Variabilidad del patrón respiratorio durante la carga elástica inspiratoria / Variability of breathing pattern during inspiratory elastic load

La ventilación pulmonar en humanos tiene una variabilidad respiración a respiración no lineal, compleja y caótica. El objetivo del trabajo fue: caracterizar la variabilidad del patrón respiratorio en perros (n: 8) anestesiados respirando bajo carga elástica umbral (CEU) inspiratoria (7 a 50 cm H2O). Con el flujo, presión traqueal y esofágica, se analizaron: tiempo inspiratorio (Ti), ritmo [tiempo espiratorio (Te); tiempo total (Ttot), y Ti/Ttot] e impulso central (Vt/Ti), variables relacionadas [volumen corriente (Vt) y ventilación pulmonar (Ve)]. Se determinaron: variabilidad grosera (varianzas), oscilaciones de baja frecuencia (análisis espectral) y memoria a corto plazo (análisis de autocorrelación). La CEU produjo disminución de la varianza de medias en Te, Ttot, Vt y Vt/Ti (p < 0.05). La media de las varianzas del Ti/Ttot aumentó (p < 0.005) y disminuyó para el Vt y el Vt/Ti (p < 0.05). En general, el porcentaje de oscilaciones de baja frecuencia (OB%) disminuyó (p < 0.02). Durante CEU alta, las variables de ritmo no cambiaron el porcentaje de registros con autocorrelación (AU%), pero el Vt y variables relacionadas disminuyeron los AU% (p < 0.005). Hubo correlación positiva (r: 0.955, p< 0.001) entre OB% y AU% en Vt y variables relacionadas, pero las variables de ritmo no mostraron correlación. En conclusión: La CEU indujo un patrón respiratorio más monótono. La memoria a corto plazo disminuyó en la fase inspiratoria y aumentó en la espiratoria. Estos cambios ocurrieron bajo anestesia, sugiriendo que ciertas estructuras suprapontinas pueden no ser imprescindibles para la generación de estos cambios.

In humans, lung ventilation exhibits breath-to-breath variability and dynamics that are nonlinear, complex and chaotic. Our objective was to characterize the breathing pattern variational activity in anesthetized dogs (n: 8) breathing through threshold inspiratory elastic load (7 to 50 cm H2O). Starting from flow signal and tracheal and esophageal pressures, we analyzed inspiratory time (Ti), timing (expiratory time, Te; total time, Ttot; and Ti/Ttot) and central drive (Vt/Ti) and variables related to it (tidal volume, Vt and pulmonary ventilation, Ve). We measured gross variability (variances), low frequency oscillations (spectral analysis), and short term memory (autocorrelation analysis). Loading decreased variance of the mean values of Te, Ttot, Vt and Vt/Ti (p < 0.05); the mean of variances for Ti/Ttot increased (p < 0.005) while it decreased for Vt and Vt/Ti (p < 0.05). In general, percent of data recordings with low frequency oscillations (OB%) decreased (p < 0.02). During heavy load, timing parameters percent of data recordings with autocorrelations (AU%) did not change, but Vt and its related parameters decreased their AU% (p < 0.005). There was a positive correlation (r: 0.955, p < 0.001) between the existence of low frequency oscillations and autocorrelations for Vt and its related parameters, while timing variables did not show such a correlation. In conclusion, threshold elastic load induced a monotonous respiratory pattern. The short term memory decreased during inspiratory stage while increased during expiratory stage. These changes occurred during anesthesia suggesting that certain suprapontine structures may not be obligatory to induce them.

Análisis del signo de Hoover en relación con parametros funcionales, radiologicos y de radio de curvatura en pacientes con enfermedad pulmonar obstructiva crónica / [Relationship between Hoover sign, functional and variables, and curvature radius in patients with obstructive pulmonary disease]

The purpose of the present study was: 1) to relate the Hoover sign -SH (+)- with several functional (spirometry and lung volumes) and radiographic (AP x-ray) parameters, 2) to characterize the changes in diaphragmatic curvature radius and the efficiency and to establish some relationships with the functional and radiographic parameters. Fifteen patients with COPD (SH (+), n: 8) were studied. The radius was determined in the right hemidiaphragm after maximal inspired and expired x-ray. The SH (+) was found in more severely obstructed patients (FEV1

) and with high degree of air trapping (RV/TLC

, p 0.01). The expiratory radius (Re) was higher (p 0.05), and their efficiency (1/Re), was minor (p 0.05). The FEV1

correlated with the degree of hyperinflation according to TLC

(r -0.58, p 0.022) and with air trapping according to RV

(r -0.77, p 0.0008). The patients with low FEV1

showed high Re (r -0.61, p 0.015) and decreased diaphragmatic efficiency during expiration (1/Re) according to 1/Re = 0.093 cm-1 + 0.0012 cm-1* FEV1

(r 0.688, p 0.0054). The FEV1 correlated with the diaphragmatic movement (r 0.71, p 0.003). The PaCO2 correlated with the TLC

(r 0.534, p 0.04), the RV

(r 0.62, p 0.014) and with the radiographic parameters of hyperinflation (r 0.546, p 0.035) and air trapping (r 0.528, p 0.043). The presence of Hoover sign suggest severe bronchial obstruction, diaphragmatic flattening, increase of curvature radius, decrease of mobility and efficiency.