The significance of volume-adjusting the maximal midexpiratory flow in assessing the response to a bronchodilator drug.

Forced expiratory spirograms were obtained before and for six hours after 25 subjects ingested ephedrine and placebo in a double-blind crossover study. Significant changes in the forced vital capacity (FVC) and the forced expiratory volume in one second (FEV1.0) were noted on days when ephedrine was administrated, while the mean forced expiratory flow during the middle half of the FVC (FEF25-75%) failed to indicate significant bronchodilation. When FVC increases after therapy with a bronchodilator drug, one is no longer measuring flow during the same volume segment and driving pressure (static transpulmonary pressure [Pst]) as before administration of the bronchodilator drug. Volume-adjusting the FEF25-75% after therapy to the same volume and Pst over which flow is being measured in the tracings before bronchodilator therapy yielded highly significant increases in flow after administration of the bronchodilator drug.

Prolonged rate of decay of arterial PO2 following oxygen breathing in chronic airways obstruction.

Nine patients with moderate to severe chronic obstructive lung disease were grouped according to results of pulmonary function testing. After a short period of 100 percent oxygen breathing, it took on the average 20 minutes (range--18 to 24 minutes) for their partial pressure of arterial oxygen to return to baseline levels. These data suggest that, after discontinuing supplemental oxygen in patients with chronic airways obstruction, more than 25 minutes should elapse if a blood gas measurement is to reflect with certainty conditions during room air breathing.

Outpatient diagnosis and treatment of AIDS-related pulmonary infections.

A large number and variety of organisms can infect the lungs of persons with AIDS. An abnormal chest X-ray associated with pulmonary symptoms should trigger a vigorous search for an infectious agent. In many cases, if the patient is ambulatory, the workup can proceed on an outpatient basis. Pneumocystis carinii pneumonia is the most common infection and also one of the most readily treatable illnesses that these patients encounter. A careful and considered diagnostic approach is necessary to conserve the time and resources of both patients and healthcare providers.

Respiratory mechanics in normal hamsters.

Lung volumes and quasi-static deflation volume-pressure relationships were measured in male golden hamsters anesthetized with pentobarbital. Volume was measured with a pressure plethysmograph, and pleural pressure was estimated by the use of a water-filled esophageal catheter. Mean body weight +/- SE was 122.3 +/-3.0 g, mean lung weight was 0.74 +/- 0.2 g or about 0.6% of body weight. Mean lung volume at 25 cmH2O transpulmonary pressure (TLC25) was 7.2 +/- 0.14 ml, 9.78 +/- 0.17 ml/g lung weight or 5.92 +/- 0.06 ml/100 g body weight. Mean functional residual capacity was 2.4 +/- 0.06 ml or 33.3% of TLC25. Mean vital capacity was 5.2 +/- 0.13 ml. Mean quasi-static compliance of lung was 0.63 +/- 0.03 ml/cmH2O. Chord compliance of chest wall between lung volumes of 1 and 4 ml above RV was 3.39 +/- 0.53 ml/cmH2O. At FRC, the chest wall recoiled inward, so that pleural pressure was positive (1.4 +/- 0.13 cmH2O) and the lung was resisting further collapse. The slope of the lung's deflation volume-pressure curve changed at FRC, ERV was small (0.36 +/- 0.03 ml), and RV was determined by complete airway closure. Thus the mechanisms determining FRC are unusual and include an influence of airway closure.

Bacterial tracheitis with upper airway obstruction in a patient with the acquired immunodeficiency syndrome.

Bacterial tracheitis after an upper viral respiratory infection is a well-recognized entity in the pediatric literature. Bacterial tracheitis has only recently been reported in adults, and it is a potentially life-threatening illness. We report a case of bacterial tracheitis in a patient with AIDS.