Chest
Volume 101, Issue 2, February 1992, Pages 432-436
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Clinical Investigations
Postthoracotomy Respiratory Muscle Mechanics During Incentive Spirometry Using Respiratory Inductance Plethysmography

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We undertook this study to characterize the postthoracotomy compartmental displacement and respiratory mechanical changes occurring during and after the performance of the incentive spirometry maneuver. We also evaluated the effect of recumbency angle on compartmental recruitment. Sixteen patients were randomized to perform incentive spirometry either at 30° or 60° recumbency angle. They were studied using respiratory inductance plethysmography to measure tidal volume, respiratory frequency, inspiratory time, rib cage motion/tidal volume ratio, inspiratory duty cycle, and inspiratory flow. Patients were studied before surgery and on postoperative days 1 and 3. Statistical analysis was accomplished using multiple measures ANOVA with post-hoc Student's t-tests when appropriate. Preoperative incentive spirometry augmented VT by increasing both VT/TI and TI. Postoperatively, the incentive recruitment of VT was reduced, a result of a decrease in TI and TI/TTOT; VT/TI was unchanged. There was postoperative decrease of AB and AB/Vr during incentive spirometry, greatest in the 60° group. Our results characterize the nature of the respiratory recruitment afforded by incentive spirometry, before and after thoracotomy. We also found evidence of postthoracotomy diaphragmatic derecruitment during incentive spirometry exacerbated by a high recumbency angle.

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Subjects

Sixteen patients, 11 men and 5 women, scheduled for elective thoracotomy were studied. Informed consent was obtained from all subjects according to the guidelines of the Institutional Review Board of Memorial Sloan-Kettering Cancer Center. Patients were excluded from participation in the study if they were concomitantly suffering from a severely debilitating medical or psychiatric illness, weighed under 50 kg or over 100 kg, or found to have a pleural effusion. Patients ranged in age from 30 to

RESULTS

There were no significant differences between the populations in height, weight, age, percent predicted FVC and FEV1/FVC at 30° and 60° angle of inclination (Table 1). The postoperative pain score prior to the study sessions averaged 2.1 ±0.6 ranging from 1 to 5. There was no significant difference in pain scores on postoperative day 1 and day 3. Total daily doses of morphine sulphate administered was greater on postoperative day 1 than on day 3 (0.42 ±0.01 mg/kg vs 0.17 ±0.01 mg/kg,

DISCUSSION

Respiratory complications remain the most important cause of postoperative morbidity following thoracotomy. Previous investigators have shown that between 10 and 50 percent of patients who have undergone thoracic surgery have evidence of postoperative pulmonary abnormalities.15, 16 Incentive spirometry is one of the mechanical aids used to increase lung volume and reduce the incidence of such complications.6 This study characterizes the global respiratory mechanical changes that occur during

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  • Cited by (0)

    This study was supported by a starter grant from the Society of Cardiovascular Anesthesiologists.

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