Carbon dioxide retention MCQ | PGI MCQs for MD MS Preparations

Carbon dioxide retention is seen in the following condition 

A. Carbon monoxide poisoning 
B. Lung failure 
C. Drowning 
D. Ventilatory failure 
E. Highaltitude

Ans. B. Lung failure; (C) Drowning; (D) Ventilatory failure:

• Retention of CO2 in the body (hypercapnia) caused by hypoventilation or circulatory deficiency. 

• In Lung failure due to parenchymal causes (e.g. Fibrosis, poor diffusion through the pulmonary membrane or through the tissues); serious hypercapnia usually doesn’t occur because CO2 diffuses 20 times as rapidly as 0₂. If hypercapnia begins to occur, this stimulates pulmonary ventilation which corrects the hypercapnia. 

• Hypercarbia associated with apnea or hypoventilation is less often documented than hypoxia in drowning. 

• In CO-poisoning, there is variable PCO2 

• Hypercapnia is not concomitant when too little 02 in the air, too little Hb, or poisoning of oxidative enzymes 

• In high altitude due to hypoxic stimulation —hyperventilation occurs resulting in fall of PaCO2