title: [Effect of mean arterial pressure on arterial to end-tidal CO₂partial pressure difference during one-lung ventilation].
abstract: OBJECTIVE
  To study the effect of different mean arterial pressures (MAP) on arterial to end-tidal CO₂partial pressure difference [(Pa-et)CO₂] and the intrapulmonary shunt (Qs/Qt) in patients undergoing thoracic surgery during one-lung ventilation (OLV).
  
  
  METHODS
  Forty-two patients undergoing right-sided pulmonary lobectomy were allocated into group A with fluctuation of MAP (at 20 min after OLV) within ± 10% of the baseline (n=22) and group B with lowered MAP by 30% of the baseline (n=20). Arterial and venous blood gas analyses were recorded to calculate [(Pa-et)CO₂] and Qs/Qt at 20 min after induction with two-lung ventilation (T₁), 20 min after OLV (T₂), 30 min after recovery of normal blood pressure (T₃), and 20 min after recovery of two-lung ventilation (T₄).
  
  
  RESULTS
  PetCO₂and PaCO₂were well correlated during two-lung ventilation and OLV in group A (P<0.05). In group B, [(Pa-et)CO₂] at T₂was significantly higher than that in group A, but PetCO₂was still correlated with PaCO₂(P<0.05). Qs/Qt increased more obviously in group B than in group A in T₂(P<0.05). Bo obvious correlation was found between the [(Pa-et)CO₂] and Qs/Qt during OLV.
  
  
  CONCLUSIONS
  PetCO₂reflects the dynamic changes of PaCO₂under normal blood pressure during OLV. In the hypotension period, when [(Pa-et)CO₂] increases and the correlation coefficient between PetCO₂and PaCO₂lowers, PetCO₂may not accurately reflect the changes of PaCO₂and blood gas analysis is warranted.
authors.affiliation: Department of Anesthesiology, Nanfang Hospital, Southern Medical University, Guangzhou 510515, China.E-mail: xiaozhao0601@126.com.
authors.forename: Zhao-Yan
authors.initials: ZY
authors.lastname: Zeng
authors.forename: Jing
authors.initials: J
authors.lastname: Ye
authors.forename: Zhen-Long
authors.initials: ZL
authors.lastname: Zhao
authors.forename: Zai-Sheng
authors.initials: ZS
authors.lastname: Qin
mesh_terms: D062186:Arterial Pressure; D001784:Blood Gas Analysis; D002245:Carbon Dioxide / Q000032:analysis; D006801:Humans; D008168:Lung / Q000601:surgery; D008991:Monitoring, Physiologic; D061810:One-Lung Ventilation; D010100:Oxygen / Q000032:analysis; D019616:Thoracic Surgical Procedures
chemical_list: D002245:Carbon Dioxide; D010100:Oxygen