Long-term pulmonary functional outcome of bronchopulmonary dysplasia and premature birth.

Pulmonary function and exercise tolerance were evaluated in late childhood in two groups of prematurely born children: one group with bronchopulmonary dysplasia (BPD) [n = 15; gestational age at birth (GA): 29.6 +/- 2.8 weeks; birth weight (BW): 1,367 +/- 548 g; age at test: 7.9 +/- 0.6 years], and a second group without significant neonatal lung disease [pre-term (PT)] (n = 9; GA: 30.3 +/- 1.7 weeks; BW: 1,440 +/- 376 g; age at test: 7.8 +/- 0.22 years). The results were compared with a control group of children of similar ages and heights, born at term [term born (TB)]. We observed that total lung resistance (RL) was significantly higher in BPD (11 +/- 3 cmH2O/L/s), and in PT (9 +/- 2) than in TB [5 +/- 1; (P < 0.001 and P < 0.05, respectively)]. In BPD RL was higher than in PT (P < 0.05). Dynamic lung compliance (CLdyn) was decreased in BPD (43 +/- 11 mL/cmH2O) and in PT (56 +/- 17) compared with TB (76 +/- 20) (P < 0.001 and P < 0.05), and also in BPD compared with PT (P < 0.05). Forced expiratory volume in 1 second (FEV1) and FEV1/forced vital capacity (FVC) were lower in BPD (1.07 +/- 0.15 L and 72 +/- 7%) than in PT (1.29 +/- 0.23 L, and 80 +/- 7%) (P < 0.05). Exercise tests were performed in six boys with BPD. The ratio between minute ventilation at maximal workload (VEmax) and the predicted value of maximal voluntary ventilation (MVV) was elevated in the six BPD boys tested, compared with five boys of Group 2 and five TB boys (87 +/- 15% vs. 62 +/- 14% and 65 +/- 13%) (P < 0.05). We conclude that: 1) prematurity and BPD is followed by long-term airway obstruction and a mild degree of exercise intolerance and; 2) premature birth without BPD may be followed by a milder degree of airway obstruction in childhood than in infants who developed BPD during the neonatal period.

Reliability of pulse oximetry during exercise in pulmonary patients.

To evaluate the reliability of pulse oximetry during exercise, we studied 101 patients primarily with chronic pulmonary diseases. Three devices were used on different patients. Radial arterial blood was sampled at rest and maximal exercise simultaneously to pulse oximetric determination. Measured blood oxygen saturation was significantly different from noninvasive saturation at rest and also at exercise for each device. Nevertheless, changes in pulse oximetry from rest to exercise were significantly correlated with measured saturation for all three devices. Direction of changes in saturation from rest to exercise was correctly evaluated by transcutaneous oximetry in all but six instances where changes were less than 4 percent. Although measured and transcutaneous saturations are significantly different, we conclude that pulse oximetry reliably estimates changes in arterial saturation between rest and exercise for a clinical purpose. None of the three tested devices was better compared with the others in estimating saturation changes at exercise.

Pulmonary function in infancy and in childhood following mechanical ventilation in the neonatal period.

Pulmonary function was evaluated in both infancy and childhood in the same 19 prematurely born infants, who required mechanical ventilation (MV) during the neonatal period. Results of our patients were compared with those of control subjects. Upon first evaluation, we found that lung resistance (RL) was significantly elevated (24.85 +/- 6.06 vs. 17.77 +/- 2.39 cmH2O/L/s; P less than 0.01). The mean value of dynamic lung compliance (CLdyn) was low, but the difference compared to controls did not reach significance. From infancy to childhood, elevated RL persisted (9.33 +/- 2.51 vs. 6.52 +/- 1.52 cm H2O/L/s; P less than 0.01), and the decrease of CLdyn became significant (46.86 +/- 12.84 vs. 59.34 +/- 15.68 mL/cmH2O; P less than 0.05). In addition, maximum flow at functional residual capacity was significantly decreased (0.824 +/- 0.284 vs. 1.215 +/- 0.358 L/s; P less than 0.01); whereas pulmonary diffusing capacity for carbon monoxide was similar in the patients (7.62 +/- 2.16 mL/min/mm Hg) and in the controls (8.38 +/- 1.6). Pulmonary dysfunction following premature birth, respiratory distress, and prolonged MV may not resolve from infancy to childhood.

Diaphragmatic and genioglossus electromyographic activity at the onset and at the end of obstructive apnea in children with obstructive sleep apnea syndrome.

We studied the activity of the diaphragm and of the genioglossus at the onset and at the end of obstructive sleep apnea in children. Seven children (mean age 46 months, range 15-87) with obstructive sleep apneas mainly due to enlarged tonsils were tested during natural sleep. We recorded sleep stages (neurophysiological criteria), nasal and buccal air flow (thermistors), thoracoabdominal motion (magnetometers), genioglossus and diaphragm electromyographic activity (EMG) (surface electrodes), and transcutaneous partial pressure of oxygen (Radiometer 44 degrees C). A total of 153 obstructive apneas for the whole group of patients was studied. Compared to the preceding unoccluded breaths, genioglossus and diaphragm EMG data showed that 1) at the onset of obstructive apnea there was no significant decrease in genioglossus and/or diaphragm EMG, contrasting with published data for obese adults, and 2) at the end of obstructive apnea, significant preferential increase in genioglossus EMG, not related to the decrease in transcutaneous partial pressure of oxygen, was found as in obese adults. This study showed that different mechanisms may control the onset of obstructive apnea in children as compared to adults, whereas children and obese adults share the same preferential increase in genioglossus EMG at the end of obstructive apnea.

Paradoxical inward rib cage motion during rapid eye movement sleep in infants and young children.

In neonates, rib cage motion on inspiration during rapid eye movement sleep is almost exclusively paradoxical. We wondered whether or not duration of paradoxical inward rib cage motion on inspiration during rapid eye movement sleep decreases in infancy and early childhood. Thirteen healthy infants from 7 to 31 months of age were tested during natural afternoon naps. Electroencephalogram, electrooculogram and electromyogram were all recorded. Airflow was measured by nasal and buccal thermistors, abdominal and rib cage anteroposterior diameters by magnetometers. Transcutaneous partial pressure of O2 was monitored. Diaphragmatic electromyographic activity was recorded using surface electrodes. The average total sleep time was 138 min ranging from 107 to 186 and rapid eye movement sleep time amounted to 15% of total sleep time ranging from 6 to 25. During rapid eye movement sleep, the total duration of paradoxical inward rib cage motion was measured and expressed as a percentage of rapid eye movement sleep time. We found that duration of paradoxical inward rib cage motion during rapid eye movement sleep decreased significantly with age (r = -0.66, P less than 0.02) which may be explained by the changes in chest wall compliance and geometry of the rib cage occurring with growth. We observed no decrease in transcutaneous partial pressure in O2 during paradoxical inward rib cage motion during rapid eye movement sleep in infants in contrast to that reported in neonates.

Lung function of children treated for malignant extrapulmonary tumors.

Lung function was studied in 29 children suffering from extrapulmonary tumors of varying etiology (Wilm's tumor, n = 7; bone malignancy, n = 17; nasopharyngeal epithelioma, n = 5). Lung volume: vital capacity (VC) and functional residual capacity (FRC), lung mechanics: lung resistance (RL), dynamic lung compliance (CLdyn) and static lung compliance (CLstat) and lung transfer factor for CO (TLCO), and blood gases were determined at different stages of therapy: at t0, before any aggressive treatment for respiratory function; at t1, after the initiation of polychemotherapy with or without local tumoral treatment (surgery or local irradiation); at t2, less than 6 months after onset of thoracopulmonary irradiation (whole lung irradiation at 20 grays) (group I), or local thoracopulmonary irradiation at high exposure greater than 40 grays (group II); at t3 after more than 6 months following irradiation with chemotherapy maintained; at t4, after cessation of all treatment (mean: 25 months +/- 14 after cessation of treatment). At t0, lung function data in children without pulmonary metastases did not deviate from predicted values. At t1, group I showed a significant decrease in CLdyn, which could be due to chemotherapy and for 5 children to consequences of abdominal surgery. In group II, only two children had a low CLdyn and also a significant decrease in VC (possibly due to the site of the tumor). After irradiation (at t2), FRC, TLCO and CLdyn were significantly lower than the predicted values and lower than at t1 in both groups (p greater than 0.01). At t3, functional parameters did not show any change compared to t2. At t4, FRC and TLCO were within normal limits in both groups but CLdyn, CLstat and the CLdyn/FRC ratio remained significantly decreased. It is suggested that these functional abnormalities are due to inadequate alveolar growth.