Post-polio lung function.

Post-polio patients sometimes complain about the occurrence of breathing difficulties decades after the polio infection. We have examined 40 post-polio patients who have had respiratory or non-respiratory poliomyelitis for at least 30 years in an attempt to elucidate whether hypoventilation is common and to what extent certain symptoms and simple lung function tests are related to hypoventilation or incipient hypoventilation. We measured arterial blood gases, vital capacity (VC), maximal expiratory and inspiratory pressures (MEP, MIP) and CO2 rebreathing response. Symptoms were assessed by a yes/no questionnaire. Six patients required respiratory assistance at the onset of the disease. At present, two require nocturnal assisted ventilation. Two patients showed manifest hypoventilation; one of which required night-time ventilator, whereas the other patient had not required ventilatory assistance even at the onset of the disease. Significant correlation (p less than 0.05) was found between arterial carbon dioxide tension (a-PCO2) and VC, MEP and ventilation increase during CO2 rebreathing. A significantly higher a-PCO2 was found among those who required respiratory assistance at the onset of the disease, who admitted headache and who felt the cough ineffective. Low VC and low ventilatory increase during CO2 rebreathing and the presence of headache explained 45% of the variation in a-PCO2 in a multiple regression analysis. We conclude that manifest hypoventilation is rare in this unselected material of post-polio patients and that a vital capacity below 45-50% of predicted normal and the presence of frequent headaches indicate an increased risk to develop hypoventilation.