Table 1

Changes to the respiratory muscle load-capacity-drive relationship in each condition during sleep, leading to alveolar hypoventilation

	Load	Capacity	Drive
COPD	Dynamic hyperinflation Bronchoconstriction	Loss of intercostal muscle activity during sleep	Reduced drive during sleep does not compensate for increased load/decreased capacity
Obesity	Smaller lung volumes Airway narrowing Dynamic hyperinflation Airway inflammation Small airway tidal closure	Adipose tissue impairing chest expansion Reduced diaphragm neuromuscular coupling	Reduced drive during sleep does not compensate for increased load/decreased capacity
Slowly-progressive neuromuscular disease	Fibrosis of rib cage/spinal deformities Reduce nasopharyngeal dilator muscle function	Respiratory muscle weakness	Reduced drive during sleep does not compensate for increased load/decreased capacity Disruption along the neural pathways
Motor neuron disease	Reduced nasopharyngeal dilator muscle function Increased secretions	Respiratory muscle weakness Phrenic nerve-induced diaphragm paralysis/paresis	Reduced drive during sleep does not compensate for increased load/decreased capacity Disruption along the neural pathways