Negative intrathoracic pressure decreases independently left ventricular filling and emptying

J. Peters, C. Fraser, R. S. Stuart, William A Baumgartner, J. L. Robotham

Research output: Contribution to journalArticle

Abstract

The mechanism for the fall in left ventricular (LV) stroke volume with normal and obstructed inspiration is controversial with changes proposed in LV preload and afterload. During respiration extending over several cardiac cycles, changes in both LV filling and emptying could occur, rendering demonstration of any responsible mechanism difficult. To evaluate the independent effects of negative intrathoracic pressure (NITP) on LV filling and emptying, we have analyzed the effects of NITP confined to either diastole or systole using electrocardiogram (ECG)-triggered phrenic nerve stimulation in six anesthetized closed-chest dogs. Lung volume was either maintained by completely obstructing the airway or allowed to increase during NITP. With diastolic NITP and the airway obstructed during phrenic nerve stimulation, LV filling volume (integrated mitral flow) significantly decreased (-37 ± 6.1% SE) associated with increases in LV and right atrial filling pressures at end diastole relative to both atmospheric and esophageal pressures. Right atrial pressure relative to either atmospheric or esophageal pressure increased significantly more than left atrial pressure. The ensuing LV stroke volume (integrated ascending aortic flow) decreased significantly (-30.8 ± 5.9%). With NITP confined to systole and at constant LV preload, LV stroke volume also decreased (-12.9 ± 2.5%) associated with an increase in LV systolic pressure relative to esophageal pressure. Similar significant changes were observed despite a smaller fall in esophageal pressure when lung volume was allowed to increase during either diastolic or systolic NITP. We conclude that 1) NITP confined to diastole decreases LV filling and the ensuing LV stroke volume, most likely by ventricular interdependence; 2) NITP confined to systole also decreases LV stroke volume presumptively by imposing an increased afterload on the LV; 3) both diastolic and systolic mechanisms should contribute to a decreased LV stroke volume during normal and obstructed inspiration; and 4) if the effects of intrathoracic pressure changes were to extend over several cardiac cycles, mechanisms exist to account for either increases or decreases in LV volumes.

Original languageEnglish (US)
JournalAmerican Journal of Physiology - Heart and Circulatory Physiology
Volume257
Issue number1
StatePublished - 1989

Fingerprint

Pressure
Stroke Volume
Atrial Pressure
Diastole
Systole
Phrenic Nerve
Lung
Atmospheric Pressure
Ventricular Pressure
Electrocardiography
Respiration
Thorax
Dogs
Blood Pressure

ASJC Scopus subject areas

  • Physiology

Cite this

Negative intrathoracic pressure decreases independently left ventricular filling and emptying. / Peters, J.; Fraser, C.; Stuart, R. S.; Baumgartner, William A; Robotham, J. L.

In: American Journal of Physiology - Heart and Circulatory Physiology, Vol. 257, No. 1, 1989.

Research output: Contribution to journalArticle

@article{b0b25b385fcd4f14996e132496b593c2,
title = "Negative intrathoracic pressure decreases independently left ventricular filling and emptying",
abstract = "The mechanism for the fall in left ventricular (LV) stroke volume with normal and obstructed inspiration is controversial with changes proposed in LV preload and afterload. During respiration extending over several cardiac cycles, changes in both LV filling and emptying could occur, rendering demonstration of any responsible mechanism difficult. To evaluate the independent effects of negative intrathoracic pressure (NITP) on LV filling and emptying, we have analyzed the effects of NITP confined to either diastole or systole using electrocardiogram (ECG)-triggered phrenic nerve stimulation in six anesthetized closed-chest dogs. Lung volume was either maintained by completely obstructing the airway or allowed to increase during NITP. With diastolic NITP and the airway obstructed during phrenic nerve stimulation, LV filling volume (integrated mitral flow) significantly decreased (-37 ± 6.1{\%} SE) associated with increases in LV and right atrial filling pressures at end diastole relative to both atmospheric and esophageal pressures. Right atrial pressure relative to either atmospheric or esophageal pressure increased significantly more than left atrial pressure. The ensuing LV stroke volume (integrated ascending aortic flow) decreased significantly (-30.8 ± 5.9{\%}). With NITP confined to systole and at constant LV preload, LV stroke volume also decreased (-12.9 ± 2.5{\%}) associated with an increase in LV systolic pressure relative to esophageal pressure. Similar significant changes were observed despite a smaller fall in esophageal pressure when lung volume was allowed to increase during either diastolic or systolic NITP. We conclude that 1) NITP confined to diastole decreases LV filling and the ensuing LV stroke volume, most likely by ventricular interdependence; 2) NITP confined to systole also decreases LV stroke volume presumptively by imposing an increased afterload on the LV; 3) both diastolic and systolic mechanisms should contribute to a decreased LV stroke volume during normal and obstructed inspiration; and 4) if the effects of intrathoracic pressure changes were to extend over several cardiac cycles, mechanisms exist to account for either increases or decreases in LV volumes.",
author = "J. Peters and C. Fraser and Stuart, {R. S.} and Baumgartner, {William A} and Robotham, {J. L.}",
year = "1989",
language = "English (US)",
volume = "257",
journal = "American Journal of Physiology",
issn = "0363-6135",
publisher = "American Physiological Society",
number = "1",

}

TY - JOUR

T1 - Negative intrathoracic pressure decreases independently left ventricular filling and emptying

AU - Peters, J.

AU - Fraser, C.

AU - Stuart, R. S.

AU - Baumgartner, William A

AU - Robotham, J. L.

PY - 1989

Y1 - 1989

N2 - The mechanism for the fall in left ventricular (LV) stroke volume with normal and obstructed inspiration is controversial with changes proposed in LV preload and afterload. During respiration extending over several cardiac cycles, changes in both LV filling and emptying could occur, rendering demonstration of any responsible mechanism difficult. To evaluate the independent effects of negative intrathoracic pressure (NITP) on LV filling and emptying, we have analyzed the effects of NITP confined to either diastole or systole using electrocardiogram (ECG)-triggered phrenic nerve stimulation in six anesthetized closed-chest dogs. Lung volume was either maintained by completely obstructing the airway or allowed to increase during NITP. With diastolic NITP and the airway obstructed during phrenic nerve stimulation, LV filling volume (integrated mitral flow) significantly decreased (-37 ± 6.1% SE) associated with increases in LV and right atrial filling pressures at end diastole relative to both atmospheric and esophageal pressures. Right atrial pressure relative to either atmospheric or esophageal pressure increased significantly more than left atrial pressure. The ensuing LV stroke volume (integrated ascending aortic flow) decreased significantly (-30.8 ± 5.9%). With NITP confined to systole and at constant LV preload, LV stroke volume also decreased (-12.9 ± 2.5%) associated with an increase in LV systolic pressure relative to esophageal pressure. Similar significant changes were observed despite a smaller fall in esophageal pressure when lung volume was allowed to increase during either diastolic or systolic NITP. We conclude that 1) NITP confined to diastole decreases LV filling and the ensuing LV stroke volume, most likely by ventricular interdependence; 2) NITP confined to systole also decreases LV stroke volume presumptively by imposing an increased afterload on the LV; 3) both diastolic and systolic mechanisms should contribute to a decreased LV stroke volume during normal and obstructed inspiration; and 4) if the effects of intrathoracic pressure changes were to extend over several cardiac cycles, mechanisms exist to account for either increases or decreases in LV volumes.

AB - The mechanism for the fall in left ventricular (LV) stroke volume with normal and obstructed inspiration is controversial with changes proposed in LV preload and afterload. During respiration extending over several cardiac cycles, changes in both LV filling and emptying could occur, rendering demonstration of any responsible mechanism difficult. To evaluate the independent effects of negative intrathoracic pressure (NITP) on LV filling and emptying, we have analyzed the effects of NITP confined to either diastole or systole using electrocardiogram (ECG)-triggered phrenic nerve stimulation in six anesthetized closed-chest dogs. Lung volume was either maintained by completely obstructing the airway or allowed to increase during NITP. With diastolic NITP and the airway obstructed during phrenic nerve stimulation, LV filling volume (integrated mitral flow) significantly decreased (-37 ± 6.1% SE) associated with increases in LV and right atrial filling pressures at end diastole relative to both atmospheric and esophageal pressures. Right atrial pressure relative to either atmospheric or esophageal pressure increased significantly more than left atrial pressure. The ensuing LV stroke volume (integrated ascending aortic flow) decreased significantly (-30.8 ± 5.9%). With NITP confined to systole and at constant LV preload, LV stroke volume also decreased (-12.9 ± 2.5%) associated with an increase in LV systolic pressure relative to esophageal pressure. Similar significant changes were observed despite a smaller fall in esophageal pressure when lung volume was allowed to increase during either diastolic or systolic NITP. We conclude that 1) NITP confined to diastole decreases LV filling and the ensuing LV stroke volume, most likely by ventricular interdependence; 2) NITP confined to systole also decreases LV stroke volume presumptively by imposing an increased afterload on the LV; 3) both diastolic and systolic mechanisms should contribute to a decreased LV stroke volume during normal and obstructed inspiration; and 4) if the effects of intrathoracic pressure changes were to extend over several cardiac cycles, mechanisms exist to account for either increases or decreases in LV volumes.

UR - http://www.scopus.com/inward/record.url?scp=0024339471&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0024339471&partnerID=8YFLogxK

M3 - Article

C2 - 2750932

AN - SCOPUS:0024339471

VL - 257

JO - American Journal of Physiology

JF - American Journal of Physiology

SN - 0363-6135

IS - 1

ER -