Quantifiable features of a tidal breathing phenotype in dogs with severe bronchomalacia diagnosed by bronchoscopy

Figures & data

Figure 1. The definitive diagnosis of canine bronchomalacia was made by bronchoscopy in this study. (A) Bronchoscopic view showing severe collapse of the left and right principal bronchus (LPB and RPB). (B) Bronchoscopic image at the same level of the carina from a dog without bronchomalacia. (C, D) Bronchoscopic images demonstrating the dynamic collapse of the lobar bronchus of the accessory lobe (RB3) and the right caudal lobe (RB4) in a dog with severe bronchomalacia.

Table 1. The overall severity of bronchomalacia was based on the degree of collapse and the total number of airways affected.

Grade of severity	Degree of collapse	Total number of airways with collapse ≥ 50%
Mild	Affected airways between 25 to 50% or up to 50% collapse	≤ 2 of eight sites affected
Moderate	The overall degree of collapse between mild and severe grade	The number of airways affected between mild and severe grade
Severe	≥ 3 bronchi reach 51–75% collapse OR At least 1 bronchus >75% collapse	≥ 3 of eight sites plus segmental bronchi

Notes: Total possible airways affected included eight sites: LPB, RPB, LB1, LB2, RB1, RB2, RB3, RB4. When segmental bronchi were affected, this was considered as a ninth site and the required criterion for the highest severity.

Abbreviations: LPB: the left principal bronchus; RPB: the right principal bronchus; LB1: lobar bronchus of left cranial lobe; LB2: lobar bronchus of left caudal lobe; RB1: lobar bronchus of right cranial lobe; RB2: lobar bronchus of right middle lobe; RB3: lobar bronchus of accessory lobe; RB4: lobar bronchus of right caudal lobe.

Figure 2. Diagram of the set-up used to measure tidal breathing signals in dogs.

Table 2. Basic ventilatory parameters (median with range) in dogs with bronchomalacia and control dogs.

Ventilatory parameters	Bronchomalacia (n = 14)	Control (n = 14)	p
RR (cycles/min)	21 (16–42)	26 (17–59)	.19
TV/BW (mL/kg)	9.8 (3.5–20.9)	13.0 (5.4–27.3)	.11
MV/BW (mL/kg)	218 (59–490)	338 (171–879)	.039*
Ti (second)	0.93 (0.62–1.4)	0.98 (0.43–1.56)	.98
Te (second)	1.65 (0.88–2.38)	1.25 (0.58–2.0)	.13
Te/Ti (ratio)	1.55 (1.13–2.76)	1.35 (1.11–1.81)	.011*
PIF/BW (mL/s/kg)	16.5 (3.2–32.2)	15.9 (10.2–54.3)	.48
PEF/BW (mL/s/kg)	28.6 (7.6–43.5)	14.6 (8.7–41.7)	.09

Note: Significant differences (p < .05) are denoted with boldface.

Abbreviations: RR: respiratory rate; TV/BW: tidal volume per kg body weight; MV/BW: minute volume per kg BW; Ti and Te: inspiratory and expiratory time; PIF/BW and PEF/BW: peak inspiratory and expiratory flow per kg BW.

Table 3. Spirometric parameters from flow-volume (F-V) loop, flow-time (F-t) plot, and volume-time (V-t) plot (median with range) in dogs with bronchomalacia and control dogs.

F-V, F-t, and V-t parameters	Bronchomalacia (n = 14)	Control (n = 14)	p
PEF/EF50	1.19 (1.00–1.59)	1.21 (1.06–1.48)	.38
PEF/EF25	1.71 (1.07–3.96)	1.39 (1.19–2.13)	.23
PEF/PIF	1.66 (1.04–2.39)	0.78 (0.59–1.15)	<.001*
EF50/IF50	1.75 (0.96–2.47)	0.81 (0.54–1.20)	<.001*
ExpLF/Te	0.76 (0.57–0.93)	0.05 (0.02–0.14)	<.001*
Vt-AUCexp (%)	19.3 (10.7–31.0)	44.4 (33.9–48.9)	<.001*

Note: Significant differences (p < .05) are denoted with boldface.

Abbreviations: PIF and PEF: peak inspiratory and expiratory flow; EF50 and IF50: expiratory or inspiratory flow at end TV plus 50% TV; EF25: expiratory flow at end TV plus 25% TV; ExpLF/Te: the ratio of the expiratory low-flow phase to the entire expiratory period; Vt-AUCexp: the proportion of area under expiratory curve on V-t plot.

Figure 3. A flow-time (F-t) plot from a dog with severe bronchomalacia, showing a significantly prolonged low-flow expiratory phase. A F-t plot from a control dog was shown on the upper left Corner.

Figure 4. The volume-time (V-t) plots from a dog with severe bronchomalacia (left) and a control dog (right). an exponential shape of the expiratory curve was noted in dogs severe bronchomalacia, resulting in a low proportion of area under expiratory curve on V-t plot (Vt-AUCexp).