Chronic Obstructive Pulmonary Disease. Key Words: Diaphragm, Exercise tolerance, Inspiratoly muscle training. Threshold training. The purpose of this article is ...
Focus on Ventilatoty Muscle Training Clinical Perspective
Respiratory Muscle Training for Patients With Chronic Obstructive Pulmonary Disease
The purpose of this article is to describe respiratoly mzsscle traini~zgtechniques and the effectiveness of this training in patients with chronic obstructi~tepulmonary disease (COPD). The respiratoly muscles can be strengthened, but the benejt of stronger respiratol~),muscles in patients with COPD is not clear. Maximal szlstazned voluntary ventilation, inspiratoy resistive breathing, and threshold loading are the three most commonly used techniques for improving the endurance of the inspiratoly muscles in patients with COPD. Recent studies using inspiratory resisti~tebreathing with targeted devices or threshold trainers hat~eshown more consistent increases in inspiratory muscle function and exercise tolerance than studies using other techniques. Endurance exercise involving the extremities improves inspirato y muscle endurance in younger individuals with cystic fibrosis but not in olderpersons with COPD. Recommendations are outlined regarding the techniques to use for respiratory muscle training and which patient populations may benejt from these techniques, [Reid WD, Sanzrai B. Respiratory muscle training for patients with chronic obstructive pulmonaly disease. Phys Ther. 1995;75996-1 005.1
W Darlene Reid Baljit Samrai
Key Words: Diaphragm, Exercise tolerance, Inspiratoly muscle training. Threshold training.
Chronic obstructive pulmonary disease (COPD) is a group of conditions characterized by airway obstruction. The term "chronic obstn~ctivepulmonary disease" is usually used to refer to a combination of primarily chronic bronchitis and emphysema but can include other conditions such as asthma, bronchiectasis, and cystic fibr0sis.l In this article, the term
"chronic obstructive pulmomary disease" will be used to describe a combination of chronic bronchitis and emphysema, whereas other obstructive lung diseases will be identified with their specific term. Chronic obstructive pulmonary disease and cystic fibrosis are progressive, incurable conditions that incur large health care costs, result in loss of workdays, and
WD Reid, PhU, BhlRtPT), is Assistant Professor, Division of Physical Therapy, School of Rehabilitatlon Sciences. Klniversity of British Columhia. T325-2211 Weshrook Mall. Vancouver, British Columbia, Canada V6T 2Bi iwdreidQunixg.ubc.ca). Address all correspondence to Dr Reid.
B Samrai, BSc, is a graduate student. Experimental Medicine, University of British Columbia This article was presented in part for the presentation titled ,'Ventilatory Muscle Training and the COPD Client" in the symposium Ventilatory Muscle Training: Principles and Practice at the Canddian Physiotherapy Association-Amencan Physic:~lTherapy Association Joint Congress; Toronto. Ontario, Canada; June 4-8, 1994.
eventually will lead to very limited mobility due to increased dyspnea and decreased exercise tolerance. Interventions that may improve and maintain mobility would be valuable to these patients. Conditions characterized by chronic airflow limitations can result in impaired respiratory muscle function because of respiratory muscle weakness, increased work of breathing due to changes in the lungs, and inefficiency of the inspiratory muscles because of hyperinflation. Respiratory muscle weakness may occur because of systemic abnormalities such as poor nutrition, abnormal arterial blood gases, and disuse. Increased work of breathing results from airway obstruction, which contributes to dynamic
Thzs artzcle was subttzitted April 5, 1995, nnd ubasacceptedJuly 14,1995
70 / 996
Physical Therapy / Volume 75, Number 11 /November 1995
airway compression and hyperinflation. Hyperinflation places all of the inspiratory muscles at shorter-thannormal lengths and at a mechanical disadvantage, with the diaphragm being affected to the greatest degree. (See article by Reid and Dechman in this issue for complete explanation, with figures.) The etiology of poor respiratory muscle function in patients with COPD is not clear. Roussos2 hypothesized several years ago that the respiratory muscles in individuals with COPD are susceptible to respiratory muscle fatigue. More recently, Rochester.' postulated that weakness rather than fatigue is present in the respiratory muscles of some groups of patients with COPD. Discerning the diference between weakness and fatigue is often difficult. Regardless of whether weakness or fatigue is present, poor inspiratory muscle function is an important factor contributing to exertional dyspnea, exercise intolerance,' and, as diseases progress, to hypercapnic ventilatory failure in patients with COPD.2,3Respiratory muscles, similar to limb muscles, improve their function in response to training. This improved function, in turn, could potentially decrease dyspnea, i m p r o ~ ~exercise e tolerance, and increase the ability to do daily activities, and may reverse hypercapnic ventilatory failure. During the last 15 years, a plethora of studies have been performed examining the benefit of respiratory muscle training in patients with COPD. As with all clinical studies, dficulties were encountered, and often the clinical design and the training techniques were not optimal. These factors resulted in controversial results. More recently, however, improved training techniques have consistently demonstrated positive outcomes from respiratory muscle training in several different conditions involving airway obstruction. This article will describe different respiratory muscle training techniques and the effectiveness of respiratory muscle training in patients with chronic airflow limitation. Finally,
some recommendations will be given regarding the techniques to use for respiratory muscle training and which patient populations may benefit from these techniques.
Training Principles The principle of specijicity of training states that the effects of training are very specific to the neural and muscular elements overloaded. According to this principle, respiratory muscle training will improve respiratory muscle function during day-to-day activities when the type of recruitment pattern during training is most similar to the recruitment pattern required during those activities. Of greater importance, respiratory muscle training will only be of benefit to the patient if respiratory muscle function is a major limiting factor during the performance of activities. The overload principle states that an overload must be applied to a muscle for a training response to occur. This overload may be applied by increasing the frequency of training, the duration of training, the intensity of the loading, or a combination of these factors. Many studies examining the benefit of respiratory muscle training have probably been unsuccessful because an inadequate overload was applied as a result of the type of training device used. Revenibility implies that the effects of training are transient. As soon as the individual stops training, the structural and functional changes within the body related to training will begin to return to baseline. The principle of individual dzfferences states that all individuals are different, so their needs and abilities should be considered before designing an exercise program. We currently have no criteria to select which individuals may benefit most from respiratory muscle training.
Respiratory Muscle Strength Training Force production of the respiratory muscles can be improved through specific strength training in young asymptomatic individuals,"n elderly individuals,' and in those with COPD.' Inspiratory muscle force also improves
Physical Therapy / Volume 75, Numbe,r 11 / November 1995
in response to some inspiratory muscle endurance training protocol^.^-^^ Respiratoy muscle strength training can be defined as the performance of high, near-maximal inspiratory or expiratory maneuvers that are usually quasi-isometric,' ' The repetition rate is low (range=5"-20' repetitions). The primary goal of strength training is to improve force production of the respiratory muscles. Respiratory muscle strength training is probably not important clinically except in cases of neuromuscular weakness.17 In these conditions, training of the expiratory muscles may be very important for the production of an effective cough.
Respiratory Muscle Endurance Training Because the main function of the respiratory muscles is to perform lowintensity contractions about 10 to 20 times per minute throughout the life span, endurance training of the inspiratory muscles is much more important than strength training for individuals with COPD. In addition, endurance is decreased more than force production in patients with COPD compared with normal values.lXRespiratory muscle endurance training can be defined as repetitive, shortening contractions that are in coordination with the breathing pattern. The duration is usually at least 15 minutes, and the endurance training may consist of a continuous or multiple-interval training period. Three major types of respiratory muscle endurance training techniques have been developed: maximum sustained voluntary ventilation (MSW)," inspiratory resistive breathing,H and threshold loading.10 The advantages and disadvantages of each of these techniques will be outlined. In addition, the outcomes from each type of training in individuals with chronic airflow limitation will be discussed.
Maximum Sustained Voluntary Ventilation Maximum sustained voluntary ventilation, the least practical training rechnique, requires the individual to hy-
-
Table I. Effects of Maxiinllnz Sustained L'oluntary Ventilatiolz"
Reference
Leith et aI6
Duration, Frequency, and Time Course of Training
Outcome
Subjects and Groups
N: 4C, 4s
20-30 min, 5x/wk, 5 wk
19%
IM Endurance
T MSVC
Exercise Tolerance
Not measured
4 MSW Keens et aI2"
7 CF/Ex 4 N/MSW 4 CF/MSW
25 min, 5x/wk, 4 wk
CF/Ex: 57% f MSVC N/MSW: 22% f MSVC CF/MSW: 52% f MSVC
No A in i/o,max predicted from submaximal exercise testz4
Belman and Mittman"
15 min, 2x/d, 6 wk
33% f MSVC
f TI,, for arm and leg ergometry and 12 MD
Belmanz3
10 COPD (no C group) 2 COPD
15 min, 1-6x/di,
52?6 f MSVC (NS)
Not measured
Ries and Moserlg
COPD:
3x/d, 6 wk
29% f MSVC (NS)
T f
6 wk
5 MSW
i/o,max
and i/~maxin MSW group
TI, on TM
7 Ex Levine et alz2
COPD: 15 MSW/IPPB 17 IPPB
15 min daily, 6 wk
41%
T
MSVC
f TM and cycle ergometer tests and ADL for both MSW/IPPB and IPPB groups
"Asterisk (*) indicates 3-6Xl'd while o n ventilatory support: 1 X / d for 5 wk while on ward after intensive care. ADI.=activities of cl;~ilyliving; C=control: CF=cvstic fibrosis; COPL)=chronic obstructive pulmonary disease; Ex=endurance exercise involving the extremities: TM=inspiratory nluscles: IPPR=interrnittent positive pressure breathing; MSVC=maximuni sustained ventilator) c:~p;~city; MSW=rnaxilnum sustained voluntary ventilation; N=;isyrnptomatic individuals; NS=nonsignificant; RF=respirato~yhilure; S=IM strength trainers; T,,,,=endurance time; TM=tre;~dniill: ~c),max=maximal oxygen consumption; \i~max=rn;iximum expiraton. minute ventilation: 12 MD=12-minute walk distance: A=cl~ange.
perventilate for 15 to 25 minutes. Because the person is hyperventilating, which decreases the partial pressure of carbon dioxide (arterial) level. equipment is necessary to maintain arterial blood gases within a physiologic range. An elaborate apparatus is used that consists of (1) equipment to monitor and adjust inspiratory oxygen and carbon dioxide levels, (2) a target such that the person can pace himself or herself at a defined minute ventilation, and (3) a measuring component to determine the amount ventilated. The conlbined cost of this equipment is likely in excess of $50,000 (Canadian), so M S W is not a useful technique for large numbers of patients, and is not convenient as a home training technique. Home use of an M S W training apparatus, however, has been reported. l" Although this training technique requires costly equipment, rendering it less practical than other training techniques, it is likely the best technique for purely improving endur-
'Available from DHD Medical Products,
72 / 998
another report.LLOther researchers did not measure the effect of MSW training on exercise t~lerance"~'or only estimated n~aximaloxygen consumpMaximum sustained voluntary ventilation from submaximal e x e r c i ~ e . ~ ~ , ~ ~ tion training has been used in several studies of asymptomatic indi~iduals,"~~)M,iximum sustained voluntary ventilation training appears to improve inthose with cystic fibr~sis,~" those with COPD,19,21,22 and those with COl-'D in spiratory muscle endurance; however, respiratory failure2"Tab. 1). In these the benefit of this technique on exerstudies, the duration of training was cise tolerance is less clear. Further, the usually 15 to 30 minutes per session, complexity of the training apparatus the frequency of training ranged from hinders the wiclespread use of h l S W as a home training technique. three to six times a week, and the time course of training was between 4 and 6 weeks. Several reports6J-22 lnspiratory Resistance Training showed an increase in the maximum sustained ventilatory capacity, alInspiriitory resistance training is probably the most popular respiratory musthough only nonsignificant trends toward improvement were shown in cle training technique used to date. two studies. 1q.2Waximum sustained One inspiratory resistance trainef voluntary ventilation training increased consists of a mouthpiece attached to a exercise tolerance in patients with T-piece with a one-way valve on one COPD in uncontrolled2' and conside and a nonlinear inspiratory resistrolledl%t~udies.and showed a similar Lance attached to the other side. A increase :is an intermittent positive nonlinear resistance changes in intensity when flow rate is altered.2i During pressure breathing treatment group in inspiration, the one-way valve closes, so the person must breath against the nonlinear resistance, which is a colDiemolding Hea1thc:ire Division, CanJstot:~,NY 13032. ored disk with a small hole in the ance at high speeds of n~uscle contraction.
Physical Therapy /Volume 75, Number 11 / November 1995
Table 2. Effects o f Znspiratoly Resistive Breathing Duration, Frequency, and Time Course of Training
Outcome IM Force and Endurance
Exercise Tolerance
Reference
Subjects and Groups
Andersen et aIz6
10 COPD*
30 min daily, 4 + 8 wk
J EMG,,
T
ADL
Secher et aI3"
81 COPD (6 groupst)
15 min, 3x/d, 6-13 wk
Not measured
T
stair climbing in all groups with face mask, even those with no loads
Sonne and Davis34
6 COPD*
30 min daily, 6 wk
T
MIR for 10 min
T
~ o ~ r n aVE x ,and maximum work load on cycle ergometer
Asher et ale
11 CF-crossover C
15 min, 2X/d, 4 wk
T
MIP, min
No A in submaximal or maximal Ex on cycle ergometer
MIP
MIR for 10
Larson and Kimzg
9 COPD*
15 min, 2X/d, 1 mo
T
Jones et aI3O
COPD: 11 Ex 11 IR, 8 sham
15 min, 2 x/d, 10 wk
Not measured
T
Belman et alZ7
COPD: 10
15 rnin daily, 6 wk
No A n MIP, MIR, MSVC
Not measured
Noseda et aI3'
COPD: 12 IR, 13 BR*
15 min, 2x/d, 8 wk
Richardson et a13'
COPD: 6 max 30 min, 5x/wk, 6 wk IR, 6 progressive IR, 4 sham
Guyatt et alZ8
COPD: 43 IR 39 C
Coaching IRT
Pardy and c:olleag~es'~,~~ COPD: 8 Ex, 9-1 2 IR*
T
J 12MD
T
maximum work load on cycle ergometer test
MIR
MIR in IR group
No A in 12 MD or submaximal or maximal Ex on cycle ergometer
No A n MIP and Pmean at maximum load
Not measured
10 min, 5x/d, 6 mo
No A in MIP and T,,, on progressive IR
No A in 6 MD and T,, on progressive bike ergometer test
30 min daily, 2 mo
J EMG,,
T
12 MD and TI,, on submaximal bike ergometer test in IR group
"Asterisk ('11 indicates no control group. Dagger (t) indicates several groups with and without a face mask. Four groups with the face mask had different inspiratory and expiratory loads or no loads. Double dagger ($) indicates control period before training period. ADL=activities of claily living; BR=hreathing retraining; C=control; CF=cystic fibrosis; COPD=chronic obstructive pulmonary disease; EMG,,,=electromyographic signs of diaphragm fatigue; Ex=endurance exercise involving the extremities; IM=inspiratory muscles; IR=inspiratory resistance; IRT=inspiratory resistance trainers: hlIP=rnaxirnal inspiratory pressure; MIR=maximal inspiratory resistance: MSVC=maximum sustained ventilatory capacity; Pmean=mean pressure during threshold load; T,,,,,=endurance time; Vo,max=maximal oxygen consumption: ~emax=maximalexpiratory minute ventilation; A=change: 6 MD=6-min~utewalk distance; 12 MD=12-minute walk distance.
center. During expiration, the one-way valve opens, so expiration is unimpeded. The disks can be changed and vary in diameter from 2.0 to 7.1 mm. The P-flext is another inspiratory resistance device, but rather than changing the disks in order to adjust hole size, a dial can be adjusted to a larger or smaller hole (range in diameter= 1.5-5.1 mm). In several studies, the benefits of IRT have been examined in individuals with COPD2G-3hnd those with cystic fibrosis8 (Tab. 2). For the most part,
the duration of training was 30 minutes (range=15-50 min), the frequency of training was either five times per week or daily, and the time course of training sessions ranged from 4 weeks to 6 months. Success from IRT in individuals with COPD has been variable. In many of the studies, there were no control gro~ips26,29,3* or Functional indexes such as exercise tolerance or Functional abilities were not u ~ e d . ~ 7Not ,3~ all the studies demonstrated an improved respiratory muscle endurance
+~vailable from HealthScan Products Inc, Unit 8-2, 908 Pornpton Ave, Cedar Grove, NJ 070091292
Physical Therapy / Volume 75, Number 11i November 1995
or exercise tolerance (Tab. 2). During most of these studies,j"~j'~~?-~6 including a large double-blind, controlled clinical no attempt was made to control the breathing pattern or to monitor the pressure generated during IRT and testing trials. Because of these limitations, the validity of training and testing is suspect. Richardson et aP2 noted that most patients breathing against inspiratory resistance trainers in their study were working below the fatigue threshold, and therefore the intensity of training was probably not sufficient to improve inspiratory muscle endurance. Belman et alL7found that encouraging a slow breathing pattern during IRT improved inspiratory muscle endurance in contrast to
o1
I
I
I
1
1
10
20
30
40
60
PRESSURE (cm H,O) Figure. Pressure-flow characteristics oj' norzlinear resistuncc~strsed irz a respiratoy nzuscle training stu~$l,forpatientswith chronic obstructiuepzrlmona y disease. (Reprinted with permission from Reid and W7arren.')
results obtained in a similar group of patients when an uncoached breathing pattern using the inspiratory resistance device had no effect. The problem with the inspiratory resistance devices is that the resistance 1s nonlinear. If the person breathes in slowly, only a small effort is required to create a low pressure to produce flow, whereas if the person breathes in more quickly. a larger effort is required to produce the larger pressure to achieve the higher flow ratez5(Figure). The lack of beneficial effects in some studies may hrlve been due to patients changing their breathing patterns in order to make the load easier rather than working against the inspiratory resistan~e.~~,3~ Further, the demonstration of an increase in the maximal inspiratory resistance (MIR) sustained during testing in some stud-
74/ 1000
ies (Tab. 2) may have been due to an altered breathing pattern rather than improved inspiratory muscle endurance. Therefore, the breathing pattern and flow rate must be monitored carefully and controlled throughout every testing and training session when using inspiratory resistance devices. lnspiratory Resistance Training Using Targeted Techniques
Recently, efforts have been made to control breathing patterns during IRT by using ta~getedtechniques. The targeted device used by Dekhuijzen et al" is probably the simplest and most practical to use. They attached an inspiratory resistance to an incentive spirometer. The physical therapist modified the flow adjustment on the incentive spiroineter such that patients
had to exert 70% of their maximal inspiratory pressure (MIPI to keep the ball at the top of the incentive spironleter during tra~ning.The device used by Hanrer et all1 was a modified P-flex device with a latex sleeve between the mouthpiece and the inspiratory resistance. The sleeve nras connected to a needle, and subjects had to inspire with sufficient force to deflect the needle a significant amount. The feedback device used by Belman and Shadmehf)7' appears to be the most complex compared with other targeted devices, but these investigators demonstrated that patients were able to learn how to use the device. The inspiratory resistance breather was attached to a little box. On the box, a green light went on and off in order to time inspiration and expiration, respectively. The patient was instructed to breath in during the time that the green light was on. A scale at the top of the device gave an indication of the magnitude of pressure genel~ited,and a red light went on when the maximum pressure was generated. Recent studies using IRT with targeted devices have consistently shown positive results (Tab 3) in contrast to the inconsistent benefits shown with the use of a nonlinear resistance trainer alone (Tab. 2). In addition, the experimental design of all three studies included another treatment for the control group, either low-intensity tralningv.' or pulmonary rehabihtation." All three studies showed inlprovement in indexes of respiratory muscle force (MIP) or endurance (reduced electromyographic signs of diaphragm fatigue," higher training pressure^,",^ or higher maximum sustained ventilatory capacity?. In addition, greater improvement in exercise tolerance9l 3 and less dyspnea1I were shown than in the other treatment group. From the data presented in Tables 2 and 3, it would appear that the use of a targeted device is essential to optimize benefits from IRT. Threshold Loading
Threshold loading is probably the most practical approach to inspiratory muscle training to date. This technique
Physical Therapy / Volume 75, Number 11 / November 1995
Table 3. Effkcts of 7iilgc>tedTechniquesu
Reference
Duration, Frequency, and Time Course of Training
Subjects and Groups
Outcome
Dekhuijzen et all3 COPD: 20 Rehab; 20 IMT and Rehab
2 hr Rehab, 5X/wk, 10 wk 15 min IMT
T
12 MD and MIP, J EMG,, moreso in IMT and Rehab groups than in Rehab group alone
Harver et at"
COPD: 9 LI (5 cm H,O/L.s); 10 HI (5-35 cm H, O/L.s)
15 min, 2x/d, 8 wk
T
inspiratory training pressure, MIP, J dyspnea in HI group, no significant improvement in LI group
Belman and ShadmehrQ
COPD 9 LI (7.5-10 cm H,O); 10 HI (progressive -60-1 00 cm H,O)
15 min daily, 5 wk
f MIP, MSVC, maximal sustained work rate in both groups but greater T in HI group
"COPD=chronic obstructive pulmonary disease: EMG,,,,,=electromyogriiphic signs of diaphragm fatigue; HI=high-intensity training; IMT=inspiratory inuscle training; LI=low-intensity training; MIP=:maximal inspiratory pressure; MSVC=maximum sustained ventilatory capacity; Rehat>=pulmona~rehabilitation; 12 b,lD= 12-rn~nutewalk distance.
uses an apparatus that consists of a mouthpiece connected to a one- or two-way valve, which in tuin is attached to some sort of inspiratory threshold loading device. The subject breathes in against the threshold load (usually a weighted plunger or springloaded valve) and breathes out unimpeded. Earlier versions of the training device consisted of a weighted plunger for the threshold load,l2>"but a one-mra)!spring-loaded valve has recently been developed.lO Using the spring-loaded threshold trainer,t expiration is unloaded. During inspiration, however, a person has to breathe in hard enough to open the valve against a tightened spring. The inspiratory load is calibrated in centimeters of water and can be increased by removing the mouthpiece and tightening the spring. Greater success is apparently achieved when training at a higher threshold load. l o
ie~,~~J"-'~"*.j') although it was not measured in one study.'* The improvement in exercise tolerance in response to threshold training is a cntical finding. Earlier reports examining the effects of IRT and MSW did not consistently show an impact on exercise tolerance, compared with the exercise tolerance shown by a control group or another treatment group.
Threshold training has also been demonstrated to benefit other groups of patients not usually considered in respiratory muscle training studies. Weiner et all5 found that this type of respiratory muscle training improved inspiratory muscle force and endurance and decreased symptoms in patients with asthma. Threshold training prevented the loss of respiratory muscle force and endurance associated with high-dose steroids in patients with autoinunune diseases in one study." Patients with COPD or Threshold loading training has been patients with asthma receiving highperformed in asymptomatic individudose steroids, even delivered over als,l2those with COPD,10,1",JH~3Vho~e repeated short courses, may be suswith asthma,'; and those with cystic ceptible to steroid myopathy of the fibrosisl"(Tab. 4).All studies demonrespiratory muscles." Threshold trainstrated improved indexes of respiraing may prevent loss of respiratory tory muscle endurance (increased nluscle function and promote imendurance time at submaximal threshprovement during and following steold load or increased submaximal roid administration in individuals with chronic respiratory disease. threshold load sustained for a deterexcept for one mined tirne),1°~12~lj~16~~ study that did not measure endurance.14Exercise tolerance was shown to improve in several studPhysical Therapy / Volume 7 5 , Number 11/November 1995
Respiratoty Muscle Training as an Adjunct to Weaning Respiratory muscle endurance training Inay also be used as an adjunct to assist weaning patients from a mechanical ventilator. Investigations have used IRT and MSW to train individuals on mechanical ventilators. A few poorly controlled studies with small numbers of patients have demonstrated positive r e s u l t s 2 ~ . *(Tab. ~ ~ + 5). ~ Aldrich et altt (Tab. 5 ) examined a larger number of patients in a chronic care institution who were more stable but who were still unable to wean. After 10 to 46 days, most of the patients were either weaned totally or to nocturnal ventilation.*" Respiratory muscle training may better prepare the inspiratory muscles for the work of spontaneous breathing than traditional weaning techniques for a couple of reasons. Similar to what occurs in limb muscles, a higherintensity training load may recruit a larger pool of muscle fibers and, hence, a larger pool of fibers are trained for subsequent lower, but potentially fatiguing, loads.+iA training load may also facilitate intracellular changes in the diaphragm characteristic of endurance training such as increased mitochondria1 density, increased substrate stores of lipid and glycogen, and increased capillary den~ity.~
Table 4.
Ejects o f i%i*eshold Training
Reference
Clanton et al"
Subjects and Groups
Duration, Frequency, and Time Course of Training
Outcome
N: 4 10% MIP
3x2.5 min, 3x/wk, 10 wk
f MIP and TI, at 65% of MIP
4 50% MIP Goldstein et aI3'
COPD: 6 sham* and Rehab, 6 IMT and Rehab
10+20 min, 2x/d, 4 wk
f Ti,, on threshold trainer for IMT group, no A in MIP, both groups f 6 MD
Larson et a1.O
COPD: 12 LI (15% MIP)
15+30 min, daily, 2 mo
f MIP, TI,, at 66% of MIP, 12 MD
30 min, daily, 6 mo
f MIP, T,,, at 66% of MIP, 12 MD,
1 h, 3x/wk, 6 mo 15 min IMT
f MIP and P,peak/MIP in IMT and Ex; f TI,, on bike and 12 MD, more in IMT and Ex groups than in Ex group f MIP and f TI,, on TM
10 HI (30% MIP) Kim et aI3'
COPD: 26 sham*
4 dyspnea
41 HI (30%) Weiner et all6
COPD: 12 C, 12 IMT and Ex (15%+80% MIP), 12 Ex
Sawyer and C l a n t ~ n ' ~ CF: 10 LI (10% MIP), 10 HI (60% MIP)
30 min, daily, 10 wk
Weiner et all5
30 min, 5x/wk, 6 mo
Asthma: 15 sham*
f MIP and P, peak/MIP
J symptoms, hospitalizations, abscenteeism, and medication
15 IMT (15%+80% MIP) -
-- -
- - - ~ --
'Asterisk ('1 indicates sham trainers had a negligible load on threshold trainers, whereas LI had a small but measurable load. C=control; COPD=chronic obstructive pulmonary disease; Ex=exercise; HI=high-intensity trainers; IMT=inspiratory muscle trainers; LI=low-intensity trainers; MIP=maximal inspiratory pressure; N=asymptomatic individuals; P,,,peak/MIP=highest pressure susrained o n threshold loader expressed as a proportion of the MIP; T,,,,,=endurance time; TM=treadmill; 6 MD=6-minute walk distance; 12 MD=12-minute walk distance; Rehab=pulmonary rehabilitation; A=change.
Respiratory muscle training may facilitate weaning in those patients who fail conventional T-piece weaning, but a better understanding of the specific etiology of respiratory muscle dysfunction contributing to failed weaning is needed. Unfortunately, there are no criteria for selecting those patients who are best suited for respiratory
muscle training and which training protocol to use. If the overload is too severe, there is the potential for respiratory muscle injury to occur. Respiratory muscle injury has been shown in both animal models of respiratory ~verloa@',~'and in people with COpD,48,49
Endurance Exercise Involving the Extremities Some researchers have exanlined the benefit of endurance exercise involving the extremities such as running, swimming, or cycle ergornetry on respiratory muscle endurance (Tab. 6). These types of exercise were effective
Table 5. Efects of Inspiratoty Muscle Training in Ventilatory Failurea
Reference
Subjects and Groups
Duration, Frequency, and Time Course of Training
Type of IMT
Outcome
BeImanz3
2 COPD
15 min, 3-6x/d in ICU, daily on wards, -6 wk
MSW
Successful weaning in 11 wk, f MSVC and ET
Aldrich and K a r p e ~ ~4~ COPD CHF, other
5-15 min, 30 min, 1-2x/d, 11-24 d
IRT
Abelson and Brewer4'
1 COPD, 3 quad
15 min/d, 3-10 wk, 3-10 wk
IRT
f MIP and VC
Aldrich et a144
7 NM 20 COPD
1 3 0 min, 5x/wk, 10-46 d
IRT
f MIP and VC; 12 patients weaned totally; 5 patients
MIP and weaned 3 of 4 patients
weaned to nocturnal ventilaton
"CHF=congestive heart failure; COPD=chronic obstructive pulmonary disease: ET=exercise tolerance; ICU=intens~vecare unit; IMT=inspiratory muscle training; IRT=inspiratory resistive training; MIP=maximal inspiratory pressure; MSVC=maximum sustained ventilatory capacity; MSvV=rnaxlmum sustained voluntary ventilation; NM=neuromuscular disease; quad=quadriplegia; VC=vital capacity.
76 / 1002
Physical Therapy / Volume 75, Number 11 /November 1995
Table 6.
Effects c!fEtzdurunce Exerc~seInuok'rizg the Extremztz~~s on Respnatoiy Muscle Fz~nctzon"
Subjects and Groups
Duration, Frequency, and Time Course of Training
Robinson and Kjeldgaardso
11 N
40 min+, 3x/wk, 20 wk
Running
16% f MSVC, 14% f M W
Keens et aIz0
4 CF
1.5 hr+, daily, 4 wk
Swimming/ canoeing
57% f MSVC
Orenstein et a15'
31 CF: 21 Ex, 10 C
1 hr, 3x/wk, 3 mo
Running
50% f MSVC, f maximal work load and i/o,max
Belman and Kendregan5'
COPD: 8 U/E, 7 WE
2x20 min, 4x/wk, 6 wk
Arm and leg cycl~ng
No A in MSVC, f maximal work load in trained limbs
Ries and Moserlg
7 COPD
15-20 min, 3x!d, 6 wk
Walking
No A in MSVC, f T,,,,, on TM
Reference
Activity
Outcome
"C=control; COPD=chronic o1)structive pulmonary disease: Ex=exercise; L/E=lower-extremity cycle ergometry training; MSVC=maximu~ns~~stained ventilatory capacity: MW=maximal vol~intaryventilation; T,,,=endurance time; TM=tre;~dmill;U/E= ilpper-extremity cycle ergometry training: Volmax=m;tximal oxygen consumption: A=change: C\-=asymptomaticindividuals.
techniques of training for the respiratory muscles in younger asymptomatic individualsi0 and those with cystic but they were ineffective in two studies on older patients with COPD1T5' (Tab. 6). At least in older patients with COPD, specific respiratory muscle training is required to improve respiratory muscle endurance
A Practical Guide for Respiratory Muscle Training Although many of the specific details have not been worked out regarding
Table 7.
Effects of Endumnce Exeflcise Involving the Extf- mit ties on Chronic Ol~structivePulmonuty Diseusea
The benefits of exercise on other body systems (Tab. 7)i%hould be considType of ered when weighing the relative beneExercise Effect fit of endurance exercise involving the exTreinities versus respiratory muscle tmining in patients with chronic respiCardiovascular lncreased i/o,max ratory disease. Most studies demonRespiratory Increased tolerance of dyspnea strate an increased maximal work load Decrease in minute following a general exercise program ventilation at s~milarwork in patients with COPDi-' and those loads ~ " ' - rewith cystic f i b r ~ s i s . ~ ~ ~Several lncreased mucociliary searchers have shown improved maxiclearance mal oxygen consumption in patients Skeletal muscle lmproved oxygen extraction with COPDi3 and those with cystic Maximal work lncreased fibro~is.~' i4.55.57 In addition, several load other effects have been shown (Tab. lmproved efficiency-lower 7),5-'one of the most important being HR, VO, , or increased the facilitation of sputum expectoraanaerobic threshold tion in patients with cystic fibrosi~.~+.5~Psychological lncreased sense of For the time spent training, it may be well-being of greater benefit to patients to perActivities of Improved daily living form endurance exercise involving the extremities rather than specific inspiratory muscle training in spite of the "hIodified from Reid and ~ a r d ~ See . " this reference for complete citation of refermces lack of benefit to the respiratory mussi~pportingfactors shown. HH=heart rate, cles from a general exercise training Vo,=oxygen consumption, Vo,max=maximal program in older patients with COPD. oxygen consunlption. I'hysical Therapy / Volume 75, Number 11/ November 1995
the optimal respiratory muscle training program. there are a few guidelines that can be given to the physical therapist who wants to implement this type of training. Many patients with chronic respiratory disease may benefit from inspiratory muscle training (Tab. 8); however, it is still not known in which subgroups of patients are optimal benefits achieved. Because many other aspects of respiratory rehabilitation such as a general exercise training program have more widespread benefits,5' it would appear that inspiratory muscle training should be recommended to more motivated patients who would have time to commit to an endurance exercise program involving the extremities and an inspiratory muscle training program. An exception to this general guideline might be individuals who are at high-risk for an endurance exercise program involving the extremities, such as those with significant cardiovascular disease. For example. we received a referral for a 65-year-old man with a long-standing history of COPD combined with a more recent history of a 3-month stay in intensive care following coronary :lrtery bypass surgery. This patient was discharged home to a nlral community but continued to complain of extreine dyspnea on exertion. Because he was experiencing some cardiac arrhythmias, an unsupervised exercise program was not instituted, but instead he
1003/ 77
-
Table 8. selection Criteria foiRespii-atop Muscle Training High motivation Exercise is high risk Very dyspneic? Stable hypercapnic respiratory failure? High-dose steroids? Asthma? Cystic fibrosis?
began threshold inspiratory muscle training. Respiratory muscle training decreased complaints of dyspnea and improved patient-reported exercise tolerance. In such an individual with a high cardiovascular risk, inspiratory muscle training may reduce dyspnea and improve exercise tolerance while imposing much less stress on the cardiovascular system (Reid \XD, unpublished data, 1992). Before beginning any kind of training program including respiratory muscle training, patients should be medically stable and properly managed. Medications should be optimal, and the patient should be using oxygen if prescribed. In addition, the therapist should ensure that nutrition is optimal. Exercising an individual with poor nutrition can result in muscle catabol i ~ m j 9and , ~ loss of functionb1rather than improved performance. In order to determine the benefit of respiratory muscle training, the patient should be evaluated before and after a 6- to Sweek course of training. This evaluation should include an inspiratory muscle endurance test, an exercise tolerance test such as a 12-minute walk test or treadmill test, a measure ~ , " a measure of of d y ~ p n e a , ~ and functional a c t i v i t i e ~ . ~The ~ , ~minimum 5 equipment required would include a respiratory muscle trainer, oximeter, stopwatch, blood pressure cuff, and electrocardiographic monitor (the latter two items would be required for the walk or treadmill test). More sophisticated respiratory muscle testing systems are described elsewhere (see
article by Clanton and Diaz in this issue). The most practical, effective training device appears to be the threshold trainer.1° Although the optimal training program has not been determined, most studies have used a training duration of between 15 and 30 minutes. From what is known about endurance training of limb muscles, the frequency of training should probably be no fewer than three times per week.5 If prescribing higher frequencies of training, it might be of benefit to have patients take the weekend off to give them some variety in activities and to maximize recovery from training. Training intensity should be at an inspiratory pressure equal to or greater than 30% of the MIP.9J0J+16Recent reports have described successful outcomes at much higher training intensities of about 60% to 70% of the MIP for a 10-week13or 4-month16 training period or up to 80% of the MIP during the last 2 months of a 6-]nonth training- period."%16Training at higher intensities, however, inthe risk of respiratory fatigue and even respiratory muscle Progression of training should be slow, and allowances should be made for any exacerbation of disease or social event so that training - may . be resumed at a lower level following any prolonged lapse in training. *
Conclusion Inspiratow lnuscle training is benefit for some patient groups. The mechanism of respiratory muscle fatigue is poorly understood, and it is difficultto discern the difference between weak and fatigued muscles. It is therefore very difficult in some cases, such as weaning from a mechanical ventilator, to decide when to rest or train the respiratory muscles. The best ~rotocolsof res~iratorvmuscle training are yet to be defined. Although many training studies have been performed, the optimal intensity, contraction speed, repetition rate, and frequency still need to be determined. Further, the specific subgroups that may benefit from these techniques need to be determined, R~~~~~ studies
using targeted inspiratory resistive and threshold training in patients with COPD seem to indicate that this technique is helpful in addition to pulmonary rehabilitation. In patients with COPD, an endurance exercise program involving the extremities should be the first treatment of choice, and, in special circumstances, inspiratory muscle training may have an added benefit. Other patient groups such as those with steroid-induced myopathy, cystic fibrosis, or asthma may also benefit from inspiratory muscle training. References 1 Fishman AP. The spectrum of chronic ohstructive disease of the aiways. In: Fishman AP, ed. P ~ r l t n o t ~Diseuses rr~ rind Disorden.. New York, NY: McGraw-Hill Book Co: 1988: chap 70. 2 Roussos C. Ventilatory failure and respiratory muscles. In: Roussos C, Macklem PT, eds. The 7hora.x. New York, NY: Marcel Dekker Inc; 1985;29(pt B):chap 41. Lung Biology in Health and Disease Series. 3 Rochester DF. Respiratory muscle weakness, pattern of breathing, and CO, retention in chronic obstructive pulmonary disease. Am Rev Respir Dis. 1991;143:901-903. 4 ~ ~ lCG,l ~~~~~i~~ ~ ~limitation h ~and~,.linical exercise testing in chronic obstructive pulmonary disease. Zlin Chest Med. 1994;15:305306. 5 McArdle WD, Katch FI, Katch VL. Exercise Physiology: Energy, NLlt~tion; and Human ~e$orm%ce. 2nd ed. Philadelphia, Pa: Lea & Febiger; 1986. 6 Leith DE, Bradley M Ventilatory muscle strength and endurance training. J Appl ~hysl'ol.1976;41:508-516. 7 Reid WD, Warren CPW. Ventilatory muscle strength and endurance training in elderly subjects and patients with chronic airflow limitation: a pilot study, physiotherapS' Carl. ada. 1984;36:305-311. 8 Asher MI, Pardy RL, Coates AL. The effects of inspiratory muscle training in patients with cystic fibrosis. A m Rev Respir Dis. 1982;126: xss-ssc, -,,-,, 9 Belman MJ, Shadmehr R. Targeted resistive ventilatory muscle training in chronic obstructive pulmonary disease. J Appl Physiol 1988; 65:2726-2735. 10 Larson JL, Kim h1J. Sharp JT, Larson DA. Inspiratory muscle training with a pressure threshold breathing device in patients with chronic obstn~ctivepulmonary disease. A m Rer, Respir Dis. 1988;138:689-696. 11 Harver A. Mahler DA. Daubensoeck ,A. Targeted inspiratory muscle tralning improves respiratory muscle function and reduces dyspnea in patients with chron~cobstructive pulrnonary disease. A n n Intern Med 1989;lll: 117-1 24 12 Clanton TL. Dixon GF, Drake J, Gadek JE Inspiratory muscle conditioning using a
.
-
Physical Therapy /Volume 75, Number 11 /November 1995
threshold loading deisice. Chest. 1985;87:6266. 13 Dekhuijzen PNR, Folgering HTM, van Herwaarden CLA. Target-flow inspiratory muscle training during pulmonary rehabilitation in patients with COPD. Chest. 1991;99:128-133. 14 Samyer EH. Clanton TL. Improved pulmonary function and exercise tolerance with inspiratory muscle conditioning in children with cystic fibrosis. Chest. 1993;104:1490-1497. 15 Weiner P, Azgad Y, Ganam R. Weiner M. Inspiratory muscle training in patients with bronchial asthma. Chest. 1992;102:1357-1361. 16 Weiner P, Azgad Y, Ganam R. Inspiratory muscle training combined with general exercise reconditioning in patients with COPD. Chest. 1992;102:1351-1356. 17 Estennt: M, De Troyer A. Cough in tetraplegic subjects: an active process. A n n Intern Med. 1990;112:22-28. 18 Rochester DF. Respiratory muscles and ventilatory failure: 1993 perspective. A m JMed Sci 1993;305:394-402, 19 Ries AL. Moser KM. Comparison of isocapnic hypementilation and walking exercise tratning at home in pulmonary rehabilitation. Chest. 1986;90:285-289. 20 Keens TG, Krastins IRB, Wannamaker EM, et al. Ventilatory muscle endurance training in normal subjects and patients with cystic fibrosis. Am Re!)Respir Dis. 1977;116:853-860. 21 Helman MJ, Mittman C. Ventilatory muscle training improves exercise capacity in chronic obstructive pulmonary disease patients. Am Rev Respir Dis. 1980:121:273-280. 22 Levine S, Weiser P, Gillen J. Evaluation of a ventilatory muscle endurance training program in rehabilitation of patients with chronic obstructive pulmonary disease. Am Rn! Respir Dis. 1986;133:400-406. 23 Belman MJ. Respiratory failure treated by ventilatory muscle training (VMT): a report of two cases. Eur J Respir Dis. 1981;62:391-395. 24 Astrand PO, Ryhming I. A nomogram for calculation of aerobic capacity (physical fitness) from pulse rate during submaximal work. JAppI Physiol. 1954;7:218. 25 Reid WD, Loveridge BM. Ventilatory muscle endurance training in patients with chronic obstructive pulmonary disease. Physiotherapy Canada. 1983;35197-205. 26 Andersen JB, Dragsted L, Kann T, et al. Resistive breathing training in severe chronic obstructive pulmonary disease. Scandinavian .lotlrnal of Respiratiotz. 1979;60:151-156. 27 Helman MJ, Thomas SG. Lewis MI. Resistive breathing training in patients with obstructive pulmonary disease. Chest. 1986;90: 662-669. 28 Guyatt G, Keller J , Singer J, et al. Controlled trial of respiratory tnuscle training in chronic airflow limitation. Thorax. 1992;47: 598-602. 29 Larson M, Kitn MJ. Respiratory muscle training with the incentive spirometer re5istive breathing device. Heart Lung. 1984;15341345. 30 Jones DT, Thomson RJ, Sears MR. Physical exercise and resistive breathing training in severe chronic airways obstruction: Are they effective? EurJ Respir Dis. 1985:67:159-166.
31 Noseda A, Carpiaus JP. Vandeput W, et al. Resistive inspiratory muscle training and exercise performance in COPD patients: a comparative study with conventional breathing retraining. Respir Physiol. 1987;23:457-463. 32 Richardson J, Dunn L, Pardy R. Inspiratory resistive endurance training in patients with chronic obstructive pulmonary disease: a pilot study. Physiotherapy Canada. 1989;41:85-92. 33 Secher NH, Madsen F, Bjerre-Jepsen K, er al. Exercise and the breathless bronchitic. Lancet. 1980;11(8199):858-859. 34 Sonne LJ, Davis JA. Increased exercise performance in patients with severe COPD following inspiratory resistive training. Chest. 1982;81:436-439. 35 Pardy RL, Rivington RN, Despas PJ, Macklem PT. The effects of inspiratory muscle training on exercise performance in chronic airflow limitation. Am Rev Respir Dis. 1981; 123(pt 1):426-433. 36 Pardy RL, Rivington N, Despas PJ, Macklem PT. Inspiratory muscle training compared with physiotherapy in patients with chronic airflow limitation. Am Rev Respir Dis. 1981;123(pt 1):421-425. 37 Belman blJ3Skadtnehr R. A target feedback device for ventilatory muscle training. .I Clin Monit. 1991;7:42-48. 38 Goldstein R, De Rosie J, Long S, et al. Applicability of a threshold loading device for inspiratory muscle testing and training in patients with COPD. Chest. 1989;96:564-571 39 Kim MJ, Larson JL, Covey MK, et al. Inspiratory muscle training in patients with chronic obstructive pulmonary disease. N u n Res. 1993;42:356-362, 40 Weiner P, Azgad Y, Weiner M. Inspiratory muscle training during treatment with corticosteroids in humans. A m J Respir Crit Care Med. 1994;149(pt 4):A273. 41 Gallagher CG. Respiratory steroid myopathy. Av~JRespirCrit Care Med. 1994;150:4-6. 42 Abelson H, Brewer K. lnspiratory muscle training in mechanically ventilated patients. Physiotherap,) Canada. 1987;39:305-307. 43 Aldrich TK, Karpel JP. Inspiratory muscle resistive training in respiratory failure. A m Rev Respir Dis. 1985;131:461-462. 44 Aldrich TK, Karpel JP, Uhrlass RM, et al. Weaning from mechanical ventilation: adjunctive use of inspiratory resistive training. Crit Caw Med. 1989:17:143-147. 45 Lieber RL. Skeletal Muscle Structure and Functiotz: Implicatior~sfor Rehabilitation arrd Sports Medicine. Baltimore. Md: Williams & Wilkins; 1986: chap 4. 46 Reid WD, Huang J, Bryson S. et al. Diaphragm injury and myofibrillar structure induced by resistive loading. J Appl P/qsiol. 1994;76:176-184. 47 Reid WD. Time course of diaphragm injury in tracheal banded rats. Clin Invest nird. 1993;16(4):~121. 48 Hards JM, Reid WD, Pardy RL, Pare PD. Respiratory muscle morphometry: correlation with lung function and nutrition. Chest. 1990; 97:1037-1044. 49 Silver MM, Smith SR. Diaphragm contraction bancl necrosis in a perinatal and infantile
Physical Therapy / Volume 75, Number 11/ November 1995
autopsy population. Hum Pathol. 1992;23: 817-827. 50 Robinson EP, Kjeldgaard JM Improvement in ventilatory tnuscle function with running. J Appl Pbysiol. 1982;52:1400-1406. 51 Orenstein DM, Franklin BA, Doershuk CF. et al. Exercise conditioning and cardiopulmonary fitness in cystic fil>rosis:the effects of a three-month supenised running program. Chest. 1981:80:392-398. 52 Belman MJ, Kendregan BA. Exercise training hils to increase skeletal muscle enzymes in patients with chronic obstructive pulmonary disease. Am Rev Respir Dis. 1986;123: 256-261. 53 Reid WD. Pardy RL. Long-term care of patients with chronic bronchitis and emphysema. In: Cherniak N, ed. Chronic Obstn~cti~~e Pulmonary Disease. Philadelphia, Pa: WB Saunders Co; 1991: chap 64. 54 Salh W, Bilton D, Dodd M. Webb AK. Effect of exercise and physiotherapy in aiding sputum expectoration in adults with cystic fibrosis. Thorax. 1989;44:1006-1008. 55 Heijerman HGM, Bakker W, Sterk PJ, Dijkman H. Oxygen-assisted exercise training in adult cystic fibrosis patients with pulmonary limitation to exercise. IntJ Rehahil Res. 1991; 14:lOl-115. 56 Andreasson B, Jonson B, Kornfiilt R, et :I]. Long-term effects of physical exercise on working capacity and pulrnonary function in cystic fibrosis. Acta Paediatr Scand. 1987; 76: 70-75. 57 de Jong \V, Grevink RG, Roorda RJ, et al. Effect of a home exercise training program in patients with cystic fibrosis. Chest. 1994;105: 463-468. 58 Blomquist M, Freyschuss U, Wiman L-G, Strandvik B. Physical activity and self treatment in cystic fibrosis. Arch Dis Child. 1986; 61:362-367. 59 Brouns F. Nutritional aspects of health and performance at lowland and altitude. Int J Sports Med. 1992;13(suppl):S100-S106. 60 Kayser B. Nutrition and energetics of exercise at altitude: theory and possible practical implications. Sports Med. 1994:17:309-323. 61 Lewis MI, Belman MJ. Nutrition and the respiratory muscles. Clin Chest Med. 1988:9: 337-348. 62 Borg GAV. Psychophysical basis of perceived exertion. Med Sci Sports Dcerc. 1982;14: 377-381. 63 Jones NL, Berman LB. Bartkirwicz PD, Oldridge NB. Chronic obstructive respiratory disorders. In: Skinner JS, ed. Exercise Testing and Exercise Plwcriptiot~for Special Cases: Theoretical Basis and Clitrical Application. Philadelphia, Pa: Lea & Febiger; 1987: chap 11. 64 Bergner M, Bobbttt RA, Carter WB, Gilson BS. The sickness impact profile: a development and final rev~sionof a health status measure. Med Care. 1981;19:787-805 65 McHorney CA, Ware JE Jr, Lu JF, Sherbourne CD. The MOS 36-item short-form health survey (SF-36), 111: Tests of data quality, scaling assumptions, and reliability across diverse patient groups. Med Care. 1994;32:4066.
