Jacob G. Schwartz

Improved oxygenation and lung compliance withprone positioning of neonates

Fourteen intubated infants recovering from neonatal respiratory disease had arterial blood gases and lung mechanics measured in the supine position and in two variants of the prone position. Prone positioning resulted in significant increases in mean (+/- SEM) arterial oxygen tension (Pa(o2 70.4 +/- 2.5 to 81.1 +/- 4.4mm Hg), dynamic lung compliance (1.7 +/- 0.24 to 2.55 +/- 0.37 ml/cm H2O),and tidal volume (8.6 +/- 1.0 to 10.5 +/- 1.2 ml) when all prone values were compared to supine values. Prone positioning with the abdomen protruding freely, when compared to all supine values, was associated with significantly increased dynamic lung compliance and tidal volume. Values for prone-abdomen free were not significantly different from values for prone-abdomen restricted. This suggests that there are clinical benefits from prone positioning in neonates recovering from respiratory disease.

Pulmonary physiotherapy in neonates:Physiologic changes and respiratory management

To investigate physiologic alterations in respiratory function associated with chest physiotherapy, arterial blood gases, respiratory patterns, lung mechanics, and functional residual capacity were measured in 13 neonates (weights 1.25 to 3.20 kg) during the control period, after vibration of the chest and suctioning, after hyperventilation, and two hours after suctioning. Compared to control values, mean PO2decreased significantly after suctioning to 43 mm Hg and increased significantly after hyperventilation to 78 mm Hg. There was a significant decrease in inspiratory resistance and a trend toward decrease in expiratory resistance after suctioning, with return to control levels after hyperventilation. Respiratory rate increased significantly after suctioning. Functional residual capacity, dynamic lung compliance, and tidal volume, as well as PCO2 and base excess, were not changed appreciably throughout the protocol. Because of potentially severe hypoxemia, this study suggests that suctioning and hyperventilation are not warranted on a routine basis in infants recovering from respiratory diseases.

Theophylline therapy in bronchopulmonary dysplasia.

BRONCHOPULMONARY DYSPLASIA is the most common neonatal pulmonarY disease requiring long-term mechanical ventilation. After establishing this diagnos!s, current therapy includes fluid restriction, diuretics, digitalization, and chest physiotherapy. During weaning and long-term management, several complications may occur, such as increased secretions, recurrent atelectasis, intermittent bronchospasm, and difficulty weaning from mechanical ventilation to continuous positive airway pressure. These complications may be related either to increased airway resistance or to unstable maintenance of lung volume; Although the pathologic changes in bronchopulmonary dysplasia result in increased airway resistance/there have been few clinical reports on the efficacy of bronchodilators for treating bronchopulmonary dysplasia? To establish the effect of theophylline therapy, a group 0fneonates with bronchopulmonary dysplasia .were treated with aminophylline intravenously, followed by measurements of serial pulmonary function tests and serum theophylline levels.

Effects of endotracheal tube leaks on functional residual capacity determination in intubated neonates.

Summary: The present study evaluates a new closed circuit helium (He) dilution technique for determination of endotracheal (ET) tube leakage and functional residual capacity (FRC) in neonates with ET tubes. By analytically relating the fall in He concentration due to mixing with that due to leakage, it is possible to predict the final equilibration concentration of He and, therefore, correct for ET tube leaks. The system (120 ml) contains an air pump, He meter, breathing bag in cylinder, a strip chart readout, and solenoid valve. Continuous positive airway pressure (CPAP) or ventilator pressure can be applied during testing. FRC measurements were performed on 13 neonates (700–4500 g) on CPAP with ET tubes. Leak rates were significantly higher (P < 0.001) on 3 cm H2O CPAP compared to 0 cm H2O CPAP. The mean measured FRC was 53.5 ml at 3 cm H2O and 46.3 ml at 0 cm H22O CPAP. If gas leakage had not been considered in FRC calculations, the error in FRC could have been as high as 39% at 3 cm H2O CPAP and 18% at 0 cm H2O CPAP.Speculation: The present, technique provides a high degree of accuracy for determining FRC and ET tube leakage in critically ill infants on CPAP. Although measurements were not conducted on CPAP levels above 3 cm H2O, it is possible that higher levels of pressure may result in even greater leakage. Under these conditions FRC could only be determined accurately with this method.

Successful extubation of neonates: clinical and physiological factors.

Arterial blood gases, pulmonary mechanics, lung volume measurements and clinical profiles were determined pre and postextubation in 19 infants recovering from respiratory disease. This study evaluated clinical and physiological factors which may be valuable in predicting successful extubation in neonates. Of the 19 patients, 4 required reintubation within 72 h. In this group of patients, the combined profile of low birth weight (1050 g), low gestational age (31 weeks), and high pulmonary resistance (inspiratory 278 cm H2O/L · sec, expiratory 309 cm H2O/L · sec) was significantly different from the 15 patients who were successfully extubated. In addition, lower pHa after extubation was also characteristic of those infants requiring reintubation.

Cardiopulmonary changes in the crying neonate.

Summary: To determine hemodynamic effects of crying, 12 newborn infants recovering from the respiratory distress syndrome (RDS) were studied.When crying, the range of inspiratory esophageal pressure was - 18.8 to −32.5 cm H2O and the range of expiratory pressure was +6.2 to +34.4 cm H2O. The esophageal pressure remained positive for a mean value of 66% of the respiratory cycle. There was a mean significant increase in heart rate of 19 beats/min. The systolic and diastolic blood pressures increased significantly at the beginning of strain to 115 and 135% of the respective control values. There was a progressive decrease in systolic and diastolic pressures during the period of strain and the systolic pressures reached values significantly less than control. With the decrease in systolic and diastolic pressures, there were pronounced reductions in pulse pressures. Three infants reached pulse pressure values less than 1% of control when cries were sustained for nine cardiac cycles.There was a significant mean decrease in arterial oxygen tension (PaO2) of 16.8 mm Hg. There were no changes in arterial carbon dioxide tension (PaCO2), pH, or base excess.Speculation: Asphyxiated nconates and infants with RDS often have a compromised circulation with hypoxemia and hypotension. This study suggests that the circulatory status in such infants may be further compromised by extended periods of crying. In three patients who were relatively stable and normovolemic, a profound decrease in pulse pressure was observed when the cry included seven or more cardiac cycles. These transient periods of no aortic flow might be of clinical significance in critically ill infants. The decreased frequency of crying observed in critically ill neonates may be beneficial to both oxygenation and hemodynamic stability.

The effect of external expiratory resistance on lung volume and pulmonary function in the neonate

To investigate the acute physiologic effects of external expiratory resistance on lung function in extubated neonates recovering from respiratory disease, lung mechanics, respiratory patterns, and function residual capacity were measured in ten neonates during a control period and immediately after application of an external expiratory resistance of 30 cm H 2 O/l/second via a face mask. Following application of EER, mean FRC increased by 40.8% ( P

1242 THE EFFECTS OF DIFFERENT BODY POSITIONS ON PULMONARY FUNCTION IN NEONATES RECOVERING FROM RESPIRATORY DISEASE

To evaluate alterations in pulmonary function with positioning, 9 intubated neonates (wt. [mean] 2.3 kg., gest. age 34 wks., FiO2 .29, CPAP or PEEP 4 cm H2O) were studied in 4 positions (SC= supine control, PR=prone-abdomen restricted, PF=prone-abdomen hanging free, SF=supine followup). After 30 min. in each position; arterial blood gases, lung mechanics, and funct. residual cap. (FRC) were measured. Mean values in supine control were: pO2 67 torr, pC02 42 torr, RR 54 breaths/min., lung compliance (CL) 1.7 ml/cm H2O, tidal volume (VT) 4.15 cc/kg, minute ventilation (VE) 263 ml/kg/min, FRC 26 ml/kg. In PR compared to SC: pO2 increased 12 torr (mean); FRC decreased 15%. In the PF compared to SC: pO2 increased 15 torr, mean FRC was unchanged but increased in 5/8 pts. In PF compared to PR: pO2 increased 6 torr; mean FRC was unchanged but increased in 5/7 pts. All comparisons of CL, pCO2, VE between the above groups were unchanged. In SF compared to PF: pO2 decreased 9 torr, FRC decreased 27%, CL decreased 44%, pCO2 was unchanged, VE decreased 20%. Summary of trends: 1) compared to supine control pO2 increased in both prone positions and FRC decreased in prone-abdomen restricted; 2) PF was better of 2 prone positions for increasing FRC. This study demonstrates that prone positioning improves oxygenation in neonates and that the prone-abdomen free is the best prone position for increasing lung volumes in infants with respiratory disease.

ALTERATIONS IN NEONATAL RESPIRATORY FUNCTION FOLLOWING CHEST PHYSIOTHERAPY

Percussion, suctioning and hyperventilation have been recommended for airway management in neonates requiring endotracheal tubes. To investigate physiological alterations in respiratory function due to chest physiotherapy, we measured arterial blood gases, respiratory patterns, lung mechanics, and functional residual capacity (FRC) in 10 neonates, weights (1.25 to 3.20 kg) during the control period, post vibration of the chest and suctioning, after hyperventilation, and 2 hours post suctioning. Post suctioning compared to controls mean (± SEM) PaO2 decreased 75.2 (± 9.3) to 44.0 (±3.1) mm Hg (P<0.01) while lung compliance and FRC were unchanged. There was a decrease in inspiratory resistance (RI) from 81.8 (± 14.6) to 59.0 (± 10.6) cm H2O/L/sec. (P<0.02) and I:E ratio increased from 0.93 (± 0.04) to 1.04 (± 0.06) (P<0.07). Hyperventilation compared to post suctioning resulted in an increase in mean (± SEM) PaO2 to 63.9 (± 10.0) mmHg (P<0.01), and RI to 98.3 (± 22.0) cm H2O/L/sec. (P<0.05). FRC, CL, VT were unchanged. Two hour followup values for all parameters studied were similar to control values except for a trend toward increased compliance. There were no significant differences at any stage of the study for PaCO2, pH, base excess, VT, or minute ventilation. This study indicates that there is a significant decrease in PaO2 after chest vibration and suctioning increase in PaO2 after hyperventilation but these changes do not appear to be related to alterations in lung volume.

Computer Assisted Evaluation and Computation of Pulmonary Function in the Critically Ill Neonate

At the Infant Intensive Care Unit of The Children’s Hospital of Philadelphia, approximately 500 newborn infants are admitted each year with various forms of respiratory disease, such as Respiratory Distress Syndrome, Meconium Aspiration Syndrome, and Neonatal Apnea. In these situations, when oxygen and carbon dioxide gas exchange is significantly compromised, it becomes necessary to apply respiratory support such as mechanical ventilation, continuous positive airway pressure (CPAP) and/or increased inspired oxygen concentration (FiO2) to maintain adequate vital signs.