Table 1.

Pharmacological studies using different methodologies of inhalation cough challenge with citric acid or tartaric acid* as tussigenic agents.

Author	Delivery system	Output (O) or volume (V)	Inh type	Dose or concentration	Recording method	Normal values	Agent tested	Number tested
Lowry et al. [70, 100]	Neb (U)	1.8 ml min−1 (O)	1 min	0.68% in 0.79% NaCl	1 min	11.4 coughs min−1 [100]	Captopril [70]	21 [100] 16 [70]
Poundsford et al. [47, 63, 101]	Neb	833 ml (V)	5 s	0.5–32% [101] 0.125–2.0 × 10−1 mol l−1 [63]	C-Thresh [63] CI [101]	Total coughs and CI: 11.6 and 5.3 [101]	Salbutamol, ipratropium [101] Opiates [63]	16 [101]
Laude et al. [24]	Neb + d-meter	0.125 ml Inh−1 (O)	S-breath	10–1000.0 mm	10 s	D5 141.3 mm Capsaicin	Citric acid	10
Fujimura et al. [46, 60, 61]	Neb	0.21 ml min−1 (O)	15 s	1.56–800.0 mg ml−1	1 min	Geomean D5 1.03 mg l−1 (F) 2.62 mg l−1 (M) [61] 32.0 mg ml−1 [46, 60]	Mexiletine [60] Procaterol Methacholine [46]	14 [60] 28 [46]
Thompson et al. [30, 31]	Neb + d-meter	0.275 ml Inh−1 (O)	S-breath	500.0 mm	10 s	19.07 coughs (F) 11.97 coughs (M) [30]	Dextromethorphan dextrorphan [31]	160 [30] 19 [31]
Packman et al. [34]	–	–	S-breath	5%	1 min	–	Diphenhydramine	20
Morice et al. [32, 33]	Neb + d-meter	0.125 ml Inh−1 (O)	S-breath	33.0 µmol	1-min	9 coughs (baseline) [32]	Menthol [32] dextromethorphan [33]	20 [32]

Neb = Nebulizer (Jet unless stated otherwise), U = Ultrasonic, d-meter = Breath activated dosimeter, Inh = Inhalation, S-breath = Single breath, MMD = Mass median diameter, MMAD = Mass median aerodynamic diameter, CI = Cough index, i.e. number of coughs divided by the time of coughing, C-Thresh = Cough threshold, i.e. concentration causing one cough, Geomean = Geometric mean, ACEI = Angiotensin converting enzyme inhibitors.