Design and patients
Ninety-four AECOPD patients admitted into the intensive care unit (ICU) of our hospital from June 2008 to March 2012 were included, all of whom in accordance with the criteria of COPD guideline constituted by Chinese Society of Respiratory Diseases in 2007 and the diagnosis standard of pulmonary encephalopathy[2, 3]. They were divided into the control group (BMI<21) and the study group (BMI>21) in accordance with the criteria of COPD guideline constituted by American and European Society of Respiratory Diseases in 2004, BMI<21 was underweight and should be treated by nutritional support.
The study group consist of 23 males and 15 females aged from 41 to 85 years old (average of 64.50±4.75 years) and the course of their diseases are from 3 months to 22.23 years (average of 62.34±3.50 months), among whom there are 6 patients with type III and 32 patients with type IV COPD. The control group consist of 32 males and 24 females aged from 42 to 86 years old (average of 63.70±3.90 years) and the course of their diseases are from 4 months to 21.70 years (average of 63.18±4.22 months), among whom there are 12 patients with type III and 44 patients with type IV COPD. There is no significant difference between these two groups in age, gender, course of diseases, type of COPD, the score of APACHE II, result of blood gas analysis (P>0.05).
These two groups were treated by similar symptomatic therapies such as antibacterial, antispasmodic, relieving asthma, antitussive, expectorant, correction of electrolyte imbalance and acid-base balance disorders, strengthen nutritional support, etc. Patients were ventilated using assistance controlled mechanical ventilation (ACMV) during the initial mechanical ventilation, and switched to synchronous intermittent mechanical ventilation (SIMV) and pressure support ventilation (PSV) and positive expiratory end pressure (PEEP) with the improvement of patients’ condition. Mode and parameters of mechanical ventilation were adjusted according to patients’ condition. Patients were ventilated using SIMV and PSV and PEEP, and switched to PSV and PEEP after the PIC window appeared. The level of PSV was decreased gradually to 5-8cmH2O with the improvement of patients’ condition; at least 12 hours later, exudation was conducted and followed by non-invasive mechanical ventilation. The non-invasive mechanical ventilation that we used were bi-level positive airway pressure-spontaneous and timing mode (BiPAP-S/T); the level of inspiration positive airway pressure (IPAP) was 4-7cmH2O (1cmH2O = 0.0198KPa), and then weaning from mechanical ventilation after spontaneous breathe smoothly, instead of nasal breathing. These two groups weighed every day and kept the balance of body fluid. The treatment of the study group was the same as that of the control group until BMI >21, then weaning from mechanical ventilation.
The following indices were recorded at different times including before mechanical ventilation such as BMI, variation of blood gas analysis, invasive mechanical ventilation time, non-invasive mechanical ventilation time, total mechanical ventilation time, VAP occurred rate, re-intubation rate, hospital mortality rate in 28 days.
All parameters were expressed as the mean ±standard deviation (SD), with the use of SPSS13.0 software. All indices were analyzed by independent-sample t test and x2 test between the two groups, and by paired-sample t test between different times for each group. A P value less than 0.05 was considered statistically significant.