Comparison of spontaneous and positive-pressure breathing in supine normal subjects

Distribution of ventilation (V) and perfusion (Q) was studied with 133Xe in eight supine, normal subjects comparing spontaneous breathing (SB) and intermittent positive-pressure breathing (IPPB). Tidal volume, inspiratory flow, and breathing frequency measured during SB were closely matched during automatically triggered IPPB. V and Q in the lung bases (adjacent to the diaphragm) were decreased relative to other regions during SB and further diminished by IPPB at similar volumes. During IPPB, basilar V and Q improved when tidal volume was increased; however; spontaneous hyperinflation resulted in significantly higher basilar V and Q than large tidal volumes delivered by IPPB. Thus, changes in lung volumes and gas exchange in the supine posture are attributable to impaired V and Q in the bases but not in dependent (posterior) regions. IPPB further reduces basilar V and Q, possibly due to loss of interdependence resulting from diminished respiratory muscle contraction. These findings may explain atelectasis during prolonged IPPB in supine patients. Although large tidal volumes improve basilar V during IPPB, spontaneous deep breaths are more effective and may prevent atelectasis better than IPPB at similar tidal volumes.

Determinants of lung bacterial clearance in mice after acute hypoxia

Net lung bacterial clearance in normal mice is determined by the balance of in vivo bacterial multiplication on the one hand, and the defense mechanisms of mucociliary clearance and phagocytosis and killing by the oxygen-dependent alveolar macrophage on the other. The bactericidal function of the macrophage is the major component of the defense mechanism. The effect of acute hypoxia on the defense mechanism was studied in mice exposed to aerosols of Staphylococcus aureus, Escherichia coli, Klebsiella pneumoniae, and Streptococcus pneumoniae. Physical clearance was not impaired by acute hypoxia, and bacterial replication was not stimulated by the low oxygen atmosphere. Clearance of Staphylococcus aureus, Klebsiella pneumoniae, and Escherichia coli was impaired during acute hypoxia due to decreased phagocytosis or killing by the alveolar macrophage. The important human pathogen Streptococcus pneumoniae was cleared normally in the presence of acute hypoxia. This observation suggests that an oxygen-independent clearance mechanism is important in lung defense against the pneumococcus. This may be a separate mechanism within the alveolar macrophage or a system as yet unidentified.

Pulmonary complications of general surgery

1. Patients should be divided preoperatively into low- or high-risk categories, depending on their probability of developing postoperative pulmonary complications. The evaluation should include spirometry as well as an assessment of the previously defined risk factors. 2. Patients in a low-risk category need only instruction in deep breathing pre- and postoperatively. Routine use of supplemented oxygen postoperatively is reasonable until it can be demonstrated whether such is necessary. 3. High-risk patients should be as free as possible of respiratory secretions at the time of surgery. A regimen for this purpose includes cessation of smoking, and administration of inhaled bronchodilators followed by chest percussion and postural drainage. 4. High-risk patients should be carefully instructed in deep breathing and coughing preoperatively. A mechanical device such as an incentive spirometer may be beneficial in this regard. If it is not possible to achieve spontaneous deep breathing, an attempt to accomplish this by IPPB may be undertaken. The tidal volume desired should be ordered. If IPPB does not result in large tidal volumes, it should be discontinued. 5. The deep breathing procedure found to be most successful preoperativelly should be continued postoperatively. 6. The patient should be as mobile as possible while in bed and ambulated as soon as is feasible. 7. Patients with preoperative expiratory flows of less than 20% of predicted values or with chronic hypercapnia should be carefully observed for postoperative ventilatory failure.

Fibronectin is not detectable on the intact buccal epithelial surface of normal rats or humans

Fibronectin (FN) has been postulated to prevent gram-negative bacillary (GNB) colonization of the oropharynx by covering epithelial cell GNB receptors. We investigated the distribution of FN along the luminal surface of oropharyngeal epithelium in animals and humans. Examination of buccal epithelial biopsies obtained from normal rats revealed no luminal surface FN by either immunofluorescent or immunoperoxidase staining. Extraction of epithelial surface proteins and quantitation of FN by rocket immunoelectrophoresis and electrophoretic transfer to nitrocellulose followed by immunologic detection also detected no FN from normal animals' oropharyngeal biopsies. Buccal epithelial biopsies from three normal humans were examined for FN using electrophoretic transfer to nitrocellulose followed by immunologic detection, and no FN was demonstrable. Our results suggest that FN is not present on the oral epithelial surface of healthy rodents or humans, and that FN may not be involved in the pathogenesis of bacillary colonization.

Lung clearance of Staphylococcus aureus strains with differing protein A content: protein A effect on in vivo clearance

We have studied the clearance from murine lungs of two strains of Staphylococcus aureus, one possessing high and the other possessing low levels of protein A.S. aureus FDA 209 and S. aureus Wood 46 were assayed for their ability to bind mouse immunoglobulin G, using an indirect radioimmunoassay. S. aureus FDA 209 binding of mouse immunoglobulin was significantly greater than that of S. aureus Wood 46 (118,909 versus 37,845 cpm). Clearance of these two strains from the lung after a 30-min aerosol inoculation period was not significantly different. The percentage of bacteria remaining in the lung was 49.2 and 55.0% at 2h, 31.8 and 33.2% at 3 h, and 25.4 and 17.2% at 4 h for protein A-rich and protein A-poor strains, respectively (P greater than 0.20 at each time). These data suggest that the previously demonstrated in vitro antiphagocytic effect of protein A may not be relevant to pulmonary clearance mechanisms.

Pulmonary aspiration of gastric contents

A retrospective analysis of 50 patients who had been observed to aspirate gastric contents was performed to define better the course of patients with this syndrome. The patients invariably had a disturbance of consciousness, most commonly due to sedative drug overdose or general anesthesia. The onset of clinical signs occurred prompty after aspiration and tended to be similar in all patients, irrespective of their subsequent course or outcome. These findings usually included fever, tachypnea, diffuse rales, and serious hypoxemia. Cough, cyanosis, wheezing, and apnea were each seen in approximately one third of the cases. Apena, shock, and early severe hypoxemia were particularly ominous events. Initial roentgenograms revealed diffuse or localized alveolar infiltrates, which progressed during the next 24 to 36 hours. Subsequent clinical courses followed 3 patterns: 12 per cent of the patients died shortly after aspiration; 62 per cent had rapid clinical and radiologic improvement, with clearing, on average, within 4.5 days; 26 per cent demonstrated rapid improvement, but then had clinical and radiographic progression associated with recovery of bacterial pathogens from the sputum and a fatal outcome in more than 60 per cent. Treatment from the outset by adrenocortical steroids or antimicrobial agents had no demonstrable effect on the outcome. The clinical features of aspiration of gastric contents are characteristic and distinguish it from other forms of aspiration-related lung disease.

Animal model of neutropenia suitable for the study of dual-phagocyte systems

When two sets of phagocytic cells participate simultaneously in the inflammatory process and bacterial killing, the relative contribution of each cell type is difficult to ascertain. The use of cell-specific antibody will permit selective depletion of one phagocyte population. We describe an experimental model of granulocytopenia which utilizes the immunoglobulin G fraction of an antigranulocyte serum. This material markedly depleted circulating polymorphonuclear leukocytes (PMN); within 2 h after injection of antigranulocyte globulin, PMN counts were at 19% of original levels and remained significantly depressed for 24 h. Granulocyte recruitment was also impaired, with only 5 x 10(3) PMN appearing in the lungs in response to an aerosol of Klebsiella, compared to 4.17 x 10(5) PMN in control animals (P less than 0.01). Most importantly, alveolar macrophages retained normal viability (97% versus 94% for control value, P not significant) normal phagocytic function, and normal bactericidal capacity. Antigranulocyte globulin is thus a valuable tool for the study of bacterial defense mechanisms.

Pneumoconiosis among the activated-carbon workers

The prevalence of respiratory symptoms and chest radiographic and spirometric abnormalities was assessed among 397 employees of an activated carbon plant. Definite radiographic findings of pneumoconiosis, consisting of p-type, rounded opacities in the lower lung fields without firbosis or coalescence, were present in 9.6% of men and were related to cumulative dust exposure. Lesser degrees of radiographic abnormality suggesting pneumoconiosis were present in 11% of men and 2% of women. Spirometric values were substantially lower in blacks than in whites. However, cumulative dust exposure was not an important determinant of pulmonary function in either race. Review of lung biopsy speciments that had been obtained previously in two employees revealed extensive carbon depositiion but minimal associated fibrosis. Prolonged inhalation of activated carbon dust leads to pulmonary deposition of carbon and raciographic signs of pneumoconiosis; such deposition has little, if any, effect on respiratory symptoms or pulmonary function.

Pulmonary elastase activity in response to Streptococcus pneumoniae and Pseudomonas aeruginosa

Elastase activity generated during lung defense against aerobic bacteria was studied in an animal model. Bronchoalveolar lavage (BAL) fluid from hamsters inoculated with bacteria was assayed for elastase activity at 0, 2, 4, 6, and 8 h after inoculation using a synthetic substrate of elastase, succinyl-trialanine-nitroanilide (SLAPN). Streptococcus pneumoniae type 25 inoculation led to a peak elastase activity of 0.72 +/- 0.27 X 10(-3) units, not significantly different from baseline (0.41 +/- 0.08 X 10(-3) units) or saline control (0.33 +/- 0.18 X 10(-3) units). In contrast, inoculation with Pseudomonas aeruginosa strain PAO-1 (a species known to produce elastase as well as other virulence factors) produced peak elastase activity of 3.0 +/- 1.2 X 10(-3) units in BAL fluid, significantly higher than either pneumococcus type 25 or saline control (p less than 0.025). Inoculation with Pseudomonas aeruginosa strain E-64, an isogenic mutant of PAO-1 that produces a nonfunctional elastase, led to peak levels similar to the PAO-1 strain, suggesting that the presence of bacterial elastase was not the primary factor in BAL fluid elastase activity. Total numbers of granulocytes in BAL fluid from pneumococcus-inoculated animals (144 +/- 31 X 10(6] was significantly higher (p less than 0.05) than from either the PAO-1 (74 +/- 31 X 10(6] or E-64 (99 +/- 27 X 10(6] strains of Pseudomonas, Use of selective enzyme inhibitors of elastase, diisopropyl fluorophosphate and disodium ethylenediaminetetraacetate, implied that the majority of elastase activity in BAL fluid was due to a serine protease, of which granulocyte elastase is the primary source.(ABSTRACT TRUNCATED AT 250 WORDS)

Increased salivary elastase precedes gram-negative bacillary colonization in postoperative patients

The upper airway epithelium is coated with fibronectin, a glycoprotein that covers receptor sites for gram-negative bacteria and prevents them from colonizing the oropharynx. We investigated the identity of salivary proteolytic enzymes capable of degrading fibronectin in a group of 16 patients who had elective cardiac surgery. Six patients became colonized with gram-negative bacteria (Group C) and 10 did not (Group NC). Salivary elastase activity was low in both groups preoperatively. Twenty-four hours after surgery, salivary elastase activity increased in Group C, and it remained elevated at 48 and at 72 h. Fibronectin digestive activity of the saliva of patients in Group C was also increased within 24 h of surgery, and salivary elastase and fibronectin digestive activity were highly correlated (r = 0.86, p less than 0.001). Enzyme inhibition experiments showed that most of the fibronectin digestive activity was due to elastase from polymorphonuclear cells (PMN), and the molecular weight of the salivary enzyme digesting fibronectin was 30,000 daltons (similar to the molecular weight of elastase). Levels of antileukoprotease, the major elastase inhibitor in saliva, were normal in patients with increased elastase activity. We conclude that salivary elastase is of PMN origin, increases prior to gram-negative bacillary colonization of the pharynx, and is responsible for most of the fibronectin digestive activity of the saliva.

Early pulmonary granulocyte recruitment in response to Streptococcus pneumoniae

Although polymorphonuclear leukocytes (PMN) are a conspicuous histologic feature of clinical and experimental pneumococcal pneumonia, neither the mechanism nor the magnitude of recruitment of these cells to the lung following lesser pneumococcal challenge is known. We have, therefore, investigated the early process of recruitment of PMN to alveolar spaces after pulmonary inoculation of Streptococcus pneumoniae in doses less than those causing pneumonia. We injected Balb/c mice with water and varying inoculums of pneumococci via an endobronchial catheter. Bronchoalveolar lavage (BAL) was performed on the inoculated lung at 0, 2, or 4 h after injection. Cellular response was measured and chemotactic activity was assayed on BAL supernatants at each time interval using the migration of human PMN through 3-micron filters in modified Boyden chambers by the leading front techniques. The BAL of normal and control animals (inoculum of sterile water only used for the control animals) yielded 5.03 +/- 1.51 X 10(2) and 0.17 +/- 0.04 X 10(5) PMN, respectively. The PMN recruitment at 4 h as a function of pneumococcal inoculum was described by the following equation: log PMN = 0.751 log Pn + 1.119 (r2 = 0.82, p less than 0.001). The PMN were, therefore, recruited in a dose-dependent manner. That recruitment may be caused by chemotactic substance(s) was suggested by the significant correlation between the PMN response and the distance of in vitro migration: log PMN = 0.057 micron + 0.52 (r = 0.77, p less than 0.005). We have defined quantitatively the recruitment of PMN to the lung after pneumococcal challenge.(ABSTRACT TRUNCATED AT 250 WORDS)

Pulmonary clearance and phagocytic cell response to normal pharyngeal flora

Because human lungs are repetitively inoculated with the normal bacterial flora of the pharynx, we determined the pulmonary clearance of representative species after aerosol inoculation of a murine model, and characterized the phagocytic cell response by bronchoalveolar lavage. Viable bacteria remaining in the lungs at 1, 2, and 4 h were: Streptococcus sanguis, 24%, 8%, and 1%; Streptococcus salivarius, 49%, 24%, and 5%; Neisseria catarrhalis, 69%, 49%, and 22%. Clearance of Streptococcus sanguis was associated with a twofold increase in alveolar macrophages (p less than 0.05); Streptococcus salivarius evoked a doubling of alveolar macrophages and a 20-fold rise in granulocytes (p less than 0.05); the response to Neisseria catarrhalis was a 400-fold increase in granulocytes (p less than 0.05). Thus, normal pharyngeal organisms are cleared rapidly from the lung by a dual phagocytic cell system. It is speculated that bacteria-phagocyte interaction allows the possibility of lung injury from proteolytic enzymes released from either set of phagocytes.

Clearance of Serratia marcescens from Lungs of Normal Mice

After aerosol deposition of Serratia marcescens in mice, initial delayed pulmonary clearance was followed between 4 and 24 hr later by progressive elimination.

Exposure chamber for 66 mice suitable for use with the henderson aerosol apparatus

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Treatment of pneumonia in patients at risk of infection with gram-negative bacilli

Patients with a history of chronic debilitating disease due to a variety of causes are known to be at risk for infection with coliform gram-negative bacilli when they present with community-acquired pneumonia. Empiric treatment with broad-spectrum parenteral antibiotics is often begun in such patients pending the result of blood and other cultures. The optimal duration of broad-spectrum empiric therapy in such patients when cultures fail to reveal a specific pathogen is unknown. Review was made of the charts of 131 patients with community-acquired pneumonia admitted to the hospital and treated with broad-spectrum parenteral antibiotics in whom a specific pathogen was never isolated. Overall, 89 percent of these patients were cured without complication or relapse. Patients receiving broad-spectrum therapy for four days or less due to rapid clinical improvement had a successful outcome in 95 percent of cases. It is concluded that broad-spectrum parenteral antibiotic therapy can safely be abbreviated provided response to therapy is prompt.