The underwater environment: cardiopulmonary, thermal, and energetic demands

2009 ◽  
Vol 106 (1) ◽  
pp. 276-283 ◽  
Author(s):  
D. R. Pendergast ◽  
C. E. G. Lundgren
Keyword(s):  
Blood Pressure ◽  
Blood Flow ◽  
Cardiac Output ◽  
Stroke Volume ◽  
Time Dependent ◽  
Breath Holding ◽  
Peripheral Blood Flow ◽  
Short Term ◽  
Underwater Environment ◽  
Maximal Cardiac Output

Water covers over 75% of the earth, has a wide variety of depths and temperatures, and holds a great deal of the earth's resources. The challenges of the underwater environment are underappreciated and more short term compared with those of space travel. Immersion in water alters the cardio-endocrine-renal axis as there is an immediate translocation of blood to the heart and a slower autotransfusion of fluid from the cells to the vascular compartment. Both of these changes result in an increase in stroke volume and cardiac output. The stretch of the atrium and transient increase in blood pressure cause both endocrine and autonomic changes, which in the short term return plasma volume to control levels and decrease total peripheral resistance and thus regulate blood pressure. The reduced sympathetic nerve activity has effects on arteriolar resistance, resulting in hyperperfusion of some tissues, which for specific tissues is time dependent. The increased central blood volume results in increased pulmonary artery pressure and a decline in vital capacity. The effect of increased hydrostatic pressure due to the depth of submersion does not affect stroke volume; however, a bradycardia results in decreased cardiac output, which is further reduced during breath holding. Hydrostatic compression, however, leads to elastic loading of the chest wall and negative pressure breathing. The depth-dependent increased work of breathing leads to augmented respiratory muscle blood flow. The blood flow is increased to all lung zones with some improvement in the ventilation-perfusion relationship. The cardiac-renal responses are time dependent; however, the increased stroke volume and cardiac output are, during head-out immersion, sustained for at least hours. Changes in water temperature do not affect resting cardiac output; however, maximal cardiac output is reduced, as is peripheral blood flow, which results in reduced maximal exercise performance. In the cold, maximal cardiac output is reduced and skin and muscle are vasoconstricted, resulting in a further reduction in exercise capacity.

Cardiac Output Changes in Newborns With Hyperbilirubinemia Treated With Phototherapy

PEDIATRICS ◽  
1985 ◽  
Vol 76 (6) ◽  
pp. 918-921
Author(s):  
Frans J. Walther ◽  
Paul Y. K. Wu ◽  
Bijan Siassi
Keyword(s):  
Blood Flow ◽  
Cardiac Output ◽  
Stroke Volume ◽  
Skin Blood Flow ◽  
Peripheral Blood ◽  
Cardiovascular Effects ◽  
Tissue Perfusion ◽  
Peripheral Blood Flow ◽  
Limb Blood Flow ◽  
Term Infants

Phototherapy is known to increase peripheral blood flow in neonates, but information on the associated cardiovascular effects is not available. Using pulsed Doppler echocardiography we evaluated cardiac output and stroke volume in 12 preterm and 13 term neonates during and after phototherapy. We concomitantly measured arterial limb blood flow by strain gauge plethysmography and skin blood flow by photoplethysmography. Cardiac output decreased by 6% due to reduced stroke volume during phototherapy, whereas total limb blood flow and skin blood flow increased by 38% and 41%, respectively. Peripheral blood flow increments tended to be higher in the preterm than in the term infants. The reduced stroke volume during phototherapy may be an expression of reduced activity of the newborn during phototherapy. For healthy neonates the reduction in cardiac output is minimal, but for sick infants with reduced cardiac output, this reduction may further aggravate the decrease in tissue perfusion.

The human spleen as an erythrocyte reservoir in diving-related interventions

2002 ◽  
Vol 92 (5) ◽  
pp. 2071-2079 ◽  
Author(s):  
Kurt Espersen ◽  
Hans Frandsen ◽  
Torben Lorentzen ◽  
Inge-Lis Kanstrup ◽  
Niels J. Christensen
Keyword(s):  
Blood Pressure ◽  
Blood Flow ◽  
Indirect Method ◽  
Hemoglobin Concentration ◽  
Breath Holding ◽  
Breath Hold ◽  
Peripheral Blood Flow ◽  
Diving Response ◽  
Human Spleen ◽  
The Face

Twelve subjects without and ten subjects with diving experience performed short diving-related interventions. After labeling of erythrocytes, scintigraphic measurements were continuously performed during these interventions. All interventions elicited a graduated and reproducible splenic contraction, depending on the type, severity, and duration of the interventions. The splenic contraction varied between ∼10% for “apnea” (breath holding for 30 s) and “cold clothes” (cold and wet clothes applied on the face with no breath holding for 30 s) and ∼30–40% for “simulated diving” (simulated breath-hold diving for 30 s), “maximal apnea” (breath holding for maximal duration), and “maximal simulated diving” (simulated breath-hold diving for maximal duration). The strongest interventions (simulated diving, maximal apnea, and maximal simulated diving) elicited modest but significant increases in hemoglobin concentration (0.1–0.3 mmol/l) and hematocrit (0.3–1%). By an indirect method, the splenic venous hematocrit was calculated to 79%. No major differences were observed between the two groups. The splenic contraction should, therefore, be included in the diving response on equal terms with bradycardia, decreased peripheral blood flow, and increased blood pressure.

scholarly journals Estimation of changes in instantaneous aortic blood flow by the analysis of arterial blood pressure

2012 ◽  
Vol 112 (11) ◽  
pp. 1832-1838 ◽  
Author(s):  
Tatsuya Arai ◽  
Kichang Lee ◽  
Robert P. Marini ◽  
Richard J. Cohen
Keyword(s):  
Blood Pressure ◽  
Blood Flow ◽  
Cardiac Output ◽  
Stroke Volume ◽  
Arterial Blood Pressure ◽  
Aortic Blood Flow ◽  
Windkessel Model ◽  
Arx Model ◽  
Arterial Blood ◽  
Aortic Blood

The purpose of this study was to introduce and validate a new algorithm to estimate instantaneous aortic blood flow (ABF) by mathematical analysis of arterial blood pressure (ABP) waveforms. The algorithm is based on an autoregressive with exogenous input (ARX) model. We applied this algorithm to diastolic ABP waveforms to estimate the autoregressive model coefficients by requiring the estimated diastolic flow to be zero. The algorithm incorporating the coefficients was then applied to the entire ABP signal to estimate ABF. The algorithm was applied to six Yorkshire swine data sets over a wide range of physiological conditions for validation. Quantitative measures of waveform shape (standard deviation, skewness, and kurtosis), as well as stroke volume and cardiac output from the estimated ABF, were computed. Values of these measures were compared with those obtained from ABF waveforms recorded using a Transonic aortic flow probe placed around the aortic root. The estimation errors were compared with those obtained using a windkessel model. The ARX model algorithm achieved significantly lower errors in the waveform measures, stroke volume, and cardiac output than those obtained using the windkessel model ( P < 0.05).

MATHEMATICAL MODELING OF STROKE VOLUME FROM THE PERIPHERAL BLOOD FLOW FOR NON INVASIVE PLETHYSMOGRAPHIC MEASUREMENT OF CARDIAC OUTPUT AND ITS VALIDATION

2017 ◽  
Vol 29 (06) ◽  
pp. 1750041
Author(s):  
Pranali Choudhari ◽  
M. S. Panse
Keyword(s):  
Blood Flow ◽  
Cardiac Output ◽  
Stroke Volume ◽  
Peripheral Blood ◽  
Clinical Medicine ◽  
Patient Specific ◽  
Peripheral Blood Flow ◽  
Lung Water ◽  
Non Invasive ◽  
Multiple Variable

The ability to accurately measure Cardiac Output (CO) is important in clinical medicine as it helps in improving diagnosis of abnormalities and appropriate disease management. In spite of being an important vital parameter, it is still missing from the screens of the bedside monitors employed today. This could be due to the invasiveness of the method or the discomfort in the measurement. Invasive methods are most accurate but can be best suited for the intensive care units (ICUs) and surgeries, but for bedside measurement these methods add an unnecessary risk to the life of the patient. The existing non-invasive method employed for CO measurement is the thoracic bioimpedance method, which is risky for patients with cardiovascular diseases and inaccurate for patients with extra vascular lung water. This paper presents a novel method of CO measurement from the peripheral blood flow, which fairly overcomes the disadvantages of the existing method. The impedance pulse has been acquired across the wrist, instead of the thorax. A new stroke volume equation has been modeled by carrying out the finite element simulation of the blood flow and multiple variable regression to incorporate the patient specific factors. The stroke volume thus obtained has been validated for 57 subjects.

scholarly journals Central hemodynamic and splanchnic circulation in children with meningococcal septic shock

2017 ◽  
Vol 8 (1) ◽  
pp. 91-97
Author(s):  
M. A. Georgiyants ◽  
V. A. Korsunov ◽  
O. M. Olkhovska
Keyword(s):  
Blood Pressure ◽  
Septic Shock ◽  
Blood Flow ◽  
Cardiac Output ◽  
Ejection Fraction ◽  
Stroke Volume ◽  
Blood Flow Rate ◽  
Healthy Children ◽  
Group I ◽  
Meningococcal Septic Shock

Meningococcal infection is caused by the bacterium Neisseria meningitidis (also termed meningococcus). Invasive meningococcal disease remains a rare infectious disease not only with high mortality but also with important morbidity and remains as a leading cause of sepsis and septic shock. The pathogenic mechanisms of microcirculatory disorders in meningococcal septic shock have been subject to controversy. This article presents the results of a study of 11 paediatric patients’ (4 boys and 7 girls) with meningococcal septic shock (Group I) who were hospitalized at the Regional Children's Infectious Hospital from 2009 to 2011. The average age of the patients was 37.4 ± 8.4 mo. Septic shock was diagnosed according to International Pediatric Sepsis Consensus Conference: definitions of criteria for sepsis and organ dysfunction in paediatrics. Heart rate, respiratory rate, systolic blood pressure, diastolic blood pressure, average blood pressure, SpO2 were monitored. The cardiac output, ejection fraction, fraction shortening, stroke volume were measured by ultrasound in M-mode by Teichholz method. Blood circulation in the a. mesenterica, a. hepatica, a. lienalis, a. renal sinister, v. porta, v. lienalis, v. renal sinister was determined by impulse Doppler’s wave. Acid-base and electrolytes level in serum, nitric oxide (NO), endothelin I, creatinine, C-reactivity protein and lactate blood level were measured. The control group consisted of 21 healthy children (9 boys and 12 girls), aged 37.5 ± 5.4 mo. in average (Group II). We used t-criteria (Student’s) and correlation with R-criteria (Spearmen) for statistical analysis. The data showed a statistically significant lower fraction of ejection, fraction of shortening, stroke volume in Group I. Moreover, our data showed a statistically high level of mesenterial and portal blood flow rate and high pulse index in v. renal sinister compared to healthy children. The blood level of NO was increased in Group I as well as in Group II. Direct correlations were determined between the level of NO and mesenteric, hepatic arterial and venous blood flow rate. Statistically significant inverse correlations between the level of NO and pulse resistive index in splanchnic vessels were discovered as well as inverse correlations between the NO level and the indicator of the severity of condition on PRISM scale (r = –0.952). At the same time, we have found no correlation between splanchnic circulation value and cardiac output. Based on the results of this study, we consider that NO has organ protective effects in children with meningococcal sepsis. Future research should aim to introduce new strategies of intensive care for patients with meningococcal septic shock with early use of inotrope and NO-donor therapy in fluid restriction combination. 

Cardiovascular changes associated with thermal polypnea in the chicken

1964 ◽  
Vol 207 (6) ◽  
pp. 1349-1353 ◽  
Author(s):  
G. C. Whittow ◽  
P. D. Sturkie ◽  
G. Stein
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Blood Flow ◽  
Cardiac Output ◽  
Stroke Volume ◽  
Respiratory Rate ◽  
Peripheral Resistance ◽  
Flow Through ◽  
Skin Temperatures ◽  
Increased Blood Flow

The effect of hyperthermia on the respiratory rate, cardiac output, blood pressure, arterial hematocrit, and the skin temperatures of the extremities of unanesthetized hens has been investigated. During hyperthermia, the respiratory rate increased to a maximal value and then declined. There was also an increase in cardiac output, followed by a decrease, but the peak cardiac output occurred at a rectal temperature which was significantly higher than that at which the peak respiratory rate was recorded. The increase in cardiac output was the result of an increase in both stroke volume and heart rate. The diminution of cardiac output seemed to be related to a decrease in the stroke volume at high levels of heart rate. The decrease in blood pressure and total peripheral resistance was attributed partly to an increased blood flow through the extremities.

The Blood Pressure of Giraffes

2021 ◽  
pp. 187-215
Author(s):  
Graham Mitchell
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Blood Flow ◽  
Cardiac Output ◽  
Hydrostatic Pressure ◽  
Left Ventricle ◽  
Stroke Volume ◽  
Body Mass ◽  
The Brain ◽  
Very High

As discussed in this chapter, giraffes have, compared with any other mammal, a very high mean blood pressure of ~250 mmHg. Human blood pressure is ~90 mmHg. Its size is determined by the length of the neck, the height of the head above the heart, by hydrostatic pressure generated by gravity acting on the column of blood in the carotid artery, and contractions of the heart muscles: blood pressure must be high enough to ensure that blood reaches the brain. Uniquely in giraffes blood pressure is regulated by receptors that are located in both the carotid and occipital arteries. Once thought to be ~2.5% of body mass the heart is smaller (~0.5% of body mass) but its muscle walls, especially of the interventricular wall and left ventricle wall, are exceptionally thick (up to 8 cm). The relative cardiac output is the same as in other mammals (~5 L 100 kg–1 of body mass) through a combination of a higher than predicted heart rate (70 b min–1 vs 50 b min–1) and smaller than predicted stroke volume (~0.7 ml kg–1 body mass vs 1.2 ml kg–1). Stroke volume is small because the left ventricle muscle wall is thick. The origin of high blood pressure is the resistance to blood flow, which is about twice what it is in other mammals. The higher resistance results from a combination of the thick muscular walls and narrow lumens of a giraffe’s blood vessels and unique mechanisms that regulate blood flow to the brain.

Peripheral Vascular Effects and Pharmacokinetics of the Antimigraine Compound, Zolmitriptan, in Combination with Oral Ergotamine in Healthy Volunteers

Cephalalgia ◽  
1997 ◽  
Vol 17 (6) ◽  
pp. 639-646 ◽  
Author(s):  
RM Dixon ◽  
HB Meire ◽  
DH Evans ◽  
H Watt ◽  
N On ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Blood Flow ◽  
Cardiac Output ◽  
Stroke Volume ◽  
Flow Velocity ◽  
Blood Flow Velocity ◽  
Systolic Pressure ◽  
Arterial Diameter ◽  
Vascular Effects ◽  
Double Blind

Members of the new class of antimigraine compounds, 5HT1B/1D agonists, as well as ergotamine, may cause vasoconstriction through stimulation of 5HT receptors on peripheral vessels. The cardiovascular effects of 20 mg oral zolmitriptan (Zomig, formerly 311C90), 2 mg oral ergotamine and the combination were assessed in a randomized double-blind, placebo-corirolled crossover study in 12 healthy subjects. Pharmacodynamic measures included oscillometric blood pressure, systolic blood pressure at the toe and arm using a strain gauge technique, stroke volume and cardiac output using bioimpedance cardiography, high-resolution ultrasound to measure brachial arterial diameter and a novel Doppler method to measure blood flow velocity. Both drugs produced small degrees of peripheral vasoconstriction, including increases in diastolic blood pressure and blood flow velocity and decreases in arterial diameter and toe-arm systolic pressure gradient. These effects were generally additive with the combination but of no clinical importance. There were no significant changes in cardiac output, stroke volume heart rate or ECG. Zolmitriptan, at eight times the likely therapeutic dose, was generally well tolerated both alone and in combination with ergotamine. Ergotamine had no clinically important effects on zolmitriptan pharmacokinetics. Ergotamine, migraine, peripheral vasculature, pharmacokinetics, zolmitriptan

Correlation of hemodynamic events during infusion of epinephrine in man

1962 ◽  
Vol 17 (1) ◽  
pp. 71-74 ◽  
Author(s):  
Michael J. Allwood ◽  
Ernst W. Keck ◽  
Robert J. Marshall ◽  
John T. Shepherd
Keyword(s):  
Blood Pressure ◽  
Blood Flow ◽  
Cardiac Output ◽  
Stroke Volume ◽  
Forearm Blood Flow ◽  
Muscle Blood Flow ◽  
Systemic Blood Pressure ◽  
Transient Phase ◽  
Systemic Blood ◽  
Muscle Groups

Changes in cardiac output, stroke volume, and systemic blood pressure have been correlated with changes in muscle blood flow during the periods of initial transient and subsequent sustamed vasodilatation during intravenous infusion of epinephrine. In the initial phase blood pressure decreased slightly; forearm blood flow increased by 308%, cardiac output by 50%, and stroke volume by 10%. During the sustained phase the systolic blood pressure increased; corresponding increases for the other measurements were 87, 47, and 25%, respectively. The lack of correlation between these changes in cardiac output and forearm blood flow suggests that in the transient phase vasodilatation does not occur simultaneously in all muscle groups. Stroke volume makes a greater contribution to the increased output during the sustained phase. Submitted on May 29, 1961

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