Keywords
pulmonary disease - deglutition - deglutition disorders
Introduction
Chronic obstructive pulmonary disease (COPD) is characterized by chronic airflow limitation
leading to pathologic alterations in the lungs with consequent extrapulmonary effects.
It is not a completely reversible disease, generating systemic complications and comorbidities
that contribute to the worsening of the disease and that can lead to death.[1]
[2] Its principal etiologic factors include the inhalation of particles or gases; exposure
to smoking, occupational dust, chemical irritants; and socioeconomic conditions, among
others.[3]
One symptom manifested by COPD is coughing, which can occur daily or intermittently,
and another is dyspnea, which is associated with disability in activities of daily
living and decreased quality of life, progressing as the disease worsens.[4] These factors exacerbate the disease, because they result in worse gas exchange
and pulmonary hemodynamics.
Furthermore, COPD might affect the dynamics and coordination of other important functions
such as deglutition.[5] Deglutition is considered both a dynamic and a complex process; it has the function
of transporting the bolus from the mouth to the stomach in a safe manner. At the time
the food is swallowed, a pause in breathing occurs for a few seconds, and the breath
returns in the expiratory phase, thereby avoiding aspiration episodes.[6]
Difficulties resulting from respiratory and/or ventilatory pattern might alter this
coordination, resulting in decreased protection of the lower airway as may occur in
patients with COPD due to ventilatory functional alterations and thoracoabdominal
biomechanics, which can lead to difficulties in swallowing process called dysphagia.[5] Dysphagia refers to changes during swallowing, which may involve any of the stages of this
process; however, the alteration of the pharyngeal phase of swallowing might result
in the entry of food into the airway, causing laryngeal penetration, laryngotracheal
aspiration, pulmonary problems, undernutrition, dehydration, or aspiration pneumonia
and might even lead to death.[7]
[8]
[9]
The literature presents studies that relate COPD to dysphagia, suggesting that the
laryngeal aspiration phenomenon, related to the alteration in the pharyngeal phase
of swallowing, contributes significantly to the exacerbation of the symptoms of lung
disease,[6]
[10] in addition to causing more frequent hospitalizations.[11] Abnormalities in the swallowing process are associated with frequent exacerbations
in patients with COPD.[12] However, it is unclear whether these abnormalities may already be found in patients
with mild degree of disease.[13]
It is known that adequate protective reflexes of the airway have an important role
in the aspiration prevention, whereas the impairment in the swallowing reflex may
become a potential risk factor for exacerbations of COPD.[10]
The purpose of this literature review was to investigate the relation between dysphagia
and exacerbations of COPD.
Methods
The National Library of Medicine (Medline), Library Online (SciELO), Literatura Latino-Americana
e do Caribe (Lilacs), Physiotherapy Evidence Database (PEDro), and U.S. National Library
of Medicine National Institutes of Health (PubMed) databases were searched for articles
published from November 2012 to March 2013. Search descriptors “DPOC,” “Deglutição,”
and “Transtornos de Deglutição” and their corresponding English “pulmonary disease,”
“deglutition,” and “deglutition disorders” were used. The search was limited to Portuguese
and English languages and studies performed with adults with COPD of both genders,
published between 2000 and 2013. Studies outside the stipulated period were excluded.
Titles and abstracts were analyzed to obtain potentially relevant articles for review
and in accordance with the proposed purpose in the present study.
From the methodology applied, 16 studies were found, of which 14 were included in
this review. The reviewed articles were organized in the following categories: (1)
considerations about the COPD and (2) dysphagia and exacerbations in COPD.
Literature Review
Considerations in Chronic Obstructive Pulmonary Disease
The World Health Organization estimates that through 2030 the mortality and disability
caused by COPD will increase significantly. Estimates suggest that ∼5.5 million people
have the disease in Brazil, and it is a major cause of deaths in the country. Tobacco
use is responsible for 80 to 90% of cases,[14] and its chronic use is associated with decreased pulmonary function. In addition
to cigarette smoke, inhalation of particles and toxic gases, such as smoke from the
firewood, irritating gases, and occupational exposure, have a direct relation to the
development and maintenance of airway obstruction.[15]
For pneumology and physical therapy, the gold standard instrument for disease diagnosis
is spirometry, which observes the restriction to airflow before and after bronchodilator
use. The most important parameters in view of clinical application are the forced
vital capacity (FVC), forced expiratory volume in 1 second (FEV1), and FEV1-to-FVC ratio. The FEV1-to-FVC ratio after bronchodilator must be reduced (i.e., less than 80% predicted).[16]
The degree of severity of the disease is determined by clinical characteristics and
the airflow limitation. Mild COPD (stage I) is characterized by mild airflow limitation
(FEV1/FVC < 70%, but FEV1 ≥ 80% of predicted), and at this stage the individual may not be aware that their
lung function is abnormal; moderate COPD (stage II) occurs with worsening of airflow
limitation (30% ≥ FEV1 < 70% of predicted and FEV1 ≥ 80% of predicted), and dyspnea becomes more intense to efforts; in severe disease
(stage III), FEV1/FVC < 70% or FEV1 > 50% of predicted plus respiratory insufficiency or clinical signs of right ventricular
failure are evident.[16]
The concept of COPD involves two entities, pulmonary emphysema and chronic bronchitis.
Pulmonary emphysema may be defined as a chronic obstructive process, resulting in
important alterations to the whole structure distal to the terminal bronchioles, called
lobes, leading to accumulation of air in the lungs, condition called pulmonary hyperinflation.[17]
Already chronic bronchitis is a clinical condition characterized by excessive secretion
in the bronchial tree, the presence of chronic or recurrent cough, with expectoration
for the least 3 consecutive months of the year and 2 consecutive years.[18] Physiopathology of chronic bronchitis involves the destruction of the lung parenchyma,
causing pulmonary hyperinflation that leads to increased airflow obstruction and reduced
lung elastic recoil.[19]
[20] Hyperinflation, due to alterations of the respiratory muscles, interferes in diaphragmatic
excursion, which modifies the disposition of thoracic wall,[21] reflecting an abnormal movement between the thorax and abdomen.
The mechanical disadvantage found in patients with COPD leads to recruitment of accessory
muscles of inspiration and compromises diaphragm performance, which becomes rectified
and decreases apposition area, thereby restricting its excursion.[22] Wouters emphasized that the clinical manifestations of COPD extend beyond the lung
issues, given the impact on general health by the influence of systemic manifestations,
such as the incoordination of the swallowing function.[23]
Dysphagia and Exacerbations in Chronic Obstructive Pulmonary Disease
Swallowing is didactically divided into four phases: oral preparatory, proper oral,
pharyngeal, and esophageal. The first two stages correspond to the preparation of
food in the oral cavity by chewing (incision, mastication, and pulverization), associated
with saliva to form the alimentary bolus, and the transport of the alimentary bolus
toward the pharynx. In the pharyngeal phase, food is transported to the esophagus
and involves a series of involuntary events for protection of the lower airway, which
is the most important phase. The esophageal phase corresponds to the bolus transport
to the stomach.[24]
Dysphagia is characterized by any difficulty during the swallowing stage that prevents
the proper conduct of the alimentary bolus from the oral cavity to the stomach.[9] To verify the presence and severity of the swallowing disorder, after clinical evaluation
speech-language pathologists often classify the swallowing dynamics according to the
occurrence of clinical findings. The Dysphagia Risk Evaluation Protocol classifies
swallowing at different levels ranging from level I (normal swallowing) to level VII
(severe dysphagia); speech-language treatment is performed according to classification.[25]
It is noteworthy that dysphagia is not only detected by clinical evaluation due to
the absence of clinical signs; sometimes it is necessary to objectively examine swallowing
to verify aspirations that occur silently, with videofluoroscopy as the gold standard
examination in this case.[26]
The lack of coordination of these movements is related to the presence of laryngeal
penetration (i.e., the entry of secretions, food, or liquid above the level of the
vocal folds and/or laryngotracheal aspiration, which happens with entry of any substance
below the level of the vocal folds and can lead to aspiration pneumonia).[5]
[26] Subjects with COPD are more susceptible to present this dyssynchrony.[5]
COPD has the potential to alter the coordination between swallowing and breathing
due to dyspnea and abnormalities of thoracoabdominal biomechanics, which negatively
influences the normal process of swallowing of these individuals; they do not realize
the respiratory pause that is observed in a process of normal swallowing, increasing
the risk of penetration of the content into the pharynx.[27] Some authors suggest that the presence of dysphagia may be one factor that initiates
the exacerbation of COPD, especially when the incoordination of the swallowing reflex
occurs with consequent laryngeal aspiration.[10]
[28]
Exacerbations characterize the acute worsening of COPD symptoms, accelerating the
decline in lung function and compromising the quality of life of patients,[29]
[30] because they increase the demand for doctor visits, hospitalization, and treatment
costs. They can also contribute to airway inflammation and may present incomplete
recovery and contribute to the decline of FEV1, which in these patients is already at reduced values.[31]
[32]
Proper coordination between breathing and swallowing events is essential for human
survival, ensuring effective hydration and nutrition and preventing pulmonary aspiration.[33] Dysphagia may be the result of various disorders and diseases. Respiratory impairment
itself leads the individual to have a higher energy expenditure, which can lead to
weight loss and undernutrition. Swallowing disorders can also lead to other complications,
including dehydration, aspiration pneumonia, or airway obstruction.[34]
Strength and respiratory muscle endurance are reduced in patients with COPD, because
of hyperinflation, poor nutrition, and general deconditioning of the muscles that
lead to increased work of breathing.[35] The systemic effects of the disease go beyond the lung impairments. Pulmonary obstruction
is caused by different pathophysiological factors that lead to hyperinflation of the
lung.[36]
Decline in lung function leads to diaphragmatic mobility reduction,[37] and changes in diaphragmatic excursion alter the provision of thoracic wall, causing
reverberating abnormal movement between the thorax and abdomen. Patients with COPD
commonly use the accessory muscles of respiration, which shortens the muscles and
makes them tense. This change may reflect the disposition of the larynx and even the
pharynx, damaging the effective process of swallowing.
In a systematic review of the literature conducted by O'Kane and Groher, six of the
seven studies surveyed documented some kind of alteration in the swallowing process
of patients with COPD.[6] Insufficient swallowing accompanied by pulmonary aspiration may be a predictive
factor for exacerbations in patients with COPD. In the same way, disease exacerbations
may be precursors of poor swallowing, suggesting alteration in the swallowing reflex
during exacerbations of the disease.[38]
Discussion
COPD is a lung disease that affects 12% of the population, occurs in subjects mainly
older than 40 years of both genders, and is the fourth to seventh leading cause of
death in Brazil.[21]
[39] It is considered a public health problem that is growing every year. In Brazil,
studies related to COPD epidemiology are scarce when compared with international studies,
but the number of deaths from the disease has been increasing in the past 20 years,
for both genders; mortality based on cause of disease increased ∼340%.[40]
Smoking is a leading cause of COPD, with the frequency of cigarette consumption associated
with greater impairment of lung function and consequent airflow limitation.[21] Soares et al aimed to characterize the population to the risk of COPD and found
that in a sample of 157 subjects, 108 (68,8%) were male with a mean age of 53.85 years;
the researchers also found that the greater amount of cigarettes smoked predominated
in this sex.[3] This finding highlights the need to perform early intervention in this population,
to prevent the development and consequences of long-term COPD.
Some authors suggest that the clinical manifestations of COPD may affect other important
functions such as swallowing, which is justified by the incoordination during apnea
of respiration when food passes through the pharynx.[28] The pharyngeal phase of swallowing is considered the most important, because there
are many occurrences necessary for directing the alimentary bolus movements, such
as elevation and anterior displacement of the larynx, firm glottal closure and lowering
of the epiglottis, along with breathing apnea; that there should be a synchronism
in that movement so that the aliment is not diverted toward the lower airway.[25]
Drozdz et al analyzed the pharyngeal phase of swallowing in subjects with chronic
cough using videofluoroscopy.[41] They found that mild dysphagia occurred in 20% of cases and 13.4% had mild to moderate
or moderate dysphagia. They concluded that this population, despite not presenting
swallowing complaints, has higher aspiration risk due to alteration in breathing pattern
that could lead to lack of coordination between swallowing and breathing.
Bastille et al compared the results of clinical and objective evaluation of swallowing
of a subject diagnosed with COPD.[42] They found that the clinical evaluation of swallowing was normal; however, due to
the presence of chronic cough, videofluoroscopy showed the presence of laryngeal penetration
of the laryngotracheal aspiration, which was silent due to the decreased sensitivity
of the laryngeal region.
In this context, several studies have shown the relation of dysphagia with disease
exacerbation in patients with COPD. In one of these studies, a self-perception questionnaire
was used, and 35 patients in clinical and medication treatment reported the presence
of dysphagia in the pharyngeal and esophageal phases of swallowing.[5]
One study of 61 patients with no history of COPD exacerbations in the previous 4 weeks,
using the repetitive saliva swallowing test (RSST) and the modified water-swallow
test, showed that dysphagia causes exacerbations in COPD subjects; the RSST test was
useful for dysphagia detect associated with exacerbations.[43] Similar findings were found in 2009, when 64 patients with COPD were tested with
the simple two-step swallowing provocation test and the RSST; swallowing dysfunction
could be observed in the mild stage of the disease.[13]
In research conducted in 2007, 50 patients with COPD were evaluated based on the response
latency time of the swallowing reflex, timed from the instillation of 0.03 ounces
of distilled water to the pharynx through a nasal catheter; results indicated impairments
in this reflex, which was significantly associated with disease exacerbation.[10] Similar results were observed in a 2010 study, when 65 patients with COPD who had
episodes of exacerbation recorded over a period of 12 months were assessed using a
self-perception questionnaire; results showed altered swallowing reflex that could
predispose them to disease exacerbations.[12]
Videofluoroscopy was used to evaluate 16 patients, and results suggested that impairments
in swallowing may occur when there is ingestion of large quantities of liquids. Still,
the authors suggested possible association of respiratory pattern with swallowing
disorders.[44] Similar results were evidenced in 2002 in a study that also used videofluoroscopy
to evaluate patient swallowing, which concluded that these patients had abnormal physiology
of swallowing.[45]
Gross et al in their study found that patients with COPD had alterations between the
process of breathing and swallowing, and this alteration may increase the risk of
pulmonary aspiration contributing to disease exacerbations.[28] The evaluation used respiratory inductance plethysmography to track respiratory
signs, as well as the electromyography to score the behavior of the act of swallowing
during each respiratory cycle.
McKinstry et al observed that alterations in the respiratory mechanics of COPD commonly
include swallowing disorders.[46] Research indicates that people with the disease have a propensity to develop oropharyngeal
dysphagia as a consequence of the lack of coordination between breathing and swallowing.
In research conducted by Mokhlesi et al, the starting point was the hypothesis that
patients with COPD have a lower rest position and reduced larynx elevation, which
increases the risk of aspiration.[45] Videofluoroscopy may show these patients have abnormal swallowing, but more studies
are needed to assess the aspirations as a cause of exacerbations.
Previous studies have cited these findings, noting that reduced laryngeal elevation
occurs during the swallowing process and alterations of the cricopharyngeal muscle.
The literature describes that this dysphagia in these patients is related to the lack
of coordination between breathing and swallowing.[33] In a study of 78 patients with COPD, we observed that 85% of them had some degree
of dysphagia.[19]
In a study performed with patients with COPD and gastroesophageal reflux disease,
patients who had daily or weekly symptoms were more prone to exacerbations of the
disease, which may occur due to microaspirations of gastric contents leading to irritation
of the airways. Another mechanism would be to increase intra-abdominal pressure generated
by hyperinflation and increased respiratory effort, which alters the relation between
the diaphragm and the esophageal sphincter.[47]
Thus, it is evident that early detection of the presence of dysphagia, mainly related
to lack of coordination between the functions of swallowing and breathing in subjects
with COPD, may assist in decreasing the disease exacerbation.
Conclusion
In this review, a relationship between the presence of dysphagia and exacerbations
of COPD was noted, as identified by studies demonstrating that the difficulties associated
with swallowing might lead to disease exacerbations. There seems to be a consensus
among authors concerning this relation, so that the main factor for this occurrence
is related by the lack of coordination between the functions of breathing and swallowing,
because subjects with COPD do not perform adequately apnea of breath. However, it
was difficult to compare the studies because methodological differences.
More research to clarify the relation between dysphagia and exacerbations of COPD
is needed; it might then possible to search multidisciplinary strategies to assist
in the treatment of these patients in a comprehensive manner, to cater treatment to
their specific needs due to systemic manifestations of pulmonary disease.
