Table 2.

The relationship between cough sound, flow and oesophageal pressure

Sound parameter	Sound analysis time window
	P1	P1–3	P0.5
(a) Flow
PW	0.88 (0.78 to 0.93)	0.82 (0.60 to 0.90)	0.88 (0.79 to 0.92)
Ep	0.87 (0.78 to 0.92)	0.81 (0.56 to 0.90)	0.87 (0.79 to 0.91)
RT	0.31 (0.02 to 0.48)	0.01 (−0.18 to 0.3)	0.23 (−0.05 to 0.42)
D	0.29 (−0.11 to 0.59)	0.60 (0.23 to 0.82)	N/A
Fp	0.11 (−0.25 to 0.34)	0.35 (0.07 to 0.53)	0.17 (−0.06 to 0.45)
BW	−0.24 (−0.53 to 0.11)	0.05 (−0.16 to 0.35)	−0.10 (−0.35 to 0.19)
Fc	0.49 (0.25 to 0.71)	0.63 (0.26 to 0.79)	0.48 (0.19 to 0.78)
(b) Oesophageal pressure
PW	0.89 (0.84 to 0.95)	0.85 (0.65 to 0.91)	0.89 (0.81 to 0.94)
Ep	0.89 (0.82 to 0.95)	0.85 (0.58 to 0.93)	0.89 (0.82 to 0.94)
RT	0.35 (−0.04 to 0.45)	0.05 (−0.33 to 0.53)	0.23 (−0.13 to 0.5)
D	0.23 (−0.11 to 0.54)	0.70 (0.47 to 0.84)	N/A
Fp	0.06 (−0.30 to 0.41)	0.36 (0.12 to 0.60)	0.26 (−0.11 to 0.46)
BW	−0.40 (−0.58 to 0.10)	0.06 (−0.13 to 0.39)	−0.15 (−0.43 to 0.24)
Fc	0.53 (0.22 to 0.76)	0.68 (0.48 to 0.82)	0.53 (0.25 to 0.80)

Data presented as median (IQR) within-subject Spearman’s correlation coefficients for patients with chronic cough and healthy controls combined. The correlations were similar when patients and controls were analysed separately (see online supplementary tables 1–4). Sound was recorded with free-field microphone, with PW, power; Ep, peak energy; RT, rise time; D, duration; Fp, peak frequency; BW, bandwidth; Fc, centroid frequency.