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Chapter 11 GENERAL SUMMARY

The effects of acute infectious disease on physical fitness were investigated in 47 male and 33 female patients (mean age 25.8 and 26.1 years, respec- tively) hospitalized with various acute infectious diseases without cardiac complications. Twenty- two healthy men (mean age 25.0 years), confined to bed for the same period of time as the patients, served as a control group. The aims were to try to establish the extent and duration of physical de- terioration caused by illnesdbed rest; 1) as eva- luated by history and clinical signs, 2) as measured as reaction to upright exercise on the bicycle er- gometer, with determination of oxygen uptake and lactate production and measurement of the heart volume on X-ray, and 3) as measured as reaction to standing (orthostasis). Further, find- ings in patients and control subjects were com- pared in an attempt to evaluate the relative effects of bed rest and illness.

Apart from routine clinical procedures measure- ments were performed on four occasions: directly after illnedbed rest (occasion I); after about 1 month (occasion TI); after about 3l/z months (oc- casion 111); and about 1 year after illness in the patients (occasion IV); or, in the control subjects, 1 week prior to bed rest (occasion 0). Measure- ments of occasion 111 were used to represent the subject’s habitual level (= reference level). Mea- surements of occasion IV were performed to estab- lish possible clinical sequelae and, additionally - since such sequelae were not apparant - to con- trol the relevance of the measurements performed on occasion 111. Findings on occasion I11 and IV were usually similar.

The results indicated that clinical symptoms or signs possibly referable to circulatory dysfunction were present in 26.9 per cent of the patients 1 month after illness, while, 3 months after illness, only one patient suffered general tiredness.

In the male patients after illness, physical work- ing capacity expressed as work load at heart rate 150 beats/min (w150) was 79.3 per cent of that of occasion 111, while in the female patients it was 72.7 per cent of their reference level. The deterio- ration was, in relative terms, significantly more pronounced in the female patients. The control subjects deteriorated to 86.9 per cent of their refe- rence level as a result of bed rest. Except in those patients suffering pneumonia, there was no sta- tistical difference in amount of deterioration, either in relative or absolute terms, between male patients and control subjects although, on average, a tendency existed for the male patients to show a higher degree of deterioration in physical work- ing capacity. In the patients, the deterioration in maximal work performed (Wmax perf) roughly followed that of w150. Except in male patients suffering pneumonia, whose WISO values were lower, no significant differences referable to diag- nosis or aetiology were found. Change in pulse related physical working capacity from occasion I to 111 showed highly significant correlations to the duration of bed rest, while correlations to du- ration of illness or fever were lower. Multiple correlation analysis indicated bed rest to be the most important factor.

The reaction to orthostasis, measured as maxi- mal heart rate (HR) and mean HR during 8 mi- nutes standing, was not significantly altered by bed rest alone, but highly significant differences of 18.5-22.1 beats per minute were encountered in the patients when recordings on occasion I were compared to recordings on occasion 111. In the female patients the systolic blood pressure (BP, lowest and mean) during standing was similar on occasions I and 111, while the male patients showed a significant decrease after illness. The standing diastolic BP was significantly lower after

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illness/bed rest in the male patients and control subjects but not in the female patients who main- tained the same level.

The orthostatic dysfunction, expressed in terms of HR response, was significantly more pro- nounced in those patients who suffered from pneumonia than in the other patients.

Respiratory rate and ventilation volume tended to be higher on occasion I than on succeeding occasions, but bed rest alone had no effect on these variables. For the same absolute amount of work, oxygen uptake was lower on occasion I than on occasion 111, most differences being probably significant.

The blood lactate concentration, determined after the same absolute amount of work, was sig- nificantly higher on occasion I than on succeeding occasions in both patients and control subjects. An inverse pattern was seen when the working capa- city was expressed as percentages of the values of occasion I11 and related to a given lactate level (Wlact). On occasions I and I1 both the Wlact fraction and the Wl50 fraction of the female pa- tients were significantly lower than those of the

control subjects, indicating a greater relative de- terioration in the female patients. Similarly, these values were lower in the male patients than in the control subjects, but not significantly so. There were no significant differences in the Wlsct frac- tion when compared to the wl50 fraction on occa- sions I or 11, in each series of subjects, indicating that the deterioration was roughly parallel when expressed in "circulatory" or in "metabolic" terms.

In conclusion, the results confirm that cardio- vascular dysfunction occurs in patients confined to bed with acute febrile infections. Part of the deterioration is caused by the clinical bed rest but it is relevant to conclude that acute febrile infec- tion as such brings about an additional impair- ment. Thus, in the present study, with bed rest effects eliminated, orthostatic dysfunction has been shown to occur. On the other hand, the physical working capacity, expressed in different terms, was not significantly reduced by illness as such (except in pneumonia patients) although a consistent trend suggesting an additional effect added to that caused by bed rest alone was de- monstrated. Heart volume was not significantly altered.

ACKNOWLEDGEMENTS Technical assistance was skilfully rendered by Mrs Financial support was given by the Swedish De- Ninni Rosbn, medical technologist. legation for Applied Medical Defence Research

The author is much indebted for help and ad- (grant No. U65/73), by the Swedish Institute of vice to the scientific and technical staffs of the Defence Research (grants Nos. FMFD 74/75 and Departments of Infectious Diseases and Clinical FOA 75/76), and by the Faculty of Medicine, Physiology and Diagnostic Radiology, University University of Uppsa1,a. Hospital, Uppsala.