Relationship between lung function results in the first year of life and respiratory morbidity in early childhood in patients born prematurely

Fatores associados à morbidade respiratória entre 12 e 36 meses de vida de crianças nascidas de muito baixo peso oriundas de uma UTI neonatal pública

O objetivo do estudo foi estimar a morbidade respiratória entre 12 e 36 meses em crianças prematuras e identificar os fatores associados. A população compreendeu 84 crianças de uma coorte de prematuros de muito baixo peso. O desfecho foi a taxa de incidência de morbidade respiratória. A associação entre as variáveis independentes e morbidade respiratória foi verificada por modelo linear generalizado. Entre 12 e 24 meses, 56,3% das crianças apresentaram morbidade respiratória. Entre 24 e 36 meses, 38,1% das crianças foram acometidas. As variáveis associadas à morbidade respiratória foram: displasia broncopulmonar (RT = 1,9; IC95%: 1,2-2,9), complacência pulmonar alterada (RT = 1,6; IC95%: 1,1-2,2), pneumonia neonatal (RT = 2,8; IC95%: 2,0-4,0), persistência do canal arterial (RT = 1,6; IC95%: 1,1-2,4) e morbidade respiratória no primeiro ano de vida (RT = 1,8; IC95%: 1,3-2,6). A incidência de morbidade respiratória entre 12 e 36 meses se manteve elevada neste grupo de crianças de alto risco, o que reforça a necessidade de acompanhamento e de intervenções efetivas na prevenção do adoecimento e na melhora da qualidade de vida destas crianças e suas famílias.

Asthma

Asthma has been recognized as a disease since the earliest times. In the Corpus Hippocraticum, Hippocrates used the term “ασθμα” to indicate any form of breathing difficulty manifesting itself by panting. Aretaeus of Cappadocia, a well-known Greek physician (second century A.D.), is credited with providing the first detailed description of an asthma attack [13], and to Celsus it was a disease with wheezing and noisy, violent breathing. In the history of Rome, we find many members of the Julio-Claudian family affected with probable atopic respiratory disorders: Caesar Augustus suffered from bronchoconstriction, seasonal rhinitis as well as a highly pruritic skin disease. Claudius suffered from rhinoconjunctivitis and Britannicus was allergic to horse dander [529]. Maimonides (1136–1204) warned that to neglect treatment of asthma could prove fatal, whereas until the 19th century, European scholars defined it as “nervous asthma,” a term that was given to mean a defect of conductivity of the ninth pair of cranial nerves.

Lung function in prematurely born infants after viral lower respiratory tract infections

BACKGROUND

Chronic respiratory morbidity has been reported in prematurely born infants after respiratory syncytial virus (RSV) and human metapneumovirus (hMPV) lower respiratory tract infections (LRTIs). The aim of this study was to determine the impact of viral LRTI on lung function at follow-up of prematurely born infants.

METHODS

Fifty-nine infants born before 32 weeks of gestational age were prospectively followed after neonatal unit discharge. Nasopharyngeal aspirates were obtained when the infants developed LRTIs in hospital or the community. RSV was identified by immunofluorescence and/or culture. In addition, RSV and other viral infections were identified by real time reverse transcription polymerase chain reaction. At a corrected age of 1 year, measurements of lung volume [functional residual capacity (FRC)pleth] and airway resistance (R(aw)) were made by plethysmography, and lung volume was also assessed by helium gas dilution (FRC(He)). Before the measurements, parents completed diary cards for 1 month documenting on a daily basis whether their infant wheezed, coughed, or required bronchodilator therapy.

RESULTS

Twenty-five infants had at least 1 proven RSV LRTI (RSV-positive group). The RSV-positive group compared with the rest of the cohort had similar lung volumes, but significantly higher R(aw) (P = 0.002), more days of wheeze (P < 0.001), and bronchodilator requirement (P = 0.027). Regression analysis also identified that hMPV LRTI was associated with elevated airways resistance at follow-up.

CONCLUSION

RSV and hMPV LRTIs in prematurely born infants are associated with abnormal lung function at follow-up.

Lung function and exhaled nitric oxide levels in infants developing chronic lung disease

Chronic lung disease (CLD) is a common outcome of neonatal intensive care. To determine whether the results of serial exhaled nitric oxide (eNO) measurements during the perinatal period differed between infants who did and did not develop CLD. In addition, we wished to assess whether eNO results were more predictive of CLD development than lung function test results or readily available clinical data (gestational age and birthweight). The patients were 24 infants with a median gestational age of 27 (range 25-31) weeks. Measurements of eNO levels, functional residual capacity (FRC), and compliance of the respiratory system (CRS) were attempted on postnatal days 1, 3, 5, 7, 14, and 28 days. The 12 infants who developed CLD were of significantly lower birthweight and gestational age than the rest of the cohort; in addition, they had lower median FRC (P < 0.02) and CRS (P < 0.02) results, but not higher eNO levels, in the first week after birth. Construction of receiver operator characteristic (ROC) curves demonstrated that the CRS and FRC results on Day 3 were the best predictors of CLD development; the areas under the ROC curves were 0.94 and 0.91, respectively. Early lung function test results, but not eNO levels, are useful in predicting CLD development, but are not significantly better than birthweight.

Randomised trial of high frequency oscillatory ventilation or conventional ventilation in babies of gestational age 28 weeks or less: respiratory and neurological outcomes at 2 years

BACKGROUND

The long term outcome of children entered into neonatal trials of high frequency oscillatory ventilation (HFOV) or conventional ventilation (CV) has been rarely studied.

OBJECTIVE

To evaluate respiratory and neurodevelopmental outcomes for children entered into the United Kingdom Oscillation Study, which was designed to evaluate these outcomes.

METHODS

Surviving infants were followed until 2 years of age corrected for prematurity. Study forms were completed by local paediatricians at routine assessments, and parents were asked to complete a validated neurodevelopmental questionnaire.

RESULTS

Paediatricians' forms were returned for 73% of the 585 surviving infants. Respiratory symptoms were common in all infants, and 41% had received inhaled medication. Mode of ventilation had no effect on frequency of any symptoms. At 24 months of age, severe neurodevelopmental disability was present in 9% and other disabilities in 38% of children, but the prevalence of disability was similar in children who received HFOV or CV (relative risk 0.93; 95% confidence interval 0.74 to 1.16). The prevalence of disability did not vary by gestational age, but boys were more likely to have overall disability. Developmental scores were unaffected by mode of ventilation (relative risk 1.13; 95% confidence interval 0.78 to 1.63) and were lower in infants born before 26 weeks gestation compared with babies born at 26-28 weeks.

CONCLUSIONS

Initial mode of ventilation in very preterm infants has no impact on respiratory or neurodevelopmental morbidity at 2 years. HFOV and CV appear equally effective for the early treatment of respiratory distress syndrome.

Respiratory function of very prematurely born infants at follow up: influence of sex

OBJECTIVE

To test the hypothesis that male compared with female prematurely born infants would have worse lung function at follow up.

DESIGN

Prospective follow up study.

SETTING

Tertiary neonatal intensive care units

PATIENTS

Seventy six infants, mean (SD) gestational age 26.4 (1.5) weeks, from the United Kingdom oscillation study.

INTERVENTIONS

Lung function measurements at a corrected age of 1 year.

MAIN OUTCOME MEASURES

Airways resistance (Raw) and functional residual capacity (FRC(pleth)) measured by whole body plethysmography, specific conductance (sGaw) calculated from Raw and FRC(pleth), and FRC measured by a helium gas dilution technique (FRC(He)).

RESULTS

The 42 male infants differed significantly from the 34 female infants in having a lower birth weight for gestation, requiring more days of ventilation, and a greater proportion being oxygen dependent at 36 weeks postmenstrual age and discharge. Furthermore, mean Raw and FRC(pleth) were significantly higher and mean sGaw significantly lower. After adjustment for birth and current size differences, the sex differences in FRC(pleth) and sGaw were 15% and 26% respectively and remained significant.

CONCLUSION

Lung function at follow up of prematurely born infants is influenced by sex.

Neonatal risk factors for respiratory morbidity during the first year of life among premature infants

CONTEXT AND OBJECTIVE

There have been dramatic increases in very low birth weight infant survival. However, respiratory morbidity remains problematic. The aim here was to verify associations between pulmonary mechanics, pulmonary structural abnormalities and respiratory morbidity during the first year of life.

DESIGN AND SETTING

Prospective cohort study at Instituto Fernandes Figueira, Fundação Oswaldo Cruz, Rio de Janeiro.

METHODS

Premature infants with birth weight < 1500 g were studied. Lung function tests and high-resolution chest tomography were performed before discharge. During the first year, infants were assessed for respiratory morbidity (obstructive airways, pneumonia or hospitalization). Neonatal lung tests and chest tomography and covariables potentially associated with respiratory morbidity were independently assessed using relative risk (RR). RR was subsequently adjusted via logistic regression.

RESULTS

Ninety-seven newborn infants (mean birth weight: 1113 g; mean gestational age: 28 weeks) were assessed. Lung compliance and lung resistance were abnormal in 40% and 59%. Tomography abnormalities were found in 72%; respiratory morbidity in 53%. Bivariate analysis showed respiratory morbidity associated with: mechanical ventilation, prolonged oxygen use (beyond 28 days), oxygen use at 36 weeks, respiratory distress syndrome, neonatal pneumonia and patent ductus arteriosus. Multivariate analysis gave RR 2.7 (confidence interval: 0.7-10.0) for simultaneous lung compliance and chest tomography abnormalities. Adjusted RR for neonatal pneumonia and mechanical ventilation were greater.

CONCLUSIONS

Upon discharge, there were high rates of lung mechanism and tomography abnormalities. More than 50% presented respiratory morbidity during the first year. Neonatal pneumonia and mechanical ventilation use were statistically significant risk factors.

Chronic manifestations of respiratory syncytial virus infection in premature infants

BACKGROUND

Respiratory syncytial virus (RSV) infection in healthy infants born at term results in long term sequelae. Infants born prematurely are at increased risk of severe acute RSV infection; thus it would seem likely that such infants would be at increased risk of long term respiratory sequelae.

METHODS

Methods of assessing the long term outcome of RSV infection are discussed and the results of retrospective and prospective studies investigating chronic respiratory morbidity after RSV infection in premature infants are reviewed.

RESULTS

Documentation of all health care utilization, parental documentation of symptom status and lung function measurement provide a comprehensive and quantitative assessment of respiratory outcome. Studies that have included such outcome measures have demonstrated that RSV hospitalization in infants born between 32 and 35 weeks of gestational age and in those born more prematurely who developed chronic lung disease was associated with more hospital admissions, inpatient days, physician contacts and outpatient visits in the first 2 years after birth. Children born before 32 weeks of gestation who developed chronic lung disease also required more outpatient attendances and prescriptions and respiratory medications in years 2 through 4. Prospective data collection has demonstrated that chronic respiratory morbidity occurs in very premature infants, regardless of whether their RSV infection required hospitalization.

CONCLUSION

Chronic respiratory morbidity is increased in premature infants after RSV infection. The duration of this increased morbidity and the impact of other viral infections, particularly dual infection with RSV, on long term sequelae merit investigation.

Assessment of prematurely born children at follow-up using a tidal breathing parameter

Prematurely born children frequently have respiratory problems at follow-up. A non-invasive and easily performed lung function test would greatly facilitate their evaluation and appropriate treatment. We have, therefore, assessed whether the shape of the tidal breathing expiratory flow curve would give useful information in such a population. One hundred and twenty traces were randomly selected from plethysmographic measurements of thoracic gas volume and airway resistance made during a follow-up study of a prematurely born population. The children had a median gestational age of 29 (range 23-35, interquartile range 27-31) weeks and postnatal age at the time of measurement of 11 (range 6-24, interquartile range 7-13) months. From the flow and volume signals, the mean time to reach peak tidal expiratory flow as a proportion of the total expiratory time (tPTEF : tE) was determined for each child. The median tPTEF : tE differed significantly between children who, in the neonatal period, had or had not required mechanical ventilation (p < 0.001) and had or had not had an increased inspired oxygen requirement (p < 0.01), and who were or were not symptomatic at follow-up (p < 0.001). Logistic regression analysis demonstrated that a low tPTEF : tE ratio was independently associated with symptom status. These results suggest that assessment of a tidal breathing parameter during follow-up of prematurely born children may be useful. As tPTEF : tE can be measured without sedation, relatively quickly and with simple equipment, potentially large study populations could be investigated, and this technique should now be evaluated in a non-sedated group of young prematurely born children.

Respiratory morbidity in preschool children born prematurely. Relationship to adverse neonatal events

Respiratory morbidity, recurrent cough and/or wheeze and lung function abnormalities are common even outside infancy in preschool children born prematurely. Throughout the first 5 years of life, adverse neonatal events such as immaturity at birth and a requirement for prolonged respiratory support are significantly associated with positive symptom status. In the older preschool child, however, there is some evidence to suggest that other factors, such as a family history of atopy, may be equally important. The development of recurrent symptoms even at 4 years of age can be predicted accurately from the results of lung function measurements made in infancy, and hopefully such data will facilitate the introduction of effective intervention strategies. Lung function abnormalities are more marked in symptomatic patients and, in older children, seem to reflect increased airway responsiveness rather than having a significant relationship to adverse neonatal events. The hospital readmission rate for respiratory disorders, however, is certainly adversely affected by extremely low birthweight and neonatal chronic lung disease, as well as current symptom status. These data highlight that strategies to reduce extremely premature delivery and its consequences should favourably influence respiratory morbidity in preschool children.

Respiratory illness in families of preterm infants with chronic lung disease

AIMS--To examine the relation, based on two types of questionnaires, between (1) chronic lung disease of the newborn (CLDN) and lower respiratory illness (LRI) in siblings, and between (2) CLDN and asthma, chronic obstruction pulmonary disease (COPD), or allergy in parents and grandparents. METHODS--Data from 209 children born before 32 weeks of gestation were randomly taken from the records of three neonatal units. Taking into account age and gender, the excess of LRI was calculated for each family compared with the average of all families. Subsequently whether CLDN was associated with an excess of LRI in the family was tested. RESULTS--Thirty one (14.8%) children were diagnosed as having CLDN. The family probability index for LRI did not differ between children with or without CLDN. The prevalence of COPD, asthma, and allergy in parents of children with CLDN was similar to that of children without CLDN. The prevalence of LRI was 18.1% in study children, 29.6% in children with CLDN, and 16.9% in children without CLDN (P < 0.01). These prevalences were higher compared with that of a group of term siblings (9.3%) (P = 0.05). CONCLUSIONS--These findings suggest that CLDN in preterm children is not related to a genetic or familial predisposition towards asthma, COPD, or allergy.