**7. Preliminary results of the analysis of swallowing apnea in individuals with chronic obstructive pulmonary disease**

This section presents new results concerning the evaluation of swallowing apnea in patients with COPD. This analysis was performed using the instrument described in the previous section. The primary hypothesis is that swallowing apnea in COPD patients is altered during liquid swallowing compared with age-matched healthy subjects.

#### **7.1. Patients and methods**

**Figure 5.** Front panel of the program used to automatically calculate the time in the course of the swallowing apnea (s) and the phase in which the swallowing apnea started and stopped in the respiratory cycle (inspiration or expiration).

Figure 5: Front panel of the program used to automatically calculate the time in the course of the swallowing apnea (s) and the phase in which the swallowing apnea started and

Regardless of the method used for data acquisition (ambulatory or telemonitoring), the final analysis of the airflow, mechanical vibration and glass angle signals is performed by a dedicated software (Figure 5). It allows the user to automatically calculate the time in the course of the swallowing apnea (s) and the phase in which the swallowing apnea started

and stopped in the respiratory cycle (inspiration or expiration).

Representative examples of the typical morphology of the nasal airflow, mechanical vibration and glass angle signals obtained during a swallowing of 20 mL of water in a normal subject

Representative examples of the typical morphology of the nasal airflow, mechanical vibration and glass angle signals obtained during a swallowing of 20 mL of water in a


Figure 6: Typical glass angle, larynx mechanical vibration and nasal airflow normal signal morphology during swallowing of 20 mL of water in a normal (A) and a dysphagic patient (B).

**Figure 6.** Typical glass angle, larynx mechanical vibration and nasal airflow normal signal morphology during swal‐

As seen in Figure 6A, the movement necessary to drive water into the mouth of the volunteer is described by the increase in the glass angle. When the angle is near 900 and water is beginning

As seen in Figure 6A, the movement necessary to drive water into the mouth of the volunteer is described by the increase in the glass angle. When the angle is near 900 and

0 2 4

Arbitrary units

6 8

4 6 8 10 12 14 16 18 20 22 24

Time (s)

Swallowing mark

 Glass angle Larynx vibration Nasal airflow

Apnea

90<sup>O</sup>

Exp

Insp

0O

and a dysphagic patient are presented in Figure 6.

90o

0 1 2 3 4 5 6 7 8 9 10 11 12

lowing of 20 mL of water in a normal (A) and a dysphagic patient (B).

Apnea

Swallowing mark

Exp

Insp

0 o

A


0

1

Arbitrary units

2

3

4

218 Seminars in Dysphagia

stopped in the respiratory cycle (inspiration or expiration).

normal subject and a dysphagic patient are presented in Figure 6.

 Glass angle Larynx vibration Nasal airflow

Time (s) B

The study included a control group formed by eleven healthy subjects and twelve outpatients with COPD. The volunteers initially were analysed using spirometry and plethysmography [48]. This study was approved by the Ethics Committee of the State University of Rio de Janeiro. Informed consent was obtained from all volunteers before inclusion in the study.

The variables studied were: forced expiratory volume in the first second (FEV1), forced vital capacity (FVC), the ratio of forced expiratory volume to forced vital capacity (FEV1 / FVC), forced expiratory flow between 25 and 75% of the FVC curve (FEF 25-75%), total lung capacity (TLC), functional residual capacity (FRC), residual volume (RV) and the ratio of residual volume and total lung capacity (RV / TLC). The exams were performed by swallowing saliva and water at volumes of 5, 10 and 20 mL. Patients were instructed to swallow each volume three times. Twelve swallows of each patient were studied (276 total swallows).

#### **7.2. Results**

Table 2 shows the biometric, spirometric and plethysmographic characteristics of these volunteers. Volunteers in the two groups were comparable considering age, weight and height, showing no statistically significant differences. In general, the pulmonary function parameters were highest in normal subjects and lower in patients.


**Table 2.** Biometric and pulmonary function characteristics of the investigated subjects. Ns: non-significant.

Figure 7 shows that, in contrast with the control subjects (p=ns), the increase of the offered volume resulted in a longer duration of swallowing apnea in patients with COPD (p<0.05).

**Figure 7.** Time interval of swallowing apnea in healthy subjects and patients with COPD for different volumes of wa‐ ter. \* p < 0.02; \*\* p < 0.002 in comparison with the control group.

\*\*

\*

The COPD patients had longer swallowing apnea with volumes of 10 mL (p<0.02) and 20 mL (p<0.002). A higher number of swallows in the pattern of inspiration-apnea-inspiration was observed in the COPD group, especially in the volumes of 10 and 20 mL (Figure 8). different volumes of water. \* p < 0.02; \*\* p < 0.002 in comparison with the control group. The COPD patients had longer swallowing apnea with volumes of 10 mL (p<0.02) and 20 mL (p<0.002). A higher number of swallows in the pattern of inspiration-apnea-inspiration

was observed in the COPD group, especially in the volumes of 10 and 20 mL (Figure 8).

Figure 7: Time interval of swallowing apnea in healthy subjects and patients with COPD for

\*

 Control - ANOVA p=ns COPD - ANOVA p<0.05

Swallowing apnea (s)

Figure 8: Percentage of exhalation-apnea-exhalation (A), inhalation-apnea-exhalation (B), exhalation-apnea-inhalation (C) and inhalation-apnea-inhalation (D) events in healthy (blue) and COPD patients (red) for different water volumes. 276 swallows were studied. **Figure 8.** Percentage of exhalation-apnea-exhalation (A), inhalation-apnea-exhalation (B), exhalation-apnea-inhalation (C) and inhalation-apnea-inhalation (D) events in healthy (blue) and COPD patients (red) for different water volumes. 276 swallows were studied.

#### **7.3. Discussion**

volume and total lung capacity (RV / TLC). The exams were performed by swallowing saliva and water at volumes of 5, 10 and 20 mL. Patients were instructed to swallow each volume

Table 2 shows the biometric, spirometric and plethysmographic characteristics of these volunteers. Volunteers in the two groups were comparable considering age, weight and height, showing no statistically significant differences. In general, the pulmonary function parameters

**COPD**

**n=12 p-value**

three times. Twelve swallows of each patient were studied (276 total swallows).

**Control n=11**

Age (years) 69.8 ± 6.8 71.3± 6.1 ns Weight (kg) 69.98 ± 10.3 61.4 ± 17.4 ns Height (cm) 160.8 ± 9.9 156.9 ± 9.0 ns

FEV1 (%) 106.8 ± 12.7 69.9 ± 29.7 0.001 FVC (%) 103.9 ± 13.0 95.0 ± 24.1 ns FEV1/CVF 81.2 ± 4.00 56.1 ± 16.1 <0.0001 FEF25-75(%) 117.0 ± 24.5 34.3 ± 24.9 <0.0001 TLC (%) 100.7 ± 6.5 114.0 ± 9.4 <0.0001 FRC (%) 86.3 ± 14.1 112.7 ± 2.2 0.003 RV (%) 98.9 ± 14.1 148.5 ± 38.6 <0.0001 RV/TLC 39.9 ± 6.40 52.9 ± 10.8 0.0003

**Table 2.** Biometric and pulmonary function characteristics of the investigated subjects. Ns: non-significant.

Figure 7 shows that, in contrast with the control subjects (p=ns), the increase of the offered volume resulted in a longer duration of swallowing apnea in patients with COPD (p<0.05).

**Figure 7.** Time interval of swallowing apnea in healthy subjects and patients with COPD for different volumes of wa‐

ter. \* p < 0.02; \*\* p < 0.002 in comparison with the control group.

) 24.7 ± 5.5 27.0 ± 2.8 ns

were highest in normal subjects and lower in patients.

**7.2. Results**

220 Seminars in Dysphagia

IMC (kg/m2

Leslie et al. [49] suggested that the apnea time significantly increases with volume in normal elderly subjects. In contrast, Esteves and colleagues [24] found no increase in apnea time and swallowing with volume in normal young subjects. In the results described in Figure 7, the increase in volume did not result in increased swallowing apnea time in elderly individuals. Note that, in the volume of 5 ml, individuals of the control group had significantly longer apnea times than that observed in the swallowing of saliva, 10 and 20 mL of water (p<0.02). This result may be related to the relatively small number of individuals analysed.

In contrast with that observed in normal volunteers, the presence of COPD resulted in increased apnea time with the bolus volume (Figure 7). We can also observe that patients with COPD had apnea times significantly higher during conditions of higher volume (10 mL and 20 mL). These findings disagree with those described in the study by Gross [38], which observed no difference in apnea time between the COPD and control group. These authors note, however, that in the swallows of COPD patients in which apnea occurred in inspiration time, the apnea interval was longer. Physiologically, the presence of longer periods of apnea in COPD could indicate a compensatory mechanism for airway protection against aspiration of food residuals.

The control group presented an increased number of swallows in the standard-expiration apnea-expiration (EE) pattern in all studied volumes (Figure 8). This is in close agreement with previous studies [9, 20, 22, 50]. This finding supports the theory that swallowing during the expiratory phase represents less risk of aspiration and therefore may be considered a protective mechanism of the airways. Swallowing during the inspiratory phase may facilitate the entry of food and saliva into the airways during and after swallowing [22]. Other patterns were also observed in this group. In order of increasing frequency: inspiration-apnea-expiration (IE), expiration-apnea-inspiration (EI), and inspiration-apnea-inspiration (II). This result is consis‐ tent with that reported by Martin-Harris [22]. The pattern II presented the smallest frequency in all volumes, which agrees with previous results [9, 20, 22].

COPD patients more frequently showed the EE and EI patterns (Figure 8). Similar findings were reported in the study conducted by Cjevic [2]. The pattern II occurred less frequently compared with other patterns. Comparing the swallowing of COPD patients with control subjects, it can be observed that the pattern EI (Figure 8C) occurs more frequently in COPD patients compared to control subjects. This phenomenon was observed in all studied volumes. Considering the pattern II (Figure 8D), we observe that this also occurs more frequently in COPD, particularly in exams using 20 mL. In agreement with the present work, the study by Gross [38] describes that patients with COPD had pre and post inspiration swallowing apnea more often than the control subjects. These results are consistent with the observation that the inspiration after swallowing facilitates aspiration of food and saliva.
