Grunting was investigated in 22 infants with hyaline membrane disease. It was demonstrated to be a modified Valsalva maneuver, as during expiration intrapleural pressure was increased by closure of the glottis and contraction of the abdominal muscles. Grunting could be prevented if the trachea was intubated; but, during this period the arterial oxygen tension fell. After detubation grunting recommenced and arterial oxygen tension rose to previous levels. Therefore, grunting appears to be a protective form of breathing, aimed at raising the PaO2. This is probably achieved by improvement of alveolar ventilation, but the exact mechanism is not known.
- Received April 10, 1967.
- Accepted October 2, 1967.
- Copyright © 1968 by the American Academy of Pediatrics