It is possible to employ the isolette incubator-respirator for application of a constant negative pressure (CNP) without the modification described by Vidyasagar. The solenoid valve is blocked in "up position" by a simple mechanical procedure which is easily reversible. Tank is employed in "incubator position." The motor driven vacuum is then acting continuously and creates CNP. Several applications of this method envisioned by us have been practiced on 20 infants. 1. It is a useful adjunct at oxygen therapy in hyaline membrane disease (HMD).