R e s e a r c h . A r t i c l e B e d r e s t A l ter s R e s p ir a t o r y M u s c l e S t r e n g t h in Pa t ie n t s Im m o b il iz e d D u e t o F r a c t u r e d F e m u r s PUCKREE T, BSc, MS, PhD'; MOONASUR R, B Physio2; GOVENDER K, B Physio3 1 Department o f Physiotherapy, University of Durban-W estville. B asic Physiotherapist, K in g Edw ard VIII H ospital, Durban. B asic Physiotherapist, W estville H ospital, Durban. A B S T R A C T : Bedrest produces decrements in the functioning o f all physiological systems. Physiotherapists treat patients who are managed with Thomas splints follow ing fractured fem urs. The patients are generally compartmentally treated as orthopaedic patients. No attention is p a id to the status o f the respiratory system which can be the cause o f morbidity in these patients . Since the ventilatdry muscles play a m ajor role in breathing and coughing the purpose o f the present study was to determine the effect o f a lim ited period o f bedrest on the strength o f the inspiratory and expiratory muscles. A sample o f convenience consisting o f 15 African male patients immobilized by Thomas ’ Splint f o r fractured m id-shaft fem u rs participated in the study by voluntary consent. A ll patients had been confined to bed f o r at least 3 weeks. M axim al inspiratory pressures (PiM AX) and M axim al expiratory pressures (PeMAX)were recorded using a Boehringer Force M eter at functional residual capacity in the semi-recumbent position. The data were norm alized and analyzed using the student t-test at the 0.05% level. The results show ed a significant reduction in both PiM A X and PeM AX compared to age predicted norm al values. The decrease in PeM AX was greater than that o f PiMAX. We conclude that respiratory muscle strength decays with bedrest. KEYWORDS: K E Y W ORDS : BEDREST, RESPIRATORY MUSCLES, W EAKNESS This research was presented as a poster at the 13 th international conference of the World Confederation of Physical Therapy held in Yokohama in May, 1999. INTRODUCTION: Follow ing certain types o f injury, other­ wise healthy subjects are surgically or m edically m anaged in a supine or semi- recum bent position for three to twelve weeks. The orthopaedic m anagem ent o f certain categories o f fractured femurs inclu d es sk eletal tractio n u sing a T hom as’ splint. Fractures o f the lower limb take a average 12 weeks to unite hence patients are kept in traction for m ore than 3 weeks. However, bedrest results in the deconditioning o f several ph y sio lo g ical system s (B rooks and Fahey, 1984) resulting in impairm ents, disability and handicap even in young patients. A sh er’s (1947) request to get patients out o f bed and save them an early grave, is sufficient to im ply the detrim ental effects o f bedrest on the normal functioning o f the various sys­ tems o f the body. T he resp irato ry system play s an im portant role in providing the body with oxygen and in the rem oval o f car- bon-dioxide (C 0 2 ). The effective func­ tioning o f the respiratory system is partially dependent on the strength o f the respiratory muscles which essentially act as a pump. The function o f the respi­ ratory m uscles can be directly affected by bedrest and indirectly affected by the position in which bedrest occurs (Ng and Stokes, 1991). The type and duration o f bedrest can reduce m axim al oxygen consum ption (V 02m ax) and w ork capa­ city from as little as 1% to about 26% (Brooks and Fahey, 1984). In supine, the vital capacity falls by 8-10 % i and with diaphragm weakness it may fall by more than 30% (Cam pbell et. al, 1970). The strength o f the respiratory m us­ cles determines the amount o f inspiratory and expiratory pressures that can be developed (Clanton and Diaz, 1989). The latter affects pulm onary volumes and tim ing, h ence breath in g depth and frequency. B edrest can produce decrem ents in the force production or strength and endurance o f the respiratory muscles (Clanton and Diaz, 1989, Chase et.al, 1966). This reduction in respiratory m uscle strength can result in poor ven­ tilation o f the lungs. Poorly ventilated areas can be susceptible to infection. N o studies have in v estig ated the effects o f bedrest on respiratory m uscle strength in orthopaedic patients. The strength o f the respiratory m uscles can be assessed clinically by m easuring the CORRESPONDENCE: T. Puckree Senior lecturer D epartm ent o f Physiotherapy, University o f Durban-W estville, Private Bag X54001 Durban, 4000, South A frica Tel: (031) 204-4977 Fax: (031) 204-4817 Email: lpuckree@ pixie.udw.ac.za SA J o u r n a l o f P h y s io th e ra p y 2000 V o l 56 No 4 27 R ep ro du ce d by S ab in et G at ew ay u nd er li ce nc e gr an te d by th e P ub lis he r (d at ed 2 01 3. ) mailto:lpuckree@pixie.udw.ac.za pressure generated by these m uscles (Clanton and Diaz, 1989). The maximum inspiratory pressure (PiM ax) and m axi­ m um expiratory pressure (PeM ax) are indices o f global inspiratory and expira­ tory m uscle strength respectively. These m easures are considered to be sensitive m easures o f developing m uscle w eak­ ness. Although not suitable for patients with rapidly developing m uscle w eak­ ness they are ideal for use on ortho­ paedic patients (Clanton and Diaz, 1989). Each o f these param eters is easy to measure using a calibrated m anom eter or electronic gauge (C lanton and Diaz, 1989). The purpose o f the present study was to determ ine w hether patients with fractured femurs on bedrest o f m ore than 3 weeks duration develop w eakness o f the respiratory muscles. METHODS: The sample o f convenience consisted o f 15 black males w ith ages ranging from 20 to 45 years. All patients had sustained fem oral m idshaft fractures and were m anaged on skeletal traction. T he patients were included if they had no history o f sm oking or an upper respi­ ratory tract infection in the 2 weeks prior to the study. These patients also had no history o f cardiopulm onary or neuro­ m uscular disease. All patients included in the study gave their full inform ed consent (by signing a consent form) to participate in the study w hich had ethi­ cal approval from the Ethics Com m ittee o f the U niversity o f Durban-W estville. INSTRUMENTATION A c a lib ra te d in sp irato ry /ex p irato ry force m eter (Boehringer Laboratories, G ounden,1985) w ith a b u ilt in leak previously used on quadruplegic patients was used to record PiM ax and PeMax. A standard plastic noseclip used in physiology laboratories was used to seal the nose during breathing. PROCEDURE E very patient who m et the inclusion criteria at one state hospital and had been on bedrest for a duration o f 3 weeks or m ore betw een M ay and August o f 1997, was included in the study. All the data were collected by the same investigator to eliminate inter-rater errors E ach p a tien t w as m o n ito red in the sem i-recum bent position. The procedure to be followed (as described below) was e x p lain ed to each su b ject and the process dem onstrated. The mouth was sealed around a standard spirom eter cardboard m outh-piece attached to the force meter. Because PiM ax recordings were taken at functional residual capa­ city (FRC), each subject was asked to relax completely, then to inspire rapidly and m axim ally and hold the breath for one second. A leak on the force m eter prevented the patient from using the buccal m uscles to generate pressure. The procedure was repeated five times w ith a one m inute rest betw een the readings. For the recording o f PeM ax, the subject was asked to relax com ple­ tely and then breathe out rapidly and com pletely. The highest o f each set o f five readings was used in the statis­ tical analysis. DATA ANALYSIS To m inim ize variation between subjects and reduce total error each subject’s m easured value had to be norm alized in relation to that subject’ age predicted value. Age predicted norm al values for each subject was calculated using the follow ­ ing form ulae (C lanton and Diaz, 1989). PiMax (adult male) in kPa 20-65 years (not race adjusted) = -14.02 + 0,054 *age m easurem ent at FRC = value obtained decreased by 14% converted to cm H 20 = (kPa*10.2) PeMax (adult male) in kPa 20-65 years (not race adjusted) = 26,27 + 0,101 *age m easurem ent at FRC = value obtained decreased by 19% converted to cm H 20 = (kPa* 10.2) Each subject’s m easured value was norm alized to that individuals age pre­ dicted value by calculating the m easured value as a percentage o f the age predicted value. M eans and standard deviations were calculated. Norm alized values were com pared to age predicted values by using a two tailed student t-test with a probability set at 0,05. RESULTS: Table 1 shows the measured, age pre­ dicted norm al, and norm alized values for each o f the 15 subjects. As shown only 2 o f the 15 patients retained at least 58% o f their predicted PiMax and only one patient was capable o f producing at least 30 % o f predicted PeMax- H ow ever the latter patient had the low­ est PiMax value o f 28%. Figure 1 shows bar graphs o f the m easured and age predicted values o f PiMax and PeMax- A significant decrease in both m easured PiMax and PeMax was observed com pared to age predicted norm al values. In addition a signifi­ cantly greater decrease was observed in PeMax values com pared to PiMax values. DISCUSSION: T h e strength o f respiratory m uscles determ ines the am ount o f inspiratory and expiratory pressures that can be developed during inspiration and expi­ ration (C lanton and Diaz, 1989). The latter affects pulm onary volumes and tim ing, hence breathing depth and fre­ quency. The results obtained dem on­ strate that both inspiratory and expiratory muscle strength was decreased due to bedrest in the study sample. The find­ ings are consistent w ith reports in the literature about decrem ents in various pulm onary param eters like V 0 2 max, vital capacity, etc with bedrest ( Brooks and Fahey, 1984). Clanton and Diaz(1989) reported that PiM ax and PeMax values are dependent on lung volumes. Resting lung volumes affect the length o f the m uscles which influences the ability o f each m uscle to generate force (C am pbell et al., 1970, De Troyer, 1983). The diaphragm is at an optim al position for generating force in the supine position (C am pbell et al,1970). I f the patients were on bedrest in the sem i-recum bent position as in this study, it is likely that the diaphragm was not only operating at a less than optim al length, but also was not exerted to its full potential at each breath, gradu­ ally resulting in decrements in respiratory 28 SA J o u r n a l o f P h y s io th e ra p y 2000 V o l 56 No 4 R ep ro du ce d by S ab in et G at ew ay u nd er li ce nc e gr an te d by th e P ub lis he r (d at ed 2 01 3. ) TABLE 1. Age, predicted, the measured PiMax and PeMax and normalized values (%) for each of the 15 subjects Subject Age Predicted PiMax Measured PiMax Normalized values ‘ Predicted i [ PeMax Measured PfiMax Normalized Values 1 26 135.3 65.6 48.5 195.4 45.7 23.4 2 34 139.1 62.4 44.9 188.7 46.0 24.4 3 36 140 61.2 43.7 187.0 46.0 24.6 4 25 134.8 71.5 53.0 196.2 50.7 25.8 5 34 139.1 63.9 45.9 188.7 39.7 21.0 6 41 142.4 63.0 44.2 182.8 50.1 27.4 7 24 134.4 64.0 47.6 197.0 42.9 21.8 8 28 136.3 38.6 28.3 193.7 60.9 31.4 9 25 134.8 78.8 58.5 196.2 43.4 22.1 10 29 136.7 74.1 54.2 192.8 49.2 25.5 11 35 139.6 59.9 42.9 187.8 . 50.8 27.0 12 38 141.0 63.6 45.1 185.3 52.8 28.5 13 36 140.0 82.1 58.6 187.0 54.5 29.1 14 42 142.9 63.5 44.4 1 182.0 37.6 20.7 15 29 136.7 68.5 50.1 192.8 52.7 27.3 Mean 32 135.3 65.4 48.3 190.3 48.2 25.3 FIGURE 1: m uscle strength. Sim ilar to other skele­ tal muscles that are im m obilized in pre­ scribed positions, the diaphragm and the other respiratory m uscles could develop contactures. The latter affects the strength producing ability o f these muscles in the short and long terms if sustained. It has also been shown that the type and du ratio n o f b ed rest can reduce V 02m ax , and w ork capacity from as lit­ tle as 1% to about 26% (Brooks and Fahey, 1984). In these subjects 3 weeks o f bedrest in the sem i-recum bent posi­ tion resulted in a loss o f up to 50% o f inspiratory m uscle strength and 75% o f expiratory m uscle strength. Large decre­ ments in respiratory m uscle strength in patients sim ilar to the study cohort can be prevented. M ore dynamic approaches to the treat­ ment o f patients with femoral fractures (Brooks and Fahey, 1984, Cam pbell et al, 1970) are recom m ended. A g reater d ecrease in expiratory muscle strength com pared to inspiratory OCN X Eu