Continuous positive airway pressure increases haemoglobin O2 saturation after acute but not prolonged altitude exposure.
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.
Agostoni
Piergiuseppe
P
Centro Cardiologico Monzino, IRCCS, Istituto di Cardiologia, Università di Milano, Via Parea 4, 20138 Milan, Italy. piergiuseppe.agostoni@ccfm.it
Caldara
Gianluca
G
Bussotti
Maurizio
M
Revera
Miriam
M
Valentini
Mariaconsuelo
M
Gregorini
Francesca
F
Faini
Andrea
A
Lombardi
Carolina
C
Bilo
Gregorz
G
Giuliano
Andrea
A
Veglia
Fabrizio
F
Savia
Giulio
G
Modesti
Pietro A
PA
Mancia
Giuseppe
G
Parati
Gianfranco
G
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
D006454:Hemoglobins; D010100:Oxygen