Regional maps of volumetric lung strain in healthy anesthetized dogs ventilated with varying tidal volumes and positive end-expiratory pressure (PEEP)

We have investigated the effect of positive end-expiratory pressure ventilation (PEEP) on regional splanchnic vascular capacitance. In 12 anesthetized dogs hepatic and splenic blood volumes were assessed by sonomicrometry. Vascular pressure-diameter curves were defined by obstructing hepatic outflow. With 10 and 15 cmH2O PEEP portal venous pressure increased 3.1 +/- 0.3 and 5.1 +/- 0.4 mmHg (P less than 0.001) while hepatic venous pressure increased 4.9 +/- 0.4 and 7.3 +/- 0.4 mmHg (P less than 0.001), respectively. Hepatic blood volume increased (P less than 0.01) 3.8 +/- 0.9 and 6.3 +/- 1.4 ml/kg body wt while splenic volume decreased (P less than 0.01) 0.8 +/- 0.2 and 1.3 +/- 0.2 ml/kg body wt. The changes were similar with closed abdomen. The slope of the hepatic vascular pressure-diameter curves decreased with PEEP (P less than 0.01), possibly reflecting reduced vascular compliance. There was an increase (P less than 0.01) in unstressed hepatic vascular volume. The slope of the splenic pressure-diameter curves was unchanged, but there was a significant (P less than 0.05) decrease in unstressed diameter during PEEP. In conclusion, hepatic blood volume increased during PEEP. This was mainly a reflection of passive distension due to elevated venous pressures. The spleen expelled blood and thus prevented a further reduction in central blood volume.

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Ventilation distribution assessed with electrical impedance tomography and the influence of tidal volume, recruitment and positive end-expiratory pressure in isoflurane-anesthetized dogs

Veterinary Anaesthesia and Analgesia ◽

10.1016/j.vaa.2016.06.003 ◽

2017 ◽

Vol 44 (2) ◽

pp. 254-263

Author(s):

Aline M. Ambrosio ◽

Tatiana P.A. Carvalho-Kamakura ◽

Keila K. Ida ◽

Barbara Varela ◽

Felipe S.R.M. Andrade ◽

...

Keyword(s):

Tidal Volume ◽

Electrical Impedance Tomography ◽

Electrical Impedance ◽

Positive End Expiratory Pressure ◽

Ventilation Distribution ◽

Impedance Tomography ◽

Anesthetized Dogs

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Reflex mechanisms for changes in renal nerve activity during positive end-expiratory pressure

Journal of Applied Physiology ◽

10.1152/jappl.1988.65.1.109 ◽

1988 ◽

Vol 65 (1) ◽

pp. 109-115 ◽

Cited By ~ 4

Author(s):

M. Aibiki ◽

S. Koyama ◽

K. Ogli ◽

Y. Shirakawa

Keyword(s):

Carotid Sinus ◽

Venous Pressure ◽

Control Level ◽

Vagal Afferents ◽

Positive End Expiratory Pressure ◽

Nerve Activity ◽

Renal Nerve ◽

Renal Nerve Activity ◽

Anesthetized Dogs ◽

Cardiopulmonary Receptors

This study was designed to investigate the interaction between carotid sinus baroreceptors and cardiopulmonary receptors in the reflex control of renal nerve activity (RNA) during positive end-expiratory pressure (PEEP) in anesthetized dogs. PEEP at two different levels (10 and 20 cmH2O) was applied to the following groups: animals with neuraxis intact (I group, n = 12); vagal and aortic nerve denervated animals with carotid sinus nerves intact (V group, n = 6); carotid sinus denervated animals with vagal and aortic nerves intact (SD group, n = 6); and carotid sinus denervated animals also having severed vagal and aortic nerves (SAV group, n = 12). Mean blood pressure (MBP), central venous pressure, and mean airway pressure were also simultaneously measured. In the I group, no significant alterations in RNA occurred during PEEP at both levels, even when MBP fell significantly. Although the drop in MBP in the SD group was similar to that in the I group, RNA decreased significantly 10 s after intervention at both PEEP levels, followed by a recovery of RNA toward the control level. In contrast, a significant increase in RNA, which continued until the end of PEEP, appeared in the V group immediately after each intervention. In the SAV group, RNA responses to PEEP, which were observed in the other groups, were abolished. These results provide evidence that during PEEP, renal nerve activity is modified by an interaction between carotid sinus baroreceptors and cardiopulmonary receptors; excitatory effects occur via carotid sinus nerves and inhibitory effects occur via vagal afferents.

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Effect of PEEP on discharge of pulmonary C-fibers in dogs

Journal of Applied Physiology ◽

10.1152/jappl.1985.59.4.1085 ◽

1985 ◽

Vol 59 (4) ◽

pp. 1085-1089 ◽

Cited By ~ 3

Author(s):

M. P. Kaufman ◽

G. A. Ordway ◽

T. G. Waldrop

Keyword(s):

Cardiac Output ◽

Arterial Pressure ◽

Impulse Activity ◽

Vena Cava ◽

Laboratory Animals ◽

Positive End Expiratory Pressure ◽

Firing Rates ◽

C Fibers ◽

Anesthetized Dogs ◽

Stimulation Of

Although positive end-expiratory pressure (PEEP) is believed to depress cardiac output and arterial pressure by compressing the vena cava and the heart, it is unclear whether PEEP also depresses these variables by a reflex arising from an inflation-induced stimulation of pulmonary C-fibers. We therefore recorded the impulse activity of 17 pulmonary C-fibers in barbiturate-anesthetized dogs with closed chests, while we placed the expiratory outlet of a ventilator under 5–30 cmH2O. Increasing PEEP in a ramp-like manner stimulated 12 of the 17 pulmonary C-fibers, with activity increasing from 0.0 +/- 0.1 to 0.9 +/- 0.2 imp/s when end-expiratory pressure equaled 15 cmH2O. When PEEP was increased in a stepwise manner to 15–20 cmH2O and maintained at this pressure for 15 min, pulmonary C-fibers increased their firing rates, but the effect was small averaging 0.2–0.3 imp/s after the 1st min of this maneuver. We conclude that pulmonary C-fibers are unlikely to be responsible for causing much of the decreases in cardiac output and arterial pressure evoked by sustained periods of PEEP in both patients and laboratory animals. These C-fibers, however, are likely to be responsible for causing the reflex decreases in these variables evoked by sudden application of PEEP.

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Simple computer measurement of pulmonary VCO2 per breath

Journal of Applied Physiology ◽

10.1152/jappl.1992.72.5.2029 ◽

1992 ◽

Vol 72 (5) ◽

pp. 2029-2035 ◽

Cited By ~ 28

Author(s):

P. H. Breen ◽

S. A. Isserles ◽

B. A. Harrison ◽

M. F. Roizen

Keyword(s):

Co2 Concentration ◽

Computer Algorithms ◽

Positive End Expiratory Pressure ◽

Transport Delay ◽

A Value ◽

Wide Range ◽

Airway Opening ◽

Anesthetized Dogs ◽

On Line ◽

End Tidal

Measurements of the volume of CO2 exhaled per breath (VCO2/br) are preferable to end-tidal PCO2, when the exhaled flow and CO2 waveforms may be changing during unsteady states, such as during alterations in positive end-expiratory pressure or alterations in cardiac output. We describe computer algorithms that determine VCO2/br from digital measurements of exhaled flow (including discontinuous signals common in anesthesia circuits) and CO2 concentration at the airway opening. Fractional concentration of CO2 is normally corrected for dynamic response and transport delay (TD), measured in a separate procedure. Instead, we determine an on-line adjusted TD during baseline ventilation. In six anesthetized dogs, we compared the determination of VCO2/br with a value measured in a simultaneous collection of expired gas. Over a wide range of tidal volume (180–700 ml), respiratory rate (3–30 min-1), and positive end-expiratory pressure (0–14 cmH2O), VCO2/br was more accurate with use of the adjusted TD than the measured TD (P less than 0.05).

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Effect of positive end-expiratory pressure on canine ventricular function curves

Journal of Applied Physiology ◽

10.1152/jappl.1981.51.6.1367 ◽

1981 ◽

Vol 51 (6) ◽

pp. 1367-1374 ◽

Cited By ~ 61

Author(s):

J. J. Marini ◽

B. H. Culver ◽

J. Butler

Keyword(s):

Ventricular Function ◽

Ventricular Dysfunction ◽

Transmural Pressure ◽

Positive End Expiratory Pressure ◽

Hemodynamic Changes ◽

Venous Flow ◽

Cardiac Depression ◽

Before And After ◽

Anesthetized Dogs ◽

The Right

Recent observations have been interpreted to suggest altered ventricular function during ventilation with positive end-expiratory pressure (PEEP), apart from the effect of reduced preload. We constructed ventricular function curves in 14 anesthetized dogs as PEEP was varied under closed- and open-chest conditions. The systemic venous flow of the animal was diverted through an external circuit so that blood return to the right atrium could be varied stepwise from 1--4.5 l/min before and after 15 cmH2O PEEP was applied to the airway. Pressures adjacent to the heart were measured with thin fluid-filled water sensors to enable estimation of transmural pressure. Alterations in ventricular function were assessed by comparing tangential slopes as well as the atrial pressure differences separating the curves at high and low stroke volumes. Sensitivity of this method to cardiac depression was demonstrated by similar comparisons made before and after propranolol. Curves using transmural pressure on and off PEEP were statistically indistinguishable. We conclude that hemodynamic changes resulting from PEEP are attributable to the combined effects of reduced preload and raised juxtacardiac pressure, without ventricular dysfunction.

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Pulmonary Blood Flow Redistribution with Low Levels of Positive End-expiratory Pressure

Anesthesiology ◽

10.1097/00000542-199805000-00021 ◽

1998 ◽

Vol 88 (5) ◽

pp. 1291-1299 ◽

Cited By ~ 22

Author(s):

Harry J. Kallas ◽

Karen B. Domino ◽

Robb W. Glenny ◽

Emily A. Anderson ◽

Michael P. Hlastala

Keyword(s):

Blood Flow ◽

Pulmonary Blood Flow ◽

Zone Model ◽

Structural Factors ◽

Positive End Expiratory Pressure ◽

Mechanically Ventilated ◽

Anesthetized Dogs ◽

Low Levels ◽

Ventilation And Perfusion ◽

Lung Zone

Background Recent studies have questioned the importance of the gravitational model of pulmonary perfusion. Because low levels of positive end-expiratory pressure (PEEP) are commonly used during anesthesia, the authors studied the distribution of pulmonary blood flow with low levels of PEEP using a high spatial resolution technique. They hypothesized that if hydrostatic factors were important in the distribution of pulmonary blood flow, PEEP would redistribute flow to more dependent lung regions. Methods The effects of zero cm H2O PEEP and 5 cm H2O PEEP on pulmonary gas exchange were studied using the multiple inert gas elimination technique; the distribution of pulmonary blood flow, using fluorescent-labeled microspheres, was also investigated in mechanically ventilated, pentobarbital-anesthetized dogs. The lungs were removed, cleared of blood, dried at total lung capacity, and then cubed to obtain approximately 1,000 small pieces of lung (approximately 1.7 cm3). Results Positive end-expiratory pressure increased the partial pressure of oxygen by 6 +/- 2 mmHg (P < 0.05) and reduced all measures of ventilation and perfusion heterogeneity (P < 0.05). By reducing flow to nondependent ventral lung regions and increasing flow to dependent dorsal lung regions, PEEP increased (P < 0.05) the dorsal-to-ventral gradient. Redistribution of blood flow with PEEP accounted for 7 +/- 3%, whereas structural factors accounted for 93 +/- 3% of the total variance in blood flow. Conclusions The increase in dependent-to-nondependent gradient with PEEP is partially consistent with the gravitationally based lung zone model. However, the results emphasize the greater importance of anatomic factors in determining the distribution of pulmonary blood flow.

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Regional distribution of static lung strain induced by positive-end expiratory pressure (PEEP) in healthy, dorsally recumbent, anesthetized and mechanically ventilated dogs

Veterinary Anaesthesia and Analgesia ◽

10.1016/j.vaa.2020.07.004 ◽

2020 ◽

Vol 47 (6) ◽

pp. 855.e1

Author(s):

J. Araos ◽

T. Boullhesen-Williams ◽

A. Perez ◽

J. Retamal ◽

M. Martin-Flores ◽

...

Keyword(s):

Regional Distribution ◽

Positive End Expiratory Pressure ◽

Mechanically Ventilated ◽

Lung Strain

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Extrapericardial and esophageal pressures with positive end-expiratory pressure in dogs

Journal of Applied Physiology ◽

10.1152/jappl.1981.51.4.798 ◽

1981 ◽

Vol 51 (4) ◽

pp. 798-805 ◽

Cited By ~ 22

Author(s):

K. D. Craven ◽

L. D. Wood

Keyword(s):

Stroke Volume ◽

Esophageal Pressure ◽

Confidence Limits ◽

Positive End Expiratory Pressure ◽

Local Surface ◽

Closed Chest ◽

Increase Stroke Volume ◽

Anesthetized Dogs ◽

Lateral Decubitus ◽

The Right

Using flat balloon techniques to minimize distortion and artifacts, we studied the effect of positive end-expiratory pressure (PEEP) on local surface pressures between the lung and pericardium overlying the right (R) and left (L) ventricles of ventilated closed-chest anesthetized dogs in right lateral decubitus position. To test the hypothesis that local extrapericardial [Pep(L) and Pep(R)] and average pleural pressures change equally with PEEP, we also measured esophageal pressure (Pes). When 10-cmH2O PEEP was applied, mean increases in Pes, Pep(L), and Pep(R) were 6.2, 5.6, and 5.3 cmH2O, respectively. When PEEP was raised to 20 cmH2O, further average increases in Pes, Pep(L), and Pep(R) were 5.8, 5.0, and 5.4 cmH2O. At each level of PEEP, volume infusion was used to increase stroke volume. Volume infusion at 20-cmH2O PEEP was associated with small 1.0- and 1.5-cmH2O increases in Pep but no change in Pes. Analysis of confidence limits showed that application of up to 20-cmH2O PEEP, with or without volume infusion to restore stroke volume, is associated with nearly equal changes in esophageal and local extrapericardial pressures.

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