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PubMed1997

[Pressure versus volume constant ventilation in chronic ventilatory insufficiency].

BACKGROUND: Volume controlled intermittent ventilation (IPPV) via face mask is a treatment of proven efficacy for chronic respiratory failure (CRF). Pressure support ventilation has recently been introduced in the treatment of CRF. In this study we investigated whether pressure constant ventilation (PCV) via face mask could be an adequate long term alternative to IPPV. PATIENTS AND METHODS: We studied 30 (24 male, age: 52.2 +/- 15.9 years) patients with CRF. We measured the following parameters at baseline, after 1, 2 and 6 months, respectively: blood gas analysis, oxygen saturation, vital capacity, forced exspiratory volume, breathing frequency, tidal volume, inspiratory mouth occlusion pressure, maximal inspiratory pressure, subjective symptom scores and ventilator acceptance scores. In all patients, we attempted to treat with IPPV over 1 month, followed by 1 month's trial of PCV. If PCV, compared to IPPV, was adequate, PCV was continued for a follow-up period of 4 months' duration. If patients deteriorated after PCV they were treated the following 4 months with IPPV. RESULTS: In 28 out of 30 patients CRF improved concerning subjective and objective parameters. After IPPV 18 out of 28 patients changed to PCV, with an equal quality of treatment (PCV-responder). Ten patients were PCV-nonresponders since compared to IPPV the subjective scores deteriorated and the PaCO2 increased again. In all patients of either therapy group, subjective and objective parameters remained constant for another 4 months period. At baseline the PCV-nonresponders had significantly higher degree of hypercapnia and oxygen desaturation; no other parameters were found to be of predictive value concerning the efficacy of PCV. CONCLUSIONS: PCV proved to be an alternative to IPPV in the treatment of chronic respiratory insufficiency in approximately 60% of the patients with CRF. However there is a subgroup with more severe CRF at baseline in whom PCV is inadequate.

Adult↗
PubMed1976

[Pathophysiology of respiratory disturbances in children (author's transl)].

Physiological conditions of respiration in children are defined especially by - relative hyperventilation because of high oxygen uptake per body surface, - relative narrow and soft airways with high tendency to obstruction, causing atelectasis, pneumonia or severe bronchiolitis. It is useful to differentiate between bronchiolitis and spastic or asthmatoid bronchitis, the latter being sensible to Adrenalin and developing to asthma of adults. Characteristical signs of asthmatoid bronchitis are bronchial hyperreactivity, increased airway-resistance and residual volume, decreased FEV 1, pulmonary compliance, arterial PO2 and PCO2 with signs of pulmonary inhomogeneity. Mucviscidosis, starting from abnormal viscosity of bronchial secretion, is functionally characterized by similar signs, so are increased RV with air-trapping, decreased FEV 1, VC, PO2a and pulmonary inhomogeneity. Diffuse progressive interstitial pulmonary fibrosis (HAMMAN-RICH) of acute type being mostly lethal in children up to 2 years of age and of subacute type in older children shows diffusion disturbance and characteristical ventilation disturbance with reduction of inspiratory reserve volume and enlargement of functional residual capacity but normal FEV 1. Disturbances are sensible to corticoid-therapy.

Age Factors↗
PubMed1982

Mechanism of production of crackles after atelectasis during low-volume breathing.

We compared the effects of shallow breathing of air (LVB-air) and oxygen (LVB-O2) at low lung volumes (below closing capacity) and tidal breathing at FRC (FRC-air, FRC-O2) on the production of crackles in 5 normal volunteers. Two microphones were attached on the right posterior chest wall in the midclavicular line 10 and 20 cm from the apex of the right lung, respectively (M10 and M20), to record crackles during various breathing maneuvers. We found that after LVB-air and LVB-O2, there were changes in residual volume as measured by the body plethysmograph. Both inspiratory and expiratory limbs of the quasi-static pressure volume curve were shifted to the right. Occasionally, some subjects coughed after LVB-air and/or LVB-O2. Inspiratory crackles occurred mostly at the upper third of vital capacity (VC) after LVB-air and LVB-O2 and were confined almost exclusively to the dependent lung zones (M20). The inspiratory transpulmonary pressure at 25% (PL25) and 50% (PL50) of VC correlated with the volume of trapped gas that was absorbed (delta Vtg) (p less than 0.001 and p less than 0.001, respectively). The quantity of crackles correlated with delta Vtg (p less than 0.01). We conclude that during low lung volume breathing airways in the dependent lung regions are closed. There is absorption of trapped oxygen which causes reversible atelectasis. Upon reinflation, inspired air will go to the lung regions with open airways first and subsequently to the closed dependent regions, producing crackles recorded by the M20 microphone at the upper third of VC. The crackles are produced by inflation of atelectatic lung.

Air↗
PubMed1979

Ventilatory control in patients with hypoxemia due to obstructive lung disease.

In 20 patients with chronic hypoxemia due to chronic obstructive pulmonary disease, we measured responses to CO2 and hypoxia in terms of ventilation and P0.1, the pressure generated by the respiratory muscles during the first 0.1 s of inspiratory effort against a closed airway at functional residual capacity. These responses were compared to those of a control group of 17 patients with similar ventilatory abnormality but without hypoxemia. Hypoxemic patients demonstrated significantly less response to hypoxia than did control subjects in terms of both ventilation and P0.1 The decreased hypoxic response might be analogous to that reported in high altitude dwellers and patients with cyanotic congenital heart disease. Ventilatory responses to CO2 were depressed in hypoxemic patients, but P0.1 responses were not significantly decreased. While breathing at rest with arterial O2 saturation of 95 per cent, hypoxemic patients demonstrated the same minute ventilation as control subjects, but tidal volume was smaller, inspiratory duration was shorter, and breathing frequency was slightly higher. This breathing pattern appeared to be independent of whether or not these patients retained CO2.

Carbon Dioxide↗
PubMed1985

Pressure-time product, flow, and oxygen cost of resistive breathing in humans.

We examined the relationship between the pressure-time product (Pdt) of the inspiratory muscles and the O2 cost of breathing (VO2 resp) in five normal subjects breathing through an external inspiratory resistance with a tidal volume of 800 ml at a constant end-expiratory lung volume [functional residual capacity, (FRC)]. Each subject performed 30-40 runs, each of approximately 30 breaths, with inspiratory flow rates ranging from 0.26 +/- 0.01 to 0.89 +/- 0.04 l/s (means +/- SE) and inspiratory mouth pressures ranging from 10 +/- 1 to 68 +/- 4% of the maximum inspiratory pressure at FRC. In all subjects VO2 resp was linearly related to Pdt when mean inspiratory flow (VI) was constant, but the slope of this relationship increased with increasing VI. Therefore, Pdt is an accurate index of VO2 resp only when VI is constant. There was a linear relationship between the VO2 resp and the work rate across the external resistance (W) for all runs in each subject over the range of W 10 +/- 1 to 137 +/- 21 J/min. Thus, at a constant tidal volume the VO2 resp was related to the mean inspiratory pressure, independent of flow or inspiratory duration. If the VO2 resp were determined mainly during inspiration, then for a given rate of external work or O2 consumption, VI would be inversely related to mean inspiratory pressure. Efficiency (E) was 2.1 +/- 0.2% and constant over a large range of VI, pressure, work rate, or resistance and was not altered by the presence of a potentially fatiguing load. The constant E over such a wide range of conditions implies a complex integration of the recruitment, mechanical function, and energy consumption of the muscles utilized in breathing.

Adult↗
PubMed1991

Effect of an endurance triathlon on pulmonary function.

We assessed the effect of an endurance triathlon consisting successively of a 3.8-km swim, a 180-km bicycle ride, and a 42-km run on the forced expiratory spirogram, indices of inspiratory and expiratory muscle strength (PImax and PEmax), and maximal voluntary ventilation (MVV). Twelve male participants were recruited from competitors in the Cape Cod Endurance Triathlon and underwent studies on the afternoon before the event, after each segment, and on the following morning. Participants averaged 32.9 yr of age. All completed the triathlon with an average finishing time of 12 h 45 +/- 90 min. Following completion of the triathlon, statistically significant declines occurred in FVC (7.1%), FEV1 (8.4%), FEF25-75% (15.2%), and FEF50% (18.6%), but not in MVV. On the morning after the triathlon, only FEV1 remained significantly below baseline. PImax was not significantly reduced after the swim, but significant reductions did occur after the bicycle and running events (26% and 25%, respectively); full recovery had occurred by the following morning. PEmax did not change significantly. We conclude that vital capacity, flow rates at mid-lung volumes, and inspiratory muscle strength decline as a consequence of participation in a triathlon.

Adult↗
PubMed1998

Relationship between external resistances, lung function changes and maximal exercise capacity.

In upper airway obstruction (UAO) the relationship between the degree of obstruction, exercise limitation and lung function indices is not well established. Therefore, we investigated in nine healthy subjects (age 36+/-9 yrs) the effects of two added resistances at the mouth (R1 = added resistance with 7.8 mm diameter; R2 = 5.7 mm) on forced expiratory volume in one second (FEV1), peak expiratory flow (PEF), airway resistance (Raw) and maximal breathing capacity (measured during 15 s = measured maximum breathing capacity (MBCm); calculated as FEV1x37.5 = calculated maximum breathing capacity (MBCc)) on the one hand, and maximum exercise capacity (W'max), minute ventilation (V'E) and CO2 elimination (V'CO2) on the other. We found that R1 had almost no influence on FEV1 but decreased PEF by approximately 35% and increased Raw by almost 300%; it decreased W'max by merely approximately 10% while maximal exercise ventilation (V'Emax) was only 65% of control and only reached approximately 40% MBCc and approximately 70% MBCm; yet V'E and V'CO2 were significantly reduced at high exercise levels indicating hypoventilation. With R2, FEV1 was reduced by 25% and PEF by 55%, and Raw was increased by 600%; W'max was approximately 60% of control, V'Emax was only 35% of control and reached approximately 30% MBCc and approximately 60% MBCm, V'E was already reduced at moderate exercise levels. We conclude that: 1) an upper airway obstruction of 6 mm diameter (but not of 8 mm) had a marked influence on maximum exercise capacity due to hypoventilation; 2) calculated maximum breathing capacity markedly overestimated measured maximum breathing capacity because the forced expiratory volume in one second is an insensitive index of upper airway obstruction and because it does not take inspiratory flow limitation into account; and 3) a 10% decrease in maximum exercise capacity was linearly related with a 7% decrease in the forced expiratory volume in one second and a 150% increase in airway resistance. A 10% decrease in maximal exercise ventilation was related to a 8.5% decrease in peak expiratory flow and 9% decrease in measured maximum breathing capacity.

Adult↗
PubMed1987

Weaning from mechanical ventilation: successful use of modified inspiratory resistive training in muscular dystrophy.

An 18-yr-old man with Duchenne muscular dystrophy and ventilatory failure could not be weaned from mechanical ventilation using a T-piece method, despite repeated attempts over 3 months. Subsequently, we weaned the patient using inspiratory muscle resistive training (IRT), modified by the concurrent delivery of intermittent mandatory ventilation (IMV). During the training program, the sessions were gradually prolonged from 5 min to a maximum of 30 min, the IMV rate was gradually decreased, and the magnitude of the resistive load was gradually increased. After 45 days of training, his vital capacity had increased from 380 to 850 ml, his maximal inspiratory airway pressure from -28 to -50 cm H2O, and his tolerance of T-piece breathing, from less than 10 min to over 16 h. After an additional 2 wk of nocturnal mechanical ventilation, he was successfully weaned. We conclude that IRT with IMV can be an effective method of weaning patients who have severe ventilatory failure.

Adolescent↗
PubMed1999

[Effect of specific inspiratory muscle training on dyspnea and exercise tolerance in congestive heart failure].

It has been shown that the inspiratory muscles of patients with congestive heart failure (CHF) are weaker than normal. This weakness may contribute to dyspnea and limit exercise capacity. But respiratory muscles can be trained for increase in both strength and endurance. This study was designed to evaluate the effect of specific inspiratory muscle training (SIMT) on muscular performance, lung function, dyspnea and exercise capacity in moderate heart failure. 10 patients with CHF (NYHA functional class II-III) received 1/2 hour of SIMT daily, 6 times/week, for 3 months. They started breathing at a resistance 15% of their Pimax for 1 week and the resistance was then increased incrementally to 60%. Spirometry, inspiratory muscle strength and endurance, and the 12-minute walk test were performed before and after the training period. All showed an increase in inspiratory muscle strength and endurance. This was associated with a small but significant increase in FVC, a significant increase in the distance walked (458 +/- 29 to 562 +/- 32 m, p < 0.01), and improvement in the dyspnea index score. SIMT resulted in increased inspiratory muscle strength and endurance. This increase was associated with decreased dyspnea and an increase in submaximal exercise capacity. SIMT may prove to be useful complementary therapy in CHF.

Aged↗
PubMed2005

Disability and breathlessness in asthmatic patients--a scoring method by repetitive inspiratory effort.

Measurement of disability and breathlessness in asthma is important to guide treatment. Using an incentive spirometer, Triflo II (Tyco Healthcare, Mansfield, MA, USA), we developed a three-minute respiratory exercise test (3-MRET) to score the maximal breathing capacity (MBC) and perception of dyspnea (POD) index by means of repetitive inspiratory efforts achieved within 3 minutes. POD index was calculated based on the ratio of breathlessness on visual analogue scale over MBC score. In 175 normal healthy subjects and 158 asthmatic patients of mild (n = 26), moderate (n = 78), and severe (n = 54), severity, the mean (95% CI) MBC scores in mild, moderate, and severe asthma patients were 168 (145-192), 153 (136-169), and 125 (109-142) respectively, and 202 (191-214) in normal subjects (p < 0.001). The mean POD index in mild, moderate, and severe asthma patients was 16 (9-23), 25 (14-37), and 57 (14-100), respectively, and 6 (4-7) in normal subjects (p < 0.001). Intraclass correlation coefficients for MBC score and POD index in 17 asthmatic and 20 normal subjects were high. In 14 asthmatic patients randomized to receiving nebulized beta2-agonist or saline in a cross-over, double-blind study, % forced expiratory volume in one second (FEV1) change correlated with % change in MBC score [r(s) = 0.49, p < 0.01] and POD index [r(s)-0.46, p = 0.012]. In 21 asthmatic and 26 normal subjects, the MBC score and POD index correlated with the walking distance and walking POD index of the six-minute walking test (6MWT). We conclude that 3MRET is discriminative between asthmatic patients of varying severity and normal subjects, is reproducible, is responsive to bronchodilator effect, and is comparable with 6MWT. Taken together, it has the potential to score disability and POD in asthma simply and effectively.

Adrenergic beta-Agonists↗
PubMed1999

The effect of specific inspiratory muscle training on the sensation of dyspnea and exercise tolerance in patients with congestive heart failure.

BACKGROUND: It has been previously shown that the inspiratory muscles of patients with congestive heart failure (CHF) are weaker than those of normal persons. This weakness may contribute to the dyspnea and limit exercise capacity in these patients. The respiratory muscles can be trained for both strength and endurance. HYPOTHESIS: The present study was designed to evaluate the effect of specific inspiratory muscle training (SIMT) on inspiratory muscle performance, lung function, dyspnea, and exercise capacity in patients with moderate heart failure. METHODS: Twenty patients with CHF (NYHA functional class II-III) were recruited for the study. The subjects were randomized into two groups: 10 patients were included in the study group and received SIMT and 10 patients were assigned to the control group and received sham training. Subjects in both groups trained daily, 6 times/week, for one-half h, for 3 months. The subjects started breathing at a resistance equal to 15% of their PImax for 1 week and the resistance was then increased incrementally to 60%. Spirometry, inspiratory muscle strength (assessed by measuring the PImax at residual volume), and endurance (expressed by the relationship between PmPeak and PImax), the 12-min walk test, and peak VO2 were performed before the beginning and at the end of the training period. RESULTS: All patients in the training group showed an increase in the inspiratory muscle strength [mean (+/- standard error of the mean) PImax increased from 46.5 +/- 4.7 to 63.6 +/- 4.0 cm H2O, p < 0.005], and endurance (mean PmPeak/PImax from 47.8 +/- 3.6 to 67.7 +/- 1.7%, p < 0.05), while they remained unchanged in the control group. This was associated in the training group with a small but significant increase in forced vital capacity, a significant increase in the distance walked (458 +/- 29 to 562 +/- 32 m, p < 0.01), and an improvement in the dyspnea index score. No statistically significant change in the mean peak VO2 was noted in either group. CONCLUSIONS: Specific inspiratory muscle training resulted in increased inspiratory muscle strength and endurance. This increase was associated with decreased dyspnea, increase in submaximal exercise capacity, and no change in maximal exercise capacity. This training may probe to be a complementary therapy in patients with congestive heart failure.

Aged↗
PubMed1987

Flow-volume loop changes reflecting respiratory muscle weakness in chronic neuromuscular disorders.

In order to identify the changes in pulmonary function and in the flow-volume loop due to respiratory muscle weakness, two groups of 10 nonsmokers with stable, chronic neuromuscular disease but without respiratory symptoms were studied: one without (Group 1) and one with (Group 2) respiratory muscle weakness as assessed by measurement of maximal static inspiratory and expiratory pressures. In Group 1, pulmonary function was normal except for increased ratio of one-second forced expiratory volume to forced vital capacity and forced expiratory flow at 25 to 75 percent forced vital capacity, which may reflect increased elastic lung recoil. Group 2 had mild volume restriction, appropriate for the degree of respiratory muscle weakness, and reduced inspiratory and expiratory flow rates. Pulmonary function was significantly more disturbed in Group 2 than in Group 1, and correlated well with maximal static inspiratory and expiratory pressures. Analysis of the flow-volume loop configuration revealed that four parameters describing effort-dependent portions were significantly related to maximal static inspiratory pressure and maximal static expiratory pressure. These parameters were peak expiratory flow, the slope of the ascending limb of the maximal expiratory curve, a drop of forced expiratory flow near residual volume, and forced inspiratory flow at 50 percent of vital capacity. A flow-volume loop score obtained from these four parameters was significantly higher in Group 2 than in Group 1 (2.8 +/- 1.03 versus 1.1 +/- 1.37; p less than 0.01). A flow-volume loop score of 2 or more had 80 percent specificity and 90 percent sensitivity in predicting respiratory muscle weakness in these patients with chronic neuromuscular disease. These data suggest that sensitive assessment of the flow-volume loop configuration as part of routine pulmonary function testing may help to suspect and identify respiratory muscle weakness.

Chronic Disease↗
PubMed1997

Effect of upper respiratory tract infection in patients with neuromuscular disease.

Respiratory muscle strength during acute upper respiratory tract infection (URI) was assessed in patients with various forms of neuromuscular disease. Vital capacity (VC), oxygen saturation, end-tidal PCO2, maximal inspiratory pressure (MIP), and maximal expiratory pressure (MEP) were determined in 25 stable patients with various forms of neuromuscular disease. Thirteen episodes of URI developed in 10 patients. Respiratory parameters were reassessed within 24-36 h following the onset of symptoms in each patient. In patients with URI, mean baseline VC, MIP, and MEP were 1.16 L +/- 0.14, 49.2 cm H2O +/- 6.8, and 35.5 cm H2O +/- 3.8 and fell to 1.01 L +/- 0.15, 37.1 cm H2O +/- 6.2, and 25.5 cm H2O +/- 3.0 during URI (p < 0.05 for each), respectively. Mean baseline PCO2 and oxygen saturation were 39.1 mm Hg +/- 1.1 and 95.1% +/- 1.0, and during URI, 43.9 mm Hg +/- 2.1 (p < 0.05) and 95.0% +/- 1.0 (NS), respectively. Five episodes of significant hypercapnia were observed in 4 patients. All parameters returned to near baseline values following recovery. We conclude that patients with various forms of neuromuscular disease develop reductions in respiratory muscle strength in association with URI. Unlike normal subjects, however, these decrements in respiratory muscle function may result in symptoms of shortness of breath, reductions in vital capacity, and acute hypercapnia in this patient population.

Acute Disease↗
PubMed2005

The 1-year impact of severe acute respiratory syndrome on pulmonary function, exercise capacity, and quality of life in a cohort of survivors.

OBJECTIVE: To examine pulmonary function, exercise capacity, and health-related quality of life (HRQoL) among severe acute respiratory syndrome (SARS) survivors. METHODS: We evaluated survivors with confirmed SARS at the Prince of Wales Hospital, Hong Kong, at 3, 6, and 12 months after symptom onset. Our assessment included: lung volume (total lung capacity [TLC], vital capacity, residual volume, functional residual capacity), spirometry (FVC, FEV1), diffusing capacity of the lung for carbon monoxide (D(LCO)), inspiratory and expiratory respiratory muscle strength, 6-min walk distance (6MWD), chest radiographs (CXRs), and HRQoL by Medical Outcomes Study 36-Item Short-Form General Health Survey questionnaire. RESULTS: Ninety-seven patients completed the serial assessments. There were 39 male and 58 female patients, and 63 patients (70%) were health-care workers (mean age, 36.9 years [SD, 9.5 years]; body mass index, 23.7 kg/m2 [SD, 4.0 kg/m2]). At 1 year, 27 patients (27.8%) had abnormal CXR findings. Four patients (4.1%), 5 patients (5.2%), and 23 patients (23.7%) had FVC, TLC, and D(LCO) values < 80% of predicted values, respectively. The 6MWD at 12 months was 511.0 m (SD, 89.8 m), which was higher than at 3 months (mean difference, 47.0 m; 95% confidence interval [CI], 31.8 to 62.1 m; p < 0.01) but not different from 6 months (mean difference, 9.7 m; 95% CI, - 4.4 to 23.8 m; p = 0.18). The 6MWD was lower than that for normal control subjects of the same age groups, and there was impairment of HRQoL at 12 months. Patients who required ICU admission (n = 31) showed higher CXR scores (1.6 [SD, 3.1]; vs 0.4 [SD, 1.1]; p = 0.04) and lower percentage of predicted FVC, TLC, and Dlco than those who did not, but there were no differences in 6MWD and health status. CONCLUSION: Significant impairment in Dlco was noted in 23.7% of survivors 1 year after illness onset. Exercise capacity and health status of SARS survivors were remarkably lower than those of a normal population.

Adult↗
PubMed1985

Phrenic and diaphragm function after coronary artery bypass grafting.

We studied respiratory mechanics and phrenic nerve and diaphragm function in 12 patients on the day before and eight to 13 days after coronary artery bypass grafting. The average vital capacity, functional residual capacity, and total lung capacity decreased by 20.5%, 9.5%, and 14.7% respectively after operation. Eleven patients showed less negative maximum inspiratory mouth pressures at any given lung volume after surgery and the magnitude of the change correlated with the reduction in total lung capacity. In 11 of the 12 patients the conduction times of the right and left phrenic nerves did not change substantially after operation and the ratio of inspiratory electrical activity (Edi) of left and right hemidiaphragms was similar before and after the procedure. One patient, however, showed a considerable increase in left phrenic nerve conduction time and a reduction in the left to right Edi ratio postoperatively. In three patients diaphragm function was also assessed by changes in transdiaphragmatic pressure during supramaximal phrenic nerve stimulation and voluntary increase in inspired volume; in none of the three patients did the transdiaphragmatic pressure swings show any significant change in the postoperative period. These data indicate that phrenic nerve paralysis only occasionally accounts for the postoperative loss of lung volume after coronary artery bypass grafting surgery. The mechanism of these abnormalities therefore remains to be determined.

Coronary Artery Bypass↗
PubMed1989

[Volume, flow and respiratory muscle strength in mitral stenosis].

Pulmonary function and respiratory muscle strength was assessed in 20 patients with mitral stenosis uncomplicated by other illness. Pulmonary function was evaluated by spirometry, flow-volume curves, functional residual capacity (FRC) and total lung capacity (TLC). Respiratory muscle strength was evaluated by measurement of maximal static inspiratory and expiratory mouth pressure (PIM, PEM cmH2O) at FRC and TLC respectively. Spirometric, FRC and TLC average values were normal. The maximal expiratory flow rate at 50 and 25% of vital capacity were decreased to 49.5 and 38.3% from predicted values. The values of PIM and PEM in patients (-93 +/- 17; 128 +/- 32 cmH2O, respectively) were similar to those of 12 normal subjects studied at comparable lung volume. Our results were similar to previous reports. There was no evidence of decreased respiratory muscle force, probably because the patients nutritional status and cardiac output were normal.

Adolescent↗
PubMed1990

Effects of expiratory resistive loading on the sensation of dyspnea.

To determine whether an increase in expiratory motor output accentuates the sensation of dyspnea (difficulty in breathing), the following experiments were undertaken. Ten normal subjects, in a series of 2-min trials, breathed freely (level I) or maintained a target tidal volume equal to (level II) or twice the control (level III) at a breathing frequency of 15/min (similar to the control frequency) with an inspiratory load, an expiratory load, and without loads under hyperoxic normocapnia. In tests at levels II and III, end-expiratory lung volume was maintained at functional residual capacity. A linear resistance of 25 cmH2O.1(-1).s was used for both inspiratory and expiratory loading; peak mouth pressure (Pm) was measured, and the intensity of dyspnea (psi) was assessed with a visual analog scale. The sensation of dyspnea increased significantly with the magnitude of expiratory Pm during expiratory loading (level II: Pm = 9.4 +/- 1.5 (SE) cmH2O, psi = 1.26 +/- 0.35; level III: Pm = 20.3 +/- 2.8 cmH2O, psi = 2.22 +/- 0.48) and with inspiratory Pm during inspiratory loading (level II: Pm = 9.7 +/- 1.2 cmH2O, psi = 1.35 +/- 0.38; level III: Pm = 23.9 +/- 3.0 cmH2O, psi = 2.69 +/- 0.60). However, at each level of breathing, neither the intensity of dyspnea nor the magnitude of peak Pm during loading was different between inspiratory and expiratory loading. The augmentation of dyspnea during expiratory loading was not explained simply by increases in inspiratory activity. The results indicate that heightened expiratory as well as inspiratory motor output causes comparable increases in the sensation of difficulty in breathing.

Adult↗
PubMed1989

Exercise performance of hemodialysis patients during short-term and prolonged exposure to altitude.

The work capacity of patients on maintenance hemodialysis is impaired even at normal inspiratory oxygen pressure. A further restriction can be expected when these patients are exposed to hypoxia at altitude, since most of the usual compensatory mechanisms required to adjust to this environment are impaired or even missing. We tested the tolerance of hemodialysis patients to hypoxia and measured work capacity, hematological, and cardiovascular parameters at rest and during incremental bicycle ergometry during 3-hour exposure to altitudes of 2,000 m and 3,000 m, and during 2 weeks of exposure to an altitude of 2,000 m and compared these data with prealtitude values or with data evaluated in a control group, respectively. In control tests the patients reached work loads at exercise termination of about 66% of age and sex-matched healthy controls, the reduction correlated well with the degree of anemia. During short-term altitude exposure to 2,000 m peak work performance remained unchanged in comparison to prealtitude tests, whereas at 3,000 m it was reduced by about 12%. During the 2-week stay at 2,000 m peak work loads increased significantly by 17% accompanied by an increase in peak oxygen uptake (+15%), blood lactate, heart rates (+10 min-1), and systolic blood pressure (+20 mmHg), whereas the diastolic pressure was comparable to prealtitude values. In another group of hemodialysis patients studied at low altitude under similar experimental conditions none of these parameters was changed. Our data show that during acute exposure to altitudes up to 2,000 m maximal work of hemodialysis patients is not reduced, but is restricted at altitudes higher than that.(ABSTRACT TRUNCATED AT 250 WORDS)

Acclimatization↗