Variation in Maximum Inspiratory and Expiratory Pressure: MATERIAL AND METHODS

25 Apr


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 tests were conducted simultaneously within the first week of inclusion in the study.

Respiratory Function Study

An OHIO 827 unit (Sensor Medics) was used to determine the following factors: simple and postbronchodilator spirometry and measurement of pulmonary volumes by the technique of helium dilution and CO transfer (Deo, KCO). The American Thoracic Society rules were followed and the values found were compared with those gathered in the normal population.
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The MIPs and maximum expiratory pressures (MEPs) were measured from residual volume and TLC by the method of Black and Hyatt. To obtain these values, a dry manometer connected to a pressure transducer with range of 0 to 300 cm HaO (Sibelmed) was used. The signal was amplified and polygraphically recorded by means of a 12-channel polygraph (Sensor Medics).

To obviate the learning effect, a minimum of ten maneuvers were performed until at least three of the determinations varied by less than 5 percent. The maneuvers were repeated immediately after finishing the load test and after 10, 20, and 30 minutes.

Inspiratory Load Test

A modification of the Nickerson and Keens method4 was applied. After placing the patient in the sitting position with his back resting against a rigid support, application was made of a noncollapsible mouthpiece joined to a Hans Rudolph two-way valve (2700) in which another valve was installed, and different weights were inserted through the latter. The weight was increased until the patient generated a mouth pressure equivalent to 65 percent of his MIP (threshold pressure). Once the proper load was known, the patient breathed through the device until the threshold pressure calculated during three consecutive breaths ceased to be generated (exhaustion). The time that elapsed from the start of the test to exhaustion (TLIM) was counted. During the test, the pressure exerted was controlled at all times by a polygraph recording, preventing it from dropping below the threshold pressure. The inspiratory time-total time ratio (Ti/Гтот) was kept constant and the respiratory frequency was approximately 20 breaths per minute.

Nutritional Study

As part of the nutritional study, the following measurements were taken: weight as a percentage of the control, body fat content measured as a percentage of total body weight (triceps pinch with caliper), and circumference of the upper arm in order to obtain muscle content. In all measurements we followed the rules of Driver and Lebruw.
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Statistical Study We applied the Friedman test and a Wilcoxson test of sign-range.