Respiratory muscle strength in healthy infants and those with surgically correctable anomalies.

Assessment of respiratory muscle strength provides important diagnostic and prognostic information. Normative data in healthy, term infants is, however, limited. Surgically correctable birth defects, congenital diaphragmatic hernia (CDH) and abdominal wall defects (AWD), commonly have impaired diaphragm function. The study aims were to obtain normative data for respiratory muscle strength in healthy, term born infants at birth and at 6 weeks postnatal age (PNA) and to investigate the influence of growth and maturation on inspiratory muscle strength in CDH/AWD infants. Maximal inspiratory (cPimax) and expiratory (cPemax) pressures during crying were measured at birth in 67 healthy, term born infants (mean (SD) gestational age (GA) 39.4 (1.7) weeks) and reassessed in 27 at 6 weeks PNA. cPimax and functional residual capacity (FRC) (22.3 (4.2) ml/kg) were also measured in 23 infants with AWD/CDH (mean (SD) GA 36.9 (2.1) weeks) and reassessed in 16 at median (range) 6.5 (1.5-15) months PNA. In healthy infants, mean (SD) cPimax was 88.8 (19.33) cmH2 O and cPemax 61.8 (13.5) cmH2 O at birth, increasing significantly at followup to 100.9 (15.2) cmH2 O (P < 0.05) and 82.6 (19.4) cmH2 O (P < 0.001) respectively. Mean (SD) cPimax was significantly lower (47.5 (22.4) cmH2 O, P < 0.0001) in AWD/CDH infants compared to healthy infants at birth but had increased significantly to 88.1 (27.6) cmH2 O (P < 0.0001) at followup which correlated significantly with increases in FRC (r(2) = 0.33, P = 0.0263). Infants with AWD and CDH have significantly reduced inspiratory muscle strength compared to healthy term born infants but strength increases markedly in early life.

Effect of caffeine on respiratory muscle strength and lung function in prematurely born, ventilated infants.

The aims of this study were to determine whether caffeine administration increased respiratory muscle function and if this was associated with lung function improvement in prematurely born infants being weaned from mechanical ventilation. Respiratory muscle function was assessed by measurement of the maximum pressures generated during occlusions at end inspiration (Pemax) and end expiration (Pimax) and lung function by measurement of lung volume (functional residual capacity (FRC)) and respiratory system compliance (CRS) and resistance (RRS) in 18 infants with a median gestational age of 28 (range 24-36) weeks. Measurements were made immediately prior to caffeine administration (baseline) and 6 h later. Six hours after caffeine administration compared to baseline, the median Pemax (p = 0.017), Pimax (p = 0.004), FRC (p < 0.001), CRS (p = 0.002) and RRS (p = 0.004) had significantly improved. Our results suggest that caffeine administration facilitates weaning of prematurely born infants from mechanical ventilation by improving respiratory muscle strength.

Lung gas transfer in children with sickle cell anaemia.

The impact of sickle cell anaemia (SCA) on respiratory function of children must be determined if their management is to be optimised. Pulmonary diffusing capacity (DL(CO)), corrected for haemoglobin (DL(COc)), therefore was assessed in 24 children with SCA and 24 ethnic matched controls, mean age 11 (range 7-16) years. To determine if any differences found correlated with other measures of lung function, spirometry was undertaken and lung volumes assessed. The SCA children compared to the controls had lower weight (p=0.01), body mass index (p=0.002), DL(CO) (p<0.0001), K(CO) (p=0.003), V(CSB) (p=0.01), FEV(1) (p<0.0001) and FVC (p<0.0001), but greater K(COc) (p=0.001). K(COc) results correlated significantly with PEF (r=-0.58, p=0.02), but not TLC(pleth) (p=0.36), FEV(1) (0.39) or FVC (p=0.36). In conclusion, when corrected for haemoglobin levels, the SCA children compared to controls of similar age had elevated gas transfer per unit lung volume results. Our results suggest this abnormality is independent of other lung function abnormalities.

Sleeping position, oxygen saturation and lung volume in convalescent, prematurely born infants.

OBJECTIVE: To determine whether the effects of sleeping position on lung volume and oxygenation are influenced by postmenstrual age (PMA) and oxygen dependency in convalescent prematurely born infants. DESIGN: Prospective study. SETTING: Tertiary neonatal unit. PATIENTS: 41 infants (21 oxygen dependent), median gestational age 28 weeks (range 24-31 weeks) and birth weight 1120 g (range 556-1780 g). INTERVENTION: Infants were studied both supine and prone at two-weekly intervals from 32 weeks' PMA until discharge. Each posture was maintained for 1 h. MAIN OUTCOME MEASURES: Pulse oximeter oxygen saturation (Spo(2)) was monitored continuously, and at the end of each hourly period functional residual capacity (FRC) was measured. RESULTS: Overall, lung volumes were higher in the prone position throughout the study period; there was no significant effect of PMA on lung volumes. Overall, Spo(2) was higher in the prone position (p = 0.02), and the effect was significant in the oxygen-dependent infants (p = 0.03) (mean difference in Spo(2) between prone and supine was 1.02%, 95% CI 0.11% to 1.92%), but not in the non-oxygen-dependent infants. There was no significant influence of PMA on Spo(2). CONCLUSION: In the present study, prone sleeping did not improve oxygenation in prematurely born infants, 32 weeks' PMA or older and with no ongoing respiratory problems. However, the infants were monitored in each position for an hour, thus it is recommended that oxygen saturation should continue to be monitored after 32 weeks' PMA to be certain that longer periods of supine sleeping are not associated with loss of lung volume and hypoxaemia.