Non-ventilated Infants Research Articles

The Effect of Phototherapy on Renal Blood Flow Velocity in Preterm Infants

Mean renal blood flow velocity (RBFV) was studied with two-dimensional/pulsed Doppler ultrasound and relative renal vascular resistance (RVR) was calculated before, during, and after phototherapy treatment in 30 preterm infants (gestational age ≤32 weeks) who were treated for a minimum of 12 h with phototherapy for nonhemolytic hyperbilirubinemia. RBFV decreased, whereas RVR increased significantly after the initiation of phototherapy. In ‘healthy’ (nonventilated) infants RBFV and RVR returned to baseline values after discontinuation of phototherapy. Whereas in ‘unhealthy’ (ventilated) infants, RBFV and RVR did not return to baseline values after discontinuation of phototherapy. In 16 infants (>50% of the cases) the ductus arteriosus reopened during phototherapy.

Transfusion Practices in Infants Receiving Assisted Ventilation

Controversies about medical practices usually arise from lack of definitive scientific studies. In the presence of continuing controversy about the appropriate hemoglobin level for ventilated (or nonventilated) infants, we can attempt to derive as much useful information as possible. In this article, the authors focus on four subjects: the physiologic role of red cells, the clinical effects of anemia and the proposed clinical benefit of red cell transfusions in preterm infants, the risks associated with transfusions, and the use of recombinant erythropoietin as an alternative to transfusion therapy.

The effect of phototherapy on cerebral blood flow velocity in preterm infants.

Cerebral blood flow velocity was studied with two-dimensional/pulsed Doppler ultrasound before, during and after discontinuation of phototherapy in 22 preterm infants (gestational age < or =32 weeks), who were treated for a minimum of 12h with blue-light phototherapy for non-haemolytic hyperbilirubinaemia. Before the cerebral blood flow velocity measurements, patency of the ductus arteriosus was diagnosed by Doppler echocardiography. All infants had normal brain ultrasound scans. Mean cerebral blood flow velocity increased significantly after initiation of phototherapy in all infants. Only in "healthy" (non-ventilated) infants did cerebral blood flow velocity return to pre-phototherapy values (baseline) after discontinuation of phototherapy, whereas in "unhealthy" (ventilated) infants cerebral blood flow velocity did not return to baseline. In 10 infants the ductus arteriosus reopened during phototherapy. In those infants, mean cerebral blood flow velocity returned to pre-phototherapy values after 2 h of phototherapy prior to its discontinuation.

A possible role for the Hering-Breuer deflation reflex in apnea of prematurity

Background: The vagally mediated Hering-Breuer deflation reflex terminates expiration and initiates inspiration when lung volume is reduced to less than functional residual capacity. The effects of prematurity on this reflex are not known. Study design: Fifteen term and 20 preterm nonventilated infants were studied. Lung deflation was achieved by chest compression using an inflatable jacket. Relative changes in expiratory time and inspiratory time on chest compression were calculated from airflow recordings. Esophageal pressure changes in the term infants and chest wall movements in the preterm infants were also measured. Results: The term infants had a mean prolongation of inspiratory time on squeezing of 15% versus a 24% shortening in the preterm infants ( p < 0.001). The term infants had a mean shortening of expiratory time on squeezing of 35% versus 18% in the preterm infants ( p < 0.001). Fifteen of the 20 preterm infants demonstrated a tendency to have short apneas (2 to 5 seconds) on squeezing, 88% of which were central in origin. In these infants shortening of inspiratory time was greater than that seen in the preterm infants not having apneas ( p < 0.05). Conclusions: Preterm infants responded to a rapid reduction in lung volume with a shortened inspiratory effort and a tendency to have central apneas. This may be due to an immaturity in part of the reflex arc responsible for transmitting the Hering-Breuer deflation reflex. (J Pediatr 1998;132:35-9)

Pituitary-Adrenal Response in Preterm Very Low Birth Weight Infants after Treatment with Antenatal Corticosteroids

Antenatal corticosteroids have been widely used for the prevention of respiratory distress syndrome in preterm neonates, yet little is known about their effects on the hypothalamic-pituitary-adrenal axis in these infants. We prospectively evaluated pituitary-adrenal function in 61 preterm (<32 gestational weeks), very low birth weight (<1500 g) infants on days 7 and 14 of life using the human CRH stimulation test. The baseline and poststimulation plasma ACTH and serum cortisol concentrations did not differ significantly between infants whose mothers received no antenatal corticosteroids, and those whose mothers received 1–2 doses or >2 doses (mean 7.2 doses) of prenatal dexamethasone (P = > 0.12). The number of doses of dexamethasone and the time intervals between the last dose of drug and delivery did not significantly affect the pituitary-adrenal responsiveness on days 7 and 14 of life. Among infants who did not require mechanical ventilation at the time of the human CRH test, significantly higher plasma ACTH (P < 0.014) and lower serum cortisol concentrations (P < 0.02) were found on day 14 than on day 7. In contrast, none of the poststimulation hormone concentrations were significantly different in ventilated infants between days 7 and 14. The relationship between the blood hormone concentrations in each time epoch (day 7 and day 14) and possible confounding factors including gestational and postconceptional age, birth weight, sex, Apgar scores, mode of delivery, single or higher order births, and mode of ventilation were determined. Plasma ACTH concentrations on day 7 were found to be significantly higher in ventilated than in nonventilated infants (P = 0.006). However, none of the aforementioned factors correlated significantly with plasma ACTH concentrations on day 14. Serum cortisol concentrations on day 7 were significantly higher in infants of greater gestational age (P = 0.039) and birth weight (P= 0.013), with lower Apgar scores at 1 and 5 min (P= 0.021 and P = 0.049, respectively), and in those delivered vaginally (P = 0.047). Similarly, serum cortisol concentrations on day 14 were found to be significantly higher in infants with lower Apgar scores at 1 and 5 min (P = 0.011 and P = 0.014, respectively) and in infants requiring mechanical ventilation (P = 0.014). Our results suggest that single or multiple courses of antenatal dexamethasone have no long-lasting suppressive effects on pituitary-adrenal function in preterm, very low birth weight infants. Maturation of pituitary function appears to be more advanced than adrenal function. The organ’s ability to respond appropriately to various stressful stimuli indicates that the pituitary-adrenal axis is highly responsive at these early gestational ages.

Pituitary-adrenal response in preterm very low birth weight infants after treatment with antenatal corticosteroids.

Antenatal corticosteroids have been widely used for the prevention of respiratory distress syndrome in preterm neonates, yet little is known about their effects on the hypothalamic-pituitary-adrenal axis in these infants. We prospectively evaluated pituitary-adrenal function in 61 preterm (< 32 gestational weeks), very low birth weight (< 1500 g) infants on days 7 and 14 of life using the human CRH stimulation test. The baseline and poststimulation plasma ACTH and serum cortisol concentrations did not differ significantly between infants whose mothers received no antenatal corticosteroids, and those whose mothers received 1-2 doses or > 2 doses (mean 7.2 doses) of prenatal dexamethasone (P = > 0.12). The number of doses of dexamethasone and the time intervals between the last dose of drug and delivery did not significantly affect the pituitary-adrenal responsiveness on days 7 and 14 of life. Among infants who did not require mechanical ventilation at the time of the human CRH test, significantly higher plasma ACTH (P < 0.014) and lower serum cortisol concentrations (P < 0.02) were found on day 14 than on day 7. In contrast, none of the poststimulation hormone concentrations were significantly different in ventilated infants between days 7 and 14. The relationship between the blood hormone concentrations in each time epoch (day 7 and day 14) and possible confounding factors including gestational and postconceptional age, birth weight, sex, Apgar scores, mode of delivery, single or higher order births, and mode of ventilation were determined. Plasma ACTH concentrations on day 7 were found to be significantly higher in ventilated than in nonventilated infants (P = 0.006). However, none of the aforementioned factors correlated significantly with plasma ACTH concentrations on day 14. Serum cortisol concentrations on day 7 were significantly higher in infants of greater gestational age (P = 0.039) and birth weight (P = 0.013), with lower Apgar scores at 1 and 5 min (P = 0.021 and P = 0.049, respectively), and in those delivered vaginally (P = 0.047). Similarly, serum cortisol concentrations on day 14 were found to be significantly higher in infants with lower Apgar scores at 1 and 5 min (P = 0.011 and P = 0.014, respectively) and in infants requiring mechanical ventilation (P = 0.014). Our results suggest that single or multiple courses of antenatal dexamethasone have no long-lasting suppressive effects on pituitary-adrenal function in preterm, very low birth weight infants. Maturation of pituitary function appears to be more advanced than adrenal function. The organ's ability to respond appropriately to various stressful stimuli indicates that the pituitary-adrenal axis is highly responsive at these early gestational ages.

Technical and methodologic considerations for performance of indirect calorimetry in ventilated and nonventilated preterm infants.

To evaluate and refine indirect calorimetry measurement techniques so that accurate metabolic measurements can be performed in mechanically ventilated and convalescing preterm infants who require supplemental oxygen. Laboratory validation of an indirect calorimeter; clinical and laboratory assessments of technical problems in performing metabolic measurements; and clinical indirect calorimetry studies in mechanically ventilated and nonventilated preterm infants. Neonatal intensive care unit (ICU) in a tertiary care university hospital. Level II and level III mechanically ventilated (n = 10) and nonventilated (n = 14) neonatal ICU patients who required FIO2 levels ranging from 0.21 to 0.42. None. System calibration was assessed by combustion of 100% ethanol; the mean respiratory quotient was 0.667 +/- 0.001 (SEM). In addition, oxygen consumption (Vo2) and CO2 production (Vco2) were simulated by CO2/nitrogen infusions within the range expected for 0.5- to 7-kg infants. Mean relative errors were 0.6 +/- 0.3% and 1.8 +/- 0.3% for expected Vo2 and Vco2 values, respectively. In 27 mechanically ventilated patients with no audible endotracheal tube leak, measured endotracheal tube leak ranged from 0.0% to 7.5%. Fluctuations in FIO2 during mechanical ventilation were monitored in 30-min studies, using wall-source (n = 27) or tank-source (n = 11) supplemental oxygen. Mean FIO2 variation was 0.00075 +/- 0.00013 vs. 0.00011 +/- 0.00001 using wall-source and tank-source oxygen, respectively. Some of the difficulties of obtaining accurate measurements in supplemental hood oxygen studies were overcome by using tank-source vs. wall-source oxygen and a unique hood design. Accurate indirect calorimetry studies can be performed in both ventilated and nonventilated infants weighing as little as 500 g, providing that sufficient attention is paid to technical and methodologic measurement details.

Efficiency of aerosol medication delivery from a metered dose inhaler versus jet nebulizer in infants with bronchopulmonary dysplasia

The best means for optimal delivery of drugs into lungs of infants with bronchopulmonary dysplasia (BPD) is uncertain. We aimed to measure radio-aerosol deposition of salbutamol by jet nebulizer and metered dose inhalers (MDI) in ventilated and non-ventilated BPD infants. In a randomized, crossover sequence, salbutamol lung deposition was measured using an MDI (2 puffs or 200 micrograms) or sidestream jet nebulizer (5 minutes of nebulization with 100 micrograms/kg) in 10 ventilated (mean birthweight, 1,101 g) and 13 non-ventilated (mean birthweight, 1,093 g) prematurely born infants. Non-ventilated infants inhaled aerosol through a face mask, connected to a nebulizer or an MDI and spacer (Aerochamber). Ventilated infants received aerosol from an MDI + MV15 Aerochamber or a nebulizer inserted in the ventilator circuit. Lung deposition by both methods was low: mean (SEM) from the MDI was 0.67 (0.17)% of the actuated dose, and from the nebulizer it was 1.74 (0.21)% and 0.28 (0.04)% of the nebulized and initial reservoir doses, respectively. Corresponding figures for the ventilated infants were 0.98 (0.19)% from the MDI and 0.95 (0.23)% and 0.22 (0.08)% from the nebulizer. In both groups, and for both methods of delivery, there was marked inter-subject variability in lung deposition and a tendency for the aerosol to be distributed to the central lung regions.

SURVIVAL OF INFANTS WITH BIRTH WEIGHT (BW) LESS THAN 501 GRAMS (g).† 1621

Objective: To determine the number and outcome of infants with BW < 501 g at 54 Neonatal Intensive Care Units participating in the Vermont Oxford Neonatal Network. Methods: Pre-defined perinatal and neonatal outcome data were collected on standardized forms for all live births with BW < 501 g during one year (June 1, 1994 - May 31, 1995). Results: There were 391 liveborn infants evaluated of whom 95 were intubated and ventilated, and 296 were not. Ventilated infants, compared to non-ventilated infants, were more likely to have received antenatal steroids (35% vs. 4%, p<0.001), to be delivered by cesarean section (43% vs. 4%, p<0.001), to be more mature(mean gestational age 24 weeks vs. 21 weeks, p<0.001), and to be heavier(mean BW 444 g vs. 370 g, p<0.001). Most deaths (81%) occurred within the first day of life; few infants (1%) died after 28 days. No infant born less than 320 grams or less than 22 weeks survived. Twenty four infants survived to discharge, all of whom were ventilated, and received surfactant. Among survivors, 22 of 24 (92%) received steroids for chronic lung disease. One survivor had grade IV intraventricular hemorrhage (IVH), whereas 17 of 24(71%) had no IVH. The mean hospital stay for survivors was 127 ± 22 days. Conclusions: Some infants with BW < 501 g selected for intubation and ventilation can survive to discharge to home. Further study will be needed to better understand the selection criteria used to offer resuscitation to these extremely low BW infants, and determine the long term neurodevelopmental outcome of the survivors.

Low birthweight infants and total parenteral nutrition immediately after birth. I. Energy expenditure and respiratory quotient of ventilated and non-ventilated infants.

The aim of this study was to determine the energy expenditure and respiratory quotient (RQ) of ventilated and non-ventilated low birthweight infants during the first five days of life, in order to determine optimal feeding regimens. Eighty six infants, of birthweight less than 1750 g, were grouped according to whether they were artificially ventilated or breathing air spontaneously, and whether they were parenterally or enterally fed at the time of study. Energy expenditure and respiratory quotient were measured during days 1-5 and the relation of energy expenditure to several explanatory variables was investigated using multiple regression analysis. The energy expenditure of ventilated infants was less than that of spontaneously breathing infants; the differences were significant on days 1-3. The respiratory quotient (mean (SE)) was greater in intravenously fed infants compared with milk-fed--0.99 (0.03) v 0.92 (0.01) (P < 0.05), with 42% of studies of infants receiving total parenteral nutrition (TPN) producing an RQ of > 1.0 compared with 16.6% of milk-fed infants (P < 0.01). There was a significant correlation between glucose intake and RQ (r = 0.39, P < 0.001). The activity scores were measured during 75 studies and scores were significantly higher in spontaneously breathing milk-fed infants compared with ventilated parenterally fed infants. Factors independently related to energy expenditure were: postnatal age (P < 0.01); milk feeds (P < 0.01); and physical activity (P < 0.05). A mix of carbohydrate and fat from day 1 may not only meet energy needs but may also reduce respiratory quotient.

A new equation to predict the resting energy expenditure of surgical infants

It is essential that adequate calories are provided to newborns to cover their energy expenditure. This is difficult to measure and varies significantly between individuals. The aim of this study was to develop an equation to predict the basal energy requirements of stable surgical infants, using easily measurable parameters. Resting energy expenditure (REE) was measured using computerized open-circuit indirect calorimetry. One hundred twenty-two measurements were made on different days in 46 stable nonventilated infants. The measured REE was 34.41 ± 0.46 cal/kg/min; (mean ± SEM). Three body-size measurements correlated significantly with REE (cal/min): weight in kilograms ( r = .87; P < .00001), body surface area in square meters ( r = .86; P < .00001), and lean body mass in kilograms ( r = .81; P < .00001). Five other independent variables correlated significantly with REE (cal/kg/min): heart rate in beats per minute ( r = .60; P < .00001), postnatal age in days ( r = .49; P < .00001), caloric intake in cal/kg/min ( r = .44; P < .00001), gestational age in weeks ( r = .43; P < .00001), and rectal temperature in degrees Celsius ( r = .19; P = .04). Weight, heart rate, age, gestational age, and temperature were regarded as independent predictor variables of REE for the multiple stepwise regression analysis. Three variables entered this highly significant equation: REE (cal/min) = −74.436 + (34.661 × weight in kg) + (0.496 × heart rate in beats/min) + (0.178 × age in days) ( r = .92; F = 230.07; significance, F < .00001). Thirteen additional studies were performed on nine stable surgical infants to test the validity of this equation. The correlation between predicted and measured REE was 0.89. The error in predicting REE from the equation was −.95 ± 3.65%.

The Impact of an Insult or Disability from Birth on Infants' Ability to Organize and Interpret Multiple Sources of Information

Observing the behavior of at-risk infants as they interact with their environment may provide information about the way in which they organize and interpret multiple sources of information. This study was conducted at a regional neonatal intensive care unit (NICU) follow-up clinic to investigate the impact of a stressful birth on infants' performance during selected tasks. Infants between the adjusted ages of 91 days and 240 days were observed during three tasks that required integrating multiple stimuli: (a) a task of spatial perception, (b) a task of intermodal representation of speech, and (c) a contingency learning task. Seven birth-status variables (gestational age, birthweight, adjusted age, length of ventilation, 5-minute Apgar scores, parent education, and parent income levels) compiled from hospital records were compared to seven performance variables (reach, vision, smile, fuss, attention, speech, and contingency). Multiple regression analyses were applied to the data. Findings from the study indicate that (a) mechanically ventilated infants were more irritable than nonventilated infants, (b) infants from lower-income families were fussier than infants from higher-income families, (c) lower-birthweight infants were more successful on the visual task than higher-birthweight infants, (d) 5-minute Apgar scores were more predictive of infants' success than 1-minute scores on the visual task, (e) older infants were more accurate during the reaching task than younger infants.

The Hering-Breuer reflex during the first year of life in healthy infants : P.S. Rabbette a, M.E. Fletcher b, C.A. Dezateux b, H. Childs b, K.L. Costeloc a and J. Stocks b, aDepartment of Neonatal Medicine, Homerton Hospital and bRespiratory and Anaesthetic Unit, Institute of Child Health, London, U.K.

Background: The vagally mediated Hering-Breuer deflation reflex terminates expiration and initiates inspiration when lung volume is reduced to less than functional residual capacity. The effects of prematurity on this reflex are not known. Study design: Fifteen term and 20 preterm nonventilated infants were studied. Lung deflation was achieved by chest compression using an inflatable jacket. Relative changes in expiratory time and inspiratory time on chest compression were calculated from airflow recordings. Esophageal pressure changes in the term infants and chest wall movements in the preterm infants were also measured. Results: The term infants had a mean prolongation of inspiratory time on squeezing of 15% versus a 24% shortening in the preterm infants (p < 0.001). The term infants had a mean shortening of expiratory time on squeezing of 35% versus 18% in the preterm infants (p < 0.001). Fifteen of the 20 preterm infants demonstrated a tendency to have short apneas (2 to 5 seconds) on squeezing, 88% of which were central in origin. In these infants shortening of inspiratory time was greater than that seen in the preterm infants not having apneas (p < 0.05). Conclusions: Preterm infants responded to a rapid reduction in lung volume with a shortened inspiratory effort and a tendency to have central apneas. This may be due to an immaturity in part of the reflex arc responsible for transmitting the Hering-Breuer deflation reflex. (J Pediatr 1998;132:35-9)

Food and drug reactions, wheezing, and eczema in preterm infants.

Allergic reactions were investigated in 777 preterm infants who were randomly assigned to early diet and followed up to 18 months post term. Wheezing or asthma was common (incidence 23%); it was associated with neonatal ventilation, maternal smoking, and a family history of atopy and was unexpectedly reduced in babies born by caesarean section. Even in non-ventilated infants, the incidence of subsequent wheezing was 18%, rising to an estimated 44% (using logistic regression) when the foregoing risk factors (excluding ventilation) were present. Eczema occurred in 151 infants (19%) and was strongly associated with multiple pregnancy (30% incidence in twins or triplets). Reactions to cows' milk (incidence: 4.4% from detailed history; 0.8% confirmed by challenge), other foods (10%), and drugs (5%) were within the range reported in full term infants. Milk and food reactions were associated with multiple pregnancy (19%) and a family history of atopy. Reactions to drugs were least likely to occur in infants who had been ventilated and were on multiple medications in the neonatal period, suggesting that drug tolerance may have developed. We speculate that preterm infants may be a high risk group for asthma and eczema, which could imply an association between atopy and prematurity.

Cerebral blood flow in newborn infants with and without mechanical ventilation

The influence of mechanical ventilation with low mean airway pressure (MAP) on cerebral blood flow (CBF) veolocity in newborn infants was assessed in fifteen ventilated infants by Duplex Doppler Sonography (Duplex DS). As a control, CBF velocities were examined in 15 age and weight matched non-ventilated infants. For quantitation, maximal systolic velocity, enddiastolic velocity and the semiquantitative Pourcelot index were determined as representative flow variables. There was no significant difference of these flow variables between ventilated and non-ventilated infants. The pH, pO2 and pCO2 did not differ significantly between the two groups and there was no correlation between the flow variables, pH, pO2, pCO2 or MAP. Mechanical ventilation with low MAP is not associated with adverse effects on cerebral hemodynamics in newborn infants when significant alterations of the blood gases are avoided.

Disturbance in respiratory mechanics in infants with bronchiolitis.

The passive flow-volume and partial forced expiratory flow-volume techniques were used to assess pulmonary function in 14 spontaneously breathing infants with acute respiratory syncytial virus bronchiolitis. Two additional infants were studied while paralysed and ventilated. During the acute stage of the illness there was a significant reduction in forced expiratory flow rates and an increase in respiratory resistance. Although the mean thoracic gas volume for the group was increased, five infants did not compensate for their airways obstruction by hyperinflation. Curvilinear passive flow-volume curves were seen in three of the 14 non-ventilated infants and in both ventilated infants. At follow up three to four months later all passive flow-volume curves were linear. There was a significant reduction in hyperinflation and an increase in forced expiratory flow rates, but values still differed significantly from those in normal infants.

An analysis of potential biases in the loss of indigent infants to follow-up

Loss to follow-up is a major problem in indigent inner-city populations. We evaluated a large, well-described, inborn indigent population of high-risk infants (HRI) and control infants (CI) to assess possible selection biases in loss to follow up at one year adjusted age. Serial clinic visits, phone calls, and letters and payment of $20.00 for attending at 1 year was used to minimize patient loss. Yet, the 1 year loss rate was high, and among HRI, greater for ventilator-treated infants > 1500 g birthweight ( 71 114 ; 62%) than for ventilator-treated very-low birthweight (VLBW; < 1500 g) infants ( 39 108 ; 36%) or non-ventilated VLBW infants ( 62 145 ; 43%) ( P < 0.05). Multivariate analyses indicated that those lost to follow-up were at no greater risk of a poor outcome on the basis of prenatal and perinatal medical and socioeconomic findings than were those in the same risk group (HRI or CI) or subgroup of HRI who were examined at 1 year. In a review of hospital records, similar rates of hospitalization and neurologic problems during infancy were identified for HRI examined and HRI lost to follow-up. The identification of such morbidity during infancy may be less complete for HRI lost to follow-up than for those examined. Thus, the high frequency of deficits observed in follow-up evaluation of indigent HRI is unlikely to result from loss of unaffected infants.

Infants Weighing 1,000 Grams or Less at Birth: Developmental Outcome for Ventilated and Nonventilated Infants

The neurodevelopmental outcome at a mean age of 40 months was investigated in 23/25 surviving infants of birth weights less than or equal to 1,000 gm. Eight infants required intubation and assisted ventilation and 17 were not ventilated. One ventilated infant was lost to follow-up and one nonventilated infant was a victim of sudden infant death syndrome at age 6 months. Fifteen (65%) had a good outcome but the differences between ventilated and nonventilated infants were striking. Thirteen (81%) of the nonventilated group were normal, but only two ventilated survivors (28%) were normal (P less than 0.05). Cicatricial retrolental fibroplasia occurred in three (43%) of the ventilated survivors and in none of the nonventilated infants (P less than .02). The requirement for assisted ventilation in these very low-birth-weight infants is associated with significant morbidity. Improvement in outcome may depend as much upon better understanding and management of prenatal events as upon improvements in neonatal care.

Airway Resistance in Infants After Various Treatments for Hyaline Membrane Disease: Special Emphasis on Prolonged High Levels of Inspired Oxygen

Thoracic gas volume, airway resistance (Raw), and dynamic lung compliance (CL) were measured in 48 infants surviving after hyaline membrane disease. Some infants were found to have a small reduction in CL after recovery from the acute phase of the illness but no other abnormalities were detected, irrespective of the type of treatment received. When studied again between the ages of 4 and 10 months, CL had returned to normal, but all infants who had been treated with intermittent positive pressure ventilation (IPPV) during the neonatal period were found to have developed a raised Raw. In contrast, all nonventilated infants, including those who had received up to five days of oxygen therapy in concentrations above 80%, had normal lung function. We conclude that IPPV, and not the increased inspired oxygen concentration, damaged the airways and interfered with their growth.

PULMONARY FUNCTION STUDIES DURING THE FIRST YEAR OF LIFE IN INFANTS RECOVERING FROM THE RESPIRATORY DISTRESS SYNDROME

Serial measurements of pulmonary function during the first year of life were obtained in 38 premature infants following recovery from respiratory distress syndrome (RDS). Twenty-seven similar weight normal prematures were studied as controls. Serial measurements were made of functional residual capacity, dynamic compliance, and arterial blood gases. All infants following the acute phase of RDS showed decreases in functional residual capacity and/or dynamic compliance, arterial PO2 and mild to severe carbon dioxide retention. Nine nonventilated infants returned to normal by age 2 to 4 months. Eight of 11 infants ventilated for RDS with subsequent development of bronchopulmonary dysplasia died by age 5 months. The 3 survivors had increased FRC, markedly decreased dynamic compliance, relative hypoxia, and carbon dioxide retention throughout the first year. Eighteen ventilated infants with clinical recovery showed considerable individual variations, but the mean group arterial PO2 was lower than normal from 6 to 12 months of age. Abnormalities in chest radiographs were common in infants after ventilation and readmission to hospital for respiratory problems during the first year of life occurred in 8 of 21 surviving infants initially ventilated for RDS.