Volume 86 Number 3
Ellis FA: Keratosis foUicularis is not primarily a follicular disease, Arch Dermat Syph 50:27, 1944. 10. Graham JH, Johnson WC, and Helwig EB: Dermal pathology, New York, 1972, Harper & Row, Publishers, p 120.
Letters to the Editor
9.
4.
5.
More on the "oligohydraminios syndrome"
6.
79 8.
70 the Editor: 1 wish to reinforce the arguments of Thomas and Smith j by referring to material published elsewherefi 3 Two additional experiments of nature strengthen the case in favor of the concept of the "oligohydramnios tetrad": (1) Urethral obstructions in the fetus are associated with the extrarenal manifestations of Potter's syndrome, but only when the obstruction is total 4 and when there is no bypass such as a patent urachus. 5 (2) Bilateral infantile polycystic kidneys are usually associated with fetal anuria, the "oligohydramnios tetrad," and early death from respiratory insufficiency. Occasional infants survive for a few postnatal months to die of renal failure6; in such cases limited renal function is present postnatally and presumably prenatally and the "oligohydramnios tetra&' is absent 9 Both early (respiratory) and late (renal) deaths may occur in subjects of the same kindred. 3 The extreme rarity of the extrarenal manifestations of Potter's syndrome in the absence of renal nonfunction in Dr. Potter's experience 7 is no doubt due to the policy of terminating pregnancies complicated by premature rupture of the membranes. In my own experience of about 25,000 live births, nine pregnancies with chronic amniotic leakage of more than 3 weeks' duration resulted in the delivery of a live-born child9 Three infants had the "oligohydramnios tetrad" and died within hours of birth of respiratory failure which did not respond to resuscitation. Finally I wish to draw attention to the publication of Blanc and associates 8 in which the concept of the pathogenic role of oligohydramnios was presented. Max Perlman Neonatal Unit o.f the Department of Pediatrics Hadassah University Hospital Kiryat Hadassah Jerusalem, Israel
REFERENCES 1. Thomas IT, and Smith DW: Oligohydramnios, cause of the non-renal features of Potter's syndrome, including 9 pulmonary hypoplasia, J PEDIATR84:81 l, 1974. 2. Perlman M, Levin M, and Ben-Aderet N: Renal malformations, oligohydramnios and pulmonary hypoplasia, Proc. Fifth Isr~teli Congress Obstet Gynecol p 30, 1972 (abst.). 3. Perlman M, and Levin M: Fetal pulmonary hypoplasia, anuria and olig0hydramnios: Clinico-pathological obser-
481
vatiOns and review of the literature, A m J Obstet Gynecol 118:1119, 1974. Potter EL: Pathology of the fetus and infant, ed. 2, Chicago, 1961, Year Book Medical Publishers Inc., pp 301-302. May F: Ein fall yon kongenitalem verchluss der urethra membranacea, Z Urol 42:245, 1949. Lundin PM, and Olow I: Polycystic kidneys in newborns, infants and children. A clinical and pathological study, Acta Paediatr 50:185, 1961. P o t t e r EL: O l i g o h y d r a m n i o s : F u r t h e r c o m m e n t , J PEDIATR84:931, 1974. Blanc WA, Apperson JW, and McNally J: Pathology of the newborn and of the placenta in oligohydramnios, Bull. Sloane Hosp Women 8:51, 1962.
Significance of the paired and unpaired t test in evaluating CPAP To the Editor: In reporting their experience with continuous positive airway pressure (CPAP) delivered by face-mask, Ackerman and associates 1 conclude that the 7 m m Hg increase in Paco2 with the application of CPAP was not significant. Although it is not specified, I surmise that an unpaired t test was used to determine significance. The appropriate calculation is a paired t test, which yields a t value of 2.52 and a p ( 0.05. This result closely parallels our own experience with CPAP by face-mask. David A. Belenky, M.D. Senior Fellow Division of Neonatal Biology University of Washington School of Medicine Seattle, Wash. 98195
REFERENCE 1. Ackerman BD, Stein MP, Sommer JS, and Schumacher M: Continuous positive airway pressure applied by means of a tight-fitting face-mask, J PEDIATR 85:408, 1974.
Reply To the Editor: Dr. Belenky is correct that the data in question could appropriately by analyzed by the paired t test, and that, so analyzed, the data suggest a significant elevation of the Paco 2. The effect of continuous positive airway pressure (CPAP) on the Paco 2 is an inconsistent one. Gregory and associates 1 reported a decrease in tidal volume and minute volume, even though alveolar ventilation did not change significantly. Their data on dynamic compliance, showing no significant change, together with the data showing improved oxygenation without change in alveolar ventilation, suggested that CPAP resulted in
Ellis FA: Keratosis foUicularis is not primarily a follicular disease, Arch Dermat Syph 50:27, 1944. 10. Graham JH, Johnson WC, and Helwig EB: Dermal pathology, New York, 1972, Harper & Row, Publishers, p 120.
Letters to the Editor
9.
4.
5.
More on the "oligohydraminios syndrome"
6.
79 8.
70 the Editor: 1 wish to reinforce the arguments of Thomas and Smith j by referring to material published elsewherefi 3 Two additional experiments of nature strengthen the case in favor of the concept of the "oligohydramnios tetrad": (1) Urethral obstructions in the fetus are associated with the extrarenal manifestations of Potter's syndrome, but only when the obstruction is total 4 and when there is no bypass such as a patent urachus. 5 (2) Bilateral infantile polycystic kidneys are usually associated with fetal anuria, the "oligohydramnios tetrad," and early death from respiratory insufficiency. Occasional infants survive for a few postnatal months to die of renal failure6; in such cases limited renal function is present postnatally and presumably prenatally and the "oligohydramnios tetra&' is absent 9 Both early (respiratory) and late (renal) deaths may occur in subjects of the same kindred. 3 The extreme rarity of the extrarenal manifestations of Potter's syndrome in the absence of renal nonfunction in Dr. Potter's experience 7 is no doubt due to the policy of terminating pregnancies complicated by premature rupture of the membranes. In my own experience of about 25,000 live births, nine pregnancies with chronic amniotic leakage of more than 3 weeks' duration resulted in the delivery of a live-born child9 Three infants had the "oligohydramnios tetrad" and died within hours of birth of respiratory failure which did not respond to resuscitation. Finally I wish to draw attention to the publication of Blanc and associates 8 in which the concept of the pathogenic role of oligohydramnios was presented. Max Perlman Neonatal Unit o.f the Department of Pediatrics Hadassah University Hospital Kiryat Hadassah Jerusalem, Israel
REFERENCES 1. Thomas IT, and Smith DW: Oligohydramnios, cause of the non-renal features of Potter's syndrome, including 9 pulmonary hypoplasia, J PEDIATR84:81 l, 1974. 2. Perlman M, Levin M, and Ben-Aderet N: Renal malformations, oligohydramnios and pulmonary hypoplasia, Proc. Fifth Isr~teli Congress Obstet Gynecol p 30, 1972 (abst.). 3. Perlman M, and Levin M: Fetal pulmonary hypoplasia, anuria and olig0hydramnios: Clinico-pathological obser-
481
vatiOns and review of the literature, A m J Obstet Gynecol 118:1119, 1974. Potter EL: Pathology of the fetus and infant, ed. 2, Chicago, 1961, Year Book Medical Publishers Inc., pp 301-302. May F: Ein fall yon kongenitalem verchluss der urethra membranacea, Z Urol 42:245, 1949. Lundin PM, and Olow I: Polycystic kidneys in newborns, infants and children. A clinical and pathological study, Acta Paediatr 50:185, 1961. P o t t e r EL: O l i g o h y d r a m n i o s : F u r t h e r c o m m e n t , J PEDIATR84:931, 1974. Blanc WA, Apperson JW, and McNally J: Pathology of the newborn and of the placenta in oligohydramnios, Bull. Sloane Hosp Women 8:51, 1962.
Significance of the paired and unpaired t test in evaluating CPAP To the Editor: In reporting their experience with continuous positive airway pressure (CPAP) delivered by face-mask, Ackerman and associates 1 conclude that the 7 m m Hg increase in Paco2 with the application of CPAP was not significant. Although it is not specified, I surmise that an unpaired t test was used to determine significance. The appropriate calculation is a paired t test, which yields a t value of 2.52 and a p ( 0.05. This result closely parallels our own experience with CPAP by face-mask. David A. Belenky, M.D. Senior Fellow Division of Neonatal Biology University of Washington School of Medicine Seattle, Wash. 98195
REFERENCE 1. Ackerman BD, Stein MP, Sommer JS, and Schumacher M: Continuous positive airway pressure applied by means of a tight-fitting face-mask, J PEDIATR 85:408, 1974.
Reply To the Editor: Dr. Belenky is correct that the data in question could appropriately by analyzed by the paired t test, and that, so analyzed, the data suggest a significant elevation of the Paco 2. The effect of continuous positive airway pressure (CPAP) on the Paco 2 is an inconsistent one. Gregory and associates 1 reported a decrease in tidal volume and minute volume, even though alveolar ventilation did not change significantly. Their data on dynamic compliance, showing no significant change, together with the data showing improved oxygenation without change in alveolar ventilation, suggested that CPAP resulted in
