Biomedical subjects

A De Groote

Publications and source records attributed to A De Groote.

3 recordsLinked to original sources

PubMed2001

Mathematical assessment of qualitative diagnostic calibration for respiratory inductive plethysmography.

We present a critical assessment of qualitative diagnostic calibration (QDC), which claims to provide a relative calibration of respiratory inductive plethysmography during natural breathing (Sackner MA, Watson H, Belsito AS, Feinerman D, Suarez M, Gonzalez G, Bizousky F, and Krieger B. J Appl Physiol 66: 410-420, 1989). QDC computes the calibration factor (K) by considering breaths of constant tidal volume (VT) and provides a criterion to select breaths when VT is unknown. We applied QDC on uncalibrated data constructed from simulated sets of thoracic and abdominal volumes, with a predefined K. As expected, QDC yields a correct K when applied to breaths at constant VT. In breathing at quasi-constant VT, the criterion for breath selection is shown to bias the results toward K = 1. For spontaneous breathing, the calculated K deviates from its predefined value and depends heavily on the selection criterion. We conclude that QDC will only provide a correct calibration factor when applied to an entire set of breaths with constant or quasi-constant VT. More generally, physiological conclusions based on QDC should be critically evaluated on a case-by-case basis.

Abdomen↗

PubMed2000

Naso-oesophageal probes decrease the frequency of sleep apnoeas in infants.

The objective of the study was to determine whether a naso-oesophageal probe modifies sleep and cardiorespiratory patterns in infants with repeated obstructive apnoeas. Two polygraphic recording sessions were conducted in random order for 2 nights on 35 infants suspected to have repeated obstructive sleep apnoeas. One sleep study was performed with a pH probe inserted through the nasal passage down to the distal portion of the oesophagus. The other session was conducted without any naso-oesophageal probe (the baseline study). For the 25 infants who presented repeated obstructive apnoeas during baseline studies, the presence of the probe was associated with a small, but significant, decrease in the number of central apnoeas (median frequency of 18.5 apnoeas per hour without a probe; 16.1 per hour with the probe; P=0.040), and obstructive apnoeas (median of 1.9 apnoeas per hour without a probe; 0.6 per hour with the probe; P=0.016). The presence of the probe was also associated with a small increase in percentage non-rapid eye movement (NREM) sleep frequency. The changes were statistically significant only for infants who had no obstructive apnoea during baseline studies (29 vs. 31%). The presence of a naso-oesophageal probe significantly modifies the infants' respiratory characteristics during sleep. These findings should be considered when reporting and interpreting sleep studies in infants.

Airway Obstruction↗

PubMed1997

Chest wall motion during tidal breathing.

We have used an automatic motion analyzer, the ELITE system, to study changes in chest wall configuration during resting breathing in five normal, seated subjects. Two television cameras were used to record the x-y-z displacements of 36 markers positioned circumferentially at the level of the third (S1) and fifth (S2) costal cartilage, corresponding to the lung-apposed rib cage; midway between the xyphoid process and the costal margin (S3), corresponding to the abdomen-apposed rib cage; and at the level of the umbilicus (S4). Recordings of different subsets of markers were made by submitting the subject to five successive rotations of 45-90 degrees. Each recording lasted 30 s, and three-dimensional displacements of markers were analyzed with the Matlab software. At spontaneous end expiration, sections S1-3 were elliptical but S4 was more circular. Tidal changes in chest wall dimensions were consistent among subjects. For S1-2, changes during inspiration occurred primarily in the cranial and ventral directions and averaged 3-5 mm; displacements in the lateral direction were smaller (1-2 mm). On the other hand, changes at the level of S4 occurred almost exclusively in the ventral direction. In addition, both compartments showed a ventral displacement of their dorsal aspect that was not accounted for by flexion of the spine. We conclude that, in normal subjects breathing at rest in the seated posture, displacements of the rib cage during inspiration are in the cranial, lateral outward, and ventral directions but that expansion of the abdomen is confined to the ventral direction.

Adult↗