THE EFFECTS OF BEDREST AND THE INITIAL POSTOPERATIVE ACTIVITY OF CHAIR-SITTING ON OXYGEN BALANCE AND OTHER RESPONSES IN CORONARY ARTERY BYPASS GRAFT PATIENTS: A VALIDATION STUDY FOR THE NURSING DIAGNOSIS OF ACTIVITY INTOLERANCE.
Contributors: University of Texas at Austin.
Published: 1994
Number of pages: 272
Subjects: Health Sciences, Nursing.
Description: A descriptive, correlational study with a repeated measures design was employed to identify indicators and contributing factors of tolerance to the initial post-bedrest activity in a homogeneous sample of critically ill patients. The sample consisted of 25 coronary artery bypass graft (CABG) patients (19 men, 6 women) between the ages of 42 and 69 (M = 60). Heart rate and rhythm, ST segment deviation, systolic and diastolic blood pressure, dyspnea, fatigue (preceived exertion and ratings on a visual analogue scale), weakness, and angina were measured before, during and after the first postoperative chair-sitting activity. Data to calculate oxygen consumption (VO$\sb2),$ oxygen delivery (DO$\sb2),$ and the oxygen extraction ratio (O$\sb2$ER) were also measured at each time period. Measurements were obtained at four times: with patients in the supine position (baseline), immediately after moving to a bedside chair, after 15 minutes of sitting, and at the end of 10 minutes of rest after the return to bed. Total time in the chair was 20 minutes. Prior to activity, the subjects had been on continuous bedrest since surgery (M = 31 hours).

Mean heart rate, systolic blood pressure, dyspnea, exertion, VO$\sb2$ and O$\sb2$ER were significantly greater than baseline after moving to the chair. At the end of chair-sitting for 15 minutes, heart rate, dyspnea, exertion, and VO$\sb2$ had returned to baseline, but systolic and diastolic pressures were significantly lower than preactivity values. O$\sb2$ER decreased but remained significantly greater than baseline at the end of sitting and 10 minutes of postactivity rest. O$\sb2$ER was greater than normal at each data collection period. During postactivity rest, all other parameters except heart rhythm returned to baseline. A significant increase in premature ectopic arrhythmias was seen only in the postactivity period. Two patients had clinically significant changes in ST segments which also occurred only during postactivity. All patients denied angina and no significant changes were seen at any time in DO$\sb2,$ weakness, and fatigue ratings on the visual analogue scale. A significant negative correlation was found between O$\sb2$ER and SBP during and after activity, otherwise correlations between the dependent variables and O$\sb2$ER and with bedrest were consistently low and nonsignificant.

DO$\sb2$ was below normal throughout the study and was attributed to low postoperative hemoglobin levels and small changes in cardiac output. The increase in oxygen consumption in the presence of a low oxygen delivery placed the patients at risk for an oxygen supply/demand imbalance; however, high oxygen extraction ratios and generally small, transient changes were seen in most of the parameters during and after activity. These findings indicate that the increased tissue oxygen extraction was sufficient to maintain homeostasis without major adjustments in the other responses. Consequently, oxygen extraction appears to have mediated activity responses and is seen as a contributing factor for activity tolerance. (Abstract shortened by UMI.).
Notes: Source: Dissertation Abstracts International, Volume: 55-10, Section: B, page: 4324.

Thesis (PH.D.)--THE UNIVERSITY OF TEXAS AT AUSTIN, 1994.

School code: 0227.