood pressures as predictors of daily blood pressure level in normotensive subjects and borderline and mild hypertensive subjects

A series of standardized laboratory tests [10 min sitting and supine, 9 min standing, dynamic; cycle ergometer (ERG) and isometric exercise; handgrip (HG)] were performed during intra-arterial blood pressure (BP) recording in 97 healthy unmedicated men, initially classified as normotensive (NT, n = 34), borderline hypertensive (BHT, n = 29) or mildly hypertensive (HT, n = 34) by repeated office blood pressure (OBP) measurements. After testing, a 24-h intra-arterial ambulatory BP (IABP) recording was obtained while subjects performed their normal activities. Day and night periods were analysed as well as 24-h averages for systolic BP (SBP) and diastolic BP (DBP) using Pearson correlations and multiple linear regressions. In normotensive subjects, the supine SBP predicted IABP measurements best (r range 0·39–0·69, P<0·05–0·001). In multiple regression, supine SBP explained 49% of 24-h SBP variance (F = 12·4, P = 0·001). For BHT, supine SBP was also the best predictor (r range 0·09–0·64, P NS to P<0·001), and it explained 37% of 24-h SBP variance (F = 15·6, P = 0·0005). In HT, ERG DBP correlated best with IABP (r range 0·52–0·75, P<0·01–0·001). ERG SBP explained 49% of 24-h SBP (F = 31·0, P = 0·0000) and ERG DBP explained 56% of 24-h DBP (F = 35·4, P = 0·0000) variance. Laboratory BP correlations were generally better with day than with night measurements. OSBP correlated moderately well with IABP in NT, and weakly in BHT and HT; ODBP instead correlated with IABP in NT and HT but not significantly in BHT. In conclusion, OBP is less closely related to IABP than laboratory BP, but even laboratory BP generally explains less than 50% of IABP variance. Stressors such as exercise are useful only in HT. For BHT, the prediction of IABP with laboratory measures was even weaker than in other groups, and thus ambulatory measurements cannot be replaced by short-duration laboratory measurements and stress tests.     

Whole‐body vibration dosage alters leg blood flow

The effect of whole‐body vibration dosage on leg blood flow was investigated. Nine healthy young adult males completed a set of 14 random vibration and non‐vibration exercise bouts whilst squatting on a Galileo 900 plate. Six vibration frequencies ranging from 5 to 30 Hz (5 Hz increments) were used in combination with a 2·5 mm and 4·5 mm amplitude to produce twelve 1‐min vibration bouts. Subjects also completed two 1‐min bouts where no vibration was applied. Systolic and diastolic diameters of the common femoral artery and blood cell velocity were measured by an echo Doppler ultrasound in a standing or rest condition prior to the bouts and during and after each bout. Repeated measures MANOVAs were used in the statistical analysis. Compared with the standing condition, the exercise bouts produced a four‐fold increase in mean blood cell velocity (P<0·001) and a two‐fold increase in peak blood cell velocity (P<0·001). Compared to the non‐vibration bouts, frequencies of 10–30 Hz increased mean blood cell velocity by approximately 33% (P<0·01) whereas 20–30 Hz increased peak blood cell velocity by approximately 27% (P<0·01). Amplitude was additive to frequency but only achieved significance at 30 Hz (P<0·05). Compared with the standing condition, squatting alone produced significant increases in mean and peak blood cell velocity (P<0·001). The results show leg blood flow increased during the squat or non‐vibration bouts and systematically increased with frequency in the vibration bouts.     

Decrease in myoglobin and enzyme contents with haemodilution in non-hypoxaemic polycythaemic patients

Summary. Quadriceps muscle biopsies from five patients with primary polycythaemia and four patients with non-primary polycythaemia, all with normal respiratory functions, were studied before and after normalization of haemoglobin and erythrocyte volume fraction by haemodilution or venaesectio. Since similar results were obtained from both groups of patients data were pooled. After normalization of the erythrocyte volume fraction myoglobin decreased by 19 ± 16%, P<0·01, the activity of creatine kinase and citrate synthase by 12 ± 8 and 14 ± 18%, P<0·05, respectively. The decrease in myoglobin content was related to the decrease in haemoglobin concentration (r= 0·77, P<0·01). In conclusion, these data suggest that in non-hypoxaemic polycythaemia skeletal muscle shows adaptations indicative of an impaired oxygenation and a metabolic stress, adaptations that are reversed by haemodilution.     

Volumetric measurements of peripheral oedema in clinical conditions

Water‐displacement volumetry can be used for quantifying the volume of the leg. However, not much is known about its application in patients with peripheral oedema of cardiopulmonary origin. We measured the reproducibility of a water‐displacement apparatus with a solid object and in ten non‐oedematous clinical patients (group A). The day‐to‐day variability of the leg volume was assessed in the same group. The diurnal variability was assessed in ten patients with persisting peripheral oedema (group B). The effect of treatment on the severity of peripheral oedema was evaluated in another nine patients with peripheral oedema, who were in need of diuretic treatment (group C). Volumetric results were compared to the ankle circumference method and the body weight method. The coefficient of variation was 0·16% in the fixed object and 0·47% in group A. The day‐to‐day variability was 1·52% after 1 day and 1·76% after a mean interval of 4·8 days. In group B, leg volume and circumference increased during the day (5·9%, P<0·001, and 2·4%, P<0·01, respectively), while body weight remained unchanged. In group C, leg volume, circumference and body weight decreased significantly after treatment (13·1%, P<0·01, 7·1%, P<0·05, and 5·9%, P<0·05). The correlation between the changes in volume and body weight was poor (r=0·37, P=0·33). In conclusion, (1) water‐displacement volumetry is highly reproducible, (2) a diurnal variability of peripheral oedema was found, and (3) volumetry is a suitable tool for monitoring peripheral oedema, while the body weight method appears to be less accurate.     

Venous plasma adrenaline response to orthostatic syncope during tilting in healthy men

Summary. The effect of transient cerebral ischaemia connected with acute orthostatic hypotension on plasma adrenaline and noradrenaline levels was studied in seven healthy male volunteers during tilt. Sublingual administration of 1 mg nitroglycerin was used to block peripheral vascular reflexes and thus to provoke orthostatic intolerance. A consistent increase in plasma adrenaline concentrations (from 19·2 to 104·3 pg/ml on average, P<0·01) was found in six subjects who developed clinical signs of collapse after tilting. Plasma adrenaline never changed after tilting without collapse. Posturally stimulated plasma noradrenaline increases were similar yet irrespective of the presence of collapse.     

Effects of rest intervals and training loads on metabolic stress and muscle hypertrophy

We investigated the effects of volume‐matched resistance training (RT) with different training loads and rest intervals on acute responses and long‐term muscle and strength gains. Ten subjects trained with short rest (30 s) combined with low load (20 RM) (SL) and ten subjects performed the same protocol with long rest (3 min) and high load (8 RM) (LH). Cross‐sectional area (CSA) of the upper arm was measured by magnetic resonance imaging before and after 8 weeks of training. Acute stress markers such as growth hormone (GH) and muscle thickness (MT) changes have been assessed pre and post a single RT session. Only the SL group demonstrated significant increases in GH (7704·20 ± 11833·49%, P<0·05) and MT (35·2 ± 16·9%, P<0·05) immediately after training. After 8 weeks, the arm CSA s in both groups significantly increased [SL: 9·93 ± 4·86% (P<0·001), LH: 4·73 ± 3·01% (P<0·05)]. No significant correlation between acute GH elevations and CSA increases could be observed. We conclude that short rest combined with low‐load training might induce a high amount of metabolic stress ultimately leading to improved muscle hypertrophy while long rest with high‐load training might lead to superior strength increases. Acute GH increases seem not to be directly correlated with muscle hypertrophy.     

The influence of water ingestion on postexercise hypotension and standing haemodynamics

In young healthy adults, postexercise hypotension (PEH) occurs after a single bout of dynamic exercise due to peripheral vasodilation. Gravitational stress may further aggravate the magnitude of PEH, thus predisposing to orthostatic intolerance. As water drinking activates sympathetic vasoconstriction, it might offset PEH via enhanced α‐adrenergic vascular responsiveness. We hypothesized that water ingestion before exercise would decrease the magnitude of PEH and improve the haemodynamic reaction to active standing postmaximal exercise. In a randomized fashion, 17 healthy adults (nine men; eight women, 21·2 ± 1·6 years) ingested 50 and 500 ml of water before completing resting, cycle ergometer and recovery protocols on two separate days. After exercise, measurements [arterial blood pressure (BP), heart rate and spectral heart rate variability (HRV)] were taken in the seated position followed by 5 min of active standing. Compared to that seen post‐50 ml of water, the 500 ml volume elicited an overall increase in BP (P < 0·05). Nevertheless, the magnitude of PEH was not different after either volume of water. There was an overall bradycardic effect of water, and this was accompanied by increased high‐frequency power (P < 0·05). Finally, no BP, heart rate or HRV differences were found between conditions in response to active standing. These data suggest that, despite being well preserved after maximal exercise, the water pressor response does not affect the magnitude of PEH. They also indicate that drinking 500 ml of water does not impact the BP, heart rate or HRV response to 5 min of active standing during recovery postmaximal exercise.     

Cerebral oxygen saturation evaluated by near‐infrared time‐resolved spectroscopy (TRS) in pregnant women during caesarean section – a promising new method of maternal monitoring

Time‐resolved spectroscopy (TRS‐20) measures tissue oxygen saturation (%) by evaluating the absolute concentrations of oxygenated, deoxygenated and total haemoglobin based on measurement of the transit time of individual photons through a tissue of interest. We measured tissue oxygen saturation in the prefrontal lobes of the brain by TRS‐20 in eighteen pregnant women during caesarean section. In a case of placenta previa, massive bleeding immediately decreased cerebral oxygen saturation from 67·2% to 54·2%, but did not alter peripheral tissue oxygenation as measured by pulse oximetry. Four cases of pre‐eclampsia revealed chronic changes in elevated base levels of cerebral oxygen saturation, though peripheral oxygen saturation was similar to that in normotensive pregnant women. Average cerebral oxygen saturation in the cases of pre‐eclampsia before the introduction of anaesthesia was 73·6 ± 4·4 (SD)% (n = 4), significantly higher than in normotensive pregnant women, 67·2 ± 4·3% (n = 13, P<0·05). Z‐scores of cerebral oxygen saturation prior to anaesthesia positively correlated with those of systolic or diastolic blood pressure. TRS‐20 could detect acute as well as chronic changes in brain oxygen saturation in response to pregnancy‐associated complications.     

Effect of nasal air temperature on FEV1 and specific airways conductance

We investigated whether changes in nasal air temperature affect specific airway conductance (SGaw) and one second forced expiratory volume (FEV₁) in 10 asthmatic patients with a history of cold‐sensitive asthma and eight healthy subjects. An air‐stream (0·6 l s^–1) of –15°C, +22°C or +37°C was blown into both nostrils during a Valsalva manoeuvre. Each provocation consisted of 10 puffs of air, each of 15 s duration, at 1 min intervals. Before and at regular intervals after the provocations, SGaw and FEV₁ were determined. In asthmatics, after cold air provocation, SGaw fell 23% (P<0·01) and FEV₁ 8% (P<0·01). After the warm air provocations, SGaw rose 15% (P<0·01) and FEV₁ 6% (P<0·01). After the ambient air provocations, no significant changes occurred in SGaw or FEV₁. In the healthy subjects, the nasal provocations caused no significant changes in lung function. The present study shows that cold air in the nose causes a slight obstruction and warm air possibly a slight dilatation of the lower airways in patients with a history of cold‐sensitive asthma but not in healthy subjects.