title: PaO2 oscillations caused by cyclic alveolar recruitment can be monitored in pig buccal mucosa microcirculation.
abstract: BACKGROUND
  Cyclic alveolar recruitment and derecruitment play a role in the pathomechanism of acute lung injury and may lead to arterial partial pressure of oxygen (PaO(2) ) oscillations within the respiratory cycle. It remains unknown, however, if these PaO(2)  oscillations are transmitted to the microcirculation. The present study investigates if PaO(2)  oscillations can be detected in the pig buccal mucosa microcirculation.
  
  
  METHODS
  Respiratory failure was induced by surfactant depletion in seven pigs. PaO(2)  oscillations caused by cyclic recruitment and derecruitment were measured in the thoracic aorta by fast fluorescence quenching of oxygen technology. Haemoglobin oxygen saturation, haemoglobin amount and blood flow in the buccal mucosa microcirculation were determined by combined fast white light spectrometry and laser Doppler flowmetry additionally to systolic arterial pressure. Measurements were performed during baseline conditions and during cyclic recruitment and derecruitment.
  
  
  RESULTS
  Measurements remained stable during baseline. Respiratory-dependent oscillations occurred in the systemic circulation [PaO(2)  oscillations 92 (69-172) mmHg; systolic arterial pressure oscillations 33 (13-35) %] and were related to the respiratory rate (5.0 ± 0.2/min) as confirmed by Fourier analysis. Synchronised oscillations were detected to the pig buccal mucosa microcirculation [haemoglobin oxygen saturation oscillations 3.4 (2.7-4.9) %; haemoglobin amount oscillations 8.5 (2.3-13.3) %; blood flow oscillations 66 (18-87) %]. The delay between PaO(2) -\ and microcirculatory oxygen oscillations was 7.2 ± 2.8 s.
  
  
  CONCLUSIONS
  The present study suggests that PaO(2)  oscillations caused by cyclic recruitment and derecruitment were transmitted to the buccal mucosa microcirculation. This non-invasive approach of measuring oxygen waves as a surrogate parameter of cyclic recruitment and derecruitment could be used to monitor PaO(2)  oscillations at the bedside.
authors.affiliation: Department of Anaesthesiology, Medical Center of the Johannes Gutenberg-University, Währinger Gürtel 18-20, Vienna, Austria. ulrich.klein@meduniwien.ac.at
authors.forename: K U
authors.initials: KU
authors.lastname: Klein
authors.forename: E K
authors.initials: EK
authors.lastname: Hartmann
authors.forename: S
authors.initials: S
authors.lastname: Boehme
authors.forename: M
authors.initials: M
authors.lastname: Szczyrba
authors.forename: L
authors.initials: L
authors.lastname: Heylen
authors.forename: T
authors.initials: T
authors.lastname: Liu
authors.forename: M
authors.initials: M
authors.lastname: David
authors.forename: C
authors.initials: C
authors.lastname: Werner
authors.forename: K
authors.initials: K
authors.lastname: Markstaller
authors.forename: K
authors.initials: K
authors.lastname: Engelhard
mesh_terms: D000818:Animals; D001013:Aorta, Thoracic / Q000502:physiology; D062186:Arterial Pressure; D018893:Bronchoalveolar Lavage; D002610:Cheek / Q000098:blood supply*; D005583:Fourier Analysis; D006439:Hemodynamics / Q000502:physiology; D017078:Laser-Doppler Flowmetry; D008833:Microcirculation / Q000502:physiology; D008991:Monitoring, Physiologic; D010100:Oxygen / Q000097:blood*; D011650:Pulmonary Alveoli / Q000502:physiology*; D011659:Pulmonary Gas Exchange; D012039:Regional Blood Flow / Q000502:physiology; D012131:Respiratory Insufficiency / Q000503:physiopathology; D013552:Swine
chemical_list: D010100:Oxygen