Neuromuscular cough


Children with neuromuscular diseases such as spinal muscular atrophy, Duchenne muscular dystrophy, cerebral palsy, cervical spine injuries, mitochondrial myopathy, and other hypotonic disorders of unknown etiology may lack sufficient inspiratory muscle strength to generate a large volume of inhaled air into the lungs. 

As a result, the lungs are not fully expanded to maximal capacity. More critical, however, is decreased expiratory-muscle strength, leading to reduced dynamic airway compression and diminished expiratory pressures and flow rates.


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Spirometry and plethysmography are essential components of routine assessment that will enable the clinician to determine the child’s respiratory sufficiency by tracking vital capacity, forced expiratory volume in one second and forced vital capacity (FEV1/FVC) ratios, maximum inspiratory pressure (MIP), and maximum expiratory pressure (MEP). The clinician also should ask the patient to cough with as much force as possible during the evaluation to hear the strength and effectiveness of the cough.19 


The absence of an effective cough can be dangerous, possibly resulting in atelectasis, pneumonia, and respiratory failure. Protussive mechanical aids are essential in the daily management of neuromuscular disease to enhance airway clearance.20 

Chest physiotherapy by means of manual cuffing, vibratory wand, or a high-frequency chest compression vest helps to move mucus and fluid into the central airways. Acapella and Flutter devices do not work as well for this purpose because the patient may lack sufficient oral-muscle strength to form a seal, and cannot generate the pressures needed for the device to operate. 

Insufflation/exsufflation therapy simulates a cough by using pre-set positive pressure to push air into the lungs through a face mask, followed rapidly by negative pressures to pull air out. Suction equipment is then necessary to clean the debris from the oropharynx.


Biphasic positive airway pressure (BiPAP) delivered through a face mask, a nasal mask, or nasal pillows can be used to permit lung rest, recruit atelectatic alveoli, and enhance ventilation. Frequently used at night during sleep, BiPAP is beneficial during acute illnesses and during naps for rest. 


Tracheostomy is an invasive option for providing a means for chronic ventilation and airway clearance with deep suctioning. Long-term expectations and personal desires for end-of-life interventions must be discussed with patients and their families before pursuing tracheostomy.19



Pertussis


Pertussis, also called whooping cough, most commonly affects infants and young children, and can be fatal in children younger than age 1 year. This bacterial infection is caused byBordetella pertussis, a non-motile coccobacillus that is transmitted by means of aerosolized droplets; transmission is from human to human only.

 As is the case with many respiratory pathogens,B. pertussisattaches to the respiratory tract, starting in the nasopharynx and migrating distally down to the terminal bronchioles, where it becomes invasive and can be found in alveolar macrophages. B. pertussiscreates a toxin that paralyzes the cilia and causes inflammation of the respiratory tract.21 The infection causes excessive secretions of mucus, pus, and even blood.

Pertussis begins with a catarrhal phase that may last one to two weeks. The catarrhal phase is indistinguishable from other respiratory infections, with the patient experiencing runny nose, low-grade fever, and cough. The infection is most contagious at this phase. 


The second phase of pertussis is known as the paroxysmal phase because it is characterized by paroxysms of coughing—rapid, numerous coughing fits, with or without an inspiratory whoop. This phase may last from one week up to six to 10 weeks.

Coughing may last many weeks longer as the illness enters the final, convalescent phase.21 Cough overall improves, but the infected patient remains highly susceptible to other respiratory infections, during which the coughing paroxysms can return.


Testing for pertussis is notoriously difficult and will only be detected during the first three weeks of infection, when it might not even yet be suspected. Nasopharyngeal culture is the gold standard, but the incidence of false-negative results increases after two weeks of infection. Polymerase chain reaction amplification is quite sensitive, and can detect illness in the first three weeks of infection.

 In infants and unvaccinated persons, the test may be effective through four weeks of illness.22 Serologic testing can detect infection that has been present up to eight weeks, but no commercially available test exists. Only the Centers for Disease Control and Prevention and the Massachusetts state public health laboratory have a validated assay for pertussis.23

Clinicians must have a high index of suspicion for pertussis. The CDC has a working definition of pertussis that focuses on the character of the cough: “A cough illness lasting at least two weeks with one of the following: paroxysms of coughing, inspiratory ‘whoop,’ or post-tussive vomiting, without other apparent cause.” Both laboratory-confirmed cases and probable cases fitting the definition are reportable to the CDC.21

The macrolide antibiotics are the first-line treatment for pertussis. Azithromycin (Zithromax, Zmax), clarithromycin (Biaxin, Prevpac), and erythromycin are all acceptable; sulfa drugs can be used in patients who are allergic to the macrolides. Isolation is recommended for the patient until he or she has completed five days of antibiotics. Consider administration of a course of antibiotics to persons in close contact with the patient within three weeks of exposure.