Comparison of thoracoabdominal calibration methods in normal human subjects

Abstract

In 19 normal subjects in the supine posture, we compared accuracy and precision of calibration methods that utilized different ranges of tidal volumes and thoracoabdominal partitioning: spontaneous quiet breathing (QB), isovolume maneuvers, and voluntary efforts to breathe with variable tidal volume and thoracoabdominal partitioning. Thoracic and abdominal movements were measured with the respiratory area fluxometer. Calibration methods utilizing one or more types of respiratory efforts were applied to three measurement situations: QB, variable breathing (volume and thoracoabdominal partitioning), and simulated obstructive apnea (isovolume efforts). Qualitative diagnostic calibration (QDC) included QB data only. The isovolume method (ISOCAL) included isovolumetric efforts at end expiration (functional residual capacity) and QB. Multilinear regression analyses were performed on data sets that included 1) voluntary efforts to breathe with variable volume and thoracoabdominal partitioning (CAL 1), 2) QB in addition to variable volume and partitioning (CAL 2), and 3) isovolume maneuvers in addition to QB and variable volume and partitioning efforts (CAL 3). When calibration data included a wide range of tidal volume, variable thoracoabdominal partitioning, and isovolume efforts (CAL 3), a stable calibration with small bias and scatter during all respiratory patterns was obtained. Excluding isovolume maneuvers (CAL 2) and QB (CAL 1) did not diminish accuracy. Limiting data to isovolume efforts at functional residual capacity plus QB (ISO-CAL) caused a significant increase in scatter during variable breathing patterns. Limiting calibration data to that portion of QB with small variation in the uncalibrated sum of thoracic and abdominal movements (QDC) caused significant increases in scatter in both isovolume efforts and variable breathing.

Validation of respiratory inductive plethysmography using the Qualitative Diagnostic Calibration method in anaesthetized infants

“…Unfortunately, the RespiEvents™ software does not allow the user to access the exclusion criteria, or assess the intrinsic variability of the RIP signals during the calibration period. This made it impossible to assess whether the relative contribution of the rc and abd compartments to VT was sufficiently variable during the 5 min of QDC calibration to derive robust coefficients in these anaesthetised infants [12]. The QDC method also assumes that the respiratory system can be represented by a single compartment model, with instantaneous pressure equilibration throughout the system, which may prove to be a significant limitation in infants.…”

“…In an attempt to overcome this problem, various modifications of the isovolume technique have been proposed for use in infants and children, including the use of different patterns of ventilation, due to changes in body posture, sleep state or airway occlusion, to derive the relative contribution of the rc and abd to the tidal volume and thereby assign appropriate calibration coefficients [4,5,[10][11][12][13]. Nevertheless, these methods generally remain too complex for widespread use.…”

“…Validation of the QDC method has been performed in both awake adults [14], and in sleeping newborns and infants [15,16], but not in anaesthetized subjects, in whom the contribution of the rc and abd compartments during tidal breathing may not be sufficiently variable to allow derivation of accurate calibration factors using QDC [12]. In addition, there is very little information about how many breaths need to be derived from RIP to reflect VT measured simultaneously from a PNT accurately.…”

Pletismografia respiratória por indutância: estudo comparativo entre calibração por manobra de isovolume e calibração qualitativa diagnóstica em voluntários saudáveis avaliados em diferentes posturas

“…In this sense, a study conducted by Sartene et al (7) demonstrated that, during quiet breathing, there is dispersion of approximately 20% of the mean tidal volume, and only 8% of this value corresponds to the contribution of the thoracic and abdominal compartments. Therefore, the authors stated that the use of calibrations requiring quiet breathing is questionable when quiet breathing is employed in devices with two degrees of freedom, given that most of the study participants, when evaluated in the supine position, predominantly used only one degree of freedom.…”

“…(2)(3)(4)(5)(6)(7) The QDC method is performed during a given period of baseline breathing and uses a statistical placed horizontally on a stretcher, lying on their backs, with the hips and knees flexed; for the sitting position, the volunteers were sat on a chair without back support, with the hips and knees at a 90° angle; and for the orthostatic position, the volunteers were instructed to stand upright, with arms relaxed at their sides, and distribute their body weight evenly on both legs (Figure 1).…”