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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

Correlation between changes of oxygenation, shunt and atelectasis in pigs.The differences (deltas) between the two measurement points in pigs (atelectasis in otherwise normal lungs and 12h after induction of ARDS) for PaO2, lnPaO2, shunt and atelectasis were calculated. These repeated measurements were available only for pigs (N = 19). Linear regression of delta-PaO2 (ΔPaO2, left panel), delta-lnPaO2 (ΔlnPaO2, central panel) or delta-shunt (Δshunt, right panel) on the changes in atelectasis (Δatelectasis) was performed. Blood gases were obtained after short-term ventilation with pure oxygen for five minutes. In this figure, atelectasis refers to real atelectasis as well as to the non-aerated lung tissue after induction of ARDS and was quantified as percentage of Mtotal (-100 to 100 HU in computer tomography). Intrapulmonary (Berggren’s) shunt was calculated according to [28]. We transformed PaO2 values logarithmically (lnPaO2) to linearize the relationship between PaO2 and atelectasis.
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pone.0135272.g002: Correlation between changes of oxygenation, shunt and atelectasis in pigs.The differences (deltas) between the two measurement points in pigs (atelectasis in otherwise normal lungs and 12h after induction of ARDS) for PaO2, lnPaO2, shunt and atelectasis were calculated. These repeated measurements were available only for pigs (N = 19). Linear regression of delta-PaO2 (ΔPaO2, left panel), delta-lnPaO2 (ΔlnPaO2, central panel) or delta-shunt (Δshunt, right panel) on the changes in atelectasis (Δatelectasis) was performed. Blood gases were obtained after short-term ventilation with pure oxygen for five minutes. In this figure, atelectasis refers to real atelectasis as well as to the non-aerated lung tissue after induction of ARDS and was quantified as percentage of Mtotal (-100 to 100 HU in computer tomography). Intrapulmonary (Berggren’s) shunt was calculated according to [28]. We transformed PaO2 values logarithmically (lnPaO2) to linearize the relationship between PaO2 and atelectasis.

Mentions: Lung injury by instillation of hydrochloric acid led to impairment of oxygenation and lung mechanics compatible with the current criteria for severe human ARDS [39] in all animals (PaO2 at FIO2 = 1.0 was 81 (66–97) mmHg at the diagnosis of ARDS). Measurements in pigs 12 hours after induction of ARDS showed an increased correlation between PaO2 and atelectasis (R2 = 0.79, P<0.0001), lnPaO2 and atelectasis (R2 = 0.72, P<0.0001) and between atelectasis and shunt (R2 = 0.75, P<0.0001) (see also Table 1). Also in pigs, the differences (delta) between the two measurement points in pigs (atelectasis in otherwise normal lungs and 12h after induction of ARDS) for PaO2, lnPaO2 or shunt correlated well with the changes in atelectasis between both measurement points (R2 = 0.89, 0.88 and 0.79 for the regression of PaO2, lnPaO2 or shunt, respectively, on atelectasis; P<0.0001; Fig 2).


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)

Correlation between changes of oxygenation, shunt and atelectasis in pigs.The differences (deltas) between the two measurement points in pigs (atelectasis in otherwise normal lungs and 12h after induction of ARDS) for PaO2, lnPaO2, shunt and atelectasis were calculated. These repeated measurements were available only for pigs (N = 19). Linear regression of delta-PaO2 (ΔPaO2, left panel), delta-lnPaO2 (ΔlnPaO2, central panel) or delta-shunt (Δshunt, right panel) on the changes in atelectasis (Δatelectasis) was performed. Blood gases were obtained after short-term ventilation with pure oxygen for five minutes. In this figure, atelectasis refers to real atelectasis as well as to the non-aerated lung tissue after induction of ARDS and was quantified as percentage of Mtotal (-100 to 100 HU in computer tomography). Intrapulmonary (Berggren’s) shunt was calculated according to [28]. We transformed PaO2 values logarithmically (lnPaO2) to linearize the relationship between PaO2 and atelectasis.
© Copyright Policy
Related In: Results  -  Collection

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

pone.0135272.g002: Correlation between changes of oxygenation, shunt and atelectasis in pigs.The differences (deltas) between the two measurement points in pigs (atelectasis in otherwise normal lungs and 12h after induction of ARDS) for PaO2, lnPaO2, shunt and atelectasis were calculated. These repeated measurements were available only for pigs (N = 19). Linear regression of delta-PaO2 (ΔPaO2, left panel), delta-lnPaO2 (ΔlnPaO2, central panel) or delta-shunt (Δshunt, right panel) on the changes in atelectasis (Δatelectasis) was performed. Blood gases were obtained after short-term ventilation with pure oxygen for five minutes. In this figure, atelectasis refers to real atelectasis as well as to the non-aerated lung tissue after induction of ARDS and was quantified as percentage of Mtotal (-100 to 100 HU in computer tomography). Intrapulmonary (Berggren’s) shunt was calculated according to [28]. We transformed PaO2 values logarithmically (lnPaO2) to linearize the relationship between PaO2 and atelectasis.
Mentions: Lung injury by instillation of hydrochloric acid led to impairment of oxygenation and lung mechanics compatible with the current criteria for severe human ARDS [39] in all animals (PaO2 at FIO2 = 1.0 was 81 (66–97) mmHg at the diagnosis of ARDS). Measurements in pigs 12 hours after induction of ARDS showed an increased correlation between PaO2 and atelectasis (R2 = 0.79, P<0.0001), lnPaO2 and atelectasis (R2 = 0.72, P<0.0001) and between atelectasis and shunt (R2 = 0.75, P<0.0001) (see also Table 1). Also in pigs, the differences (delta) between the two measurement points in pigs (atelectasis in otherwise normal lungs and 12h after induction of ARDS) for PaO2, lnPaO2 or shunt correlated well with the changes in atelectasis between both measurement points (R2 = 0.89, 0.88 and 0.79 for the regression of PaO2, lnPaO2 or shunt, respectively, on atelectasis; P<0.0001; Fig 2).

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