Adaptive immune responses of patients with asthma to the attachment (G) glycoprotein of respiratory synctial virus

A history of acute bronchiolitis in infancy caused by respiratory syncytial virus is a risk factor for recurrent wheezing in early childhood. Because the attachment (G) protein sensitizes mice for pulmonary eosinophilia and because Th2 cells are central in the pathogenesis of asthma, plasma and peripheral blood mononuclear cells (PBMC) from donors with asthma and from healthy donors were evaluated for anti-G protein responses. A significant trend connecting severity of asthma with anti-G protein IgG1 and IgG2 titers was observed. The correlation between anti-F protein IgG3 titers and asthma severity approached significance. Peptide mapping studies revealed that more positive recall responses (interferon-gamma and interleukin-10 secretion) occurred after PBMC from donors with asthma were stimulated with peptides representing the nonglycosylated domain of G protein. The same peptides elicited more positive recall responses (proliferation and interferon-gamma secretion) in the PBMC of healthy donors. These data suggest that a mechanism may exist whereby adaptive immune responses against G protein contribute to wheezing.

Impact of low birth weight on early childhood asthma in the United States

OBJECTIVE

To estimate the independent contribution of birth weight to asthma prevalence among children younger than 4 years in the United States and to compare the magnitude of its effect on asthma between African American and white children.

DESIGN

Cross-sectional analysis using the 1988 National Maternal-Infant Health Survey and 1991 Longitudinal Follow-up Survey.

SETTING

United States.

PATIENTS

Eight thousand seventy-one subjects, selected from a randomized, systematic population-based sample and weighted to be nationally representative, who completed both initial and longitudinal follow-up surveys and reported information on asthma diagnosis.

MAIN OUTCOME MEASURES

Birth weight and other sociodemographic factors linked to birth outcome were analyzed for independent association with physician-diagnosed asthma by age 3 years.

RESULTS

The prevalence of asthma varied by birth weight category: 6.7% in children 2500 g or more at birth, 10.9% in children 1500 to 2499 g at birth, and 21.9% in children less than 1500 g at birth (very low birth weight [VLBW]) (P<.001). Some of the characteristics shown to be independently associated with asthma included: VLBW (odds ratio [OR], 2.9; 95% confidence interval [CI], 2.3-3.6), moderately low birth weight (OR, 1.4; 95% CI, 1.1-1.8), and African American race (OR, 1.9; 95% CI, 1.6-2.4). In stratified analyses, the independent association between VLBW and asthma in white and African American populations was: OR(white), 3.1 (95% CI, 2.2-4.3) and OR(African American), 2.5 (95% CI, 2.0-3.3). The prevalence of VLBW, however, was tripled in African American compared with white children (1.8% vs 0.6%).

CONCLUSIONS

These data confirm findings of other studies that identify a strong independent association between low birth weight and asthma. For this 1988 national birth cohort, an estimated 4000 excess asthma cases were attributable to birth weight less than 2500 g. Although the strength of the independent association between VLBW and asthma was smaller in the African American population, the substantially increased prevalence of VLBW in this community may contribute to the disproportionately increased prevalence of asthma among African American children.

Inadequate therapy for asthma among children in the United States

OBJECTIVE

Childhood asthma morbidity and mortality are increasing despite improvements in asthma therapy. We hypothesized that a substantial number of children with moderate to severe asthma are not taking the maintenance medications recommended by national guidelines. The objective of this study was to describe medication use among US children with asthma and determine risk factors for inadequate therapy.

METHODS

The National Health and Nutrition Examination Survey (NHANES) III 1988-1994 provided cross-sectional, parent-reported data for children 2 months to 16 years of age. Analysis focused on children with moderate to severe asthma (defined as having any hospitalization for wheezing, >/=2 acute visits for wheezing, or >/=3 episodes of wheezing over the past year). We defined these children as adequately treated if they had taken a maintenance medication (inhaled corticosteroid, cromolyn, or theophylline) during the past month. Demographic variables were analyzed for independent associations with inadequacy of therapy. The statistical analysis used SUDAAN software to account for the complex sampling design.

RESULTS

A total of 1025 children (9.4%) had physician-diagnosed asthma. Of those with moderate to severe asthma (n = 524), only 26% had taken a maintenance medication during the past month. Even among children with 2 or more hospitalizations over the previous year, only 32% had taken maintenance medications. In a logistic regression analysis, factors significantly associated with inadequate therapy included: age </=5 years, Medicaid insurance, and Spanish language. Children surveyed after 1991, when national guidelines for asthma management became available, were no more likely to have taken maintenance medications than children surveyed before 1991.

CONCLUSION

Most children with moderate to severe asthma in this nationally representative sample, including those with multiple hospitalizations, did not receive adequate asthma therapy. These children may incur avoidable morbidity. Young children, poor children, and children from Spanish-speaking families appear to be at particularly high risk for inadequate therapy.

Immune-mediated inflammation directly impairs pulmonary function, contributing to the pathogenesis of Pneumocystis carinii pneumonia

The clinical severity of Pneumocystis carinii pneumonia (PCP) correlates closely with the appearance of pulmonary markers of inflammation. Therefore, a model system was developed whereby physiological studies could be performed on live mice to determine the extent to which pulmonary inflammation contributes to respiratory impairment during PCP. P. carinii-infected severe combined immunodeficient mice displayed little evidence of pulmonary inflammation and exhibited normal oxygenation and dynamic lung compliance. When comparably infected littermates were immunologically reconstituted, however, an intense immune-mediated inflammatory response was observed that resulted in significant decreases in both lung compliance and oxygenation. As the pneumonia resolved pulmonary function returned toward normal. To begin to define the cell populations contributing to inflammation-associated respiratory impairment during PCP, similar studies were performed in CD4(+) T cell-depleted mice. Mice depleted of both CD4(+) and CD8(+) cells developed infection, but they demonstrated neither abnormal lung compliance nor increased respiratory rate and displayed no markers of lung injury. In contrast, mice depleted of only CD4(+) T cells exhibited severe pulmonary inflammation and injury, decreased oxygenation and lung compliance, and increased respirations. Respiratory compromise was associated with the presence of activated CD8(+) cells and neutrophils in broncho-alveolar lavage fluid. These observations provide direct experimental evidence that the host's response to P. carinii directly impairs pulmonary function and contributes to the pathogenesis of PCP. Furthermore, CD8(+) T cells likely contribute to the respiratory compromise observed during PCP.

Increase in admission threshold explains stable asthma hospitalization rates

BACKGROUND

Asthma morbidity and mortality has increased substantially in recent years, but asthma hospitalization rates among many geographic and sociodemographic groups have remained stable. Observations on asthma hospitalization rates and severity of acute episodes might provide valuable insight into the functioning of the health care system during this period of health care reform.

OBJECTIVE

To analyze changes between 1991 and 1995 in childhood asthma hospitalization rates and severity of acute episodes.

DESIGN AND METHODS

All 29 329 hospitalizations, including 2028 for asthma, for the 198 893 children (<19 years of age) in Monroe County (Rochester), New York, were studied during this 5-year period. Severity was determined by hospital record review on a 22% random sample. Using the worst oxygen saturation (SaO(2)) during the first 24 hours of hospitalization as the primary index of severity, episodes were categorized as mild (0 to >/=95), moderate (90 to 94), or severe (<90).

RESULTS

Hospitalization rates are expressed as hospitalizations per 1000 child-years. The overall asthma hospitalization rate was 2.04 (95% confidence interval, 1.95-2.13). The overall annual asthma hospitalization rate remained relatively stable from 1991 (1.90) to 1995 (2.31), whereas the hospitalization rates for severe asthma rose 270%-from 0.57 to 1.55-during this period. Simultaneously, the hospitalization rates for mild asthma decreased from 0.26 to 0.12. As a proportion of all asthma hospitalizations between 1991 and 1995, severe episodes increased from 31.5% to 60.4%; conversely, mild episodes decreased from 14.1% to 4.7%.

CONCLUSIONS

Severity increased significantly among children hospitalized for asthma while the overall asthma hospitalization rate remained stable. It seems that the health care system in this community has responded to an increase in severity of asthma by raising the severity threshold for admission.

Predicting deterioration in previously healthy infants hospitalized with respiratory syncytial virus infection

OBJECTIVE

To estimate the incidence of clinical deterioration leading to intensive care unit transfer in previously healthy infants with respiratory syncytial virus (RSV) infection hospitalized on a general pediatric unit and, to assess the hypothesis that history, physical examination, oximetry, and chest radiographic findings at time of presentation can accurately identify these infants.

STUDY DESIGN

A virology database was used to identify and determine the disposition of all children </=1 year of age admitted to the Children's Hospital at Strong (CHaS) with RSV infection during the 1985 to 1994 respiratory seasons. Index patients were all previously healthy, full-term infants admitted initially to the general inpatient services at CHaS or Rochester General Hospital, a second University of Rochester teaching hospital, whose clinical deterioration led to transfer to the pediatric intensive care unit (PICU). These infants were matched retrospectively (for year and date of infection, sex, chronologic age, and race) with two hospitalized controls who did not require PICU transfer. Chest radiographic findings, respiratory rate (RR), O(2) saturation, and presence of wheezing at time of presentation to the emergency department (ED) were compared.

RESULTS

During the study years, 542 previously healthy, full-term infants were admitted to the general pediatric unit at CHaS with proven RSV infection. Ten (1.8%; 95% confidence interval, 0.9%, 3.4%) were transferred subsequently to the PICU, primarily for close monitoring of progressive respiratory distress. Data for these patients and 7 patients transferred from Rochester General Hospital to the PICU at the CHaS were compared with those for control patients. The mean RR in the ED (63 vs 50), and O(2) saturation in the ED (88% vs 93%) were modestly abnormal in cases compared with controls. Wheezing on examination at time of presentation and chest radiographic findings did not differ between the two groups. A RR >80 and an O(2) saturation <85% at time of presentation each had a specificity >97% for predicting subsequent deterioration. Each parameter, however, had a sensitivity </=30%.

CONCLUSION

Clinical deterioration requiring PICU admission is an uncommon occurrence in previously healthy infants admitted to a general pediatric inpatient unit with RSV infection. Extreme tachypnea and hypoxemia were both associated with subsequent deterioration; however, only a small proportion of patients who clinically deteriorated presented in this way. The clinical usefulness of these parameters, therefore, is limited. respiratory syncytial virus, deterioration, healthy infants, prediction.

Pulmonary function changes in children after respiratory syncytial virus infection in infancy

During the last 20 years, an association between respiratory syncytial virus (RSV) bronchiolitis or pneumonia in infants and abnormal pulmonary function later in childhood has been established. Study designs have varied considerably, but most investigators have used an observational approach in which children with early bronchiolitis or pneumonia are identified and pulmonary function is measured later in childhood. Decreased forced expiratory flows at mid-lung volumes and increased airway reactivity have been demonstrated consistently in most studies. Few studies, however, have addressed the issue of whether the early symptomatic RSV infection caused the subsequent abnormalities in pulmonary function. An atopic tendency does not appear to explain the underlying association between early RSV infection and subsequent abnormal pulmonary function. Evidence suggests that infants with symptomatic bronchiolitis have an underlying deficit in pulmonary function that might contribute to the abnormalities documented later in childhood. The issue of causation could be addressed by intervention studies in which RSV is prevented or treated and differences in pulmonary function are observed. Several small prospective studies of children enrolled in early controlled trials of ribavirin treatment of RSV lower respiratory tract infection have not consistently demonstrated differences between infants in treated and control groups. Larger studies of the effect of ribavirin treatment, immunoglobulin prophylaxis, or immunization (when it becomes available) on subsequent pulmonary function and airway hyperreactivity may resolve this important issue.

Socioeconomic variation in asthma hospitalization: excess utilization or greater need?

OBJECTIVE

To assess the hypothesis that higher incidence of severe acute asthma exacerbation, not lower severity threshold for admission, explains the difference between the asthma hospitalization rates of inner-city and suburban children.

METHODS

All 2028 asthma hospitalizations between 1991 and 1995 for children (aged >1 month and <19 years) dwelling in Rochester, New York, were analyzed. ZIP codes defined residences as inner-city, other urban, or suburban. Based principally on the worst oxygen saturation (SaO2) during the first 24 hours of hospitalization, severity was examined by hospital record review (n = 443) of random samples of inner-city, other urban, and suburban asthma admissions.

RESULTS

Large inner-city/suburban differences were noted in many sociodemographic attributes, and there was also a distinct, stepwise gradient in risk factors in moving from the suburbs to other urban areas and to the inner city. Racial and economic segregation was particularly striking. Black individuals accounted for 62% of inner-city births versus <3% in the suburbs. Medicaid covered 65% of inner-city births, whereas Medicaid covered only 6% of suburban births. The overall asthma hospitalization rate was 2.04 admissions/1000 child-years. Children <24 months old, those most commonly hospitalized for asthma, were fourfold more likely to be hospitalized (OR: 3.97, 95% CI: 3. 44-4.57) than children between the ages of 13 and 18 years. The hospitalization rate of asthma in boys was almost twice the rate of asthma in girls. The greatest gender difference was observed among children who were <24 months old. For these children, the rate for boys was 6.10/1000 child-years compared with 2.65/1000 child-years for girls (OR: 2.31, 95% CI: 1.95-3.03). This gender difference diminished gradually in older age groups to the extent that there was no difference among girls and boys between the ages of 13 and 18 years (males, 1.12/1000 child-years vs females, 1.09/1000 child-years). Based on worst SaO2 values, mild (worst SaO2 >/=95%), moderate (90%-94%), and severe (<90%) admissions constituted 10.3%, 41.9%, and 47.7% of all hospitalizations, respectively. Although rates within the community followed a distinct geographic pattern of suburban (1.05/1000 child-years) < other urban (2.99/1000 child-years) < inner-city (5.21/1000 child-years), the proportions of admissions with low severity did not vary among areas. Likewise, the proportions of admissions that were severe (SaO2 <90%) were not significantly different (44.8, 45.7, and 52.1% for suburban, other urban, and inner-city areas, respectively). The distributions of asthma severity, measured by the duration of frequent nebulized bronchodilator treatments and the length of hospital stay, were also similar among children from different socioeconomic areas.

CONCLUSION

The marked socioeconomic and racial disparity in Rochester's asthma hospitalization rates is largely attributable to higher incidence of severe acute asthma exacerbations among inner-city children; it signals greater need, not excess utilization. Both adverse environmental conditions and lower quality primary care might explain the higher incidence. Interventions directed at the environment offer the possibility of primary prevention, whereas primary care directed at asthma is focused on secondary prevention, principally on improved medication use. Higher hospitalization rates cannot be assumed to identify opportunities for cost reduction. The extent to which our observations about asthma hold true under other conditions and in other communities warrants systematic attention. Knowledge of when higher rates signal excess utilization and when, instead, they signify greater needs should guide equitable national health policy.

How commonly are children hospitalized for asthma eligible for care in alternative settings?

OBJECTIVE

To estimate the proportion of children hospitalized for acute asthma exacerbation who might be cared for successfully in alternative settings such as short-stay units or in-home nursing.

DESIGN

Descriptive study based on analysis of hospital discharge files and on retrospective medical record review of a random sample of asthma hospitalizations.

METHODS

The 2028 asthma hospitalizations between 1991 and 1995 for children (aged <19 years) dwelling in Rochester, NY, were studied. Measures included the duration of frequent administration of nebulized medication (2 or more times in a 4-hour period), worst oxygen saturation levels, deterioration, and hospital length of stay. Oxygen saturation values and nebulized medication frequency were determined by hospital record review on a random sample of 443 asthma episodes. Length of stay was available for all admissions.

RESULTS

Worst oxygen saturation following hospital admission was 95% or greater, 90% to 94%, and less than 90% for 21.3%, 51.6%, and 27.1% of episodes, respectively. Children received frequent nebulized medication treatments for a mean of 2.0 nursing shifts (8 hours per shift), although they remained hospitalized, on average, for 4.3 nursing shifts longer. Deterioration to a critical level of severity was uncommon. Among children initially admitted to the regular pediatric inpatient unit, only 0.7% subsequently deteriorated to the point that they were transferred to the critical care unit.

CONCLUSION

More than 70% of asthma hospitalizations in this community could be cared for in alternative settings with supplemental oxygen, nebulized medication treatments, and close nursing observation provided, in most cases, for 2 nursing shifts.

Changes in alveolar septal border lengths with postnatal lung growth

Evaluation of alveolar development beyond the postnatal period of rapid septation has generally involved alveolar counting. We used an alternate approach to assess postseptation parenchymal development: measurement of the lengths of various types of alveolar septal borders. This technique directly addresses changes in the elastin fiber network that determines parenchymal complexity. Lungs from weanling and adult ferrets, inflated to 15 cmH2O, were perfusion fixed and dehydrated, and 2-micrometer sections were stained with Miller's elastin stain for light microscopy. We used standard morphometric methods to measure the lengths of the various types of alveolar septal borders. Three types comprised >90% of all septal borders: 1) free septal ends ("ends") containing an elastin cable; 2) angled meetings of two alveolar septa ("bends"), also with a cable; and 3) the near-symmetrical intersections of three septa ("junctions") devoid of elastin. When scaled for lung volume, ends and bends were 23 and 37% greater in adults (P < 0.001), reflecting the increase in parenchymal complexity with growth. The 17% difference in scaled junction lengths was not significant (P = 0.10). Bends increased out of proportion to the increase in ends, and both bends and ends increased to a greater degree than any possible increase in junctions (P < 0.001 for all comparisons). Although the interpretation of changes in the distribution of alveolar border lengths is not straightforward, an increase in bends resulting in an increase in the complexity of individual alveoli may contribute to the increase in alveolar gas-exchanging surface area with growth. Septation, the process responsible for the rapid early postnatal increase in parenchymal complexity in many species, should tend to increase the lengths of ends and junctions and decrease the lengths of bends. Therefore, these data suggest that septation is not the predominant mechanism of later postnatal parenchymal development in the ferret.

Ensuring high-quality alternatives while ending pediatric inpatient care as we know it

Child advocates recognize pediatric hospitalization as an issue of great concern because of the serious morbidity it reflects and the adverse psychosocial effects of inpatient experience on children and families. Accounting for almost 50% of child health care costs, estimated at $49.8 billion in the United States in 1987, pediatric hospitalization also represents a substantial financial burden. Studies of the variation in childhood hospitalization rates among geographic areas, however, suggest a large portion of these hospitalizations are avoidable. In individual level analysis, admitting pediatricians judged 28% of acute, general pediatric hospitalizations to be potentially avoidable had specified alternative services been available. Furthermore, evidence supports the safety of care in alternative settings for selected acute illness episodes. Hospitals share incentives for reducing inpatient services as they join managed care organizations that capitate hospital costs. At a time when health care cost reduction has become a dominant theme in industry and politics, concern seems warranted that cost considerations might prevail over quality considerations in shaping change. The concern of child advocates is heightened by the fact that costs are measured as dollars while measures of quality remain comparatively vague.

Cell proliferation contributes to PNEC hyperplasia after acute airway injury

Pulmonary neuroendocrine cells (PNECs) are airway epithelial cells that are capable of secreting a variety of neuropeptides. PNECs are scattered throughout the bronchial tree either as individual cells or clusters of cells termed neuroepithelial bodies (NEBs). PNECs and their secretory peptides have been considered to play a role in fetal lung development. Although the normal physiological function of PNECs and neuropeptides in normal adult lungs and in repair from lung injury is not known, PNEC hyperplasia has been associated with chronic lung diseases, such as bronchopulmonary dysplasia, and with chronic exposures, such as hypoxia, tobacco smoke, nitrosamines, and ozone. To evaluate changes in PNEC number and distribution after acute airway injury, FVB/n mice were treated with either naphthalene or vehicle. Naphthalene is an aromatic hydrocarbon that, at the dose used in this study, selectively destroys nonciliated bronchial epithelial cells (Clara cells) through cytochrome P-450-mediated metabolic activation into cytotoxic epoxides. PNECs were identified by immunohistochemical analysis of calcitonin gene-related peptide-like immunoreactivity (CGRP-IR). Proliferating cells were marked with [(3)H]thymidine incorporation. Acute naphthalene toxicity results in PNEC hyperplasia that is detectable after 5 days of recovery. PNEC hyperplasia is characterized by increased numbers of NEBs without significant changes in the number of isolated PNECs and by increased [(3)H]thymidine labeling of CGRP-IR cells. These data show that cell proliferation contributes to PNEC hyperplasia after acute airway injury and suggest that PNECs may be capable of more rapidly increasing their number in response to injury than previously recognized.

Strain-induced growth of the immature lung

To investigate the relationship between strain and postnatal lung growth, two groups of weanling ferrets were tracheotomized: the study group was exposed for 2 wk to a continuous positive airway pressure (CPAP) of 6 cmH2O and the other group was exposed to atmospheric pressure (control). Total lung capacity after 2 wk was approximately 40% higher in the CPAP-exposed animals than in the control animals (n = 19 for the control group and 18 for the study group; P < 0.01). CPAP exposure was also associated with increases in lung weight and total lung protein and DNA contents. Lung recoil, measured in a subgroup of animals, was characterized by air-filled and saline-filled static expiratory pressure-volume curves. Neither in the air-filled lungs nor saline-filled lungs was there a significant difference between CPAP-exposed and control animals in lung recoil at equal fractions of total lung capacity. These data indicate that mechanical strain was associated with an acceleration of lung growth in immature ferrets. The preservation of volume-corrected lung recoil and the expected contribution of surface forces and tissue forces to lung recoil in CPAP-exposed animals suggest that this response did not involve simple lung distension but included a remodeling of the lung parenchyma.

Diagnostic tests of lung function

Objective measurements of a wide variety of aspects of respiratory function can be useful in the evaluation and management of children and adolescents who have respiratory symptoms or disorders. Many of the tests described in this article can be performed reasonably in the pediatrician's office. Pediatricians can be comfortable in measuring and interpreting pulse oximetry, blood gas analysis, spirometry, and peak flow. They also should be familiar with the indications for the less common tests of pulmonary function that now are widely available.

Sequelae of respiratory syncytial virus infections. A role for intervention studies

The association between respiratory syncytial virus (RSV) infections in infancy and respiratory abnormalities later in life has been attributed both to a direct effect of the infection itself and to an inherent susceptibility. Observational studies do not allow a rigorous test of these hypotheses. Respiratory syncytial virus infection is universal in the first years of life and no uninfected control group exists. Randomized, controlled trials using new prophylactic agents such as vaccines or specific therapeutic agents will provide a powerful test of the relationship between RSV infection and long-term respiratory sequelae.

Long-term results of valve replacement with the St. Jude Medical prosthesis

To assess with truly long follow-up the long-term results of valve replacement with the St. Jude Medical prosthesis (St. Jude Medical, Inc., St. Paul, Minn.), we reviewed the case histories of the first 1112 patients undergoing 1244 valve replacements with this valve between June 12, 1978, and June 12, 1987: 690 male (62%) and 422 female patients, mean age 56 years. A total of 773 patients (69%) had the aortic valve replaced, 207 (19%) the mitral valve, and 132 (12%) the aortic and mitral valves. There were 42 hospital deaths (3.8%). Follow-up was 97.5% complete (8988 patient-years). There were 213 late deaths. Ninety-one (43%) were considered valve-related: sudden death, n = 27; anticoagulant-related hemorrhage, n = 22; thromboembolism, n = 19; prosthetic valve endocarditis, n = 13; valve thrombosis, n = 9; and noninfectious perivalvular leak, n = 1. Overall actuarial survival, including hospital mortality, was 68% +/- 6% (95% confidence limits) 14 years after the operation. Linearized rates of late valve-related events were as follows: thromboembolism, 1.09% per patient-year; anticoagulant-related hemorrhage, 0.94% per patient-year; prosthetic valve endocarditis, 0.32% per patient-year; valve thrombosis, 0.33% per patient-year; and perivalvular leak, 0.19% per patient-year. Actuarial freedom, at 14 years, from thromboembolism was 89% +/- 3%, anticoagulant-related hemorrhage 83% +/- 8%, valve thrombosis 97% +/- 1%, and reoperation 95% +/- 3%. Actuarial freedom from all valve-related deaths and valve-related morbidity and mortality, at 14 years, was 84% +/- 6% and 61% +/- 8%, respectively. We conclude that, because of its low thrombogenicity, low incidence of valve-related events, and low valve-related mortality, the St. Jude Medical valve is one of the best performing mechanical prosthesis currently available. Nevertheless, the late valve-related complications and deaths illustrate that the quest for a "perfect" prosthesis remains unfulfilled.

Arthroscopic Bankart repair versus nonoperative treatment for acute, initial anterior shoulder dislocations

A prospective study evaluating nonoperative treatment versus arthroscopic Bankart suture repair for acute, initial dislocation of the shoulder was undertaken in young athletes. All patients met the following criteria: 1) sustained an acute first-time traumatic anterior dislocation, 2) no history of impingement or occult subluxation, 3) the dislocation required a manual reduction, and 4) no concomitant neurologic injury. Thirty-six athletes (average age, 20 years) met the criteria for inclusion. Group I patients were immobilized for 1 month followed by rehabilitation; they were allowed full activity at 4 months. Group II patients underwent arthroscopic Bankart repair followed by the same protocol as Group I. Group I consisted of 15 athletes. Twelve patients (80%) developed recurrent instability; 7 of the 12 have required open Bankart repair for recurrent instability. Group II consisted of 21 patients; 18 patients (86%) had no recurrent instability at last followup (average, 32 months; range, 15 to 45) (P = 0.001). One patient in Group II has required a subsequent open Bankart repair to treat symptomatic recurrence (P = 0.005). In this study, arthroscopic Bankart repair significantly reduced the recurrence rate in young athletes who sustained an acute, initial anterior dislocation of the shoulder.

Role of pulmonary blood flow in postpneumonectomy lung growth

To study the influence of blood flow on postpneumonectomy lung growth, we banded the left caudal lobe pulmonary artery of eight ferrets in such a way that blood flow to the caudal lobe did not increase when the right lung was excised 1 wk later. The fraction of the cardiac output received by the right lung before pneumonectomy was therefore directed entirely to the left cranial lobe. Three weeks after pneumonectomy the weight, volume, and protein and DNA contents of the two lobes of the left lung were measured and compared with those of five unoperated animals and eight animals after right pneumonectomy alone. Although its perfusion did not increase after pneumonectomy, the left caudal lobe of banded animals participated in compensatory growth, increasing in weight and protein and DNA contents. Although the cranial lobe of banded animals received 25% more of the cardiac output than the same lobe in pneumonectomized animals, cranial lobe volume and protein and DNA contents in the two groups were similar. Caudal lobes were smaller in banded than in simple pneumonectomized animals and tended to contain less protein, whereas the cranial lobes tended to be heavier. We conclude that increased pulmonary perfusion is not necessary for compensatory lung growth in adult ferrets, but it may modify this response.

Simultaneous immunostaining method for localization of bromodeoxyuridine and calcitonin gene-related peptide

A new simultaneous double immunostaining method has been optimized to localize the DNA synthesis marker bromodeoxyuridine (BrdU) and calcitonin gene-related peptide (CGRP) in endocrine cells of Bouin's-fixed, paraffin-embedded rat lung. Nuclease pre-treatment before immunostaining is compatible with optimal tissue morphology and CGRP antigenicity preservation. Nickel-enhanced development of avidin-biotin-peroxidase staining is used to show CGRP immunoreactivity in black and alkaline phosphatase-anti-alkaline phosphatase is applied to demonstrate incorporated BrdU in red. The present methodology could be useful for studies requiring detection of incorporated BrdU in cells producing regulatory peptides or other labile antigens.

CGRP-immunoreactive endocrine cell proliferation in normal and hypoxic rat lung studied by immunocytochemical detection of incorporation of 5'-bromodeoxyuridine

We have tested the suggestion that the reported increase, in hypoxic rats, in the number of lung endocrine cells immunoreactive for the regulatory peptide CGRP is caused by an accumulation of peptide within the cells which renders them more detectable, rather than by a real increase in proliferation. The incorporation of continuously infused 5'-bromodeoxyuridine (BrdU) into nuclei of CGRP-containing cells was studied by immunohistochemistry in the airway and respiratory epithelium of rats kept in a hypoxic (10% O2), normobaric conditions for 7 days and in normoxic, normobaric controls. Some CGRP-immunoreactive cells could also be labelled for BrdU. However, the ratio of the number of cells labelled with both CGRP and BrdU to the number of cells labelled with CGRP alone did not differ significantly between hypoxic and normoxic rats (7.1 +/- 0.7 and 6.1 +/- 1.2, respectively; mean +/- SEM; P = 0.49). These data strongly suggest that CGRP-containing endocrine cells or their precursors do proliferate in adult rat lung, but that the proliferation is not increased significantly in hypoxia.

Quantitative immunocytochemistry shows calcitonin gene-related peptide-like immunoreactivity in lung neuroendocrine cells is increased by chronic hypoxia in the rat

We have previously shown that the vasodilator calcitonin gene-related peptide (CGRP) is increased in pulmonary neuroendocrine cells in response to hypoxia. To quantify the change, we have now examined lung of adult male Wistar rats exposed to hypoxia (FIO2 = 0.1) for 1 wk and littermate controls. Sections of lung were immunostained simultaneously using rabbit antiserum to rat alpha-CGRP with the peroxidase antiperoxidase technique. The area and integrated optical density of each group of endocrine cells were measured using an image analyzer. For each animal, the summed integrated optical density of endocrine cells divided by the sum of their areas was used as a measure of CGRP-like immunoreactivity. The intensity of immunostaining of endocrine cells in the respiratory portion of the lung was 43% greater than that of endocrine cells along the conducting airways (P less than 0.001). The intensity of staining was increased by approximately 12% (P less than 0.04) after 7 d of hypoxia with no apparent difference in the response of central and peripheral endocrine cells. Measurements of staining intensity of CGRP-coupled agarose beads indicated that a 12% change in staining intensity corresponded to a 15 to 20% change in the concentration of CGRP or CGRP-like immunoreactive material. The supra-optimal dilution technique (measurement of the increase in the number of immunoreactive cells upon sequential immunostaining with a supra-optimal and then an optimal dilution of primary antiserum) detected the increase in CGRP-like immunoreactivity after 7 d of hypoxia with a high degree of statistical significance (P less than 0.005) using the same number of sections.

Early ribavirin treatment of respiratory syncytial viral infection in high-risk children

A 3-year prospective, blinded, multicenter study was done to assess the efficacy of early ribavirin intervention in mild respiratory syncytial virus illness in children with bronchopulmonary dysplasia or with congenital heart disease. A cohort of 178 children younger than 36 months of age with bronchopulmonary dysplasia or congenital heart disease were followed. Forty-seven infants whose respiratory syncytial virus infection resulted in mild symptoms of less than or equal to 72 hours' duration received ribavirin (n = 20) or water placebo aerosol (n = 27) either in a hospital or at home. Outcome measures included respiratory and analog score, room air oxygen, saturation, and oxygen flow needed to maintain saturation at greater than or equal to 91%. No difference in age, gender, family size, passive smoking, baseline oxygen saturations in room air, or duration of symptoms before treatment was found between groups. After 3 days of therapy, ribavirin produced a greater rate of improvement of analog scores (p = less than or equal to 0.001), lower oxygen requirements (p = 0.01), and higher oxygen saturation (p = 0.01). Respiratory scores and total hospital days did not differ significantly between the groups. Treatment failure occurred in 2 of 20 children (10%) in the ribavirin group versus 5 of 27 children (18%) in the placebo group, a nonsignificant difference. No child required assisted ventilation or had an adverse reaction. We conclude that early ribavirin therapy may help to reduce morbidity from respiratory syncytial virus infection in high-risk young children.

Study design considerations for ribavirin: efficacy studies

Five placebo-controlled double-blind studies, each including approximately 30 subjects, have addressed the question of the effect of aerosolized ribavirin on the course of RSV lower respiratory infection in infancy. The fact that each was able to establish a beneficial effect despite the small number of subjects studied is convincing evidence that such an effect exists. The studies from Rochester using oximetry and an analog illness severity scale indicate that this effect is both statistically significant and clinically relevant. These tools are reliable and easily applicable measures for multicenter studies when illness severity is selected as an outcome measure. Characteristics that should be taken into consideration when assigning experimental groups include age, sex, a history of prematurity or underlying conditions and arterial oxygen saturation. Future studies will address additional questions about the efficacy of ribavirin, such as its role in critically ill children, the economic benefits of its use in terms of duration of hospitalization, the usefulness of early treatment of RSV disease in high risk infants, and the impact of treatment on long-term consequences of RSV infection. These studies may require outcome variables and subject selection strategies different from those used in earlier studies.

Effects of corticosteroids on postnatal lung and airway growth in the ferret

To investigate the influence of corticosteroids on postnatal lung and airway growth, young male ferrets were given cortisone acetate (20 mg/kg im daily) beginning at 8 wk of age. At 19 wk of age pulmonary function was measured. The lungs were excised for measurements of recoil pressures and wet and dry weights. The dimensions of central and peripheral airways were estimated from analysis of bronchial casts. Corticosteroid-treated animals were shorter and tended to be lighter than control animals but were heavier in relation to length. Total lung capacity was reduced in proportion to the reduction in body size. Lung recoil and wet-to-dry weight ratios were nearly identical. Maximal expiratory flows were reduced in proportion to the reduction in body size. Size-corrected airway conductance was reduced, suggesting a sensitivity of central airways to growth suppression by corticosteroids. Peripheral airways, on the other hand, were not smaller in treated animals and were larger in proportion to body size. In the ferret corticosteroid administration is associated with a suppression of lung parenchymal growth similar to that of overall body growth. The peripheral airways may be less sensitive and the central airways more sensitive to the effect of corticosteroids on growth.

Changes in airway length after unilateral pneumonectomy in weanling ferrets

We have previously shown that airway cross-sectional area increases 15-20% after pneumonectomy in weanling ferrets by measuring bronchial casts. We have now reanalyzed these same casts to quantitate changes in airway length after pneumonectomy. In each cast the distance from each of 120 airways to the terminal bronchiole along its axial pathway was measured. The relationship between the logarithm of this distance and that of the fraction of the lobe subtended by an airway could be described by a quadratic equation with a correlation coefficient greater than 0.85. Subsegmental and more distal airways of postpneumonectomy animals were 33-47% longer than those of controls. Overall the main axial pathway of airways in the left lower lobes was 12% longer in operated animals, but this increase was primarily accounted for by an increase in the length of the more peripheral airways. Central airways were little if any longer in operated animals. After pneumonectomy in weanling ferrets, subsegmental and peripheral airway lengths increase to a greater degree than lung volume and airway cross-sectional area, whereas central airway lengths increase to a lesser extent if at all. The mechanisms responsible for this difference between central and intralobar compensatory airway growth are unknown.

Lung volumes after an increase in lung distension in pneumonectomized ferrets

To investigate the role of lung distension in compensatory lung growth, the right lung of each of 21 adult male ferrets was replaced with a silicone rubber balloon filled with mineral oil. Three to thirteen weeks after surgery, the oil was removed through a subcutaneous port. Lung volumes were measured serially until 3-6 wk after balloon deflation. With pneumonectomy the total lung capacity (TLC) decreased to less than 50% of the preoperative value and remained essentially unchanged while the balloon was inflated. At balloon deflation, TLC and vital capacity did not change immediately, whereas functional residual capacity increased by 44%, indicating a change of 2-3 cmH2O in end-expiratory transpulmonary pressure. TLC increased by 10% within 3 days and continued to increase over the subsequent 3-5 wk by a total of 25% over TLC at balloon deflation. There was little difference in this response between animals whose balloons were deflated 3 wk after surgery and those in which deflation was delayed up to 13 wk. After pneumonectomy in the adult ferret, the remaining lung increases in volume in response to an increase in lung distension even weeks or months after surgery. The extent to which this volume increase involves lung tissue growth or depends on previous lung resection is at present unknown. This model may be useful for studies of the mechanisms by which lung distension influences lung volume and compensatory lung growth.

Ventilatory chemosensitivity in parents of infants with sudden infant death syndrome

We measured ventilatory responses to progressive isocapnic hypoxia and to hyperoxic hypercapnia (CO2) using rebreathing techniques in 16 parents of infants with autopsy-confirmed sudden infant death syndrome (SIDS) and 18 control parents matched for age, sex, and body size. Response to ventilatory loading was assessed by repeating the CO2 test with an inspiratory flow-resistive load (16 cm H2O/L/sec). During loaded and unloaded CO2 tests, respiratory effort was also assessed by measuring the pressure generated in the first 0.1 second (P0.1) of the subsequent inspiratory effort after brief manual occlusion of the inspiratory line. Ventilatory responses of the parents of victims of SIDS to chemical and mechanical stimulation were not significantly different from those of control parents. Responses in both groups were similar to previously reported normal values. There was a linear increase in ventilation (VE) in response to hypercapnia and hypoxia and in P0.1 in response to hypercapnia. We found expected increases in P0.1/PCO2 and decreases in VE/PCO2 slopes during loaded breathing in all subjects, but no difference between groups. We conclude that parents of SIDS victims have normal ventilatory chemosensitivity and respiratory drive.

Airway hyperreactivity and a history of clinical manifestations of asthma in childhood

The relationship between airway hyperreactivity and a history of the clinical manifestations of asthma was investigated in 54 children between the ages of 8 and 12. Airway reactivity was assessed by measuring the change in pulmonary function following the hyperventilation of subfreezing air. Clinical manifestations of asthma were assessed by a standardized questionnaire regarding lower respiratory symptoms and by medical records review. The subjects were participating in a study of the sequelae of bronchiolitis; 25 had seen a physician for mild bronchiolitis during the first 2 years of life, and the remainder had not. Airway hyperreactivity was demonstrated in 8 of the 54 children and correlated with use of medication for asthma in the 2 years before pulmonary testing and positive parental response to the question, "Does your child wheeze apart from colds?" Airway hyperreactivity did not correlate with a history of other respiratory symptoms or with a history of physician-diagnosed wheezing or asthma. No questionnaire or chart review item identified over 50% of the children with reactive airways, and most subjects identified by each of the items did not demonstrate hyperreactive airways. These data suggest that airway reactivity is only weakly associated with a history of the clinical manifestations of asthma in childhood, in part because children with clinically inactive asthma do not consistently demonstrate airway hyperreactivity and in part because many children with hyperreactive airways have never had respiratory symptoms.

Ribavirin treatment of respiratory syncytial viral infection in infants with underlying cardiopulmonary disease

Aerosolized ribavirin was evaluated in the treatment of respiratory syncytial virus lower respiratory tract disease in 53 infants, 36 of whom had underlying diseases. Of the total infants, 26 were studied in a double-blind, placebo-controlled manner; 14 received ribavirin and 12 received placebo, a water aerosol, for an average of five days. When the infants with bronchopulmonary dysplasia and congenital heart disease treated with ribavirin were compared with those receiving placebo, the treated infants showed a significantly faster rate of improvement in their illness severity score. The degree of improvement in the total group of infants receiving ribavirin compared with those receiving placebo was similarly greater, and at the end of therapy significantly greater improvement was also demonstrated in their arterial blood gas values and in the amount of virus shed from their nasal washes. No toxic or adverse effects of the aerosol therapy were observed in any of the 53 infants studied, and resistance to ribavirin did not develop in any of the respiratory syncytial virus strains isolated, despite prolonged treatment in some of the more ill infants.

Normal pulmonary function measurements and airway reactivity in childhood after mild bronchiolitis

Concern about the long-term sequelae of bronchiolitis has been raised through studies of children hospitalized for bronchiolitis, but the long-term sequelae of mild bronchiolitis have not been studied. We assessed the hypothesis that 25 children with mild bronchiolitis (index subjects) were at greater risk for abnormalities of pulmonary function or airway reactivity to cold air between the ages of 8 and 12 years than were randomly selected, matched controls. There were no consistent differences in pulmonary function or airway reactivity between index and control groups. Airway hyperreactivity was found in five control subjects and three index subjects, and all children with symptomatic asthma were identified by cold air challenge. Our data suggest that children with a history of mild bronchiolitis are not at increased risk between ages 8 and 12 years for airway hyperreactivity or for abnormalities in pulmonary function.

Postpneumonectomy airway growth in the ferret

To investigate the participation of the conducting airways in compensatory growth following partial lung resection, bronchial casts of six ferrets having undergone right-sided pneumonectomy at 8 wk of age were compared with those of five sham-operated control animals. At maturity, the left lungs of the postpneumonectomy animals were 65% larger than those of the controls. Central airway cross-sectional areas at 10 specific locations in each cast were 12% larger in the postpneumonectomy animals compared with controls. To characterize the size of more peripheral airways, the size and number of the terminal bronchioles subtended by each airway in each left lower lobe cast were identified so that the fraction of the lobe served by that airway could be estimated. The characteristic cross-sectional areas of airway serving 0.7, 2.2, and 9.5% of the left lower lobe in postpneumonectomy animals were 18, 13, and 13% larger than those of controls, but this difference was statistically significant only at the two more peripheral levels. Although airway areas were larger in postpneumonectomy animals, the ratio of airway cross-sectional area to the 0.67 power of lung volume was 20-26% smaller in operated than in control animals at each of the four levels. Following pneumonectomy in the weanling ferret, central and peripheral conducting airways increase in cross-sectional area to similar degrees, but this airway growth is less than the compensatory increase in lung volume.

A technique for quantitating airway size from bronchial casts

To develop a technique for quantitating the size of airways at various positions in the bronchial tree, we analyzed casts of formalin-fixed excised lungs of five mature male ferrets. The left lower lobe of each cast was dissected, the diameter and position of each terminal bronchiole were entered into a computer programmed to reconstruct the airway system, and the cross-sectional areas of 120 conducting airways were measured. The fraction of the lobe served by each measured airway was estimated by dividing the sum of the squared diameters of the terminal bronchioles subtended by that airway by the summed squared diameters of all terminal bronchioles in the lobe. In each cast the relationship between an airway's cross-sectional area (Y) and the fraction of the lobe it was estimated to subtend (X) was described (0.91 less than R2 less than 0.95) by the expression ln(Y) = A + B ln(X) + C [ln(X)]2. Linear regression of ln(Y) on ln(X) for 30-50 airways estimated to serve fractions of the lobe around each of three arbitrarily selected levels (airways serving 0.7, 2.2, and 9.5% of the lobe) was adequate to characterize the area of airways at each level in each of the five animals with 95% confidence intervals narrower than 8% of the estimated area. Variability of airway size at each level among the five casts was modest, suggesting that this technique identified analagous airways in the various animals. Interindividual variability did not increase when the data were reanalyzed with terminal units defined on the basis of airway diameters rather than on the morphological identification of terminal bronchioles.

Ventilatory chemosensitivity in subjects with a history of childhood cyanotic breath-holding spells

The ability of children with cyanotic breath-holding spells to respond to anger or frustration by voluntary breath-holding for prolonged periods (often to the point of precipitating hypoxic seizure activity) suggested the hypothesis that such children may have a less powerful urge to breathe in the presence of hypoxia and/or hypercapnia than children who do not have breath-holding spells. Because ventilatory chemosensitivity is difficult to measure in infants and young children, this hypothesis was tested indirectly by measuring the ventilatory responses to hyperoxic progressive hypercapnia and to isocapnic progressive hypoxia of seven individuals who had a history of cyanotic breath-holding spells in infancy and 17 control subjects. The mean values for sensitivity to hypoxia and to hypercapnia were not significantly different between the two groups, and the responses of the majority of the subjects with cyanotic breath-holding spells were clearly within the normal range. There were fewer individuals with high-normal ventilatory responses among the subjects with cyanotic breath-holding spells. Although children with cyanotic breath-holding spells may have decreased ventilatory chemosensitivity transiently during infancy or may differ from other children in some other aspect of the control of breathing, the pathogenesis of infantile cyanotic breath-holding spells does not involve a permanently blunted sensitivity to hypercapnia or hypoxia.

Stridor in childhood

The acute onset of stridor in a young child usually represents viral croup, particularly during the fall and early winter. If the clinical picture is entirely consistent with this diagnosis and gas exchange is maintained, management with cool mist at home is appropriate. Rapid deterioration is unusual in viral croup; however, if obstruction is prolonged or becomes unusually severe, racemic epinephrine aerosols, hospitalization for careful observation, a brief course of corticosteroid therapy, and, rarely, endotracheal intubation may be required. Many of the other causes of acute stridor in childhood represent true pediatric emergencies: epiglottitis, foreign body aspiration, bacterial tracheitis, allergic airway edema, and retropharyngeal abscess, all requiring management with a consultant. Chronic stridor in infancy most often represents laryngomalacia, a developmental abnormality of the laryngeal cartilage which usually resolves by the second year of life and rarely requires specific treatment. Other causes of chronic stridor in childhood include subglottic hemangioma, vocal cord paralysis, and a long list of abnormalities. In the older child with chronic stridor or in the infant whose clinical picture is unusual for laryngomalacia, airway roentgenograms, barium studies, or laryngoscopy/bronchoscopy should be obtained to establish the definitive diagnosis.

Ultrasonic and jet aerosolization of phospholipids and the effects on surface activity

Surface active aerosols were produced from aqueous dispersions of mixed lipids (CLL), extracted from bovine lung lavage. Particle size distributions were measured as a function of humidity for two types of aerosol generators: ultrasonic and jet. Lipid dispersions before aerosolization were prepared by sonication in an ice bath and by mechanical vortexing. Over a range of high humidity greater than 60-70%, ultrasonic nebulization gave CLL aerosols with mass median aerodynamic diameters (MMAD) of 1.4 +/- 0.1 micron, compatible with predicted alveolar deposition fractions of 0.2-0.3 according to current deposition models. For humidities of 30-95%, jet nebulization gave MMAD values of 0.4-0.5 micron, which have lower predicted alveolar deposition. The surface pressure-time (pi - t) adsorption characteristics at 35 +/- 2 degrees C of CLL dispersions prepared initially by vortexing or sonication were not significantly affected by ultrasonic nebulization over a 1-2 h time period. In addition, the dynamic surface tension lowering of both kinds of CLL dispersion was not affected by ultrasonic nebulization (minimum surface tension less than 1 dyne/cm at 37 degrees C and 100% humidity). Current interest in the treatment of the respiratory distress syndrome (RDS) with exogenous surfactant replacement has focused largely on the delivery of surfactant replacement has focused largely on h delivery of surfactants to infants by tracheal instillation at birth. However, the ability to form multi-component surfactant aerosols with appreciable alveolar deposition fractions and high surface activity may help to expand the utility of replacement therapy to patients with aerated lungs.

Aerosolized ribavirin treatment of infants with respiratory syncytial viral infection. A randomized double-blind study

We evaluated a new antiviral agent, ribavirin, in the treatment of infants hospitalized with lower-respiratory-tract disease from respiratory syncytial virus. Ribavirin or placebo was administered to 33 infants in a double-blind manner by continuous aerosol for three to six days. Seventeen infants were treated with placebo, and 16 with ribavirin. By the end of treatment, infants receiving ribavirin had significantly greater improvement in their overall score for severity of illness, in lower-respiratory-tract signs, and in arterial oxygen saturation. Viral shedding was also diminished in the treated groups as compared with the placebo group. No side effects or toxicity were associated with the aerosol therapy. Isolates of respiratory syncytial virus obtained from the infants over the course of therapy showed no change in sensitivity to ribavirin.

Lung growth and airway function after lobectomy in infancy for congenital lobar emphysema

To characterize the outcome of lobectomy in infancy and the low expiratory flows which persist after lobectomy for congenital lobar emphysema, 15 subjects with this history were studied at age 8-30 yr. Total lung capacity was normal in all, but higher values (P < 0.05) were observed in nine subjects with upper lobectomy than in five subjects with right middle lobectomy. Ratio of residual volume to total lung capacity was correlated (P < 0.05) with the amount of lung missing as estimated from normal relative weights of the respective lobes. Xe(133) radiospirometry in eight subjects showed that the operated and unoperated sides had nearly equal volumes at total lung capacity, but that the operated side was larger than the unoperated side at residual volume. Perfusion was equally distributed between the two sides. Similar findings were detected radiographically in four other subjects. Forced expiratory volume in 1 s and maximal midexpiratory flow rate averaged 72 and 45% of predicted, respectively. Low values of specific airway conductance and normal density dependence of maximal flows in 12 subjects suggested that obstruction was not limited to peripheral airways. Pathologic observations at the time of surgery and morphometry of the resected lobes were not correlated with any test of pulmonary function. These data show that lung volume can be completely recovered after lobectomy for congenital lobar emphysema in infancy. The volume increase occurs on the operated side, and probably represents tissue growth rather than simple distension. The response to resection is influenced by the particular lobe resected and may be associated with decreased lung recoil near residual volume. Low expiratory flows in these subjects could be explained by several mechanisms, among which a disproportion between airway and parenchymal growth in infancy (dysanaptic growth) is most compatible with our data.