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PubMed2004

Effect of salmeterol on the ventilatory response to exercise in chronic obstructive pulmonary disease.

This study examined the effects of bronchodilator-induced reductions in lung hyperinflation on breathing pattern, ventilation and dyspnoea during exercise in chronic obstructive pulmonary disease (COPD). Quantitative tidal flow/volume loop analysis was used to evaluate abnormalities in dynamic ventilatory mechanics and their manipulation by a bronchodilator. In a randomised double-blind crossover study, 23 patients with COPD (mean +/- SEM forced expiratory volume in one second 42 +/- 3% of the predicted value) inhaled salmeterol 50 microg or placebo twice daily for 2 weeks each. After each treatment period, 2 h after dose, patients performed pulmonary function tests and symptom-limited cycle exercise at 75% of their maximal work-rate. After salmeterol versus placebo at rest, volume-corrected maximal expiratory flow rates increased by 175 +/- 52%, inspiratory capacity (IC) increased by 11 +/- 2% pred and functional residual capacity decreased by 11 +/- 3% pred. At a standardised time during exercise, salmeterol increased IC, tidal volume (VT), mean inspiratory and expiratory flows, ventilation, oxygen uptake (VO2) and carbon dioxide output. Salmeterol increased peak exercise endurance, VO2 and ventilation by 58 +/- 19, 8 +/- 3 and 12 +/- 3%, respectively. Improvements in peak VO2 correlated best with increases in peak VT; increases in peak VT and resting IC were interrelated. The reduction in dyspnoea ratings at a standardised time correlated with the increased VT. Mechanical factors play an important role in shaping the ventilatory response to exercise in chronic obstructive pulmonary disease. Bronchodilator-induced lung deflation reduced mechanical restriction, increased ventilatory capacity and decreased respiratory discomfort, thereby increasing exercise endurance.

Administration, Inhalation↗
PubMed1992

Effect of volume history on changes in DLcoSB-3EQ with lung volume in normal subjects.

The purpose of this study was to determine the relationship between the three-equation diffusing capacity for carbon monoxide (DLcoSB-3EQ) and lung volume and to determine how this relationship was altered when maneuvers were immediately preceded by a deep breath. DLcoSB-3EQ maneuvers were performed in nine healthy subjects either immediately after a deep breath or after tidal breathing for 10 min. The maneuvers consisted of slow inhalation of test gas from functional residual capacity to 25, 50, 75, or 100% of the inspiratory capacity and, without breath holding, slow exhalation to residual volume. After either a deep breath or tidal breathing, we found that DLcoSB-3EQ decreased nonlinearly with decreasing lung volume. At all lung volumes, DLcoSB-3EQ was significantly greater when measured after a deep breath than after tidal breathing. This effect increased as lung volume decreased, so that the greatest difference between DLcoSB-3EQ after a deep breath and that after tidal breathing occurred at the lowest lung volume. We conclude that a deep breath or spontaneous sigh has a role in reestablishing the pathway for gas exchange during tidal breathing.

Adult↗
PubMed1993

Lung volumes in tetraplegic patients according to cervical spinal cord injury level.

Fifty-six tetraplegic patients with motor complete lesions (Frankel A and B) underwent spirometric measurements more than 6 months after injury. The results were evaluated according to the level of transection of the cervical cord. A pronounced restrictive respiratory dysfunction was demonstrated in all patients. The expiratory reserve volume (ERV) was zero or markedly reduced in patients at all lesion levels. Systematic increases in both ERV and vital capacity (VC) were found with lower lesion level. The inspiratory capacity (IC) was reduced at all injury levels, but there were no systematic differences in IC between injury levels C4-C8. The total lung capacity (TLC) was reduced and the ratio residual volume/total lung capacity (RV/TLC) was increased in patients at all injury levels. The lung function of patients tested > 12 months after injury was not significantly different from the function in those tested 6-12 months after injury. A respiratory rehabilitation programme for tetraplegic patients should take into account the fact that the respiratory function, especially the forced expiration, is dependent upon injury level.

Adolescent↗
PubMed1993

Lung volume changes during relatively fluent speech in stutterers.

We investigated breathing patterns in stutterers during relatively fluent speech and compared these with normal subjects for similar speech tasks. Rib cage and abdominal displacements and esophageal, gastric, and transdiaphragmatic pressures provided indexes of diaphragmatic, rib cage, and abdominal muscle contraction. We found that stutterers spoke either at substantially higher or lower lung volumes than normal subjects, confining their speech to the inspiratory capacity or expiratory reserve volume. During spontaneous speech, stutterers did not cross functional residual capacity (FRC) for most breaths. In addition, stutterers used several different motion pathways from breath to breath. At high lung volumes stutterers used the diaphragm to provide inspiratory braking. At lung volumes below FRC stutterers recruited their abdominals. This contrasted with normal subjects who spoke in the middle part of the vital capacity and who recruited inspiratory and expiratory rib cage muscles above and below FRC, respectively. Breath sizes were log-normally distributed in stutterers compared with a gaussian distribution in normal subjects (P < 0.001). During reading, stutterers tended to cross FRC (P < 0.01), used very similar initiation lung volumes from breath to breath (P < 0.001), and used similar motion pathways to achieve deflation. We conclude that stutterers sustain fluency by speaking at abnormally high or low lung volumes and that this may account for the different muscle patterns observed in stutterers compared with normal subjects.

Diaphragm↗
PubMed2006

Inspiratory fraction and exercise impairment in COPD patients GOLD stages II-III.

The inspiratory-to-total lung capacity ratio or "inspiratory fraction" (inspiratory capacity(IC)/total lung capacity (TLC)) may be functionally more representative than traditional indices of resting airflow limitation and lung hyperinflation in patients with chronic obstructive pulmonary disease (COPD). In the present retrospective study, a comparison was made of the individual performance of post-bronchodilator IC, IC/TLC and forced expiratory volume in one second (FEV(1)) in predicting a severely reduced peak oxygen uptake (V'(O(2)); <60% predicted) in 44 COPD patients Global Initiative for Chronic Obstructive Lung Disease stages II-III (post-bronchodilator FEV(1) ranging from 31-79% pred). Patients with lower IC/TLC values (<or=0.28) showed increased lung volumes and reduced exercise capacity as compared with other subjects. Following a multiple linear regression analysis, only IC/TLC and FEV(1) remained as independent predictors of V'(O(2)) (r(2) = 0.33). A receiver operating characteristic (ROC) curve analysis revealed that an IC/TLC <or=0.28 had the highest specificity (89.6%), positive predictive value (80%) and overall accuracy (86.3%) in identifying patients with V'(O(2)) <60% pred. In addition, the area under the ROC curve tended to be higher for IC/TLC than IC. In conclusion, post-bronchodilator total lung capacity-corrected inspiratory fraction provides useful information in addition to forced expiratory volume in one second and inspiratory capacity, to estimate the likelihood of chronic obstructive pulmonary disease patients to present with severely reduced maximal exercise capacity.

Aged↗
PubMed2002

Respiratory function in singleton and twin pregnancy.

OBJECTIVE: Singleton pregnancy causes important changes in respiratory function. The incidence of twin pregnancies is increasing, but it is not known whether affected women suffer greater respiratory compromise. The aim of this study was to determine if changes in respiratory function during pregnancy in healthy women were greater in those with a twin pregnancy compared with those with a singleton pregnancy. DESIGN: Cross sectional study. SETTING: London teaching hospital. POPULATION: Healthy pregnant women attending the antenatal clinic and ultrasound department. METHODS: A cross sectional study of respiratory function was performed in 68 women with twin pregnancies (17 examined in the first trimester, 35 second trimester, 16 third trimester) and 140 women with singleton pregnancies (28, 80, 40, respectively) and 22 non-pregnant women. Women were examined once between 7 and 40 weeks of gestation. Forced vital capacity, relaxed vital capacity, forced expiratory volume in 1 second (FEV1), peak flow, inspiratory capacity, functional residual capacity (FRC), expiratory reserve volume, pulmonary diffusing capacity and minute ventilation were measured. RESULTS: Both in twin and singleton pregnancies, the mean FRC and expiratory reserve ventilation of women studied in the third trimester and minute ventilation of women studied in each trimester differed significantly from that of the non-pregnant women. There were, however, no significant differences demonstrated in respiratory function between healthy women with twin as compared with singleton pregnancies. CONCLUSION: In healthy women, the extra demands of atwin compared with a singleton pregnancy do not compromise further the respiratory system.

Adult↗
PubMed1987

Effect of hyperinflation and equalization of abdominal pressure on diaphragmatic action.

We tested the hypothesis that the mechanical arrangement of costal (COS) and crural (CRU) diaphragms can be changed from parallel to series when direct or indirect transmission of tension occurs. Ratio of rib cage to abdominal displacement (RC/AB) resulting from separate COS and CRU stimulations were used to measure RC expanding action. Hyperinflation in six dogs caused RC/AB with COS and CRU stimulations to change progressively from 0.53 +/- 0.07 (SE) and 0.03 +/- 0.05 at functional residual capacity (FRC) to -0.48 +/- 0.08 and -0.46 +/- 0.05 at 68% inspiratory capacity, respectively. Liquid substitution of abdominal contents in six other dogs equalized abdominal pressure swings (delta Pab), without changing chest wall elastic properties or geometry, or costal RC/AB (0.35 +/- 0.07 before and 0.33 +/- 0.06 after) but caused crural RC/AB to change from 0.01 +/- 0.05 to 0.31 +/- 0.01. We conclude that hyperinflation changes fiber orientation, allowing direct transmission of tension between COS and CRU, which become linked mechanically in series (the diaphragm acts as a unit with RC deflating action); and equalization of delta Pab causes indirect transmission of tension between COS and CRU, which become linked in series (the diaphragm acts as a unit with RC inflating action).

Abdomen↗
PubMed2004

Diaphragm electromyogram root mean square response to hypercapnia and its intersubject and day-to-day variation.

Diaphragm activation can be quantified by measuring the root mean square of crural EMG (RMSdi) (Beck J, Sinderby C, Lindstrom L, and Grassino A, J Appl Physiol 85: 1123-1134, 1998). To examine intersubject and day-to-day variation in the RMSdi-Pco(2) relationship, end-tidal Pco(2), minute ventilation (Ve), respiratory frequency (f(B)), and RMSdi were measured in seven healthy subjects on two occasions during steady-state ventilation at seven levels of inspired O(2) fraction (Fi(CO(2))) from 0 to 0.08 in random order. RMSdi was measured with a multielectrode esophageal catheter and controlled for signal contamination and diaphragm position. RMSdi was normalized for values obtained during quiet breathing at functional residual capacity, at Fi(CO(2)) of 0.04, and during an inspiratory capacity maneuver (RMSdi%max) as well as ECG R-wave amplitude at functional residual capacity (RMSdi/ECG(R)), f(B), and thickness of the costal diaphragm measured by ultrasound. RMSdi increased linearly with Pco(2) (mean r(2) = 0.83 +/- 0.10); at the highest Fi(CO(2)), RMSdi%max was 40.2 +/- 11.6%. Relative to the intersubject variation in the Ve-Pco(2) relationship, intersubject variations in the slopes and intercepts of the RMSdi-Pco(2) relationships were 1.7 and 1.8 times, respectively, and RMSdi%max-Pco(2) relationships 0.9 and 1.3 times, respectively, and were unrelated to f(B) and diaphragm thickness. Relative to the day-to-day variation in the Ve-Pco(2) relationship, day-to-day variation in the slopes and intercepts of the RMSdi-Pco(2) relationships were 2.8 and 4.4 times, respectively, and RMSdi/ECG(R)-Pco(2) relationships 1.3 and 2.2 times, respectively. It was concluded that the RMSdi-Pco(2) relationship measures chemosensitivity and is best compared between subjects via RMSdi%max and on separate occasions in the same subject via RMSdi/ECG(R).

Adult↗
PubMedDate not supplied

Prediction of some ventilatory 'norms' in healthy Indian males 21-69 years age.

This paper presents regression equations for predicting some ventilatory 'norms' (viz. vital capacity, forced vital capacity, forced expiratory volume for one second, expiratory reserve volume, inspiratory capacity and maximum voluntary ventilation) from physical characteristics of healthy Indian males. These equations have been constructed on the basis of multivariate regression analysis of the data of ventilatory 'norms' and physical characteristics collected on 171 healthy Indian males of age ranging from 21-69 years. Applications of these regression equations will be of practiced importance to biomedical scientists interested in the indirect assessment of ventilatory 'norms for a wider age range (21-69 years) which has not been covered by earlier studies carried out in this direction.

Adult↗
PubMed1975

[Respiratory functions in parkinsonian patients with predominant akinesia during treatment with decarboxylase-blocked L-dopa (author's transl)].

The effect of decarboxylase (DC)-blocked L-dopa (proportion of 4: 1) on respiratory function was tested by spirometry in 30 patients with Parkinson's disease. It was possible to improve restrictive ventilatory abnormalities of extra-pulmonary origin (weakness of respiratory musculature). Vital capacity (VC) increased by 0.21 litre. Thisincrease was due to a raised inspiratory capacity and thus an increase in the active part of ventilation. Forced expiration volume (FEV1) was improved by 0.32 litre, FEV1/VC remaining unchanged, which demonstrates that the restrictive ventilatory abnormality was affected. Inspiratory volume (VT) and minute volume at constant respiratory rate increased by 0.07 and 1.171, respectively. These results must be interpreted with caution, but they suggest a raised metabolic level with regained mobility during treatment. All quoted results, except those of respiratory rate and minute volume, were statistically significant (2 mu equals 0.01).

Adult↗
PubMed2001

Effect of fenestration on the sub-diaphragmatic venous hemodynamics in the total-cavopulmonary connection.

OBJECTIVE: To understand differences in the sub-diaphragmatic venous physiology between patients with fenestrated and non-fenestrated total-cavopulmonary connections (TCPC). METHODS: We studied the effects of respiration, retrograde flow, and gravity on the sub-diaphragmatic venous flows in 20 normal healthy volunteers (control), 25 Fontan patients with non-fenestrated TCPC, and 21 with fenestrated TCPC. Subhepatic inferior vena cava (IVC), hepatic vein (HV), and portal vein (PV) flow rates were measured with Doppler ultrasonography during inspiration and expiration in both supine and upright positions. The supine inspiratory-to-expiratory flow rate ratio was calculated to reflect the effect of respiration, the supine-to-upright flow rate ratio was calculated to assess the effect of gravity, and the magnitude of retrograde flow was evaluated with respect to total antegrade flow. Mean IVC, HV, and wedged hepatic venous (WHV) pressures were measured during cardiac catheterization in four TCPC patients before and after fenestration closure. The transhepatic venous pressure gradient (TVPG) was calculated as the difference between the HV and WHV pressure. RESULTS: Compared with control, HV flow in TCPC was heavily dependent on respiration; this inspiratory capacity was greater in fenestrated than non-fenestrated subjects (inspiratory-to-expiratory flow ratio 1.7, 4.4, and 3.0, respectively P<0.001). Normal retrograde HV flow was diminished in TCPC patients, furthermore, fenestrated subjects had less flow reversal than non-fenestrated (retrograde as percent of antegrade flow 43, 19, and 30%, respectively P<0.001). Gravity decreased IVC and HV flows more in TCPC subjects than control, but this effect was not different between the two TCPC groups. Closure of the fenestration resulted in higher IVC and HV pressures (pre-closure versus post-closure pressures [mmHg]: 11.2 +/- 4.0 vs. 12.3 +/- 3.9, and 11.5 +/- 3.8 vs. 12.4 +/- 3.8, respectively P< or =0.001). The normal TVPG was reduced in fenestrated TCPC, and worsened after fenestration closure (0.9 +/- 0.3 and 0.7 +/- 0.4, respectively P < 0.04). CONCLUSIONS: Fenestration of the inferior venous connection has important influences on sub-diaphragmatic venous return in TCPC patients. Although fenestration lowers venous pressures and partially restores TVPG, its beneficial effects on flow in TCPC patients are mediated primarily by an increase in inspiration-derived forward HV flow and reduced flow reversal. These observations suggest fenestration results in a more efficient and less congested splanchnic circulation in TCPC patients, and may have important implications in the early and late management of Fontan patients.

Blood Flow Velocity↗
PubMed1993

Preservation of sustainable inspiratory muscle pressure at increased end-expiratory lung volume.

Previous studies in isolated muscles have shown that decreases in muscle length reduce the loss of force resulting from fatigue in response to repeated maximal stimulations. However, increases in end-expiratory lung volume (EEV), which presumably decrease the length of the inspiratory muscles, appear to make the inspiratory muscles more susceptible to fatigue. To address this paradox, we studied the influence of changes in EEV on inspiratory muscle fatigue resulting from repeated maximal voluntary inspirations for 15 min in normal humans. Tidal volume and breath timing were constant between runs. Fatigue runs were compared with atmospheric, positive or negative pressures applied to the mouth, sufficient to change EEV by approximately +30% or -20% of inspiratory capacity. Although the maximal initial pressure-time product for the inspiratory muscles (PTmus) was reduced by increased EEV, sustainable PTmus was not significantly affected. In contrast, both initial and sustainable pressure-time products for the diaphragm were reduced at elevated EEV. The rate at which the fatigue process developed was also reduced at increased EEV. There were no significant effects of decreased EEV on any measured pressures. We conclude that when EEV is elevated, within a moderate range, sustainable inspiratory muscle pressure is preserved. However, the contribution of the diaphragm to inspiratory pressure development during fatigue may be uniquely compromised by increased EEV.

Adult↗
PubMed1990

Maximum inspiratory muscle endurance capacity during resistive loading in chronic obstructive pulmonary disease.

In 10 patients with stable severe chronic obstructive pulmonary disease (COPD) we evaluated the relationship between the degree of airway obstruction and hyperinflation, and the maximum inspiratory muscle endurance capacity during added inspiratory resistive loading. We measured the ratio of forced expiratory volume in 1 s to forced vital capacity (FEV1/FVC) and airway resistance (Raw) as indices of airway obstruction, and the ratio of functional residual capacity to total lung capacity (FRC/TLC) as an index of hyperinflation. The mean resting transdiaphragmatic pressure to its maximum (Pdi/Pdimax), the tension time index of the diaphragm, and the maximum transdiaphragmatic pressure (Pdimax) were also determined. Following 15 min of resting breathing, the patients breathed through added inspiratory resistances which were progressively increased every 3 min until exhaustion. Maximum endurance capacity (ECmax) was defined as the product of the esophageal pressure - time integral and frequency at the maximum load sustainable for 3 min. ECmax correlated significantly with Raw (r = -0.67, p less than 0.04). The addition of FRC/TLC to the analysis resulted in a significant increase in the correlation coefficient (r = 0.86, p less than 0.01). ECmax did not correlate with FEV1/FVC. Both resting Pdi/Pdimax and Pdimax independently influenced ECmax. In addition, Pdimax correlated significantly with FRC/TLC, and resting Pdi/Pdimax with Raw. We conclude that in stable patients with severe COPD, both airway obstruction and hyperinflation affect maximum inspiratory muscle endurance capacity during inspiratory resistive loading.

Aged↗
PubMed2001

Diaphragm activation during exercise in chronic obstructive pulmonary disease.

Although it has been postulated that central inhibition of respiratory drive may prevent development of diaphragm fatigue in patients with chronic obstructive pulmonary disease (COPD) during exercise, this premise has not been validated. We evaluated diaphragm electrical activation (EAdi) relative to maximum in 10 patients with moderately severe COPD at rest and during incremental exhaustive bicycle exercise. Flow was measured with a pneumotachograph and volume by integration of flow. EAdi and transdiaphragmatic pressures (Pdi) were measured using an esophageal catheter. End-expiratory lung volume (EELV) was assessed by inspiratory capacity (IC) maneuvers, and maximal voluntary EAdi was obtained during these maneuvers. Minute ventilation (V E) was 12.2 +/- 1.9 L/min (mean +/- SD) at rest, and increased progressively (p < 0.001) to 31.0 +/- 7.8 L/min at end-exercise. EELV increased during exercise (p < 0.001) causing end-inspiratory lung volume to attain 97 +/- 3% of TLC at end-exercise. Pdi at rest was 9.4 +/- 3.2 cm H(2)O and increased during the first two thirds of exercise (p < 0.001) to plateau at about 13 cm H(2)O. EAdi was 24 +/- 6% of voluntary maximal at rest and increased progressively during exercise (p < 0.001) to reach 81 +/- 7% at end-exercise. In conclusion, dynamic hyperinflation during exhaustive exercise in patients with COPD reduces diaphragm pressure-generating capacity, promoting high levels of diaphragm activation.

Diaphragm↗
PubMed1994

Lung volume specificity of inspiratory muscle training.

We examined the extent to which training-related increases of inspiratory muscle (IM) strength are limited to the lung volume (VL) at which the training occurs. IM strength training consisted of performing repeated static maximum inspiratory maneuvers. Three groups of normal volunteers performed these maneuvers at one of three lung volumes: residual volume (RV), relaxation volume (Vrel), or Vrel plus one-half of inspiratory capacity (Vrel + 1/2IC). A control group did not train. We constructed maximal inspiratory pressure-VL curves before and after a 6-wk training period. For each group, we found that the greatest improvements in strength occurred at the volume at which the subjects trained and were significantly greater for those who trained at low (36% for RV and 26% for Vrel) than at high volumes (13% for Vrel + 1/2IC). Smaller increments in strength were noted at volumes adjacent to the training volume. The range of vital capacity (VC) over which strength was increased was greater for those who trained at low (70% of VC) than at high VL (20% of VC). We conclude that the greatest improvements in IM strength are specific to the VL at which training occurs. However, the increase in strength, as well as the range of volume over which strength is increased, is greater for those who trained at the lower VL.

Adult↗
PubMed2000

Oxidative enzyme activities of the vastus lateralis muscle and the functional status in patients with COPD.

BACKGROUND: Enzymatic and histochemical abnormalities of the peripheral muscle may play a role in exercise intolerance in patients with chronic obstructive pulmonary disease (COPD). A study was undertaken to measure the mitochondrial enzyme activity of the vastus lateralis muscle in patients with COPD and to evaluate the relationship between enzyme activities and functional status. METHODS: Fifty seven patients with COPD of mean (SD) age 66 (7) years with forced expiratory volume in one second (FEV(1)) 39 (15)% predicted and peak oxygen uptake (VO(2)) of 14 (4) ml/min/kg and 15 normal subjects of similar age were included in the study. Each subject performed a stepwise exercise test up to maximal capacity during which five-breath averages of VO(2) were measured. Muscle specimens were obtained by percutaneous needle biopsy of the vastus lateralis muscle and the activity of two mitochondrial enzymes (citrate synthase (CS) and 3-hydroxyacyl CoA dehydrogenase (HADH)) was measured. The functional status of the patients was classified according to peak VO(2). RESULTS: CS and HADH activities were markedly reduced in patients with COPD compared with normal subjects (22.3 (2.7) versus 29.5 (7.3) micromol/min/g muscle (p<0.0001) and 5. 1 (2.0) versus 6.7 (1.9) micromol/min/g muscle (p<0.005), respectively). The activity of CS decreased progressively with the deterioration in the functional status while that of HADH was not related to functional status. Using a stepwise regression analysis, percentage predicted functional residual capacity (FRC), the activity of CS, oxygen desaturation during exercise, age, and inspiratory capacity (% pred) were found to be significant determinants of peak VO(2). The regression model explained 59% of the variance in peak VO(2) (p<0.0001). CONCLUSIONS: The oxidative capacity of the vastus lateralis muscle is reduced in patients with moderate to severe COPD compared with normal subjects of similar age. In these individuals the activity of CS correlated significantly with peak exercise capacity and independently of lung function impairment.

3-Hydroxyacyl CoA Dehydrogenases↗
PubMed1978

Physiological responses to head-out immersion in water at 11 ATA.

Cardiorespiratory, thermal, and renal responses to a 30-min head-out immersion in 15 degree C water were studied at 1-ATA air and 11-ATA helium-oxygne environments in four male subjects wearing dry suits. Cardiorespiratory responses to immersion (reductions in heart rate, expiratory reserve volume, vital capacity, and thoracic impedance; and increases in stroke volume, cardiac output, and inspiratory capacity) were comparable at both pressures. However, thermal responses to immersion (a reduction in mean skin temperature and increases in skin heat flux and suit conductance) were significantly greater at 11 ATA compared to those at 1 ATA. The rate of urinary excretion of norepinephrine increased significantly during and after immersion at 11 ATA but not at 1 ATA. In contrast, the urinary excretion of epinephrine was not altered by pressure or immersion. The immersion diuresis was greater and lasted longer at 11 ATA than at 1 ATA although there was no difference in the endogenous creatinine excretion . This diuresis was accompanied by a significant natriuresis which was more marked at 1 ATA than at 11 ATA. At 1 ATA, the urinary excretion of both aldosterone and antidiuretic hormone (ADH) decreased during immersion. At 11 ATA, the rate of excretion of these hormones before immersion was lower compared to that at 1 ATA and did not change significantly during immersion. These results indicate that immersion in a hyperbaric helium-oxygen environment presents a greater cold stress than at 1-ATA air, and also that immersion diuresis and natriuresis at high pressure may be induced by a factor other than inhibition of aldosterone and ADH.

Adult↗
PubMed2006

Pulmonary function at peak exercise in patients with chronic heart failure.

BACKGROUND: Various respiratory abnormalities are associated with chronic heart failure (CHF). However, changes in inspiratory capacity (IC) and breathing pattern from rest to exercise in patients with CHF have not been thoroughly investigated in these patients. MATERIALS AND METHODS: Seventy seven (66 male/11 female) patients with clinical stable CHF (age: 52+/-11 years) were studied. All the patients underwent pulmonary function tests, including measurements of IC and maximal inspiratory pressure (Pimax) at rest and then a maximal cardiopulmonary exercise testing (CPET) on a treadmill. During the CPET, IC was measured every 2 min. Pimax was measured again after the end of CPET. RESULTS: Percent predicted forced expiratory volume in 1 s (FEV1) was 91+/-12, %predicted forced vital capacity (FVC) was 92+/-13, %FEV1/FVC was 81+/-4, and %predicted IC was 85+/-18. Peak exercise IC was lower than resting (2.4+/-0.6 vs. 2.6+/-0.6 l, p<0.001). Analysis of variance between Weber's groups revealed statistically significant differences in peak exercise IC (p<0.001), VE/VCO2slope (p<0.001), resting Pimax (p=0.005) and post-exercise Pimax (p<0.001). At rest, there was a statistically significant difference in end-tidal CO2 (P(ETCO2)) (p=0.002), in breathing frequency (p=0.004), in inspiratory time (Ti) (p=0.04) and in total respiratory time (T(Tot)) (p=0.004) among Weber's groups. At peak exercise there was a statistically significant decrease in minute ventilation (VE) (p<0.001), tidal volume (VT) (p<0.001), respiratory cycle (VT/TI) (p<0.001) and P(ETCO2) (p<0.001). Peak IC was correlated with peak VO2 (r=0.72, p<0.001), anaerobic threshold (r=0.71, p<0.001), VO2/t slope (r=0.54, p<0.0001), and post-exercise Pimax (r=0.62, p<0.001). CONCLUSIONS: In patients with CHF, peak exercise IC is reduced in parallel with disease severity, which is probably due to respiratory muscle dysfunction.

Anaerobic Threshold↗