Chest
Original Research: Acute Ventilatory FailureProlonged Invasive Ventilation Following Acute Ventilatory Failure in COPD: Weaning Results, Survival, and the Role of Noninvasive Ventilation
Section snippets
Materials and Methods
Patients are referred to the PCP when weaning has failed at the referring ICU. Those accepted for transfer to the RSSC have recovered from the acute illness that precipitated their intubation. Most receive ventilation via tracheostomy and are hemodynamically stable without need of inotropic support.
General Care
Following transfer to our unit, sedating drugs are withdrawn at the first opportunity, and a normal diurnal routine is reinforced. Respiratory function is optimized with bronchodilators and corticosteroids as indicated. Respiratory tract secretions are actively managed with physiotherapy, tracheal suctioning, and the appropriate use of antibiotics. The management of coexisting medical problems is reviewed, and metabolic abnormalities are corrected. Tube enteral feeding is used to optimize
Weaning from IMV
On arrival, IMV is continued, using pressure support ventilation (PSV) with positive end-expiratory pressure aiming to normalize arterial blood gas (ABG) levels. Ventilatory weaning involves the introduction of unsupported spontaneous breathing (USB). Initial brief episodes (up to 30 min) are lengthened according to individual patient progress. This is guided by close clinical observation for respiratory distress, and the use of pulse oximetry, transcutaneous Pco2 (Ptco2) monitoring, and ABG
Laryngeal Function and Tracheostomy Management
Effective laryngeal function is a priority. Speaking is encouraged as soon as self-ventilation via a one-way tracheostomy speaking valve is possible without risk of aspiration. Swallowing safety is first assessed with the tracheostomy tube cuff inflated, using oropharyngeal administration of blue food dye followed by tracheal suctioning. If there is no aspiration, dyed fluids and food are tried. Once successful, these steps are repeated with the cuff deflated. Mild aspiration usually improves
Patient Selection
Patients with a discharge diagnosis of COPD were sought from a database of all patients entered into the PCP. The diagnosis was reviewed on the basis of patient history, referring hospital notes, clinical assessment, spirometry, and radiography. Coexisting pulmonary, neuromuscular, or chest wall disorders, or obstructive sleep apnea were exclusion criteria.
Data Collection
A retrospective case note review was performed, and the following data were extracted: age at PCP admission; sex; length of stay (LOS) at referring ICU; LOS in the RSSC; FEV1; FVC; ABG levels at intubation, at transfer to, and discharge from the PCP; APACHE (acute physiology and chronic health evaluation) II score at ICU admission; ventilation mode and inspired oxygen concentration at RSSC discharge; and discharge destination. The most recent ventilator settings were sought for patients
Outcomes
Weaning success was defined as complete withdrawal of IMV, with or without continuing requirement for nocturnal NIV. Hospital and long-term survival were also measured. Patients with a tracheostomy retained solely for suction were regarded as weaned. Failure to wean was defined as death during the weaning process, or discharge from the RSSC with a continuing requirement for IMV. Long-term survival was assessed using case notes, the hospital computerized patient administration system, and the
Statistical Analysis
Data were analyzed using statistical software (SPSS version 12.0 for Windows; SPSS; Chicago, IL). Long-term survival was assessed with Kaplan-Meier charts and life tables. Associations with survival were sought using Cox regression, with grouped data used when statistically significant but nonlinear relationships were found for continuous variables. Normally distributed data were compared using independent t tests, and nonparametric data were compared with the Mann-Whitney U test.
Results
We accepted 436 patients into the PCP between June 1992 and December 2003, 97 of whom had a discharge diagnosis of COPD. Thirty patients were excluded from the analysis due to coexisting pulmonary, chest-wall or neuromuscular disorders, or obstructive sleep apnea. Demographics, ICU, and weaning data of the remaining 67 patients (36 male) are presented in Table 1.
All 67 patients were receiving tracheostomy ventilation on arrival to the RSSC. Three patients died in the RSSC while receiving IMV,
Patient Characteristics and Correlation With Long-term Survival
Neither weaning success nor hospital survival were associated with age; sex; FEV1; FVC; APACHE II score on ICU admission; ABG levels at ICU or PCP admission; LOS in the ICU; or use of NIV during weaning. Long-term survival was inversely associated on univariate analysis with age and LOS in the ICU and the RSSC. Patients aged ≥ 70 years on entry to the PCP had a 2.7-fold hazard of dying subsequently, compared to those < 70 years old (95% confidence interval [CI], 1.5 to 4.9; p = 0.001). Patients
Discussion
Exacerbations of COPD requiring hospitalization are associated with substantial hospital and longer-term mortality.34678914 Those cases complicated by acute ventilatory failure frequently require IMV, and weaning can be difficult.121015 We report a 95.5% success rate for weaning COPD patients from IMV and 92.5% survival to hospital discharge. These subjects had recovered from the acute illness that precipitated their intubation, were hemodynamically stable, and received ventilation via
ACKNOWLEDGMENT
The authors thank the Intensive Care National Audit and Research Centre for their help in providing APACHE II data, and Fay Cafferty for statistical input.
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