Results: In our study mean PImax was 59.8951c m +24.49023, with male and female values were 66.7600 + 24.48717cm and 50.6900 +21.50713 cm respectively. Mean PEmax was 67.3636 c m+23.63529, with male and female values were 75.8012+23.27025 cm and 56.0496+ 19.132337cm respectively. Mean MVV was 97.6900 L/min+31.04196 with male and female were 115.6236+24.93948 and 73.6427+20.34229 respectively.
Conclusion: In our study PImax, PEmax and MVV values were lower in females than males. It had significant positive or negative correlation with various anthropometric, physiological and spirometry parameters. The results of this study can be used to predict respiratory muscle strength in healthy adults, which can be used for required assessment of respiratory function and also aid in the planning of treatment and rehabilitation.
Key words: Maximal Respiratory Static Pressure (MRP); PImax(MIP); PEmax(MEP); Maximal Voluntary Ventilation (MVV); RM; Total Lung Capacity (TLC); Residual Volume (RV);
• Spirometry detected a pattern of restriction: reduced forced expiratory volume in one second, reduced forced vital capacity, normal FEV1/FVC ratio, and reduced total lung capacity and respiratory muscle weakness is in the differential diagnosis.
• Spirometry detected a low vital capacity of unknown etiology and respiratory muscle weakness is in the differential diagnosis.
• Spirometry detected a low maximal voluntary ventilation maneuver of unknown etiology and respiratory muscle weakness is in the differential diagnosis.
• Evaluation of whether known respiratory muscle weakness has improved, remained stable, or worsened.
• To determine whether there is an increased risk of incident mobility disability in older individuals, hospitalizations and death in patients with COPD, mortality in patients with heart failure.
• pressure and Maximal Voluntary Ventilation.
• To look for a co-relation between maximal respiratory static pressure and anthropometric parameters in normal healthy adults.
• To study the co-relation between maximal respiratory static pressure and spirometry parameter in normal healthy adults.
• To look for co-relation of MVV with various anthropometric & spirometry parameter for assessment of respiratory muscles strength.
The following reference ranges (Table 4) were extracted from studies of reasonable quality that evaluated individuals in different age. The mean maximal inspiratory pressure (shown on vertical axis in cm H2O) declines with age during adulthood and is lower in women than male. Measurement of maximal inspiratory pressure, maximal expiratory pressure and maximal voluntary ventilation generated at mouth is an accepted non invasive clinical method for evaluation of the strength of respiratory muscles; however the choice of normal values for this measurement is made difficult by the wide variation in normal values reported in the literatures. In the healthy subjects mean values ranging from 89 to 146 cm. H2O have been reported for MIP and published value for MEP in adult male subjects ranging from 130 to 247 cm.H2O [1,2]. Leech et al studied 924 healthy caucasian adults and found respiratory pressures were positively correlated with weight but not to height or age, have reported a mean value of MEP in male adolescent of 131 cm, where as Cook et al reported a mean value of 198 cm H2O a difference of 50% [12]. Leo Black, Robert Hyatt. et al. studied MRP in 120 healthy subjects (60 males and 60 female) between 20 to 74 years of age, there was no significant regression of PImax, PEmax below 55 years of age, but above 55 years PEmax in males and females and PImax in males decreased with age [11]. Another study by H.Willson, N.T Cook et al in 370 normal healthy adults and children, in male PImax and PEmax were significantly correlated with age (p< 0.001 and < 0,005 respectively), whereas in females they were correlated with height (p< 0.0035 and 0.005) [12]. Robert J. Smith. et al. reported a mean value of MIP in females ranged from mean values of 86 to 108 cm H20 and for male 114 to 149 cm H20 [22]. Another study by I. Odd Chorob, et al (Pol Meruker Lekariski2002) in 166 clinically normal subjects (79 females and 87 males), in females PImax ranged 38 to104cm H2O with average 60 cm H2O, PEmax ranged 46- 104 cm H2O with average 87.5 cm H2O [8]. In male PImax was 40-120 cm.H2O with average 73.2cm, PEmax ranged 46-140 cm H2O with an average of 115.9.cm H2O. PImax was negatively correlated with age, in both groups. There was no correlation between PImax, PEmax and height in female groups. There was positive correlation between PImax, PEmax and weight in both groups (males and females). In a study done by Mc Elvancy G, Blackie S.et al. MIP and MEP in 64 normal females and 40 normal males older than 56 years of age no correlation was found with age [23]. Predicted normal values for MRP in caucasian adults and children by S.H. Wilson, NT Cook. et al. MIP and MEP measurement in 370 normal male and female, in male PImax and PEmax were significantly correlated with age (p< 0.001 and 0.035 respectively) whereas in females they were correlated with height (p< 0.035 and < 0.0respectively) [12]. In both boys and girls PImax was related with weight (p< 0.0001 &<0.01respectively) and PEmax to age (p< 0.0001 for both). Another study done by Babak Amra, Hasan Salehi. et al. they analyzed 224 male and 211 females mean value for MIP were 9.78 kPa for male and 7.61 kPa for females, mean value for MEP was 13.11 kPa for male and 10.21 kPa for female, the reported values were markedly less than American and European studies [36]. In this study age showed a negative correlation with MIP for both male and female. In a study done by A. Johan, C.C. Chan. et al. for measurement of MRP (MIP,MEP) in adults Chinese Malayas and Indians, MIP in male Chinese was 88.7+ 32.5, Malaya was 74+22.7 and Indians was 83.7+30 cm H2O [14]. MIP in female was 53.6+20.3 in Chinese 50.7+18.3 in Malaya, and 50.0+15.2 in Indian, MEP in male was 113.4+41.5 in Chinese 94.71+23.4 in Malaya and 98.4+22.2 cm H2O in Indians. In females MEP values were 68.3+24 for Chinese, 63.61+ 21.6 for Malaya and 62.2+20.4 for Indians. In a study done by Raida I, Harik Khan. et al. (Baltimore Longitudinal study of aging ) measured MIP in 668 men and women they analyzed 139 male and 128 female in healthy subgroup with wild age range (20-90 years) mean MIP was 102.2+29.4(range 33.0 to 173.2) in men and 72.4+23.3(range21.0.to 126.6) in females [3]. In the youngest group (age < 39.9 yrs.) the mean values for men and women were 117.6 cm H2O and 79.5cm respectively and it decreases with age. MIP reaches an average of 66.0 cm H2O and 45.5 cm H2O respectively for men and women in older age group (age >75 yrs.). Mean MIP value for females in each age group were approximately 70% of the values of the males. Age was found to be negative predictor, PEF was positive for male subjects. For females age and height were found to be negative predictor, whereas FVC, PEF and weight were positive predictor.
b) Study done by Misri Z.K., Sabir R.C. et al. at Kasturba Medical College Mangalore, 200 medical students (100 boys and 100 girls) were evaluated [35]. The values for PEmax and PImax were lower in females and this was in agreement with previous report by Black and Hyatt. No significant correlation was found between age and respiratory pressure in both male and females. There was significant correlation between MIP and body weight in females (p< 0.001). BSA showed significant correlation with height and weight (p< 0.01) with both male and female.
c) In another study done by A.Gopalkrishna, K.Vaishali. et al. at Kasturba Medical College Mangalore, they studied 250 healthy normal subjects [33]. In males PImax values correlated positively with height, weight, BMI, however PImax and PEmax were negatively correlated with age. For females PImax and PEmax showed positive correlation with height, weight, BMI and had moderately negative correlation with age, compared to previous studies this study showed lower mean value for adults, mean PImax for males was 75.35+ 20.89, mean PEmax was 93.39+ 20.21 cm, H2O, for females mean PImax was 48.80+16.91 and mean PEmax was 60.65+20.28 cm H2O [2,3,7,9]. There was significant correlation of PEmax with age for male and female subjects (p< 0.05) and PImax for male subjects (p< 0.05). However there was no correlation of PImax with age for female subjects (p>0.05). For females a significant correlation was found with height, weight and BMI. This may be explained by the fact that decreased muscle mass and strength fall with increasing age in males.
• Nonsmokers.
• History of smoking.
• History of serious pulmonary disease.
• Cardiac and neuromuscular disease.
• Physical findings suggesting cardiopulmonary disease.
• Evident chest deformity and neuromuscular deficit.
• Standing Height was measured in nearest centimeters.
• Weight was recorded in kilogram.
• B.M.I. was calculated from height and weight.
• Persons effort and technique
• Pressure gauge accuracy most common cause of errors
• Person device interface.
• The technologist should acts as an enthusiastic and encouraging coach eliciting maximal effort from the person for each maneuver. Most clinical laboratory performed only five measurements.
Sex wise distribution of study population: |
|||||
Valid |
Frequency |
Percent |
Valid Percent |
Cumulative Percent |
|
1 Male |
59 |
57.3 |
57.3 |
57.3 |
|
2 Female |
44 |
42.7 |
42.7 |
100 |
|
Total |
103 |
100 |
100 |
SEX |
AGE(yrs.) |
BMI |
HT(c m) |
WT(kg) |
|
1 Male |
Mean |
41.37 |
25.0844 |
167.9 |
70.91 |
N |
59 |
54 |
59 |
59 |
|
Std. Deviation |
16.197 |
3.26276 |
6.999 |
10.547 |
|
2 Female |
Mean |
45.59 |
26.4253 |
155.41 |
44 |
N |
44 |
44 |
44 |
44 |
|
Std. Deviation |
14.768 |
3.98833 |
7.54 |
11.263 |
|
Total |
Mean |
43.17 |
25.7136 |
162.56 |
67.98 |
N |
103 |
103 |
103 |
103 |
|
Std. Deviation |
15.669 |
3.65913 |
9.506 |
11.328 |
|
Minimum |
20 |
18.5 |
137 |
43 |
|
Maximum |
80 |
39.14 |
183 |
104 |
SEX |
FEV1/FVC% |
FEV1 L |
FEV1% |
FVC L |
FVC % |
|
1 Male |
Mean |
98.3956 |
2.891 |
98.7271 |
3.3141 |
93.37 |
N |
59 |
59 |
59 |
59 |
59 |
|
Std. Deviation |
12.69632 |
0.59676 |
12.79309 |
0.6179 |
12.352 |
|
2 Female |
Mean |
92.2023 |
1.903 |
96.6225 |
2.2518 |
94.47 |
N |
44 |
44 |
44 |
44 |
44 |
|
Std. Deviation |
13.10547 |
0.4466 |
14.33874 |
0.53831 |
12.122 |
|
Total |
Mean |
95.7499 |
2.4689 |
97.8281 |
2.8603 |
93.84 |
N |
103 |
103 |
103 |
103 |
103 |
|
Std. Deviation |
13.17363 |
0.72651 |
13.44738 |
0.78618 |
12.207 |
In female: Mean Pimax, PEmax and MVV were 50.0900 cm+ 21.50713(range 31.55763 to 69.72237), 56.0496 cm+19.13237 (range 36.91723 to 75.18197), 73.6427 L/min+20.34229(range 53.30091 to 93.98499) respectively. In female the values of Pimax, PEmax and MVV were lower than males.
a) Correlation of PImax to variables in entire group: Significant positive correlation was found with height (p= 0.002, r=0.298) with absolute value only. Significant negative correlation was found with age (both absolute and percent values p=0.01, r=0.337 and p=0.018, r=0.233 respectively). No correlation was found with weight, and B.M.I.
b) Correlation of PImax to spirometry parameters in entire group: Positive correlation was found between PImax and FEV1/FVC% (p=0.015, r=0.240). Significant positive correlation was found between PImax and FEV1% and FEV1 with absolute values only (P=0.000, r=0.348, p=0.000, r= 0.489 respectively). Significant positive correlation was found between PImax and FVC absolute value only (p=0.000, r=0.420). Significant positive correlation was found between PImax and PEmax both with absolute and percent values (p=0.000, r=0.584and p=0.012, r=0.247 respectively). Significant positive correlation was found between PImax and MVV absolute value only (p=0.000, r=0.468) (Table 4)
SEX |
Pimax kpa |
Pimax % |
Pemax kpa |
Pemax % |
MVV L/min |
MVV % |
Pimax cm |
Pemax |
|
1 Male |
Mean |
6.2451 |
61.576 |
7.0908 |
51.36 |
115.6236 |
89.298 |
66.76 |
75.8012 |
N |
59 |
59 |
59 |
59 |
59 |
59 |
59 |
59 |
|
Std. Deviation |
2.29066 |
22.1297 |
2.17682 |
15.715 |
24.93948 |
16.9971 |
24.48717 |
23.27025 |
|
2 Female |
Mean |
4.7418 |
68.85 |
5.2432 |
65.62 |
73.6427 |
82.641 |
50.69 |
56.0496 |
N |
44 |
44 |
44 |
44 |
44 |
44 |
44 |
44 |
|
Std. Deviation |
2.01189 |
35.451 |
1.78974 |
24.275 |
20.34229 |
18.6084 |
21.50713 |
19.13237 |
|
Total |
Mean |
5.6029 |
64.683 |
6.3016 |
57.45 |
97.69 |
86.454 |
59.8951 |
67.3636 |
N |
103 |
103 |
103 |
103 |
103 |
103 |
103 |
103 |
|
Std. Deviation |
2.29095 |
28.6594 |
2.21097 |
20.953 |
31.04196 |
17.9222 |
24.49023 |
23.63529 |
d)Correlation of PEmax to spirometry parameters in entire group: Significant positive correlation was found between PEmax and FEV1 L (absolute value p=0.000, r=0.476), negative correlation with PEmax %-p=0.041, r=0.202 Significant positive correlation was found between PEmax and FVC L(absolute value-p=0.000, r=0.464), PEmax and MVV both absolute and percent values (p=0.000, r=0.520, p=0.001, r=0.317 respectively). PEmax and PImax both absolute and percent values) p=0.012, r=0.247, and p=0.00, r=0.381respectively).
e) Correlation of MVV with variables in entire group: Significant positive correlation was found between MVV and height (p=0.000, r=0.719) with both absolute and percent value (p=0.027, r=0.218). Significant positive correlation was found between MVV and weight (p=0.007, r=0.265). Significant negative correlation was found between MVV and B.M.I. and age (p=0.003, r=0.309, and p=0.000, r=0.521 respectively) only with absolute values.
f) Correlation of MVV with spirometry parameters in entire group: Significant positive correlation was found between MVV and MVV% and spirometry, MVV L and FEV1/FVC% (p=0.000, r=0.403)FEV1%, (p=0.000, r=0.383) FEV1L ( p=0.000, r=0.0.839), FVC L (p=0.000, r=0.798) FVC%. No relation with MVV% and FEV1/FVC%, with FEV1% (p=0.046, r=0.197), FEV1L (p=0.023, r=0.224), FVCL (p=0.015, r=0.239).
g) Correlation of PImax to other variables in male subgroup: Significant negative correlation found between PImax and age (p=0.022, r=0.297) with absolute value only. No correlation found with height, weight and B.M.I. (Table-5).
Age group |
Pimax cm |
Pemax cm |
MVV L/min |
|
1.00 upto 30 |
Mean |
73.6634 |
77.4095 |
140.8644 |
Std. Deviation |
20.62059 |
21.94144 |
20.02683 |
|
N |
23 |
23 |
23 |
|
2.00 31-50 |
Mean |
68.6927 |
82.9858 |
122.6959 |
Std. Deviation |
31.17205 |
25.47858 |
25.49947 |
|
N |
17 |
17 |
17 |
|
3.00 51 and above |
Mean |
56.6739 |
67.4258 |
103.8539 |
Std. Deviation |
19.41337 |
21.29099 |
19.77533 |
|
N |
19 |
19 |
19 |
|
Total |
Mean |
66.76 |
75.8012 |
115.6236 |
Std. Deviation |
24.48717 |
23.27025 |
24.93948 |
i) Correlation of PEmax to other variables in male subgroup: No correlation found between PEmax and age, height, weight, and B.M.I.
j) Correlation of PEmax and spirometry parameters in male subgroup: Significant positive correlation found between PEmax value and FEV1 L (p=0.029, r= 0.285) FVC L (p=0.043, r=0.264), with MVV (p=0.002, r=0.387) MVV% (p=0.000, r=0.262), correlation was more significant with absolute functional and percent parameter, correlation was more significant with MVV parameters among all functional parameters. However PEmax had no significant correlation with FEV1/FVC ratio.
k) Correlation of MVV to variables in male subgroup: Significant positive correlation found between MVV value and height with absolute value only (p=0.000, r= 0.8487). Significant negative correlation was found between MVV and age with absolute value only (p=0.000, r=0.575). Negative correlation was found with B.M.I. with absolute value only(p=0.016,r=0.326).Correlation of MVV with spirometry parameters in male subgroup: Significant positive correlation was found between MVV and FEV1/FVC % (p=0.004, r=0.365), FEV1 L(P=0.000, R=0.699), FEV1 % (p=0.000, r=0.404), FVC L (p=0.000, r=0.673),FVC %(p=0.019, r=0.306). No correlation was found with MVV% value.
l) Correlation of PImax to other variables in female subgroup: Significant negative correlation was found between PImax value and age (p=0.024, r=0.339), both with absolute and percent value (p=0.049, r=0.298) no correlation with height, weight and B.M.I. (Table-6).
1.00 upto 30 |
Mean |
64.781 |
62.817 |
97.4848 |
Std. Deviation |
12.2044 |
17.06233 |
15.85331 |
|
N |
8 |
8 |
8 |
|
2.00 31-50 |
Mean |
51.1038 |
55.031 |
82.5159 |
Std. Deviation |
23.66648 |
18.019 |
19.24992 |
|
N |
19 |
19 |
19 |
|
3.00 51 and above |
Mean |
43.5963 |
54.0034 |
65.3478 |
Std. Deviation |
19.87184 |
21.50664 |
18.49246 |
|
N |
17 |
17 |
17 |
|
Total |
Mean |
50.69 |
56.0496 |
73.6427 |
Std. Deviation |
21.50713 |
19.13237 |
20.34229 |
|
N |
44 |
44 |
44 |
n) Correlation of PEmax to other variables in female subgroup: Significant positive correlation was found between PEmax value and height (p=0.013, r= 0.373), with absolute value only.
o) Correlation of PEmax to spirometry parameters in female subgroup: Significant positive correlation was found with FEV1 L( p=0.045, r=0.304), Pimax (p=0.004, r=0.428), PImax% (p=0.023, r=0.342), MVV (p=0.049, r=0.299) correlation was most significant with absolute MVV than percentage predicted values. However PEmax had no significant correlation with FEV1/FVC,FEV1%, FVC, FVC%.
p) Correlation of MVV to other variables in female group: Significant positive correlation found between MVV value and height (p=0.009, r=0.529) both absolute and percent values. Significant negative correlation was found between MVV and age (p=0.000, r=0.0612) .No correlation was found with weight and B.M.I.
1.00 upto 30 |
Mean |
71.3713 |
73.6438 |
129.0245 |
Std. Deviation |
19.03109 |
21.51987 |
27.96615 |
|
N |
31 |
31 |
31 |
|
2.00 31-50 |
Mean |
59.4097 |
68.2319 |
101.4897 |
Std. Deviation |
28.48794 |
25.76953 |
30.17956 |
|
N |
36 |
36 |
36 |
|
3.00 51 and above |
Mean |
50.4984 |
61.0874 |
85.226 |
Std. Deviation |
20.4496 |
22.15306 |
26.71788 |
|
N |
36 |
36 |
36 |
|
Total |
Mean |
59.8951 |
67.3636 |
97.69 |
Std. Deviation |
24.49023 |
23.63529 |
31.04196 |
(1)The first concerns the temporal course of the pressure generated. Rahn. et al. first reported that the maximum expiratory pressure can be sustained voluntarily is about 160 cm H2O, Mills. et al. later showed that values over 260 cm could be obtained by sudden voluntary efforts [11,17]. The measurement of MIP, MEP, MVV may vary markedly with the speed of the maneuver, the response characteristics of the pressure measuring device and the decision of the observer to record either peak or sustained maximal pressure.
(2) Secondly air leaks at the nose and mouth can produce inaccuracy during forced expiratory maneuvers.
(3) Thirdly forced respiratory maneuvers are influenced by motivation.
(4) Finally the number of trials to measure MIP, MEP may affect the MRP recorded Black, Hyatt and Leech who used two or three trials to determine normal values whose results were lower than those of Ringqvist21 because the latter used best of many attempts for measurement of these parameters ( > 20) [2,11,21].
While MRP generated are highly dependent on the pulmonary volumes at which they are measured, most studies have stated that measurements were made at or near RV and TLC for MIP, MEP and MVV respectively. A review of reported normal values for MIP, MEP and MVV (Table 4) showed substantial variations most probably a consequences of one or other factors outlined previously. Gibson. et al. while using indentical method as Black and Haytt to this study, collected data from small group of normal caucasian women and obtained a range considerably lower than those of Ringqvist and Black and Hyatt (PEmax 67-140 cm H2O and PImax 35-95cm H20 ), but very similar to our results [6,11, 21]. In comparison to different Asian studies A. Johan, CC Chan et al Devsahayam. et al. from C.M.C. Vellore, Misri Z.K. et al. Gopalkrishan K.M.C [5,33-35]. Mangalore India our results are similar to above studies Table 4.
Our results demonstrated a very strong gender effect, which is consistent with all previous findings reported in the literature [19]. In one study MIP in men was about 30% higher than in women [13]. In our study it is about 30% higher in men than women. RJ Smyth, K.R.Chapman. et al. in a study of 76 adolescent and 36 healthy adults reported MIP and MEP values which is significantly lower in females than males (for male mean MIP and MEP were 107+26 and 114+ for females the values were 76+25 and 86+22 respectively)[22]. Our results showed the importance of age as a significant negative predictor of MIP for both male (p< 0.022,r=0.297) and female(p< 0.024,r=0.298), a finding consistent with most of the studies including Harik Khan. et al. Vincken. et al. and Babak Amra, Hasan Salehi. et al. Gopalkrishanan. et al. all of these studies used population groups with wide age range [3,29,33,36]. Enright and co-workers had also reported similar results in elderly subjects above 55 years of age [13]. In our study PImax showed no correlation with height, weight and BMI for both sex, a finding not consistent with previous studies, but when entire group was taken into consideration PImax is positively correlated with height (P< 0.002,r=0.298). PEmax showed no correlation with age, height, weight and BMI in males, in females there was significant positive correlation seen between PEmax and height (p< 0.013, r=0.373), no correlation was seen between PEmax and age weight and BMI in females. Mean MVV value was 97.6900 L/min+31.04196 with male and female values were 115.6236 L/min +24.93948 and 73.6427 L/min +20.34229 respectively. MVV showed significant negative correlation with age in both males and females (p=0.000, r=0.575, p=0.000, r=0.612 respectively), consistent with study done by JA Neder, LE Nevy et al 8, in Brazilian population [8]. Significant positive correlation was seen between MVV and height in both male (p=0.000, r=0.487) and females (p=0.000, r=0.529) a finding seen in above Brazilian population [8]. No correlation was seen with weight in both the sex, but negative correlation was seen with BMI in males only (p< 0.16,r= 0.326). Wilson et al found that there was significant correlation with age in adult males and height in female [12]. In our study, age showed significant correlation with PImax, PEmax and MVV value in and both male and female and is consistent with the results of Ringqvist and Vincken et al, both of which used study group with wide age ranges and with Enright et al. in elderly subjects [4,13,21,29]. Berry et al reported a negative correlation between age and MIP, also Black and Hyatt who reported significant negative effect of age only in elderly women [11,15]. The failure to show an effect of age on MIP in a group of younger adults is consistent with previous findings that age related decline in pulmonary function begins in middle thirties, Guleria Jindal et al done a study of subjects between 12.5 to 18.5 years of age and showed a significant correlation with age, weight and height in both sexes [19,24,25]. Wilson et al reported that respiratory pressure in men are related to age and for women a significant relationship was shown only with height, this may be explained by the fact that muscle mass their strength falls with increasing age in men, their peak begins in second or third decade, while in women overall strength may not be related to age to such an extent [12]. In our study we found no correlation between MRP, MVV and body weight a finding not consistent with previous studies by Leech et al Arora Rochester et al, who found out that that diaphragm muscle mass varies almost three fold from atrophy in underweight person, to increased mass in muscular normal subjects [2,6]. Spirometry showed significant positive correlation for PImax in males with all n the parameters like FEV1, FVC, MVV, PEmax, except FEV1/ FVC%, in females PImax showed significant positive correlation with FEV1, and PEmax, no correlation was seen with FVC, FEV1/ FVC % and MVV values. For PEmax positive correlation was seen with FEV1, FVC%, PImax, MVV, no correlation with FEV1/FVC in males. In females positive correlation with FEV1, MVV and Pimax. No correlation was seen with FEV1/FVC%, FEV1%, FVC, FVC%. Significant positive correlation was seen between MVV and FEV1, FVC, FEV1/FVC in both males and females with absolute and percentage values. Correlation was more significant with absolute values than percent values. Our study suggest strong correlation between PImax, PEmax and FEV1, FVC. Polgar and Weng and other studies done in the past showed a similar results between respiratory muscle strengths and FEV1 and same study showed a positive correlation between respiratory muscle strength and FVC [12,13,24-26,37]. In our study absolute values of FEV1and FVC had better correlation with PImax and PEmax than percent values. Study also highlights relationship between MVV and Pimax, PEmax values amongst all the parameters MVV showed highest positive correlation with respiratory muscle strength, absolute MVV value showed better correlation than percent values. MVV values reflects the respiratory muscle endurance and fatigue. A test of endurance includes more dynamic factors than a test of strength. Measurement of respiratory muscle endurance indirectly assess performance of the inspiratory and expiratory muscles. Age was the strongest negative correlate with the studied dependable variables. The ageing process is associated with a reduction in the total and respiratory accessory muscular mass. Increased compliance of the abdominal compartment in older subjects can dissipate the generated pressure notably in forced expiration decreasing the MRP, as there is decrease in TLC and marked increase in RV with age. Considering the highest values for MIP, MEP are generated in the lowest and the highest lung volumes respectively, these physiological adaptation may also contribute to age related decline in MIP and MEP, MVV. MVV is a test of overall function of respiratory system, it is influenced not only by RM strength, but also by the compliance of the lung thorax system, the condition of the ventilatory control system and its resistance of both airways and tissues. Apart from the reduction in RM strength, aging is associated with reduction in the compliance of the chest wall and increase in both the resistive and elastic work of breathing [13]. It is important therefore to recognize that MVV was used in this study only as an indirect index of RM strength and these other factor should also be considered in the analysis of the results. Our results are similar to Asian studies. Significant correlation was found between maximal respiratory pressure (MIP, MEP) maximal voluntary ventilation with age, height in males. Compared to previous study our study had shown lower mean values for adults, the probable reason could be geographical variations, poor motivation and deliberate leak in the mouthpiece of the apparatus [2,3,7,9]. Several factors contribute to the wide range of values described in previous studies:
(1) Characteristics of the pressure measuring device and diameter of the orifice [1,2,7,15].
(2) Air leak at the nose and mouth.
(3) Motivation and number of trials may affects the MRP and MVV recorded.
In correlation of the variables with MRP our results showed statistically significant correlation of PEmax with age for male and female subjects (p< 0.05) and PImax with age for male subjects (p< 0.05) and female subjects. Black and Hyatt3 showed a decrease in the respiratory muscle strength with age, our study also showed decrease in respiratory muscle strength in male with age. Several factors may affect respiratory muscle strength in adults variable changes may occur in skeletal muscle, in the elastic recoil of the lungs, and chest wall and increase in residual volume. Increase in RV occur with age this may lead to an altered force length relationship of the diaphragm and diminished static outward recoil of the chest wall resulting in decreased PImax at RV [1,2]. This increased Rv is not uniform in all person and may contribute to differing PImax values in subjects of the same age. Our study showed decreased PEmax with age in both male and female subjects the probable reasons could be loss of lung recoil and increase in lung compliance in the elderly, which could tend to decrease PEmax. Changes also occur in the thoracic wall involving calcification and stiffening of the articulation of rib cage together with changes in the spinal curvature making chest wall less compliant. Our results showed that respiratory pressures in men are related to age, for female a significant relationship shown with height. This may be explained by that decreased muscle mass and strength fall with increasing age, there is approximately 8-10% decline for every 10 years, with peak decline in 2nd or 3rd decade of life [1,2]. Weight could affect the diaphragm mass exerting an influence on respiratory muscle performance which is not seen in our study.
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