RESUMEN
The body density (BD), and hence the relative body fat (% BF) was measured for 182 female athletes. The residual volume (RV) was determined both before and after the underwater weighing by a multiple breath helium dilution technique with the subject immersed to neck level. The absolute mean difference (lXdl) and SEE between the two RV trials were 63 and 75 ml, respectively. These increased to values ranging 144-685 and 187-252 ml, respectively, when the mean of the two RV trials for each subject was compared with the RVs predicted via regression equations, estimated from the vital capacity (VC) and assumed to be a constant of 1000 ml. A similar trend resulted from variation of only the RV in the BD formula for each subject. The two RV trials resulted in an lXdl and SEE of .00121 (.5% BF) and .00141 g.cm-3 (.6% BF), respectively, but these increased to values ranging .00283 (1.3% BF) -.01291 (5.7% BF) and .00362 (1.6% BF) -.00527 g.cm-3 (2.5% BF), respectively, for predicted, estimated and assumed constant RVs. In all cases, the lowest lXdl and SEE were associated with the RVs predicted by a multiple regression equation (R = .725; SEE = 187 ml) which was generated on our sample while the largest lXdl values were registered by the other regression equations. These data emphasize that the use of predicted, estimated and constant RVs result in substantial errors in BD and % BF compared with those when the RV is measured.
Asunto(s)
Tejido Adiposo/anatomía & histología , Peso Corporal , Mediciones del Volumen Pulmonar/métodos , Volumen Residual/métodos , Deportes , Adolescente , Adulto , Niño , Densitometría , Femenino , Humanos , Inmersión , Valor Predictivo de las Pruebas , Análisis de Regresión , Capacidad VitalRESUMEN
The effects of measured and predicted residual lung volume on the accuracy of body density and percent fat (%Fat) were investigated. Adult fitness subjects (N = 46) had residual lung volume measured with the oxygen dilution method while those from an athlete sample (N = 134) utilized the nitrogen washout technique. Residual lung volume was also predicted with gender-specific regression equations using height and age and from 24% of vital capacity (%FVC). Residual lung volume alpha reliability for the average of four residual lung volume trials exceeded 0.90 (SEM less than = 161 ml) for the oxygen dilution method and 0.99 (SEM = 30 ml) for the average of two nitrogen washout measures. The standard errors for predicted residual lung volume were 579 and 355 ml, respectively, for the men and women in the adult sample and 288 ml for the trained athlete sample. Estimating residual lung volume from %FVC yielded a SEE of 318 ml for the trained athlete sample. Measured residual lung volume errors resulted in errors of 1.04%Fat, 0.87%Fat, and 0.21%Fat for the men, women, and trained athlete samples, respectively. In contrast, predicted residual lung volume measurement errors resulted in errors of 3.70%Fat, 2.85%Fat, and 1.98%Fat for the respective samples and 2.18%Fat when using %FVC with the trained athletes. Measured residual lung volume introduces little %Fat error while predicted residual lung volume introduces a substantial source of measurement error.
Asunto(s)
Composición Corporal , Mediciones del Volumen Pulmonar/métodos , Volumen Residual/métodos , Tejido Adiposo/anatomía & histología , Adulto , Femenino , Humanos , MasculinoRESUMEN
Atelectasis, pulmonary edema, fibrosis, pneumothorax, and mucous plug airway obstruction all result in reduced lung volume. The oxygen (O2) wash-in method provides a way to monitor routinely the functional residual capacity (FRC) in the ICU without disconnecting the patient from the ventilator and without additional personnel or instrumentation. This method is a modification of an open-circuit nitrogen (N2) wash-out procedure and requires a computer-based respiratory monitoring system with a fast response O2 analyzer and respiratory flowmeter. FRC is computed after a 20% or greater change in the ventilator FIO2 setting. The accuracy and reproducibility of the method were evaluated using artificial lungs, normal subjects, and postcardiac surgery patients. FRC estimates by O2 wash-in and helium dilution were highly correlated, with r = 0.97 and a regression slope and zero intercept of 1.06 and -0.13, respectively. The FRC difference between 23 repeated trials in 18 postcardiac surgery patients was 70 +/- 160 ml (mean +/- SD).
Asunto(s)
Mediciones del Volumen Pulmonar/métodos , Volumen Residual/métodos , Respiración Artificial , Procedimientos Quirúrgicos Cardíacos , Computadores , Cuidados Críticos , Helio , Humanos , Oxígeno , PosturaRESUMEN
A convenient modification of the classical closed circuit helium dilution technique was developped to determine functional residual capacity, especially in intubated and artificial ventilated patients. The determination of the still inflatable lung volume and its variability in the course of pulmonary insufficiency or after a change in the adjustment of the respirator (PEEP a.o.), was reproducible better than +/- 10%. This method can be performed in a short time, without risk for the patient and with instruments locally independent of the ICU, surgery or recovery room.
Asunto(s)
Helio , Mediciones del Volumen Pulmonar/métodos , Volumen Residual/métodos , Síndrome de Dificultad Respiratoria/diagnóstico , Dióxido de Carbono/metabolismo , Humanos , Respiración ArtificialRESUMEN
This paper describes a modification of the standard oxygen-dilution technique for determining residual lung volume, whereby rapid responding oxygen and carbon dioxide analyzers are used to determine the point of nitrogen equilibration, and a five-liter rebreathing bag is substituted for the standard spirometer. This simplified method reduced the total test time to five min or less for duplicate determinations, and eliminated the need for a nitrogen analyzer and a spirometer. This method was found to be both reliable (r = 0.99) and valid (r = 0.92), with a standard error of prediction of 125 ml, and a mean difference of only eight ml, when compared with the established oxygen-dilution technique on a sample of 76 healthy men and women, 19 to 55 years of age. In a subsample of 13 subjects, residual volume was also determined with the nitrogen washout technique, which correlated r = 0.89 and r = 0.91 with the established and modified oxygen-dilution techniques respectively. The use of assumed values for the initial and final alveolar concentrations of nitrogen did not appear to significantly influence the final results.
Asunto(s)
Mediciones del Volumen Pulmonar/métodos , Adulto , Dióxido de Carbono , Femenino , Humanos , Masculino , Nitrógeno , Oxígeno , Volumen Residual/métodosAsunto(s)
Mediciones del Volumen Pulmonar , Pulmón/fisiología , Volumen Residual , Adolescente , Adulto , Factores de Edad , Anciano , Niño , Femenino , Humanos , Pulmón/diagnóstico por imagen , Mediciones del Volumen Pulmonar/instrumentación , Mediciones del Volumen Pulmonar/métodos , Masculino , Persona de Mediana Edad , Pletismografía Total , Radiografía , Valores de Referencia , Volumen Residual/instrumentación , Volumen Residual/métodos , Factores Sexuales , EspirometríaRESUMEN
The functional residual capacity (FRC) was measured in 24 healthy subjects, 1-by the helium dilution method using a closed system and an open system during washout, and 2-using a constant pressure plethysmograph. Results obtained with the three methods were not significantly different. Furthermore, FRC was determined by helium dilution in 177 healthy men and in 100 healthy women, aged between 18 and 77 years. In both sexes, FRC was dependent on age, height (H) and weight, being greater in the taller, older subjects. For a given height and age, FRC decreased with increasing weight. Correlation coefficients between logarithm of (FRC/H3) and age and/or weight were highly significant. From these allometric relationships, it was possible to calculate FRC reference values, and then, reference values for other functional tests such as steady state TLCO and lung compliance.
Asunto(s)
Mediciones del Volumen Pulmonar/métodos , Pulmón/fisiología , Volumen Residual/métodos , Adolescente , Adulto , Anciano , Estatura , Peso Corporal , Femenino , Humanos , Masculino , Persona de Mediana EdadRESUMEN
A radioactive xenon inhalation procedure was used to determine differential residual volumes (right lung vs. left lung) in 28 normal subjects (6 of whom smoked approximately 1 package of cigarettes per day). The average right lung residual volume represented 54% of the total residual volume, whereas the average left lung residual volumerepresented 46% of the total. In addition, all of the subjects were studied by a standard helium dilution technique and found to have total lung residual comparable to the total lung residual volume as determined by the xenon technique. There was no statistical difference between the data obtained from cigarette smokers vs. nonsmokers. The noninvasive nature of the xenon technique makes this a useful procedure in determining differential residual volumes.
Asunto(s)
Mediciones del Volumen Pulmonar/métodos , Volumen Residual/métodos , Espirometría/métodos , Radioisótopos de Xenón , Adolescente , Adulto , Femenino , Lateralidad Funcional , Helio , Humanos , Técnicas de Dilución del Indicador , Masculino , Fumar/fisiopatología , Radioisótopos de Xenón/administración & dosificaciónRESUMEN
After a critical study of classic lung models, showing that linear resistances are not faithful nor justified and that pneumotachograph is not a good measuring apparatus because of its inaccuracy (it changes calibration according to the nature of gas mixture and needs integration to determine volumes), authors present their own lung "model". In this model, it is possible to adjust resistance, compliance, vital capacity and residual volume. Parabolic resistances are used, because they more approach physiologic ones. Building of resistances (diaphragms), compliances (rigid tanks with adjustable elements), vital capacity (elastic membrane between two grills) is simple to realise and easy to reproduce. Measures of pressure and volume are given directly by gauges and are insensitive to gas nature, which is important in respiratory physiology. Flow-rates are deducted from volume values. The lung model can be used in a twin-cell shape to show the effects of artificial ventilation in case of pulmonary asymmetry. Examples given underline the interest of having a model with resistances easy to build and an adjustable vital capacity.
Asunto(s)
Pulmón/fisiología , Modelos Biológicos , Ventiladores Mecánicos/normas , Resistencia de las Vías Respiratorias/métodos , Humanos , Rendimiento Pulmonar/métodos , Volumen Residual/métodos , Capacidad Vital/métodosRESUMEN
The helium dilution technique for the measurement of functional residual capacity (FRC) is reviewed with special reference to anaesthesia. A modification is described which permits measurements to be made during intermittent positive pressure ventilation. This modification causes minimal interference with the circuit as it is used for spontaneous respiration. The measuring circuit may be alternated with an open circuit without disturbance of the pattern of breathing (spontaneous or artificial). Potential errors in the measurement of FRC during anaesthesia are considered and assessment of linearity, reproducibility and accuracy is described.