Measurement of Respiratory Sensation in Interstitial Lung Disease: Exercise Testing

6 Dec

Measurement of Respiratory Sensation in Interstitial Lung Disease: Exercise TestingExercise Testing
Eighteen patients performed progressive incremental exercise until limited by exhaustion or by symptoms on the cycle ergometer (Monark-Crescent AB, Varberg, Sweden). Two ILD patients were unable to exercise due to severe dyspnea at rest or joint complaints. Each person breathed through a low-resistance, Hans-Rudolph twoway valve during quiet breathing at rest for 5 min. Then, the patient pedalled at 50 rpm with zero load for 1 min. Power production was increased by 12.5 to 25 W/min for ILD patients. Expired gas was collected and analyzed for Ve, Vo2, and Vco2 every 30 s using the Metabolic Measurement Cart (Sensormedics, Schiller Park, IL). Heart rate was recorded with a 12-lead electrocardiogram. Oxygen saturation was measured by ear oximetry (Hewlett-Packard model 47201A) in the 18 patients and was recorded at rest and at the end of each minute of exercise. Peak values for Vo2 were measured. Gas exchange during exercise was examined as the difference between SaOa at rest and at peak exercise (ASaO*). Values are positive in patients with arterial desaturation and negative in patients with improvement in Sa02 during exercise. Differences in Sa02 (percent) were normalized for the differences between Vo2 (liters per minute) measured at peak exercise and at rest (AVoJ.

Statistical Analysis
Differences between control subjects and ILD patients were evaluated using unpaired t tests. Correlations among clinical, psychophysical, lung function and exercise variables were evaluated using Spearmans rank order correlation coefficient (r,). Values are presented as mean ± SD. A p value less than 0.05 was considered significant.
Anthropometric data and results of lung function and exercise parameters for both the patient and control groups are presented in Table 1. Age, gender, height and weight were comparable in the two groups. Patients with ILD exhibited significantly lower levels of lung function (FVC and FEVx) compared with control subjects. The values for the clinical rating of breathlessness represented a wide spectrum in the ILD patients. The range of ratings was 0 to 3 for the MRC scale, 25 to 95 mm for the OCD, and 1.5 to 11.5 for the BDI. Values obtained by the clinical rating methods of breathlessness were highly interrelated (MRC vs OCD, rs = — 0.80; MRC vs BDI, rg = — 0.87; and OCD vs BDI, rs = 0.70; p<0.001 for all comparisons).
Table 1—Anthropometric Data, Lung Function, and Exercise Parameters in Normal Subjects and Patients with ILD

Normal Subjects (n = 10)ILD(n = 20)
Anthropometric Data
Age (yr)56.3±8.058.9±14.1
Sex (F/M)5/510/10
Height (cm)167.6 ±10.1166.9 ±8.9
Weight (kg)75.2 ±10.771.5 ±14.2
Lung Function
TLC(L)4.27±1.26 (78± 17%)
FVC (L)4.04±1.22t2.52±0.76f (69 ±14%)
FEV, (L)3.19±0.88f1.86±0.53f (70 ±16%)
Dsb (ml/min/mm Hg)13.2 ±5.9 (62 ±20%)
Exercise Parameters(n as 18)
Peak Vo216.7 ±6.5
ASaCyAVo*7.8 ±9.9