Tachypnoea in a Well Baby: What to Do Next?
Tachypnoea in a Well Baby: What to Do Next?
There are numerous causes of tachypnoea in term infants (reviewed by Sasidharan). Often the tachypnoea is just one of several signs in a clearly unwell child, examples include, a baby with a metabolic acidosis for example from numerous rare metabolic disorders; bacterial sepsis; or significant pain, for example, from a volvulus. In some children, the cause is obvious on initial assessment, from the history, for example, narcotic withdrawal and postbirth asphyxia. In some, it may be determined on first examination, for example, the small thorax of Jeune asphyxiating thoracic dystrophy, bell-shaped chest from pulmonary hypoplasia, hypotonia associated with neurological or neuromuscular disease, stridor due to upper airway obstruction or even severe neonatal rickets.
Below are some causes to consider in a child who seems well, has a normal clinical examination, but is without an immediately obvious diagnosis, with the relevant investigations that may provide the answer.
Infection. It is likely the child would have other symptoms and signs, particularly fever and cough, nevertheless, low grade or chronic infection must be considered. A nasopharyngeal aspirate for respiratory viruses and a cough swab for bacterial culture, and possibly a white cell count and C reactive protein may be helpful. Pulmonary tuberculosis has been described in children under 1 year, with tachypnoea the predominant sign, and not all patients had a contact history, cough or abnormal radiograph, although most did.
Cystic Fibrosis. In the UK and many other countries, newborn screening means babies are diagnosed with cystic fibrosis (CF) at around 3–4 weeks of age; however screening is not infallible. While most babies are symptom-free from the respiratory perspective, the majority have suboptimal weight gain, often with abnormal stools. Infants can present with tachypnoea, recurrent cough and sometimes wheeze, but our experience is that it is most unusual for tachypnoea to be the sole symptom in a baby with CF. Nevertheless it must be considered and a sweat test performed if appropriate.
Interstitial Lung Disease. This is a heterogeneous group of rare diseases, most often accompanied by crackles, recession, hypoxaemia and eventually failure to thrive. However in some, tachypnoea is the only obvious symptom, and the severity of symptoms and signs varies. Consideration should be given to neuroendocrine cell hyperplasia, previously known as persistent tachypnoea of infancy; it is often associated with recession, crackles in the chest and sometime hypoxia. There is an airway obstruction element to the condition, but the prognosis is generally good, with symptoms resolving at a median of 18 months (range 6–60 months), although in practice it may be even longer. Inherited surfactant protein C deficiency, ATP-binding cassette transporter A3 and thyroid transcription factor-1 are important, although again other signs of respiratory distress are likely to be present. Surfactant protein B deficiency is lethal in neonates so is unlikely to present with just tachypnoea. A chest CT scan can be highly suggestive, although diagnostic certainty may require a lung biopsy. In cases of neuroendocrine cell hyperplasia, the appearance is quite characteristic with ground glass opacification, particularly in the right middle lobe and lingula, accompanied by air trapping and mosaicism. Blood for surfactant protein gene mutations can diagnose surfactant protein B and C deficiency, ATP-binding cassette transporter A3 and thyroid transcription factor-1 (NKX2.1) gene abnormalities.
Congenital thoracic malformations, particularly cystic ones, are usually asymptomatic and diagnosed antenatally during fetal abnormality ultrasound scanning. However congenital lobar emphysema may cause neonatal respiratory distress, and while symptoms may be present at birth or appear within the first 48 h, in some cases tachypnoea does not develop for 1–4 months. Furthermore, although usually obvious on a plain chest radiograph, a case has been reported in which the lesion was only apparent on a CT scan. Rarely, forms of spontaneous pulmonary interstitial emphysema have been seen with minimal respiratory symptoms, including tachypnoea, in a full term non-ventilated baby; a chest radiograph and CT scan indicate the diagnosis.
Pulmonary Hypoplasia. This is rarely an isolated phenomenon (primary) and more commonly is secondary and associated with disorders of lung growth (eg, severe oligohydramnios, CDH, Ebstein's malformation of the tricuspid valve). Patients may present in early infancy, and the severity depends on the degree of hypoplasia; persistent tachypnoea and breathlessness with activity/exercise are the principle symptoms when the hypoplasia is not too severe. When unilateral, the thorax is asymmetrical, with reduced air entry and underexpansion on that side. Confirmation can usually be made with a chest radiograph or a chest CT scan. With normal radiology, infant lung function testing may be necessary which would indicate reduced lung volumes and reduced functional residual capacity. If right sided, the pulmonary vasculature must be visualised because of the association with Scimitar syndrome (partial or complete anomalous pulmonary venous drainage into the inferior vena cava, commonly associated with persistent left superior vena cava, dextrocardia, pulmonary sequestration and right pulmonary hypoplasia). The infantile form of Scimitar tends to present in the first 2 months with tachypnoea, as well as recurrent pneumonia, failure to thrive and heart failure.
Congenital Diaphragmatic Hernia. This lesion is often diagnosed antenatally or within hours or days of birth. However late-presenting (>1 month) CDH is well recognised, and a review of these late diagnoses found 65% of right sided and 42% left sided CDH presented within the 1st year of life. Tachypnoea was the most common symptom, followed by vomiting. Diagnosis may be made on a chest radiograph but is not always obvious; chest CT or a contrast gastrointestinal study may be necessary.
Diaphragmatic Weakness. Compared with adults, the diaphragm is critical to respiration in infancy due to the fact the chest wall is so compliant, the mediastinum is more mobile and the intercostal muscles are weaker. Even unilateral diaphragmatic weakness can cause a degree of respiratory distress. At this age, phrenic nerve injury is the most common cause. When due to a difficult delivery, for example, following shoulder dystocia, the majority of infants with phrenic nerve palsy also have a brachial plexus injury (Erb's palsy). A number of congenital neuromuscular disorders can cause severe diaphragmatic weakness. One of them, spinal muscular atrophy with respiratory distress (SMARD1) is very rare and unlike more typical spinal muscular atrophies, presents with respiratory distress before distal muscular weakness is obvious. The respiratory difficulty is due to diaphragmatic weakness followed by paralysis (more usually on the right side initially), but it is usually accompanied by a weak cry and stridor. A chest radiograph may indicate an abnormal position of a hemidiaphragm. An ultrasound or fluoroscopic examination of the diaphragms can demonstrate abnormal movements, especially if paradoxical or weak/paralysed.
H-type Tracheo-oesophageal Fistula. It is likely that as well as tachypnoea, the child would have marked symptoms on feeding, usually coughing, choking, turning blue and potentially recurrent lung infections. A tube oesophagram (video oesophagography) and/or bronchoscopy may be necessary to make the diagnosis, however.
Upper airway narrowing may be obvious due to the presence of significant or persisting stridor, especially if the narrowing is more than mild. Possible causes include laryngotracheomalacia, bronchomalacia, laryngeal or tracheal web, subglottic stenosis. Tachypnoea accompanied by noisy breathing is an indication for a bronchoscopy (flexible or rigid).
Nasal Obstruction. Infants are obligate nose breathers for several months. Nasal obstruction, when bilateral, can cause significant respiratory distress in the neonatal period, and intubation may be required, for example, bilateral choanal atresia. However unilateral obstruction may present later (typically at 5–24 months), and with milder symptoms; unilateral atresia is more common than bilateral and accounts for up to 75% cases of atresia. Additionally symptoms will be milder if it is a stenosis rather than complete atresia. Techniques for diagnosis include placing a cold mirror/metal spoon under the nostril to look for condensation, passing a small nasogastric tube, or putting a few drops of saline in the nostril and looking for bubbles.
After careful examination by the cardiologist, inevitably children will have an ECG and echocardiogram performed to exclude a number of potential cardiac diagnoses. It is important to be aware that major cardiovascular disease may present initially during infancy with just mild tachypnoea. With increasing symptoms of tachypnoea and recurrent chest infections, cardiac disorders may masquerade as respiratory disease. Many causes are 'silent' meaning there is no murmur, so the diagnosis is not always obvious without assessment by a cardiologist (Box 3 and Box 4).
Tachypnoea during infancy without a heart murmur can occasionally be caused by a large atrial septal defect, pulmonary vein stenosis, cor triatriatum, mitral stenosis, hypertrophic cardiomyopathy and coarctation of the aorta. Transient neonatal myocardial ischaemia complicating birth asphyxia, anomalous origin of a coronary artery from the pulmonary trunk, dilated cardiomyopathy and myocarditis will manifest 'T' wave abnormalities and ischaemia or infarction on an ECG.
'Silent' heart disease in infants with pulmonary hypertension and a persistent elevation of pulmonary vascular resistance for several weeks may sometimes be associated with a large ventricular septal defect, complete atrioventricular septal defect (especially in babies with Down's Syndrome), large patent ductus arteriosus and common mixing situations in which mild arterial oxygen desaturation is not clinically obvious. Infants without heart disease may manifest a failure of a fall in pulmonary vascular resistance after birth, leading to mild tachypnoea, which can be a mild form of persistent pulmonary hypertension of the newborn. Almost all of these infants with pulmonary hypertension will have a prominent precordial impulse, loud pulmonary component of the second heart sound, right ventricular hypertrophy on an ECG, and cardiomegaly with or without pulmonary venous congestion on a chest radiograph.
Whatever the cardiac anomaly, a good quality echocardiogram will usually provide a complete diagnosis. When tachypnoea without obvious stridor results from a vascular ring or pulmonary artery sling, a CT angiogram is also helpful in making the diagnosis.
Gastro-oesophageal reflux is thought to cause tachypnoea, presumably due to discomfort from oesophagitis, but it would need to be quite severe to cause persistent symptoms; the child would not necessarily be vomiting. A pH study should be diagnostic, and in an infant a dual probe study is preferable in order to take account of any buffering of stomach acid by frequent milk feeds.
Recurrent aspiration of fluid (eg, milk, saliva) can sometimes be silent, so the baby does not necessarily cough, splutter or choke when drinking. It is often idiopathic, sometimes associated with a bulbar palsy, and occasionally anatomical (eg, laryngeal cleft). Diagnosis is made by a speech therapist's clinical assessment, sometimes followed by a videofluoroscopic swallowing study.
Particular consideration in babies with Down's syndrome should be given to congenital heart disease, infection, upper airway anomalies (narrow trachea, laryngomalacia, tracheomalacia and bronchomalacia), aspiration due to gastro-oesophageal reflux or swallowing abnormalities.
Potential Causes of Tachypnoea—When the Diagnosis Is Not Immediately Obvious
There are numerous causes of tachypnoea in term infants (reviewed by Sasidharan). Often the tachypnoea is just one of several signs in a clearly unwell child, examples include, a baby with a metabolic acidosis for example from numerous rare metabolic disorders; bacterial sepsis; or significant pain, for example, from a volvulus. In some children, the cause is obvious on initial assessment, from the history, for example, narcotic withdrawal and postbirth asphyxia. In some, it may be determined on first examination, for example, the small thorax of Jeune asphyxiating thoracic dystrophy, bell-shaped chest from pulmonary hypoplasia, hypotonia associated with neurological or neuromuscular disease, stridor due to upper airway obstruction or even severe neonatal rickets.
Below are some causes to consider in a child who seems well, has a normal clinical examination, but is without an immediately obvious diagnosis, with the relevant investigations that may provide the answer.
Respiratory and Upper Airway
Infection. It is likely the child would have other symptoms and signs, particularly fever and cough, nevertheless, low grade or chronic infection must be considered. A nasopharyngeal aspirate for respiratory viruses and a cough swab for bacterial culture, and possibly a white cell count and C reactive protein may be helpful. Pulmonary tuberculosis has been described in children under 1 year, with tachypnoea the predominant sign, and not all patients had a contact history, cough or abnormal radiograph, although most did.
Cystic Fibrosis. In the UK and many other countries, newborn screening means babies are diagnosed with cystic fibrosis (CF) at around 3–4 weeks of age; however screening is not infallible. While most babies are symptom-free from the respiratory perspective, the majority have suboptimal weight gain, often with abnormal stools. Infants can present with tachypnoea, recurrent cough and sometimes wheeze, but our experience is that it is most unusual for tachypnoea to be the sole symptom in a baby with CF. Nevertheless it must be considered and a sweat test performed if appropriate.
Interstitial Lung Disease. This is a heterogeneous group of rare diseases, most often accompanied by crackles, recession, hypoxaemia and eventually failure to thrive. However in some, tachypnoea is the only obvious symptom, and the severity of symptoms and signs varies. Consideration should be given to neuroendocrine cell hyperplasia, previously known as persistent tachypnoea of infancy; it is often associated with recession, crackles in the chest and sometime hypoxia. There is an airway obstruction element to the condition, but the prognosis is generally good, with symptoms resolving at a median of 18 months (range 6–60 months), although in practice it may be even longer. Inherited surfactant protein C deficiency, ATP-binding cassette transporter A3 and thyroid transcription factor-1 are important, although again other signs of respiratory distress are likely to be present. Surfactant protein B deficiency is lethal in neonates so is unlikely to present with just tachypnoea. A chest CT scan can be highly suggestive, although diagnostic certainty may require a lung biopsy. In cases of neuroendocrine cell hyperplasia, the appearance is quite characteristic with ground glass opacification, particularly in the right middle lobe and lingula, accompanied by air trapping and mosaicism. Blood for surfactant protein gene mutations can diagnose surfactant protein B and C deficiency, ATP-binding cassette transporter A3 and thyroid transcription factor-1 (NKX2.1) gene abnormalities.
Congenital thoracic malformations, particularly cystic ones, are usually asymptomatic and diagnosed antenatally during fetal abnormality ultrasound scanning. However congenital lobar emphysema may cause neonatal respiratory distress, and while symptoms may be present at birth or appear within the first 48 h, in some cases tachypnoea does not develop for 1–4 months. Furthermore, although usually obvious on a plain chest radiograph, a case has been reported in which the lesion was only apparent on a CT scan. Rarely, forms of spontaneous pulmonary interstitial emphysema have been seen with minimal respiratory symptoms, including tachypnoea, in a full term non-ventilated baby; a chest radiograph and CT scan indicate the diagnosis.
Pulmonary Hypoplasia. This is rarely an isolated phenomenon (primary) and more commonly is secondary and associated with disorders of lung growth (eg, severe oligohydramnios, CDH, Ebstein's malformation of the tricuspid valve). Patients may present in early infancy, and the severity depends on the degree of hypoplasia; persistent tachypnoea and breathlessness with activity/exercise are the principle symptoms when the hypoplasia is not too severe. When unilateral, the thorax is asymmetrical, with reduced air entry and underexpansion on that side. Confirmation can usually be made with a chest radiograph or a chest CT scan. With normal radiology, infant lung function testing may be necessary which would indicate reduced lung volumes and reduced functional residual capacity. If right sided, the pulmonary vasculature must be visualised because of the association with Scimitar syndrome (partial or complete anomalous pulmonary venous drainage into the inferior vena cava, commonly associated with persistent left superior vena cava, dextrocardia, pulmonary sequestration and right pulmonary hypoplasia). The infantile form of Scimitar tends to present in the first 2 months with tachypnoea, as well as recurrent pneumonia, failure to thrive and heart failure.
Congenital Diaphragmatic Hernia. This lesion is often diagnosed antenatally or within hours or days of birth. However late-presenting (>1 month) CDH is well recognised, and a review of these late diagnoses found 65% of right sided and 42% left sided CDH presented within the 1st year of life. Tachypnoea was the most common symptom, followed by vomiting. Diagnosis may be made on a chest radiograph but is not always obvious; chest CT or a contrast gastrointestinal study may be necessary.
Diaphragmatic Weakness. Compared with adults, the diaphragm is critical to respiration in infancy due to the fact the chest wall is so compliant, the mediastinum is more mobile and the intercostal muscles are weaker. Even unilateral diaphragmatic weakness can cause a degree of respiratory distress. At this age, phrenic nerve injury is the most common cause. When due to a difficult delivery, for example, following shoulder dystocia, the majority of infants with phrenic nerve palsy also have a brachial plexus injury (Erb's palsy). A number of congenital neuromuscular disorders can cause severe diaphragmatic weakness. One of them, spinal muscular atrophy with respiratory distress (SMARD1) is very rare and unlike more typical spinal muscular atrophies, presents with respiratory distress before distal muscular weakness is obvious. The respiratory difficulty is due to diaphragmatic weakness followed by paralysis (more usually on the right side initially), but it is usually accompanied by a weak cry and stridor. A chest radiograph may indicate an abnormal position of a hemidiaphragm. An ultrasound or fluoroscopic examination of the diaphragms can demonstrate abnormal movements, especially if paradoxical or weak/paralysed.
H-type Tracheo-oesophageal Fistula. It is likely that as well as tachypnoea, the child would have marked symptoms on feeding, usually coughing, choking, turning blue and potentially recurrent lung infections. A tube oesophagram (video oesophagography) and/or bronchoscopy may be necessary to make the diagnosis, however.
Upper airway narrowing may be obvious due to the presence of significant or persisting stridor, especially if the narrowing is more than mild. Possible causes include laryngotracheomalacia, bronchomalacia, laryngeal or tracheal web, subglottic stenosis. Tachypnoea accompanied by noisy breathing is an indication for a bronchoscopy (flexible or rigid).
Nasal Obstruction. Infants are obligate nose breathers for several months. Nasal obstruction, when bilateral, can cause significant respiratory distress in the neonatal period, and intubation may be required, for example, bilateral choanal atresia. However unilateral obstruction may present later (typically at 5–24 months), and with milder symptoms; unilateral atresia is more common than bilateral and accounts for up to 75% cases of atresia. Additionally symptoms will be milder if it is a stenosis rather than complete atresia. Techniques for diagnosis include placing a cold mirror/metal spoon under the nostril to look for condensation, passing a small nasogastric tube, or putting a few drops of saline in the nostril and looking for bubbles.
Cardiac
After careful examination by the cardiologist, inevitably children will have an ECG and echocardiogram performed to exclude a number of potential cardiac diagnoses. It is important to be aware that major cardiovascular disease may present initially during infancy with just mild tachypnoea. With increasing symptoms of tachypnoea and recurrent chest infections, cardiac disorders may masquerade as respiratory disease. Many causes are 'silent' meaning there is no murmur, so the diagnosis is not always obvious without assessment by a cardiologist (Box 3 and Box 4).
Tachypnoea during infancy without a heart murmur can occasionally be caused by a large atrial septal defect, pulmonary vein stenosis, cor triatriatum, mitral stenosis, hypertrophic cardiomyopathy and coarctation of the aorta. Transient neonatal myocardial ischaemia complicating birth asphyxia, anomalous origin of a coronary artery from the pulmonary trunk, dilated cardiomyopathy and myocarditis will manifest 'T' wave abnormalities and ischaemia or infarction on an ECG.
'Silent' heart disease in infants with pulmonary hypertension and a persistent elevation of pulmonary vascular resistance for several weeks may sometimes be associated with a large ventricular septal defect, complete atrioventricular septal defect (especially in babies with Down's Syndrome), large patent ductus arteriosus and common mixing situations in which mild arterial oxygen desaturation is not clinically obvious. Infants without heart disease may manifest a failure of a fall in pulmonary vascular resistance after birth, leading to mild tachypnoea, which can be a mild form of persistent pulmonary hypertension of the newborn. Almost all of these infants with pulmonary hypertension will have a prominent precordial impulse, loud pulmonary component of the second heart sound, right ventricular hypertrophy on an ECG, and cardiomegaly with or without pulmonary venous congestion on a chest radiograph.
Whatever the cardiac anomaly, a good quality echocardiogram will usually provide a complete diagnosis. When tachypnoea without obvious stridor results from a vascular ring or pulmonary artery sling, a CT angiogram is also helpful in making the diagnosis.
Gastrointestinal
Gastro-oesophageal reflux is thought to cause tachypnoea, presumably due to discomfort from oesophagitis, but it would need to be quite severe to cause persistent symptoms; the child would not necessarily be vomiting. A pH study should be diagnostic, and in an infant a dual probe study is preferable in order to take account of any buffering of stomach acid by frequent milk feeds.
Recurrent aspiration of fluid (eg, milk, saliva) can sometimes be silent, so the baby does not necessarily cough, splutter or choke when drinking. It is often idiopathic, sometimes associated with a bulbar palsy, and occasionally anatomical (eg, laryngeal cleft). Diagnosis is made by a speech therapist's clinical assessment, sometimes followed by a videofluoroscopic swallowing study.
Trisomy 21
Particular consideration in babies with Down's syndrome should be given to congenital heart disease, infection, upper airway anomalies (narrow trachea, laryngomalacia, tracheomalacia and bronchomalacia), aspiration due to gastro-oesophageal reflux or swallowing abnormalities.
Source...