Heart–lung interactions

2020 ◽  
pp. 73-80
Author(s):  
Gulrukh Zaidi ◽  
Paul H. Mayo
Keyword(s):  
Critical Care ◽  
Stroke Volume ◽  
Cardiac Function ◽  
Transthoracic Echocardiography ◽  
Intrathoracic Pressure ◽  
Practical Method ◽  
Pressure Variation ◽  
Respiratory Cycle ◽  
Critical Care Echocardiography ◽  
Pulsed Wave Doppler

Echocardiography is the most clinically practical method of visualizing cardiac structures and directly observing changes of cardiac function during the respiratory cycle. This chapter will review heart–lung interactions and will focus on the effects of intrathoracic pressure variation on cardiac function that can be measured with advanced critical care echocardiography. These measurements are derived from observing respirophasic variation of stroke volume (SV) and help the intensivist to guide management of haemodynamic failure. The heart–lung interactions that occur with changes in intrathoracic pressure variation have utility in identification of preload sensitivity and adverse patient ventilator interaction. Measurement of the systolic velocity envelope with pulsed-wave Doppler is a requisite skill in order to identify SV variation, as is the recognition that the measurements may be difficult with transthoracic echocardiography.

Transesophageal Echocardiography

2019 ◽  
pp. 816-826
Author(s):  
Ryan C. Craner ◽  
Farouk Mookadam ◽  
Harish Ramakrishna
Keyword(s):  
Intensive Care Unit ◽  
Critical Care ◽  
Intensive Care ◽  
North America ◽  
Transesophageal Echocardiography ◽  
Transthoracic Echocardiography ◽  
Tertiary Care ◽  
Specialized Training ◽  
Critical Care Echocardiography ◽  
Tertiary Care Centers

The use of ultrasound has revolutionized care in the intensive care unit (ICU). The use of critical care echocardiography, including transthoracic echocardiography (TTE), has become commonplace in ICUs worldwide. In North America, however, intensivists rarely perform transesophageal echocardiography (TEE) unless they have anesthesiology training or have received specialized training to be competent in TEE. In many centers, neurology critical care is provided within the general ICU, and many tertiary-care centers have a dedicated ICU for specialized cases that require advanced and intensive neurologic care.

Determinants of cardiac augmentation by elevations in intrathoracic pressure

1985 ◽  
Vol 58 (4) ◽  
pp. 1189-1198 ◽  
Author(s):  
M. R. Pinsky ◽  
G. M. Matuschak ◽  
M. Klain
Keyword(s):  
Stroke Volume ◽  
Cardiac Function ◽  
Blood Volume ◽  
Intrathoracic Pressure ◽  
Left Ventricular ◽  
Filling Pressure ◽  
Respiratory Frequency ◽  
Stroke Work ◽  
Inspiratory Time ◽  
Ventricular Failure

We studied the cardiovascular effects of phasic increases in intrathoracic pressure (ITP) by high-frequency jet ventilation in an acute pentobarbital-anesthetized intact canine model both before and after the induction of acute ventricular failure by large doses of propranolol. Chest and abdominal pneumatic binders were used to further increase ITP. Respiratory frequency, percent inspiratory time, mean ITP, and swings in ITP throughout the respiratory cycle were independently varied at a constant-circulating blood volume. We found that pertubations in mean ITP induced by ventilator adjustments accounted for all observable steady-state hemodynamic changes independent of respiratory frequency, inspiratory time, or phasic respiratory swings in ITP. Changes in ITP were associated with reciprocal changes in both intrathoracic vascular pressures (P less than 0.01) and blood volume (P less than 0.01). When cardiac function was normal, left ventricular (LV) stroke volume decreased, whereas in acute ventricular failure, LV stroke volume increased in response to increasing ITP when apneic LV filling pressure was high (greater than or equal to 17 Torr) and did not change if apneic LV filling pressure was low (less than or equal to 12 Torr). However, in all animals in acute ventricular failure, LV stroke work increased with increasing ITP. Our study demonstrates that the improved cardiac function seen with increasing ITP in acute ventricular failure is dependent upon adequate LV filling and decreased LV afterload in a manner analogous to that seen with arterial vasodilator therapy in heart failure.

Oxford Textbook of Advanced Critical Care Echocardiography

2020 ◽  
Keyword(s):  
Critical Care ◽  
Critically Ill Patients ◽  
Transthoracic Echocardiography ◽  
Clinical Problem ◽  
Evidence Based ◽  
Clinical Use ◽  
Multiple Choice Questions ◽  
Critical Care Echocardiography ◽  
Reference Guide ◽  
Specific Assessment

This book is a physiological and evidence-based reference guide to the principles and techniques of advanced echocardiography. Both transoesophageal and transthoracic echocardiography are addressed, where appropriate. The foundations of advanced echocardiography are outlined in Part 1, preceding specific assessment methods of critical care echo which are demonstrated and discussed in Part 2. In reality, most critically ill patients do not suffer only one clinical problem, so Part 3 integrates techniques learned in Part 2 to answer both common and unexpected critical care questions. The future use of echocardiography in critical care is explored in Part 4. Important reference values for clinical use can be accessed easily in the appendices. An appendix includes videos, cases, and multiple-choice questions that can be used to reinforce understanding.

scholarly journals Influence of expiratory loading and hyperinflation on cardiac output during exercise

2004 ◽  
Vol 96 (5) ◽  
pp. 1920-1927 ◽  
Author(s):  
Kristy N. Stark-Leyva ◽  
Ken C. Beck ◽  
Bruce D. Johnson
Keyword(s):  
Cardiac Output ◽  
Stroke Volume ◽  
Cardiac Function ◽  
Healthy Subjects ◽  
Obstructive Lung Disease ◽  
Intrathoracic Pressure ◽  
Lung Mechanics ◽  
Dynamic Hyperinflation ◽  
Expiratory Flow Limitation ◽  
Lung Inflation

Patients with obstructive lung disease are exposed to expiratory loads (ELs) and dynamic hyperinflation as a consequence of expiratory flow limitation. To understand how these alterations in lung mechanics might affect cardiac function, we examined the influence of a 10-cmH2O EL, alone and in combination with voluntary hyperinflation (ELH), on pulmonary pressures [esophageal (Pes) and gastric (Pg)] and cardiac output (CO) in seven healthy subjects. CO was determined by using an acetylene method at rest and at 40 and 70% of peak work. At rest and during exercise, EL resulted in an increase in Pes and Pg (7-18 cmH2O; P < 0.05) and a decrease in CO (from 5.3 ± 1.8 to 4.5 ± 1.4, 12.2 ± 2.2 to 11.2 ± 2.2, and 16.3 ± 3.3 to 15.2 ± 3.2 l/min for rest, 40% peak work, and 70% peak work, respectively; P < 0.05), which remained depressed after an additional 2 min of EL. With ELH, CO increased at rest and both exercise loads (relative to EL only) but remained below control values. The changes in CO were due to a reduction in stroke volume with a tendency for stroke volume to fall further with prolonged EL. There was a negative correlation between CO and the increase in expiratory Pes and Pg with EL ( R = -0.58 and -0.60; P < 0.01), whereas the rise in CO with subsequent hyperinflation was related to a more negative Pes ( R = 0.72; P < 0.01). In conclusion, EL leads to a reduction in CO, which appears to be primarily related to increases in expiratory abdominal and intrathoracic pressure, whereas ELH resulted in an improved CO, suggesting that lung inflation has little impact on cardiac function.

scholarly journals The Effect of Sustained Positive Airway Pressure on Derived Cardiac Output in Children

1994 ◽  
Vol 22 (1) ◽  
pp. 30-34 ◽  
Author(s):  
J. B. Clough ◽  
A. W. Duncan ◽  
P. D. Sly
Keyword(s):  
Cardiac Output ◽  
Stroke Volume ◽  
Airway Pressure ◽  
Positive Airway Pressure ◽  
Intrathoracic Pressure ◽  
Continuous Variable ◽  
Positive Pressure ◽  
Age Related ◽  
Pulsed Wave Doppler ◽  
Doppler Techniques

It is well established that the improvement in gas exchange that occurs with positive pressure ventilation may come at the expense of a decrease in cardiac output and oxygen delivery. Clinical observation suggests that children and infants may be more resistant than adults to the falls in cardiac output induced by positive airway pressure. The aims of this study were to quantify the effect of a sustained increase in intrathoracic pressure on cardiac output and stroke volume, and to determine whether this change is age-related. Twenty-eight children undergoing general anaesthesia were studied. Cardiac output was derived using pulsed wave Doppler techniques at four different levels of sustained positive airway pressure, and stroke volume was calculated. The relationship between airway pressure and both cardiac output and stroke volume was examined using a general linear model which included age as a continuous variable. Cardiac output decreased with increasing levels of sustained positive airway pressure (P=0.001). The fall in SV for a given airway pressure increased with increasing age (P=0.02). The mechanisms responsible for the increase of the magnitude of the fall in stroke volume with age remain to be elucidated.

scholarly journals Echocardiographic measure of dynamic arterial elastance predict pressure response during norepinephrine weaning: an observational study

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Maxime Nguyen ◽  
Osama Abou-Arab ◽  
Stéphane Bar ◽  
Hervé Dupont ◽  
Bélaïd Bouhemad ◽  
...  
Keyword(s):  
Stroke Volume ◽  
Pulse Pressure ◽  
Pulse Pressure Variation ◽  
Stroke Volume Variation ◽  
Pressure Variation ◽  
Pressure Response ◽  
Arterial Elastance ◽  
Volume Variation ◽  
Norepinephrine Dose ◽  
Stroke Volume Variations

AbstractThe purpose of this study was to determine whether dynamic elastance EAdyn derived from echocardiographic measurements of stroke volume variations can predict the success of a one-step decrease of norepinephrine dose. In this prospective single-center study, 39 patients with vasoplegic syndrome treated with norepinephrine and for whom the attending physician had decided to decrease norepinephrine dose and monitored by thermodilution were analyzed. EAdyn is the ratio of pulse pressure variation to stroke volume variation and was calculated from echocardiography stroke volume variations and from transpulmonary thermodilution. Pulse pressure variation was obtained from invasive arterial monitoring. Responders were defined by a decrease in mean arterial pressure (MAP) > 10% following norepinephrine decrease. The median decrease in norepinephrine was of 0.04 [0.03–0.05] µg kg−1 min−1. Twelve patients (31%) were classified as pressure responders with a median decrease in MAP of 13% [12–15%]. EAdyn was lower in pressure responders (0.40 [0.24–0.57] vs 0.95 [0.77–1.09], p < 0.01). EAdyn was able to discriminate between pressure responders and non-responders with an area under the curve of 0.86 (CI95% [0.71 to1.0], p < 0.05). The optimal cut-off was 0.8. EAdyn calculated from the echocardiographic estimation of the stroke volume variation and the invasive arterial pulse pressure variation can be used to discriminate pressure response to norepinephrine weaning. Agreement between EAdyn calculated from echocardiography and thermodilution was poor. Echocardiographic EAdyn might be used at bedside to optimize hemodynamic treatment.

Basic Critical Care Echocardiography by Pulmonary Fellows

2014 ◽  
Vol 42 (10) ◽  
pp. 2169-2177 ◽  
Author(s):  
Kay Choong See ◽  
Venetia Ong ◽  
Jeffrey Ng ◽  
Rou An Tan ◽  
Jason Phua
Keyword(s):  
Critical Care ◽  
Critical Care Echocardiography

Breathing through an inspiratory threshold device improves stroke volume during central hypovolemia in humans

2008 ◽  
Vol 104 (5) ◽  
pp. 1402-1409 ◽  
Author(s):  
Kathy L. Ryan ◽  
William H. Cooke ◽  
Caroline A. Rickards ◽  
Keith G. Lurie ◽  
Victor A. Convertino
Keyword(s):  
Cardiac Output ◽  
Arterial Pressure ◽  
Stroke Volume ◽  
Lower Body Negative Pressure ◽  
Systolic Arterial Pressure ◽  
Intrathoracic Pressure ◽  
Subsequent Increase ◽  
Arterial Blood ◽  
Threshold Device ◽  
Inspiratory Resistance

Inspiratory resistance induced by breathing through an impedance threshold device (ITD) reduces intrathoracic pressure and increases stroke volume (SV) in supine normovolemic humans. We hypothesized that breathing through an ITD would also be associated with a protection of SV and a subsequent increase in the tolerance to progressive central hypovolemia. Eight volunteers (5 men, 3 women) were instrumented to record ECG and beat-by-beat arterial pressure and SV (Finometer). Tolerance to progressive lower body negative pressure (LBNP) was assessed while subjects breathed against either 0 (sham ITD) or −7 cmH2O inspiratory resistance (active ITD); experiments were performed on separate days. Because the active ITD increased LBNP tolerance time from 2,014 ± 106 to 2,259 ± 138 s ( P = 0.006), data were analyzed (time and frequency domains) under both conditions at the time at which cardiovascular collapse occurred during the sham experiment to determine the mechanisms underlying this protective effect. At this time point, arterial blood pressure, SV, and cardiac output were higher ( P ≤ 0.005) when breathing on the active ITD rather than the sham ITD, whereas indirect indicators of autonomic activity (low- and high-frequency oscillations of the R-to-R interval) were not altered. ITD breathing did not alter the transfer function between systolic arterial pressure and R-to-R interval, indicating that integrated baroreflex sensitivity was similar between the two conditions. These data show that breathing against inspiratory resistance increases tolerance to progressive central hypovolemia by better maintaining SV, cardiac output, and arterial blood pressures via primarily mechanical rather than neural mechanisms.

scholarly journals Non-Invasive Scale Measurement of Cardiac Output Compared with the Gold-Standard Direct Fick Method: A Feasibility Study

2021 ◽  
Author(s):  
Daniel Yazdi ◽  
Sarin Patel ◽  
Suriya Sridaran ◽  
Evan Wilson ◽  
Sarah Smith ◽  
...  
Keyword(s):  
Cardiac Output ◽  
Stroke Volume ◽  
Cardiac Function ◽  
Exercise Test ◽  
Gold Standard ◽  
Cardiopulmonary Exercise Test ◽  
Cardiac Monitoring ◽  
Non Invasive ◽  
Cardiopulmonary Exercise ◽  
The Mean

AbstractBackgroundObjective markers of cardiac function are limited in the outpatient setting and may be beneficial for monitoring patients with chronic cardiac conditions.ObjectiveWe assess the accuracy of a scale, with the ability to capture ballistocardiography, electrocardiography, and impedance plethysmography signals from a patient’s feet while standing on the scale, in measuring stroke volume and cardiac output compared to the gold-standard direct Fick method.MethodsThirty-two patients with unexplained dyspnea undergoing level 3 invasive cardiopulmonary exercise test at a tertiary medical center were included in the final analysis. We obtained scale and direct Fick measurements of stroke volume and cardiac output before and immediately after invasive cardiopulmonary exercise test.ResultsStroke volume and cardiac output from a cardiac scale and the direct Fick method correlated with r = 0.81 and r = 0.85, respectively (P < 0.001 each). The mean absolute error of the scale estimated stroke volume was -1.58 mL, with a 95% limits of agreement (LOA) of -21.97 mL to 18.81 mL. The mean error for the scale estimated cardiac output was -0.31 L/min, with a 95% LOA of -2.62 L/min to 2.00 L/min. The change in stroke volume and cardiac output before and after exercise were 78.9% and 96.7% concordant, respectively between the two measuring methods.ConclusionsThis novel scale with cardiac monitoring abilities may allow for non-invasive, longitudinal measures of cardiac function. Using the widely accepted form factor of a bathroom scale, this method of monitoring can be easily integrated into a patient’s lifestyle.

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