Respiratory








After reading this chapter you should be able to assess, diagnose and manage:




  • chronic cough



  • wheezing illnesses



  • lower respiratory tract infection



  • cystic fibrosis presentation



  • sleep disordered breathing



  • life-threatening events including sudden unexpected death in infancy



and




  • select and interpret appropriate respiratory investigations



  • understand the indications for long-term ventilation and respiratory support




Respiratory investigations


Blood gases


Values for carbon dioxide and pH do not differ markedly between arterial and venous samples and both will provide important information for clinical care ( Table 17.1 ). Oxygen results from venous and capillary samples reflect values after tissue perfusion and are therefore ignored in clinical practice.



Table 17.1

Responses to changes in plasma oxygen and bicarbonate levels









































abnormality primary disturbance effect on base excess compensatory response
pH pCO2
respiratory acidosis ↑ pCO2 negative ↑ [HCO3-]
metabolic acidosis ↓ [HCO3-] N or ↓ negative ↓pCO2
respiratory alkalosis ↓ pCO2 N or ↓ positive ↓[HCO3-]
metabolic alkalosis ↑ [HCO3-] N or ↑ positive ↑pCO2


Chest radiograph


Radiological investigation of respiratory disease is commonly used in clinical practice. The posterior-anterior (PA) film is preferable where possible so as to facilitate assessment of cardiac size, although an anterior-posterior (PA) film may be practicable in the acutely ill or small child. Lateral films expose the child to significantly more radiation and rarely add clinically useful information.


Pulse oximetry


The correlation between peripheral saturation measurement and arterial saturation is sufficient for most clinical assessments. Since the technique measures absorbance in haemoglobin, it may provide normal values in anaemic individuals even though the oxygen carrying capacity is significantly reduced and it may also give low saturation values in individuals with poor peripheral perfusion.


Spirometry


Spirometry measures lung volumes, usually during a forced exhalation and inhalation manoeuvre, and the test is usually possible in children over the age of 5 or 6 years ( Figure 17.1 ). In forced manoeuvres such as the Forced Expiratory Volume in 1 second (FEV 1 ), the increased intrathoracic pressure during forced exhalation is transmitted to the bronchi, acting to decrease the diameter of the lumen and so limiting the rate of flow—this is termed ‘dynamic airway narrowing’.




Fig. 17.1


Common patterns of flow volume loops.


During spirometry, a variety of volumes are measured, and there are recognisable patterns of these ( Table 17.2 ). Reference values allow the spirometry measurements of a child to be compared to the average measurements for their age, sex, height and race and these can be expressed in the form of a percentage predicted or a Z score.


A: in a well child, the loop proceeds in a clockwise manner initially with a rapid rise of flow over a small volume, reaching the Peak Expiratory Flow Rate (PEFR). Over the remaining lung volume, the patient expires to the end of vital capacity. The downward reflection of the loop below the zero line, back to the origin, represents the inspiration after the forced expiration.


B: an ‘obstructed’ loop. Note the concavity of the downward phase of expiration.


C: a ‘restrictive’ pattern. Note that the volume is decreased—the flow rate may be more normal.


D: extra-thoracic fixed obstruction (e.g. vascular ring around the trachea or mediastinal mass). Note that the peak inspiratory and expiratory flows are both reduced.



Table 17.2

Patterns of lung volume changes.
























FEV1 FVC FEV1/FVC ratio Interpretation
normal Normal Normal normal
reduced normal reduced obstruction (e.g. asthma, cystic fibrosis)
normal/reduced reduced normal/increased restriction (e.g. pulmonary hypoplasia, scoliosis, interstitial lung disease)


Bronchodilator reversibility test


Assesses children and young people (from age of 5 years) for bronchial hyperreactivity by recording spirometry values before and after the administration of a bronchodilator (usually salbutamol). An improvement in FEV1 of 12% or more is regarded as a positive response.


Bronchoprovocation test


The bronchoprovocation test assesses whether a child with initially normal pulmonary function tests may actually produce abnormal results when an inhaled irritant is given. The typical agents used to challenge the airways are methacholine, histamine and adenosine. The concentration of the agent which induces a 20% fall in FEV 1 is recorded and the lower the dose then the greater the degree of airway hyperreactivity. Exercise can also be used as a ‘provocation test’. Both these investigations should be undertaken by teams competent in their administration.


Fraction of exhaled nitric oxide (FeNO)


FeNO can be measured in most school-aged children and is an indicator of airways inflammation. It is useful where the history suggests asthma but spirometry is normal or an obstructive pattern is not reversible. Levels of >35 parts per billion are abnormal in children aged 5–18 years.


Bronchoscopy


Bronchoscopy uses either a rigid or flexible bronchoscope and allows direct visualisation of the internal airway structure and allows for microbiological sampling or biopsy. Inhaled foreign may be located and extracted.


Whole body plethysmography (or the ‘body box’)


This measures thoracic gas volumes, including air that is not directly communicating with the airway opening (such as ‘trapped gas’ or lung cysts).


Transfer factor of the lung for carbon monoxide (TLCO)


The rate of oxygen diffusion across the alveolar membrane can be assessed by measuring diffusing capacity of carbon monoxide, but the test can only be done in cooperative older children.


Cough


Cough is a reflex which removes mucous and other material from the lungs and is less effective in glottic dysfunction, tracheostomy and neuromuscular weakness.


Cough can be the cardinal feature of both acute, life-threatening and chronic, life-limiting respiratory disease and the causes can be categorised by the age of the child ( Table 17.3 ), the duration of the cough and the character of the cough.



Table 17.3

Selected causes of cough, grouped by the typical ages at presentation.












Infant Preschool School age/adolescent
primary ciliary dyskinesia
cystic fibrosis
infections (viruses, bacteria, chlamydia, pertussis)
congenital malformations (tracheoesophageal fistula)
foreign body
infection
cystic fibrosis
primary ciliary dyskinesia
bronchiectasis
immunodeficiency
asthma
passive cigarette smoke
aspiration
asthma
postnasal drip
infection
cystic fibrosis
primary ciliary dyskinesia
immunodeficiency
bronchiectasis
smoking
air pollution
tic cough
aspiration


The character of the cough can be described as ‘wet’ or ‘dry’ with the former suggestive of excessive secretions. In infants and children, a cough associated with sputum production is rarely ‘productive’ as the sputum is usually swallowed rather than expectorated. A wet cough implies infection and, if chronic, suggests protracted bacterial bronchitis, suppurative lung disease or bronchiectasis. A wet cough might also feature in gastro-oesophageal reflux and aspiration. An acute viral cough can last 3 to 4 weeks whilst the ‘postinfectious cough’ can last much longer, especially in pertussis.


Protracted bacterial bronchitis


This is the most common cause of a prolonged cough over 4 weeks duration in preschool children. The child usually looks well, has no other clinical signs and has normal growth. It is typically associated with infection by M. catarrhalis, S. pneumoniae and H. influenzae and can be treated effectively with a prolonged (2–4 week) course of an oral antibiotic, such as coamoxiclav. The diagnosis is confirmed by the resolution of symptoms after the trial of therapy. If the cough does not resolve after 4 weeks of antibiotics, then chronic suppurative lung disease or bronchiectasis should be considered.


‘Red flags’ for cough


A cough should be investigated thoroughly if any of the following are present:




  • sudden onset cough after choking



  • night sweats



  • haemoptysis



  • poor weight gain or weight loss



  • cough which progressively worsens



  • signs of lung disease—clubbing, barrel-shaped chest, Harrison’s sulci



Investigations


For a chronic wet cough, a typical approach would involve chest radiographs, bacterial cough swab and viral swabs, a sweat test and an initial immune panel (immunoglobulins, functional antibodies, full blood count and lymphocyte subsets). If primary ciliary dyskinesia is suspected, patients are referred for ciliary studies to a national referral diagnostic centre whilst, if bronchiectasis is suspected, a CT scan should be undertaken. Bronchoscopy may also be indicated.


Treatment and management


Treatment is directed at the underlying cause. There is no role for over-the-counter ‘cough medicines’ which usually contain opiate-derived compounds to suppress the cough. When a cough is felt to be benign, a watch-and-wait approach is appropriate.


Wheezing disorders


Young children inherently have narrow airways and consequently generate wheeze with only minimal reduction in the diameter of the bronchi and bronchioles. Most wheeze occurs in the expiratory phase as the increased intrathoracic pressure required for expiration will also lead to external pressure on the smaller airways. A biphasic wheeze or a very localised wheeze suggest a fixed area and warrants further consideration ( Table 17.4 ).



Table 17.4

Common causes of wheeze






















Cause Examples
infective mycoplasma
pertussis
viral induced wheeze—adenovirus, respiratory syncytial virus, human metapneumovirus, parainfluenza, influenza
inflammatory hypersensitivity pneumonitis
irritant inhalation—smoke, illicit drugs
sarcoidosis
vasculitis
physical compression foreign body aspiration
granulation tissue in airway
lymph node enlargement
tumour—lymphoma
vascular ring, vascular compression
tracheo-bronchomalacia
bronchogenic or pulmonary cyst
complex pathophysiological primary ciliary dyskinesia
cystic fibrosis
bronchiectasis
aspiration and gastro-oesophageal reflux disease.
hyperventilation.
upper airway vocal cord palsy
vocal fold dysfunction
angioedema


Asthma


The key clinical features of asthma are episodic wheeze that is present during exacerbations along with breathlessness and cough. Some patients have interval symptoms, which include breathlessness, cough and wheeze that may be exacerbated by exertion, changes in environmental temperatures, damp air, emotion and laughter. Nocturnal cough may also be present. Between attacks many children may be symptom free with normal lung function. Those patients with poorly controlled asthma may have a hyperinflated chest and develop Harrison’s sulci ( Figure 17.2 ) which are fixed inward grooves in the chest wall where the diaphragm inserts into the internal surfaces of the ribs.




Fig. 17.2


Chest of 11-year-old boy with poorly controlled asthma. Harrison’s sulci visible (arrow).


Asthma in the acute setting


An acute asthma attack is associated with breathlessness and a feeling of a ‘tight’ chest, with a characteristic nonproductive cough. Clinical signs include:




  • tachypnoea



  • intercostal recession



  • chest indrawing



  • ‘tracheal tug’



  • prolongation of the expiratory phase of breathing



  • wheeze which may be audible without a stethoscope



In more severe asthma, patients use their accessory muscles of respiration. Oxygen saturations are often maintained during an attack and when patients do deteriorate, they are usually hypoxic prior to becoming hypercapnic as the latter finding is a late feature, and indicates a severe, or life-threatening episode ( Table 17.5 ).



Table 17.5

Levels of severity of an acute asthma attack




















Mild-moderate Severe Life threatening
oxygen saturation 92% and above in air
PEFR > 50% predicted of best
cannot complete sentences in one breath or too breathless to talk or eat/feed
oxygen saturation < 92% in air
PEFR < 50% predicted or best
cyanosis
silent chest
poor respiratory effort
fatigue or exhaustion
agitation or reduced level of consciousness
raised carbon dioxide
under 6 years
heart rate < 140/min
respiratory rate < 40/min
under 6 years
heart rate > 140/min
respiratory rate > 40/min
6 years and over heart rate < 125/minrespiratory rate < 30/min 6 years and over heart rate > 125/min
respiratory rate > 30/min


Associations


Asthma is often associated with other atopic conditions, in particular hay fever, food allergies and eczema. There is often a strong history of familial atopy.


Wheeze in the under 5-year olds


A current challenge is that many children wheeze in the preschool period and such children are often diagnosed with ‘pre-school wheeze’ rather than asthma. This can be categorised as either:




  • recurrent viral-induced wheeze—evidence of a viral infection with each occurrence of wheeze



  • multi trigger wheeze—episodic wheeze after exposure to pollen, moulds or house dust mite



In reality, many children will move between the two groups and the current NICE guidelines recommend treating them based on observation and clinical judgment along with regular reviews.


Investigations


No single test is diagnostic of asthma, but a history of recurrent wheeze which responds to treatment is useful. Spirometry is the key diagnostic test and can be performed in most children who are 5 years and older. The FEV 1 , FEV 1 /FVC ratio and the FEF 25–75 are all reduced.


Administration of a bronchodilator (usually salbutamol) should result in an improvement, and an increase in FEV 1 volume of 12% over the baseline is considered reversible airflow obstruction. Peak expiratory flow is highly effort dependent and it alone should not be relied upon.


Exercise challenge tests are useful and spirometry is undertaken before and after exercise. A decrease of 10% of FEV 1 is usually considered diagnostic of exercise-induced asthma.


Treatment and management of chronic asthma


There are several stepwise approaches to increasing asthma treatment but central to all the guidelines is regular review of symptoms and the stepping down of therapy when appropriate. A further key component of treatment is the avoidance of cigarette smoke ( Table 17.6 ).


The major challenge in asthma is adherence to medication and it is well recognised that many patients take only around half their prescribed doses of inhalers. Therefore, rather than automatically ‘stepping up’ treatment, a careful, sensitive discussion around adherence is often more helpful if patients have frequent exacerbations or loss of control of daily symptoms.



Table 17.6

Pharmacological management of asthma following NICE recommendations




























Situation Therapy
if infrequent, short-lived wheeze and normal lung function
consider SABA as reliever therapy alone
if asthma-related symptoms 3 times a week or more, or causing waking at night or uncontrolled with a SABA alone
consider low-dose ICS as the first-line maintenance therapy
if uncontrolled on a paediatric low dose of ICS
consider LTRA in addition to the ICS and review the response to treatment in 4 to 8 weeks
if uncontrolled on a low dose of ICS and an LTRA as maintenance therapy
consider stopping the LTRA and starting a LABA in combination with the ICS
if uncontrolled on a paediatric low dose of ICS and a LABA as maintenance therapy
consider changing the ICS and LABA maintenance therapy to a MART regimen with a paediatric low-maintenance ICS dose
if uncontrolled on a paediatric low-maintenance ICS dose with LABA consider increasing the ICS to a paediatric moderate maintenance dose (either continuing on a MART regimen or changing to a fixed dose of an ICS and a LABA, with a SABA as a reliever therapy)
if asthma is uncontrolled in children and young people (aged 5 to 16) on a paediatric moderate maintenance ICS dose with LABA (either as MART or a fixed-dose regimen) seek advice from a healthcare professional with expertise in paediatric asthma management

SABA = short acting beta-agonist (e.g. salbutamol); LABA = long-acting beta agonist (e.g. salmeterol or formoterol—unlicensed in under 5s); LTRA = leukotriene receptor antagonist; ICS = inhaled corticosteroid; MART = maintenance and reliver treatment.


Guidelines for the pharmacological management of asthma are published by NICE, BTS/SIGN and GINA (Global Initiative for Asthma Management and Prevention). There are some differences between these guidelines but all follow a similar approach to management.


Treatment and management of acute attack


Children and young people with asthma are at risk of acute attacks which may progress rapidly and become life threatening. Presentation requires prompt assessment and administration of high flow oxygen through a tight-fitting mask when the SpO 2 is less than 94% or there is any suggestion of respiratory compromise.


Those with a mild to moderate episode should be given inhaled ß 2 -agonist and, if there is a failure of response, inhaled ipratropium bromide should be added via a nebuliser. Oral steroids should be administered at an early stage when possible although their effect will not be immediate.


If reassessment after a short interval reveals a poor response, then an initial single bolus dose of intravenous salbutamol is given followed by intravenous magnesium sulphate if there is a minimal response. Discussions with colleagues from anaesthetics and paediatric intensive care should be undertaken.



Clinical Scenario


A 15-year-old girl was referred for evaluation of recent onset of cough and wheeze. She had been well previously, had no history of atopy and she was not a smoker. She was, however, a high performing runner but would develop symptoms as soon as he started sprinting on the field. She described an inspiratory stridor, dry cough, tightness of chest and throat. She would stop running and the coughing would cease. She had been on high-dose combination of inhaled steroids and long-acting beta agonists without any benefit.


Her spirometry was entirely normal at baseline; however, after strenuous exercise on treadmill there was marked decrease in inspiratory flow volume. There was associated inspiratory wheeze. Continuous nasolaryngoscopy whilst on treadmill demonstrated severe adduction of laryngeal structures in parallel with severe respiratory distress. Psychological evaluation did not reveal any obvious contributing factors.


A pH study demonstrated frequent gastro-oesophageal reflux and endoscopy indicated that this may be long standing.


A diagnosis was made of exercise-induced laryngeal obstruction secondary to chronic gastro-oesophageal reflux.


Treatment with proton-pump inhibitor was commenced and a referral made to speech therapy with the aim of controlling laryngeal dysfunction. Following this intervention, she had a marked improvement in symptoms and her inhaled medications were withdrawn. She was able to return to high performance running.



Lower respiratory tract infections


A microbiological diagnosis is not made in most children with pneumonia but the organisms likely responsible depend on the age of the child. In older children Streptococcus pneumoniae and Mycoplasma pneumoniae are commonly implicated with the latter more common in school-age children. In those under 2 years, the commonest bacterial cause of pneumonia is Streptococcus pneumoniae which causes around a third of radiologically confirmed pneumonia in this age group. A viral cause is more common in younger children—commonly respiratory syncytial virus (RSV) or human metapneumovirus. Infections caused by group A streptococcus and Staphylococcus aureus are more likely to cause necrotising pneumonia and children with these infections are more likely to require intensive care.


Clinical presentation


The physical signs of pneumonia will help make a clinical diagnosis and also assign the degree of severity and guide management. Although some factors differ between infants and young children, the common findings are fever, tachypnoea, respiratory distress, chest pain, abdominal pain and headache. Cough may be absent initially. Wheeze is uncommon in children with pneumonia.



Table 17.7

Conditions that may result in sleep disordered breathing













































































Airway and breathing sleep-related disorders
obstructive sleep apnoea and hypoventilation
high-risk children
Down syndrome
neuromuscular disease
craniofacial syndromes
mucopolysaccharidoses
achondroplasia
Prader Willi syndrome
congenital central hypoventilation syndrome
Nonrespiratory sleep disorders/disorders with daytime sleepiness
insufficient night sleep
narcolepsy
idiopathic CNS hypersomnia
chronic fatigue syndrome
delayed sleep phase syndrome
restless leg syndrome
non-REM arousal disorders sleep terror, sleep walking, confusional arousals
sleep–related movement disorders
REM parasomnias nightmares, REM movement disorders

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Jun 18, 2022 | Posted by in PEDIATRICS | Comments Off on Respiratory
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