title: Change in pulmonary blood volume changes pulmonary artery systolic storage.
abstract: BACKGROUND
  A fraction of right ventricular stroke volume (pulmonary artery systolic storage, [PASS]), which is stored in pulmonary arteries during systole and then discharged to the capillaries, determines the diastolic pulmonary capillary blood flow and hence the capillary blood volume participating in gas diffusion. Possibility that increases in pulmonary blood volume (PBV) increase PASS, leading to an improved distribution of ventilation-to-perfusion ratios (V/Q), was examined.
  
  
  RESULTS
  Included were 34 obese patients undergoing bariatric surgery. We used a nitrous oxide-airway-pneumotachographic method to measure PASS. The measurements were repeated before and after increasing PBV. In 20 patients, PBV was increased with infusion of crystalloids, which was guided by pulmonary capillary wedge pressure (PCWP). There was a good correlation between change in PASS and change in PBV (r(2) = 0.741, P < 0.0001). However, when the baseline PASS was high, changes in PASS were much less. In patients with a pulmonary artery diastolic-pulmonary capillary wedge pressure gradient ≥ 6 mmHg, the baseline PASS was correlated with pulmonary venous resistance (r(2) = 0.644, P = 0.017). In 14 patients, in whom PBV was increased with both changes in position and infusion of crystalloids, the physiologic dead space-to-tidal volume ratio (VD/VT) was measured as an index of the distribution of V/Q. There was a good negative correlation between PASS and VD/VT (r(2) = 0.697, P < 0.0001). However, at a high baseline PASS, increases in PBV decreased PASS (P = 0.0006) and increased VD/VT (P = 0.0018).
  
  
  CONCLUSIONS
  Changes in PBV change PASS and thereby the distribution of V/Q, depending on pulmonary venous resistance, which determines the baseline PASS.
authors.affiliation: Department of Anesthesiology and Pain Medicine, Inje University, College of Medicine, Haeundae Paik Hospital, Busan 612-030, Republic of Korea. Electronic address: charles6133@msn.com.
authors.forename: Charles
authors.initials: C
authors.lastname: Her
authors.forename: Yong Han
authors.initials: YH
authors.lastname: Kim
authors.forename: Sang Yoon
authors.initials: SY
authors.lastname: Jeon
mesh_terms: D000328:Adult; D050110:Bariatric Surgery; D001810:Blood Volume / Q000502:physiology*; D002196:Capillaries / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009767:Obesity, Morbid / Q000503:physiopathology* / Q000601:surgery; D011651:Pulmonary Artery / Q000502:physiology*; D011652:Pulmonary Circulation / Q000502:physiology*; D011667:Pulmonary Veins / Q000502:physiology; D011669:Pulmonary Wedge Pressure / Q000502:physiology; D011673:Pulsatile Flow / Q000502:physiology; D013318:Stroke Volume / Q000502:physiology; D013599:Systole / Q000502:physiology*; D014692:Ventilation-Perfusion Ratio / Q000502:physiology*; D055815:Young Adult
keywords: Artery; Blood volume; Obesity; Pulmonary; Ventilation