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Re: Effect of head up tilting on oxygenation

Dear Editor

We read with interest the paper by Dimitriou et al.,[1] in which it was confirmed again that head up tilting to 45 degrees results in better oxygenation in stable preterm neonates. However compared to our study,[2] in which the same effect was observed, there is a (probably) significant difference. Their infants were studied in the horizontal prone, in the horizontal supine and in the 45 degree head up tilt supine position whereas in our study all infants were studied in the prone position including the 45 degree head up tilt. We had then hypothesised that the combination of the prone position and the 45 degree head up tilt could facilitate diaphragmatic activity.

I do not think that this hypothesis can be totally dismissed by the results of Dimitriou et al.,[1] as suggested by the authors, since their infants were studied in different positions (i.e. supine in their study and prone in our study)

I should be grateful for the authors' views

H.D. Dellagrammaticas

References

(1) Dimitriou G, Greenough A, Pink L, McGhee A, Hickey A, Rafferty GF. Effect of posture on oxygenation and respiratory muscle activity in convalescent infants. Arch Dis Child Fetal Neonatal Ed 2002;86:F147-50.

(2) Dellagrammaticas HD, Kapetanakis J, Papadimitriou M, Kourakis G. Effect of body tilting on physiological functions in stable very low birthweight neonates. Arch Dis Child 1991;66:429-32.

Send letter to journal:
Re: Re: Effect of head up tilting on oxygenation

Dear Editor

We thank Professor Dellagrammaticas for his comments on our study. [1] Dellagrammaticas et al. [2] hypothesised that the combination of the prone posture and the 45 degree head up tilt position could facilitate diaphragmatic activity. We however, propose that the improvement in oxygenation seen in the head up tilt position1 was more likely to be due to a change in lung volume. In the head up tilt position, the weight of the abdominal contents on the diaphragm is reduced, tending to increase functional residual capacity.[3] In contrast, ultrasonographic examination [4] has demonstrated that the diaphragm was significantly thicker at end expiratory volume in the prone rather than the supine position, which is likely to result in reduced diaphragm strength. Indeed, we demonstrated [1] Pimax (a measure of respiratory muscle strength) was lower in the prone compared to the supine position and the supine posture with 45° head tilt.

Anne Greenough MD FRCP FRCPCH DCH
Academic Head of Paediatrics
Children Nationwide Professor of Neonatology and Clinical Respiratory Physiology

Gabriel Dimitriou MD
Lecturer in Perinatology

References

(1) Dimitriou G, Greenough A, Pink L, McGhee A, Hickey A, Rafferty GF. Effect of posture on oxygenation and respiratory muscle strength in convalescent neonates. Arch Dis Child 2002;86:F147-50.

(2) Dellagrammaticas Hd, Kapetankis J, Papadimitriou M, Kourakis G. Effect of body tilting on physiological functions in stable very low birth weight neonates. Arch Dis Child 1991;66: 429-32.

(3) Thoresen M, Cowan F, Whitelaw. Effect of tilting on oxygenation in newborn infants. Arch Dis Child 1988;63: 315-7.

(4) Rehan VK, Nakashima JM, Gutman A, Rubin LP, McCool FD. Effects of supine and prone position on diaphragmatic thickness in healthy term infants. Arch Dis Child 2000;83:234-8.

Send letter to journal:
Re: Neonatal Position and Oxygenation

Dear Editor

We read with interest the postural benefits on oxygenation by G Dimitrioui et al.[1] The study has addressed to the issues which in past, were less investigated. However, the study could have been more complete had it looked into the factors which affect the functioning of diaphragm. Besides the relevant data like weight, age, and the infants who were on full enteral feeds with no respiratory problems, there was no mention of other factors which affect the functioning of diaphragm. Many variables like administration of Xanthenes and B2 blockers, diaphragmatic surgery, phrenic nerve injury, peritonitis, pleuritis ,dyselectrolaemia, acidosis & hypercapnia etc, will affect the optimal functioning of diaphragm.[2] The type, frequency & fortification of feeds could have also affected the gastric emptying and thus affect the ventilation perfusion.[3] The effect of various degrees of shoulder elevation like 30°, 45°, 60° in prone, supine & lateral positions on oxygenation is also known.[4] Therefore, for more effective conclusion on position vis a vis oxygenation, it would be more meaningful to get information generated on the above variables and to analyse results with variable specific stratification.

We in our still unpublished similar study by Gupta G et al, have also looked at effect of posture on oxygenation. Infants were studied in four different positions, supine, prone, right lateral and left lateral. They were kept at various degrees of shoulder inclination of 0°, 30° and 45°. The parameters studied were oxygenation (SPO₂) heart rate, by Novametrix pulse-oximeter and respiratory rate. The recordings were taken at just before feed, 5, 15, 30 and 60 minutes after feed. In our study, we found that SPO₂ was maximum at 45° inclination both in prone as well as right lateral position .

We, therefore, solicit author’s comments for more effective answer to such an important research question.

References

(1) Dimitriou G, Greenough A, Pink L, McGhee A, Hickey A, and Rafferty GF. Effect of posture on oxygenation and respiratory muscle strength in convalescent infants. Arch Dis Child Fetal Neonatal Ed 2002; 86: F86 –F150

(2) Martina JM, Fanaroff AA, Martin RJ. Respiratory disorders in preterm and term infants. In Neonatal–Perinatal Medicine, 7th Edition. Fanaroff AA, Martin RJ, (Eds). St Louis: Mosby. 2002:1042

(3) Yu VYH . Effect of body position on gastric emptying in the neonate. Arch Dis Child 19 75; 50:500 – 4.

(4) Dellagrammaticas HD, Kapetanakis J, Papadimitriou M, et al. Effect of body tilting on physiological functions in stable very low birthweight neonates. Arch Dis Child 1991;66:429–32

Send letter to journal:
Re: Re: Neonatal position and oxygenation

Dear Editor

We thank Professor Gupta for his comments. We agree that many factors affect diaphragmatic function; thus had emphasized this in our discussion and that the infants had acted as their own controls. Unfortunately, Professor Gupta does not provide sufficient detail of his data to allowing meaningful speculation regarding the mechanisms of any changes seen, we look forward to hearing more.

Anne Greenough MD FRCP FRCPCH DCH
Academic Head of Paediatrics
Children Nationwide Professor of Neonatology and Clinical Respiratory Physiology

Gabriel Dimitrioub MD
Clinical Lecturer in Perinatology