The Functional Residual Capacity of Infants with Respiratory Distress Syndrome

Abstract

Positive end-expiratory pressure (PEEP) is used in the treatment of infants with respiratory distress syndrome (RDS) to prevent atelectasis, recruit alveolar space and return the functional residual capacity (FRC) toward normal volumes. This study determined the FRC range of 15 prematurely born infants with RDS receiving PEEP. Ventilator settings were controlled clinically using predominantly results of arterial blood-gas analyses. Measurements of arterial blood-gases and FRC (N2 washout) were made during the infants' second day of life. The FRC of the infants on a PEEP of 4.5 +/- 1.3 cmH2O ranged widely from 3 to 33 ml/kg with a mean of 14.5 ml/kg; 17 +/- 2 ml/kg was considered normal. The FRC was within one SD of the mean in only three of the 15 infants (20%) and outside of two SD of normal in seven (47%). A linear regression of calculated alveolar-arterial oxygen gradient (AaDo2) with FRC yielded a correlation coefficient r = 0.825. The AaDo2 values could be used to identify six of the seven infants having FRC outside of 2SD from normal. We conclude that convential methods of PEEP selection for infants with RDS seldom result in a normalization of FRC. Calculated AaDo2 values may be used to identify most RDS infants with FRC widely divergent from normal values.

Lung Volume, Gas Mixing, and Mechanics of Breathing in Mechanically Ventilated Very Low Birth Weight Infants with Idiopathic Respiratory Distress Syndrome

“…They have also presented later work on a similar material with intermittent positive pressure ventilation, using the same technique, with a FRC of 14.5 mL/kg body weight (24). Heaf et al (25) Differences in mode of ventilation may have contributed to these discrepancies (23,26). We can consequently confirm the observations that infants with IRDS and a demand for respiratory support have lower FRC than comparable groups without lung disease (27)(28)(29)(30).…”

“…Richardson et al (23) presented data on 32 intubated, spontaneously breathing newborn preterms on continuous positive airway pressure with a mean body weight of 2.013 kg and a mean FRC of 21.4 mL, using a nitrogen washout technique. They have also presented later work on a similar material with intermittent positive pressure ventilation, using the same technique, with a FRC of 14.5 mL/kg body weight (24).…”

Functional Residual Capacity in Ventilated Infants and Children

“…There are no data on "norma l" FRC values in ventilated children without lung disease when a presumed "physiologic" level of PEEP (2-4 em H 2 0 ) is applied; neither is there information on FRC in ventilated children with ARF. The only information presently available is from studies in adults (2), prematurely born infants with respirato ry distress syndrome (6) , and animal models (7).…”

Lung Function Tests in Neonates and Infants with Chronic Lung Disease of Infancy: Functional Residual Capacity

“…69 Although a wide range of FRCs (from as low as a mean of 7.8 ml/kg to 15.5 ml/kg) was reported in ventilated infants with RDS using clinically determined PEEP ($4 cm H 2 O) and prior to surfactant administration, these values are significantly lower than those predicted from reference data generated in healthy infants breathing without assistance. 2,82,[91][92][93] The effect of varying PEEP level on FRC was assessed systematically. 24,69,70,74,94 Increasing PEEP consistently results in increases in FRC and oxygenation, 74,94 but the correlation between DPEEP and DFRC seems nonlinear.…”