title: Continuous positive airway pressure increases haemoglobin O2 saturation after acute but not prolonged altitude exposure.
abstract: OBJECTIVE
  It is unknown whether subclinical high-altitude pulmonary oedema reduces spontaneously after prolonged altitude exposure. Continuous positive airway pressure (CPAP) removes extravascular lung fluids and improves haemoglobin oxygen saturation in acute cardiogenic oedema. We evaluated the presence of pulmonary extravascular fluid increase by assessing CPAP effects on haemoglobin oxygen saturation under acute and prolonged altitude exposure.
  
  
  RESULTS
  We applied 7 cm H(2)O CPAP for 30 min to healthy individuals after acute (Capanna Margherita, CM, 4559 m, 2 days permanence, and <36 h hike) and prolonged altitude exposure (Mount Everest South Base Camp, MEBC, 5350 m, 10 days permanence, and 9 days hike). At CM, CPAP reduced heart rate and systolic pulmonary artery pressure while haemoglobin oxygen saturation increased from 80% (median), 78-81 (first to third quartiles), to 91%, 84-97 (P < 0.001). After 10 days at MEBC, haemoglobin oxygen saturation spontaneously increased from 77% (74-82) to 86% (82-89) (P < 0.001) while heart rate (from 79, 64-92, to 70, 54-81; P < 0.001) and respiratory rate (from 15, 13-17, to 13, 13-15; P < 0.001) decreased. Under such conditions, these parameters were not influenced by CPAP.
  
  
  CONCLUSIONS
  After ascent excessive lung fluids accumulate affecting haemoglobin oxygen saturation and, in these circumstances, CPAP is effective. Acclimatization implies spontaneous haemoglobin oxygen saturation increase and, after prolonged altitude exposure, CPAP is not associated with HbO(2)-sat increase suggesting a reduction in alveolar fluids.
authors.affiliation: Centro Cardiologico Monzino, IRCCS, Istituto di Cardiologia, Università di Milano, Via Parea 4, 20138 Milan, Italy. piergiuseppe.agostoni@ccfm.it
authors.forename: Piergiuseppe
authors.initials: P
authors.lastname: Agostoni
authors.forename: Gianluca
authors.initials: G
authors.lastname: Caldara
authors.forename: Maurizio
authors.initials: M
authors.lastname: Bussotti
authors.forename: Miriam
authors.initials: M
authors.lastname: Revera
authors.forename: Mariaconsuelo
authors.initials: M
authors.lastname: Valentini
authors.forename: Francesca
authors.initials: F
authors.lastname: Gregorini
authors.forename: Andrea
authors.initials: A
authors.lastname: Faini
authors.forename: Carolina
authors.initials: C
authors.lastname: Lombardi
authors.forename: Gregorz
authors.initials: G
authors.lastname: Bilo
authors.forename: Andrea
authors.initials: A
authors.lastname: Giuliano
authors.forename: Fabrizio
authors.initials: F
authors.lastname: Veglia
authors.forename: Giulio
authors.initials: G
authors.lastname: Savia
authors.forename: Pietro A
authors.initials: PA
authors.lastname: Modesti
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Mancia
authors.forename: Gianfranco
authors.initials: G
authors.lastname: Parati
mesh_terms: D000064:Acclimatization / Q000502:physiology; D000328:Adult; D000531:Altitude; D001794:Blood Pressure / Q000502:physiology; D045422:Continuous Positive Airway Pressure; D005260:Female; D006339:Heart Rate / Q000502:physiology; D006454:Hemoglobins / Q000737:chemistry*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000097:blood*; D013997:Time Factors
chemical_list: D006454:Hemoglobins; D010100:Oxygen