To determine whether a statistically significant relationship exists between Forced Vital Capacity (FVC) and Maximum Phonation Time (MPT) in individuals with Motor Neuron Disease (MND), and to evaluate the potential of MPT as a surrogate marker for respiratory function.

A retrospective chart review was conducted on 56 patients with MND over a 36-month period, encompassing 230 clinical visits. Data collected included FVC, MPT, Peak Cough Flow (PCF), ALS Functional Rating Scale–Revised (ALS-FRS-R), and demographic variables (sex, race, time since diagnosis, and MND subtype). Correlational analyses were performed to assess relationships among variables.

Moderate to strong correlations were observed:

• FVC and ALS-FRS-R: r = 0.71
• PCF and FVC: r = 0.78
• PCF and ALS-FRS-R: r = 0.60
• MPT and ALS-FRS-R: r = 0.51
• FVC and MPT: r = 0.46 

MPT demonstrated a moderate correlation with FVC, supporting its potential utility as a surrogate respiratory measure in MND populations. These findings are particularly relevant for telehealth and settings where spirometry is not feasible, offering clinicians an accessible tool for monitoring respiratory function and guiding care decisions.