Biomedical subjects

L C Lands

Publications and source records attributed to L C Lands.

40 records · Page 3Linked to original sources

PubMed1992

Cardiac output determination during progressive exercise in cystic fibrosis.

Cardiac output (Q) determination using the equilibrium CO2-rebreathe indirect Fick technique (Equil) to estimate mixed venous PCO2 (Pv-CO2) has been validated during steady state (SS) exercise in subjects with lung disease. A modification of the exponential method using a low concentration of CO2 with an exponential rise in PEt-CO2 (Ex) during rebreathing to estimate Pv-CO2 has been validated during nonsteady state exercise. The purpose of the present study was to validate the Ex method in subjects with lung disease. Q was measured by Ex at every second work load during Prog. Q was measured after 5 min of SS exercise by both Ex and Equil. Arterial PCO2 was estimated from PEtCO2. There was no significant difference in the Q-VO2 relationship during Prog exercise between the combined control and mild (FEV1 > 70%) CF subjects or the moderate and severe CF subjects. Q can be determined in the nonsteady state using the exponential CO2-rebreathe indirect Fick technique in subjects with CF, allowing for noninvasive examination of cardiopulmonary interaction during exercise at a wide range of work loads.

Adult↗

PubMed1991

The effects of diuresis and transfusion on pulmonary function in children with thalassemia major.

Previous pulmonary function studies in subjects with thalassemia major (TM) who were on regular transfusion programs have demonstrated results ranging from small airway obstruction to a restrictive pattern. Ten subjects with TM were studied pre- and postdiuresis, and again 24 hr after transfusion, in order to evaluate the role of possible fluid overload in altering pulmonary function. Subjects underwent spirometry and had lung volume and flow volume curves (MEFVC) measured in a volume displacement plethysmograph while breathing air and a mixture of 80% helium and 20% oxygen (HeO2). Six patients had pulmonary mechanics measured with esophageal balloons in place. Baseline function was normal and no change occurred following diuresis. Following transfusion, the volume of isoflow (VisoV) decreased, but other parameters did not change. Subsequent analysis revealed 5 subjects with an initial VisoV greater than 20 (% FVC) but, paradoxically, less evidence of flow limitation in the small airways than those with a VisoV less than 20 (% FVC). Posttransfusion, in those subjects with an initially high VisoV, the Vmax25(air) tended to fall without a change of MEFVC in HeO2, resulting in a decreased VisoV. This was interpreted as evidence of subtle abnormalities in the small airways caused by volume expansion, raising doubts about the value of the VisoV as a measure of small airway disease. As a group, our subjects did not demonstrate any abnormalities in baseline function. Some subjects had mild flow limitation in small airway while other developed comparable levels of flow limitation following the volume expansion associated with transfusion.

Blood Transfusion↗

PubMed1991

Accuracy of measurements of small changes in soft tissue mass by use of dual-photon absorptiometry.

Dual-photon absorptiometry (DPA) has recently been applied to the assessment of body composition. To evaluate the accuracy of DPA in detecting small changes in the lean soft tissue mass, we performed DPA with the use of the Norland 2600 Dichromatic densitometer on six healthy adult males before and after a 30-ml/kg transfusion of saline and before and after exercise in a warm environment, resulting in a greater than or equal to 1-kg weight loss. Absolute weight [baseline pretransfusion r2 = 0.999, standard error of estimate (SEE) = 590 g; posttransfusion r2 = 0.999, SEE = 300 g; baseline pretranspiration r2 = 0.999, SEE = 230 g; posttranspiration r2 = 0.999, SEE = 240 g] was accurately reflected in DPA total mass. Weight changes due to transfusion were poorly reflected by changes in DPA total mass (r2 = 0.417, SEE = 404 g). However, changes posttranspiration were accurately reflected in the DPA total mass (r2 = 0.886, SEE = 106 g posttranspiration). Similarly, weight changes due to transfusion were poorly measured by changes in DPA soft mass (r2 = 0.478, SEE = 365 g), but changes posttranspiration were highly correlated with DPA soft mass changes (r2 = 0.909, SEE = 92 g). Weight changes were not reflected by changes in the DPA lean soft tissue mass (r2 = 0.006, SEE = 1,737 posttransfusion, r2 = 0.094, SEE = 1,038 g posttranspiration). DPA-derived nonfat mass was highly correlated with skinfold-derived nonfat mass (r2 = 0.96, SEE = 2,400 g). Accuracy of total and soft tissue measurements implied correct mineral mass assessment.(ABSTRACT TRUNCATED AT 250 WORDS)

Absorptiometry, Photon↗

PubMedDate not supplied

Activity levels and the relationship to lung function and nutritional status in children with cystic fibrosis.

Cystic fibrosis is characterized by chronic obstructive lung disease and malnutrition. Previous studies have shown that nutritional status and lung function are limiting factors for exercise capacity. A reduced exercise capacity may in turn diminish activity levels. We evaluated whether the total time spent somewhat active (e.g., walking) or active (e.g., biking), as reported by the Habitual Activity Estimation Scale, was related to lung function, as evaluated by forced expiratory volume in one second (%predicted FEV1), and nutritional status, measured as body mass percentile, in 36 children with cystic fibrosis, aged 6 to 16 years. The Habitual Activity Estimation Scale questionnaires were completed by the parents for children younger than 12 years of age and by both the parent and the child, independently, for those 12 years and older. Patients had a body mass percentile of 99 +/- 15.2% and % predicted FEV1 of 85.7 +/- 20, with no differences between boys (15/36) and girls (21/36). Boys spent 8.1 hours and girls spent 7.5 hours (P > 0.1) being at least somewhat active. These values are similar to those reported for healthy boys and girls. In patients with significant lung disease (%predicted FEV1, < or = 75; n = 11), activity level (the time spent somewhat active or active) was related to nutritional status (r = 0.675; P = 0.02) but not to lung function (r = 0.21; P > 0.1). Activity level reported by patients 12 years of age and older was on average 24.1% higher (P < 0.05) than that reported by their parents, but the two reportings were related (r = 0.758; P = 0.004). These results suggest that activity level may be restricted by nutritional status in those patients with significant air flow limitation. We suggest that improving the nutritional status of cystic fibrosis patients may prevent decreases in activity levels and quality of life of these affected children.

Adolescent↗