2018, Number 1
Med Crit 2018; 32 (1)
Determination of the mechanical power in patients in invasive mechanical ventilation in spontaneous mode
Gómez RJI, Monares ZE, González CBG, Camarena AG, Aguirre SJS, Franco GJ
PDF size: 225.97 Kb.
ABSTRACTObjective: To define which would be the mechanical power (using a mathematical model that can apply to possible causes for lung injury) used by a ventilator, in patients undergoing invasive mechanical ventilation in spontaneous PAV (proportional assist ventilation).
Material and methods: The mechanical and distention powers are calculated using the equations:
|1. Poder mecánico rs =|
2. Mechanical power rs = (0.098) . (FR . ΔV) . (Ppeak - ½ . ΔP)
3. PD = (0.098) . (PPL- PEEP) . Vt . RF
Sixty patients were selected, half of them with invasive mechanical ventilation PAV in spontaneous mode, estimating the plateau pressure (Ppl) though tidal volume value (Vt), distensibility (Crs), and the positive pressure at the end of a normal exhalation (PEEPt) given by the mechanical ventilator.
Results: Data from 60 patients undergoing invasive mechanical ventilation was included, 30 of them through spontaneous modality: proportional assist ventilation (PAV), from which 100% had a successful ventilator tube removal; 30 patients were paired as controls with controlled modalities, with age 65 years (SD ± 15), 63% were men, with the general parameters: mean respiratory frequency (RF) of 18 (SD ± 5.5) min-1, mean Vt of 0.46 (SD ± 0.1) Lts, mean Crc of 55 (SD ± 22) mL/cm H2O, PEEPt of 7.6 (SD ± 3.3) cm H2O, peak pressure (Ppico) 20.4 (SD ± 6.9) cm H2O, Ppl of 17.05 (SD ± 5.8) cm H2O. When comparing the mechanical power, all the results were inferior in patients with spontaneous modality versus patients undergoing controlled modality ventilation, determining the following values: 6.98 (SD ± 1.69) versus 18.49 (SD ± 8.20) J/min (p ‹ 0.001), 7.17 (SD ± 1.67) versus 20.92 (SD ± 9.05) J/min (p ‹ 0.001) and of 4.6 (SD ± 1.64) versus 12.33 (SD ± 7.04) J/min (p ‹ 0.001), in the equations 1, 2, and 3 respectively, with an average value for the patients undergoing spontaneous modality of 6.25 (SD ± 1.66) J/min.
Conclusions: The probability of determining a mean value for the mechanical power used in patients undergoing invasive mechanical ventilation on a PAV mode may allow to obtain a standard parameter to follow under the context of its estimated equivalence in physiological conditions, mainly for patients in whom lung protective measures are desired in order to obtain a positive progress and the eventual removal of the invasive ventilation.