Effect of continuous pressure breathing on right ventricular volumes

1967 ◽  
Vol 22 (6) ◽  
pp. 1053-1060 ◽  
Author(s):  
Maylene Wong ◽  
Edgardo E. Escobar ◽  
Gilberto Martinez ◽  
John Butler ◽  
Elliot Rapaport
Keyword(s):  
Right Ventricular ◽  
Negative Pressure ◽  
Atmospheric Pressure ◽  
Diastolic Pressure ◽  
Venous Pressure ◽  
Intrathoracic Pressure ◽  
Transmural Pressure ◽  
Positive Pressure ◽  
End Diastolic Volume ◽  
Negative Pressure Breathing

We measured the end-diastolic volume (EDV) and stroke volume (SV) in the right ventricle of anesthetized dogs during continuous pressure breathing and compared them to measurements taken during breathing at atmospheric pressure. During intratracheal positive-pressure breathing, EDV, and SV decreased and end-diastolic pressure became more positive relative to atmospheric pressure. During intratracheal negative-pressure breathing, EDV enlarged and SV tended to increase; end-diastolic pressure became more negative. During extrathoracic negative-pressure breathing SV decreased, EDV fell, though not significantly, and end-diastolic pressure rose, but insignificantly. Changes in EDV observed during intratracheal positive-pressure breathing and intratracheal negative-pressure breathing were associated with minor shifts in transmural pressure (end-diastolic pressure minus intrapleural pressure) in the expected directions, but during extrathoracic negative-pressure breathing a large increase in transmural pressure took place with the nonsignificant reduction in EDV. We believe that intrathoracic pressure influences right ventricular filling by changing the peripheral-to-central venous pressure gradient. The cause of the alteration in diastolic ventricular distensibility demonstrated during extra-thoracic negative-pressure breathing remains unexplained. positive-pressure breathing; negative-pressure breathing; extrathoracic negative-pressure breathing Submitted on August 16, 1966

Responses to continuous negative-pressure breathing in man at rest and during exercise

1980 ◽  
Vol 48 (6) ◽  
pp. 977-981 ◽  
Author(s):  
H. Bjurstedt ◽  
G. Rosenhamer ◽  
C. M. Hesser ◽  
B. Lindborg
Keyword(s):  
Negative Pressure ◽  
Venous Pressure ◽  
Intrathoracic Pressure ◽  
Carbon Dioxide Tension ◽  
Minute Volume ◽  
Left Ventricular ◽  
Circulatory Effects ◽  
Ventricular Afterload ◽  
Negative Pressure Breathing ◽  
The Right

We studied the respiratory and circulatory effects in six healthy supine volunteers of continuous negative-pressure breathing (CNPB) at -15 and -30 cmH2O at rest and during dynamic leg exercies at 50% of individual working capacity. CNPB had no significant effects on respiratory minute volume, tidal volume, or arterial carbon dioxide tension. Mean arterial pressure remained essentially unchanged both at rest and during exercise, signifying that the reductions in intrathoracic pressure caused corresponding increases in left ventricular afterload. Nevertheless, cardiac output increased significantly in both conditions, causing reductions of mean central venous pressure that were considerably greater during exercise than at rest. These responses were reflected by increments in left ventricular work, amounting to 24 and 20% at rest and during exercise, respectively, at -30 cmH2O. We conclude that in CNPB at rest the increased activity of the left ventricle with associated juxtathoracic venous collapse protects the right heart and pulmonary circulation from congestion and that it does so even more effectively during exercise.

Venous and arterial reflex responses to positive-pressure breathing and lower body negative pressure

1997 ◽  
Vol 82 (6) ◽  
pp. 1889-1896 ◽  
Author(s):  
Jochen K. Peters ◽  
George Lister ◽  
Ethan R. Nadel ◽  
Gary W. Mack
Keyword(s):  
Cardiac Output ◽  
Vascular Resistance ◽  
Negative Pressure ◽  
Lower Body Negative Pressure ◽  
Venous Pressure ◽  
Transmural Pressure ◽  
Right Atrial ◽  
Positive Pressure ◽  
Lower Body ◽  
Reflex Responses

Peters, Jochen K., George Lister, Ethan R. Nadel, and Gary W. Mack. Venous and arterial reflex responses to positive-pressure breathing and lower body negative pressure. J. Appl. Physiol. 82(6): 1889–1896, 1997.—We examined the relative importance of arteriolar and venous reflex responses during reductions in cardiac output provoked by conditions that increase [positive end-expiratory pressure (PEEP)] or decrease [lower body negative pressure (LBNP)] peripheral venous filling. Five healthy subjects were exposed to PEEP (10, 15, 20, and 25 cmH2O) and LBNP (−10, −15, −20, and −25 mmHg) to induce progressive but comparable reductions in right atrial transmural pressure (control to minimum): from 5.9 ± 0.4 to 1.8 ± 0.7 and from 6.5 ± 0.6 to 2.0 ± 0.2 mmHg with PEEP and LBNP, respectively. Cardiac output (impedance cardiography) fell less during PEEP than during LBNP (from 3.64 ± 0.21 to 2.81 ± 0.21 and from 3.39 ± 0.21 to 2.14 ± 0.24 l ⋅ min−1 ⋅ m−2with PEEP and LBNP, respectively), and mean arterial pressure increased. We observed sustained increases in forearm vascular resistance (i.e., forearm blood flow by venous occlusion plethysmography) and systemic vascular resistance that were greater during LBNP: from 19.7 ± 2.91 to 27.97 ± 5.46 and from 20.56 ± 2.48 to 50.25 ± 5.86 mmHg ⋅ ml−1 ⋅ 100 ml tissue−1 ⋅ min ( P < 0.05) during PEEP and LBNP, respectively. Venomotor responses (venous pressure in the hemodynamically isolated limb) were always transient, significant only with the greatest reduction in right atrial transmural pressure, and were similar for LBNP and PEEP. Thus arteriolar rather than venous responses are predominant in blood volume mobilization from skin and muscle, and venoconstriction is not intensified with venous engorgement during PEEP.

Cardiovascular responses of man during negative-pressure breathing

1960 ◽  
Vol 15 (4) ◽  
pp. 557-560 ◽  
Author(s):  
E. Y. Ting ◽  
S. K. Hong ◽  
H. Rahn
Keyword(s):  
Heart Rate ◽  
Negative Pressure ◽  
Venous Pressure ◽  
Cardiovascular Responses ◽  
Positive Pressure ◽  
Reduced Pressure ◽  
Cavity Collapse ◽  
Blood Pressures ◽  
Negative Pressure Breathing ◽  
Finger Plethysmography

Blood pressures, heart rate and finger volumes were recorded while supine subjects submitted to various degrees of continuous negative-pressure breathing. The lowest pressure was –30 cm H2O. Systolic and diastolic arterial pressures as well as heart rate remained essentially unchanged. The peripheral venous pressure estimated by an indirect method was slightly lowered. Finger plethysmography indicated a peripheral vasoconstriction to the same degree as observed during positive-pressure breathing. Various considerations suggest that during negative-pressure breathing the veins entering the thoracic cavity collapse and effectively divide the circulation into the thoracic one which operates at a considerably reduced pressure, and the nonthoracic circulation which is maintained at normal pressures. The pressure difference between these two circulations is maintained by the left ventricle. Submitted on February 8, 1960

Effect of intrathoracic pressure on pressure-volume characteristics of the lung in man

1975 ◽  
Vol 38 (3) ◽  
pp. 411-417 ◽  
Author(s):  
H. S. Goldberg ◽  
W. Mitzner ◽  
K. Adams ◽  
H. Menkes ◽  
S. Lichtenstein ◽  
...  
Keyword(s):  
Negative Pressure ◽  
Total Lung Capacity ◽  
Human Subjects ◽  
Ambient Pressure ◽  
Intrathoracic Pressure ◽  
Dynamic Compliance ◽  
Positive Pressure ◽  
Lung Capacity ◽  
Airway Opening ◽  
Volume Characteristics

Quasi-static pressure-volume (P-V) curves in normal seated human subjects were determined with pressure at the airway opening (Pa0) set below (negative pressure), above (positive pressure), or equal to ambient pressure. Dynamic compliance (Cdyn) during controlled continuous negative pressure breathing (CNPB) was also studied. Quasi-static P-V curves at negative pressure were decreased in slope, reflected a decrease in total lung capacity, and intersected the P-V curve obtained at ambient Pa0. At positive pressure the P-V curves showed an increase in slope and an increase in total lung capacity. During CNPB a fall in Cdyn was found. The fall in Cdyn was rapid and persisted for the duration of CNPB. Cdyn promptly returned to control levels when Pa0 was adjusted to ambient pressure.

Cardiopulmonary effects of continuous pressure breathing in hypothermic dogs

1965 ◽  
Vol 20 (4) ◽  
pp. 669-674 ◽  
Author(s):  
J. Salzano ◽  
F. G. Hall
Keyword(s):  
Heart Rate ◽  
Cardiac Output ◽  
Oxygen Consumption ◽  
Stroke Volume ◽  
Negative Pressure ◽  
Alveolar Ventilation ◽  
Positive Pressure ◽  
Negative Pressure Breathing ◽  
Continuous Positive Pressure ◽  
Respiratory Dead Space

Continuous pressure breathing was studied in hypothermic anesthetized dogs. Alveolar ventilation decreased during continuous positive-pressure breathing and increased during continuous negative-pressure breathing. The changes in alveolar ventilation were due to changes in respiratory rate as well as in respiratory dead space. Cardiac output fell significantly during continuous positive-pressure breathing due to a reduction in heart rate and stroke volume. During continuous negative-pressure breathing cardiac output was only slightly greater than during control as a result of a fall in heart rate and an increase in stroke volume. Oxygen consumption was reduced to 60% of control during continuous positive-pressure breathing of 16 cm H2O but was 25% greater than control during continuous negative-pressure breathing. Qualitatively, CO2 production changed as did O2 consumption but was different quantitatively during continuous negative-pressure breathing indicating hyperventilation due to increased respiratory rate. Mean pulmonary artery pressures and pulmonary resistance varied directly with the applied intratracheal pressure. The results indicate that the hypothermic animal can tolerate an imposed stress such as continuous pressure breathing and can increase its oxygen consumption during continuous negative-pressure breathing as does the normothermic animal. hypothermia; respiratory dead space; metabolic rate; cardiac output Submitted on December 8, 1964

Effect of increases in lung volume on clearance of aerosolized solute from human lungs

1985 ◽  
Vol 59 (4) ◽  
pp. 1242-1248 ◽  
Author(s):  
J. D. Marks ◽  
J. M. Luce ◽  
N. M. Lazar ◽  
J. N. Wu ◽  
A. Lipavsky ◽  
...  
Keyword(s):  
Lung Volume ◽  
Negative Pressure ◽  
Ambient Pressure ◽  
Pressure Control ◽  
Positive Pressure ◽  
Healthy Humans ◽  
Human Lungs ◽  
Solute Uptake ◽  
Residual Capacity ◽  
Negative Pressure Breathing

To study the effect of increases in lung volume on solute uptake, we measured clearance of 99mTc-diethylenetriaminepentaacetic acid (Tc-DTPA) at different lung volumes in 19 healthy humans. Seven subjects inhaled aerosol (1 micron activity median aerodynamic diam) at ambient pressure; clearance and functional residual capacity (FRC) were measured at ambient pressure (control) and at increased lung volume produced by positive pressure [12 cmH2O continuous positive airway pressure (CPAP)] or negative pressure (voluntary breathing). Six different subjects inhaled aerosol at ambient pressure; clearance and FRC were measured at ambient pressure and CPAP of 6, 12, and 18 cmH2O pressure. Six additional subjects inhaled aerosol at ambient pressure or at CPAP of 12 cmH2O; clearance and FRC were determined at CPAP of 12 cmH2O. According to the results, Tc-DTPA clearance from human lungs is accelerated exponentially by increases in lung volume, this effect occurs whether lung volume is increased by positive or negative pressure breathing, and the effect is the same whether lung volume is increased during or after aerosol administration. The effect of lung volume must be recognized when interpreting the results of this method.

Modulation of bat wing venule contraction by transmural pressure changes

1992 ◽  
Vol 262 (3) ◽  
pp. H625-H634 ◽  
Author(s):  
M. J. Davis ◽  
X. Shi ◽  
P. J. Sikes
Keyword(s):  
Venous Pressure ◽  
Transmural Pressure ◽  
The Body ◽  
Intraluminal Pressure ◽  
Positive Pressure ◽  
Cross Sectional ◽  
Series Of Experiments ◽  
Pressure Changes ◽  
Bat Wing

We tested the hypothesis that the frequency and amplitude of spontaneous venular contractions in the bat wing could be modulated by changes in transmural pressure. In one series of experiments, venous pressure in the wing was elevated by pressurizing a box containing the body of the animal while the wing was exposed to atmospheric pressure. During this time, venular diameters were continuously recorded using intravital microscopic techniques while venular pressures were measured through servo-null micropipettes. In another series of experiments, single venular segments were dissected from the wing, cannulated, and pressurized in vitro. The results from both experimental protocols were qualitatively similar; alterations in venous pressure over a narrow range (+/- 5 cmH2O from control) produced substantial changes in contraction frequency and amplitude. The product of frequency and cross-sectional area was maximal over the venous pressure range between 10 and 15 cmH2O. Venules demonstrated a rate-sensitive component in their reaction to rapid pressure changes, because contraction bursts occurred immediately after positive pressure steps and quiescent periods often occurred after negative pressure steps. We conclude that venular vasomotion in the bat wing is modulated by intraluminal pressure and involves a bidirectional, rate-sensitive mechanism. In addition, comparisons with arteriolar vasomotion studies suggest that venules are more sensitive to luminal pressure changes than arterioles.

Abdominal muscle and diaphragm activities and cavity pressures in pressure breathing

1963 ◽  
Vol 18 (1) ◽  
pp. 37-42 ◽  
Author(s):  
Beverly Bishop
Keyword(s):  
Technical Assistance ◽  
Respiratory Activity ◽  
Silent Period ◽  
Intrathoracic Pressure ◽  
Abdominal Muscle ◽  
Positive Pressure ◽  
Abdominal Pressure ◽  
Negative Pressure Breathing ◽  
External Oblique ◽  
Anesthetized Cat

The respiratory contribution of the diaphragm and external oblique abdominal muscle has been assessed by recording from the anesthetized cat the integrated electromyograms during continuous pressure breathing. As the intrapulmonary pressure is progressively reduced from 0 to -12 cm H2O, the diaphragm becomes increasingly active until it has no silent period during the respiratory cycle. Concomitantly, any respiratory activity in the abdominal muscle is completely silenced. A hyperactive diaphragm and relaxed abdominal wall can account for the constancy seen in the directly recorded intra-abdominal pressure even though the intrathoracic pressure falls. When the animal is subjected to pressures from 0 to +14 cm H2O, the diaphragm is initially inhibited and the abdominal muscle becomes increasingly active. In every animal, on positive pressure the abdominal muscle becomes active during expiration and in 20% of the animals it is also active during inspiration. Active expiration continues throughout the pressure breathing and is sufficient to reverse the breath by breath abdominal pressure variations. During negative pressure breathing, respiration is an inspiratory act and only the thorax is subjected to stress. During positive pressure breathing, respiration is an expiratory act and both the thorax and abdomen are subjected to the stress. Submitted on May 21, 1962 Note: (With the Technical Assistance of J. R. Blumstein and D. Pennec) Submitted on January 22, 1962

Immersion diuresis in dogs

1977 ◽  
Vol 42 (6) ◽  
pp. 915-922 ◽  
Author(s):  
J. T. Davis ◽  
A. B. DuBois
Keyword(s):  
Negative Pressure ◽  
Early Phase ◽  
Left Atrial ◽  
Stretch Reflex ◽  
Transmural Pressure ◽  
Cervical Vagotomy ◽  
Anesthetized Dogs ◽  
Immersion Diuresis ◽  
Negative Pressure Breathing ◽  
Average Left Atrial

The mechanism of diuresis during the 1st h of immersion was investigated using anesthetized dogs. Four different experiments were carried out. First, left atrial transmural pressure was measured before, during, and after immersion. The data suggest that, although the left atrium may or may not be stretched depending on the conditions of immersion, the amount of diuresis is independent of the amount of left atrial stretch, and therefore a causal relationship between diuresis and left atrial stretch could not be established. Second, bilateral cervical vagotomy was carried out. Immersion diuresis sometimes occurred despite this vagotomy, suggesting that the left atrial stretch reflex was not participating in those cases. Third, negative-pressure breathing was carried out to simulate the negative transthoracic pressure associated with uncompensated immersion. The average left atrial transmural pressure did not change. A slight hemodilution and a moderate diuresis occurred. There was no correlation between changes in left atrial transmural pressure and changes in urine ouput. Fourth, blood studies were done on splenectomized dogs subjected to immersion. Hemodilution occurred and was most marked in dogs which had had their kidneys removed. The hemodilution is sufficient to explain the early phase of the immersion diuresis. The data suggest that, in anesthetized dogs, hemodilution is the probable initiator of diuresis upon immersion and that, in dogs, left atrial stretch is unrelated to diuresis during immersion or negative-pressure breathing.

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