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  • 1.
    Eiken, Ola
    et al.
    KTH, School of Technology and Health (STH), Environmental Physiology (Closed 20130701).
    Mekjavic, I.
    Sundblad, Patrik
    KTH, School of Technology and Health (STH), Environmental Physiology (Closed 20130701).
    Kölegård, Roger
    KTH, School of Technology and Health (STH), Environmental Physiology (Closed 20130701).
    G tolerance vis-à-vis pressure-distension and pressure-flow relationships of leg arteries2012In: European Journal of Applied Physiology, ISSN 1439-6319, E-ISSN 1439-6327, Vol. 112, no 10, p. 3619-3627Article in journal (Refereed)
    Abstract [en]

    During increased gravitoinertial (G) load in the head-to-foot direction, pressures in dependent vascular beds are commonly raised to levels capable of distending precapillary vessels, which, in turn, may reduce arterial pressure, and hence compromise the capacity to withstand G load (G tolerance). We hypothesized that distensibility in precapillary leg vessels would be lower in a group of subjects possessing high G tolerance (H; n = 7; relaxed G tolerance = 6.6 ± 0.8 G) than in a group with low G tolerance (L; n = 8; G tolerance = 3.9 ± 0.3 G). The groups were matched with regard to gender, age, weight, height, and resting arterial pressure. Arterial pressure-distension and pressure-flow experiments were performed with the subject supine in a pressure chamber with a lower leg protruding to the outside. Increased intravascular pressure in the blood vessels of the outside leg was accomplished by stepwise increasing chamber pressure to 240 mmHg. Diameter and flow in the posterior tibial artery were measured by ultrasonographic/Doppler techniques. Pressure-induced increments in arterial diameter and flow were more pronounced (p < 0.03) in the L (14.1 ± 4.2% and 32 ± 21 ml/min respectively) than in the H (1.7 ± 5.0% and 1.6 ± 25 ml/min) group, and the pressure thresholds at which these increments commenced were lower (by 52 and 48 mmHg, respectively) in the L than in the H group (p < 0.04). Negative correlations were observed between G tolerance and the increments in diameter and flow (p < 0.02). Thus, the wall stiffness of precapillary leg vessels is greater in individuals with high relaxed G tolerance; whether a causal relationship exists remains to be established.

  • 2.
    Gennser, Mikael
    et al.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Grönkvist, Mikael
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Norrbrand, Lena
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Sundblad, Patrik
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Mekjavic, I.B.
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Effekt av gasdensitet på ventilation och arteriell oxygenmättnad vid normobar och hypobar hypoxi2016Conference paper (Refereed)
  • 3. Gustafsson, T.
    et al.
    Kölegård, Roger
    KTH, School of Technology and Health (STH), Environmental Physiology.
    Sundblad, Patrik
    KTH, School of Technology and Health (STH), Environmental Physiology.
    Norman, B.
    Eiken, Ola
    KTH, School of Technology and Health (STH), Environmental Physiology.
    Elevations of local intravascular pressures release vasoactive substances in humans2013In: Clinical Physiology and Functional Imaging, ISSN 1475-0961, E-ISSN 1475-097X, Vol. 33, no 1, p. 38-44Article in journal (Refereed)
    Abstract [en]

    The wall stiffness of arteries and arterioles adapts to the long-term demands imposed by local intravascular pressure. We investigated whether substances capable of inducing acute and long-term effects on arterial wall stiffness are released locally into the bloodstream in response to an acute marked increase in local intravascular pressure in the blood vessels of the human arm. Experiments were performed on ten subjects positioned in a pressure chamber with one arm extended through a hole in the chamber door and kept at normal atmospheric pressure. Intravascular pressure was increased in the arm, by a stepwise increase in chamber pressure up to +150 mmHg. Diameter and flow were measured in the brachial artery by Doppler ultrasonography. Blood samples were drawn simultaneously from both arms before, during, immediately after and 2 h after the release of the chamber pressure. Plasma levels of endothelin-1 (ET-1), vascular endothelial growth factor A (VEGF-A), fibroblast growth factor 2 (FGF-2) and angiotensin II (Ang-II) were measured. Elevation of chamber pressure by 150 mmHg increased local arterial distending pressure to about 220260 mmHg, resulting in an increase in brachial artery diameter of 9% and flow of 246%. The pressure stimulus increased the plasma levels of ET-1 and Ang-II, but not of VEGF-A or FGF-2 in the test arm. The local release of the vasoconstrictors ET-1 and Ang-II in response to markedly increased distending pressure may reflect one mechanism behind adaptation to acute and long-term changes in intravascular pressure.

  • 4.
    Kölegård, Roger
    et al.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Sundblad, Patrik
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Grönkvist, Mikael
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Är det möjligt att uppskatta Gz-tolerans medelst ortostatisk prov?2015Conference paper (Refereed)
  • 5. Lindholm, P
    et al.
    Sundblad, Patrik
    KTH, School of Technology and Health (STH), Environmental Physiology (Closed 20130701).
    Linnarsson, D
    Oxygen-conserving effects of apnea in exercising men.1999In: Journal of applied physiology, ISSN 8750-7587, E-ISSN 1522-1601, Vol. 87, no 6, p. 2122-2127Article in journal (Refereed)
    Abstract [en]

    We sought to determine whether apnea-induced cardiovascular responses resulted in a biologically significant temporary O(2) conservation during exercise. Nine healthy men performing steady-state leg exercise carried out repeated apnea (A) and rebreathing (R) maneuvers starting with residual volume +3.5 liters of air. Heart rate (HR), mean arterial pressure (MAP), and arterial O(2) saturation (Sa(O(2)); pulse oximetry) were recorded continuously. Responses (DeltaHR, DeltaMAP) were determined as differences between HR and MAP at baseline before the maneuver and the average of values recorded between 25 and 30 s into each maneuver. The rate of O(2) desaturation (DeltaSa(O(2))/Deltat) was determined during the same time interval. During apnea, DeltaSaO(2)/Deltat had a significant negative correlation to the amplitudes of DeltaHR and DeltaMAP (r(2) = 0.88, P < 0.001); i.e., individuals with the most prominent cardiovascular responses had the slowest DeltaSa(O(2))/Deltat. DeltaHR and DeltaMAP were much larger during A (-44 +/- 8 beats/min, +49 +/- 4 mmHg, respectively) than during R maneuver (+3 +/- 3 beats/min, +30 +/- 5 mmHg, respectively). DeltaSa(O(2))/Deltat during A and R maneuvers was -1.1 +/- 0.1 and -2.2 +/- 0.2% units/s, respectively, and nadir Sa(O(2)) values were 58 +/- 4 and 42 +/- 3% units, respectively. We conclude that bradycardia and hypertension during apnea are associated with a significant temporary O(2) conservation and that respiratory arrest, rather than the associated hypoxia, is essential for these responses.

  • 6.
    Linnarsson, D
    et al.
    Karolinska Institutet.
    Spaak, J
    Karolinska Institutet.
    Sundblad, Patrik
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology. Karolinska Institutet.
    Baroreflex impairment during rapid posture changes at rest and exercise after 120 days of bed rest.2006In: European Journal of Applied Physiology, ISSN 1439-6319, E-ISSN 1439-6327, Vol. 96, no 1, p. 37-45Article in journal (Refereed)
    Abstract [en]

    Orthostatic intolerance is common after space flight and head-down tilt (HDT) bed rest. We hypothesized that HDT-induced impairments of arterial blood pressure (AP) control would be more marked during exercise and that recovery of baroreflex function after very long-term HDT would be delayed. Six subjects were studied before (BDC) during (day 60, D60; D113) and after (recovery day 0, R0; R3; R15) 120 days of HDT. Supine resting subjects were exposed to repeated 1 min passive tilts to upright at 3-min interval. During 50 W steady-state exercise corresponding tilt had a 2-min duration at 4-min interval. The amplitudes of the tilt-induced transient beat-by-beat deviations in AP and rate (HR) were determined during the gravity transients. At rest these deviations did not change over time, but during exercise the total peak-to-nadir range of deviations in systolic AP (SAP) at up-tilt and down-tilt increased to 168+/-16% (mean+/-SEM) of BDC at D113 with no clear recovery upto and including R15. Counter-regulatory HR responses were not increased proportionally and especially not tachycardic responses to up-tilt, resulting in a reduction of baroreflex sensitivity (deltaRR-interval/deltaSAP) by 55+/-9% of BDC at D113 with no recovery upto and including R15. We conclude that prolonged bed rest cause long-lasting impairments in AP control and baroreflex function in exercising humans.

  • 7.
    Montmerle, S.
    et al.
    Karolinska Institutet.
    Sundblad, Patrik
    Karolinska Institutet, Sweden.
    Linnarsson, D.
    Karolinska Institutet.
    Residual heterogeneity of intra- and interregional pulmonary perfusion in short-term microgravity2005In: Journal of applied physiology, ISSN 8750-7587, E-ISSN 1522-1601, Vol. 98, no 6, p. 2268-2277Article in journal (Refereed)
    Abstract [en]

    We hypothesized that the perfusion heterogeneity in the human, upright lung is determined by nongravitational more than gravitational factors. Twelve and six subjects were studied during two series of parabolic flights. We used cardiogenic oscillations of O(2)/SF(6) as an indirect estimate of intraregional perfusion heterogeneity (series 1) and phase IV amplitude (P(4)) as a indirect estimate of interregional perfusion heterogeneity (series 2). A rebreathing-breath holding-expiration maneuver was performed. In flight, breath holding and expiration were performed either in microgravity (0 G) or in hypergravity. Controls were performed at normal gravity (1 G). In series 1, expiration was performed at 0 G. Cardiogenic oscillations of O(2)/SF(6) were 19% lower when breath holding was performed at 0 G than when breath holding was performed at 1 G [means (SD): 1.7 (0.3) and 2.3 (0.6)% units] (P = 0.044). When breath holding was performed at 1.8 G, values did not differ from 1-G control [2.6 (0.8)% units, P = 0.15], but they were 17% larger at 1.8 G than at 1 G. In series 2, expiration was performed at 1.7 G. P(4) changed with gravity (P < 0.001). When breath holding was performed at 0 G, P(4) values were 45 (46)% of control. When breath holding was performed at 1.7 G, P(4) values were 183 (101)% of control. We conclude that more than one-half of indexes of perfusion heterogeneity at 1 G are caused by nongravitational mechanisms.

  • 8. Ostlund, A
    et al.
    Sundblad, Patrik
    KTH, School of Technology and Health (STH), Environmental Physiology (Closed 20130701).
    Demetriades, AK
    Linnarsson, D
    Arterial baroreflex control during mild-to-moderate nitrous oxide narcosis.1999In: Undersea & Hyperbaric Medicine, ISSN 1066-2936, Vol. 26, no 1, p. 15-20Article in journal (Refereed)
    Abstract [en]

    We hypothesized that light-to-moderate inert gas narcosis might play a role in bradycardia in divers by altering sensitivity or response dynamics of arterial baroreflexes. Carotid-cardiac and carotid-mean arterial pressure (MAP) baroreflex response curves were generated by applying multiple levels of neck pressure and suction. Seven healthy volunteers were studied during air breathing (control) and during inhalation of 39% nitrous oxide (N2O). Baseline (pre-stimulus) heart rate (HR) and MAP were not altered by N2O. Range, threshold level, saturation level, and delay of responses did not differ between conditions. For hypertensive stimuli, sensitivity of responses did not differ between air control and N2O inhalation, but for hypotensive stimuli, maximal response gain for HR tended to be reduced with N2O inhalation (P = 0.054). Our results speak against inert gas narcosis as a primary mechanism for hyperbaric bradycardia, but it remains possible that an attenuation of tachycardic responses to hypotensive stimuli plays a role.

  • 9.
    Quintana, M
    et al.
    Karollinska Institutet.
    Gustafsson, T
    Karollinska Institutet.
    Sundblad, Patrik
    Karollinska Institutet.
    Langanger, J
    Karollinska Institutet.
    The effects of heart rate on myocardial velocity and atrio-ventricular displacement during exercise with and without beta-blockade: a tissue Doppler echocardiographic study2005In: European Journal of Echocardiography, ISSN 1525-2167, E-ISSN 1532-2114, Vol. 6, no 2, p. 127-133Article in journal (Refereed)
    Abstract [en]

    BACKGROUND:

    Colour tissue Doppler echocardiography (TDE) allows an objective assessment of regional myocardial function. Peak systolic velocity (PSV) and A-V plane displacement (AVPD) obtained from colour TDE correlate well with changes in cardiac wall motion and can discriminate ischemic areas during stress echocardiography. During exercise, the relationship between PSV and AVPD depends on several factors besides ischemia and should be considered when performing exercise stress echocardiography.

    AIMS:

    To investigate the relation between PSV, AVPD and heart rate (HR) during semi-upright exercise with and without beta-blockade.

    SUBJECTS AND METHODS:

    Twelve healthy men underwent semi-upright exercise stress echocardiography with and without beta-blockade on two separate occasions. Standard echocardiographic projections were used for the stress echocardiography. Grey-scale echocardiographic pictures containing colour TDE information were obtained at rest and during a two-stage exercise test, and the images were analyzed off-line. The PSV and AVPD were measured at four points at the base of the left ventricle at the septum and lateral, inferior and anterior walls.

    RESULTS:

    PSV, AVPD and HR gradually increased during exercise. The increases in PSV and AVPD were linearly correlated with the increase in HR. The increases in PSV were significantly lower during exercise with beta-blockade than without beta-blockade (P<0.05). This was not observed in AVPD, as increments were not affected by beta-blockade.

    CONCLUSION:

    These data showing a relationship between HR and PSV, and a significantly lower PSV with beta-blockade at a given HR, suggest that PSV is influenced by HR and myocardial contractility, both of which are augmented by physical exercise-induced sympathetic stimulation.

  • 10. Rohdin, M
    et al.
    Petersson, J
    Sundblad, Patrik
    KTH, School of Technology and Health (STH), Environmental Physiology (Closed 20130701).
    Mure, M
    Glenny, RW
    Lindahl, SG
    Linnarsson, D
    Effects of gravity on lung diffusing capacity and cardiac output in prone and supine humans.2003In: Journal of applied physiology, ISSN 8750-7587, E-ISSN 1522-1601, Vol. 95, no 1, p. 3-10Article in journal (Refereed)
    Abstract [en]

    Both in normal subjects exposed to hypergravity and in patients with acute respiratory distress syndrome, there are increased hydrostatic pressure gradients down the lung. Also, both conditions show an impaired arterial oxygenation, which is less severe in the prone than in the supine posture. The aim of this study was to use hypergravity to further investigate the mechanisms behind the differences in arterial oxygenation between the prone and the supine posture. Ten healthy subjects were studied in a human centrifuge while exposed to 1 and 5 times normal gravity (1 G, 5 G) in the anterioposterior (supine) and posterioanterior (prone) direction. They performed one rebreathing maneuver after approximately 5 min at each G level and posture. Lung diffusing capacity decreased in hypergravity compared with 1 G (ANOVA, P = 0.002); it decreased by 46% in the supine posture compared with 25% in the prone (P = 0.01 for supine vs. prone). At the same time, functional residual capacity decreased by 33 and 23%, respectively (P < 0.001 for supine vs. prone), and cardiac output by 40 and 31% (P = 0.007 for supine vs. prone), despite an increase in heart rate of 16 and 28% (P < 0.001 for supine vs. prone), respectively. The finding of a more impaired diffusing capacity in the supine posture compared with the prone at 5 G supports our previous observations of more severe arterial hypoxemia in the supine posture during hypergravity. A reduced pulmonary-capillary blood flow and a reduced estimated alveolar volume can explain most of the reduction in diffusing capacity when supine.

  • 11.
    Rohdin, M.
    et al.
    Karolinska Institutet.
    Sundblad, Patrik
    Karolinska Institutet, Sweden.
    Linnarsson, D.
    Karolinska Institutet.
    Effects of hypergravity on the distributions of lung ventilation and perfusion in sitting humans assessed with a simple two-step maneuver2004In: Journal of applied physiology, ISSN 8750-7587, E-ISSN 1522-1601, Vol. 96, no 4, p. 1470-1477Article in journal (Refereed)
    Abstract [en]

    Increased gravity impairs pulmonary distributions of ventilation and perfusion. We sought to develop a method for rapid, simultaneous, and noninvasive assessments of ventilation and perfusion distributions during a short-duration hypergravity exposure. Nine sitting subjects were exposed to one, two, and three times normal gravity (1, 2, and 3 G) in the head-to-feet direction and performed a rebreathing and a single-breath washout maneuver with a gas mixture containing C(2)H(2), O(2), and Ar. Expirograms were analyzed for cardiogenic oscillations (COS) and for phase IV amplitude to analyze inhomogeneities in ventilation (Ar) and perfusion [CO(2)-to-Ar ratio (CO(2)/Ar)] distribution, respectively. COS were normalized for changes in stroke volume. COS for Ar increased from 1-G control to 128 +/- 6% (mean +/- SE) at 2 G (P = 0.02 for 1 vs. 2 G) and 165 +/- 13% at 3 G (P = 0.002 for 2 vs. 3 G). Corresponding values for CO(2)/Ar were 135 +/- 12% (P = 0.04) and 146 +/- 13%. Phase IV amplitude for Ar increased to 193 +/- 39% (P = 0.008) at 2 G and 229 +/- 51% at 3 G compared with 1 G. Corresponding values for CO(2)/Ar were 188 +/- 29% (P = 0.02) and 219 +/- 18%. We conclude that not only large-scale ventilation and perfusion inhomogeneities, as reflected by phase IV amplitude, but also smaller-scale inhomogeneities, as reflected by the ratio of COS to stroke volume, increase with hypergravity. Except for small-scale ventilation distribution, most of the impairments observed at 3 G had been attained at 2 G. For some of the parameters and gravity levels, previous comparable data support the present simplified method.

  • 12.
    Rundqvist, Helene
    et al.
    Karolinska Institutet.
    Rullman, Eric
    Karolinska Institutet.
    Sundberg, Carl Johan
    Karolinska Institutet.
    Fischer, Helene
    Karolinska Institutet.
    Eisleithner, Katarina
    Karolinska Institutet.
    Ståhlberg, Marcus
    Karolinska Institutet.
    Sundblad, Patrik
    Karolinska Institutet, Sweden.
    Jansson, Eva
    Karolinska Institutet.
    Gustafsson, Thomas
    Karolinska Institutet.
    Activation of the erythropoietin receptor in human skeletal muscle2009In: European Journal of Endocrinology, ISSN 0804-4643, E-ISSN 1479-683X, Vol. 161, no 3, p. 427-434Article in journal (Refereed)
    Abstract [en]

    Objective: Erythropoietin receptor (EPOR) expression in non-hematological tissues has been shown to be activated by locally produced and/or systemically delivered EPO. Improved oxygen homeostasis, a well-established consequence of EPOR activation, is very important for human skeletal muscle performance. In the present study we investigate whether human skeletal muscle fibers and satellite cells express EPOR and if it is activated by exercise. Design and methods: Ten healthy males performed 65 min of cycle exercise. Biopsies were obtained from the vastus lateralis muscle and femoral arterio-venous differences in EPO concentrations were estimated. Results: The EPOR proteinwas localized in areas corresponding to the sarcolemma and capillaries. Laser dissection identified EPOR mRNA expression in muscle fibers. Also, EPOR mRNA and protein were both detected in human skeletal muscle satellite cells. In the initial part of the exercise bout there was a release of EPO from the exercising leg to the circulation, possibly corresponding to an increased bioavailability of EPO. After exercise, EPOR mRNA and EPOR-associated JAK2 phosphorylation were increased. Conclusions: Interaction with JAK2 is required for EPOR signaling and the increase found in phosphorylation is therefore closely linked to the activation of EPOR. The receptor activation by acute exercise suggests that signaling through EPOR is involved in exercise-induced skeletal muscle adaptation, thus extending the biological role of EPO into the skeletal muscle.

  • 13.
    Spaak, J
    et al.
    Karolinska Institutet.
    Montmerle, S
    Karolinska Institutet.
    Sundblad, Patrik
    Karolinska Institutet.
    Linnarsson, D
    Karolinska Institutet.
    Long-term bed rest-induced reductions in stroke volume during rest and exercise: cardiac dysfunction vs. volume depletion2005In: Journal of applied physiology, ISSN 8750-7587, E-ISSN 1522-1601, Vol. 98, no 2, p. 648-654Article in journal (Refereed)
    Abstract [en]

    Long-term head-down-tilt bed rest (HDT) causes cardiovascular deconditioning, attributed to reflex dysfunctions, plasma volume reduction, or cardiac impairments. Our objective with the present study was to evaluate the functional importance and relative contribution of these during rest and exercise in supine and upright postures. We studied six subjects before (baseline), during [days 60 (D60) and 113 (D113)], and after [recovery days 0 (R0), 3 (R3), and 15 (R15)] 120 days of -6 degrees HDT. We determined cardiac output, stroke volume (SV), mean arterial pressure, and heart rate during rest and exercise in supine and upright postures. Cardiac output and SV decreased significantly in all four conditions, but the time courses differed for rest and exercise. Upright resting SV was decreased by 24 +/- 9% at D60 compared with baseline but had recovered already at R3. Supine exercise SV decreased more slowly (by 5 +/- 8% at D60 and by 18 +/- 4% at D113) and recovered more slowly after HDT termination. Steady-state mean arterial pressure showed no changes. Heart rate had increased by 18 +/- 4% at D60 and had recovered partially at R3. Our data indicate that long-term HDT causes both a rapid, preload-dependent reduction in SV, most evident during rest in the upright position, and a more slowly developing cardiac dysfunction, most evident during supine exercise. However, the ability to maintain blood pressure and to perform sustained low levels of dynamic exercise is not influenced by HDT.

  • 14. Spaak, J
    et al.
    Sundblad, Patrik
    KTH, School of Technology and Health (STH), Environmental Physiology (Closed 20130701).
    Linnarsson, D
    Human carotid baroreflex during isometric lower arm contraction and ischemia.1998In: American Journal of Physiology, ISSN 0002-9513, E-ISSN 2163-5773, Vol. 275, no 3 Pt 2, p. H940-945Article in journal (Refereed)
    Abstract [en]

    Our aim was to determine the roles of somatomotor activation and muscle ischemia for the tachycardia and hypertension of isometric arm contraction. Carotid-cardiac and carotid-mean arterial pressure (MAP) baroreflex response curves were determined in 10 men during rest, during isometric arm contraction at 30% of maximum, and during postcontraction ischemia. Carotid distending pressure (CDP) was changed by applying pressure and suction in a neck chamber. Pressures ranged from +40 to -80 mmHg and were applied repeatedly for 15 s during the three conditions. Maximum slopes and ranges of the response curves did not differ among conditions. The heart rate (HR) curve was shifted to a 14 +/- 1.8 (mean +/- SE) beats/min higher HR and a 9 +/- 5.7 mmHg higher CDP during contraction and to a 14 +/- 5.9 mmHg higher CDP during postcontraction ischemia with no change of HR compared with rest. The MAP curve was shifted to a 20 +/- 2.8 mmHg higher MAP and to a 18 +/- 5.4 mmHg higher CDP during contraction, and the same shifts were recorded during postcontraction ischemia. We conclude that neither somatomotor activation nor muscle ischemia changes the sensitivity of arterial baroreflexes. The upward shift of the MAP response curve, with no shift of the HR response curve during postexercise ischemia, supports the notion of parallel pathways for MAP and HR regulation in which HR responses are entirely caused by somatomotor activation and the pressor response is mainly caused by muscle ischemia.

  • 15. Spaak, J
    et al.
    Sundblad, Patrik
    KTH, School of Technology and Health (STH), Environmental Physiology (Closed 20130701).
    Linnarsson, D
    Impaired pressor response after spaceflight and bed rest: evidence for cardiovascular dysfunction.2001In: European Journal of Applied Physiology, ISSN 1439-6319, E-ISSN 1439-6327, Vol. 85, no 1-2, p. 49-55Article in journal (Refereed)
    Abstract [en]

    We hypothesized that impaired cardiovascular responses to isometric muscle action contribute to the cardiovascular deconditioning that occurs after space flight (SF) and head-down-tilt bed rest (HDT). Six subjects were studied before, during and after 120 days of -6 degrees HDT, and four subjects were studied before, during (two subjects) and after 179-389 days of SF. Subjects performed a sustained handgrip (SHG) at a force equivalent to 30% of maximum contraction force for 2 min, and heart-rate (HR) and pressor (mean arterial pressure, deltaMAP) responses were recorded. At the same relative force, both deltaHR and deltaMAP were significantly reduced during the first days after HDT (-54%, P<0.05 and -43%, P<0.05). In two subjects studied within 24 h after their return from SF, deltaMAP was practically absent (-79%, P<0.05) whereas in four subjects studied 1-4 days after return from SF, deltaMAP was reduced by 35% (P<0.05). deltaHR was not significantly changed. Our finding of attenuated pressor responses to SHG after HDT and SF supports the notion of impairments at both the neurocirculatory control and effector organ levels.

  • 16.
    Sundblad, Patrik
    et al.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology. KTH, School of Technology and Health (STH), Centres, Swedish Aerospace Physiology Centre, SAPC.
    Franberg, Oskar
    Siebenmann, Christoph
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology. KTH, School of Technology and Health (STH), Centres, Swedish Aerospace Physiology Centre, SAPC.
    Gennser, Mikael
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology. KTH, School of Technology and Health (STH), Centres, Swedish Aerospace Physiology Centre, SAPC.
    Measuring Uptake and Elimination of Nitrogen in Humans at Different Ambient Pressures2016In: Aerospace Medicine and Human Performance, ISSN 2375-6314, Vol. 87, no 12, p. 1045-1050Article in journal (Refereed)
    Abstract [en]

    BACKGROUND: To measure nitrogen (N-2) wash-out and uptake requires elaborate set-ups, especially when doing the measurements at increased or decreased ambient pressure. Here we present a transportable device for quantifying N-2 turnover in humans which can be used at different ambient pressures. METHODS: A modified close-circuit electronic rebreather was used to assess N-2 turnover. Changes in N-2 volume within the rebreathing circuit, reflecting N-2 uptake or washout, were derived from the continuously monitored total system volume and the calculated volumes of oxygen and water vapor. The calculation of continuous N-2 volume curves was performed off-line using dedicated computer software. RESULTS: Four subjects participated in the proof-of-concept tests. At steady state, the drift in calculated N-2 volume in the rebreathing circuit over a 1-h duration was minimal. Three of the subjects participated in additional N-2 steady-state measurements where 1019 mL (BTPD) of N-2 was injected into the rebreathing circuit over 20 min and the measured volume increase was 1006 +/- 32 mL. Lastly, N-2 elimination was assessed during decompression to 0.5 atm and while breathing hyperoxic gas. N-2 uptake was measured during compression to 1.8 atm. The elimination and uptake curves were deemed to be realistic. DISCUSSION: A method for assessing N-2 turnover in humans has been developed and a first evaluation has been performed. It is easy to work with operationally and can be used at different ambient pressures. More research is needed in order to further validate it as a method for assessing N-2 turnover in humans.

  • 17.
    Sundblad, Patrik
    et al.
    KTH, School of Technology and Health (STH), Environmental Physiology (Closed 20130701).
    Haruna, Y
    Tedner, B
    Linnarsson, D
    Short-term cardiovascular responses to rapid whole-body tilting during exercise.2000In: European Journal of Applied Physiology, ISSN 1439-6319, E-ISSN 1439-6327, Vol. 81, no 4, p. 259-270Article in journal (Refereed)
    Abstract [en]

    Our objective was to characterize the responses of heart rate (HR) and arterial blood pressure (BP) to changes in posture during concomitant dynamic leg exercise. Ten men performed dynamic leg exercise at 50, 100, and 150 W and were rapidly and repeatedly tilted between supine (0 degrees ) and upright (80 degrees ) positions at 2-min intervals. Continuous recordings of BP and HR were made, and changes in central blood volume were estimated from transthoracic impedance. Short-lasting increases in BP were observed immediately upon tilting from the upright to the supine position (down-tilt), averaging +18 mmHg (50 W) to +31 mmHg (150 W), and there were equally short-lasting decreases in BP, ranging from -26 to -38 mmHg upon tilting from supine to upright (up-tilt). These components occurred for all pressure parameters (systolic, mean, diastolic, and pulse pressures). We propose that these transients reflect mainly tilt-induced changes in total peripheral resistance resulting from decreases and increases of the efficiency of the venous muscle pump. After 3-4 s (down-tilt) and 7-11 s (up-tilt) there were large HR transients in a direction opposite to the pressure transients. These HR transients were larger during the down-tilt (-15 to -26 beats. min(-1)) than during the up-tilt (+13 to +17 beats. min(-1)), and increased in amplitude with work intensity during the down-tilt. The tilt-induced HR fluctuations could be modelled as a basically linear function of an arterial baroreflex input from a site half-way between the heart and the carotid sinus, and with varying contributions of fast vagal and slow sympathetic HR responses resulting in attenuated tachycardic responses to hypotensive stimuli during exercise.

  • 18.
    Sundblad, Patrik
    et al.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology. KTH, School of Technology and Health (STH), Centres, Swedish Aerospace Physiology Centre, SAPC.
    Kölegård, Roger
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology. KTH, School of Technology and Health (STH), Centres, Swedish Aerospace Physiology Centre, SAPC.
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology. KTH, School of Technology and Health (STH), Centres, Swedish Aerospace Physiology Centre, SAPC.
    G tolerance and the vasoconstrictor reserve2014In: European Journal of Applied Physiology, ISSN 1439-6319, E-ISSN 1439-6327, Vol. 114, no 12, p. 2521-2528Article in journal (Refereed)
    Abstract [en]

    Because leg arterial stiffness is higher in subjects with high G tolerance, we hypothesized that subjects with high G tolerance would have larger capacity for vasoconstriction. Sixteen subjects, eight with high and eight with low G tolerance (H and L group, respectively), were exposed to a cold pressor test (CPT) in supine and upright posture. Heart rate (HR), mean arterial pressure (MAP) and cardiac output (CO) were measured, and total peripheral resistance (TPR) and stroke volume (SV) were calculated. In the supine position, CPT increased TPR more in the H group; 31 +/- A 18 % than in the L group; 11 +/- A 7 % (p < 0.05). The L group had larger increases in CO than the H group; 17 +/- A 16 vs. 3.4 +/- A 7 % (p = 0.06). In the upright position, the H group had a larger MAP response to CPT than the L group; 26 +/- A 14 vs. 14 +/- A 7 % (p = 0.06). The H group, but not the L group, had significant increases in TPR whereas the L group had significant increases in CO and SV. In response to CPT, the high G tolerance group elevated MAP by increasing TPR, whereas the low G tolerance group showed a dependency on increased CO. The H group seemed to have a larger vasoconstrictor reserve. The results further suggest that vasoconstrictor reserve capacity could constitute the link between the recent finding that indicates a relationship between G tolerance and arterial distensibility in the legs.

  • 19.
    Sundblad, Patrik
    et al.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology. KTH, School of Technology and Health (STH), Centres, Swedish Aerospace Physiology Centre, SAPC.
    Kölegård, Roger
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology. KTH, School of Technology and Health (STH), Centres, Swedish Aerospace Physiology Centre, SAPC.
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology. KTH, School of Technology and Health (STH), Centres, Swedish Aerospace Physiology Centre, SAPC.
    Passiv G-tolerans; kardiovaskulära omställningar under G-belastning vis-a-vis under cold-pressor test samt stimulering av arteriella baroreceptorer2014Conference paper (Refereed)
  • 20.
    Sundblad, Patrik
    et al.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Kölegård, Roger
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Migeotte, P. -F
    Delière, Q.
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    The arterial baroreflex and inherent G tolerance2016In: European Journal of Applied Physiology, ISSN 1439-6319, E-ISSN 1439-6327, p. 1-9Article in journal (Refereed)
    Abstract [en]

    Purpose: High G tolerance is based on the capacity to maintain a sufficient level of arterial pressure (AP) during G load; therefore, we hypothesized that subjects with high G tolerance (H group) would have stronger arterial baroreflex responses compared to subjects with low G tolerance (L group). The carotid baroreflex was evaluated using the neck pressure method (NP), which assesses open-loop responses. Methods: The carotid baroreflex was tested in 16 subjects, n = 8 in the H and L group, respectively, in the supine and upright posture. Heart rate and AP were measured. Results: There were no differences between groups in the maximum slopes of the carotid baroreflex curves. However, the H group had a larger systolic and mean AP (SAP, MAP) increase to the initial hypotensive stimuli of the NP sequence in the upright position compared to the L group, 7.5 ± 6.6 vs 2.0 ± 2.4 and 4.1 ± 3.4 vs 1.1 ± 1.1 mmHg for SAP and MAP, respectively. Furthermore, the L group exhibited an increased latency between stimuli and response in AP in the upright compared to supine position, 4.1 ± 1.0 vs 3.1 ± 0.9 and 4.7 ± 1.1 vs 3.6 ± 0.9 s, for SAP and MAP. No differences in chronotropic responses were observed between the groups. Conclusions: It is concluded that the capacity for reflexive vasoconstriction and maintained speed of the vascular baroreflex during orthostatic stress are coupled to a higher relaxed GOR tolerance.

  • 21.
    Sundblad, Patrik
    et al.
    Karolinska Inst, Dept Lab Med, Clin Physiol, SE-14186 Stockholm, Sweden.;Karolinska Univ Hosp, Dept Clin Physiol, SE-14186 Stockholm, Sweden..
    Kölegård, Roger
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Environmental Physiology.
    Rullman, Eric
    Karolinska Inst, Dept Lab Med, Clin Physiol, SE-14186 Stockholm, Sweden.;Karolinska Univ Hosp, Dept Clin Physiol, SE-14186 Stockholm, Sweden..
    Gustafsson, Thomas
    Karolinska Inst, Dept Lab Med, Clin Physiol, SE-14186 Stockholm, Sweden.;Karolinska Univ Hosp, Dept Clin Physiol, SE-14186 Stockholm, Sweden..
    Effects of training with flow restriction on the exercise pressor reflex2018In: European Journal of Applied Physiology, ISSN 1439-6319, E-ISSN 1439-6327, Vol. 118, no 9, p. 1903-1909Article in journal (Refereed)
    Abstract [en]

    We hypothesized that 5 weeks of endurance training with blood flow restriction (R-training), providing relative ischemia and stimulation of the muscle chemoreflex, would decrease the exercise pressor reflex (EPR) when compared to training with the same workload in a free-flow condition (NR-training). 10 subjects performed one-leg knee-extension training four times a week during a 5-week period. Both legs were trained with identical workload, with one leg being trained during flow-restriction induced by lower body positive pressure. The EPR was assessed by measuring the increase in heart rate (HR) and mean arterial pressure (MAP) during an isometric knee extension of 35% of max torque for 90 s, this was done before (C), and after training in each leg (R and NR, respectively). At the end of isometric contraction, the increase in mean AP (MAP) in the NR-trained leg and in the control condition were 41 +/- 4 and 38 +/- 4 mmHg, respectively, whereas the increase in the R-trained leg was 30 +/- 4 mmHg (p < 0.05 R vs C and NR), corresponding to a decrease of about 25%. A similar patter was observed with respect to responses in HR, where the increase was 28 +/- 3 and 28 +/- 3 bpm in the NR and C, and 22 +/- 4 in the R condition (p < 0.05 R vs C and NR). Peripheral metabolic changes induced by relative ischemia are important in modifying the EPR in response to exercise training.

  • 22.
    Sundblad, Patrik
    et al.
    KTH, School of Technology and Health (STH), Environmental Physiology (Closed 20130701).
    Linnarsson, D
    Influence of apnea on cardiovascular responses to neck suction during exercise.1996In: American Journal of Physiology, ISSN 0002-9513, E-ISSN 2163-5773, Vol. 271, no 4 Pt 2, p. H1370-1374Article in journal (Refereed)
    Abstract [en]

    Short-lasting neck suction (NS) is a common method to assess the carotid-cardiac baroreflex, and NS is usually applied during apnea to avoid breath-synchronous variations of heart rate (HR) and blood pressure. We hypothesized that the apnea might provoke cardiovascular effects that could confound the HR and blood pressure responses to NS. HR and blood pressure responses to 10-s trains of 50-mmHg pulses of NS were studied in six male subjects during supine rest, upright rest, isometric arm exercise at 30% of maximal voluntary contraction, and dynamic leg exercise at 100 W in the sitting position. Repeated NS sequences were performed during apnea preceded by a relaxed expiration to functional residual capacity and during eupnea. Initial HR responses to NS were similar during eupnea and apnea in all conditions. However, during isometric and dynamic exercise, recordings made under eupneic and apneic conditions differed during the second half of the NS period. During apneic isometric arm contraction, the elevation of mean carotid distending pressure (MCDP) (arterial pressure at carotid level minus NS pressure) was maintained at a 25-35% higher level than during eupneic isometric exercise over the last half of the NS period. In dynamic exercise, mean arterial pressure and MCDP started to increase after 3-5 s of apneic NS, whereas they were maintained during eupnea. One to three seconds later, HR started to drop markedly in apneic subjects, reaching values 20 beats/min lower than those in eupneic subjects at the end of the NS. We conclude that cardiovascular effects of apnea may appear after only 8 s of apnea in dynamic exercise and therefore could confound responses to NS.

  • 23.
    Sundblad, Patrik
    et al.
    KTH, School of Technology and Health (STH), Environmental Physiology (Closed 20130701).
    Linnarsson, D
    Relationship between breath-synchronous arterial pressure and heart rate variations during orthostatic stress.2003In: Clinical Physiology and Functional Imaging, ISSN 1475-0961, E-ISSN 1475-097X, Vol. 23, no 2, p. 103-109Article in journal (Refereed)
    Abstract [en]

    It has recently been shown that the phase relationship between respiration-induced changes in arterial pressure (AP) and heart rate (HR) are different in supine and upright postures. We wanted to further analyse the coupling between respiration, arterial blood pressure and HR in the time domain, and how this coupling was altered during orthostatic stress. Nine healthy subjects were studied. Respiration-induced changes in AP and HR were recorded during frequency- and volume-controlled breathing. This was done during supine rest with and without lower body negative pressure (-50 mmHg) (LBNP). All experiments were performed after beta1-blockade. Responses were averaged breath-by-breath to enhance the time resolution and to eliminate noise. The respiration-induced changes in arterial pulse pressure (PP) were different between control and LBNP: The peak in PP during the respiratory cycle occurred 0.9 +/- 0.8 (mean +/- SD) s before the onset of inspiration during supine control and 0.8 +/- 2.1 s after the onset of inspiration during LBNP (P = 0.03). These changes in the timing of peak PP significantly distorted the cyclic systolic AP and mean AP fluctuations during LBNP. Despite the altered AP response with LBNP, HR fluctuations closely correlated in time with respiration in all conditions, albeit with a significantly reduced amplitude during LBNP (-49%, P = 0.01). The results points to a lack of coupling between AP and HR during paced breathing and thus suggest that respiratory sinus dysrhythmia at least, to a large extent, is independent of the arterial baroreflex.

  • 24.
    Sundblad, Patrik
    et al.
    KTH, School of Technology and Health (STH), Environmental Physiology (Closed 20130701).
    Linnarsson, D
    Slowing of carotid-cardiac baroreflex with standing and with isometric and dynamic muscle activity.1996In: American Journal of Physiology, ISSN 0002-9513, E-ISSN 2163-5773, Vol. 271, no 4 Pt 2, p. H1363-1369Article in journal (Refereed)
    Abstract [en]

    We hypothesized that the carotid-cardiac baroreflex becomes slowed in conditions with increased sympathetic activity. Changes in heart rate (HR) and blood pressure in response to 10-s trains of 50-mmHg pulses of neck suction (NS) were studied in six male subjects during supine rest, upright rest, isometric arm exercise at 30% of maximum voluntary contraction, and dynamic leg exercise at 100 W in the sitting position. Estimated mean carotid distending pressure increased by approximately 20 mmHg with 50-mmHg, QRS-triggered, pulsatile NS. Repeated NS sequences were performed in each condition. The amplitude of the bradycardic response was highly variable among the subjects and did not differ significantly between conditions, mean values ranging from 0.3 to 0.6 beats.min-1.mmHg-1. In supine rest, the full bradycardic response appeared within < 1 s, i.e., during or immediately after the R-R interval of the first NS pulse. In the other conditions it took significantly longer, 2-3 s or three to seven R-R intervals, for the full HR responses to develop. Our results support the notion that the carotid-cardiac baroreflex in humans becomes slowed under conditions of concurrent sympathetic stimulation.

  • 25.
    Sundblad, Patrik
    et al.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology. Swedish Aerospace Physiology Center.
    Orlov, O
    Guidelines for Standardization of Bed Rest Studies in the Spaceflight Context.2015Report (Other academic)
  • 26.
    Sundblad, Patrik
    et al.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Orlov, O
    Angerer, O
    Larina, IM
    Cromwell, R
    Standardization of Bed Rest Studies in the Spaceflight Context.2016In: Journal of applied physiology, ISSN 8750-7587, E-ISSN 1522-1601, Vol. 121, no 1, p. 348-349Article in journal (Refereed)
  • 27.
    Sundblad, Patrik
    et al.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Prisk, G. Kim
    Something from nothing?: Space research without leaving the planet2016In: Journal of applied physiology, ISSN 8750-7587, E-ISSN 1522-1601, Vol. 120, no 8, p. 889-890Article in journal (Other academic)
  • 28.
    Sundblad, Patrik
    et al.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology. Department of Physiology and Pharmacology, Karolinska Institutet, Sweden .
    Spaak, J.
    Kaijser, L.
    Time courses of central hemodynamics during rapid changes in posture.2014In: Journal of applied physiology, ISSN 8750-7587, E-ISSN 1522-1601, Vol. 116, no 9, p. 1182-1188Article in journal (Refereed)
    Abstract [en]

    Changes in posture cause blood volume redistribution, affecting cardiac filling and stroke volume (SV). We hypothesized that the time courses of ventricular filling would differ between the right and left ventricle during a rapid (2 s) tilt and that changes in right ventricular filling pressure would be more swift because of the direct coupling to the systemic circulation. We further hypothesized that the transient imbalance between right and left ventricular filling pressure would influence left ventricular SV changes. Right atrial pressure (RAP), pulmonary capillary wedge pressure (PCWP), left ventricular stroke volume, heart rate, and arterial pressure were recorded beat-by-beat during rapid tilts from supine to upright positions and back again, during rest and dynamic 100-W leg exercise. RAP changes had a faster time course than PCWP during down-tilts, both during rest and exercise (1 +/- 1 vs. 6 +/- 2 s and 2 +/- 2 vs. 6 +/- 2 s, respectively; P < 0.05). This discrepancy caused a transient decrease in the end-diastolic pressure difference between the right and left ventricle. The decreased pressure difference in diastole impeded left ventricular filling because of ventricular interdependence, causing SV to fall transiently. The mechanisms of ventricular interdependence were also involved in reverse during up-tilt, where SV was maintained for 2-3 s despite falling PCWP. Furthermore, the decrease in RAP during up-tilt in the resting condition was biphasic with an initial fast and a second slower component, which might suggest the effect of venous valves. This was not seen during dynamic leg exercise where blood pooling is prevented by the venous muscle pump.

  • 29.
    Sundblad, Patrik
    et al.
    KTH, School of Technology and Health (STH), Environmental Physiology (Closed 20130701).
    Spaak, J
    Linnarsson, D
    Cardiovascular responses to upright and supine exercise in humans after 6 weeks of head-down tilt (-6 degrees).2000In: European Journal of Applied Physiology, ISSN 1439-6319, E-ISSN 1439-6327, Vol. 83, no 4-5, p. 303-309Article in journal (Refereed)
    Abstract [en]

    Seven healthy men performed steady-state dynamic leg exercise at 50 W in supine and upright postures, before (control) and repeatedly after 42 days of strict head-down tilt (HDT) (-6 degrees) bedrest. Steady-state heart rate (fc), mean arterial blood pressure, cardiac output (Qc), and stroke volume (SV) were recorded. The following data changed significantly from control values. The fc was elevated in both postures at least until 12 days, but not at 32 days after bedrest. Immediately after HDT, SV and Qc were decreased by 25 (SEM 3)% and 19 (SEM 3)% in supine, and by 33 (SEM 5)% and 20 (SEM 3)% in upright postures, respectively. Within 2 days there was a partial recovery of SV in the upright but not in the supine posture. The SV and Qc during supine exercise remained significantly decreased for at least a month. Submaximal oxygen uptake did not change after HDT. We concluded that the cardiovascular response to exercise after prolonged bedrest was impaired for so long that it suggested that structural cardiac changes had developed during the HDT period.

  • 30.
    Sundblad, Patrik
    et al.
    KTH, School of Technology and Health (STH), Environmental Physiology (Closed 20130701).
    Spaak, J
    Linnarsson, D
    Haemodynamic and baroreflex responses to whole-body tilting in exercising men before and after 6 weeks of bedrest.2000In: European Journal of Applied Physiology, ISSN 1439-6319, E-ISSN 1439-6327, Vol. 82, no 5-6, p. 397-406Article in journal (Refereed)
    Abstract [en]

    We sought to determine whether the cardiovascular deconditioning that occurs in exercising men after prolonged (42 days) bedrest in the head-down tilt (HDT) position is primarily related to mechanical changes in the heart or to an impaired arterial-cardiacchronotropic baroreflex. Seven subjects were studied before (C, control) and repeatedly after HDT with rapid tilting between the upright and supine positions during steady-state 50-W dynamic leg exercise. Ventricular interdependence was assumed to be an index of cardiac size; it was assessed on the basis of the initial dip of arterial pulse pressure (PP) induced by a sudden tilt from the upright to the supine position (down-tilt). Arterialcardiac-chronotropic baroreflex sensitivity (ABS) was assessed as the ratio between tilt-induced heart rate transients and the preceding (and reciprocal) transient in arterial pressure. On the first day of recovery, the initial PP dip was -4 (2) mmHg (where 1 mmHg is 0.13 kPa), less than half of the control value; on subsequent recovery days, the initial PP dip was not significantly different from the control value. When tilting from the upright to the supine position, mean ABS ranged from 1.02 to 1.06 bpm/mmHg during three separate control sessions. Tilts in the opposite direction gave lower ABS values because of the more sluggish HR response and ranged from 0.43 to 0.45 bpm/mmHg in the control situations. ABS did not change after HDT. Our results indicate that impairments of the cardiovascular system after long-term bedrest are of haemodynamic rather than baroreflex origin.

  • 31.
    Sundblad, Patrik
    et al.
    KTH, School of Technology and Health (STH), Environmental Physiology (Closed 20130701).
    Wranne, B
    Influence of posture on left ventricular long- and short-axis shortening.2002In: American Journal of Physiology. Heart and Circulatory Physiology, ISSN 0363-6135, E-ISSN 1522-1539, Vol. 283, no 4, p. H1302-1306Article in journal (Refereed)
    Abstract [en]

    End-diastolic volume and left ventricular stroke volume are increased in the supine compared with upright position, but the contribution of long-axis (LAS) and short-axis shortening (SAS) to these changes with change in posture has not been established. We examined long- and short-axis motion and dimensions with echocardiography in 10 healthy subjects in the upright and supine position. Long-axis length at end diastole was almost identical, whereas the diastolic short-axis diameter was increased in the supine position. At end systole, there was a decreased long-axis length and increased short-axis length in the supine vs. upright position. Both LAS and SAS were enhanced in supine vs. upright positions [LAS: 9.3 +/- 2.2 vs. 15.1 +/- 3.1 mm (P < 0.001); SAS: 12.7 +/- 3.2 vs. 16.3 +/- 2.8 mm (P < 0.001)], presumably via Starling mechanisms. LAS increased more in the lateral part of the mitral annulus than in the septal part [7.7 +/- 2.6 vs. 4.0 +/- 2.8 mm (P < 0.006)], which implies that the more spherical form, in the supine position, induces more stretch at the lateral free wall than in the ventricular septum. These findings support the notion that Starling mechanisms affect systolic LAS.

  • 32.
    Zhao, Wei
    et al.
    Ericsson Research.
    Andersson, Loa
    Ericsson AB.
    Sköldström, Pontus
    Acreo AB.
    Prototyping MPLS-TP forwarding and OAM2009In: 5th International Conference on IP + Optical Network, 2009Conference paper (Refereed)
  • 33.
    Ånell, Rickard
    et al.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Grönkvist, Mikael
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Sundblad, Patrik
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Gennser, Mikael
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Vaskulära gasbubblor hos jaktplanspiloter under olika flygprofiler2016Conference paper (Refereed)
1 - 33 of 33
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