Lung resistance and elastance in spontaneously breathing preterm infants: effects of breathing pattern and demographics.

Reported values of lung resistance (RL) and elastance (EL) in spontaneously breathing preterm neonates vary widely. We hypothesized that this variability in lung properties can be largely explained by both inter- and intrasubject variability in breathing pattern and demographics. Thirty-three neonates receiving nasal continuous positive airway pressure [weight 606-1,792 g, gestational age (GA) of 25-33 wk, 2-49 days old] were studied. Transpulmonary pressure was measured by esophageal manometry and airway flow by face mask pneumotachography. Breath-to-breath changes in RL and EL in each infant were estimated by Fourier analysis of impedance (Z) and by multiple linear regression (MLR). RL(MLR) (RL(MLR) = 0.85 x RL(Z) -0.43; r(2) = 0.95) and EL(MLR) (EL(MLR) = 0.97 x EL(Z) + 8.4; r(2) = 0.98) were highly correlated to RL(Z) and EL(Z), respectively. Both RL (mean +/- SD; RL(Z) = 70 +/- 38, RL(MLR) = 59 +/- 36 cm H(2)O x s x l(-1)) and EL (EL(Z) = 434 +/- 212, EL(MLR) = 436 +/- 210 cm H(2)O/l) exhibited wide intra- and intersubject variability. Regardless of computation method, RL was found to decrease as a function of weight, age, respiratory rate (RR), and tidal volume (VT) whereas it increased as a function of RR. VT and inspiratory-to-expiratory time ratio (TI/TE). EL decreased with increasing weight, age, VT and female gender and increased as RR and TI/TE increased. We conclude that accounting for the effects of breathing pattern variability and demographic parameters on estimates of RL and EL is essential if they are to be of clinical value. Multivariate statistical models of RL and EL may facilitate the interpretation of lung mechanics measurements in spontaneously breathing infants.

Developmental changes in chest wall compliance in infancy and early childhood.

Development of chest wall stiffness between infancy and adulthood has important consequences for respiratory system function. To test the hypothesis that there is substantial stiffening of the chest wall in the first few years of life, we measured passive chest wall compliance (Cw) in 40 sedated humans 2 wk-3.5 yr old. Respiratory muscles were relaxed with manual ventilation applied during the Mead-Whittenberger technique. Respiratory system compliance (Crs) and lung compliance (Cl) were calculated from airway opening pressure, transpulmonary pressure, and tidal volume. Cw was calculated as 1/Cw = 1/Crs - 1/Cl during manual ventilation. Mean Cw per kilogram in infants < 1 yr old was significantly higher than that in children > 1 yr old (2.80 +/- 0.87 vs. 2.04 +/- 0.51 ml.cmH2O-1.kg-1; P = 0.002). There was an inverse linear relationship between age and mean Cw per kilogram (r = -0.495, slope -0.037; P < 0.001). In subjects with normal Cl during spontaneous breathing, Cw/spontaneous Cl was 2.86 +/- 1.06 in infants < 1 yr old and 1.33 +/- 0.36 in older children (P = 0.005). We conclude that in infancy the chest wall is nearly three times as compliant as the lung and that by the 2nd year of life chest wall stiffness increases to the point that the chest wall and lung are nearly equally compliant, as in adulthood. Stiffening of the chest wall may play a major role in developmental changes in respiratory system function such as the ability to passively maintain resting lung volume and improved ventilatory efficiency afforded by reduced rib cage distortion.

Alzheimer's care and service utilization: generating practice concepts from empirical findings and narratives.

Despite evidence of stress and strain, many of those who take care of relatives with Alzheimer's disease seem to resist using support services. Existing studies of the use of formal care by families of Alzheimer's sufferers are reviewed with special attention to findings relevant to access, particularly perceptions of appropriateness and acceptability or consistency with other needs and values. The conceptual model represented by these findings is then applied to a narrative that serves as a proxy for a real case that might confront a social worker. Viewed together, both the review of empirical findings and the narrative suggest that theoretical frameworks that take into account meanings attached to relationships and personal moral assessments of whether the duties of caregiving can or should be entrusted to others may offer promising alternatives to traditional psychological or psychoeconomic views of supportive service utilization.

The micropolitics of elder care in Memento Mori, Diary of a Good Neighbor, and A Taste for Death.

Using three novels--Muriel Spark's Memento Mori, Doris Lessing's Diary of a Good Neighbor, and P. D. James' A Taste for Death--we examine themes relating to the social construction of caregiving. In our reading of the stories we found numerous instances of the political in the personal, and of how care can be shaped by inequalities of class and gender, by organizational practices and attitudes rooted in cultural assumptions, and by the social idealization of care provided by relatives and friends.

Paid to care for their own: a report on a community care program that permits relatives to be hired as caregivers.

The feasibility of a state policy to permit home care agencies to hire kin as caregivers was explored by examining existing data on a state program that allowed relatives to be hired. Of 444 clients, 22% had kin as paid caregivers. Co-residence and kinship were associated with higher disability levels and a higher level of eligibility for services as determined by a functional assessment tool used by the state to determine care plans. The limited number of clients with paid caregivers who were kin suggests that there may be a natural limit to the demand for such an option.