Search

Introduction: Measuring physiological parameters at depth is an emergent challenge for athletic training, diver's safety and biomedical research. Recent advances in wearable sensor technology made this challenge affordable; however, its impact on breath-hold diving has never been comprehensively discussed. Methods: We performed a systematic review of the literature in order to assess what types of sensors are available or suitable for human breath-hold diving, within the two-fold perspective of safety and athletic performance. Results: In the 52 studies identified, sensed physiological variables were: electrocardiogram, body temperature, blood pressure, peripheral oxygen saturation, interstitial glucose concentration, impedance cardiography, heart rate, body segment inertia and orientation. Conclusions: Limits and potential of each technology are separately reviewed. Inertial sensor technology and transmission pulse oximetry could produce the greatest impact on breath-hold diving performances in the future. [ABSTRACT FROM AUTHOR]

Background: Depression is associated with reduced heart rate variability (HRV) in healthy and cardiac samples, which may be accounted for by physical fitness. In a small sample of cardiac patients, activity and fitness levels attenuated the relationship between HRV and depression. In the current study of heart failure (HF) patients, we hypothesized that depressive symptoms and HRV would be inversely related and physical fitness would attenuate this association.Purpose: To determine if previous associations among depressive symptoms, physical fitness, and HRV would replicate in a sample of HF patients.Methods: The sample consisted of HF patients (N = 125) aged 68.55 ± 8.92 years, 68.8% male, and 83.2% Caucasian. The study was cross-sectional and a secondary analysis of a nonrandomized clinical trial (Trial Identifier: NCT00871897). Depressive symptoms were evaluated using the Beck Depression Inventory (BDI)-II, fitness with the 2 min step test (2MST), and HRV during a 10 min resting laboratory psychophysiology protocol. The dependent variable in hierarchical linear regressions was the root mean square of successive differences.Results: Controlling for sex, age, β-blocker use, hypertension, and diabetes, higher BDI-II scores significantly predicted lower HRV, β = -.29, t(92) = -2.79, p < .01. Adding 2MST did not attenuate the relationship in a follow-up regression.Conclusion: Depressive symptoms were associated with lower HRV in HF patients, independent of physical fitness. Given the prevalence of depression and suppressed HRV common among HF patients, interventions addressing depressive symptoms and other predictors of poor outcomes may be warranted. [ABSTRACT FROM AUTHOR]

Purpose: We aimed to determine the position and size of the sphenoid sinus (SS) in our study and compare the results of the measurements relative to age, gender, and the presence of pituitary adenoma using multidetector computerized tomography (MDCT). Methods: We retrospectively evaluated the paranasal sinus computerized tomography (CT) images of 200 individuals (age range of all the individuals 4–84 years; 101 females, 99 males; age range of individuals with pituitary adenoma 15–63 years; 15 females, 9 males) with 24 pituitary adenomas. The shape of SS were identified and classified, volume were measured by MDCT also for individuals with pituitary adenoma. Results: It was determined that the volume averages were significantly affected by the type of SS. Among all the individuals studied, the sellar type of SS was most frequently observed (41.5%), followed by the postsellar type (38.5%), and the least observed was the presellar type (9%). The volume of the SS is bigger in males than females although the volume is not affected by the presence of pituitary adenomas. The development of the SS continues until the age of nine. Conclusion: The morphology and morphometry of the SS show individual differences. These anatomic variations are important for decision making and application for surgical interventions (especially transsphenoidal surgery). [ABSTRACT FROM AUTHOR]

Introduction: The influence of acute exercise on sensory sensitivity (SS) differs according to the type and duration of exercise performed. In the present study, we assessed changes on SS soon after a maximal dynamic apnoea. Methods: Thirty-nine experienced male breath-hold divers were recruited. Critical flicker fusion frequency (CFFF) thresholds were used to measure SS. Thresholds were determined before and after a maximal dynamic apnoea. Immediately after surfacing, heart rate and oxygen saturation (SpO2) were recorded for two minutes. Results: After maximal dynamic apnoea, SpO2 was significantly decreased (from mean 97.3% pre-dive to mean 63.1% postdive; P < 0.0001; η² P = 0.86), but this acute hypoxaemia did not trigger changes in SS (post-dive value 102% of baseline; P = 0.22; η² P = 0.03). Pearson correlation analysis revealed a moderate association between SS with swimming speed (r = 0.423) and apnoea time (r = -0.404). Conclusions: A maximal dynamic apnoea did not produce changes in central nervous system fatigue or cortical arousal. We found no relationship between the hypoxaemia level reached after a maximal apnoea and changes in the CFFF thresholds. This study suggests that the time of exposure to hypoxia during a maximal voluntary apnoea is not enough to produce changes in SS. [ABSTRACT FROM AUTHOR]

The article reports the hyperbaric treatment for decompression sickness. Topics include how decompression sickness (DCS) is caused by formation of bubbles in tissues and blood when the sum of dissolved gas pressures exceeds ambient pressure; and the diagnosis of DCS based on careful evaluation of the circumstances of the dive, the presence of known risk factors, and the post-dive latency and nature of the manifestations.

Background: Expansion of the intravascular compartment is common to treat haemodynamic instability in ICU patients. The most useful and accurate variables to guide and evaluate a fluid challenge remain debated and incompletely investigated resulting in significant variability in practice. The analogue mean systemic pressure has been reported as a measure of the intravascular volume state.Methods: This is a protocol and statistical analysis plan for a review of the application of an analogue of the mean systemic pressure and the use of derived variables to assess the volume state and volume responsiveness. A pulmonary artery catheter was used in 286 postoperative cardiac surgical patients to monitor cardiac output before and after a fluid bolus in addition to arterial and central venous pressures. With otherwise similar monitoring, echocardiography was used in 540 general ICU patients to determine cardiac outputs and indices related to intravascular filling. The responses to a fluid bolus or the passive leg raising manoeuvre will be investigated using continuous and dichotomous definitions of volume responsiveness. The results will be stratified according to the method of monitoring cardiac output.Conclusions: This study investigating 2 cohorts that encompass a wide variety of reasons for haemodynamic instability will illustrate the applicability of the analogue mean systemic pressure and derived variables to assess the volume state and responsiveness. The results may guide the rationale and design of interventional studies. [ABSTRACT FROM AUTHOR]

The descent is a critical part of a dive, both physically and mentally. Pulmonary ventilation, expressed as respiratory minute volume (RMV) and heart rate (HR) were recorded during fast and slow descents to 35 meters (m) in open water while breathing compressed air, and during swimming horizontally at moderate velocity at an 11-m depth. Values of both types of descents were compared with reference values recorded at 11 m, the "plateau" phase, halfway through the 35-m dives. It is hypothesized that the "slow-descent" and "plateau-phase" values will be less than 'fast-descent values. Depth, cylinder pressure, water temperature and HR were recorded with a dive computer yielding time-averaged means (mRMV and mHR) for the descent and for plateau. Of the 18 divers included, 16 performed the fast descents and 11 made the slow descents. The fast descents (23 m⋅min-1 vertically), performed with 0-8 fin kicks, yielded mRMVDescent=28 ambient L (aL)⋅min-1, which is 82% higher (P<0.001) than mRMVPlateau of 15 aL⋅min-1. Further, mHRDescent was 121 beats⋅min-1 23% higher (P<0.001), than mHRPlateau of 100 bpm. Slow descents (2.4 m⋅min-1 vertically) yielded 17 aL⋅min-1 with mHR=101 beats⋅min-1, values only slightly higher than at Plateau. The 11-m dive (swimming horizontally) yielded 24 m⋅min-1 with 32 fin kicks⋅min-1, mRMV=35 aL⋅min-1 and mHR=115 beats⋅min-1. Fast descents cause a higher RMV and HR that cannot be explained by physiology alone. Presumably mental stress is a main contributor. For dives deeper than 20 m, a descent velocity of 10 m⋅min-1 is recommended to reduce cardiac stress, in particular for older divers. [ABSTRACT FROM AUTHOR]

Aim: Aquatic exercise might improve endothelial function due to hydrostatic pressure increasing blood flow and causing shear stress to the endothelium. However, the acute effect of aerobic exercise in water on endothelial function is unclear. The present study compares the acute effect of aerobic exercise at moderate intensity in water and on land on endothelial function. Methods: Nine healthy young men walked on a treadmill for 30 min while immersed in water up to the xiphoid at 30.0 ± 0.2°C and on land at an intensity equivalent to 60% heart rate reserve in a crossover trial. Brachial artery flow-mediated dilation (FMD) was measured at baseline and at 30 and 60 min after exercise. Autonomic nervous activity was compared among conditions at the heart rate variability (HRV) during exercise. Results: FMD significantly decreased at 30 min after exercise on land trial (p < 0.05), but did not change after the aquatic trial. However, FMD was significantly higher after aquatic trial than land trial (p < 0.05) at 30 and 60 min after exercise, whereas heart rate, blood pressure, and HRV did not significantly differ between them. Conclusion: These findings demonstrate that aerobic exercise in water suppressed the decrease in FMD compared with that on land, regardless of autonomic nervous activity. [ABSTRACT FROM AUTHOR]

Various methods for indirect assessment of mean systemic filling pressure (MSFP) produce controversial results compared with MSFP at zero blood flow. We recently reported that the difference between MSFP at zero flow measured by right atrial balloon occlusion (MSFPRAO) and MSFP estimated using inspiratory holds depends on the volume status. We now compare three indirect estimates of MSFP with MSFPRAO in euvolemia, bleeding, and hypervolemia in a model of anesthetized pigs (n = 9) with intact circulation. MSFP was estimated using instantaneous beat-to-beat venous return during tidal ventilation (MSFPinst_VR), right atrial pressure-flow data pairs at flow nadir during inspiratory holds (MSFPnadir_hoid), and a dynamic model analog adapted to pigs (MSFPa). MSFPRAO was underestimated by MSFPnadir_hold and MSFPa in all volume states. Volume status modified the difference between MSFPRAO and all indirect methods (method X volume state interaction, P ≤ 0.020). All methods tracked changes in MSFPRAO concordantly, with the lowest bias seen for MSFPa [bias (confidence interval): -0.4 (-0.7 to -0.0) mmHg]. We conclude that indirect estimates of MSFP are unreliable in this experimental setup. NEW & NOTEWORTHY For indirect estimations of MSFP using inspiratory hold maneuvers, instantaneous beat-to-beat venous return, or a dynamic model analog, the accuracy was affected by the underlying volume state. All methods investigated tracked changes in MSFPRAO concordantly. [ABSTRACT FROM AUTHOR]

Copyright of Der Pneumologe is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper presents a unified approach based on the recurrence quantification analysis (RQA) and approximate entropy (ApEn) for the classification of heart rate variability (HRV). In this paper, the optimum tolerance threshold (ropt) corresponding to ApEnmax has been used for RQA calculation. The experimental data length (N) of RR interval series (RRi) is optimized by taking ropt as key parameter. ropt is found to be lying within the recommended range of 0.1 to 0.25 times the standard deviation of the RRi, when N ≥ 300. Consequently, RQA is applied to the age stratified RRi and indices such as percentage recurrence (%REC), percentage laminarity (%LAM), and percentage determinism (%DET) are calculated along with ApEnmax, [Formula: see text], [Formula: see text], and an index namely the radius differential (RD). Certain standard HRV statistical indices such as mean RR, standard deviation of RR (or NN) interval (SDNN), and the square root of the mean squared differences of successive RR intervals (RMSSD) (Eur Hear J 17:354-381, 1996) are also found for comparison. It is observed that (i) RD can discriminate between the elderly and young subjects with a value of 0.1151 ± 0.0236 (mean ± SD) and 0.0533 ± 0.0133 (mean ± SD) respectively for the elderly and young subjects and is found to be statistically significant with p < 0.05. (ii) Similar significant discrimination was obtained using [Formula: see text] with a value of 0.1827 ± 0.0382 (mean ± SD) and 0.2248 ± 0.0320 (mean ± SD) (iii) other significant indices were found to be %REC, %DET, %LAM, SDNN, and RMSSD; however, ApEnmax was found to be insignificant with p > 0.05. The above features of RRi time series were tested for classification using support vector machine (SVM) and multilayer perceptron neural network (MLPNN). Higher classification accuracy was achieved using SVM with a maximum value of 99.71%. Graphical abstract. [ABSTRACT FROM AUTHOR]

Purpose: Underwater divers face several potential neurological hazards when breathing compressed gas mixtures including nitrogen narcosis which can impact diver's safety. Various human studies have clearly demonstrated brain impairment due to nitrogen narcosis in divers at 4 ATA using critical flicker fusion frequency (CFFF) as a cortical performance indicator. However, recently some authors have proposed a probable adaptive phenomenon during repetitive exposure to high nitrogen pressure in rats, where they found a reversal effect on dopamine release.Methods: Sixty experienced divers breathing Air, Trimix or Heliox, were studied during an open water dive to a depth of 6 ATA with a square profile testing CFFF measurement before (T0), during the dive upon arriving at the bottom (6 ATA) (T1), 20 min of bottom time (T2), and at 5 m (1.5 ATA) (T3).Results: CFFF results showed a slight increase in alertness and arousal during the deep dive regardless of the gas mixture breathed. The percent change in CFFF values at T1 and T2 differed among the three groups being lower in the air group than in the other groups. All CFFF values returned to basal values 5 min before the final ascent at 5 m (T3), but the Trimix measurements were still slightly better than those at T0.Conclusions: Our results highlight that nitrogen and oxygen alone and in combination can produce neuronal excitability or depression in a dose-related response. [ABSTRACT FROM AUTHOR]

Background Guidelines for patient behavior following transsphenoidal surgery do not exist. To gain generally recommendations, the German pituitary working group conducted a study among pituitary surgeons to elucidate their opinions and customs of patients' counselling. Methods Questions concerning daily activities, exertion of sports and work life were addressed. It was asked to provide the postoperative time interval after which specific activities can be resumed both after a routine or an extended approach. Results Fourteen pituitary surgeons returned the completed questionnaire. Following routine operations, washing the hair was allowed within one week, blowing the nose after 3, flying on an airplane and driving a car after one, lifting heavy weights after 4, playing wind instruments after 6, use of CPAP (continuous positive airway pressure) device after 3, permit leisure sports after 2 to 4 weeks (except for scuba diving). Competitive sports can be resumed after 6 weeks. Occupation with mental demands was considered feasible after 2 weeks, with physical labor after 4 weeks. After extended transsphenoidal surgery, the recommended time interval was roughly twice as long compared to the routine approach. Driving a car was allowed within the first 4 weeks after surgery by some pituitary surgeons, while others allow driving only after 3 months analogous to the regulations after craniotomy. The risk of scuba diving was considered high. Conclusions The data of our study and the literature, and expert opinions from related scientific fields resulted in a consensus on recommendations for patients' conduct to minimize risks after transsphenoidal surgery. [ABSTRACT FROM AUTHOR]

A letter to the editor is presented in response to an article on breath-hold diving (BHD) as a causative factor for neurological decompression sickness (DCS), such as hypoxemia, body position, and increased cardiac output, by J.D. Schipke and K. Tetzlaff, published in a previous issue.

A letter to the editor is presented in response to an article on relation between decompression sickness (DCS) in breath-hold divers (BHD) and arterialization of venous gas emboli (VGE), by J.D. Schipke and K. Tetzlaff, published in a previous issue.

Introduction: Drowning is likely to result from impairment of consciousness when scuba diving. Causes include toxic effects of breathing gas, including nitrogen narcosis and oxygen toxicity, and arterial gas embolism. Methods: Review of the medical records of scuba divers who had impaired consciousness underwater that could not be attributed to toxic effects of breathing gas or arterial gas embolism. Results: Four scuba divers had episodes of impaired consciousness when at shallow depths (8−18 m) underwater. The descriptions of the episodes were very similar. Three had histories of recurrent episodes of vasovagal syncope on land. Conclusions: Absence of other causes for their impaired consciousness underwater leads to the conclusion that the probable cause was vasovagal syncope. [ABSTRACT FROM AUTHOR]

Light is a common ambient medium to express additional information in a peripheral and calm way, but it is also an environmental stimulant to create atmosphere, evoke moods, and provide immersive experiences. Through the design of the DeLight system, we aim to establish a biofeedback-driven lighting environment that informs users about their stress level for intervention and assists them in biofeedback relaxation training. In this study, DeLight is interfaced with a heart rate variability biofeedback system with two modes for different purposes: stress intervention and relaxation assistance. We evaluated the prototype of DeLight in two user studies. The results of the first study show that DeLight has the potential for stress intervention; the HRV biofeedback through the changes of ambient light could improve a user’s awareness of stress and trigger behavioral conditioning, such as deep breathing. The results of the second study confirm that DeLight has potential as a new biofeedback interface for relaxation assistance; biofeedback through an immersive lighting environment can support physiological regulation as effectively as graphic biofeedback; it offers enhanced relaxation effects regarding both subjective experience and physiological arousal. These findings suggest that the biofeedback-driven ambient light can perform as persuasive technology in the domain of health self-management. The combination of decorative and informative aspects enables the lighting interface to offer the users a comfortable and relaxing condition for biofeedback-assisted relaxation training. [ABSTRACT FROM AUTHOR]

Copyright of Sanidad Militar is the property of Ministerio de Defensa, Subdireccion General de Publicaciones y Patrimonio Cultural and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract: Background: The etiologies of intraoperative cardiac arrest within otolaryngology are not well understood as they are rare events. Methods: A comprehensive review of the etiologies and corresponding pathophysiologic neural mechanisms of intraoperative cardiac arrest in otolaryngologic surgery are examined. Results: The occurrence of this rare complication has been described in a range of head and neck procedures, including but not limited to suspension laryngoscopy and oncologic resections in the neck, maxilla and thyroid. Three anatomically distinct pathways leading to intraoperative cardiac arrest are described: direct vagal stimulation, the trigeminocardiac reflex and the baroreceptor reflex. All three share the final common pathway of parasympathetic signaling to the sinoatrial node via the cardiac fibers of the vagus nerve. Conclusion: With a firm understanding of the mechanistic underpinning of this rare phenomenon, otolaryngologic surgeons can be better prepared for its occurrence. [ABSTRACT FROM AUTHOR]

Aims It has been suggested that the nitric oxide-sensitive guanylyl cyclase (NO-GC)/cyclic guanosine monophosphate (cGMP)-dependent signalling pathway affords protection against cardiac damage during acute myocardial infarction (AMI). It is, however, not clear whether the NO-GC/cGMP system confers its favourable effects through a mechanism located in cardiomyocytes (CMs). The aim of this study was to evaluate the infarct-limiting effects of the endogenous NO-GC in CMs in vivo. Methods and results Ischemia/reperfusion (I/R) injury was evaluated in mice with a CM-specific deletion of NO-GC (CM NO-GC KO) and in control siblings (CM NO-GC CTR) subjected to an in vivo model of AMI. Lack of CM NO-GC resulted in a mild increase in blood pressure but did not affect basal infarct sizes after I/R. Ischemic postconditioning (iPost), administration of the phosphodiesterase-5 inhibitors sildenafil and tadalafil as well as the NO-GC activator cinaciguat significantly reduced the amount of infarction in control mice but not in CM NO-GC KO littermates. Interestingly, NS11021, an opener of the large-conductance and Ca2+-activated potassium channel (BK), an important downstream effector of cGMP/cGKI in the cardiovascular system, protects I/R-exposed hearts of CM NO-GC proficient and deficient mice. Conclusions These findings demonstrate an important role of CM NO-GC for the cardioprotective signalling following AMI in vivo. CM NO-GC function is essential for the beneficial effects on infarct size elicited by iPost and pharmacological elevation of cGMP; however, lack of CM NO-GC does not seem to disrupt the cardioprotection mediated by the BK opener NS11021. [ABSTRACT FROM AUTHOR]

Summary: Background: Water immersion and aquatic exercise can be an important therapeutic tool in patients suffering from heart disease (HD). However, the effects of water immersion on heart rate variability (HRV) in HD participants remain unknown. Methods: Twenty‐eight volunteers in sinus rhythm within the same age range took part in this study: 18 HD and ten healthy controls (HC). Heart rhythm was collected with a heart rate monitor (sampling rate 1000 Hz) for periods of 10 min at rest in the supine position on land, standing on land (STL) and standing in water (STW) to the xiphoid process. Results: Heart disease participants had the same response as HC participants to the three experimental conditions (no significant between‐group differences in all HRV variables). STW (immersion) caused in both groups to increase HRV when compared to supine and STL. Conclusion: Heart disease participants demonstrate similar beneficial adaptations as HC participants to the effects of immersion, reinforcing the concept that immersion can be a valuable aquatic cardiac rehabilitation tool to acutely increase HRV. Approaches that improve HRV in both healthy and cardiac patients may have a positive impact on the reduction of morbidity and mortality. [ABSTRACT FROM AUTHOR]

Background: Advanced age is an independent predictor of poor outcome after cardiac arrest (CA). From experimental studies of regional ischemia-reperfusion injury, advanced age is associated with larger infarct size, reduced organ function, and augmented oxidative stress. The objective of this study was to investigate the effect of age on cardiovascular function, oxidative stress, inflammation, and endothelial activation after CA representing global ischemia-reperfusion.Methods: Aged (26 months) and young (5 months) rats were subjected to 8 min of asphyxia induced CA, resuscitated and observed for 360 min. Left ventricular pressure-derived cardiac function was measured at baseline and 360 min after CA. Blood samples obtained at baseline, 120 min, and 360 min after CA were analyzed for IL-1β, IL-6, IL-10, TNF-α, elastase, sE-selectin, sL-selectin, sI-CAM1, hemeoxygenase-1 (HO-1) and protein carbonyl. Tissue samples of brain, heart, kidney, and lung were analyzed for HO-1.Results: Cardiac function, evaluated by dP/dtmax and dP/dtmin , was decreased after CA in both young and aged rats, with no group differences. Mean arterial pressure increased after CA in young, but not old rats. Aged rats showed significantly higher plasma levels of elastase and sE-selectin after CA, and there was a significant different development over time between groups for IL-6 and IL-10. Young rats showed higher levels of HO-1 in plasma and renal tissue after CA.Conclusion: In a rat model of asphyxial CA, advanced age is associated with an attenuated hyperdynamic blood pressure response and increased endothelial activation. [ABSTRACT FROM AUTHOR]

The objective of this study is to examine the myocardial protective effect of antegrade cardioplegic cardiac arrest (ACC) versus ventricular fibrillation (VF) on short-term and mid-term left ventricular (LV) function in right ventricular outflow tract (RVOT) surgery. RVOT operations conducted from January 2006 to December 2015 were reviewed. The numbers of cases using ACC and VF were 71 and 49, respectively. Postoperative mortality and morbidity were compared between the two groups. Before and after propensity score matching, left ventricular ejection fraction (LVEF) and left ventricular end-systolic/end-diastolic diameter (LVESD/LVEDD) in echocardiography were measured immediately after operation and at mid-term follow-up between postoperative 6 and 24 months. There was no perioperative mortality or cerebrovascular accident. There was no statistically significant difference in the incidence of ventricular and atrial arrhythmia. In the overall patient group, LVESD was significantly decreased in the ACC group compared to the VF group immediately after operation (−0.65 ± 3.55 mm vs. 2.99 ± 4.98 mm, P = 0.001). Mid-term follow-up data demonstrated that LVEF at midterm was higher in the ACC group than in the VF group (64.80% ± 7.40% vs. 60.24% ± 7.93%, P = 0.022). However, the increased amount compared to preoperative value was not statistically significant (1.94% ± 12.65% vs. −2.94% ± 9.41%, P = 0.059). After propensity score matching, the LVEF was significantly improved in the ACC group compared to the VF group at the mid-term follow-up (6.16% ± 6.77% vs. −5.41% ± 9.05%, P = 0.001). Multiple linear regression model demonstrated that lower preoperative LVEF, ACC rather than VF, and exclusion of RVOT reconstruction procedure were positive prognostic factors for the improvement of LVEF at mid-term follow up. The results of this study suggest that myocardial protection using ACC is safe and may be more beneficial in LV function recovery up to the mid-term follow-up after pulmonary valve replacement and other RVOT procedures. [ABSTRACT FROM AUTHOR]

Key points Wave travel plays an important role in cardiovascular physiology. However, many aspects of pulmonary arterial wave behaviour remain unclear., Wave intensity and reservoir-excess pressure analyses were applied in the pulmonary artery in subjects with and without pulmonary hypertension during spontaneous respiration and dynamic stress tests., Arterial wave energy decreased during expiration and Valsalva manoeuvre due to decreased ventricular preload. Wave energy also decreased during handgrip exercise due to increased heart rate., In pulmonary hypertension patients, the asymptotic pressure at which the microvascular flow ceases, the reservoir pressure related to arterial compliance and the excess pressure caused by waves increased. The reservoir and excess pressures decreased during Valsalva manoeuvre but remained unchanged during handgrip exercise., This study provides insights into the influence of pulmonary vascular disease, spontaneous respiration and dynamic stress tests on pulmonary artery wave propagation and reservoir function., Abstract Detailed haemodynamic analysis may provide novel insights into the pulmonary circulation. Therefore, wave intensity and reservoir-excess pressure analyses were applied in the pulmonary artery to characterize changes in wave propagation and reservoir function during spontaneous respiration and dynamic stress tests. Right heart catheterization was performed using a pressure and Doppler flow sensor tipped guidewire to obtain simultaneous pressure and flow velocity measurements in the pulmonary artery in control subjects and patients with pulmonary arterial hypertension (PAH) at rest. In controls, recordings were also obtained during Valsalva manoeuvre and handgrip exercise. The asymptotic pressure at which the flow through the microcirculation ceases, the reservoir pressure related to arterial compliance and the excess pressure caused by arterial waves increased in PAH patients compared to controls. The systolic and diastolic rate constants also increased, while the diastolic time constant decreased. The forward compression wave energy decreased by ∼8% in controls and ∼6% in PAH patients during expiration compared to inspiration, while the wave speed remained unchanged throughout the respiratory cycle. Wave energy decreased during Valsalva manoeuvre (by ∼45%) and handgrip exercise (by ∼27%) with unaffected wave speed. Moreover, the reservoir and excess pressures decreased during Valsalva manoeuvre but remained unaltered during handgrip exercise. In conclusion, reservoir-excess pressure analysis applied to the pulmonary artery revealed distinctive differences between controls and PAH patients. Variations in the ventricular preload and afterload influence pulmonary arterial wave propagation as demonstrated by changes in wave energy during spontaneous respiration and dynamic stress tests. [ABSTRACT FROM AUTHOR]

Copyright of Jordan Journal of Pharmaceutical Sciences is the property of University of Jordan and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The frequency of decompression illness was high among the extinct marine 'reptiles' and very low among the marine mammals. Signs of decompression illness are still found among turtles but whales and seals are unaffected. In humans, the risk of decompression illness is five times increased in individuals with Patent Foramen Ovale; this condition allows blood shunting from the venous circuit to the systemic circuit. This right-left shunt is characteristic of the 'reptile' heart, and it is suggested that this could contribute to the high frequency of decompression illness in the extinct reptiles. [ABSTRACT FROM AUTHOR]

Water immersion alters the autonomic nervous system (ANS) response in humans. The effect of water immersion on executive function and ANS responses related to executive function tasks was unknown. Therefore, this study aimed to determine whether water immersion alters ANS response during executive tasks. Fourteen healthy participants performed color–word-matching Stroop tasks before and after non-immersion and water immersion intervention for 15 min in separate sessions. The Stroop task-related skin conductance response (SCR) was measured during every task. In addition, the skin conductance level (SCL) and electrocardiograph signals were measured over the course of the experimental procedure. The main findings of the present study were as follows: 1) water immersion decreased the executive task-related sympathetic nervous response, but did not affect executive function as evaluated by Stroop tasks, and 2) decreased SCL induced by water immersion was maintained for at least 15 min after water immersion. In conclusion, the present results suggest that water immersion decreases the sympathetic skin response during the color–word Stroop test without altering executive performance. [ABSTRACT FROM AUTHOR]

Aim Oxidative stress is increased in recreational technical diving. In an explorative retrograde study we investigated the hypothesis that, (1) repetitive, multi-day dives with oxygen-enriched breathing gases will have an impact on physiological measures, (2) negative effects can be assessed within one week post-dive. Study Design Exploratory retrospective crossover study. Setting Open-water study. Participants Ten healthy experienced technical divers. Interventions Repetitive dives with oxygen-enriched breathing gases during a 5-days diving trip to the Adriatic Sea (Croatia). Outcome Measures Basic measures of medical examination, electrocardiography, echocardiography, body plethysmography, and spiroergometry. Results The divers (32±8 years; mean±SD) performed 11±4 dives. Static and dynamic pulmonary measures were slightly decreased after the trip. On the bicycle ergometer, arterial oxygen partial pressure (pO2) remained almost unchanged from rest to 300 W before the trip (87.5±7.9 vs 85.4±9.7 mmHg) it decreased after the trip (90.4 ±7.2 vs 81.8±8.2 mmHg; p<0.05). Peak oxygen uptake (at 300 W) was decreased after the trip (45.1±9.9 vs 41.7±9.8 ml/min; p<0.05). In parallel, the aerobic threshold was decreased (234±43 vs 186±39 W; p<0.05). Conclusions Pulmonary injury is not detected at rest but at substantial physical load on the bicycle. Even after maximum one week, pO2 at 300 W was decreased together with the pulmonary O2 uptake, thus decreasing the aerobic threshold. In conclusion: (1) Multi-day, repetitive tech dives seem to induce - at least transient - pulmonary injury. (2) Pauses during a diving trip or more conservative diving are recommended. (3) A major physiological study on open-water divers can be performed by one single medical practice with an adequately equipped laboratory. [ABSTRACT FROM AUTHOR]

Purpose: Through time- and frequency-domain analysis, we compared the effects of acute hypobaric hypoxia on the changes in heart rate variability (HRV) following night sleeping and morning awakening in individuals with and without acute mountain sickness (AMS).Method: Thirty-nine nonacclimatised healthy individuals were transported by bus from sea level to 3150 m within 3 h. Short-term HRV was measured two times a day-before sleeping (BS) and after awakening (AA)- at 3 days before ascent (T0), two consecutive nights at 3150 m (T1 and T2), and 2 days after descent (T3). AMS was diagnosed using the self-reported Lake Louise score questionnaire.Result: AMS developed in 19 of 39 participants (48.7%). At sea level, individuals had higher HRV at AA than at BS, and the trend of increased HRV at AA remained unchanged at high altitude, irrespective of AMS. At T1 BS, low-frequency power in normalised unit was significantly lower in participants with AMS than in those without AMS. Compared with those at T1 BS, the square root of the mean squared differences of successive normal-normal (NN) intervals, the number of interval differences of successive NN intervals more than 50 ms (NN50), and the proportion derived by dividing NN50 by the total number of NN intervals at T1 AA significantly increased in participants without AMS but nonsignificantly decreased in those with AMS.Conclusion: After rapid ascent, individuals with AMS did not demonstrate sympathetic hyperactivity but did exhibit withdrawal of cardiac vagal modulation in the morning following the first night's sleep. [ABSTRACT FROM AUTHOR]

Coronary microvascular networks play the key role in determining blood flow distribution in the heart. Matching local blood supply to tissue metabolic demand entails continuous adaptation of coronary vessels via regulation of smooth muscle tone and structural dilated vessel diameter. The importance of coronary microcirculation for relevant pathological conditions including angina in patients with normal or near-normal coronary angiograms [microvascular angina (MVA)] and heart failure with preserved ejection fraction (HFpEF) is increasingly recognized. For MVA, clinical studies have shown a prevalence of up to 40% in patients with suspected coronary artery disease and a relevant impact on adverse cardiovascular events including cardiac death, stroke, and heart failure. Despite a continuously increasing number of corresponding clinical studies, the knowledge on pathophysiological cause–effect relations involving coronary microcirculation is, however, still very limited. A number of pathophysiological hypotheses for MVA and HFpEF have been suggested but are not established to a degree, which would allow definition of nosological entities, stratification of affected patients, or development of effective therapeutic strategies. This may be related to a steep decline in experimental (animal) pathophysiological studies in this area during the last 15 years. Since technology to experimentally investigate microvascular pathophysiology in the beating heart is increasingly, in principle, available, a concerted effort to build ‘coronary microcirculatory observatories’ to close this gap and to accelerate clinical progress in this area is suggested. [ABSTRACT FROM AUTHOR]

Background:Liver transplantation is the second most common transplant procedure in the United States. A leading cause of post-transplantation organ dysfunction is I/R injury. During I/R injury, the serine/threonine kinase Akt is activated, stimulating downstream mediators to promote cellular survival. Due to the cellular effects of Akt, therapeutic manipulation of the Akt pathway can help reduce cellular damage during hepatic I/R that occurs during liver transplantation.Objective:A full description of therapeutic options available that target Akt to reduce hepatic I/R injury has not been addressed within the literature. The purpose of this review is to illuminate advances in the manipulation of Akt that can be used to therapeutically target I/R injury in the liver.Methods:An in depth literature review was performed using the Scopus and PubMed databases. A total of 75 published articles were utilized for this manuscript. Terminology searched includes a combination of “hepatic ischemia/reperfusion injury”, “Akt/PKB”, “preconditioning” and “postconditioning.”Results:Four principal methods that reduce I/R injury include hepatic pre- and postconditioning, pharmacological intervention and future miRNA/gene therapy. Discussed therapies used serum alanine aminotransferase levels, liver histology and phosphorylation of downstream mediators to confirm the Akt protective effect.Conclusion:The activation of Akt from the reviewed therapies has resulted in predictable reduction in hepatocyte damage using the previously mentioned measurements. In a clinical setting, these therapies could potentially be used in combination to achieve better outcomes in hepatic transplant patients. Evidence supporting reduced I/R injury through Akt activation warrants further studies in human clinical trials. [ABSTRACT FROM AUTHOR]

Breath-hold diving is an activity that humans have engaged in since antiquity to forage for resources, provide sustenance and to support military campaigns. In modern times, breath-hold diving continues to gain popularity and recognition as both a competitive and recreational sport. The continued progression of world records is somewhat remarkable, particularly given the extreme hypoxaemic and hypercapnic conditions, and hydrostatic pressures these athletes endure. However, there is abundant literature to suggest a large inter-individual variation in the apnoeic capabilities that is thus far not fully understood. In this review, we explore developments in apnoea physiology and delineate the traits and mechanisms that potentially underpin this variation. In addition, we sought to highlight the physiological (mal)adaptations associated with consistent breath-hold training. Breath-hold divers (BHDs) are evidenced to exhibit a more pronounced diving-response than non-divers, while elite BHDs (EBHDs) also display beneficial adaptations in both blood and skeletal muscle. Importantly, these physiological characteristics are documented to be primarily influenced by training-induced stimuli. BHDs are exposed to unique physiological and environmental stressors, and as such possess an ability to withstand acute cerebrovascular and neuronal strains. Whether these characteristics are also a result of training-induced adaptations or genetic predisposition is less certain. Although the long-term effects of regular breath-hold diving activity are yet to be holistically established, preliminary evidence has posed considerations for cognitive, neurological, renal and bone health in BHDs. These areas should be explored further in longitudinal studies to more confidently ascertain the long-term health implications of extreme breath-holding activity.

Swallowing can lead to the development of syncope in people who have difficulty swallowing during food intake. It has shown that even spontaneous saliva swallowing can change heart rate variability (HRV). Recently, it has been suggested that changes in heart rate during swallowing may be caused by respiratory activities. In this study, the hypothesis that swallowing induced HRV are caused from breathing changes during swallowing has been tested. For this purpose, electrocardiogram (ECG), chest circumference (respiration) signals and swallowing sounds were recorded simultaneously from 20 subjects. Subjects were asked not to swallow their saliva in the first 4 min of the experiment and to swallow them several times in the next 4 min. To observe respiratory effects on HRV during swallowing, a detailed cardio-respiratory system mathematical model was used. By applying recorded chest circumference signal to the mathematical model, respiration induced HRV changes were obtained. The HRV parameters of with and without swallowing regions of the real (obtained from ECG) and model-HRV (obtained from mathematical model) were compared by paired Student t test. Statistical differences seen in the real-HRV between the swallowing and non-swallowing regions (SDNN, LF power, approximate entropy) were not observed in the model-HRV. Considering that the only factor constituting HRV in the mathematical model is respiration, it was concluded that swallowing changes HRV with a mechanism other than breathing changes.

Sepsis is the life-threatening organ dysfunction arising from a dysregulated host response to infection. Although the specific mechanisms leading to organ dysfunction are still debated, impaired tissue oxygenation appears to play a major role, and concomitant hemodynamic alterations are invariably present. The hemodynamic phenotype of affected individuals is highly variable for reasons that have been partially elucidated. Indeed, each patient's circulatory condition is shaped by the complex interplay between the medical history, the volemic status, the interval from disease onset, the pathogen, the site of infection, and the attempted resuscitation. Moreover, the same hemodynamic pattern can be generated by different combinations of various pathophysiological processes, so the presence of a given hemodynamic pattern cannot be directly related to a unique cluster of alterations. Research based on endotoxin administration to healthy volunteers and animal models compensate, to an extent, for the scarcity of clinical studies on the evolution of sepsis hemodynamics. Their results, however, cannot be directly extrapolated to the clinical setting, due to fundamental differences between the septic patient, the healthy volunteer, and the experimental model. Numerous microcirculatory derangements might exist in the septic host, even in the presence of a preserved macrocirculation. This dissociation between the macro- and the microcirculation might account for the limited success of therapeutic interventions targeting typical hemodynamic parameters, such as arterial and cardiac filling pressures, and cardiac output. Finally, physiological studies point to an early contribution of cardiac dysfunction to the septic phenotype, however, our defective diagnostic tools preclude its clinical recognition. © 2021 American Physiological Society. Compr Physiol 11:1605-1652, 2021., (Copyright © 2021 American Physiological Society. All rights reserved.)

A letter to the editor is presented in response to an article on pathogenesis of the neurological injury observed in breath-hold divers (BHD), by J.D. Schipke and K. Tetzlaff, published in the previous issue.

A letter to the editor is presented in response to an article on use of Hypoxia-induced pulmonary shunting for monitoring neurological decompression sickness while breath-hold diving.

A letter to the editor is presented in response to an article on role of intrapulmonary arteriovenous anastomoses (IPAVA) in decompression sickness for breath-hold divers.

A letter to the editor is presented in response to an article on occurrence of neurological Decompression Sickness (DCS) after breath-hold diving, published in the previous issue.