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At least 757 records · Page 42Linked to original sources
PubMed1996

Measurement of lung function in awake 2-4-year-old asthmatic children during methacholine challenge and acute asthma: a comparison of the impulse oscillation technique, the interrupter technique, and transcutaneous measurement of oxygen versus whole-body plethysmography.

This study evaluated three techniques for testing of lung function in young awake children. We compared measurements by the forced or impulse oscillation technique (IOS), the interrupter technique (IT), and transcutaneous measurements of oxygen (tcPo2) with concomitant measurements of specific airway resistance (sRaw) during methacholine challenge in 20 stable asthmatic children, 2-4 years old. Measurements were performed with all techniques after each dose of methacholine and after inhalation of a bronchodilator. Measurements were carried out during tidal breathing using a face-mask with a built-in mouthpiece. The ranking of sensitivity was as follows: sRaw > IOS, respiratory reactance at 5 Hz (Xrs5) > tcPo2 > interrupter resistance (Rint) > IOS, respiratory resistance at 5 Hz (Rrs5). The sensitivity of sRaw and Xrs5 was not significantly different, but both were significantly more sensitive than Rint and Rrs5; the sensitivity of tcPo2, Rint, and Rrs5 was not significantly different. Measurements in eight of the subjects performed during an episode of acute asthma yielded comparable results in regard to the sensitivity of the techniques. Measurements improved significantly after bronchodilator administration; however, the response to bronchodilator tended to be less during acute asthma and was best demonstrated by a deterioration of tcPo2. All the evaluated techniques reliably reflect short-term changes in respiratory function and can provide clinically useful estimates of airway function. The techniques are non-invasive, are not dependent on the active co-operation or sedation of the subjects, and therefore are well suited for routine use in young children.

Acute Disease↗
PubMed1983

The assessment of calf pump function by isotope plethysmography.

A method of measuring the function of the calf muscle pump using in vivo 99Tcm-labelled red cells is described. This new, non-invasive method can provide detailed information about the emptying and refilling of the deep and superficial veins of the calf which may prove to be superior to those methods of assessment currently used in the selection and follow-up of patients for venous surgery.

Erythrocytes↗
PubMedDate not supplied

Flow-pressure looping during plethysmography in wheezy infants.

Marked looping of the expiratory portion of the flow-pressure relationship was noted in some infants during measurements of airway resistance in a whole-body plethysmograph while the respired air was maintained at body temperature and humidity. An investigation of 13 infants who had varying degrees of airway obstruction showed that there was a negative correlation (r = 0.72) between the severity of the looping and specific airway conductance (SGaw). An even stronger correlation (r = 0.85) was found between the tangent of the angle of phase lag between flow and pressure (theta) and the forced expiratory time constant (t) obtained from the partial forced expiratory flow-volume curve. Such a relationship would be predicted from a model in which the lung behaved as a simple electrical resistance-capacitance network during expiration. It is suggested that the looping is the result of small airway closure during expiration in wheezy infants, with a consequent rise in resistance and prolongation of the time constant of the lung.

Airway Resistance↗
PubMed1995

A critical assessment of uncalibrated respiratory inductance plethysmography (Respitrace) for the measurement of tidal breathing parameters in newborns and infants.

We have compared results obtained with an uncalibrated respiratory inductance plethysmograph (RIP) with those of a face mask and pneumotachograph (PNT) for the computerized measurement of the time to reach peak tidal expiratory flow as a ratio of total expiratory time (tPTEF:tE). Simultaneous measurements were made in 32 healthy neonates aged 0-3 weeks, 35 healthy infants aged 5-82 weeks, and 28 infants aged 15-94 weeks with physician diagnosed recurrent wheeze. The group mean (+/- SD) values of tPTEF:TE determined using a PNT were 0.455 (+/- 0.129), 0.263 (+/- 0.077), and 0.232 (+/- 0.089) for the neonates, healthy infants and infants with recurrent wheeze respectively. RIP gave mean (+/- SD) values that were 0.055 (+/- 0.044) and 0.025 (+/- 0.104) lower than the PNT in healthy neonates and infants with recurrent wheeze respectively; RIP values were 0.002 (+/- 0.073) higher in the healthy infants over 4 weeks of age than measurements by PNT. Although the difference between the two measurements was not related to the thoracoabdominal phase angle, as measured from Lissajous figures, examination of the RIP ribcage and abdominal signals revealed that many healthy subjects, while appearing clinically in phase, had ribcage and abdominal signals that differed markedly from each other in terms of convexity/concavity during early expiration. This may explain the lack of agreement between the two methods. We conclude that uncalibrated RIP should be used with caution for the determination of tPTEF:tE, even in subjects whose ribcage and abdomen appear to move synchronously. The measurement of tPTEF:tE did not differentiate between the healthy infants and infants with recurrent wheezing.

Data Interpretation, Statistical↗