scholarly journals Cardiopulmonary physiology: why the heart and lungs are inextricably linked

2017 ◽  
Vol 41 (3) ◽  
pp. 348-353 ◽  
Author(s):  
Kevin Verhoeff ◽  
Jamie R. Mitchell
Keyword(s):  
Mechanical Ventilation ◽  
Blood Volume ◽  
Intrathoracic Pressure ◽  
Left Ventricular ◽  
Health Science ◽  
Diastolic Filling ◽  
Volume Distribution ◽  
External Constraint ◽  
Heart Blood ◽  
Science Educators

Because the heart and lungs are confined within the thoracic cavity, understanding their interactions is integral for studying each system. Such interactions include changes in external constraint to the heart, blood volume redistribution (venous return), direct ventricular interaction (DVI), and left ventricular (LV) afterload. During mechanical ventilation, these interactions can be amplified and result in reduced cardiac output. For example, increased intrathoracic pressure associated with mechanical ventilation can increase external constraint and limit ventricular diastolic filling and, therefore, output. Similarly, high intrathoracic pressures can alter blood volume distribution and limit diastolic filling of both ventricles while concomitantly increasing pulmonary vascular resistance, leading to increased DVI, which may further limit LV filling. While LV afterload is generally considered to decrease with increased intrathoracic pressure, the question arises if the reduced LV afterload is primarily a consequence of a reduced LV preload. A thorough understanding of the interaction between the heart and lungs can be complicated but is essential for clinicians and health science students alike. In this teaching review, we have attempted to highlight the present understanding of certain salient aspects of cardiopulmonary physiology and pathophysiology, as well as provide a resource for multidisciplined health science educators and students.

External pressure of undisturbed left ventricle

1990 ◽  
Vol 258 (4) ◽  
pp. H1079-H1086 ◽  
Author(s):  
R. J. Applegate ◽  
W. P. Santamore ◽  
H. S. Klopfenstein ◽  
W. C. Little
Keyword(s):  
Left Ventricle ◽  
Diastolic Pressure ◽  
Intrathoracic Pressure ◽  
External Pressure ◽  
Left Ventricular ◽  
Chamber Pressure ◽  
Diastolic Filling ◽  
End Diastolic Volume ◽  
Before And After ◽  
The Difference

We evaluated the contribution of the thorax and the undisturbed pericardium to the external pressure of the euvolemic left ventricle in thirteen anesthetized dogs. Left ventricular (LV) end-diastolic pressure (EDP) in the euvolemic state was 7 +/- 2 mmHg initially and increased to 10 +/- 2 mmHg after the chest and pericardium were opened. LV end-diastolic volume (conductance catheter) was 43 +/- 20 ml initially and did not change after the chest or the pericardium was opened. Intrathoracic (PIT) and pericardial (PPER) pressures were calculated as the difference in LV chamber pressure before and after opening these spaces. Thus for the LV, PIT was -3 +/- 1 mmHg, and PPER was 0 +/- 2 mmHg. Isovolumic relaxation, early diastolic filling, and total diastolic filling were not significantly altered after the chest or pericardium was opened. Thus under euvolemic conditions in this model pericardial pressure is negligible, and the external pressure of the undisturbed left ventricle is negative and equal to intrathoracic pressure.

Study of Systolic Pressure Variation (SPV) in Presence of Mechanical Ventilation

2002 ◽  
Vol 25 (4) ◽  
pp. 313-320 ◽  
Author(s):  
F. Clemente ◽  
C. De Lazzari ◽  
M. Darowski ◽  
G. Ferrari ◽  
R. Mimmo ◽  
...  
Keyword(s):  
Mechanical Ventilation ◽  
Cardiovascular System ◽  
Arterial Compliance ◽  
Systolic Pressure ◽  
Intrathoracic Pressure ◽  
Left Ventricular ◽  
Filling Pressure ◽  
Pressure Variation ◽  
Lumped Parameter Model ◽  
Systolic Pressure Variation

Systolic pressure variation (SPV) and its components (dUp and dDown) have been demonstrated to be of interest in assessing preload in mechanically ventilated patients. The aim of this paper is to analyse the sensitivity of these variables to preload and volemic changes during mechanical ventilation in different conditions of the cardiovascular system. Computer simulation experiments have been done using a modular lumped parameter model of the cardiovascular system. The effect of mechanical ventilation has been reproduced operating on intrathoracic pressure. Experiments have been performed varying preload through filling pressure. Sensitivity of SVP, dUp and dDown is described varying separately left ventricular elastance (Ev), systemic arterial resistance (Ras) and systemic arterial compliance (Cas). The sensitivity of SPV and dDown to preload and filling pressure is appreciable for high values of Ev and for a wide variation of Ras. Preliminary clinical data concerning the three parameters show good correlation with simulation results.

scholarly journals Clinical Applications of Mechanical Ventilation

1986 ◽  
Vol 14 (3) ◽  
pp. 267-280 ◽  
Author(s):  
R. Henning
Keyword(s):  
Mechanical Ventilation ◽  
Respiratory Failure ◽  
Acute Asthma ◽  
Flail Chest ◽  
Intrathoracic Pressure ◽  
Left Ventricular ◽  
Clinical Applications ◽  
Left Ventricular Performance ◽  
Ventricular Performance ◽  
Postoperative Ventilation

This paper reviews recent applications of mechanical ventilation such as controlled hypoventilation in acute asthma, domiciliary nocturnal ventilation in chronic respiratory failure due to neuromuscular disease and improvement of left ventricular performance by raised intrathoracic pressure. Established uses of mechanical ventilation include control of respiratory failure, intracranial pressure and pulmonary hypertension while other uses such as internal splinting of flail chest, simultaneous ventilation-compression cardiopulmonary resuscitation and prophylactic postoperative ventilation are more controversial.

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.

scholarly journals Exercise heat acclimation has minimal effects on left ventricular volumes, function and systemic hemodynamics in euhydrated and dehydrated trained humans

2020 ◽  
Vol 319 (5) ◽  
pp. H965-H979
Author(s):  
Gavin Travers ◽  
José González-Alonso ◽  
Nathan Riding ◽  
David Nichols ◽  
Anthony Shaw ◽  
...  
Keyword(s):  
Heart Rate ◽  
Cardiac Output ◽  
Left Ventricle ◽  
Blood Volume ◽  
Heat Acclimation ◽  
Left Ventricular ◽  
Systemic Hemodynamics ◽  
Diastolic Filling ◽  
Left Ventricular Volumes ◽  
Ventricular Volumes

This study demonstrates that 10 days of exercise heat acclimation has minimal effects on left ventricular volumes, intrinsic cardiac function, and systemic hemodynamics during prolonged, repeated semirecumbent exercise in moderate heat, where heart rate and blood volume are similar to preacclimation levels. However, progressive dehydration is consistently associated with similar degrees of hyperthermia and tachycardia and reductions in blood volume, diastolic filling of the left ventricle, stroke volume, and cardiac output, regardless of acclimation state.

Sign in / Sign up

Export Citation Format

Share Document