**3. Coordination of breathing and swallowing**

mechanism of airway protection. This may be altered in patients who have lung diseases such as chronic obstructive pulmonary disease (COPD) [2, 3]. COPD is a preventable and treatable disease characterized by progressive limitation of airflow that is usually associated with an abnormal inflammatory response of the lungs to noxious particles and gases [4, 5]. COPD is a major public health problem with high and increasing prevalence [4]. According to World Health Organization (WHO) estimates, 80 million people have moderate to severe COPD [6]. Pulmonary changes can be a detrimental factor to coordination between breathing and swallowing [2, 3, 7, 8]. Swallowing apnea requires a reorganization of the breathing pattern when swallowing. This can be limited by the typical respiratory changes observed in patients

This chapter discusses the history and current state of our knowledge concerning dysphagia in chronic obstructive pulmonary disease. We also describe the development of instrumenta‐ tion for the analysis of the swallowing apnea and preliminary results of this analysis in

**•** First we will provide a brief description of dysphagia and the interaction between swal‐

**•** Next, we describe the main results presented in the literature concerning the dysphagia in

**•** The development of instrumentation for analysis of swallowing apnea, performed in our

**•** Preliminary results of the changes of swallowing apnea in individuals with COPD are

**•** Finally, we conclude by examining the potential role of the routine analysis of swallowing

Swallowing is a complex sensoriomotor function that depends on the integrity of the mecha‐ noreceptors and chemoreceptors for the sequential stimulation and inhibition of the upper aerodigestive tract; this coordinated process transports foods and liquids through the mouth

Biomechanical events that contribute to secure bolus transport and airway protective mecha‐ nisms include: closure of the introitus to the trachea by vocal cord adduction, approximation of the adducted arytenoids to close the laryngeal aditus, epiglottal descent, antero-superior displacement of the larynx away from the path of the bolus, and opening of the upper oesophageal sphincter [11]. During swallowing, the closure of the larynx and the respiratory pause during swallowing are vital protective mechanisms that prevent aspiration [12]. This

and pharynx to the esophagus [10] and simultaneously protect the upper airway [1].

**•** In section 4, we describe the principles of the chronic obstructive pulmonary disease;

individuals with COPD. The main topics covered by this review will be as follows:

lowing and breathing in section 2 and 3, respectively;

laboratory, is presented in section 5;

disorders in COPD in the clinical arena.

phenomena is describes schematically in Figure 2.

described in section 6;

with COPD [9].

202 Seminars in Dysphagia

COPD;

**2. Dysphagia**

Recent findings have delineated single neurons within medullary networks that demonstrate multifunctionality in the control of both the respiratory and swallowing behaviours [16]. The breathing cycle is not simply repressed during swallowing; it is substituted by a different wellcontrolled behaviour pattern. Variations in the bolus volume and viscosity characteristics will interfere with the breathing stop time duration [9, 17, 18]. The consistency of these observations has led to speculation that the precise coordination of breathing and swallowing may be an important mechanism to prevent aspiration [19]. The effect of bolus volume influences the swallowed-associated respiratory cycle [9, 20], and this observation notes that these neuro‐ logical interference engrams may contribute to dyspnoea during meals in some patients with pulmonary disease.

Deglutition apnea is described as an important mechanism of airway protection. It consists of a respiratory pause that occurs involuntarily during each swallow, when the respiratory muscles are centrally inhibited and the airway closes. Breathing ceases just before and during the entire pharyngeal phase of deglutition [3]. The duration of this brief swallow apnea rages between 1 and 2 seconds in liquid swallows in most healthy adults, but there is a variability in the timing depending on the swallow task and bolus viscosity [1, 19, 21, 22].

Deglutition apnea occurs mainly during expiration and is followed by expiration [1, 2, 9, 18-25]. This pattern occurs more often in the presence of a bolus [9, 20]. A different pattern of this coordination of breathing and swallowing, for example, inspiration after swallowing, may increase the risk of aspiration and place patients at an airway protective disadvantage [1].

A modification to the stable respiratory-swallow occurs during advanced ageing. In healthy elderly aged individuals, the duration of deglutition is higher than in young groups [1, 18]. Studies have shown a greater occurrence of liquid swallow initiated and followed by the inspiratory phase of respiration [22, 26]. These pattern changes have not been associated with aspiration, however, they may cause implications on airway protection or bolus clearance in patients with already compromised swallowing function secondary to diseases and other conditions during old age, head and neck cancer, stroke and chronic obstructive pulmonary disease [1].
