Name the chronic respiratory disorder caused mainly by cigarette smoking in which alveolar walls are damaged.

'Asthma' is caused by

$A$: Emphysema is a chronic obstructive pulmonary disease,causing irreversible distension and loss of elasticity of the alveoli.
$R$: Emphysema is preventable if chronic exposure to smoke (cigarette and others) and pollutants is avoided.

Asthma is a respiratory disease caused by

If the level of carboxyhaemoglobin in blood reaches up to......,the functioning of the central nervous system is severely affected,which results in death.

Decompression sickness is: