Vital Capacity

Also written as VC.

Tidal volume rises about 40% and minute ventilation about 40%; residual volume falls; vital capacity and FEV1 are unchanged.

What our notes say

Tidal volume rises about 40% and minute ventilation about 40%; residual volume falls; vital capacity and FEV1 are unchanged. (Physiological changes in pregnancy)
Progressive reduction in carbon monoxide diffusing capacity, vital capacity and total lung capacity, with normal residual volume.\nCompliance is decreased and lung recoil pressure increased (8.OCCUPATIONAL AND ENVIRONMENTAL LUNG DISEASES MBCHB 2019-2-1)
Respiratory assessment (vital capacity, chest expansion): Reduced vital capacity in GBS — Diaphragmatic and intercostal weakness from motor fiber involvement. (Peripheral neuropathy and Guillain-Barre syndrome)
Airway, breathing, circulation – watch for respiratory muscle weakness; if vital capacity < 20 mL/kg or rapid shallow breathing, prepare for non‑invasive ventilation or intubation. (Peripheral neuropathy and Guillain-Barre syndrome)
Respiratory assessment – reduced vital capacity, shallow breathing; indicates diaphragmatic involvement. (Myasthenia gravis)
| Pulmonary function tests (spirometry) | Baseline respiratory reserve, risk of crisis | Reduced forced vital capacity (< 1 L) or maximal inspiratory pressure signals need for close monitoring. | (Myasthenia gravis)