一个bstract
Expiratory muscle strength is a determinant of cough function. Mouth pressures during a maximal static expiratory effort (PE,max) are dependent on patient motivation and technique and low values are therefore difficult to interpret. This study hypothesized that a short, sharp and maximal expiration through a narrow aperture, a “whistle”, might provide a complementary test of expiratory muscle strength.
To obtain a maximal whistle, subjects (27 healthy volunteers and 10 patients with amyotrophic lateral sclerosis) were asked to perform a short, sharp blow as hard as possible, from total lung capacity, through a reversed paediatric inhaler whistle, connected to a flange-type mouthpiece.
In both healthy subjects and patients, whistle mouth pressure (Pmo,W) was closely related to the pressure measured in the oesophagus and stomach during the same manoeuvre. In healthy subjects,Pmo,WandPE,maxcorrelated with wide limits of agreement, althoughPmo,Wvalues were significantly higher thanPE,max(131±31 cmH2Oversus101±27 cmH2O, p<0.0001). In patients, it was also found thatPmo,WandPE,max价值观密切相关(r = 0.937, p < 0.0001)。In healthy subjects, the intraclass correlation coefficient and the variation coefficient forPmo,W重复测量were respectively 0.88 and 7.0%. HoweverPmo,WandPE,maxwere always smaller than the gastric pressure generated by a maximal cough.
It is concluded that mouth whistle pressure, a noninvasive, reproducible and simple test, provides a reliable measure of expiratory muscle strength in healthy subjects that is acceptable to patients and can be used in a complementary fashion to maximal static expiratory effort.
Chest infection is a cause of serious morbidity and mortality in patients with respiratory and neuromuscular disease. Cough is considered to protect against chest infection and it has recently been shown that expiratory muscle strength is an important determinant of an effective cough1. Techniques to evaluate expiratory muscle strength are therefore of interest.
Mouth pressures during maximal static expiratory (PE,max) efforts are widely used as a noninvasive test to assess expiratory muscle strength2. When high values are found, muscle weakness is excluded3. However, the normal range forPE,maxis wide2,4, reflecting both the biological variability of respiratory muscle strength and also the difficulty some subjects have in performing the manoeuvre maximally. In the assessment of inspiratory muscle strength it has been shown that the use of a manoeuvre complementary to the static effort, such as the maximal sniff, can exclude inspiratory muscle weakness5,6. Indeed sniffing is a natural manoeuvre which is more easily performed than static efforts, and by measuring the upper airway pressure during a maximal sniff, inspiratory muscle strength may now be accurately measured noninvasively7in a variety of clinical settings8.
It was therefore reasoned that an additional test of expiratory muscle strength that was noninvasive, using a natural, uncomplicated manoeuvre, could be clinically useful. The main muscles of expiration are the abdominal muscles and one approach to measuring their strength is to record gastric pressure during a maximal cough1or following magnetic nerve stimulation posteriorly at the level of the 10th thoracic intervertebral space9. However, both these tests require passage of a gastric balloon catheter. The present authors hypothesized that a test using pressure measured at the mouth during a short, sharp and maximal expiration through a narrow aperture (a “whistle”) would be a relatively natural manoeuvre that might be a useful additional noninvasive test of expiratory muscle strength. The main purpose of the study was to ascertain in healthy subjects, and in patients with respiratory muscle weakness, whether the measurement of mouth pressure during a whistle manoeuvre (Pmo,W) is reproducible, and whether mouth whistle was pressure closely reflects oesophageal and gastric pressures. In addition, the study aimed to compare mouth, oesophageal and gastric pressures during whistle andPE,maxmanoeuvres, as well as to compare whistle mouth pressure to gastric pressure, during a maximum cough.
Methods
Twenty-seven healthy volunteers (10 male) and 10 patients (all male) with amyotrophic lateral sclerosis (ALS) were studied. The severity of ALS was assessed by the Norris limb and bulbar scales10and by the ALS functional rate scale11. The study was approved by the hospital ethics committee and all subjects gave their informed consent.
Spirometry was measured by a horizontal bellows spirometer (Vitalograph Ltd, Buckingham, UK) and vital capacity (VC), forced expiratory volume in one second (FEV1) and FEV1/VC values were recorded. Predicted values of VC and FEV1were obtained from regression equations by Quanjeret al.12.
In order to obtain a maximal whistle, subjects were asked to perform a short, sharp blow as hard as possible from total lung capacity (TLC) through a reversed paediatric inhaler whistle (Astra Pharmaceuticals Ltd, Herts, UK) connected to a flange-type mouthpiece gripped between the teeth (fig. 1⇓). Subjects performed whistles without a noseclip. Additionally, healthy subjects were asked to perform maximum whistles while holding their cheeks. Whistles suitable for analysis had to present pressure tracings showing a sharp peak and a duration of <500 ms. This was usually achieved after 3–6 whistle manoeuvres. Healthy subjects were also asked to perform whistles of varying intensities. Repeatability of whistle mouth pressure (Pmo,W) in healthy subjects was assessed by repeating measurements on two separate days. The whistle device had a linear relationship between resistance and flow across the range 10–100 L·min−1. The mean (range) value for peak flow through the device for healthy subjects was 92 L·min−1(78 - 109 L·分钟−1). The resistance over this range was 29.3–44.4 cmH2O·L−1·s.
![Fig. 1.—](http://www.qdcxjkg.com/content/erj/17/4/688/F1.medium.gif)
The whistle device consists of a reversed paediatric inhaler whistle connected to a conventional mouthpiece.
PE,maxand maximal static inspiratory effort (PI,max) were performed against a valve based on that used by Black and Hyatt4which could be closed by turning a tap. A leak 3.7 cm in length and 0.2 cm in diameter was placed 3 cm from the mouthpiece to reduce discomfort and generation of high buccal pressures13. A conventional flanged mouthpiece and noseclip were used.PE,maxwas measured from TLC andPI,maxfrom residual volume. The highest recorded pressures maintained for one second were used for analysis. Patients attempted to prevent perioral leak by holding their lips firmly around the mouthpiece with both hands. Day-to-day reproducibility ofPE,maxwas assessed in the healthy subjects.
Gastric (Pga), oesophageal (Poes) and transdiaphragmatic (Pdi) pressures were measured using a pair of commercially available latex balloon catheters (PK Morgan, Rainham, Kent, UK) 110 cm in length, passed through the nose and positioned in the stomach and oesophagus in the conventional manner14. The oesophageal balloon contained 0.5 mL air, the gastric balloon 2 mL.
Pgaduring a maximum voluntary cough effort, was also measured in healthy subjects and patients. This manoeuvre was performed in a seated position without a noseclip. Invariably, subjects inhaled deeply before coughing, but no specific instructions were given regarding the magnitude of inspiration before cough. Repeated efforts were performed until no further increase inPgawas obtained (usually achieved after 3–6 coughs).
The whistle device, the mouth piece and the balloon catheters were connected to differential pressure transducers (Validyne MP45-1, Validyne, Northridge, CA, USA), carrier amplifiers (PK Morgan), a 12 bit NB-MIO-16 analogue-digital board (National Instruments, Austin, TX, USA) and a Macintosh Quadra Centris 650 personal computer (Apple Computer Inc., Cupertino, CA, USA) running LabviewTMsoftware (National Instruments).Pdiwas obtained on-line, by subtraction ofPoesfromPga. A minimum sampling frequency of 100 Hz was used. Peak pressures were taken as those measured from the baseline at relaxed end-expiratory lung volume, at the peak pressure, obtained.
Healthy subjects and patients were studied in the seated position and pressures were displayed on a computer screen in front of the subject to provide visual feedback15. Subjects were strongly encouraged to make maximal efforts.
数据了mean±sd. VC and FEV1values were expressed as per cent of predicted value, FEV1/VC is expressed as per cent. Differences in numerical data were examined by means of paired t-tests. The agreement between measures was assessed by the method of differences against the means according to Bland and Altman16. The relationship between measures was assessed by Pearson's correlation coefficient (r) and linear regression analysis. The repeatability of measures was expressed as intraclass correlation coefficient (rI)17and assessed by calculating the coefficient of variation. A p-value <0.05 was considered statistically significant.
Results
Healthy subjects
Personal details were: age, 32±6 yrs; height, 170±10 cm; weight, 68±13 kg; and body mass index, 24±4 kg·m−2. Spirometric values were: VC, 104±13% pred; FEV1, 104±14% pred; FEV1/VC, 83±7%.
In the 27 healthy subjects,Pmo,WandPE,maxvalues were 131±31 cmH2O (range 77–202 cmH2O) and 101± 27 cmH2O (range 44–155 cmH2O), respectively (p< 0.0001). The 95% confidence intervals of the mean were 119–143 cmH2O forPmo,Wand 90–111 cmH2O forPE,max. In the same group of subjects,Pmo,Wdid not differ fromPmo,Wobtained while holding cheeks (139±35 cmH2O, range 72–217 cmH2O). The ratioPmo,W/PE,maxwas 1.3 (range 0.9–2.1) and in 24 out of 27 subjects, was >1. There was a significant correlation betweenPmo,WandPE,max(r=0.674, p=0.0001) (fig. 2⇓). The bias betweenPmo,WandPE,maxwas 30 cmH2O, withPmo,Wtending to be numerically greater thanPE,max. The limits of agreement ranged from -17–77 cmH2O (fig. 2⇓). The rIand the variation coefficient forPmo,W重复测量were 0.888 and 7.0%, respectively. In the same group of subjects, rIand variation coefficient forPE,maxwere 0.790 and 10.2%, respectively.
口笛压力之间的关系(Pmo,W) and maximum expiratory pressure (PE,max) in 27 healthy subjects. The continuous line is the line of identity. r=0.67, p=0.0001. b) Plot of the difference betweenPmo,WandPE,maxagainst the mean ofPmo,WandPE,maxin 27 healthy subjects. The bias,i.e.the mean of the difference betweenPmo,WandPE,max(continuous line), was 30 cmH2O; the limits of agreement,i.e.bias±2sd (interrupted lines), were -17–77 cmH2O.
In the 12 subjects in whomPoes,PgaandPdiwere measured during both the whistle andPE,maxmanoeuvres, values were respectively:Pmo,W139±27 cmH2O andPE,max109±27 cmH2O (p<0.02),Poes,W129±20 cmH2O andPoes,PE,max 109±24 cmH2O (p<0.05),Pga,W163±36 cmH2O andPga,PE,max 160±60 cmH2O, andPdi,W34±29 cmH2O andPdi,PE,max 50±51 cmH2O. The ratios ofPmo,W/Poes,WandPmo,W/Pga,Wwere 1.1 (range 0.95–1.23) and 0.88 (0.54–1.1), respectively. Biases betweenPmo,WandPoes,W(the mean of the difference between these two variables) and betweenPmo,WandPga,Wwere 9 cmH2O and -26 cmH2O and limits of agreement (bias±2sd) ranged from -17–35 cmH2O and from -83–31 cmH2O (fig. 3⇓).
a) Plot of the difference between mouth whistle pressure (Pmo,W) and gastric whistle pressure (Pga,W) against the mean ofPmo,WandPga,Win 12 healthy subjects. The bias and limits of agreement were -26 cmH2O and -83–31 cmH2O, respectively. b) Plot of the difference betweenPmo,Wand oesophageal whistle pressure (Poes,W) against the mean ofPmo,WandPoes,Win 12 healthy subjects. The bias and limits of agreement were 9 cmH2O and -17–35 cmH2O, respectively. c) Plot of the difference betweenPmo,Wand maximum expiratory pressure (PE,max) against the mean ofPmo,WandPE,maxin 10 amyotrophic lateral sclerosis (ALS) patients. The bias and limits of agreement were 7 cmH2O and -15–29 cmH2O, respectively. d) Plot of the difference betweenPmo,WandPga,Wagainst the mean ofPmo,WandPga,Win 10 ALS patients. The bias and limits of agreement were -5 cmH2O and -19–9 cmH2O, respectively. e) Plot of the difference betweenPmo,WandPoes,Wagainst the mean ofPmo,WandPoes,Win 10 ALS patients. The bias and limits of agreement were 3 cmH2O and -10–16 cmH2O, respectively.
In the same group of subjects, the mean value of coughPgawas 201±57 cmH2O (p<0.01versusPmo,WandPE,max) and the 95% confidence intervals of the mean were 165–238 cmH2O. The ratios ofPmo,W/coughPgaandPE,max/coughPgawere 0.73 (range 0.40–1.23) and 0.57 (0.35–0.92). Biases betweenPmo,Wand coughPgaand betweenPE,maxand coughPgawere -63 cmH2O and -90 cmH2O, respectively and limits of agreement ranged -167–41 cmH2O and -193–13 cmH2O, respectively (fig. 4⇓). A typical example of the pressures during whistle,PE,maxand maximal cough manoeuvres is shown in figure 5⇓.
a) Plot of the difference between mouth whistle pressure (Pmo,W) and gastric pressure during cough manoeuvre (coughPga) against the mean ofPmo,Wand coughPgain 12 healthy subjects. The bias and limits of agreement were -63 cmH2O and -167–41 cmH2O, respectively. b) Plot of the difference between maximum expiratory pressure (PE,max) and coughPgaagainst the mean ofPE,maxand coughPgain 12 healthy subjects. The bias and limits of agreement were -90 cmH2O and -193–13 cmH2O, respectively. c) Plot of the difference betweenPmo,Wand coughPgaagainst the mean ofPmo,Wand coughPgain 10 amyotrophic lateral sclerosis (ALS) patients. The bias and limits of agreement were -16 cmH2O and -75–43 cmH2O, respectively. d) Plot of the difference betweenPE,maxand coughPgaagainst the mean ofPE,maxand coughPgain 10 ALS patients. The bias and limits of agreement were -23 cmH2O and -91-45 cmH2O, respectively. e) Relationship betweenPmo,Wand coughPgain 10 ALS patients. The continuous line is the line of identity. r=0.67; p=0.03.
Pressures produced by: a) maximal whistle; b) maximal cough; and c) maximum expiratory pressure (PE,max) manoeuvres by a healthy subject. —: mouth pressure; – – – : oesophageal pressure; - - - : gastric pressure; — -: transdiaphragmatic pressure.
In the 8 subjects, in whomPmo,W,Poes,WandPga,Wvalues were compared during whistles of variable intensity,Pmo,W,Poes,WandPga,Wranged 7–222 cmH2O, 4–161 cmH2O and 9–235 cmH2O, respectively. There was a significant correlation betweenPmo,WandPoes,W(r=0.929, p<0.0001) and betweenPmo,WandPga,Wvalues (r=0.936, p<0.0001) (table 1⇓). Regression analysis showed thatPmo,W=5.49+1.1Pga,WandPmo,W=7.27+0.8Poes,W.
Values of mouth whistle pressure (Pmo,W), oesophagus whistle pressure (Poes,W), and gastric whistle pressure (Pga,W) during whistles ranging from minimal to maximal intensity performed by 8 healthy subjects
Patients
Patients had ALS of varying severity. The mean Norris limb and bulbar scales were 28±14 (range 9–50) and 35±6 (range 21–39), respectively. The mean ALS functional rating scale was 25±16 (range 13–32). Their personal details were: age, 61±5 yrs; height, 173± 10 cm; weight, 73±12 kg; and body mass index, 24.4±3.7 kg·m−2. Spirometric values were: VC, 78±24 %pred; FEV1, 76±32%pred; FEV1/VC, 80±7%.PI,maxvalues were 56±28 cmH2O (range 15–104 cmH2O).
The mean values ofPmo,WandPE,maxwere 69± 32 cmH2O (range 17–128 cmH2O) and 62±30 cmH2O (range 11–116 cmH2O), respectively. The 95% confidence intervals of the mean were 46–92 cmH2O forPmo,Wand 41–84 cmH2O forPE,max. The ratioPmo,W/PE,maxwas 1.17 (0.87–1.55). There was a significant correlation betweenPmo,WandPE,max(r=0.937, p< 0.0001). The bias betweenPmo,WandPE,maxwas 7 cmH2O and the limits of agreement ranged -15–29 cmH2O (fig. 3⇑).
The meanPoes,Pga, andPdivalues during both whistle andPE,maxmanoeuvres were 66±32 cmH2O and 63±29 cmH2O, 74±37 cmH2O and 56±33 cmH2O (p<0.02), and 8±7 cmH2O and -7±10 cmH2O (p<0.002), respectively. The ratios ofPmo,W/Poes,WandPmo,W/Pga,Wwere 1.08 (range 0.82–1.31) and 1.17 (range 0.87–1.55). Biases betweenPmo,WandPoes,Wand betweenPmo,WandPga,Wwere 3 cmH2O and -5 cmH2O, respectively and limits of agreement ranged -10–16 cmH2O and -19–9 cmH2O (fig. 3⇑). There was a significant correlation betweenPmo,WandPoes,W(r=0.980, p<0.0001) and betweenPmo,WandPga,Wvalues (r=0.990, p<0.0001). Regression analysis showed thatPmo,W=-5.33+1.1Pga,WandPmo,W=-1.78+0.9Poes,W.
The mean value of coughPgawas 85±39 cmH2O (p<0.05versusPE,max) and the 95% confidence intervals of the mean were 57–112 cmH2O. Ratios ofPmo,W/coughPgaandPE,max/coughPgawere 0.88 (range 0.50–1.39) and 0.78 (0.44–1.36), respectively. Biases betweenPmo,Wand coughPgaand betweenPE,maxand coughPgawere -16 cmH2O and -23 cmH2O, respectively, and limits of agreement ranged -75–43 cmH2O and -91–45 cmH2O, respectively (fig. 4⇑). There was a significant correlation betweenPmo,Wand coughPga(r=0.67, p<0.05).
Discussion
The main finding of this study was that pressure measured at the mouth during a short sharp whistle has a close relationship with the pressure measured in the oesophagus and stomach during the same manoeuvre. This confirms that this measurement (Pmo,W) is a valid reflection of expiratory muscle strength. The studies, conducted in normal subjects and patients with expiratory muscle weakness, show that the limits of agreement with thePE,maxare wide;i.e. high values ofPmo,Wcould be obtained whenPE,maxwas low and, less often, high values ofPE,maxwere observed whenPmo,Wwas low. This suggests thatPmo,WandPE,maxare complementary tests for the noninvasive evaluation of expiratory muscle strength. However, when compared to the gastric pressure during maximal cough, bothPmo,WandPE,maxunderestimate expiratory muscle strength. Further discussion of the significance of the findings follows a critique of the method.
Critique of the method
Do mouth measurements reflect expiratory muscle strength?
The aim of the study was to develop a test which reflected abdominal muscle strength, since these muscles are the main muscles of active expiration and are an important determinant of cough function. In the present study,Pgawas almost invariably greater thanPoesduring bothPmo,WandPE,maxindicating that the abdominal muscles are the driving force in both manoeuvres. In healthy subjects, for whomPoes,PgaandPdiwere measured during both manoeuvres,Pgawas similar for both manoeuvres, thoughPoeswas different, resulting in higherPdivalues withPE,maxcompared toPmo,W. This suggests thatPmo,Wmay be a more accurate reflection of abdominal muscle strength thanPE,max.
However, for the group as a whole,Pgawas incompletely transmitted from the abdomen to the chest; thusPoeswas 79% and 68% ofPgaduring whistle andPE,maxmanoeuvres, respectively. The reduced transmission of gastric pressure could be the result of diaphragm activation and the “inspiratory” action of the abdominal muscle on the lower rib cage19,20. As further confirmation thatPmo,Wclosely reflects bothPoes,WandPga,W, a strong correlation betweenPmo,WandPga,Wand betweenPmo,WandPoes,Wwas found in healthy subjects over a wide range of pressures obtained during whistles of different intensity. This predicts that thePmo,W在患者呼气测试仍将有效muscle weakness, a prediction supported by the data from ALS patients shown in figure 3⇑. Most importantly, it was found that, in patients with ALS of varying severity,Pmo,Wvalues strongly correlated withPga,W.
Dynamic nature of the manoeuvre
Unlike thePE,maxtest, which is based on a static manoeuvre, the whistle test is based on a dynamic one. With dynamic tests, concern can arise because airflow can render the manoeuvre not truly isovolumic. For the sniff this tendency is minimized because the nose acts as a Starling resistor, so that nasal flow is reduced, largely independent of driving pressure21. For the whistle, ourin vitroassessment showed that flow increased with driving pressure and this might have resulted inPmo,Wbeing lower thanPE,max; this was not so, indicating that the volume expired before peak pressure is not sufficient to importantly detract from the value of the test. This is because the whistle orifice acts as a resistor, substantially reducing expiratory flow. In this regard, the mean value we measured in healthy subjects for peak flow through the device, was 92 L·min−1, approximately 6–8 times lower than their peak expiratory flow rate.
Recoil pressures
PE,maxis normally measured at TLC because subjects find it easier to maximize expiratory efforts at high volumes. In this study the whistle test manoeuvre was also performed at TLC and, at this lung volume, the pressure measured reflected both the pressure developed by the expiratory muscles and the passive elastic recoil pressure of the respiratory system. Specifically, at TLC the passive elastic recoil pressure can add up to 40 cmH2O, equal to the pressure generated by the expiratory muscles22. However the whistle is a dynamic manoeuvre and recent data obtained using the peak expiratory flow23suggest the possibility that the recoil force generated by the chest wall might be greater in this situation than after the static manoeuvre. Whilst this might contribute toPmo,Wbeing higher thanPE,max, it does not explain the wide limits of agreement and therefore does not alter our conclusion thatPmo,Wcould be of value as a complementary test of expiratory muscle strength.
Facial muscles
Conceptually, the facial muscles might contribute toPmo,W, although the orifice of the whistle should serve the same function as the mouth leak proposed by Rinqvist13. Consistent with this, the present study found no significant differences betweenPmo,Wmeasurements taken with or without cheek support and it is therefore concluded that this is not a matter of practical clinical importance.
Significance of the findings
In healthy subjects, it was found thatPmo,WandPE,maxvalues correlated with wide limits of agreement, althoughPmo,Wvalues were significantly higher thanPE,maxand in all but three subjects thePmo,W/PE,maxratio was >1. In ALS patients, it was also found thatPmo,WandPE,maxvalues were closely related.Pmo,Wmean values were numerically, but not statistically significantly, higher than those ofPE,max, and thePmo,W/PE,maxratio was >1 in seven of the 10 patients.
一个lthough thePE,maxmanoeuvre is not complicated, it is not one with which many subjects will be familiar on a daily basis and requires full cooperation from subjects. In contrast, the whistle manoeuvre may be more natural and has the advantage of audible feedback. LowPE,maxvalues can occur even in healthy subjects, perhaps due to a lack of motivation or poor technique and thus may not indicate reduced expiratory muscle strength. PredictedPE,maxvalues are readily available for adults, the elderly, and children2,24but the normal ranges are wide, making it difficult to accurately identify weakness. In the present study, the whistle manoeuvre was easily performed, with minimal instruction, and was well accepted both by healthy subjects and ALS patients. The high mouth pressures achieved and the relatively high lower limits suggest that thePmo,Wcould be a clinically useful, additional method for assessing expiratory muscle strength. The day to day reproducibility ofPmo,Wwas good, suggesting the test could also be useful for serial measurements.
The ALS patients had variable severity of disease; some had severe respiratory muscle weakness whereas others had normal strength. In the patients, as in healthy subjects, the whistle manoeuvre was found to generate gastric, oesophageal and mouth pressures that were higher than those generated atPE,max. In particular,Pgavalues during whistle were significantly higher than those duringPE,max,这表明策略可以bett呢喃er recruit abdominal muscle contraction thanPE,max. Because of the small sample size, bulbar and nonbulbar patients were not specifically compared; clearly a theoretical concern could be that bulbar patients do not achieve satisfactory transmission of pleural pressure to the mouth during a whistle.
Interestingly, in ALS patients,Poesvalues were less thanPgavalues during whistle, but were higher thanPgavalues duringPE,max. This might suggest that the rib cage expiratory muscles play a different role during the two manoeuvres with a greater involvement during thePE,max. Alternatively, one could hypothesize that the process of ALS leads to compensatory hypertrophy or recruitment of muscles not yet affected by the disease as suggested by Attaliet al.25.
Pmo,WandPE,maxvalues were significantly lower than corresponding coughPgavalues, both in healthy subjects and in ALS patients. Additionally, gastric pressure during whistle andPE,maxmanoeuvres was numerically lower than coughPga. The present data confirm the results of a previous paper1that showed that cough is the most physiological expiratory manoeuvre and that coughPgais the gold standard for measuring pressure caused by abdominal muscle contraction. However, it was also observed that the bias and the limits of agreement betweenPmo,Wand coughPgawere respectively smaller and narrower than those betweenPE,maxand coughPga, both in patients and healthy subjects. Additionally, in ALS patients,Pmo,Wvalues did not significantly differ and were strictly related to coughPga. Lastly, the shape of the pressure tracings recorded during the whistle manoeuvre were very similar to those during cough (fig. 5⇑). Considered together, these findings suggest that whistle is a manoeuvre physiologically closer to cough thanPE,max.
总之,本研究表明,在两种healthy subjects and in amyotrophic lateral sclerosis patients, mouth whistle pressure is an accurate reflection of expiratory muscle strength. The limits of agreement between mouth whistle pressure and maximum expiratory pressure were wide, suggesting a role for mouth whistle pressure as an additional method for the evaluation of expiratory muscle strength, for use in both in the physiology laboratory and in clinical settings.
- ReceivedJune 19, 2000.
- 一个cceptedNovember 13, 2000.
- © ERS Journals Ltd