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Biomedical subjects

C S Beardsmore

Publications and source records attributed to C S Beardsmore.

At least 19 recordsLinked to original sources
PubMed2000

Effect of maternal smoking on ventilatory responses to changes in inspired oxygen levels in infants.

Maternal smoking is a major independent risk factor for sudden infant death syndrome (SIDS). Respiratory control deficits have been implicated in SIDS. The aim of this study was to test the hypothesis that infants born to smoking mothers have reduced ventilatory responses to changes in inspired oxygen. Smoking and nonsmoking women were recruited in midpregnancy and smoking status confirmed by measurement of urinary cotinine. To control for confounding factors of smoking each mother-infant pair in the smoking group was matched to a pair in the nonsmoking group for social class, maternal age and parity, feeding, birthweight, gestational age, and infant sex. Infants were seen overnight at approximately 10 wk of age for tests of respiratory control, using the alternating breath test. Ventilation was measured by respiratory inductance plethysmography and inspired and end-tidal oxygen levels were determined by mass spectrometry. Data were obtained from 40 infants (17 in the smoking group). Responses were similar in both groups for 10 respiratory parameters including respiratory drive and timing, and there were no significant differences. The mean end-tidal oxygen level when 40% O(2) was delivered was an average of 1.13% higher in the smoking group (p = 0.0067), although the inspired oxygen levels were not different. In conclusion, we did not find an independent effect of maternal smoking on respiratory control. The differences in end-tidal oxygen levels during the alternating breath test may represent differences in alveolar ventilation.

Female↗
PubMed1999

Nasal flow limitation in children.

Nasal congestion due to the common cold may be exacerbated in small children because of their small nasal passages. Our aims were 1) to test the hypothesis that smaller children have relatively larger nasal airways compared to the intrathoracic airways, and 2) to examine the effect of stenting and a decongestant on nasal patency and nasal flow. During oral forced vital capacity (FVC) maneuvers, expiratory flow is limited by intrathoracic airways. During nasal FVC, flow at high volumes is limited by the nose. The point where the nasal flow-volume curve becomes superimposable on the oral curve (%Sup) depends on the relative resistance of nasal and intrathoracic airways. Fifty-four healthy children (28 male), median age 9.5 years (range 5.9-16.0), performed full forced respiratory maneuvers through: 1) the mouth, 2) the nose, 3) the nose after application of an external stent (Breathe Right (BR) strip), and 4) the nose following instillation of xylometazoline. Peak inspiratory and expiratory flow (PIF and PEF), and mid-inspiratory and expiratory flow (MIF50 and MEF50) all showed a significant decrease from the oral to the nasal baseline maneuver. Mean (SD) %Sup of the nasal baseline was 35.6 (13.7)% and was unrelated to height. PIF and MIF50 increased with the BR strip (P < 0.05). Xylometazoline also caused a significant increase in all measured flows (P < 0.05). Mean (SD) %Sup of the nasal maneuver after application of xylometazoline increased to 53.3 (14.0)%. We conclude that there is no evidence that relative resistance of nasal and intrathoracic airways change with height. The %Sup is easy to obtain and may prove a useful index of nasal patency.

Administration, Intranasal↗
PubMed1999

Respiratory function in childhood following repair of oesophageal atresia and tracheoesophageal fistula.

AIM: To determine the relation between respiratory function in infancy and at school age in children who have undergone oesophageal atresia and tracheoesophageal fistula repair, and assess the value of infant respiratory function testing; and to examine the effect of bronchodilators. METHOD: Fourteen children (6 girls, and 8 boys) who had undergone respiratory function testing in infancy were retested at school age (7-12 years). Measurements included lung volume, airways resistance, peak flow, and spirometry. Clinical problems were investigated by questionnaire. Twelve children had repeat measurements after taking salbutamol. RESULTS: Predominant complaints were non-productive cough and dysphagia, but even those children with major problems in infancy reported few restrictions at school or in sport or social activities. Respiratory function and clinical findings at school age appeared unrelated to status in infancy, such that even the patients with severe tracheomalacia requiring aortopexy did not have lung function testing suggestive of malacia at school age. Most patients showed a restrictive pattern of lung volume which would appear to result from reduced lung growth after surgery rather than being a concomitant feature of the primary congenital abnormality. Although six children reported wheeze and four had a diagnosis of asthma, only one responded to salbutamol. This suggests that a tendency to attribute all lower respiratory symptoms to asthma may have led to an overdiagnosis of this condition in this patient group. CONCLUSION: Respiratory function testing in infancy is of limited value in medium term prognosis, but may aid management of contemporary clinical signs. In children respiratory function testing is valuable in assessing suspected asthma and effects of bronchodilators.

Albuterol↗
PubMed1996

Respiratory responses to rapid-onset, repetitive vs. continuous hypoxia in piglets.

Repeated, frequent hypoxic exposures may precede Sudden Infant Death. This study assessed whether such hypoxic modality, vs. continuous hypoxia, compromised compensatory cardiorespiratory responses. Following aseptic, chronic instrumentation, 10 to 20 day-old, unsedated piglets underwent measurements of arterial O2 saturation, pH and gas tensions, respiration, heart rate, physical activity, O2 consumption and rectal temperature on several experimental days. The piglets were exposed to 21 min of either 10% or 6% O2 in N2, each comprising either seven, 3-min exposures alternating with 3-min intervals in 21% O2 balance N2, or 7 consecutive hypoxic exposures. Responses to 6% hypoxia were greater than those to 10% hypoxia. In 10% hypoxia, responses to repetitive vs. continuous exposure differed only in PaCO2. In 6% hypoxia, repetitive vs. continuous exposure resulted in lower respiratory frequency (p < 0.05) and in lower ventilation equivalent (p = 0.07) despite higher activity levels. Thus, the mode of hypoxic exposure determines the extent of the respiratory response: Severe, repetitive hypoxia mitigates protective respiratory responses when compared to equivalent, but sustained hypoxia.

Animals↗
PubMed1996

The effect of sleep deprivation on sleep states, breathing events, peripheral chemoresponsiveness and arousal propensity in healthy 3 month old infants.

We wished to investigate the effects of sleep deprivation on sleep, arousal propensity, respiratory events and peripheral chemoresponses in healthy infants, since these effects might be relevant to mechanisms concerned with some cases of sudden infant death syndrome. Paired observations were made overnight during natural sleep and following sleep deprivation, in a randomized fashion, in 15 healthy infants aged 78 (7) days (mean (SD)). Polysomnograms were recorded and sleep was scored using Anders' criteria. Respiratory events were categorized into central, mixed and obstructive apnoeas. Peripheral chemoresponses were measured during quiet sleep from the respiratory response to two-breath alternations in fractional inspiratory oxygen (F1, O2) (0.42 and 0.00). Arousal propensity was determined from awakening and arousal thresholds to graded photic and auditory stimuli during quiet sleep, and from spontaneous awakenings and limb movements. Compared with natural sleep, following sleep deprivation infants maintained a greater proportion of quiet sleep (39 vs 44%). There was no measurable change in arousal propensity. During quiet sleep, obstructed breathing events tended to be more common after sleep deprivation (0.1 vs 0 events.h-1) and the expiratory time during baseline breathing increased significantly (1.27 vs 1.58 s) although the decrease in respiratory rate was not significant (32 vs 30 breaths.min-1). Peripheral chemoresponses altered significantly, alternations in tidal volume/inspiratory time (VT/tI) as a measure of inspiratory drive increased after sleep deprivation (9 vs 21%). In conclusion, following short-term sleep deprivation in infancy, respiratory control alters, peripheral chemoresponsiveness increases in magnitude and the timing of baseline breathing alters, without any detectable alteration in arousal propensity. This state may be associated with an increased vulnerability to obstructive respiratory events.

Arousal↗
PubMed1996

Peripheral chemoresponses of infants measured by a minimally invasive method utilizing two-breath alternations in Fl,02.

The aim of this study was to develop a minimally invasive and reliable method for measuring peripheral chemoresponsiveness to oxygen in infants, and to establish baseline data from normal infants at 12 weeks of age. Two-breath alternations in fractional inspired oxygen (FI,O2), switching between 0.42 to 0.00 were given for 2 min periods via a face mask (held close to the face but without contact) to 18 healthy infants during quiet sleep. End-tidal oxygen concentrations alternated between 21 and 11%. Instantaneous minute ventilation (V'E) and its components tidal volume (VT), respiratory frequency (fR) inspiratory and expiratory times (tI and tE), inspiratory flow (VT/tT), and inspiratory duty cycle (tI/ttot) were measured by respiratory inductance plethysmography. Two-breath alternations in each of the ventilatory components were matched with the corresponding alternating end-tidal oxygen record and compared with contiguous pre- and post-test data obtained in control periods of air breathing. Alternations in all ventilatory components except fR changed significantly during FI,O2 alternations; VT 26%, tE-8%, VT/tI 18%, tI/ttot 11% and V'E 28% of baseline values. Within and between infant variances are reported for the individual components of ventilation. Differences among infants were best detected by alternations in V'E; within infant variance 76, between infant variance 171. We conclude that the test described is a safe, reliable and relatively easily applied method of measuring peripheral chemoresponsiveness, which is suitable for clinical application in infancy.

Analysis of Variance↗
PubMed1996

Electrocorticographic activity during repeated vs continuous hypoxia in piglets.

To assess the effects on brain activity of repeated vs continuous hypoxia, 16, 10- to 22-day-old piglets were instrumented chronically for electrocortical and arterial pH and gas tension measurements. They inhaled 10% or 6% O2 in N2 for 21 min, either continuously, or during seven, 3 min exposures interrupted by 3 min recovery periods in air, all while behaving naturally within a sealed, temperature controlled, plexiglass box. An isoelectric electrocorticogram (ECoG) and/or seizures, related to the onset of hypoxia, occurred repeatedly in 6 of the 10 exposures to 6% repetitive hypoxia, only twice in 8 exposures to 6% continuous hypoxia, and never in 10% hypoxia. A frequency analysis of the ECoG, excluding all sections exhibiting isoelectric and seizure activity, revealed no changes with 10% hypoxia, but a shift towards the lower bands during both repetitive and continuous 6% hypoxia. The extent of these shifts was greater in records that also displayed isoelectric ECoG and/or seizures. The ECoG spectrum recovered at the end of the hypoxic exposure, but not when isoelectric ECoG and/or seizures coexisted. We conclude that repeated, frequent episodes of hypoxia are more detrimental than a prolonged single event, and may contribute to the occurrence of Sudden Infant Death.

Animals↗
PubMed1995

Chronic night cough and asthma severity in children with stable asthma.

The relationship between night cough and other indices of asthma severity was studied in 21 children with clinically stable asthma and persistent night cough. Overnight cough was quantified and related to symptom scores, oxygen saturation (SaO2) during sleep, evening and morning peak flow recordings and daytime tests of lung function. In the index group the median number of coughing episodes was 23 (range 1-158). Only 4 children had counts of < 10 overnight, similar to the comparison group of 12 children all of whom had counts of < 10. There was a trend towards the association of overnight cough with reduced evening peak flow (r = -0.407, P = 0.07) and reduced SaO2 (r = -0.36, P = 0.10). Abnormalities in daytime tests of lung function were observed in 13 children. There was no relationship between night cough and daytime indices of lung function abnormality although children with more severe daytime abnormalities also had significant night cough. Conversely, five children with chronic night cough had normal daytime function. Conclusion. Night-time cough in children with asthma is not simply a reflection of daytime lung function status, whereas, overnight SaO2 correlates well. Other factors need to be explored to explain the variability of night-time cough in these children.

Adolescent↗
PubMed1995

Lung function from infancy to school age in cystic fibrosis.

The aim was to investigate pulmonary mechanics in patients with cystic fibrosis during infancy and again in early childhood to see whether infant tests predicted status at school age. Plethysmographic measurements of thoracic gas volume and airways resistance were made in 29 patients at 6 months and again at 5 years 10 months. Maximum flow at functional residual capacity was measured during infancy for comparison with maximum expiratory flow rates during childhood. While many patients had normal measurements during infancy, pulmonary function had deteriorated by school age. Thoracic gas volume at school age was significantly related to the values in infancy, but other measurements made during childhood were independent of infant values. The relations between measurements in infancy and early childhood described here provide a background against which the role of external factors on pulmonary function in young children with cystic fibrosis can be investigated.

Aging↗
PubMed1994

Relationship between respiratory symptoms and cough receptor sensitivity.

The relationship was studied between preschool and current respiratory symptoms and cough receptor sensitivity in children. Forty six white children aged 7 years were investigated. They were divided into three groups: (i) healthy children; (ii) children with a history of idiopathic cough; and (iii) children with a history of wheezing. Cough receptor sensitivity was assessed by the inhalation of serially increasing concentrations of nebulised citric acid. The concentration which first induced a cough was the cough threshold and was taken as a measure of cough receptor sensitivity. The cough threshold was unrelated to respiratory symptoms, bronchial responsiveness, parental smoking, and atopic status. A wide variation in cough threshold was seen. Although these results suggest that idiopathic cough is unrelated to cough receptor sensitivity as assessed by the citric acid cough threshold, it is unclear whether threshold measurements are an accurate reflection of receptor sensitivity.

Bronchi↗
PubMed1994

Pulmonary function in infants with cystic fibrosis: the effect of antibiotic treatment.

Since 1982 all infants born within the East Anglian Regional Health Authority have been screened for cystic fibrosis. Between April 1985 and April 1992 infants identified in this way have been entered into a randomised prospective controlled trial of antibiotic prophylaxis. Approximately half the infants received continuous oral flucloxacillin and the remainder received antibiotics when clinically indicated. Infants underwent tests of respiratory function at 3-4 months and at 1 year of age. Measurements of thoracic gas volume and airway conductance were made with an infant whole body plethysmograph, and maximum expiratory flow by the 'squeeze' technique. A total of 73 tests was performed of 42 infants. To facilitate comparisons, measurements were expressed as scores. The mean values of the scores for the two groups of infants fell within normal limits. There was no difference between the treatment groups at either age. A reduction in airways conductance was observed between the two tests.

Administration, Oral↗
PubMed1994

Clinical findings and respiratory function in infants following repair of oesophageal atresia and tracheo-oesophageal fistula.

Survival rates for infants undergoing surgical repair of oesophageal atresia with tracheo-oesophageal fistula (OA-TOF) have improved dramatically, but this condition remains associated with substantial morbidity. Most studies of patients following OA-TOF repair have concentrated on school-age and older people; whereas, the most hazardous period is infancy. We aimed to assess respiratory function in a group of infants following primary operative repair, and to relate the results to clinical findings during the first year of life. We studied 16 infants within 3 months of primary repair of OA-TOF. Measurements were made of maximum expiratory flow at functional residual capacity (VmaxFRC), thoracic gas volume (TGV) and airways resistance (Raw). Ten infants had tests repeated, usually to assess progress alongside continuing symptoms, or to ascertain improvement following additional surgery. Seven infants had essentially normal initial respiratory function tests, and six remained either symptom-free or developed only minor clinical problems. One infant subsequently developed stridor, with spontaneous improvement towards the end of the first year. The remaining nine infants had abnormal initial respiratory function tests: one was symptom-free at that time. The remainder developed respiratory and/or gastro-oesophageal symptoms. The functional abnormalities appeared to reflect the severity of the clinical problems encountered. We conclude that respiratory function testing in infants following OA-TOF repair may augment the value of clinical appraisal, help define postoperative respiratory status, and provide a general guide to likely clinical progress.

Airway Resistance↗
PubMed1993

Comparison of peripheral chemoreceptor responses in monozygotic and dizygotic twin infants.

The peripheral chemoresponses of infant twin pairs were determined using a single-breath hyperoxic stimulus. A total of 43 twin pairs of comparable gestation and birth weight were studied during sleep at a mean (SD) age of 8 wk (1.4) while alternately breathing either air or 16% oxygen in nitrogen. Infants responded to a single breath of 100% oxygen by a reduction in ventilation; the mean (SEM) reduction in air was 273 ml/min (10.6) and in 16% oxygen 560 ml/min (18.4). Within-pair variances were compared in 14 monozygotic and 28 dizygotic pairs utilizing combined responses (air + 16% oxygen) computed for measurements made in behavioral quiet sleep and in 9 monozygotic and 20 dizygotic pairs for whom data were complete in polygraphically confirmed quiet sleep. The variance of responses within dizygotic twin pairs was greater than in monozygotic pairs when expressed in ml/min: F ratio 4.11 (p = 0.005) for all data and F ratio 7.67 (p = 0.003) in quiet sleep. Expressed in ml/min/kg the difference was less significant: F ratio 1.83 (p = 0.126) for all data and F ratio 3.46 (p = 0.039) in quiet sleep. Gender, birth weight, and birth order had no effect on these findings. This closer similarity of response in monozygotic twin pairs is explained by proposing a high degree of heritability for the response.

Chemoreceptor Cells↗
PubMed1992

A scoring system for lung function tests in infants.

Measurements of thoracic gas volume (TGV), airway resistance (Raw), and airway conductance (Gaw) were calculated in a group of 42 normal infants using a whole-body plethysmograph. Maximum expiratory flow at functional residual capacity was measured in a separate group of 108 normal infants. Using data obtained from these infants the following regression equations were calculated: Gaw (L.s-1.cmH2O) = -0.0475 + 0.00164 x length (cm) square root of TGV (mL1/2) = -3.22 + 0.263 x length (cm) VmaxFRC (mL.s-1) = -173 + 5.2 x length (cm). The standard errors of prediction are a measure of the scatter of individual results from the normal population about the true regression line. They were used to define limits of the normal ranges for these tests of lung function, and to develop a scoring system. This approach is preferable to expressing results as percent predicted, which gives no indication of how likely a measurement is to be within normal limits.

Age Factors↗