| Objective:“Hypercapnic encephalopathy ”(HE)is a heterogeneous and potentially reversible wide spectrum of neurological alterations(from cognitive defects,psychomotor agitation and confusion with asterixis to soporous status,delirium and coma)occurring in the presence of acute respiratory failure(ARF)with severe decompensated respiratory hypercapnic acidosis.Invasive mechanical ventilation is currently recommended as the gold-standard technique for the treatment of patients with an acute exacerbation of COPD(AECOPD)and HE.Mechanical ventilation supported basic minute ventilation,and caused Pa CO2 to recovery into stable level.Pa CO2 should not descend too much and induce respiratory alkalosis.Currently,there is no ways to monitor Pa CO2 downturn trend and mechanical ventilation strategy cannot control rate of decay.End-tidal carbon dioxide(PETCO2)monitoring refers to the noninvasive measurement of exhaled carbon dioxide and is most useful when applied directly to patient care.It is considered as a surrogate for the Pa CO2.There is strong correlation between Pa CO2 and PETCO2 in healthy adults.In this study,we will observe the correlation between Pa CO2 and PETCO2,monitor PETCO2 downswing in early used of mechanical ventilation and try to explore PETCO2-directed target strategy for ventilator settings.Methods:His prospective and observational study was performed between October 2015 and January 2017 in ICU.All patients with AECOPD and hypercapnic encephalopathy received invasive mechanical ventilation.1 Samples were immediately analyzed for Pa CO2 using a blood gas analyzer.The PETCO2 was measured using an end-tidal CO2 analyzer at the same time.Correlation between Pa CO2 and PETCO2 was analyzed.2 After HE patients were intubated and received mechanical ventilation,PETCO2 were monitoring continually.After proper calibration and an equilibration time of 20 minutes with stable hemodynamic and respiratory variables(fluctuating margin≤±2mm Hg),PETCO2 were determined and the highest reading was recorded per 2 minutes.3 After mechanical ventilation therapy for 24-36 h,patients were in controlled ventilation and PETCO2 was stably.Change the breathing frequency and adjust minute ventilation from initial value to 4L/min,then minute ventilation rise to 10L/min and was recovered to initial breathing frequency.Correlation between minute ventilation and PETCO2 was analyzed.Results:1 A total of 70 arterial blood gases were obtained from the 24 patients.There is a positive correlation between Pa CO2 and ETCO2 undifferentiated modes(r=0.759,Y= 14.376+ 0.799x).A positive correlation was found in each of the SIMV and SPONT modes,indicating statistical significance but A/C mode(r=-0.016,P=0.980).There is a significant correlation whether Pa O2/Fi O2<200mm Hg(r=0.765,P<0.001)or ≥200 mm Hg(r=0.759,P<0.001).2 Nine patients received PETCO2 monitor continuously at early stage of mechanical ventilation.PETCO2 level fell rapidly and reached stable state in20-60 minutes.The higher of initial PETCO2 value,the more time to stable state,but lower than one hour.Down trend of PETCO2 was calculated by the mechanical ventilation time of fitting curve(Y=PETCO2base+b1x+b2x2).3 A total of 58 arterial blood gases were obtained from the 12 patients.PETCO2 become stable after 1-2 minutes in each adjusted respiratory rate.There is a significant negative correlation between minute ventilation and PETCO2(r=-0.560,Y= 66.82-3.06 x).Conclusions:There is a significant correlation between Pa CO2 and PETCO2.PETCO2 could prediction Pa CO2 downtrend at early stage of mechanical ventilation and provide a basis for preventing excessive ventilation and adjust ventilatorsetting. |
PDF Full Text Request