PubMed Health⌕ Search

Biomedical subjects

A C Pincock

Publications and source records attributed to A C Pincock.

14 recordsLinked to original sources
PubMed1990

Upper airway obstruction due to goitre: detection, prevalence and results of surgical management.

A group of 132 women and 12 men with goitre were studied to determine the prevalence of upper airway obstruction caused by the goitre. Inspection of flow-volume loops was used to detect upper airway obstruction and this suggested that 44 subjects (31 per cent) had the condition. Of these 44 subjects 19 per cent were men, which was a greater proportion than could be accounted for by chance. Flow-volume loops after surgery were recorded on 43 patients of whom 29 were from the group thought to have had upper airway obstruction. Comparison of measurements before and after surgery showed no important change in the 14 without, and improvement in 27 of those with, upper airway obstruction. Analysis indicated two failures of treatment and four probable false-positives among the group with upper airway obstruction. Inspection of the flow-volume loop had a 78 per cent specificity and 100 per cent sensitivity in detecting upper airway obstruction whereas an FEV:PEF ratio above 8 had a specificity of 94 per cent and a sensitivity of 64 per cent in this respect. Ultrasonography and plain radiography of the upper airway accurately predicted retrosternal extension of the goitre but did not predict upper airway obstruction. It is recommended that all patients with symptomatic goitre should have a flow volume loop recorded.

Adult↗
PubMed1986

Linearity and temperature control of the Fleisch pneumotachograph.

We have investigated the optimal thermal conditions of a Fleisch no. 4 pneumotachograph (PT) necessary for recording maximal forced expiratory maneuvers (MFEM). Our PT assembly was tested with a computer-driven pump and found to be linear up to 14 l/s. Thermocouples (TC) were placed in a peripheral, mid, and a central capillary of the PT. Stable temperature control and consistent PT calibration were best obtained by proportional thermostatic control via the peripheral TC. When the PT was heated to 35 degrees C or above, expirations from either the pump (air at 33 degrees C saturated) or a subject cooled the PT, thus affecting its response. With the PT heated to 30 degrees C, repeated blows caused little change in PT temperature, with no evidence of condensation, thus indicating optimal thermal conditions for recording MFEM.

Biomedical Engineering↗
PubMed1985

Patterns of spirogram abnormality in individual smokers.

Dynamic ventilatory function was measured in 147 male and 212 female smokers with a mean age of 39.3 and 42.5 yr, respectively. The results were compared with values predicted from the results of control subjects who had never smoked, and deviation from predicted was expressed as a standardized residual (SR). Although the flow indices FMF, FEF50, and FEF75 showed a substantial group change in SR for smokers, the distribution of SR indicated changes in the majority of smokers but did not favor the identification of individual subjects as being abnormal. By contrast, the distribution of SR for FEV1/FVC%, FEV3/FVC%, and the time domain indices alpha(1) 75%, MR90%, and mu favored the identification of subjects with marked abnormalities. These volume-standardized indices allowed the identification of 2 patterns of spirometric abnormality prevalent among smokers. Pattern 1 showed changes predominantly in the first 75% of FVC and Pattern 2 showed changes generally confined to the tail of the spirogram; 15% of the female and 14% of the male smokers had Pattern 1 abnormalities, with only 4% of both the female and male smokers showing Pattern 2. These results appear more consistent with the "Dutch hypothesis" and not the "small airways hypothesis" concerning the development of chronic air-flow limitation in smokers.

Adult↗
PubMed1985

Time domain spirogram indices. Their variability and reference values in nonsmokers.

A cross-sectional population survey of dynamic ventilatory lung function was performed to determine the variability of and reference values for time domain spirogram indices. The reference population comprised 83 men and 143 women who were healthy nonsmokers. The time domain indices were derived from the blow with the largest sum of FVC and FEV1. Prediction equations for FEV1 and mean flow between 25 and 75% FVC were little influenced by methods for selecting the data from the 3 blows recorded. The variability of the first 2 moments of the spirogram increased with age, requiring a log transformation for regression analysis. Prediction equations for conventional and time domain spirometric indices are presented and reference values are proposed based on an estimated percentile derived from the predicted value and the residual standard deviation from regression. Two time domain indices are identified that may prove better suited than conventional indices for identifying abnormalities in the tail of the spirogram.

Adult↗
PubMed1984

Respiratory symptoms and pulmonary function of welders in the engineering industry.

We have studied respiratory symptoms, smoking habits, chest radiographs, sickness absence, and pulmonary function among 258 welders and an equal number of matched control subjects in three engineering factories. Welders who smoked had a higher frequency of chronic phlegm production than control subjects but there was no difference in cough or dyspnoea. The frequency of abnormality on chest radiographs was low and similar in welders and controls. Upper respiratory infections were a more frequent cause of sickness absence in welders than in controls but no difference was found in other respiratory diseases. FEV1 and peak expiratory flow rate were similar in welders and controls. In a subset of 186 subjects the maximum expiratory flow rate at low lung volumes was significantly less in welders who smoked than in control subjects who smoked, but there was no difference in non-smokers. Welders working under these conditions in the engineering industry appear to have no increased risk of chronic obstructive lung disease.

Absenteeism↗
PubMed1983

The effect of temperature on recording spirograms.

Correcting spirometric indexes to BTPS assumes that the spirometer has a short cooling time constant. This assumption was challenged by testing a rolling seal spirometer (RSS), a water seal spirometer (WSS), and a heated pneumotachygraph (PT) with simulated spirograms from a computer-driven servo-controlled pump whose internal temperature could be regulated. When tested with ambient air (19 degrees C) the devices recorded forced expiratory volume in one second (FEV1) (4.0 L) to within 1%. With air at 37 degrees C the precision of the PT was little changed but the RSS and WSS (corrected to BTPS) overestimated FEV1 by 6 and 5%, respectively. The first moment of the spirogram (mean transit time) was 8 and 15% underestimated by the RSS and WSS, respectively, whereas the PT was precise to within 1%. These errors changed with ambient temperature and time constant of the spirogram. Clinical judgments concerning individual patients are unlikely to be seriously influenced by these errors. However, for the precise recording of spirograms required in epidemiologic and research work, and especially for studies on the shape of spirograms and flow-volume curves, these are important errors.

Computers↗
PubMed1982

Repeatability of the moments of the truncated forced expiratory spirogram.

It is proposed that if the spirogram is truncated for moment analysis, this should be done with respect to volume and not time. Errors are incurred when the moments of one spirogram are compared with those of another. These errors are maximal with no truncation and are reduced by truncation. A method is described for deriving sequential truncated moments of the forced expiratory spirogram. The repeatability and discriminatory power of the truncated moments were assessed over five consecutive days in 21 symptom-free subjects and were compared with conventional spirometric tests. The first and second moments about the origin of the spirogram (alpha 1 and alpha 2), the moment ratio (square root alpha 2/alpha 1) and the forced expiratory time to truncation (FET) are progressively less repeatable within individuals the later the truncation point. The discriminatory power of alpha 1 and alpha 2 and FET declines with later truncation but the discriminatory power of the moment ratio is maximal with truncation at 85% forced vital capacity (FVC) an diminishes sharply if truncation is beyond 95% FVC. At 75% FVC truncation alpha 1 is as good as FEV1% in discriminating between our subjects, whereas alpha 1 at 100% FVC is only half as good as FEV1%. The moment ratio at 90% FVC truncation is highly reproducible (mean within person coefficient of variation 2.1%), has important discriminatory power and is little influenced by events early in the spirogram (correlation with FEV1% r = -0.61, p less than 0.001). The moment ratio at 90% of FVC has attributes which may be useful in detecting early airway obstruction and its further study is warranted in order to establish its normal range and predictive value.

Adult↗