TABLE 2

Main findings of major studies we considered about the effects of dopaminergic drugs on respiratory parameters and respiratory dysfunctions

First author [ref] (year)Number of patientsClinical scoreDisease durationPharmacological washoutStudy designMain results
Herer [11] (2001)21H&Y 2.6 (mean)0.25–11 years12 hPD patients versus control group. Basal spirometry (pharmacological washout) then spirometry after 45–60 min of levodopa administration (1–2.6 mg·kg−1) versus placeboImprovement of obstructive parameters and/or of saw-tooth spirometry pattern after levodopa
De Pandis [12] (2002)12H&Y 4.08 (mean)8–25 years12 hPD patients with fluctuating symptoms; spirometry in on state versus off stateRestrictive pattern in severe PD, with worsening in the off state
Weiner [13] (2002)20H&Y 2–3, UPDRS III 41.4 (mean in off)Not availableNot reportedSpirometry in on versus off state compared to healthy controlsMild restrictive pattern not influenced by levodopa; decreased respiratory muscle strength and endurance in off state, with a nonsignificant trend to increase after levodopa. POD attenuated after dopaminergic medications
Sathyaprabha [14] (2005)35H&Y 1–21–5 years12 hPD patients versus control group. Spirometry in off state versus on statePredominantly restrictive pattern ameliorating with levodopa (on condition)
Lim [64] (2008)10H&Y 2.4 (mean)8.5 years (mean)12 hPD patients, spirometry in on condition versus off conditionImprovement of restrictive parameters in on condition, even if small
Pal [25] (2007)53H&Y 2.4 (mean)3.1 years (mean)12 h for levodopa, 18 h for dopamine agonistsPD patients versus controls; spirometry in off condition after washout versus on conditionRestrictive disfunction partially reversed by levodopa
Baille [16] (2018)41UPDRS III 19 (mean)0.20–3.6 years12 hSpirometry at the time of recruitment and then two after 2 years of follow-up (both on pharmacological washout)Inspiratory muscle weakness at time of recruitment, without worsening after 2 years. Motor outcome not different among PD patients with inspiratory muscle weakness compared to patients without

PD: Parkinson's disease; H&Y: Hoehn & Yahr; UPDRS: Unified Parkinson's Disease Rating Scale; POD: perception of dyspnoea.