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Correlation of lung collapse and gas exchange - a computer tomographic study in sheep and pigs with atelectasis in otherwise normal lungs.

Wolf SJ, Reske AP, Hammermüller S, Costa EL, Spieth PM, Hepp P, Carvalho AR, Kraßler J, Wrigge H, Amato MB, Reske AW - PLoS ONE (2015)

Bottom Line: Shunt was 39 (29-51) % in sheep and 15 (11-20) % in pigs.In lung-healthy pigs, these correlations were significantly weaker, likely because pigs have stronger hypoxic pulmonary vasoconstriction (HPV) than sheep and humans.Nevertheless, correlations improved also in pigs after blunting of HPV during ARDS.

View Article: PubMed Central - PubMed

Affiliation: Department of Anaesthesiology and Intensive Care Medicine, University Hospital Leipzig, Leipzig, Germany.

ABSTRACT

Background: Atelectasis can provoke pulmonary and non-pulmonary complications after general anaesthesia. Unfortunately, there is no instrument to estimate atelectasis and prompt changes of mechanical ventilation during general anaesthesia. Although arterial partial pressure of oxygen (PaO2) and intrapulmonary shunt have both been suggested to correlate with atelectasis, studies yielded inconsistent results. Therefore, we investigated these correlations.

Methods: Shunt, PaO2 and atelectasis were measured in 11 sheep and 23 pigs with otherwise normal lungs. In pigs, contrasting measurements were available 12 hours after induction of acute respiratory distress syndrome (ARDS). Atelectasis was calculated by computed tomography relative to total lung mass (Mtotal). We logarithmically transformed PaO2 (lnPaO2) to linearize its relationships with shunt and atelectasis. Data are given as median (interquartile range).

Results: Mtotal was 768 (715-884) g in sheep and 543 (503-583) g in pigs. Atelectasis was 26 (16-47) % in sheep and 18 (13-23) % in pigs. PaO2 (FiO2 = 1.0) was 242 (106-414) mmHg in sheep and 480 (437-514) mmHg in pigs. Shunt was 39 (29-51) % in sheep and 15 (11-20) % in pigs. Atelectasis correlated closely with lnPaO2 (R2 = 0.78) and shunt (R2 = 0.79) in sheep (P-values<0.0001). The correlation of atelectasis with lnPaO2 (R2 = 0.63) and shunt (R2 = 0.34) was weaker in pigs, but R2 increased to 0.71 for lnPaO2 and 0.72 for shunt 12 hours after induction of ARDS. In both, sheep and pigs, changes in atelectasis correlated strongly with corresponding changes in lnPaO2 and shunt.

Discussion and conclusion: In lung-healthy sheep, atelectasis correlates closely with lnPaO2 and shunt, when blood gases are measured during ventilation with pure oxygen. In lung-healthy pigs, these correlations were significantly weaker, likely because pigs have stronger hypoxic pulmonary vasoconstriction (HPV) than sheep and humans. Nevertheless, correlations improved also in pigs after blunting of HPV during ARDS. In humans, the observed relationships may aid in assessing anaesthesia-related atelectasis.

No MeSH data available.


Related in: MedlinePlus

Agreement of shunt and atelectasis.Bland-Altman plots for analysis of the agreement of intrapulmonary (Berggren’s) shunt and atelectasis, when the latter was quantified by analysis of whole-lung CT and expressed as percentage of the total lung mass for sheep (left) and pigs (right) using an atelectasis definition of -100 to +100 HU (top) or an extended range of -200 to +100 HU (bottom). Shunt is plotted on the x-axis because it is considered the gold standard. The difference plotted on the y-axis was calculated by subtraction of shunt from atelectasis. Solid line: mean difference (bias), dashed lines: 95% limits of agreement (mean difference ± 1.96 SD). Blood gases were obtained after short-term ventilation with pure oxygen for five minutes.
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pone.0135272.g003: Agreement of shunt and atelectasis.Bland-Altman plots for analysis of the agreement of intrapulmonary (Berggren’s) shunt and atelectasis, when the latter was quantified by analysis of whole-lung CT and expressed as percentage of the total lung mass for sheep (left) and pigs (right) using an atelectasis definition of -100 to +100 HU (top) or an extended range of -200 to +100 HU (bottom). Shunt is plotted on the x-axis because it is considered the gold standard. The difference plotted on the y-axis was calculated by subtraction of shunt from atelectasis. Solid line: mean difference (bias), dashed lines: 95% limits of agreement (mean difference ± 1.96 SD). Blood gases were obtained after short-term ventilation with pure oxygen for five minutes.

Mentions: Except for large amounts of atelectasis (>50%), shunt systematically exceeded atelectasis in sheep but not in pigs. The bias between shunt and atelectasis was -9.5% (LOA -28.6 to 9.6%) and 2.8% (LOA -8.3 to 13.8%) in sheep and pigs, respectively (Fig 3).


Correlation of lung collapse and gas exchange - a computer tomographic study in sheep and pigs with atelectasis in otherwise normal lungs.

Wolf SJ, Reske AP, Hammermüller S, Costa EL, Spieth PM, Hepp P, Carvalho AR, Kraßler J, Wrigge H, Amato MB, Reske AW - PLoS ONE (2015)

Agreement of shunt and atelectasis.Bland-Altman plots for analysis of the agreement of intrapulmonary (Berggren’s) shunt and atelectasis, when the latter was quantified by analysis of whole-lung CT and expressed as percentage of the total lung mass for sheep (left) and pigs (right) using an atelectasis definition of -100 to +100 HU (top) or an extended range of -200 to +100 HU (bottom). Shunt is plotted on the x-axis because it is considered the gold standard. The difference plotted on the y-axis was calculated by subtraction of shunt from atelectasis. Solid line: mean difference (bias), dashed lines: 95% limits of agreement (mean difference ± 1.96 SD). Blood gases were obtained after short-term ventilation with pure oxygen for five minutes.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4530863&req=5

pone.0135272.g003: Agreement of shunt and atelectasis.Bland-Altman plots for analysis of the agreement of intrapulmonary (Berggren’s) shunt and atelectasis, when the latter was quantified by analysis of whole-lung CT and expressed as percentage of the total lung mass for sheep (left) and pigs (right) using an atelectasis definition of -100 to +100 HU (top) or an extended range of -200 to +100 HU (bottom). Shunt is plotted on the x-axis because it is considered the gold standard. The difference plotted on the y-axis was calculated by subtraction of shunt from atelectasis. Solid line: mean difference (bias), dashed lines: 95% limits of agreement (mean difference ± 1.96 SD). Blood gases were obtained after short-term ventilation with pure oxygen for five minutes.
Mentions: Except for large amounts of atelectasis (>50%), shunt systematically exceeded atelectasis in sheep but not in pigs. The bias between shunt and atelectasis was -9.5% (LOA -28.6 to 9.6%) and 2.8% (LOA -8.3 to 13.8%) in sheep and pigs, respectively (Fig 3).

Bottom Line: Shunt was 39 (29-51) % in sheep and 15 (11-20) % in pigs.In lung-healthy pigs, these correlations were significantly weaker, likely because pigs have stronger hypoxic pulmonary vasoconstriction (HPV) than sheep and humans.Nevertheless, correlations improved also in pigs after blunting of HPV during ARDS.

View Article: PubMed Central - PubMed

Affiliation: Department of Anaesthesiology and Intensive Care Medicine, University Hospital Leipzig, Leipzig, Germany.

ABSTRACT

Background: Atelectasis can provoke pulmonary and non-pulmonary complications after general anaesthesia. Unfortunately, there is no instrument to estimate atelectasis and prompt changes of mechanical ventilation during general anaesthesia. Although arterial partial pressure of oxygen (PaO2) and intrapulmonary shunt have both been suggested to correlate with atelectasis, studies yielded inconsistent results. Therefore, we investigated these correlations.

Methods: Shunt, PaO2 and atelectasis were measured in 11 sheep and 23 pigs with otherwise normal lungs. In pigs, contrasting measurements were available 12 hours after induction of acute respiratory distress syndrome (ARDS). Atelectasis was calculated by computed tomography relative to total lung mass (Mtotal). We logarithmically transformed PaO2 (lnPaO2) to linearize its relationships with shunt and atelectasis. Data are given as median (interquartile range).

Results: Mtotal was 768 (715-884) g in sheep and 543 (503-583) g in pigs. Atelectasis was 26 (16-47) % in sheep and 18 (13-23) % in pigs. PaO2 (FiO2 = 1.0) was 242 (106-414) mmHg in sheep and 480 (437-514) mmHg in pigs. Shunt was 39 (29-51) % in sheep and 15 (11-20) % in pigs. Atelectasis correlated closely with lnPaO2 (R2 = 0.78) and shunt (R2 = 0.79) in sheep (P-values<0.0001). The correlation of atelectasis with lnPaO2 (R2 = 0.63) and shunt (R2 = 0.34) was weaker in pigs, but R2 increased to 0.71 for lnPaO2 and 0.72 for shunt 12 hours after induction of ARDS. In both, sheep and pigs, changes in atelectasis correlated strongly with corresponding changes in lnPaO2 and shunt.

Discussion and conclusion: In lung-healthy sheep, atelectasis correlates closely with lnPaO2 and shunt, when blood gases are measured during ventilation with pure oxygen. In lung-healthy pigs, these correlations were significantly weaker, likely because pigs have stronger hypoxic pulmonary vasoconstriction (HPV) than sheep and humans. Nevertheless, correlations improved also in pigs after blunting of HPV during ARDS. In humans, the observed relationships may aid in assessing anaesthesia-related atelectasis.

No MeSH data available.


Related in: MedlinePlus