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 patients | Clinical score | Disease duration | Pharmacological washout | Study design | Main results |
| Herer [11] (2001) | 21 | H&Y 2.6 (mean) | 0.25–11 years | 12 h | PD patients versus control group. Basal spirometry (pharmacological washout) then spirometry after 45–60 min of levodopa administration (1–2.6 mg·kg−1) versus placebo | Improvement of obstructive parameters and/or of saw-tooth spirometry pattern after levodopa |
| De Pandis [12] (2002) | 12 | H&Y 4.08 (mean) | 8–25 years | 12 h | PD patients with fluctuating symptoms; spirometry in on state versus off state | Restrictive pattern in severe PD, with worsening in the off state |
| Weiner [13] (2002) | 20 | H&Y 2–3, UPDRS III 41.4 (mean in off) | Not available | Not reported | Spirometry in on versus off state compared to healthy controls | Mild 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) | 35 | H&Y 1–2 | 1–5 years | 12 h | PD patients versus control group. Spirometry in off state versus on state | Predominantly restrictive pattern ameliorating with levodopa (on condition) |
| Lim [64] (2008) | 10 | H&Y 2.4 (mean) | 8.5 years (mean) | 12 h | PD patients, spirometry in on condition versus off condition | Improvement of restrictive parameters in on condition, even if small |
| Pal [25] (2007) | 53 | H&Y 2.4 (mean) | 3.1 years (mean) | 12 h for levodopa, 18 h for dopamine agonists | PD patients versus controls; spirometry in off condition after washout versus on condition | Restrictive disfunction partially reversed by levodopa |
| Baille [16] (2018) | 41 | UPDRS III 19 (mean) | 0.20–3.6 years | 12 h | Spirometry 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.