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Effect of maturation on infant diaphragmatic function assessed using a non-volitional test

Presented at the Neonatal Society 2001 Summer Meeting (programme).

Rafferty GF, Greenough A, Dimitriou G, Moxham J*

Departments of Child Health and *Respiratory Medicine, Guy's, King's & St Thomas' School of Medicine, King's College Hospital, London, UK

Background: Infant maturation appears to affect diaphragm function, but those data were derived using an effort dependent test which may have biased the results.

Objective: To determine the effect of maturation on diaphragmatic function using a non-volitional test.

Patients: 35 infants (17 born preterm) with a median gestational age of 37 (range 25-42) weeks. At the time of study, their median postconceptional age (PCA) was 39 (range 32-44) weeks, 13 were studied at a PCA of less than 37 weeks. At the time of measurement none had respiratory problems or were hyperinflated (lung volume range 23 to 35 ml/kg).

Methods: Diaphragmatic function was assessed by measuring the transdiaphragmatic pressure (Pdi) generated by magnetic stimulation of the phrenic nerves. Balloon catheters were positioned in the lower third of the oesophagus and stomach. Oesophageal (Poes) and gastric (Pgas) pressure changes were measured using differential pressure transducers. The pressure signals were amplified and displayed in real time on a computer running Labview software and Pdi derived by online subtraction of Poes from Pgas.

Results: The preterm compared to the term infants had significantly lower median right (4.0, range 2.5-6.8 cmH2O versus 4.8, range 2.8-7.2 cmH2O) and median left (3.6, range 2.6-4.8 cmH2O versus 4.3, range 2.7-6.8 cmH2O) transdiaphragmatic pressures (p<0.05). Left and right Pdi correlated significantly with gestational age (r=0.4, p<0.05 and r=0.41, p<0.05 respectively) and PCA (r=0.37, p<0.05 and r=0.55, p<0.01 respectively).

Conclusion: The degree of maturation at birth and the postconceptional age at measurement affects infant diaphragmatic function.

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