Comparison of tracheal aspirates and protected brush catheter specimens for identifying pathogenic bacteria in mechanically ventilated patients.

Bacterial respiratory infections are common in patients undergoing prolonged mechanical ventilation, and antibiotic selection often is based upon the results of smears and cultures of tracheal aspirates (TA). This study was designed to determine the reliability of gram stains, cultures and antibody-coating of bacteria in TA by comparing them with the results of quantitative cultures of specimens obtained by protected brush catheters (PBC) inserted into involved areas of lung parenchyma. Twenty-two patients on mechanical ventilation for at least 72 hours, with new radiographic infiltrates and fever, were studied. Tracheal aspiration was performed in the usual manner using sterile disposable kits. Immediately thereafter, patients underwent fiberoptic bronchoscopy, and PBC-specimens were obtained from the areas of new radiographic infiltrates. Tracheal aspirates were gram stained and cultured aerobically, and antibody coating of bacteria was determined by fluorescence microscopy. Quantitative culture of PBC specimens contained greater than or equal to 10(3) colony forming units per brush in 16 of the 22 patients; a smaller number of organisms was present in two additional patients. In TA from all 22 patients, gram stains revealed polymorphonuclear neutrophils and bacteria. Cultures of TA revealed potential pathogens in 20 patients, and in 15, multiple pathogens were present. The bacteria isolated from PBC also were present in 14 of the 16 patients with greater than or equal to 10(3) CFU in PBC cultures (88%). Antibody coating was present in TA from 12 patients, and antibody coating correlated poorly with cultures of PBC specimens.(ABSTRACT TRUNCATED AT 250 WORDS)

Unilateral absence of ventilation and perfusion associated with a bronchial mucous plug.

We have described a patient in whom loss of ventilation and perfusion of an entire lung resulted from mucous impaction of a major bronchus. Mucous plugging was associated with the combination of asthma and decreased cough effectiveness due to paraplegia. Removal of the obstruction by bronchial aspiration followed by vigorous pulmonary physical therapy resulted in return of both ventilation and perfusion to the lung and relief of dyspnea and hypoxemia.

Antibody coating and quantitative cultures of bacteria in sputum and bronchial brush specimens from patients with stable chronic bronchitis.

Antibody coating of bacterial isolates has been proposed as a method of identifying bacteria responsible for chronic lower respiratory infections. This study was designed to determine the specificity of antibody coating by examining bronchial secretions obtained from a group of patients with chronic bronchitis who had no clinical evidence of acute infection. Routine and quantitative bacterial cultures were performed at the same time. The bronchial brush specimens contained potentially pathogenic bacteria in all 18 patients examined, and 17 of these 18 specimens had antibody coating of bacteria. Quantitative cultures yielded greater than 10(4) colony forming units in only one patient and he subsequently developed a lower respiratory tract infection. We conclude that in patients with chronic bronchitis, the determination of antibody coating of bacterial isolates does not significantly increase the specificity of routine culture. Quantitative cultures of specimens obtained via the protected brush catheter are useful in identifying potential pathogens.

Effect of aminophylline on exercise performance in patients with irreversible airway obstruction.

Thirteen clinically stable male patients aged 63 +/- 3 years with irreversible airway disease were given aminophylline and placebo in a randomized crossover fashion on two consecutive days while receiving beta-agonists. During incremental exercise the maximal heart rate (139.0 +/- 22.1 vs 128.0 +/- 16.4 beats per minute) and minute ventilation (41.9 +/- 6.9 vs 38.1 +/- 8.2 L/min) were significantly higher and the arterial carbon dioxide pressure (34.6 +/- 5.0 vs 38.6 +/- 7.7 mm Hg) was significantly lower during aminophylline administration than during placebo administration. However, spirometric findings, maximal inspiratory pressures, maximal oxygen consumption, work rate, and arterial oxygen pressure were similar on both regimens. We concluded that the major effect of aminophylline is to increase ventilatory drive in patients with irreversible airway obstruction. Unless an objective change in spirometric data or exercise capacity can be documented, we believe that aminophylline therapy is not warranted in these patients.

Value of routine daily chest x-rays in the medical intensive care unit.

To ascertain the value of the daily routine chest x-ray in the medical ICU, we determined prospectively the number of unsuspected abnormalities observed on 507 consecutive chest films and the consequent management changes in 94 ICU patients. Primary diagnoses were classified as pulmonary, hemodynamically unstable cardiac, uncomplicated cardiac, or miscellaneous. Admission films and those taken after procedures or a change in clinical status were excluded. Ventilator status and the tubes and catheters visible on the films were also noted. After clinical evaluation, management plans were made by ICU physicians and then the chest x-ray was examined and unsuspected abnormalities and resulting management changes were noted. Of the 507 chest films, 76 (15%) revealed an unsuspected abnormality, 71 (93%) of which led to a management change. There were significantly (p less than .02) more unsuspected abnormalities and management changes in the pulmonary and unstable cardiac patients, independent of ventilator status. Patients with two or more catheters and/or tubes visible on the chest film also had significantly more management changes (51/312 vs. 11/150, p less than .05). We conclude that while routine chest films affect the management of pulmonary and unstable cardiac patients in the ICU, routine films rarely influence management of uncomplicated cardiac patients and those without heart or lung disease, and are not warranted in this group.

Endotracheal tube cuff residual volume and lateral wall pressure in a model trachea.

The authors constructed a D-shaped tracheal model with an elastic posterior wall, thus simulating normal tracheal anatomy more closely than previous models. The performance of 9-10 tracheal tube cuffs, of 2-3 different tube sizes (7.0-10.0 mm, ID), from six different manufacturers were tested in the model. Cuff residual volumes ranged from 1.78 to 27.35 ml. Cuff pressure and lateral wall pressures exerted by the cuff on the model were measured at the time a seal was achieved which just prevented leakage of water past the cuff. When a seal was achieved with a volume of air in the cuff less than cuff residual volume, wall pressure tended to be low (less than 35 torr) and cuff pressure closely approximated wall pressure. There was no relationship between cuff brands in the wall pressure required to effect a seal in the model. The authors conclude that intratracheal tubes should have cuffs with large residual volumes. This would permit some latitude in tube size selection while ensuring that a seal could be achieved before the cuff is inflated to its residual volume.