Objective.

Describe the behavior of the alveolar-arterial oxygen gradient (Grad [Aa] O2), arterial- alveolar oxygen index (Ind [aA] O2) and Intrapulmonary shunt (Qs / Qt) in a patient group prior to ventilation -VMNI- in an intensive care unit -UCI-.

Methodology.

Retrospective cross-sectional study. We calculate the Grad[A-a] O2 by the equation: PAO2 = [[(pAtm-pH2O) xFiO2] - (pCO2 / RespQ)] - PaO2], for: Res-pQ = (0,8); (PAtm = 560mmHg for Bogotá, which is 2640 meters above sea level); PH 2 O = (47 mmHg); The (Ind [a-A] O2) and (Qs / Qt) with the formula: (Cco2-Cao2) / (Cco2-Cvo2). Scope: Tertiary Hospital. Patients: 16 ICU subjects using a non-probabilistic consecutive sample, who received NIMV in a 3-month measurement period. Variables of main interest: Diagnosis, age, blood gas analysis, the variables were: (Grad [A-a] O2), (Ind [a-A] O2) and (Qs / Qt).

Results.

The mean age of the study population was 59.6; of these, 56% (n = 9) were women. NIMV was used in 14% (n = 16) of patients with a total population of 116 over a three-month period. The gasometric values found were: (Ind [aA] O2) = (0.38mmHg ± 0.2mmHg), (Qs / Qt) = (25% ± 8.1%) and (Grad [Aa] O2), PaO2 42mmHg ± 15mmHg), PaO2 / FiO2 = (149 ± 44.2), SvO2 (n = 8) = (66.2% ±) 9.3%), PH = (7.38 ± 0.1), SaO 2 = (92% ± 2.8%) and PaO 2 (70 mmHg ± 15.4 mmHg).

Conclusions.

The gasometric values (Qs / Qt = 25 ± 8.1%), (Ind [aA] O2 = <0.38 ± 0.2 mmHg) and (Grad [Aa] O2 = 159 ± 64.1 MmHg), identified in this group of patients, can be taken into account prior to the onset of NIMV in subjects with similar characteristics at a height of 2,640 meters above sea level.

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