Britt T. Skadberg

Pulmonary outcome in adolescents of extreme preterm birth: a regional cohort study

Aims: The pulmonary outcome of extreme prematurity remains to be established in adults. We determined respiratory health and lung function status in a population‐based, complete cohort of young preterms approaching adulthood. Methods. Forty‐six preterms with gestational age ±28 wk or birthweight ±1000g, born between 1982 and 1985, were compared to the temporally nearest term‐born subject of equal gender. Spirometry, plethysmography, reversibility test to salbutamol and methacholine bronchial provocation test were performed. Neonatal data were obtained from hospital records and current symptoms from validated questionnaires. Results: When entering the study at a mean age of 17.7 (SD: 1.2) y, a doctors diagnosis of asthma and use of asthma inhalers were significantly more prevalent among preterms than controls (one asthmatic control compared to nine preterms, all but one using asthma inhalers). Peak expiratory flow (PEF) and forced expiratory volume in 1 s (FEV1) were decreased and the discrepancies relative to controls increased parallel to increased severity of neonatal lung disease. Parameters of increased neonatal oxygen exposure significantly predicted FEV1. Adjusted for height, gender and age, FEV1 was reduced by a mean of 580 ml/s in subjects with a history of bronchopulmonary dysplasia. Fifty‐six percent of preterms had a positive methacholine provocation test compared to 26% of controls.

Continuous Laryngoscopy Exercise Test: A Method for Visualizing Laryngeal Dysfunction during Exercise

Objectives/Hypothesis: To assess the diagnostic feasibility and patient acceptance of a new developed diagnostic test for exercise induced upper airway flow limitation.

Sleeping position and sudden infant death syndrome (SIDS): effect of an intervention programme to avoid prone sleeping.

The proportion of prone sleeping among sudden infant death syndrome (SIDS) victims and infants in general, and the rate of SIDS were prospectively studied in the county of Hordaland, Norway, three years before (1987–89) and three years after (1990–92) a campaign to discourage prone sleeping. Before the campaign, 64% of random reference infants were put prone versus 8% after (p < 0.0001). Concurrently, the rate of SIDS decreased from 3.5 to 1.6 per 1000 live births (63 infants before and 30 after the campaign,p= 0.0002). Prone sleeping was not considered a statistically significant risk factor for SIDS before (OR 2.0,95% CI 0.8–4.5), but was highly significant (OR 11.3,95% CI 3.6–36.5) after the campaign. Prone sleeping is an important risk factor for SIDS, but the association may be missed in epidemiological studies if prone is the predominant sleeping position. Behaviour with regard to sleeping position may be changed rapidly by means of a simple campaign.

Characteristics of asthma and airway hyper‐responsiveness after premature birth

Asthma‐like symptoms and airway hyper‐responsiveness (AHR) are frequently reported in children subsequent to premature birth and bronchopulmonary dysplasia (BPD). There is limited knowledge on the mechanisms underlying these respiratory manifestations. Generally, childhood asthma and AHR is described within a context of inheritance, allergy and eosinophilic airway inflammation, and often in relation to cigarette exposures. We investigated these factors in relation to current asthma and AHR in a population‐based cohort of 81 young people, born with gestational age ≤28 wk or birth weight ≤1000 g, and in a matched term‐born control population. In the pre‐term population, asthma and AHR were additionally studied in relation to neonatal respiratory morbidity. At follow up, more pre‐term than control subjects had asthma. Forced expiratory volume in first second (FEV1) was reduced, AHR was substantially increased, and the level of the urinary leukotriene metabolite E4 (U‐LTE4) was increased in the pre‐term population compared to the term‐born. In control subjects, asthma and AHR was associated with a pattern consistent with inheritance, allergy, airway inflammation, and cigarette exposures. In the pre‐terms, asthma and AHR was either unrelated or less related to these factors. Instead, AHR was strongly related to a neonatal history of BPD and prolonged requirement for oxygen treatment. In conclusion, asthma and AHR subsequent to extremely premature birth differed from typical childhood asthma with respect to important features, and AHR was best explained by neonatal variables. These respiratory manifestations thus seem to represent a separate clinical entity.

Behaviour and physiological responses during prone and supine sleep in early infancy

AIMS To study the effect of prone and supine sleep on infant behaviour, peripheral skin temperature, and cardiorespiratory parameters to aid understanding of why prone sleeping is associated with an increased risk of sudden infant death syndrome. METHODS Of 33 enrolled infants, 32 were studied at 2.5 and 28 at 5 months of age. A computer aided multichannel system was used for polysomnographic recordings. Behaviour was charted separately. RESULTS Prone REM (active) sleep was associated with lower frequencies of short arousals, body movements and sighs, and a shorter duration of apnoeas than supine REM sleep at both ages. At 2.5 months there were less frequent episodes of periodic breathing during prone sleep in non-REM (quiet) and REM sleep. Heart rate and peripheral skin temperature were higher in the prone position during both sleep states at both ages. CONCLUSIONS The observation of decreased variation in behaviour and respiratory pattern, increased heart rate, and increased peripheral skin temperature during prone compared with supine sleep may indicate that young infants are less able to maintain adequate respiratory and metabolic homoeostasis during prone sleep.

Exercise induced dyspnea in the young. Larynx as the bottleneck of the airways.

BACKGROUND Exercise induced asthma may symptomatically be difficult to differentiate from exercise related obstruction in the upper airways, sometimes leading to diagnostic confusion and inappropriate treatment. Larynx accounts for a significant fraction of total airway resistance, but its role as a limiting factor for airflow during exercise has been hampered by lack of diagnostic tools. We aimed to study laryngeal function in exercising humans by transnasal laryngoscopy. METHODS Continuous video recording of the larynx was performed in parallel with continuous film recording of the upper part of the body and recording of breath sounds in subjects running to respiratory distress or exhaustion on a treadmill. RESULTS A successful examination was obtained in 20 asymptomatic volunteers and 151 (91%) of 166 young patients with a history of inspiratory distress or stridor during exercise. At rest, six patients had abnormal laryngeal findings. During exercise, a moderate or severe adduction of laryngeal structures was observed in parallel with increasing inspiratory distress in 113 (75%) patients. In 109 of these, adduction started within supraglottic structures, followed by adduction of the vocal cords in 88. In four patients, laryngeal adduction started in the vocal cords, involving supraglottic structures secondarily in three. CONCLUSION Larynx can safely be studied throughout a maximum intensity exercise treadmill test. A characteristic laryngeal response pattern to exercise was visualised in a large proportion of patients with suspected upper airway obstruction. Laryngoscopy during ongoing symptoms is recommended for proper assessment of these patients.

Better care of immature infants; has it influenced long-term pulmonary outcome?

AIMS To assess whether lung function in late childhood had improved in subjects born extremely prematurely in the early 1990s compared to the early 1980s, and whether neonatal factors in the respective periods had different impact on long-term pulmonary outcome. DESIGN Population-based, controlled cohort study. Lung function was determined in 81 of 86 (94%) eligible subjects born with gestational age < or =28 weeks or birthweight < or =1000 g in Western Norway in 1982-85 (n=46) and 1991-92 (n=35), and in 81 matched control subjects born at term. RESULTS The incidence of bronchopulmonary dysplasia was similar in the two periods. At follow-up, airway obstruction, hyper-responsiveness and pulmonary hyperinflation were similarly increased in both preterm cohorts compared to matched controls. Furthermore, current lung function was similarly related to neonatal respiratory disease in both birth-cohorts: FEV1 was reduced with respectively 18.6% and 18.7% of predicted in preterms dependent on supplemental oxygen at 36 weeks postmenstrual age. Lack of antenatal treatment with corticosteroids and prolonged neonatal oxygen treatment predicted similar significant airway obstruction in the two birth-cohorts. CONCLUSION Preterms born in different eras of neonatology had similar long-term decreases in lung function. Long periods of oxygen supplementation are still required to salvage immature infants, and airway obstruction may still be a common long-term outcome.

Assessment of lung volumes in children and adolescents: comparison of two plethysmographic techniques

Thoracic gas volume (Vtg) can be measured with body plethysmography by either repetitive panting or one single inspiratory effort against a shutter occluding the airways. The panting technique is preferred, but may be demanding. We aimed to assess the precision of these two methods and the degree of agreement between them. Vtg and functional residual capacity (FRC) were measured in 155 subjects with a standard, commercially available plethysmograph, acting as a variable‐pressure, constant‐volume device when Vtg is determined. Total lung capacity (TLC) and residual lung volume (RV) were calculated subsequent to a full vital capacity manoeuvre. For non‐asthmatic healthy subjects, the standard deviations (SD) of the differences between two replicate measurements of FRC, TLC and RV were respectively 0·16, 0·13 and 0·14 litres with the panting technique, and 0·18, 0·18 and 0·23 litres with the single inspiratory effort technique. In percentage of the respective lung volumes, the corresponding 1·96 SDs were 20%, 8% and 40% with the panting technique and 23%, 12% and 67% with the single inspiratory effort technique. Between the two techniques, 95% limits of agreement were 21% for FRC, 11% for TLC and 58% for RV. The variability of Vtg and FRC accounted for most of the variability of TLC and RV. In conclusion, the panting and the single inspiratory effort technique produced results that were comparable in magnitude, however with a better precision with the panting technique. The single inspiratory effort technique can be used as an alternative if the panting technique fails.

Noninvasive treatment of bronchomalacia, successful ventilation of a severely ill infant

Noninvasive treatment of bronchomalacia. Successful ventilation of a severely ill infant.

In Reference to Continuous Laryngoscopy Exercise Test: A Method for Visualizing Laryngeal Dysfunction During Exercise

the interpretation of dynamic hyperinflation in this instance is erroneous, and results from failure of the fundamental assumption underlying the analysis of exercise flow-volume data. The placement of the tidal flow-volume loop in the correct position relative to total lung volume is the most challenging aspect of this. It is accomplished by having the subject periodically perform maximal inspiratory capacity maneuvers during the exercise test, beginning from spontaneous end-expiratory volume. The necessary assumption is that on each inspiratory capacity maneuver the patient attains the same total lung volume that was attained at baseline. If, and only if, this assumption is true, a decrease in inspiratory capacity can be interpreted as evidence of increased end-expiratory lung volume. Although this assumption seems to be valid for patients with COPD, it may not be for patients experiencing inspiratory airflow obstruction. The reduced inspiratory capacities observed in Heimdal et al.’s patients during exercise probably result from truncation of inspiration at a submaximal lung volume, rather than an increase in end-expiratory volume. Unlike COPD, for patients with laryngeal dysfunction there would be no offsetting advantage to the changes in breathing mechanics resulting from dynamic hyperinflation, so the overloading of inspiratory muscles by the shift in lung volumes would be counterproductive. It thus seems unlikely that dynamic hyperinflation would occur in this setting. Definitive demonstration of the cause of the fall in inspiratory capacity observed in these patients during exercise would require an independent measure of lung volume (e.g., such as reported by Gorgiadou et al.5). In the absence of such data, interpretation of the inspiratory capacity results should be made with caution. Manufacturers of exercise testing equipment often provide software that makes it easy to generate plots of flow-volume loops, but users need to be aware of the underlying assumptions and limitations in their analysis and interpretation.