Validation of respiratory inductive plethysmography using the Qualitative Diagnostic Calibration method in anaesthetized infants

The aim of this study was to compare tidal volume (VT) derived from the Qualitative Diagnostic Calibration (QDC) method (VT,QDC) with measurements from pneumotachography (VT,PN,T) in anaesthetized infants. Measurements were made during spontaneous (SV) and intermittent positive pressure (IPPV) ventilation, sighs and airway occlusions. The VT,DIF was the difference between VT,QDC and VT,PNT (%VT). The contribution of the ribcage (rc) to VT,QDC (%rc) and the thoracoabdominal phase lag were also derived. Twenty-eight infants, mean (SD) age 14.0 (6.2) months were studied. VT,QDC represented VT,PNT most closely when > or = 20 breaths were analysed. There was close agreement during SV immediately after the calibration period (95% limits of agreement (LA; QDC - PNT) -23, 3.0%). The 95% LA increased to -9.6, 10.2% after 10 min. Accuracy diminished during IPPV (95% LA -38, 31%), and sighs. During airway occlusions, when VT,PNT was zero, the 95% LA were -63, 4.1 mL x kg(-1). Mean phase lag was 36 and 2%, respectively, during SV and IPPV (p<0.05). The %rc appeared to be overestimated, being in excess of 50% in infants under 12 months. The Qualitative Diagnostic Calibration method used to estimate tidal volume in anaesthetized infants was limited by the need to analyse > or = 20 breaths and by a loss of within-subject accuracy if measurement conditions or pattern of breathing changed.     

Tidal volume measurements in newborns using respiratory inductive plethysmography

Respiratory inductive plethysmography (RIP) is a well-accepted noninvasive technology for monitoring breathing patterns in adults. Prior attempts to calibrate this device in babies have been fraught with technical difficulties, thereby limiting applications in this population. Recently, a new method, qualitative diagnostic calibration (QDC), has been shown to provide accurate calibration of tidal volume in adults. The QDC method is based upon principles of the isovolume maneuver and carried out during natural breathing without specialized respiratory maneuvers or postural changes. We calibrated RIP with QDC in the supine posture and compared tidal volume (VT) measured with RIP to VT by a face mask-pneumotachograph (PNT) in 21 healthy full-term newborns in supine and prone postures. Eleven of the babies were calibrated during active sleep and 10 in quiet sleep. The mean VT in the supine and prone postures were 19 and 25 ml, respectively. In the supine and prone postures, weighted mean difference between RIP (VT) and PNT (VT) and 95% confidence intervals were -0.05 ml (-0.27, 0.18) and -0.32 ml (-0.08, 0.55), respectively. There was no difference in the accuracy of RIP relative to PNT calibrated during active sleep when thoracoabdominal incoordination was present or quiet sleep when it was not in either the supine or the prone postures. Therefore, in full-term infants, RIP calibrated with QDC solely in the supine posture provides clinically acceptable measurements of VT in both supine and prone postures.     

High frequency oscillation for preterm infants with severe respiratory failure

High frequency oscillation (HFO) as rescue treatment for preterm infants with severe respiratory failure has been assessed and prognostic factors identified. Thirty six infants with a median gestational age of 27 weeks were studied. Immediately before transfer to HFO, the infants were receiving an inspired oxygen concentration of > or = 85% and/or a mean airway pressure of > or = 12 cm H2O and had a median alveolar-arterial oxygen gradient (A-aDO2) of 73.28 kPa (range 49.34-89.91). Seventeen infants subsequently died. Comparison of those 17 with the remaining 19 infants demonstrated that respiratory distress syndrome and persistent fetal circulation were associated with a significantly better outcome than pulmonary airleak. The A-aDO2 after two and six hours on HFO was significantly higher in those infants who survived compared with those who died. We conclude that a diagnosis of pulmonary airleak and failure to show early improvement in respiratory status indicate a poor prognosis when HFO is used as rescue treatment.     

Impaired respiratory function in infants with anterior abdominal wall defects

Pentobarbital alone, pentobarbital plus 1% lidocaine solution, pentobarbital plus 2% lidocaine solution, and pentobarbital plus 3% lidocaine solution were each used to euthanatize 6 dogs. For each dog, time between the beginning of injection of the euthanasia solution and each of the following events was recorded: collapse, onset of apnea, flat-line electrocardiogram, flat-line electroencephalogram, loss of palpable heartbeat, and loss of palpable pulse. Any signs of pain or discomfort were also recorded. There were no significant differences among groups except for time to flat-line electrocardiogram. Dogs euthanatized with pentobarbital alone had significantly longer times than did dogs euthanatized with pentobarbital in combination with any of the lidocaine concentrations. We concluded that pentobarbital in combination with lidocaine was a reasonable alternative to pentobarbital alone when euthanatizing dogs.     

Chest wall mechanics in sustained microgravity

We assessed the effects of sustained weightlessness on chest wall mechanics in five astronauts who were studied before, during, and after the 10-day Spacelab D-2 mission (n = 3) and the 180-day Euromir-95 mission (n = 2). We measured flow and pressure at the mouth and rib cage and abdominal volumes during resting breathing and during a relaxation maneuver from midinspiratory capacity to functional residual capacity. Microgravity produced marked and consistent changes (Delta) in the contribution of the abdomen to tidal volume [DeltaVab/(DeltaVab + DeltaVrc), where Vab is abdominal volume and Vrc is rib cage volume], which increased from 30.7 +/- 3. 5 (SE)% at 1 G head-to-foot acceleration to 58.3 +/- 5.7% at 0 G head-to-foot acceleration (P < 0.005). Values of DeltaVab/(DeltaVab + DeltaVrc) did not change significantly during the 180 days of the Euromir mission, but in the two subjects DeltaVab/(DeltaVab + DeltaVrc) was greater on postflight day 1 than on subsequent postflight days or preflight. In the two subjects who produced satisfactory relaxation maneuvers, the slope of the Konno-Mead plot decreased in microgravity; this decrease was entirely accounted for by an increase in abdominal compliance because rib cage compliance did not change. These alterations are similar to those previously reported during short periods of weightlessness inside aircrafts flying parabolic trajectories. They are also qualitatively similar to those observed on going from upright to supine posture; however, in contrast to microgravity, such postural change reduces rib cage compliance.     

Airway closure during mixed apneas in preterm infants: is respiratory effort necessary?

We report the ability of azithromycin in combination with quinine to eliminate the Babesia infection in a native Taiwanese woman. Failure of elimination of the babesial infection was observed two weeks after treating with standard regimen of oral quinine plus intravenous clindamycin for a 10-day course of therapy. Azithromycin in place of clindamycin was administered for another 10-day course of therapy two months following initial treatment. Clearance of Babesia parasites was observed and verified by hamster inoculation. These results suggest that azithromycin plus quinine should be considered as an alternative therapy for human babesiosis, especially in the failure of treatment with standard regimens.     

Bone mineralization in preterm infants

In preterm neonates a large skeletal mineral deficit builds up between birth and 40 wk postconception. During the phase of catch-up growth between 40 and 60 wk postconception there is a catch-up in peripheral skeletal mineralization, so that by the age of 1 y the skeletal mineral content is similar in preterm and term infants, despite the former being smaller, a finding that has been replicated for lumbar spinal mineralization. Later follow-up studies suggest that this catch-up persists and mineralization remains appropriate for body size. However, given the continuing abnormal growth experience of former preterm individuals, it would still be important to examine their bone mineralization in early adulthood. A number of interventions can improve perinatal bone mineralization, but few studies examine their long-term effectiveness. One such study has suggested that a relatively poor mineral diet in this period is, counterintuitively, associated with a later advantage in skeletal mineralization. If this finding is repeatable, then it could result in a major change in nutrition strategy in the neonatal period.     

Erythropoietin in very preterm infants

Three neonates (a male and two females of gestational ages 27, 27 and 29 weeks with birthweight 985, 660 and 1130 g), born to parents who are Jehovah's Witnesses, were admitted to our neonatal intensive care unit over a 2 month period in 1992. Human recombinant erythropoietin (rHuEpo, 200 u/kg sc. on alternate days for 6-8 weeks) was started early in conjunction with strict control of blood sampling in an attempt to avoid the need for blood transfusion. The lowest haemoglobin recorded was 95 g/L at 35 days of age in the first infant. The amount of blood withdrawn for sampling was 21.4 mL, 20.7 mL and 5.5 mL, respectively. All were discharged near their expected birthdate, never having received a blood transfusion in the Nursery. It is possible to manage sick, very preterm, very low birthweight neonates in a neonatal intensive care setting without the use of blood transfusions by the early use of rHuEpo in conjunction with strict control of blood sampling.     

Antenatal steroids, condition at birth and respiratory morbidity and mortality in very preterm infants

The study purpose was to compare the effect of exercise training on serum lipid and apolipoprotein concentrations and the activities of intravascular enzymes related to lipid transport in previously untrained eumenorrheic, premenopausal (PRM) women (n = 21; mean age, 36 +/- 3 years) and estrogen-free postmenopausal (POM) women (n = 16; mean age, 68 +/- 8 years). Subjects trained at a progressive intensity and duration (50% to 75% maximal O2 consumption [VO2max], 200 to 300 kcal/session) 4 d/wk for 12 weeks. Before and after training, VO2max, body weight, relative body fat, and fasting blood samples were obtained following 2 weeks on a standardized diet designed to maintain body weight and during the early follicular stage for the PRM group. Blood samples were analyzed for serum total cholesterol (TC), triglyceride (TG), high-density lipoprotein cholesterol (HDL-C), the cholesterol content of the HDL3 subfraction, apolipoprotein (apo)A-I and apoB, lipoprotein(a), and the activity of lecithin:cholesterol acyltransferase (LCAT). Total and hepatic triglyceride lipase activity (HTGLA) were determined from plasma samples obtained after heparin administration. The cholesterol content of the low-density lipoprotein (LDL) and HDL2 subfractions and endothelial-bound lipoprotein lipase activity (LPLA) were calculated. A two (group) x two (time) multivariate ANOVA (MANOVA), with repeated measures for time indicated that the exercise-induced changes in physiological measurements, serum lipid or apolipoprotein concentrations, or enzyme activities did not differ between groups. Serum concentrations of TC, LDL-C, and HDL3 cholesterol, TG, and apo A-I and apoB were higher in POM women compared with the PRM group (P < .05 for all). For the combined groups, body weight and relative body fat did not change with training, but VO2max increased an average of 18.5% (P < .05). LPLA, HTGLA, and LCAT activity were unaltered with exercise training. Except for a small but significant decrease in HDL-C (-5.5%) and an elevation in apoB (4.3%; P < .05 for both), the concentrations of serum lipids and apolipoproteins did not change over the training period. We conclude that in previously untrained women, menopausal status does not influence the exercise training response of serum lipids or apolipoproteins or activities of intravascular enzymes related to lipid transport.     

Evaluation of the respiratory inductive plethysmograph in man

We evaluated the respiratory inductive plethysmograph, (RIP), during tidal breathing in eight men and seven women. This device measures movements of the rib cage and abdomen during breathing and adds the signals to produce an indirect record of ventilation. We recorded on magnetic tape, the rib and abdominal signals separately, with a simultaneous ventilation measurement from a pneumotachograph, and analysed them later using a digital computer. One method of calibration, the simultaneous equation technique, was considered in detail. Agreement between the combined RIP signal and a simultaneous ventilation record was normally within 25% except where the calibration was unsatisfactory or the breathing pattern was irregular. The reproducibility of measurements made 5 min apart was good overall, but some subjects showed marked variability. An alternative calibration method which derives indirect isovolume relationships was also examined, but was found to give very erratic results. The most serious error was the alinearity of the rib and abdominal signals, and the problem of describing thoracic movement using only two sensing elements. We conclude that the RIP is a convenient monitor of ventilation during regular tidal breathing, but that it is not quantitative.     

Chest physiotherapy and post-extubation atelectasis in infants

The present study describe the role of copper zinc superoxide dismutase (CuZnSOD) in the short-term treatment of experimental colitis induced with 8% acetic acid. The colonic mucosa damage index in the group of 10 rats treated intravenously with 30,000 U/kg CuZnSOD was significantly decreased when compared with the control group (10 rats) treated with normal saline (0.4 +/- 0.6 vs 1.5 +/- 0.5 p < 0.01). Assay of SOD in the control group was 0.3 +/- 0.08 and in the SOD treated group, SOD was significantly increased to 0.8 +/- 0.1, glutathione peroxidase was 44.8 +/- 6.3 in the control and 56.4 +/- 9.1 in the treated group (difference not significant). Both myeloperoxidase activity (14.0 +/- 2.5 vs 22.7 +/- 2.5) and lipid peroxidation products (13.8 +/- 2.9 vs 52.9 +/- 9.6) were significantly lower in the colonic mucosa of the SOD treated group in comparison with the control. These results indicate that the anti-inflammatory effects of CuZnSOD were mainly the removal of oxygen free radicals and indirectly the prevention of lipid peroxidation. This study suggests that CuZnSOD may be beneficial in the treatment of patients with ulcerative colitis. However, our experimental data suggest that this treatment will not have strong effects on the control of severe ulcerative colitis.     

Development of attention in preterm infants

The quality of the awake state and attention in preterm infants has been evaluated by rating indices of attention such as widening of the eye, type of fixation, brightening, scanning, and cessation of sucking measured during visual fixation of patterns. Twenty-six infants ranging from 28 to 32 weeks' gestation at birth (mean, 31 weeks) were tested from one to four weeks postnatally until 36 weeks' gestation. Indices of attention were rated on a scale of 4 with an optimal mean index of 4. A progressive increase in behaviors associated with fixation of visual stimuli has been shown from 32 to 36 weeks of conceptual age. Mean scores ranged from 0.7 at 31 weeks' gestation to 1.8 at 34 weeks' and 2.7 at 36 weeks' gestation. The possibility therefore exists that by as early as 31 to 32 weeks from conception the human brain may be capable of waking states and thus able to process some sensory stimulation.rease in behaviors associated with fixation of visual stimuli has been shown from 32 to 36 weeks of conceptual age. Mean scores ranged from 0.7 at 31 weeks' gestation to 1.8 at 34 weeks' and 2.7 at 36 weeks' gestation. The possibility therefore exists that by as early as 31 to 32 weeks from conception the human brain may be capable of waking states and thus able to process some sensory stimulation.     

Hepatitis B vaccination in preterm infants

AIM: To investigate the immunogenicity and safety of existing recommendations for hepatitis B vaccination in preterm infants. METHODS: Recombinant hepatitis B vaccine (H-B-VAX II, 5 micrograms per dose) was given to 85 preterm infants divided into two groups, using two different schedules. Forty four group A infants with birthweights of < 2000 g received three doses at 1, 2, and 7 months of age. Forty one group B infants with birthweights of > or = 2000 g received three doses at 0, 1, and 6 months of age. RESULTS: After vaccination, 42 infants from group A (95%) and 37 infants from group B (90%) developed protective levels of antibody. The final seropositive rate and the geometric mean concentration of hepatitis B surface antibody between the two groups were not significantly different. The immune response of preterm infants to hepatitis B vaccines was similar to that of term infants in a previous study. CONCLUSIONS: Preterm infants can be given hepatitis B vaccines using one of the above two different schedules, at a cutoff birthweight of 2000 g.     

Deformation of the palate in preterm infants

AIM: To investigate the effect of gestation, postmenstrual age, and orotracheal intubation on palate morphology. METHODS: A prospective study was made of 76 newborn infants of 25 to 41 weeks' gestation. Palate dimensions were measured on plaster models produced from serial palatal impressions. Palate size relative to that of the mouth was assessed using a ratio of palate depth to palate width (Palatal Index). RESULTS: Palate depth and width were related to postmenstrual age and gestation. Palatal Index ranged from 0.15 to 0.57, indicating a wide variation in palate shape, but gestation and postmenstrual age had no effect. Prolonged intubation had a small effect, equivalent to an increase in palatal depth of less than 2 mm at 32 weeks' postmenstrual age. The effect was transient. CONCLUSION: Prolonged orotracheal intubation (> 10 days) leads to a small and temporary increase in palatal depth. However, this is unlikely to account for palatal grooving, which is probably caused by an overgrowth of the lateral palatine ridges.     

Tracheobronchomalacia in preterm infants with chronic lung disease

Tracheobronchomalacia is a treatable cause of persisting ventilatory requirements in the preterm neonate, and warrants a high index of suspicion. Five preterm infants with persisting ventilatory requirements with evidence of tracheobronchomalacia are reported. Four were diagnosed by tracheobronchogram and one by flexible endoscopy. All were successfully managed by continuous positive airway pressure (CPAP) via a tracheostomy. One infant died of unrelated causes. The oldest child in this series at the age of 2 years requires no further ventilatory support. Tracheobronchial anomalies should be considered in all preterm infants with persisting ventilatory requirements.