Chest
Volume 97, Issue 3, March 1990, Pages 618-620
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Clinical Investigations
Variation in Maximum Inspiratory and Expiratory Pressure after Application of Inspiratory Loads in Patients with COPD

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We studied eight men with chronic obstructive pulmonary disease (COPD) (age, 60.57 ± 7.59 years; height, 162 ± 10.43 cm; weight, 65 ± 9.7 kg). Functional values of the sample were as follows: FEV1, 46 percent; FVC, 67 percent; PO2, 72.4 mm Hg; and pH, 7.41. We used a modification of the Nickerson and Keens method. Patients were required to perform 65 percent of maximal inspiratory pressure (MIP). We counted the time from the start of the test to exhaustion of the patient (TLIM). We measured basal MIP and maximal expiratory pressure (MEP) (TLC) at the TLIM and 10, 20, and 30 minutes and MIP was different from the basal value (MIP basal, 85.7 cm H2O; MIP 10 minutes, 79.1 cm H2O; MIP 20 minutes, 78.6 cm H2O; MIP 30 minutes, 79.6 cm H2O. The MEP was not different from the basal value. We concluded that in patients with COPD, MIP decreases significantly after inspiration through umbral inspiratory weight equal to 65 percent MIP and does not return to basal value for 30 minutes. The MEP does not change with respect to basal determination.

Section snippets

PURPOSE

The purpose of this study was to evaluate the possible variation of the maximum inspiratory and expiratory pressures after the application of inspiratory loads generating 65 percent of MIP in patients with stable COPD.

Sample

The study was conducted on eight male patients with COPD in stable phase, that is, the patients had not shown any symptoms of acute relapse in a period of at least two months prior to the study. The average age was 60.57 ± 7.59 years, the height was 162.14 ± 10.43 cm, and the weight was 65 ± 9.7 kg. The patients did not have any other type of cardiorespiratory, endocrine, neuromuscular, or hepatic illness. We explained the protocol to be followed and all patients gave their consent. Various

RESULTS

It can be seen in Table 1 that there is evidence that the patients suffered a moderate obstruction of air flow and the volumes are increased. Three of the patients had a Dco of less than 80 percent due to clinical and radiologic signs of pulmonary emphysema.19 The average TLIM of the sample was 3.7 ± 1.96 minutes. The anthropometric measurements were normal.

Table 2 shows the MIP and the MEP of the patients at the basal stage, on exhaustion, and at 10, 20, and 30 minutes following exhaustion.

DISCUSSION

The studies that have been performed on respiratory muscle endurance are based on the capacity of the respiratory muscles to sustain and generate high levels of pressure. The most common test consists of generating a pressure against a given resistive inspiratory load.1, 2, 3, 20 In our study, we used the Nickerson, Keens and Kelsen methods,3, 4, 21 that consist of breathing through a constant threshold load equivalent to 65 percent of the MIR This pressure lies within the range of critical

CONCLUSIONS

On the basis of foregoing results, it may be said that the MIP decreases in the patients with COPD after the application of inspiratory loads equivalent to 65 percent of MIP The drop in MIP begins to take place at the end of the test and becomes significant ten minutes after exhaustion, without returning to its basal value even beyond 30 minutes after the end of the test. The MEP does not vary with respect to the value obtained at rest.

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    Supported by grant FISS88.

    Manuscript received April 6; revision accepted August 31.

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