The Science Journal of the American Association for Respiratory Care

1996 OPEN FORUM Abstracts

EVALUATION OF FORCED EXPIRATORY PRESSURE AS AN INDICATOR OF RADIOGRAPHIC ABNORMALITY IN THE SPINAL CORD INJURY PATIENT

AUTHORS: WT Peruzzi MD, ML Ault MD, ML Franklin MD, TA Sondergeld RRT, PR Meyer MD, RD Cane MD, BA Shapiro MD. AFFILIATION: Department of Anesthesiology, Northwestern University Medical School, Chicago, IL 60611 (Res. Grant # H133M-00008) Recognition to The Frankel Foundation.

Introduction: Using roentgenographs to evaluate the presence of pulmonary abnormalities such as atelectasis and infiltrates is a common practice. Beside parameters such as vital capacity (VC) and negative inspiratory force (NIF) have been used to assess the ability to initiate a deep breath prior to a cough. Since these parameters reflect only the initiation of the cough response, other factors such as the ability to generate positive airway prossure remain unmeasured. Spinal cord injuries (above the lumbar level) may interfere with the ability to generate enough positive pressure. Therefore, we hypothesized that forced expiratory pressure measurements (FEP) may be a better predictor of the spinal cord injury patient's inability to participate in bronchial hygiene, thereby leading to atelcctasis and/or infiltrates on chest x-ray.^{1} Methods: IRB approval was obtained, and all unintubated patients admitted to our spinal cord injury intensive care unit in a twelve month period were approached for consent. Daily measurements of VC (measured by Wright spirometer model # 700-020), FEP, and NIF (both measured by Boehringer manometer, model # 400) were obtained for a maximum of 5 consecutive days in enrolled patients. Chest X-rays were obtained and read by blinded attending radiologists when clinically indicated over the same consecutive days. The average VC, FEP, and NIF values were then compared between the two roentgenograph groups classified as either absence (CLR) or presence (POS) of atelectasis and/or infiltrate. Statistical analysis was then performed using an unpaired Student's t-test. Results: Seventy-six patients with varying levels of cervical and thoracic injury consented for enrollment in the study. A total of 123 chest x-rays were evaluated. The table demonstrates the differences in respiratory parameter values between the two roentgenograph groups. Conclusion: It was our original hypothesis that FEP would best predict an effective cough. However, our data do not support this hypothesis. We have demonstrated that VC is a better predictor of roentgenograph evidence of inadequate bronchial hygiene. Measurements of airway pressure changes may be unreliable indicators of cough effectiveness because these factors indicate only respiratory muscle function. VC is however, dependent upon both respiratory muscle function and functional lung parenchyma. Thus, vital capacity may be the most sensitive indicator of chest x-ray abnormalities in this patient population.

xPOS(n=35) SD xCLR(n=88) SD p-value

VC 1400 ±531 1785 ±831 0.012

FEP 76 ±34 72 ±31 0.540

NIF -84 ±41 -88 ±43 0.706

^{1} Shapiro, BA et. al: Clinical Application of Respiratory Care, 4th ed., 1991, pp. 448-452.

Reference: OF-96-098

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