Independent control of mucosal and total airway blood flow during hypoxemia.

In the larger airways, the blood circulation forms a subepithelial (mucosal) and outer (peribronchial) microvascular network. This raises the possibility that blood flow in these two networks is regulated independently. We used hypoxemia as a stimulus to induce changes in tracheal mucosal blood flow normalized for systemic arterial pressure (Qtr n) measured with an inert soluble gas technique and total bronchial blood flow (Qbr) and normalized Qbr (Qbrn) measured with an electromagnetic flow probe in anesthetized sheep. Fifteen minutes of hypoxemia [PO2 40 +/- 7 (SD) Torr] decreased mean Qtr n from 1.1 +/- 0.4 to 0.8 +/- 0.4 ml.min-1.mmHg-1.10(2) (-27%; P less than 0.05; n = 7) and increased mean Qbr n from 12.1 +/- 3.2 to 17.1 +/- 5.4 ml.min-1.mmHg-1.10(2) (+41%; P less than 0.05; n = 6). The rise in Qbr correlated with cardiac output (r = 0.68; P less than 0.05). Phentolamine pretreatment (0.1 mg/kg iv) blunted the hypoxemia-related decrease of mean Qtr n (-8%; P = NS). Tyramine (2.5 mg) applied locally to the trachea decreased mean Qtr n significantly after 30 and 45 min by 31 and 19%, respectively (P less than 0.05). 6-Hydroxydopamine (0.2 mg 4 times for 1 h locally applied) prevented the hypoxemia-induced as well as local tyramine-induced decrease in mean Qtr n (0 and 0%).(ABSTRACT TRUNCATED AT 250 WORDS)

Tracheal mucosal blood flow responses to autonomic agonists.

In lightly anesthetized adult sheep, we determined tracheal mucosal blood flow (Qtr) by measuring the steady-state uptake of dimethyl ether from a tracheal chamber created by an endotracheal tube provided with two cuffs. Qtr normalized for carotid arterial pressure [Qtr(n)] was determined before and after the exposure of the tracheal mucosa to aerosolized phenylephrine (0.25-2.0 mg), isoproterenol (0.05-0.8 mg), and methacholine (2.5-20 mg). The same doses of methacholine were also administered during the intravenous infusion of vasopressin. The measurements were repeated after intravenous pretreatment with the respective antagonists phentolamine, propranolol, and atropine. Mean +/- SE base-line Qtr(n) was 1.2 +/- 0.1 ml.min-1.mmHg-1.10(2). The autonomic antagonists had no effect on mean Qtr(n). Phenylephrine produced a dose-dependent decrease in mean Qtr(n) (-70% at the highest dose), which was blunted by phentolamine, and isoproterenol produced a dose-dependent increase in mean Qtr(n) (40% at the highest dose), which was blocked by propranolol. Methacholine failed to alter mean Qtr(n) even when Qtr was first decreased by vasopressin. We conclude that in lightly anesthetized adult sheep 1) base-line Qtr(n) is not under adrenergic or cholinergic control, 2) a locally administered alpha-adrenergic agonist decreases and beta-adrenergic agonist increases Qtr(n) via specific receptor activation, and 3) a locally administered cholinergic muscarinic agonist has no effect on Qtr(n).

Value of repeat fiberoptic bronchoscopies and significance of nondiagnostic bronchoscopic results in patients with the acquired immunodeficiency syndrome.

Out of 286 patients with the acquired immunodeficiency syndrome (AIDS) who had fiberoptic bronchoscopies performed for the diagnosis of pulmonary disease, 21 (7.3%) patients (Group I) had repeat procedures after 1 to 30 days (mean, 14.8 days) because of persistent pulmonary infiltrates despite therapy, and 46 (15.9%) patients (Group II) had repeat procedures after 2 to 32 months (mean, 7.5 months) because of recurrent pulmonary infiltrates after initial clinical and radiographic improvement. Pneumocystis carinii pneumonia was the most common diagnosis in both groups on initial evaluation, being found in 55% of the patients. Repeat bronchoscopy yielded a new treatable diagnosis in 1 (5%) of 21 patients in Group I and in 27 (59%) of 46 patients in group II. Sixty-two percent of patients in Group I died within 1 month. It appears that in patients with AIDS who have persistent or worsening pulmonary infiltrates despite therapy, repeat bronchoscopy after a short interval (i.e., less than 1 month) is unlikely to have therapeutic implications. In contrast, those patients whose pulmonary involvement resolves initially may benefit from an aggressive diagnostic approach if new pulmonary infiltrates appear. In both groups, nondiagnostic bronchoscopies were common (29% overall). The most commonly missed bronchoscopic diagnoses (proved by open lung biopsy) were cytomegalovirus pneumonia and Kaposi's sarcoma, and neither had much therapeutic implication. Further, 12 patients in Group II with nondiagnostic bronchoscopies improved both radiographically and clinically even though no treatment was given.

Evaluation of patients with the acquired immunodeficiency syndrome (AIDS) by fiberoptic bronchoscopy.

Hospital records were reviewed on 78 consecutive patients (33 homosexuals, 37 Haitians and 8 IV drug abusers) who had AIDS and who underwent fiberoptic bronchoscopy over a two year period. Pneumocystis carinii pneumonia (PCP) was the most common bronchoscopic finding (53.8% of patients) followed by tuberculosis (14.1%), cytomegalovirus infection (12.8%) and atypical mycobacteriosis (3.8%). In 15.4% of patients multiple organisms were found. Twenty-seven percent of patients had non-diagnostic bronchoscopies. In 8 patients with non-diagnostic bronchoscopies, open-lung biopsy or autopsy revealed PCP (2 patients), Kaposi's sarcoma (3 patients) and non-specific lymphocytic-plasmacytic infiltrates (3 patients). Histologic studies of transbronchial biopsy specimens were more sensitive for the diagnosis of PCP than touch imprints. PCP was diagnosed in 15 patients who had received trimethoprim-sulfamethoxazole for up to 4 days. Mean duration of respiratory symptoms prior to bronchoscopy was 4.2 weeks in patients with PCP and was not significantly different in patients with other bronchoscopic diagnoses. Historical, laboratory and chest radiographic parameters were not helpful in establishing a diagnosis or assessing prognosis in these AIDS patients with pulmonary infiltrates. Fiberoptic bronchoscopy with transbronchial biopsy is safe (only one of the patients had a self limited hemorrhagic episode) and sensitive for the diagnosis of pulmonary infiltrates in patients with AIDS.