Spontaneous Breathing Improves Shunt Fraction and Oxygenation in Comparison with Controlled Ventilation at a Similar Amount of Lung Collapse

Vimláti, L; Kawati, Rafael; Hedenstierna, Göran; Larsson, Anders; Lichtwarck-Aschoff, Michael

doi:10.1213/ane.0b013e31822ceef8

Cited by 19 publications

(19 citation statements)

References 25 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…27 We cannot categorically exclude that regional ventilation, rather than regional perfusion, was modulated by the ventilatory mode. This is, however, rather unlikely, as (1) in our earlier studies with almost 40% of the lung tissue atelectatic we found no substantial recruitment of lung collapse within 30 min, during neither SB nor MV 5 ; and (2) in supine pigs, during mechanical ventilation at a fraction of inspired oxygen of 1.0 and with CO comparable to that seen with unrestricted venous return in the present study, the multiple inert gas elimination technique shows complete absence of areas with a low ventilation/perfusion ratio (0.001-0.1) during one-lung ventilation, 28 whose improvement in regional ventilation could decrease pulmonary shunt. Furthermore, as each ventilatory mode served as its own control during CO modulation, lung recruitment could not explain our observations.…”

Section: Discussioncontrasting

confidence: 57%

“…Pure oxygen breathing during the preparation with healthy lungs resulted in minor shunt 5 13 (Cook Medical, Inc., Bloomington, In), placed and inflated in the left main bronchus under fiberoptic control. Disconnecting the entire left lung from ventilation created a pulmonary shunt that was not recruitable by increased airway pressures.…”

Section: Experimental Protocolmentioning

confidence: 99%

“…Recent studies suggest an SB-induced improvement of ventilation/perfusion matching independent of reopening collapsed areas. 4,5 During MV, increasing cardiac output (CO) concomitantly augments pulmonary shunt, which is explained by a progressive inhibition of hypoxic pulmonary vasoconstriction (HPV). Raising CO increases mixed-venous oxygen tension (PvO 2 ), and this results in higher oxygen tension at the HPV sensor site, attenuating the hypoxic vasoconstrictor response.…”

mentioning

confidence: 99%

See 2 more Smart Citations

Pulmonary Shunt Is Independent of Decrease in Cardiac Output during Unsupported Spontaneous Breathing in the Pig

et al. 2013

Self Cite

View full text Add to dashboard Cite

Background: During mechanical ventilation (MV), pulmonary shunt is cardiac output (CO) dependent; however, whether this relationship is valid during unsupported spontaneous breathing (SB) is unknown. The CO dependency of the calculated venous admixture was investigated, with both minor and major shunt, during unsupported SB, MV, and SB with continuous positive airway pressure (CPAP). Methods: In seven anesthetized supine piglets breathing 100% oxygen, unsupported SB, MV (with tidal volume and respiratory rate corresponding to SB), and 8 cm H 2 O CPAP (airway pressure corresponding to MV) were applied at random. Venous return and CO were reduced by partial balloon occlusion of the inferior vena cava. Measurements were repeated with the left main bronchus blocked, creating a nonrecruitable pulmonary shunt. Results: CO decreased from 4.2 l/min (95% CI, 3.9-4.5) to 2.5 l/min (95% CI, 2.2-2.7) with partially occluded venous return. Irrespective of whether shunt was minor or major, during unsupported SB, venous admixture was independent of CO (slope: minor shunt, 0.5; major shunt, 1.1%·min −1 ·l −1 ) and mixed venous oxygen tension. During both MV and CPAP, venous admixture was dependent on CO (slope MV: minor shunt, 1.9; major shunt, 3.5; CPAP: minor shunt, 1.3; major shunt, 2.9%·min) and mixedvenous oxygen tension (coefficient of determination 0.61-0.86 for all regressions). Conclusions: In contrast to MV and CPAP, venous admixture was independent of CO during unsupported SB, and was unaffected by mixed-venous oxygen tension, casting doubt on the role of hypoxic pulmonary vasoconstriction in pulmonary blood flow redistribution during unsupported SB.

show abstract

Section: Discussioncontrasting

confidence: 57%

Section: Experimental Protocolmentioning

confidence: 99%

mentioning

confidence: 99%

See 1 more Smart Citation

Pulmonary Shunt Is Independent of Decrease in Cardiac Output during Unsupported Spontaneous Breathing in the Pig

et al. 2013

Self Cite

View full text Add to dashboard Cite

show abstract

“…During assisted spontaneous breathing in the supine position, improvements in gas exchange are not necessarily accompanied by increased aerated lung tissue [20,21]. Interestingly, pulmonary blood flow redistributes from dorsal, less aerated, to ventral, better aerated lung regions, improving global ventilation-perfusion matching [15].…”

Section: Key Pointsmentioning

confidence: 99%

“…For example, during assisted spontaneous breathing, redistribution of pulmonary blood flow toward nondependent regions may be impaired in presence of inflammation, due to blunted hypoxic vasoconstriction. Furthermore, inappropriate levels of positive end-expiratory pressure (PEEP) may counteract lung recruitment during unassisted spontaneous breathing [21].…”

Section: Key Pointsmentioning

confidence: 99%

Spontaneous breathing in mild and moderate versus severe acute respiratory distress syndrome

Güldner¹,

Pelosi²,

Abreu³

2014

Current Opinion in Critical Care

View full text Add to dashboard Cite

show abstract

Hypoxia in the pulmonary vein increases pulmonary vascular resistance independently of oxygen in the pulmonary artery

Magnusdottir,

Simonsen,

Karbing

et al. 2024

Anim Models and Exp Med

View full text Add to dashboard Cite

IntroductionHypoxic pulmonary vasoconstriction (HPV) can be a challenging clinical problem. It is not fully elucidated where in the circulation the regulation of resistance takes place. It is often referred to as if it is in the arteries, but we hypothesized that it is in the venous side of the pulmonary circulation.MethodsIn an open thorax model, pigs were treated with a veno‐venous extra corporeal membrane oxygenator to either oxygenate or deoxygenate blood passing through the pulmonary vessels. At the same time the lungs were ventilated with extreme variations of inspired air from 5% to 100% oxygen, making it possible to make combinations of high and low oxygen content through the pulmonary circulation. A flow probe was inserted around the main pulmonary artery and catheters in the pulmonary artery and in the left atrium were used for pressure monitoring and blood tests. Under different combinations of oxygenation, pulmonary vascular resistance (PVR) was calculated.ResultsWith unchanged level of oxygen in the pulmonary artery and reduced inspired oxygen fraction lowering oxygen tension from 29 to 6.7 kPa in the pulmonary vein, PVR was doubled. With more extreme hypoxia PVR suddenly decreased. Combinations with low oxygenation in the pulmonary artery did not systematic influence PVR if there was enough oxygen in the inspired air and in the pulmonary veins.DiscussionThe impact of hypoxia occurs from the alveolar level and forward with the blood flow. The experiments indicated that the regulation of PVR is mediated from the venous side.

show abstract

Spontaneous Breathing Improves Shunt Fraction and Oxygenation in Comparison with Controlled Ventilation at a Similar Amount of Lung Collapse

Abstract: SB without any support improves oxygenation and reduces shunt in comparison with MV at identical settings. This seems to be achieved without any major signs of recruitment of collapsed lung regions.

Cited by 19 publications

References 25 publications

Pulmonary Shunt Is Independent of Decrease in Cardiac Output during Unsupported Spontaneous Breathing in the Pig

Pulmonary Shunt Is Independent of Decrease in Cardiac Output during Unsupported Spontaneous Breathing in the Pig

Spontaneous breathing in mild and moderate versus severe acute respiratory distress syndrome

Hypoxia in the pulmonary vein increases pulmonary vascular resistance independently of oxygen in the pulmonary artery

Contact Info

Product

Resources

About