Patients: DISCUSSION

The present study demonstrates that clinical fea­tures apparent after seven days of mechanical venti­lation for ARDS can determine the likelihood that successful extubation will occur within the following seven days. Presence on day 7 of а РаО2/РaО2 ratio >0.40, a PEEP requirement below 10 cm H20, an improving chest radiograph and less than 50 percent of lung field involvement with alveolar infiltrates was associated with early recovery from respiratory failure in group 1 patients. Conversely, absence of these features after seven days of management for ARDS identified group 2 patients who subsequently required long-term mechanical ventilation. Furthermore, group 2 patients were likely to undergo eventual tracheot­omy. The nature of the underlying clinical predispo­sition to ARDS, the severity of initial respiratory failure or the degree of improvement in thoracic compliance after seven days of ARDS were not pre­dictive of intubation duration.

The reviewed medical records did not clearly indi­cate whether the physicians’ decisions to extubate patients were based on specific weaning criteria that incorporated spontaneous ventilatory parameters. Nevertheless, no group 1 patient required reintubation after undergoing extubation on or before day 14 of ARDS; this finding demonstrates the accuracy of categorizing these patients into group 1. Furthermore, no group 2 patient underwent attempted extubation during the first 28 days of ARDS; this observation suggests that no patient was categorized into group 2 because he or she remained on mechanical ventilation needlessly beyond day 14. Rather, the severity of respiratory failure and the rapidity of resolution of ARDS appeared to be the major factors determining timing of extubation.
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The observations of this study objectify our clinical impression that patients who are successfully extu- bated within 14 days of ARDS begin to experience recovery of lung function within the first several days of respiratory failure. Indeed, the differences in РаО2/РaО2 and PEEP requirements first became significantly different between groups by day 2 and day 5 of ARDS, respectively. Either progressive de­terioration or lack of significant improvement requir­ing ongoing aggressive respiratory support by the seventh day of pulmonary dysfunction identify patients with more severe ARDS. Such patients usually do not improve rapidly within the following few days to allow early extubation. Recognition of these predictive clin­ical features after the first week of mechanical venti­lation allows timely patient care planning, such as the decision to perform a tracheotomy.

The proper timing of tracheotomy in patients with respiratory failure undergoing mechanical ventilation is controversial. Proponents of either “early” or “late” tracheotomy focus on the relative risks of prolonged translaryngeal intubation as opposed to surgical airway cannulation. Both procedures, how­ever, have inherent complications. Tracheotomy pres­ents surgical risks, such as stomal infection and hemorrhage, and long-term hazards, such as tracheal stenosis and tracheoinnominate fistulae. Recent studies, however, suggest that perioperative compli­cations occur in only 2 to 6 percent of patients when tracheotomy is performed by experienced surgeons.In comparison, prolonged ET intubation complicates nursing care, promotes patient discomfort, induces sinus infection during nasal cannulation, and risks laryngotracheal stenosis, which is less readily cor­rectable by surgery than tracheal injury from trache­otomy. The incidence of long-term airway injury from prolonged ET intubation is similar to that re­ported from tracheotomy in recent studies.