Respiratory dysfunction can occur at one or more of the following levels: central neurons including the upper motor neuron, brainstem regions of respiratory control. lower motor neurons, peripheral motor nerves, the neuromuscular junction and the respiratory muscles. Any acute or chronic lesion or condition that affects regions of respiratory control can affect the respiratory system by altering breathing pattern and respiratory drive, leading to central breathing irregularities. Dysfunction of lower motor neurons, the peripheral motor nerves, the neuromuscular junction and the muscle typically results in an impairment of the lower motor neurons, the peripheral motor nerves, the neuromuscular junction or the muscle typically results in an impairment of the respiratory pump which commonly leads to chronic hypercapnia, also called respiratory failure type 2. Moreover, weakness of bulbar muscles can cause an airway obstruction resulting in apneic periods with hypercapnia and hypoxemia. Of note, central and peripheral alterations simultaneously affect ventilation in some disorders, which highlights the need for a specific and sometimes individual diagnostic approach. Considering the impact of respiratory insufficiency on morbidity and mortality, the respiratory function must be assessed and monitored regularly.