Respiratory pump maintains cardiac stroke volume during hypovolemia in young, healthy volunteers

Spontaneous breathing has beneficial effects on the circulation, since negative intrathoracic pressure enhances venous return and increases cardiac stroke volume. We quantified the contribution of the respiratory pump to preserve stroke volume during hypovolemia in awake, young, healthy subjects. Noninvasive stroke volume, cardiac output, heart rate, and mean arterial pressure (Finometer) were recorded in 31 volunteers (19 women), 19–30 yr old, during normovolemia and hypovolemia (approximating 450- to 500-ml reduction in central blood volume) induced by lower-body negative pressure. Control-mode noninvasive positive-pressure ventilation was employed to reduce the effect of the respiratory pump. The ventilator settings were matched to each subject’s spontaneous respiratory pattern. Stroke volume estimates during positive-pressure ventilation and spontaneous breathing were compared with Wilcoxon matched-pairs signed-rank test. Values are overall medians. During normovolemia, positive-pressure ventilation did not affect stroke volume or cardiac output. Hypovolemia resulted in an 18% decrease in stroke volume and a 9% decrease in cardiac output ( P < 0.001). Employing positive-pressure ventilation during hypovolemia decreased stroke volume further by 8% ( P < 0.001). Overall, hypovolemia and positive-pressure ventilation resulted in a reduction of 26% in stroke volume ( P < 0.001) and 13% in cardiac output ( P < 0.001) compared with baseline. Compared with the situation with control-mode positive-pressure ventilation, spontaneous breathing attenuated the reduction in stroke volume induced by moderate hypovolemia by 30% (i.e., −26 vs. −18%). In the patient who is critically ill with hypovolemia or uncontrolled hemorrhage, spontaneous breathing may contribute to hemodynamic stability, whereas controlled positive-pressure ventilation may result in circulatory decompensation. NEW & NOTEWORTHY Maintaining spontaneous respiration has beneficial effects on hemodynamic compensation, which is clinically relevant for patients in intensive care. We have quantified the contribution of the respiratory pump to cardiac stroke volume and cardiac output in healthy volunteers during normovolemia and central hypovolemia. The positive hemodynamic effect of the respiratory pump was abolished by noninvasive, low-level positive-pressure ventilation. Compared with control-mode positive-pressure ventilation, spontaneous negative-pressure ventilation attenuated the fall in stroke volume by 30%.

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Cardiopulmonary effects of continuous pressure breathing in hypothermic dogs

Journal of Applied Physiology ◽

10.1152/jappl.1965.20.4.669 ◽

1965 ◽

Vol 20 (4) ◽

pp. 669-674 ◽

Cited By ~ 4

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

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Continuous external negative pressure improves oxygenation and respiratory mechanics in Experimental Lung Injury in Pigs – A pilot proof-of-concept trial

Intensive Care Medicine Experimental ◽

10.1186/s40635-020-00315-1 ◽

2020 ◽

Vol 8 (S1) ◽

Author(s):

Martin Scharffenberg ◽

Jakob Wittenstein ◽

Moritz Herzog ◽

Sebastian Tauer ◽

Luigi Vivona ◽

...

Keyword(s):

Cardiac Output ◽

Lung Injury ◽

Negative Pressure ◽

Positive Pressure Ventilation ◽

Respiratory Mechanics ◽

Peep Level ◽

Pressure Sensors ◽

Transpulmonary Pressure ◽

Positive Pressure ◽

Impedance Tomography

Abstract Background Continuous external negative pressure (CENP) during positive pressure ventilation can recruit dependent lung regions. We hypothesised that CENP applied regionally to the thorax or the abdomen only, increases the caudal end-expiratory transpulmonary pressure depending on positive end-expiratory pressure (PEEP) in lung-injured pigs. Eight pigs were anesthetised and mechanically ventilated in the supine position. Pressure sensors were placed in the left pleural space, and a lung injury was induced by saline lung lavages. A CENP shell was placed at the abdomen and thorax (randomised order), and animals were ventilated with PEEP 15, 7 and zero cmH2O (15 min each). On each PEEP level, CENP of − 40, − 30, − 20, − 10 and 0 cmH2O was applied (3 min each). Respiratory and haemodynamic variables were recorded. Electrical impedance tomography allowed assessment of centre of ventilation. Results Compared to positive pressure ventilation alone, the caudal transpulmonary pressure was significantly increased by CENP of ≤ 20 cmH2O at all PEEP levels. CENP of – 20 cmH2O reduced the mean airway pressure at zero PEEP (P = 0.025). The driving pressure decreased at CENP of ≤ 10 at PEEP of 0 and 7 cmH2O (P < 0.001 each) but increased at CENP of – 30 cmH2O during the highest PEEP (P = 0.001). CENP of – 30 cmH2O reduced the mechanical power during zero PEEP (P < 0.001). Both elastance (P < 0.001) and resistance (P < 0.001) were decreased at CENP ≤ 30 at PEEP of 0 and 7 cmH2O. Oxygenation increased at CENP of ≤ 20 at PEEP of 0 and 7 cmH2O (P < 0.001 each). Applying external negative pressure significantly shifted the centre of aeration towards dorsal lung regions irrespectively of the PEEP level. Cardiac output decreased significantly at CENP -20 cmH2O at all PEEP levels (P < 0.001). Effects on caudal transpulmonary pressure, elastance and cardiac output were more pronounced when CENP was applied to the abdomen compared with the thorax. Conclusions In this lung injury model in pigs, CENP increased the end-expiratory caudal transpulmonary pressure. This lead to a shift of lung aeration towards dependent zones as well as improved respiratory mechanics and oxygenation, especially when CENP was applied to the abdomen as compared to the thorax. CENP values ≤ 20 cmH2O impaired the haemodynamics.

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Effects of positive end-expiratory pressure on the right ventricle

Journal of Applied Physiology ◽

10.1152/jappl.1986.61.3.819 ◽

1986 ◽

Vol 61 (3) ◽

pp. 819-826 ◽

Cited By ~ 44

Author(s):

R. J. Henning

Keyword(s):

Stroke Volume ◽

Right Ventricular ◽

Positive Pressure Ventilation ◽

Ventricular Volume ◽

Positive Pressure ◽

Right Ventricular Volume ◽

Positive End Expiratory Pressure ◽

Lung Water ◽

Fluid Infusion ◽

Lung Water Content

Transmural cardiac pressures, stroke volume, right ventricular volume, and lung water content were measured in normal dogs and in dogs with oleic acid-induced pulmonary edema (PE) maintained on positive-pressure ventilation. Measurements were performed prior to and following application of 20 cmH2O positive end-expiratory pressure (PEEP). Colloid fluid was given during PEEP for ventricular volume expansion before and after the oleic acid administration. PEEP significantly increased pleural pressure and pulmonary vascular resistance but decreased right ventricular volume, stroke volume, and mean arterial pressure in both normal and PE dogs. Although the fluid infusion during PEEP raised right ventricular diastolic volumes to the pre-PEEP level, the stroke volumes did not significantly increase in either normal dogs or the PE dogs. The fluid infusion, however, significantly increased the lung water content in the PE dogs. Following discontinuation of PEEP, mean arterial pressure, cardiac output, and stroke volume significantly increased, and heart rate did not change. The failure of the stroke volume to increase despite significant right ventricular volume augmentation during PEEP indicates that positive-pressure ventilation with 20 cmH2O PEEP decreases right ventricular function.

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Preoxygenation by spontaneous breathing or noninvasive positive pressure ventilation with and without positive end-expiratory pressure

European Journal of Anaesthesiology ◽

10.1097/eja.0000000000000380 ◽

2016 ◽

Vol 33 (2) ◽

pp. 143-144

Author(s):

Alastair J. Glossop ◽

Antonio M. Esquinas

Keyword(s):

Spontaneous Breathing ◽

Positive Pressure Ventilation ◽

Noninvasive Positive Pressure Ventilation ◽

Positive Pressure ◽

Positive End Expiratory Pressure

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Non-invasive positive-pressure ventilation with positive end-expiratory pressure counteracts inward air leaks during preoxygenation: a randomised crossover controlled study in healthy volunteers

British Journal of Anaesthesia ◽

10.1016/j.bja.2017.12.002 ◽

2018 ◽

Vol 120 (4) ◽

pp. 868-873 ◽

Cited By ~ 7

Author(s):

J.-L. Hanouz ◽

F. Le Gall ◽

J.-L. Gérard ◽

N. Terzi ◽

H. Normand

Keyword(s):

Healthy Volunteers ◽

Positive Pressure Ventilation ◽

Controlled Study ◽

Positive Pressure ◽

Positive End Expiratory Pressure ◽

Non Invasive ◽

Air Leaks

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Simple Device for Producing Continuous Negative Pressure in Infants With IRDS

PEDIATRICS ◽

10.1542/peds.52.1.128 ◽

1973 ◽

Vol 52 (1) ◽

pp. 128-131

Author(s):

Eduardo Bancalari ◽

Tilo Gerhardt ◽

Ellen Monkus

Keyword(s):

Intensive Care Unit ◽

Negative Pressure ◽

Positive Pressure Ventilation ◽

Newborn Infants ◽

Transpulmonary Pressure ◽

Intermittent Positive Pressure Ventilation ◽

Positive Pressure ◽

School Of Medicine ◽

Newborn Intensive Care Unit ◽

Newborn Intensive Care

Increasing experience with the use of continuous transpulmonary pressure, either positive or negative, during the last years has clearly demonstrated the success of this mode of therapy in IRDS.1-3 Forty newborn infants with this disease have been treated with continuous negative pressure (CNP) in the Newborn Intensive Care Unit, Department of Pediatrics, University of Miami School of Medicine, using a modified incubator-respirator.* Twenty-one required only CNP, three of whom died (14%). Among the 19 who needed CNP plus intermittent positive pressure ventilation, nine died (47%). All required more than 70% oxygen to maintain a Pao2 over 50 mm Hg before using CNP.

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