Abstract & Commentary
Mechanical Insufflation-Exsufflation and Prevention of Post-Extubation Respiratory Failure
By David J. Pierson, MD, Editor, Professor Emeritus, Pulmonary and Critical Care Medicine, University of Washington, Seattle, is Editor for Critical Care Alert.
Synopsis: When enhanced secretion clearance via mechanical insufflation-exsufflation was added to a post-extubation regimen including noninvasive ventilation as needed in patients recovering from acute respiratory failure, significantly fewer of them developed recurrent respiratory failure and required reintubation.
Source: Gonçalves MR, et al. Effects of mechanical insufflation-exsufflation in preventing respiratory failure after extubation: A randomized controlled trial. Crit Care 2012;16:R48. [Epub ahead of print.]
This study from Portugal addresses an important gap in managing patients who have been extubated after an episode of acute respiratory failure — facilitating the clearance of airway secretions to avoid the necessity of reintubation. Gonçalves et al evaluated the clinical efficacy of mechanical insufflation-exsufflation (MIE) via the CoughAssist (Philips Respironics, Carlsbad, CA) when added to a post-extubation regimen for patients recovering from acute respiratory failure. Once they met standardized criteria for weaning, patients were randomized prior to extubation either to management via a standardized protocol including chest physical therapy, bronchodilators, and noninvasive ventilation (NIV) as needed, or to management by the same protocol but with the addition of nine MIE treatments at specified intervals prior to extubation and during the first 48 hours thereafter.
Before extubation, patients in the MIE group received three 8-cycle sessions of insufflation-exsufflation. MIE consisted of applying positive pressure at +40 cm H2O to the patient's endotracheal tube for 3 seconds, followed immediately by negative pressure at -40 cm H2O for 2 seconds, with manual abdominal thrusts applied during the expiratory phase, and 3-second pauses between cycles. After these three treatments, the patients were extubated. They then received six additional treatments (same settings and procedure, using an oronasal mask) over the next 48 hours. MIE was stopped at that point, and patients were followed for the remainder of their hospital stays. Patients in both groups received NIV following extubation if they met the authors' prespecified criteria; standardized criteria were used to assess patients for recurrent respiratory failure and to reintubate them when necessary.
Seventy-five patients completed the study: 40 in the standard-care group and 35 in the MIE group. They were similar in age (mean 62 years), sex, illness severity, and duration of mechanical ventilation. More than half of them had hypoxemic respiratory failure, and only 20% had chronic pulmonary disease. None died during the 48-hour post-extubation period. NIV was used in 25 (50%) of the standard-care patients and in 14 (40%) of the MIE patients. Reintubation was required in 19 (48%) and 6 (17%) of the patients in the two groups, respectively (P < 0.05), with the most common reason for reintubation being "secretion encumbrance with severe hypoxemia." NIV failed more often in the standard-care group: 13 (33%) vs 2 (6%), P < 0.05, with all patients who failed NIV being reintubated. Patients in the MIE group had significantly shorter durations of invasive mechanical ventilation and ICU length of stay (the latter, by 6 days; P < 0.05). The authors conclude that secretion management using MIE may be effective in preventing reintubation in patients who develop acute respiratory failure in the first 48 hours following extubation.
Commentary
Acute respiratory failure requiring reintubation within 48 to 72 hours after extubation is a common and serious problem in the ICU. Numerous studies have shown that it is associated with worse survival, prolonged ventilation time and ICU stay, and an increased incidence of pneumonia and other complications. Failed extubation may occur because the original cause for respiratory failure has not resolved to the point where the patient could maintain spontaneous ventilation, or because of some new problem such as pneumonia or acute pulmonary edema. It also may be precipitated by laryngeal edema or other upper airway obstruction, or more commonly by the inability to maintain airway patency in the face of decreased mental status from over-sedation or some other cause. In the presence of these things, it is hard to avoid reintubation and the reinstitution of invasive mechanical ventilation.
However, in other common circumstances it may be possible to abort or prevent the development of post-extubation respiratory failure without reintubating the patient — and thus avoiding its associated increases in morbidity and mortality. These settings include the inability to maintain alveolar ventilation because the work of breathing exceeds the patient's capability, failure of adequate lung inflation to prevent atelectasis, and the inability to adequately clear airway secretions. The first two of these processes (in practical terms, respiratory muscle fatigue and progressive atelectasis) can often be managed with NIV, and several studies have shown that this modality applied early and judiciously reduces mortality, prevents many instances of reintubation, and shortens ICU stays. Until now, however, the third problem — insufficient clearance of airway secretions — has been the Achilles heel of post-extubation management. The present study shows that MIE, applied in the right patients with or without concomitant NIV, can also reduce the need for reintubation and shorten ICU stays.
Although it is a mainstay of current management of patients with cervical spinal cord injury and chronic neuromuscular disease,1,2 MIE is less well known outside the specialized wards that deal with those conditions and may be unfamiliar to ICU clinicians. Originally introduced in the 1950s for managing secretions in patients with polio, the forerunners of today's MIE devices saw considerable use in institutions caring for such patients. However, MIE fell out of favor with the emergence of volume-targeted positive-pressure ventilation and other aspects of intensive respiratory care after the 1960s, and it was only rediscovered by rehabilitation units and others caring for chronic neuromuscular patients about 20 years ago.
Currently, although other commercial devices are sold in Europe, only the Philips Respironics CoughAssist Mechanical Insufflator-Exsufflator is available in this country.1 About the size of a home mechanical ventilator, it is used to provide a large positive-pressure inspiration followed immediately by a negative-pressure, facilitated exhalation. It thus mimics in reverse a normal cough. Both inspiratory and expiratory times and pressures can be adjusted separately, and the device must be placed on and off the patient each time the maneuver is performed. It is thus an adjunct to, but not a replacement for, NIV. Like with a spontaneous cough, MIE is most effective when glottic closure is achieved briefly at the end of inspiration and before expiration. Abdominal compression, as performed with "quad coughing" in tetraplegic patients, is often performed simultaneously to increase expiratory flow and facilitate the expulsion of airway secretions. Originally thought applicable only to patients without an artificial airway who had intact glottic function, MIE is now becoming more widely used in patients with artificial airways.3
Nearly all the literature on MIE has dealt with patients with neuromuscular disease. A recent brief review cited 23 studies in this area, 21 of them in the previous 10 years.3 However, the study of Gonçalves et al appears to be the first randomized controlled trial of MIE in a general ICU population. Because the other available means for managing airway secretions in non-intubated patients are limited and often unsatisfactory, it is likely that we will be seeing a lot more of this technique in the future. As with NIV, successful MIE has a definite learning curve, although it is generally easier to learn and to carry out than NIV in an acutely ill patient. Gonçalves and colleagues point out, however, that their study was performed in a center with special expertise in MIE, and that this may affect the generalizability of their findings.
Based on this study, on the available literature, and on experience with MIE at my institution both on the rehabilitation unit and in the ICUs, Table 1 provides one way to view the potential usefulness of MIE following extubation in patients recovering from acute respiratory failure.
Table 1. Considerations in the Use of Noninvasive Ventilation and Mechanical Insufflation-Exsufflation following Extubation in Patients with Acute Respiratory Failure NIV preferable
MIE preferable, either instead of or in addition to NIV
MIE less likely to be successful
|
Special mention should be made of chronic obstructive pulmonary disease (COPD) with respect to the potential use of MIE. Although patients with severe COPD have increased airway secretions and trouble clearing them, their problem is typically not in generating a forceful cough but in the expiratory airflow limitation that characterizes their disease. It would be interesting to study the effects of MIE in severe exacerbations of COPD, but this maneuver would appear unlikely to be helpful in that setting because of the physiology involved.
References
- Homnick DN. Mechanical insufflation-exsufflation for airway mucus clearance. Respir Care 2007;52:1296-1305.
- Simonds AK. Recent advances in respiratory care for neuromuscular disease. Chest 2006;130:1879-1886.
- Toussaint M. The use of mechanical insufflation-exsufflation via artificial airways. Respir Care 2011;56:1217-1219.
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