We retrospectively reviewed the medical records of AECOPD patients who underwent invasive mechanical ventilation at our hospital’s respiratory ICU from January 2020 to May 2020. Inclusion criteria were: > 18 years old, diagnosis of COPD with respiratory failure based on the GOLD (global initiative for chronic obstructive lung disease) criteria, endotracheal tube mechanical ventilation, and mechanical ventilation for > 48 h. Exclusion criteria were: central system diseases other than pulmonary encephalopathy, severe arrhythmia, cardiogenic shock, myocardial infarction, acute pulmonary embolism, pneumothorax, massive pleural effusion and lung malignant tumor, upper gastrointestinal perforation, obstruction, massive hemorrhage, recent digestive tract surgery, and tracheotomy.
This study was granted ethical approval by the ethics committee of Harrison International Peace Hospital. All participants gave written informed consent.
All patients were assessed according to the following readiness for weaning criteria . SIMV (synchronized intermittent mandatory ventilation) and PSV (pressure support ventilation) were used in the initial stage of invasive mechanical ventilation. Ventilator parameters were then gradually adjusted to the patient’s condition. Invasive mechanical ventilation was done > 48 h before weaning. The timing of invasive mechanical ventilation removal was determined by: full wakefulness (Glasgow coma scale [GCS] score of 15, normal blood pH (7.35–7.45); presence of cough reflex; presence of pulmonary infection control (PIC) window which was characterized by improved sputum volume, sputum character, sputum color, core temperature of < 38.0 °C, normal white blood cell count, shrinkage of lung infiltration shadow, serum procalcitonin (PCT) levels of < 0.25 ug/L ; stabilization of arterial blood partial carbon dioxide (PCO2) pressure within a fluctuation of ± 20%; oxygenation index (arterial oxygen partial pressure divided by inhaled oxygen concentration) > 150–200; rapid shallow breathing index (RSBI) < 105 breaths/min/L; tidal volume > 5 mL/kg; minute ventilation > 0.1 L/kg; inspiratory pressure of ventilator 8–12 cm H2O; positive end-expiratory pressure (PEEP) ≤ 5–8 cm H2O; and respiratory rate 12–18 times/min.
SBT was given for 60 min using a T-piece to connect the external end of tracheal intubation. Continuous normal saline atomization was given to avoid airway drying, followed by extubation according to Practical Guidelines for Mechanical Ventilation . In case of the following, SBT was immediately stopped and the patient placed on re-use of invasive mechanical ventilation: RSBI > 105 breaths/min/L, respiratory rate < 8 times/min or > 35 times/min, change of heart rate by > 20% or > 140 times/min and absence of new arrhythmia, tidal volume < 4 mL/kg, or oxygen saturation (SaO2) of < 0.90. RSBI is the ratio determined by the respiratory rate divided by the tidal volume in liters during an SBT. The respiratory rate of patients was monitored by the bedside ECG monitor. The tidal volume was monitored by the bedside portable pulmonary function instrument, with the blowing valve of the pulmonary function instrument connected with end of the T-piece.
Non-SBT patients who met weaning criteria were immediately extubated, and oxygen supplied by facemask. For all patients, blood gas analysis will be rechecked 1 h and 2 h after extubation, and not all patients were given noninvasive ventilatory (NIV) support within 2 h after extubation. The indications of NIV were: a) patient status: conscious, can remove airway secretions autonomously, shortness of breath (frequency > 25 times/min), auxiliary respiratory muscle participating in respiratory movement; b) blood gas index: pH ≤ 7.35 when breathing indoor air at sea level, arterial partial pressure of oxygen (PaO2) < 60 mmhg (1 mmhg = 0.133 kPa) with or without partial pressure of carbon dioxide (PaCO2) > 45 mmhg. The clinicians followed the same standardized operation process and extubation indications, and the extubation was operated by the same medical team, so it was considered that the bias introduced by process of weaning was marginal.
The following data at baseline were recorded: age, gender, BMI (body mass index), APACHE (acute physiology and chronic health evaluation) II score, comorbidity, pulmonary function classification, arterial blood gas analysis pH value, PCO2, heart rate, hemoglobin level, albumin levels, and body temperature. After extubation, the number of patients requiring reintubation (direct reintubation, reintubation after noninvasive ventilatory support) within 48 h, number of patients requiring noninvasive ventilatory support after extubation, and survival rate within 28 days of extubation were recorded.
Statistical analyses were done on SPSS 24.0. Kolmogorov–Smirnov normal test was used to analyze data distribution. Normal distribution data were presented as mean ± SD. Variables data between groups were compared using t-test. Attributes data between groups were analyzed using Chi-square test. P < 0.05 indicated statistically significant differences.