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2011, Number 3

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Med Crit 2011; 25 (3)

Evaluación del espacio muerto ajustado al volumen corriente en pacientes con ventilación mecánica

Magaña MC, Salinas MC, Santiago TJ, Olvera GC, Aguirre SJ, Franco GJ

Language: Spanish
References: 14
Page: 131-141
PDF size: 400.45 Kb.


ABSTRACT

Introduction: The accurate measurement of physiological dead space to tidal volume ratio (Vd/Vt) is usually omitted in the ICU as exact values need indirect calorimetry to be obtained. Frankelfield modified the original Bohr formula (Vd/Vt = PaCO2 – CO2 et/PaCO2) by including age and Rate Respiratory (RR): Vd/Vt = 0.32 + 0.0106 (PaCO2 – CO2et) + 0.003 (RR) + 0.0015 (age).
Objective: To determine Vd/Vt usefulness in patients under Mechanical ventilation (MV).
Methods: Prospective observational study of all patients under MV admitted from November 2009 to July 2010. Demographics were obtained as well as respiratory parameters. RR, minute, static compliance, tidal volumen (Vt); Vd/Vt were calculated and correlated with variables obtained. Sensitivity and specificity was calculated and Vd/Vt cutoff points were obtained.
Results: 48 patients were included, 16 (42%) female; mean age 53 ± 22; APACHE II score 8 ± 5. Mean Vd/Vt value: 0.52 ± 0.06. Only 10 (20%) were reintubated and had a mean Vd/Vt of 0.50 ± 0.05 vs 0.59 ± 0.53 of successfully extubated ones (p = 0.0001) Best Vd/Vt cutoff value was ≤ 0.55 with 80% sensitivity, 87% specificity, positive predictive value of 62% and negative of 94%.
Conclusions: Patients with Vd/Vt ≤ 0.55 are successfully extubated.


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