Citric acid cough threshold and airway responsiveness in asthmatic patients and smokers with chronic airflow obstruction.

The relation between citric acid cough threshold and airway hyperresponsiveness was investigated in 11 non-smoking patients with allergic asthma (mean FEV1 94% predicted) and 25 non-atopic smokers with chronic airflow obstruction (mean FEV1 65% predicted). Cough threshold was determined on two occasions by administering doubling concentrations of citric acid. Seven of the 11 asthmatic subjects and 14 of 25 smokers with chronic airflow obstruction had a positive cough threshold on both test days. Cough threshold measurements were reproducible in both groups (standard deviation of duplicate measurements 1.2 doubling concentrations in asthma, 1.1 doubling concentrations in chronic airflow obstruction). Citric acid provocation did not cause bronchial obstruction in most patients, though four patients had a fall in FEV1 of more than 20% for a short time on one occasion only. No significant difference in cough threshold was found between the two patient groups despite differences in baseline FEV1 values. There was no significant correlation between cough threshold and the provocative concentration of histamine causing a 20% fall in FEV1 (PC20) histamine in either group. Thus sensory nerves can be activated with a tussive agent in patients with asthma and chronic airflow obstruction without causing bronchial smooth muscle contraction.     

Relationship between upper airway obstruction and gastroesophageal reflux in a dog model.

The association between gastroesophageal reflux (GER) and upper airway obstruction in children is recognized but not well understood. Our objective was to determine if the creation of a model of upper airway obstruction in dogs would cause GER and to determine if the GER is related to intrathoracic pressure changes. Five dogs underwent evaluation with esophageal manometry and pH probe at baseline and 1 week after creation of an upper airway obstruction. Airway obstruction was created by placement of a fenestrated cuffed tracheostomy tube, which was then capped and the cuff was inflated, requiring the animals to breathe via the fenestrations. The negative inspiratory pressure (Pes) (+/- SD) increased from 11.8 +/- 4.8 cm H(2)O at baseline to 17.6 +/- 4.9 cm H(2)O 1 week after creation of an airway obstruction (p = .029). None of the dogs had GER at baseline with a reflux index (RI) value of 0.0; however, 1 week after creation of airway obstruction, three out of five dogs had GER, with a mean RI value of 21.2 +/- 21.2. There was a significant (p = .023) correlation (r = .928) of the changes in Pes and RI values following airway obstruction.Upper airway obstruction (UAO) does cause GER in this canine model. Severity of GER is significantly correlated with Pes changes.     

Effect of betamethasone on airway obstruction and bronchial response to salbutamol in prednisolone resistant asthma.

Twelve patients with chronic severe asthma, having previously shown an FEV1 increase of less than 20% of the predicted value with prednisolone treatment (20-60 mg daily for 10 days), took part in a double blind crossover comparison of equipotent anti-inflammatory doses of betamethasone and prednisolone. Betamethasone (8 mg) and prednisolone (40 mg) were administered daily for 10 days with a washout period of 10 days between. In this first part of the study betamethasone was administered intramuscularly and prednisolone orally. Placebo injections and tablets were used. Mean FEV1 was not significantly different before each period. There was a significant increase in FEV1 while they were taking betamethasone but not prednisolone. Individual analysis of the data showed that FEV1 increased with betamethasone in nine patients and remained stable or decreased in three. During treatment with prednisolone baseline FEV1 increased moderately in three patients (FEV1 0.3, 0.5 and 0.6 l) and remained stable or decreased in nine. There was no significant difference between the bronchodilator responses to cumulative doses of inhaled salbutamol when they were measured immediately before, on the last day of treatment with each steroid, and between steroid treatment periods. The same protocol was followed four months later in five of the 12 patients but both drugs were administered orally on this occasion. Similar results were obtained. The greater effect of betamethasone on bronchial obstruction may be due to its longer biological half life or to some unidentified property of its metabolites. The bronchial response to inhaled beta 2 agonist appears not to be influenced by either steroid in these patients.     

Capsaicin responsiveness and cough in asthma and chronic obstructive pulmonary disease

BACKGROUND: Chronic cough is associated with an increased sensitivity to inhaled capsaicin in a number of conditions but there are no data for patients with more severe asthma or chronic obstructive pulmonary disease (COPD). Moreover, the relationships between the capsaicin response (expressed as the concentration of capsaicin provoking five coughs, C5), self-reported cough, and routine medication is not known. METHODS: The cough response to capsaicin in 53 subjects with asthma, 56 subjects with COPD, and 96 healthy individuals was recorded and compared with a number of subjective measures of self-reported cough, measures of airway obstruction, and prescribed medication. In asthmatic subjects the relationships between the cough response to capsaicin and mean daily peak flow variability and non-specific bronchial hyperresponsiveness to histamine were also examined. RESULTS: Subjects with asthma (median C5 = 62 mM) and COPD (median C5 = 31 mM) were similarly sensitive to capsaicin and both were more reactive than normal subjects (median C5 >500 mM). Capsaicin sensitivity was related to symptomatic cough as measured by the diary card score in both asthma and COPD (r = -0.38 and r = -0.44, respectively), but only in asthma and not COPD when measured using a visual analogue score (r = -0.32 and r = -0.05, respectively). Capsaicin sensitivity was independent of the degree of airway obstruction and in asthmatics was not related to PEF variability or PC(20) for histamine. The response to capsaicin was not related to treatment with inhaled corticosteroids but was increased in those using anticholinergic agents in both conditions. CONCLUSIONS: These data suggest that an increased cough reflex, as measured by capsaicin responsiveness, is an important contributor to the presence of cough in asthma and COPD, rather than cough being simply secondary to excessive airway secretions. The lack of any relationship between capsaicin responsiveness and airflow limitation as measured by the FEV(1) suggests that the mechanisms producing cough are likely to be different from those causing airways obstruction, at least in patients with COPD.     

Relationship between peripheral airway dysfunction, airway obstruction, and neutrophilic inflammation in COPD

BACKGROUND: Considerable research has been conducted into the nature of airway inflammation in chronic obstructive pulmonary disease (COPD) but the relationship between proximal airways inflammation and both dynamic collapse of the peripheral airways and HRCT determined emphysema severity remains unknown. A number of research tools have been combined to study smokers with a range of COPD severities classified according to the GOLD criteria. METHODS: Sixty five subjects (11 healthy smokers, 44 smokers with stage 0-IV COPD, and 10 healthy non-smokers) were assessed using lung function testing and HRCT scanning to quantify emphysema and peripheral airway dysfunction and sputum induction to measure airway inflammation. RESULTS: Expiratory HRCT measurements and the expiratory/inspiratory mean lung density ratio (both indicators of peripheral airway dysfunction) correlated more closely in smokers with the severity of airflow obstruction (r = -0.64, p<0.001) than did inspiratory HRCT measurements (which reflect emphysema severity; r = -0.45, p<0.01). Raised sputum neutrophil counts also correlated strongly in smokers with HRCT indicators of peripheral airway dysfunction (r = 0.55, p<0.001) but did not correlate with HRCT indicators of the severity of emphysema. CONCLUSIONS: This study suggests that peripheral airway dysfunction, assessed by expiratory HRCT measurements, is a determinant of COPD severity. Airway neutrophilia, a central feature of COPD, is closely associated with the severity of peripheral airway dysfunction in COPD but is not related to the overall severity of emphysema as measured by HRCT.     

Bronchial responsiveness to inhaled histamine and isoprenaline in patients with airway obstruction

In order to examine the hypothesis that bronchial reactivity to non-specific constrictor stimuli is influenced by the resting tone of the bronchial smooth muscle, the airway responses to inhaled histamine solution and inhaled isoprenaline were measured in 19 patients with airway obstruction. There was a significant positive correlation between the size of the constrictor response to histamine and the dilator response to isoprenaline (r = +0.83; p less than 0.01) as measured by changes in specific airway conductance. Patients with asthma showed greater bronchial reactivity to both histamine and isoprenaline than those with chronic bronchitis, although some patients had changes intermediate between the two extremes.     

Nocturnal enuresis in children with upper airway obstruction

This study presents the results of our experience with 115 children between the ages of 3 and 19 years who have had symptoms of upper airway obstruction and nocturnal enuresis. Twelve children had secondary enuresis, and 103 children had primary enuresis. Surgical removal of upper airway obstruction led to a significant decrease in or complete cure of nocturnal enuresis in 87 (76%) of the children studied. Eleven children were also studied with polysomnographic tracings in an attempt to determine a relationship between their sleep patterns and nocturnal enuresis.     

Acute and chronic airway obstruction in children

Airway obstruction is more common in children than in adults. This is because of subtle anatomical differences in the childhood airway and an increased propensity to infection. Effects of obstruction manifest more quickly in children because of a smaller airway diameter, reduced physiological reserve and easily fatigued respiratory muscles. The signs of airway obstruction differ between upper and lower airway obstruction, and in the spontaneously breathing and ventilated child because of the differences in the mechanics of breathing in each of these situations. The anaesthetist must be able to recognize risk factors for airway obstruction such as a history of respiratory symptoms, including sleep-disordered breathing, and high-risk groups, such as ex-preterm infants. The anaesthetist must also be able to recognize the signs of airway obstruction in the awake, anaesthetized and paralysed child. Upper airway obstruction may be moderate, as in many cases of tonsillar or adenoidal hypertrophy and laryngomalacia, or severe, as in some upper respiratory tract infections such as epiglottitis, croup or bacterial tracheitis. Lower airway obstruction is most commonly seen in children with reactive airways secondary to atopic asthma, viral-associated wheeze or chronic lung disease of prematurity. It can also accompany chronic infection and bronchiectasis, as in cystic fibrosis or primary ciliary dyskinesia. Pulmonary hypertension can develop in any child with chronic airway obstruction and is an additional risk factor for complications including death during anaesthesia. This article outlines some of the issues in acute and chronic airway obstruction in children. Where possible up-to-date anaesthetic management or algorithms will be referenced.     

Acute and chronic airway obstruction in children

Airway management is one of the fundamental skills of any anaesthetist. Considerable anatomical changes occur between birth and adulthood during the development of the paediatric airway. Knowledge of these changes will influence airway planning during childhood. Airway obstruction complicates airway management and any anaesthetist working with children should be able to assess the airway for the presence of obstruction and generate a differential diagnosis of cause. This article aims to summarize key anatomical features of the paediatric airway, common causes of airway obstruction in children and provide suggestions for how to manage these patients.     

Acute and chronic airway obstruction in children

Airway management is one of the fundamental skills of any anaesthetist. Considerable anatomical changes occur between birth and adulthood during the development of the paediatric airway. Knowledge of these changes will influence airway planning during childhood. Airway obstruction complicates airway management and any anaesthetist working with children should be able to assess the airway for the presence of obstruction and generate a differential diagnosis of cause. This article aims to summarize key anatomical features of the paediatric airway, common causes of airway obstruction in children and provide suggestions for how to manage these patients.     

Acute and chronic airway obstruction in children

Airway obstruction is more common in children than in adults. This is because of subtle anatomical differences in the childhood airway and an increased propensity to infection. Effects of obstruction manifest more quickly in children because of a smaller airway diameter, reduced physiological reserve and easily fatigued respiratory muscles. The anaesthetist may encounter airway obstruction in children both outside and within the operating theatre. Problems can be either anticipated or unexpected. The anaesthetist must be able to recognize risk factors for airway obstruction such as a history of respiratory symptoms, including sleep-disordered breathing, and high-risk groups, such as ex-preterm infants. An understanding of the pathophysiology of airway obstruction can help in the recognition, diagnosis and appropriate management of airway obstruction. The pathophysiology of airway obstruction is intimately linked with the anatomy and mechanics of the upper airway and the tracheobronchial tree. The pathophysiology of airway obstruction is reviewed and this knowledge applied to problems occurring inside and outside the operating theatre, including both anticipated and unexpected problems.     

Circadian change in bronchial responsiveness and airflow obstruction in asthmatic children.

To throw light on the question of whether the increase in bronchial responsiveness seen during the night is due to increased airflow obstruction, nine asthmatic children with increased airflow obstruction at night (group 1) were compared with nine without (group 2). The mean fall in forced expiratory volume in one second (FEV1) between 16.00 and 04.00 hours was 21.9% in group 1 and 2.3% in group 2. Selection of patients was based on the amplitude of change in peak expiratory flow (PEF) measured every four hours for three consecutive days at home. The study was performed in hospital on four consecutive days. Medication was withheld for three days before and during the measurements at home and in hospital. On the first day in hospital (day 4) FEV1 was measured every four hours for 24 hours. On day 6 inhaled histamine provocation tests were performed at the same times as the FEV1 measurements on day 4. Both groups showed a nocturnal fall in the provocative dose of histamine causing a 20% fall in FEV1 (PC20). The mean change in histamine PC20 from 16.00 to 04.00 hours was 1.1 doubling doses of histamine in group 1 and 1.5 doubling doses in group 2. The results indicate that the increase in nocturnal bronchial responsiveness that occurs at night is not due to an increase in airflow obstruction.     

Exhaled nitric oxide and asthma: complex interactions between atopy, airway responsiveness, and symptoms in a community population of children

BACKGROUND: Exhaled nitric oxide (FE(NO)) is raised in asthmatic children, but there are inconsistencies in the relationship between FE(NO) and characteristics of asthma, including atopy, increased airway responsiveness (AR), and airway inflammation. The aim of this study was to investigate the relationship between FE(NO) and asthma, atopy, and increased AR in children. METHODS: One hundred and fifty five children (79 boys) of mean age 11.5 years underwent an assessment that included FE(NO) measurements, spirometric tests, inhaled histamine challenge, and a skin prick test. Blood was collected for eosinophil count. Current and past asthma like symptoms were determined by questionnaire. RESULTS: In multiple linear regression analyses FE(NO) was associated with atopy (p<0.001), level of AR (p = 0.005), blood eosinophil count (p = 0.007), and height (p = 0.002) but not with physician diagnosed asthma (p = 0.1) or reported wheeze in the last 12 months (p = 0.5). Separate regression models were conducted for atopic and non-atopic children and associations between FE(NO) and AR, blood eosinophils and height were only evident in atopic children. Exhaled NO was raised in children with a combination of atopy and increased AR independent of symptoms. CONCLUSION: Raised FE(NO) seems to be associated with an underlying mechanism linking atopy and AR but not necessarily respiratory symptoms.     

Characteristics of wheeze during histamine-induced airways obstruction in children with asthma.

BACKGROUND--An automated system has been developed for the detection of sound patterns suggestive of airways obstruction in long term recordings. The first step, presented here, was tracheal sound recording during histamine-induced airways obstruction. METHODS--The tracheal sounds of 29 children aged 8-19 years with asthma were recorded during airways obstruction caused by histamine inhalation using a system for continuous respiratory telemetry and computer analysis. Sound patterns were analysed, classified, and related to airways obstruction measured by lung function tests based on the forced expiratory volume in one second (FEV1). RESULTS--Five sound patterns were identified, one dominant sensitive and four specific to a fall in FEV1 of > 20%. The presence of at least one of three specific sound patterns during unforced respiration predicted a fall in FEV1 of > 20% in 87.5% of the subjects. The inspiratory and expiratory sound patterns were almost equally informative of airways obstruction. CONCLUSIONS--Wheezes can be differentiated with more precision than is currently accepted. Tracheal sound patterns are sensitive and specific predictors of histamine-induced airways obstruction. These patterns are neither invariably nor proportionally related to the results of lung function testing. However, they can be used for detection of airways obstruction on the basis of their presence or absence.     

Acute airway obstruction in children with benign head and neck tumours. Case reports

Infants presenting with acute airway obstruction secondary to cystic hygroma and neurofibroma are presented. Early surgical correction of large benign tumours of the head and neck is recommended to prevent life-threatening complications.     

The diagnosis of airway obstruction in children

Airway obstruction in children has many causes. Although vascular rings may have early onset of symptoms there was considerable delay in establishing the correct diagnosis. Barium swallow is diagnostic. Other tests, such as angiocardiography, bronchoscopy, bronchography, and lung scan are usually unnecessary. Pulmonary sling is a less common cause of vascular obstruction. Barium swallow showing anterior indentation at the level of the pulmonary hilum is diagnostic. Cysts and tumors are other causes of severe airway obstruction. The diagnostic and operative problems in three patients are discussed as examples. It is concluded that barium swallow is the most important single investigation in the evaluation of airway obstruction.     

Tracheobronchial obstruction in children: experience with endoscopic airway stenting

BACKGROUND: We reviewed our experience to determine the role of endoscopic airway stents in children with tracheobronchial obstruction. METHODS: Seventeen children (10 boys and 7 girls) aged 2 months to 16 years underwent tracheobronchial stenting. Etiology of the tracheobronchial obstruction included external vascular compression (n = 9); tracheobronchial anastomotic strictures after heart-lung/lung transplantation (n = 4); airway compression by malignant mediastinal mass (n = 2), and subglottic/high tracheal stenosis after prolonged intubation with a tracheostomy in situ (n = 2). Indications for airway stenting were failure to wean from ventilator after a mean of 82.5 days (range, 2 to 210) in 8 children; and dyspnea or stridor in the remaining 9 children. RESULTS: Ten children had a total of 24 uncovered self-expanding metal stents (either Magic Wallstent or Ultraflex Microvasive) and 7 children had silicone stents (2 straight, 3 Y and 2 T tube stents). At follow-up at 1 week to 72 months (median 21), only 8 of 17 (47%) children were alive but all the deaths were secondary to the underlying pathology and not related to tracheobronchial stenting. Six of 8 ventilator-dependent children were extubated after a mean of 5.3 days (range, 2 to 11) after airway stenting. For the 9 children stented for dyspnea, mean Medical Research Council dyspnea score decreased from 3.0 to 1.6 after stenting. CONCLUSIONS: Tracheobronchial stenting in children is only rarely needed and often undertaken in dire circumstances. The procedure has led to significant symptomatic benefit in dyspneic children and has enabled ventilator-dependent children to be extubated. Medium-term outlook after stenting with self-expanding metal stents for vascular compression of the airway is encouraging. The long-term outcome remains uncertain, however, and is ultimately influenced by the underlying disease.