PubMed · 8207184
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J T Lee. 1994. Statistical process control charts.. https://pubmed.ncbi.nlm.nih.gov/8207184/
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Nocturnal desaturations during rapid eye movement (REM) sleep, caused by nonobstructive hypoventilation, occur frequently in patients with chronic obstructive pulmonary disease (COPD). This is partly caused by decreased activity of the intercostal and accessory muscles due to a lower motor command. The diaphragm has to compensate for the diminished activity of these muscles during REM sleep. However, in patients with COPD strength and endurance of the diaphragm may be affected by its unfavorable position on the length-tension curve because of hyperinflation. The aim of this study was to establish the causal relationship between respiratory muscle function and nocturnal saturation in patients with COPD. We hypothesized that target-flow inspiratory muscle training (TF-IMT) would improve nocturnal saturation. In 20 patients with stable COPD (FEV1 35.5 +/- 14.1% of predicted) and a mean nocturnal saturation below 92% we measured maximal inspiratory pressure (PImax), transdiaphragmatic pressure (Pdi), maximal sustainable inspiratory pressure (SIPmax), endurance time, and nocturnal saturation in Weeks 0, 4, and 10. During these 10 wk 10 patients underwent TF-IMT at 60% of PImax and 10 control patients received sham TF-IMT at 10% of PImax. PImax, Pdi, SIPmax, and the endurance time as well as the nocturnal saturation improved significantly in the 60% training group (by 3.0 +/- 1.5 kPa, 3.4 +/- 1.9 kPa, 1.5 +/- 1.4 kPa, 189 +/- 149 s, and 1.9 +/- 2.2%, respectively), whereas no changes occurred in the sham training group. Also, significant correlations were observed between the changes in Pdi, SIPmax, and endurance time on the one hand and the change in nocturnal saturation on the other. We conclude that TF-IMT improves the nocturnal saturation in patients with severe COPD by increasing respiratory muscle strength and endurance.
The authors propose a method for adjusting results of log-linear multi-source capture-recapture estimates of total population. The method compares the totals in some subpopulations of known size with estimates derived from various capture-recapture approaches to these subpopulations. The authors term such an approach an "internal validity analysis". Trends in the ratios of the estimates to the known true values of these subpopulations provide a plausible indicator of the bias of some types of estimates of the total population especially when underlying assumptions of the methods used have not been met in analysis of the total population. The authors apply this method to published data on an open population of injection drug users that had been previously analyzed with a standard capture-recapture analysis as if it were a closed population. Internal validity analysis suggests that the size of this population is about 15% greater than that previously estimated.