Biomedical subjects

L C Lands

Publications and source records attributed to L C Lands.

At least 37 records · Page 2Linked to original sources

PubMed1998

A comparison of the availability of tobramycin for inhalation from vented vs unvented nebulizers.

STUDY OBJECTIVE: To compare drug output from a vented nebulizer (Pari LC Jet Plus) with a traditional unvented nebulizer (Hudson 1730 T Up-Draft 11) using aerosolized tobramycin, which is frequently used in the treatment of cystic fibrosis. DESIGN: Six nebulizers of each type were filled with a 4 mL tobramycin (80 mg) solution and were driven by a compressor (Pulmo-Aide). Various inspiratory flows (VI) (0, 5, 10, 15, 20 L/min for the Pari LC Jet Plus and 0, 5, and 10 L/min for the Hudson 1730, all at 40% relative humidity) were directed through each nebulizer. Drug output was measured from changes in weight and concentration (assessed by changes in osmometry) within the nebulizer. Particle size distributions were determined by laser diffraction allowing the calculation of the amount of aerosol output in the respirable range (<5 microm). The nebulizers were first run until end-nebulization to establish total drug output and then for either 4 or 5 min to determine the rate of drug output (mg/min) before intermittent aerosol output. RESULTS: The total drug output without VI for both the unvented and the vented nebulizers was not significantly different, 55 (51, 60) mg for the Hudson 1730 vs 51 (49, 53) mg for the Pari LC Jet Plus (mean [95% confidence limits]). Inspiratory flow had no effect on the unvented Hudson 1730 nebulizer but significantly increased the rate of total drug output and the rate of drug output in the respirable range for the vented Pari LC Jet Plus nebulizer (VI=0, 3.35 [2.84, 3.85] and 1.72 [1.48, 1.96] compared with VI=20, 9.87 [9.03, 10.70] and 6.11 [5.33, 6.88] mg/min). CONCLUSIONS: These findings indicate that the increase in the rate of drug output with VI for the vented nebulizer would result in shorter nebulization times and a relative decrease in drug loss during the expiratory phase.

Anti-Bacterial Agents↗

PubMed1997

Exercise ability in survivors of severe bronchopulmonary dysplasia.

There is limited information concerning the exercise performance of long-term survivors of bronchopulmonary dysplasia (BPD), and much of what is available pertains to those with relatively mild disease. The present study was undertaken to describe exercise responses in patients with a history of severe BPD, defined as those patients with a clinical and radiographic diagnosis of BPD who required supplemental oxygen at least until they were 44 wk postconceptual age and who were discharged home on oxygen. Fifteen children with a history of severe BPD were matched for gestational age with 15 children who had previously had respiratory distress syndrome but who did not develop BPD (Prem). These Prem control children were subsequently compared with 13 healthy control children born at term (Control) who were of similar postnatal age. Participants underwent pulmonary function testing, progressive exercise testing on a cycle ergometer, and a steady-state exercise test with cardiac output determined by CO2-rebreathing. Despite the patients with BPD having a lower FEV1 than those in the Prem group, who had lower values than the Control group (BPD, 64 +/- 21%; Prem, 85 +/- 11%; Control, 95 +/- 8%), the exercise capacity did not differ between the BPD and the Prem and between the Prem and the Control groups (BPD, 84 +/- 15%; Prem, 81 +/- 17%; Control, 91 +/- 12%). However, the BPD patients used a greater percentage of their ventilatory reserve (VEmax/40 FEV1: BPD, 93 +/- 20%; Prem, 67 +/- 12%; Control, 59 +/- 13%). Of the four patients with BPD who had significant oxygen desaturation with exercise, three had the lowest values for FEV1. Cardiac output was appropriate for oxygen consumption in most patients.

Anthropometry↗

PubMed1997

Estimation of mixed venous PCO2 for determination of cardiac output in children.

STUDY OBJECTIVES: Cardiac output (Q) can be estimated noninvasively during exercise by employing CO2-rebreathing techniques (equilibrium and exponential) to estimate the oxygenated mixed venous PCO2 (PvCO2). It has been found in adults and children that the equilibrium method underestimates Q as a result of overestimation of PvCO2, unless PvCO2 is "downstream corrected." In adults, it has been found that the exponential method does not require downstream correction and yields values similar to those obtained by the equilibrium method with downstream correction. The objectives of this study were as follows: to test whether the exponential method gives similar results to the equilibrium method with downstream correction in children; to verify that downstream correction is required in children; and to test whether a single equation could be used in adults and children to predict Q from oxygen consumption (VO2). DESIGN: Descriptive. SETTING: Exercise laboratory of a university hospital. PARTICIPANTS: 23 children (16 boys, 7 girls) with a mean age of 11.0 +/- 1.9 years (7.1 to 13.9 years), and 12 adults (7 men, 5 women) with a mean age of 33.6 +/- 7.2 years (24 to 48 years). INTERVENTIONS: While performing steady-state exercise on an ergometer, PvCO2 was determined in 14 children using both the equilibrium and exponential methods, and in all other subjects using the equilibrium method alone. MEASUREMENTS AND RESULTS: For the 14 children who underwent testing by both the equilibrium and exponential methods, the uncorrected equilibrium PvCO2 was significantly different from both the corrected PvCO2 and the exponential PvCO2. We found a strong relationship between Q (L/min), calculated using the downstream corrected values of PvCO2, and VO2 (L/min) (r2 = 0.95), and this relationship was similar to that obtained by dye dilution in other studies. When weight was included, it was determined that one equation could be used for children and adults: Q (L/min) = 1.42 + 5.80.VO2 (L/min) + 0.06.wt (kg), r2 = 0.97, SEY = 0.67. CONCLUSIONS: CO2-rebreathing techniques can be used to determine Q in children; the exponential method gives values that are similar to the equilibrium method with the downstream correction; and one prediction can be used for Q in adults and children.

Adolescent↗

PubMed1997

Measurement of infant pulmonary mechanics: comparative analysis of techniques.

In spontaneously breathing, intubated infants, lung elastance (E) and resistance (R) can be derived from the general equation of motion of the lung, Ptp = E.V + R.V + I.V + K, where P is the pressure applied to the system, E is the elastance (the reciprocal of the compliance), V is the volume, R is the resistance to airflow (V), I is the inertance, (V) is gas acceleration, and K is a constant representing alveolar pressure. However, differences in the methods of analysis may results in variations in the derived values of E and R. Eighteen non-sedated intubated infants, with a mean post-conceptual age of 32.3 weeks and mean weight of 1.51 kg, were studied to compare values in E and R derived by 7 different methods of analysis. For each infant, the same 7 consecutive breaths were analyzed by the following methods: 1) linear regression of Ptp on tidal volume (VT); 2) a Mead-Whittenberger analysis, 3) a 2-factor linear regression of Ptp with (V) and VT; 4) a 3-factor regression of Ptp with V, VT, and V; 5) a 3-factor linear regression model of Ptp with V, VT, and a (V)2 factor (to incorporate a turbulent flow factor); 6) a 4-factor regression of Ptp with V, VT, V, and (V)2; and 7) a transformation regression plot of Ptp/VT versus V/VT. In addition, the lung impedance was calculated from the values of E and R derived by each method. There was no significant difference between the measurements of E and R in methods 2-6 (by MANCOVA, with the subjects being covariates). Methods 1 and 7 had a significantly elevated E; in addition, Method 7 also had an elevated R. Furthermore, there were no differences between the impedance values derived from the different methods. We conclude that in this group of spontaneously breathing, intubated infants with a spectrum of pathology, the results of a 2-factor regression analysis are comparable to more complex models of the mechanics of the lung.

Airway Resistance↗

PubMed1996

Cardiorespiratory status after treatment for acute lymphoblastic leukemia.

The use of certain chemotherapeutic agents is associated with dose-related cardiotoxicity and, potentially, with restrictive lung disease. Therefore, we assessed the cardiopulmonary status and exercise capacity of 19 patients (pts; 9M:10F) 1.1 to 7.1 years (mean 4.6 +/- 1.5 years) after successful treatment of acute lymphoblastic leukemia (ALL) with Dana Farber Cancer Institute protocols. As body mass and nutritional status may influence exercise capacity, we also evaluated their anthropometric status and the plasma levels of rapid turnover proteins. Seven pts designated as "standard risk for relapse" (SR) had received low cumulative doses of doxorubicin (50 +/- 21 mg/m2), while twelve pts at "high or very high risk for relapse" (HR/VHR) had received higher doses (349 +/- 16 mg/m2). The evaluations included a questionnaire, anthropometric assessments, echocardiography, pulmonary function studies, exercise testing, and nutritional assays. Patients' data were compared with published normative data or with control values from our laboratories. In addition, we compared SR pt data with HR/VHR pt data. No pt had overt symptoms or signs of cardiorespiratory compromise. The pts had a higher percent of body fat than age-matched healthy controls (29.7 +/- 7.9% vs. 20 +/- 6%; P < 0.001). On echocardiography, cardiac systolic function was within normal limits in all. However, HR/VHR pts had lower left ventricular (LV) shortening fractions than SR pts (P < 0.05). LV filling velocity, indicative of diastolic function (the E/A ratio), was normal in most pts. Pulmonary function studies were normal. Exercise capacity was below predicted in most cases but heart rates at peak exercise and leg muscle function were within normal limits, suggesting a deconditioned state. Plasma levels of rapid turnover proteins were also normal. Despite lack of overt morbidity in our pt population, subtle abnormalities persist in cardiac function while pulmonary function is normal. Longitudinal studies will identify if further abnormalities or overt morbidity develop. In later years, continuing obesity and a sedentary state may contribute to clinically relevant heart disease.

Anthropometry↗

PubMed1996

Noninvasive determination of cardiac output in patients with severe airflow limitation.

The noninvasive measurement of cardiac output (Q) by the Indirect Fick CO2-rebreathing technique requires mixed venous P CO2 (P CO2) to be determined by the rebreathing maneuver, and Pa CO2 to be estimated from end-tidal P CO2 (PET CO2). Previous work has suggested that although P CO2 can be determined, Pa CO2 cannot be accurately estimated in patients with significant airflow limitation. Nineteen patients with cystic fibrosis who had severe airflow limitation (%FEV1, 29.3 +/- 7.12 SD) were studied during steady-state exercise at 50% of their measured maximal work capacity. Estimated Pa CO2 was slightly lower than Pa CO2 measured from blood samples obtained from an indwelling arterial catheter (measured: 45.2 +/- 4.92; estimate: 42.7 +/- 5.68 mm Hg). To calculate arterial blood content, the values derived from Pa CO2, pH, hemoglobin (Hb), and O2 saturation were compared with those derived from PET CO2 and O2 saturation, where (1) pH was assumed to be 7.40 and Hb was measured, and (2) pH was assumed to be 7.40 and Hb was assumed to be 15 g/dl (measured mean pH, 7.34; Hb, 14.4 g/dl). No difference in arterial CO2 content was seen between the three methods (measured: 47.53 +/- 5.17; estimate 1: 49.57 +/- 6.58; estimate 2: 49.12 +/- 6.61 ml/100 ml). As pH and Hb can also affect mixed venous CO2 content, the effect on Q was also assessed. Both estimates fit closely with measured Q (r2=0.77 and 0.76), with intercepts not different from zero and slopes not different from 1, and coefficients of variation of 13.5 and 14.6%. When viewed with regard to the confidence intervals for Q as a function of O2 consumption, Q was altered to a minor extent. We conclude that the use of PET CO2 to estimate Pa CO2 can give reasonable values for Q determined noninvasively in patients with severe airflow limitation.

Adult↗

PubMed1996

Accuracy of measurements of small changes in soft-tissue mass by dual-energy x-ray absorptiometry.

OBJECTIVE: To assess the ability of dual-energy x-ray absorptiometry (DXA) to measure accurately small changes in lean soft-tissue mass. DXA has recently been suggested as an accurate, noninvasive method of analysis of body composition. DESIGN: Experimental use of DXA to assess human body composition before and after rapid saline infusion. PARTICIPANTS: Six healthy men. OUTCOME MEASURES: Weight measurements, DXA scanning results and skinfold thicknesses taken on the first day of the experiment and on the second day, before and after rapid saline infusion. RESULTS: After the infusion, the subjects' weight increased by a mean 2.26 kg (standard deviation 0.199 kg). At each of the four readings, there was a strong correlation between weight and DXA-derived total mass (r = 0.999) and between skinfold-derived fat-free mass and DXA-derived lean mass (r = 0.941 to 0.957). Following infusion, no differences were found between the measured and theoretical (i.e., preinfusion value plus weight change) values for total mass (p = 22), lean soft-tissue mass (p = 0.10) and lean mass (p = 0.09). The bias was -0.669 (95% confidence interval [CI] 0.18 to -1.49) for total mass, -0.65 (95% CI 0.16 to -1.47) for lean soft-tissue mass, and -0.14 (95% CI 0.11 to -0.38) for lean mass. CONCLUSIONS: DXA is an improvement over- previous dual-energy technologies and appears to provide sufficient accuracy to detect small (less than 2.5 kg) changes in mass in individual, healthy men, over a short period and under non-steady-state conditions. Therefore, DXA may also be of practical use for longitudinal assessment of weight change.

Absorptiometry, Photon↗

PubMed1995

Skeletal muscle pyruvate dehydrogenase activity during maximal exercise in humans.

The regulation of the active form of pyruvate dehydrogenase (PDHa) and related metabolic events were examined in human skeletal muscle during repeated bouts of maximum exercise. Seven subjects completed three consecutive 30-s bouts of maximum isokinetic cycling, separated by 4 min of recovery. Biopsies of the vastus lateralis were taken before and immediately after each bout. PDHa increased from 0.45 +/- 0.15 to 2.96 +/- 0.38, 1.10 +/- 0.11 to 2.91 +/- 0.11, and 1.28 +/- 0.18 to 2.82 +/- 0.32 mmol.min-1.kg wet wt-1 during bouts 1, 2, and 3, respectively. Glycolytic flux was 13-fold greater than PDHa in bouts 1 and 2 and 4-fold greater during bout 3. This discrepancy between the rate of pyruvate production and oxidation resulted in substantial lactate accumulation to 89.5 +/- 11.6 in bout 1, 130.8 +/- 13.8 in bout 2, and 106.6 +/- 10.1 mmol/kg dry wt in bout 3. These events coincided with an increase in the mitochondrial oxidation state, as reflected by a fall in mitochondrial NADH/NAD, indicating that muscle lactate production during exercise was not an O2-dependent process in our subjects. During exercise the primary factor regulating PDHa transformation was probably intracellular Ca2+. In contrast, the primary regulatory factors causing greater PDHa during recovery were lower ATP/ADP and NADH/NAD and increased concentrations of pyruvate and H+. Greater PDHa during recovery facilitated continued oxidation of the lactate load between exercise bouts.

Adenine Nucleotides↗

PubMed1995

Effect of analyzer on determination of mixed venous PCO2 and cardiac output during exercise.

Cardiac output (CO) during exercise can be determined noninvasively by using the indirect Fick CO2-rebreathing technique. CO2 measurements for this technique are usually performed with an infrared analyzer (IA) or mass spectrometer (MS). However, IA CO2 measurements are susceptible to underreading in the face of high O2 concentrations because of collision broadening. We compared an IA (Ametek model CD-3A) with a MS (Marquette model MGA-1100) to see the effect this would have on mixed venous PCO2 (PVCO2) and CO measurements. After calibration with room air and a gas mixture of 5% CO2-12% O2-83% N2, both devices were tested with three different gas mixtures of CO2 in O2. For each gas mixture, IA gave lower CO2 values than did the MS (4.1% CO2: IA, 3.85 +/- 0.01% and MS, 4.13 +/- 0.01%; 9.2% CO2: IA, 8.44 +/- 0.07% and MS, 9.19 +/- 0.01%; 13.8% CO2: IA, 12.57 +/- 0.15% and MS, 13.82 +/- 0.01%). Warming and humidifying the gases did not alter the results. The IA gave lower values than did the MS for eight other medical gases in lower concentrations of O2 (40-50%). Equilibrium and exponential rebreathing procedures were performed. Values determined by the IA were > 10% higher than those determined by the MS for both rebreathing methods. We conclude that all IAs must be checked for collision broadening if they are to be used in environments where the concentration of O2 is > 21%. If collision broadening is present, then either a special high O2-CO2 calibration curve must be constructed, or the IA should not be used for both arterial PCO2 and PVCO2 estimates because it may produce erroneously low PVCO2 values, with resultant overestimation of CO.

Blood Gas Analysis↗

PubMed1994

Plasma volume and ion regulation during exercise after low- and high-carbohydrate diets.

This study compared plasma volume (PV) and ion regulation during prolonged exercise in control vs. glycogen-depleted (GD) conditions, with emphasis on the initial minutes of exercise. In two trials separated by 1-2 wk, four adult males cycled at 75% of peak oxygen consumption (VO2) until exhaustion (50 +/- 7 min for GD) or until the GD exhaustion time in the control trial. Blood was sampled from catheters placed in the brachial artery and retrograde in the femoral vein (fv). Arterial PV decreased rapidly and by 15 min PV was 83% (control) and 88% (GD) of initial. The decrease in PV was accompanied by a net osmotic flux of water from plasma and inactive tissues to contracting muscles. The significantly greater decrease in PV in control compared with GD was associated with a higher muscle lactate content (Lac-; 36 vs. 17 mumol/g dry wt, respectively). Increases in plasma [Cl-] and [Na+] were less than predicted from decreased PV, indicating net loss of these ions from the plasma compartment. Increases in arterial and fv [K+] were 50% greater than could be accounted for by decreased PV, corresponding with increased arterial and fv plasma K+ contents. The rapid net release of K+ and Lac- from contracting muscle during the first few minutes of exercise in both trials was abolished (control) or reversed (GD) within 15 min of beginning exercise.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1994

A simple isokinetic cycle for measurement of leg muscle function.

The measurement of net pedaling torque during isokinetic cycling allows for the evaluation of leg muscle strength and work capacity over fixed time intervals. However, the expense and difficulty of constructing an isokinetic cycle have limited the widespread application of this useful research tool. We have modified a simple commercially available isokinetic cycle that uses hydraulics to maintain pedaling velocity. A strain gauge on the flywheel axle strut measures the torsion on the strut caused by pedaling. To evaluate this device, seven healthy subjects (3 males and 4 females) were each tested twice at 60, 90, and 120 rpm for peak power during a 10-s sprint and at 100 rpm for total work performed during a 30-s sprint. These results were compared with predicted values for age, height, and sex developed on a more complicated isokinetic cycle. Subjects also performed a progressive cycle ergometry test. For the group, peak power was 97.30 +/- 12.64% of predicted (males 883.70 +/- 202.76 W; females 657.00 +/- 66.42 W) and work output was 107.70 +/- 15.75% of predicted (males 15.50 +/- 2.85 kJ; females 11.70 +/- 2.17 kJ), whereas maximal progressive exercise capacity was 126.40 +/- 25.84% (males 245.30 +/- 56.58 W; females 212.30 +/- 35.49 W). The relatively lower work values generated on this cycle (compared with the maximal progressive exercise capacity) can be attributed to the location of the strain gauge, resulting in measurement of effective work output on the flywheel.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1993

Relationships among nutritional status and skeletal and respiratory muscle function in cystic fibrosis: does early dietary supplementation make a difference?

Relationships among nutritional status and skeletal and respiratory muscle function were examined in 16 children with cystic fibrosis (CF) and mild lung disease (FEV1 95 +/- 16% predicted). Subjects were randomly assigned to receive (or not) noninvasive nutritional supplementation at 25% of normal energy recommendations for 6 mo. Skeletal muscle strength and power were similar to those of healthy children as were respiratory muscle strength and endurance. Stepwise-regression analysis indicated that changes in skeletal muscle strength and energy intake correlated significantly with growth [weight (kg) = 1.90 - 0.60 (Tanner Stage) + 0.49 (maximum voluntary strength (Nm) + 0.03 (energy intake, % RNI), r = 0.76, P < 0.05], though body composition, protein biochemistry, muscle power, respiratory muscle strength, and use of dietary supplements did not. Thus, changes in skeletal muscle strength may be a functional index of changes in nutritional status in CF. Dietary supplementation per se was not associated with functional improvement.

Adolescent↗

PubMed1993

Maximal short-term exercise performance and ion regulation in cystic fibrosis.

Controversy exists over whether defects in electrolyte transport exist in erythrocytes from cystic fibrosis (CF) patients. We hypothesized that differences in ion regulation in CF would affect skeletal muscle performance during intense exercise. Seven well-nourished CF patients were compared with seven healthy age-matched control subjects. Skeletal muscle performance was assessed during a 30-s sprint on an isokinetic cycle ergometer. Ion regulation was evaluated from arterialized venous blood sampled at rest, at peak exercise, and after 5 min of recovery. There was no difference in sprint performance between the CF (total work, 93.7 +/- 30.02% predicted; endurance, 30.6 +/- 9.93% decline) and control (109.7 +/- 19.48%; 35.6 +/- 14.76%) groups. The changes in plasma and erythrocyte ions and blood gases did not differ between the groups. There was a suggestion that the CF group may have had an inadequate ventilatory response to the metabolic challenge of short-term maximal exercise. The contribution of decreases in the strong ion difference to increases in plasma hydrogen ion concentrations was less in the CF group. This may be due to alterations in ionic regulation in CF, but the influence of inadequate arterialization of the blood samples could not be ruled out.

Adult↗

PubMed1993

Pyruvate dehydrogenase activity and acetyl group accumulation during exercise after different diets.

Pyruvate dehydrogenase activity (PDHa) and acetyl group accumulation were examined in human skeletal muscle at rest and during exercise after different diets. Five males cycled at 75% of maximal O2 uptake (VO2 max) to exhaustion after consuming a low-carbohydrate diet (LCD) for 3 days and again 1-2 wk later for the same duration after consuming a high-carbohydrate diet (HCD) for 3 days. Resting PDHa was lower after a LCD (0.20 +/- 0.04 vs. 0.69 +/- 0.05 mmol.min-1.kg wet wt-1; P < 0.05) and coincided with a greater intramuscular acetyl-CoA-to-CoASH ratio, acetyl-CoA content, and acetylcarnitine content. PDHa increased during exercise in both conditions but at a lower rate in the LCD condition compared with the HCD condition (1.46 +/- 0.25 vs. 2.65 +/- 0.23 mmol.min-1.kg wet wt-1 at 16 min and 1.88 +/- 0.20 vs. 3.11 +/- 0.14 at the end of exercise; P < 0.05). During exercise muscle acetyl-CoA and acetylcarnitine content and the acetyl-CoA-to-CoASH ratio decreased in the LCD condition but increased in the HCD condition. Under resting conditions PDHa was influenced by the availability of fat or carbohydrate fuels acting through changes in the acetyl-CoA-to-CoASH ratio. However, during exercise the activation of PDHa occurred independent of changes in the acetyl-CoA-to-CoASH ratio, suggesting that other factors are more important.

Acetyl Coenzyme A↗

PubMed1993

Comparison of three techniques for body composition analysis in cystic fibrosis.

Body composition analysis is an important component of nutritional assessment in cystic fibrosis (CF). No gold standard of measurement exists, and techniques applicable to healthy populations may be unsuitable for CF patients. We assessed lean body mass (LBM) in 12 children with CF by skinfold (SK) measurements, bioelectrical impedance analysis (BIA), and dual-photon absorptiometry (DPA) and repeated these measures in 10 subjects 6 mo later. SK and DPA measures in eight older CF patients and eight healthy controls were compared to evaluate any effect of disease on estimates of LBM by use of DPA. Good agreement between the measures was seen at baseline and 6 mo by use of concordance plots. However, the limits of agreement between measures ranged up to 19% of SK-derived LBM measures (baseline: SK and DPA, 2.63 to -3.93 kg; SK and BIA, 2.36 to -1.24 kg; BIA and DPA, 1.88 to -4.28 kg; 6 mo: SK and DPA, 2.10 to -3.58 kg; SK and BIA, 6.28 to -5.49 kg; BIA and DPA, 5.53 to -7.79 kg). The change in LBM over 6 mo did not correlate among the three measures. Only BIA change in LBM correlated with weight change (r = 0.716, P < 0.02), probably due to the inclusion of weight in the regression equations for determining LBM from impedance. The relationship between SK and DPA measures did not differ between the CF and control groups, suggesting that there was no effect of disease on the DPA measure. The results suggest that none of these methods is precise enough to follow short-term changes in the nutritional status of CF patients longitudinally.

Absorptiometry, Photon↗

PubMed1993

Respiratory and peripheral muscle function in cystic fibrosis.

Respiratory muscle strength (RMS) and endurance are often preserved in cystic fibrosis (CF) despite malnutrition, chronic airflow limitation, and hyperinflation. Inspiratory muscle function may be relatively preserved due to a selective "training stimulus" from chronic lung disease. Respiratory and peripheral muscle function were evaluated in 14 stable CF patients and 16 healthy control subjects. RMS was measured using static maximal pressures performed at FRC. Respiratory fatigue (RF) was assessed using 18 repeated static efforts (10 s on/5 s off) over 4.5 min. Peripheral function was evaluated by leg strength (LS) and leg fatigue (LF) measured during sprint efforts on an isokinetic cycle ergometer. Despite a lower weight (mean +/- SD, 94 +/- 9.6% ideal wt for CF patients versus 107 +/- 14.6% for controls) and elevated residual volume (RV)/TLC ratio (38 +/- 13.0 versus 22 +/- 5.3), the CF group maintained RMS (inspiratory 96 +/- 23.2 versus 114 +/- 33.2; expiratory 105 +/- 28.3 versus 123 +/- 40.9 cm H2O) but had decreased LS (590 +/- 201.7 versus 813 +/- 167.1 W). There were no differences between the groups with respect to RF or LF. For the control group, inspiratory and expiratory RMS correlated with LS (p < 0.01) and lean body mass (p < 0.01). For the CF group, while expiratory RMS (p < 0.05) and LS (p < 0.01) correlated with lean body mass and each other (p < 0.01), inspiratory RMS was independent of lean body mass and LS (p > 0.1). Female CF patients appeared to have a better preservation of inspiratory RMS than males with CF.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1993

Flow limitation while breathing HeO2.

Flow limitation during a maximum expiratory flow-volume curve (MEFVC) while breathing air occurs at lung volumes below 70% vital capacity (VC). To evaluate small airways function, use has been made of the volume of isoflow (VisoV), comparing an MEFVC done in air to one done in 80% helium, 20% O2 (HeO2). The VisoV has high intra-subject variability. This study investigated whether this variability was due to an inability to flow limit while breathing HeO2. This would occur if the velocity of expiratory muscle contraction did not result in sufficient intrathoracic pressures to cause dynamic airway compression in the face of increased expiratory flows while breathing HeO2. Seven healthy adult male subjects performed repeated VC expirations of varying effort with an esophageal balloon in place in a body plethysmograph while breathing air and HeO2. The flow-volume curves were matched at residual volume and transpulmonary pressure-flow plots were constructed at volume isopleths of 70, 50, and 25% VC. In air, flow limitation was demonstrated in 3, 6, and 7 subjects at 70, 50, and 25% VC, respectively. In HeO2, flow limitation was achieved in 1 and 4 subjects at 70 and 50% VC. Although one subject demonstrated intermittent glottic closure, the remaining 6 demonstrated flow limitation at 25% VC. We concluded that dynamic airways compression occurs even with the increased flows in HeO2.

Adult↗

PubMed1992

Analysis of factors limiting maximal exercise performance in cystic fibrosis.

1. Maximal exercise capacity in cystic fibrosis is influenced by both pulmonary and nutritional factors: lung disease by limiting maximal achievable ventilation, and malnutrition through a loss of muscle mass. The associated reduction in everyday activities may result in peripheral muscle deconditioning. 2. We studied 14 stable patients with cystic fibrosis (six males, eight females) and 14 healthy control subjects (seven males, seven females) in order to assess the influence of these factors on exercise performance. Subjects underwent anthropometry to estimate muscle mass, spirometry to assess ventilatory capacity, a 30 s sprint on an isokinetic cycle ergometer to assess maximal leg muscle performance, and progressive cycle ergometry to assess overall exercise capacity. 3. Compared with control subjects, the patients with cystic fibrosis were of similar age and height but weighed proportionately less [% ideal weight (mean +/- SD): 94.3 +/- 9.64 versus 109.5 +/- 11.82] and showed evidence of airflow limitation [forced expiratory volume in 1.0 s (FEV1.0) 72.5 +/- 24.78 versus 112.6 +/- 14.25% of predicted]. 4. The patients with cystic fibrosis did less absolute (5.1 +/- 1.89 versus 7.3 +/- 1.97 kJ) but similar relative maximal (11.5 +/- 3.41 versus 13.1 +/- 3.55 kJ/kg lean body mass) sprint work. During progressive exercise, the group with cystic fibrosis achieved lower absolute [maximal O2 consumption (VO2max.) 1.8 +/- 0.527 versus 3.0 +/- 0.655 litres/min] and relative (VO2max./kg lean body mass: 40.5 +/- 9.23 versus 53.0 +/- 11.62 ml min-1 kg-1) work levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗