The authors did not give an overall total number of studies. The number addressing each aspect of the review is given in the results section below.
There were no studies of arterial blood gas sampling. Three observational studies of chest roentgenography showed that a chest radiograph is a useful diagnostic test in emergency departments or hospitals. Spirometric testing (3 observational studies) was of limited usefulness at the time of presentation or during treatment.
There were 14 RCTs of bronchodilating agents, 6 placebo-controlled RCTs of corticosteroids and 11 placebo-controlled RCTs of antibiotics. Short-acting beta-agonists and anticholinergic inhaled bronchodilators have comparable effects on spirometry and a greater effect than all parenterally administered bronchodilators. A short course of systemic corticosteroids can improve spirometry and decrease the relapse rate. Antibiotics were beneficial, particularly in patients with more severe exacerbations.
No studies were cited to support the use of oxygen therapy, but there was a general acceptance of benefit. Four observational studies indicated that oxygen therapy may cause hypercarbia, but it is possible to identify the patients at risk.
Mucus clearance strategies (5 RCTs involving five different drugs) could possibly improve symptoms; there was no evidence to demonstrate that they can shorten the course of treatment.
Studies of physical and respiratory therapies (3 RCTs and 1 observational study) showed that mechanical percussion of the chest, as applied by physical/respiratory therapists, was ineffective and perhaps even detrimental.
Noninvasive positive-pressure ventilation (5 RCTs and 5 observational studies) was shown to be a beneficial support strategy. In selected hospitalised patients with respiratory failure it decreases the likelihood of requiring invasive mechanical ventilation and possibly improves survival time.