Effects of noninvasive ventilation on the coordination between breathing and swallowing in patients with chronic obstructive pulmonary disease

Figures & data

Table 1 Correlations between breathing-swallowing coordination and patient characteristics

		p-value
		SW-I frequency	SW-E frequency
Age (years)	75.8±6.6	0.236	0.232
BMI (kg/m^2)	21.2±4.3	0.594	0.714
Pulmonary function
VC (L)	2.87±0.77	0.632	0.972
VC (%)	87.1±18.6	0.397	0.724
FEV1 (L)	1.28±0.61	0.692	0.726
FEV1 (%)	45.6±14.8	0.883	0.732
DLCO/VA (%)	53.7±27.5	0.98	0.918
Blood gas
pH	7.44±0.03	0.569	0.718
PaO2 (mmHg)	76.9±11.8	0.735	0.606
PaCO2 (mmHg)	37.8±4.1	0.819	0.523
HCO3^− (mmol/L)	24.8±1.9	0.307	0.312
P/F ratio	3.2±0.85	0.535	0.276
RSST	5.29±2.20	0.241	0.202

Abbreviations: SW-I, inspiration after swallowing, SW-E, expiration after swallowing, BMI, body mass index, VC, vital capacity, FEV₁, forced expiratory volume in 1 s, DLCO/VA (%), percent of diffusing capacity for carbon/alveolar ventilation, PaO₂, arterial oxygen partial pressure, PaCO₂, arterial carbon dioxide partial pressure, P/F ratio, PaO₂/inspired oxygen fractional concentration ratio, RSST, repetitive saliva swallowing test.

Table 2 Distribution of the occurrence of SNIF in the respiratory phase after swallowing

		Respiratory phase after swallowing
		Inspiratory phase	Pause phase	Expiratory phase
SNIF(+)	Frequency	119	23	483
(n=625)	%	56.9	79.3	82.7
	Residual	−7.5	0.4	7
SNIF(-)	Frequency	90	6	101
(n=197)	%	43.1	20.7	17.3
	Residual	7.5	−0.4	−7
Total (n=822)	Frequency	209	29	584

Notes: The “%” is the frequency of swallows at each respiratory phase, and residual values indicate the differences between the number of swallows observed at each respiratory phase and the number expected based on the null hypothesis. Residual >2.58: p-value <0.01, >1.96: p-value <0.05.

Abbreviation: SNIF, the occurrence of swallowing-associated non-inspiratory flow.

Figure 1 The occurrence of the respiratory phase after swallowing under the control, CPAP, and BiPAP conditions. Values are reported as frequencies, percentages, and residuals. The SW-E frequency was markedly increased during CPAP, and the SW-I frequency was lower than under other conditions (p<0.01). The SW-I frequency was higher during the control and BiPAP conditions than under CPAP conditions (p<0.01).Abbreviations: CPAP, continuous positive pressure ventilation; BiPAP, bi-level positive airway pressure ventilation; SW-E, expiration after swallowing; SW-I, inspiration after swallowing.

Figure 2 Representative respiratory flow signals during saliva swallowing under (A) control, (B) CPAP, and (C) BiPAP conditions. Note that inspiration after swallowing under the control condition is a natural inspiration, whereas inspiration after swallowing under the BiPAP condition is triggered by SNIF. Abbreviations: SNIF, the occurrence of swallowing-associated non-inspiratory flow; CPAP, continuous positive pressure ventilation; BiPAP, bi-level positive airway pressure ventilation.

Table 3 Distribution of the occurrence of SNIF in the respiratory pause for swallowing during spontaneous breathing under the control, CPAP, and BiPAP conditions

		Condition
		Control	CPAP	BiPAP
SNIF(+)	Frequency	144	257	224
(n=625)	%	51.4	95.5	82.1
	Residual	−11.9	9.1	2.8
SNIF(-)	Frequency	136	12	49
(n=197)	%	48.6	4.5	17.9
	Residual	11.9	−9.1	−2.8
Pause duration ≤0.8 s	Frequency	79	178	177
(n=434)	%	28.2	66.2	64.8
	Residual	−10.1	5.4	4.9
Pause duration >0.8 s	Frequency	201	91	96
(n=388)	%	71.8	33.8	35.2
	Residual	10.1	−5.4	−4.9
Total (n=822)	Frequency	280	269	273

Notes: Residual >2.58: p-value <0.01, >1.96: p-value <0.05.

Abbreviations: SNIF, the occurrence of swallowing-associated non-inspiratory flow; CPAP, continuous positive pressure ventilation; BiPAP, bi-level positive airway pressure ventilation.

Figure 3 Distribution of the timing of swallowing in the respiratory phase (percentage) under the control, CPAP, and BiPAP conditions. The timing of swallowing in the respiratory phase is divided into three phases: early (<50% of the mean respiratory cycle from the onset of inspiration), intermediate (50–80%), and late (>80%). Values are reported as frequencies, percentages, and residuals. Note that swallowing in the early respiratory phase is decreased and that swallowing in the intermediate phase is increased under the CPAP condition compared to the control condition. Abbreviations: CPAP, continuous positive pressure ventilation; BiPAP, bi-level positive airway pressure ventilation.