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Results for “Maximal Voluntary Ventilation”

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At least 19 recordsLinked to original sources

PubMed1988

Supine position and sleep loss each reduce prolonged maximal voluntary ventilation.

Because of the prevalence of supine posture and sleep deprivation in both health and disease, we wondered how each of them influences prolonged maximal voluntary ventilation (MVV). Accordingly, we compared 12-second, 1-min, and 10-min isocapnic MVV supine with that measured in the upright posture in 8 healthy subjects. MVV decreased 6-10% supine, independent of test duration (p less than 0.01). Although end-expiratory lung volume was 0.47 liter lower during supine resting breathing (p less than 0.001), end-expiratory lung volumes during short-term MVV maneuvers were identical. To investigate any additional effect on MVV due to sleep loss, 12 healthy subjects performed 12-second, 1-min, and 30-min isocapnic MVV maneuvers in the supine position, either after normal sleep or after a 24-hour sleepless period. Sleep deprivation reduced MVV by 7-14%, again independent of test duration (p less than 0.05). Sleep loss also reduced the ventilation chosen to represent a submaximal (75%) breathing effect (p = 0.05), and it increased subjective ratings of fatigue and confusion (p less than 0.01). We conclude that supination and sleep deprivation together decrease both short- and long-term MVV by nearly 20%, with impairment of supination not caused by lung volume changes, and with the sleep loss effect occurring in tandem with a rise in the subjective assessment of breathing effort.

Adult↗

PubMed1988

Discontinuation of mechanical ventilation.

The vast majority of patients who undergo mechanical ventilation are able to discontinue ventilatory assistance within a few days. Typically, patients who require only short-term mechanical ventilation do not have severe underlying lung disease, and the problem for which they require ventilatory support is most commonly rapidly reversible. In these patients on short-term ventilatory support, parameters of spontaneous ventilatory requirements and respiratory muscle strength, including minute ventilation, maximal voluntary ventilation, vital capacity, and maximal inspiratory pressure, are useful in predicting the success of discontinuation of mechanical ventilation. Ventilatory support can generally be discontinued by a variety of techniques in these patients without the need for weaning from the ventilator per se. The smaller group of patients in whom it is not possible to discontinue mechanical ventilation within less than 7 days comprises individuals who frequently have severe acute or chronic lung disease, multisystem extrapulmonary disease, or neuromuscular disease. After a period of prolonged mechanical ventilatory support, these complicated patients require a process of progressive weaning in which they gradually become able to support spontaneous ventilation. Spontaneous ventilatory parameters do not correlate well with weaning ability in patients on long-term ventilatory support. A systematic and comprehensive approach in which attention is focused on optimizing pulmonary and nonpulmonary factors that affect the weaning process provides the best chance for successful withdrawal of ventilatory support after long-term mechanical ventilation. Inadequate ventilatory drive, respiratory muscle weakness and fatigue, increased work of breathing, excessive CO2 production, and cardiac failure are potential mechanisms that may play a role in inhibiting successful weaning. Adverse factors relevant to each of these mechanisms must be addressed and corrected to whatever extent possible. Studies have not demonstrated the superiority of either classic T-piece weaning or IMV weaning methods in difficult-to-wean patients on long-term ventilatory support. Both techniques may be used successfully as long as all patient variables that may adversely affect weaning ability are corrected or optimized and close care and attention to the details of the weaning process itself are provided.(ABSTRACT TRUNCATED AT 400 WORDS)

Heart Failure↗

PubMed1987

Effects of intermittent negative pressure ventilation on respiratory muscle function in patients with severe chronic obstructive pulmonary disease.

The reduced respiratory muscle strength and increased work of breathing in patients with severe chronic obstructive pulmonary disease (COPD) may predispose these patients to the development of respiratory muscle fatigue and consequent respiratory failure. To test the hypothesis that these patients may be experiencing chronic respiratory muscle fatigue, we studied the effects of resting the respiratory muscles in a group of patients with severe COPD. Fifteen stable patients with severe COPD were randomized into study and control groups. In 8 study group patients (Group B), breathing was assisted with a negative pressure ventilator 3 to 6 h daily for 3 consecutive days. The remaining 7 patients served as controls (Group A) and did not receive any intervention. Baseline lung function was evaluated by spirometry and arterial blood gas determinations. Respiratory muscle strength and endurance were evaluated by maximal inspiratory and expiratory pressures (MIP and MEP, respectively) and the maximal duration that isocapnic hyperventilation equal to 50 and 70% of the 12-s maximal voluntary ventilation could be sustained (DSV). Baseline DSV was determined as the best effort of several practice trials. All measurements were repeated on the final day of assisted ventilation approximately 2 to 3 h after its discontinuation. After assisted ventilation, the DSV at 50 and 70% of the maximal voluntary ventilation improved significantly (p less than 0.05). Maximal inspiratory pressure and MEP increased to 114% (p less than 0.05) and 112% (p = 0.05) of baseline values, respectively. Mean arterial PCO2 in the hypercapnic subgroup of Group B patients decreased from 60 mm Hg before to 52 mm Hg after assisted ventilation (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Carbon Dioxide↗

PubMed1988

Impaired exercise tolerance after inferior vena caval interruption.

Four patients were evaluated for persistent dyspnea eight months to four years after inferior vena caval interruption for treatment of pulmonary emboli. Maximal exercise testing with gas-exchange analysis was performed. All patients attained less than 64 percent of predicted maximal oxygen uptake. Peak exercise heart rates were 85 percent or greater of predicted values. Arterial hypoxemia was not observed. The ratio of dead space to tidal volume (VD/VT) decreased with exercise, and the ratios of maximal exercise ventilation to maximal voluntary ventilation (VE/MVV) were less than 67 percent. These results suggest a cardiac rather than a ventilatory limitation to exercise. Inadequate venous blood return to the heart is the likely mechanism for the impaired exercise performances.

Adult↗

PubMed1991

Inspiratory muscle relaxation rate after voluntary maximal isocapnic ventilation in humans.

We have investigated whether the capacity of the inspiratory muscles to generate pressure and flow during a ventilatory load is related to changes in inspiratory muscle relaxation rate. Five highly motivated normal subjects performed voluntary maximal isocapnic ventilation (MIV) for 2 min. Minute ventilation and esophageal, gastric, and transdiaphragmatic pressures were measured breath by breath. We observed that ventilation, peak inspiratory and expiratory pressures, and inspiratory flow rate declined from the start of the run to reach a plateau at 60 s that was sustained for the remainder of the exercise. In a subsequent series of studies, MIV was performed for variable durations between 15 and 120 s. The normalized maximum relaxation rate of unoccluded inspiratory sniffs (sniff MRR, %pressure loss/10 ms) was determined immediately on stopping MIV. Sniff MRR slowed as the duration of MIV increased and paralleled the decline in inspiratory pressure and ventilation observed during the 2-min exercise. No further slowing in MRR occurred when ventilation became sustainable. We conclude that, during MIV, the progressive loss of ventilation and capacity to generate pressure is associated with the early onset and progression of a peripheral fatiguing process within the inspiratory muscles.

Adult↗

PubMed1988

Pulmonary function and dysfunction in multiple sclerosis.

Pulmonary function was studied in 25 patients with clinically definite multiple sclerosis with a range of motor impairment. Forced vital capacity (FVC), maximal voluntary ventilation (MVV), and maximal expiratory pressure (MEP) were normal in the ambulatory patients (mean greater than or equal to 80% predicted) but reduced in bedridden patients (mean, 38.5%, 31.6%, and 36.3% predicted; FCV, MVV, and MEP, respectively) and wheelchair-bound patients with upper extremity involvement (mean, 69.4%, 50.4%, and 62.6% predicted; FVC, MVV, and MEP, respectively). Forced vital capacity, MVV, and MEP correlated with Kurtzke Expanded Disability Status scores (tau = -0.72, -0.70, and -0.65) and expiratory muscle weakness occurred most frequently. These findings demonstrate that marked expiratory weakness develops in severely paraparetic patients with multiple sclerosis and the weakness increases as the upper extremities become increasingly involved.

Adult↗

PubMed1990

Exercise cardiorespiratory function in adolescents with pectus excavatum. Observations before and after operation.

We studied 12 children with pectus excavatum (mean age, 13.8 years) using pulmonary function and exercise testing. Eight patients had surgical repair and were studied before and after repair. Four patients did not have repair and were tested twice. The degree of chest wall deformity in the two groups was similar. All patients reached 86% or more of their maximal predicted heart rate with exercise. Total lung capacity decreased 8% (p less than 0.01) after operation. In the nonoperated control group, total lung capacity was similar during both studies. The ratio of ventilation at maximal exercise to maximal voluntary ventilation was 68% +/- 12% before and 66% +/- 9% after operation in the operated group and 69% +/- 18% and 79% +/- 30% at two studies in the nonoperated group (nonsignificant changes). Maximal oxygen uptake was 36.1 +/- 4.4 ml/kg/min preoperatively and 38.1 +/- 8.1 postoperatively and 41.2 +/- 7.3 ml/kg/min and 43.0 +/- 6.9 on two studies in the nonoperated group (nonsignificant changes). Cardiac output and stroke volume increased appropriately with exercise both before and after operation. Operation had no physiologically significant effect on the cardiorespiratory response to exercise. Slight changes in cardiorespiratory function occurred in both operated and nonoperated subjects. These results emphasize the importance of studying patients before and after operation and of using a control group.

Adolescent↗

PubMed1992

Improved diaphragmatic function after surgical plication for unilateral diaphragmatic paralysis.

We studied pulmonary function tests, maximal voluntary ventilation, arterial blood gases, and respiratory muscle strength and recruitment pattern in a 37-yr-old symptomatic man before and after surgical plication for a left unilateral diaphragmatic paralysis. After plication, FVC, FEV1, TLC and FRC increased, whereas residual volume remained unchanged. Arterial PO2 improved from 70 to 87 mm Hg. Diaphragmatic strength, as expressed by the maximal transdiaphragmatic pressure increased from 30 to 75 cm H2O, and maximal voluntary ventilation increased from 74 to 123 L/min. Ventilatory muscle recruitment also changed: there was a shift from a positive to a negative delta Pg/delta Ppl slope during tidal breathing. This indicates more effective diaphragmatic recruitment after the procedure. We conclude that surgical plication may be of benefit to patients with symptomatic unilateral diaphragmatic paralysis. The improvement is due to improved respiratory muscle function.

Adult↗

PubMed1990

[Circulatory and respiratory parameters in children at cardiovascular risk].

Physical performance, pulse rate, blood pressure and respiratory functions (vital capacity, forced expiratory volume and maximal voluntary ventilation) in rest and during physical loading were studied in children of parents having had myocardial infarction under the age of 45. Children with normal and increased skinfold width, and with low resp. normal HDL-cholesterol levels were selected. The most unfavourable respiratory, circulatory and performance results were obtained in obese children with low HDL-cholesterol; significant differences were found in resting heart rate and maximal voluntary ventilation (MVV). In the author's mind, the primary factor is high body fat content resulting in poor physical activity and unfavourable HDL-cholesterol levels. All this forecasts a bad prognosis for adulthood in respect of cardiovascular disease.

Cardiovascular Diseases↗

PubMed1975

Diagnosis of upper airway obstruction by pulmonary function testing.

We compared 11 patients with upper airway obstruction (obstruction at or proximal to the carina) to 22 patients with chronic obstructive pulmonary disease and to 15 normal subjects utilizing spirometry, lung volumes, airway resistance, maximal voluntary ventilation, single-breath diffusion capacity, and maximal inspiratory and expiratory flow-volume loops. Four values usually distinguished patients with upper airway obstruction: (1) forced inspiratory flow at 50 percent of the vital capacity (FIF50%) less than or equal to 100 L/min; (2) ratio of forced expiratory flow at 50 percent of the vital capacity of the FIR50% (FEF50%/FIF50%) larger than or equal to 1; (3) ratio of the forced expiratory volume in one second measured in milliliters to the peak expiratory flow rate in liters per minute (FEV1/PEFR) larger than or equal to 10 ml/L/min; and (4) ratio of the forced expired volume in one second to the forced expired volume in 0.5 second (FEV1/FEV0.5) larger than or equal to 1.5. The last ratio can be determined with a simple spirometer.

Adult↗

PubMed1976

Clinical value of rebreathing test in obstructive lung diseases.

The ventilatory response to CO2 inhalation, using rebreathing method, was studied in normal subjects and in patients with bronchial asthma and chronic obstructive lung disease. The patients with lung disease had flatter CO2 response curves. However, it the ventilation was expressed as a fraction of the maximal voluntary ventilation, the difference between normal subjects and patients disappeared. The reduced ventilatory response of these patients may be of mechanical origin and not depending on reduced CO2 sensitivity. The high lung volume of these patients may be the mean factor of the mechanical disadvantage of thoracomuscular system.

Adult↗

PubMed1989

Sustained maximal ventilation after endurance exercise in athletes.

Although impaired respiratory muscle performance that persists up to 5 min after exercise is stopped has been demonstrated during exhaustive exercise in normal young men, it is not known whether impaired respiratory muscle function follows endurance exercise to exhaustion in highly trained athletes. To study the effects of exercise on sustained maximal voluntary ventilation immediately after exercise, eight elite cross-country skiers performed a 4-min maximal sustained ventilation (MSV) test before and immediately after exhaustive exercise. Subjects were encouraged to maintain maximal ventilation (VE) throughout the MSV test. To encourage greater effort, rapid visual feedback of VE was provided on a computer terminal along with a target VE based on their 12-s maximum voluntary ventilation (MVV). The subjects (7 males, 1 female) were 18.5 +/- 0.9 yr old (mean +/- SD) and exercised for 62.5 +/- 16.7 min at 77 +/- 5% of their maximum oxygen consumption during which average VE was 106.7 +/- 24.2 l/min BTPS. The mean MVV was 196.0 +/- 29.9 l/min or 107% of their age- and height-predicted MVV. Before exercise the MSV was 86% of the MVV or 176.7 +/- 30.5 l/min, whereas after exercise the MSV was 90% of the MVV or 180.3 +/- 28.9 l/min (P = NS). The total volume of gas expired during the 4-min MSV was 706.7 +/- 121.9 liters before and 721.2 +/- 115.5 liters after exercise (P = NS). In this group of athletes, exhaustive exercise produced no deleterious effects on the ability to perform a 4-min MSV test immediately after exercise.

Adolescent↗

PubMed1991

Normal values and ranges for ventilation and breathing pattern at maximal exercise.

Assessment of the breathing pattern at maximal exercise in patients is limited because the range of ventilatory responses (minute ventilation; tidal volume; respiratory rate) at maximal exercise in normal humans is unknown. We studied 231 normal subjects (120 women; 111 men) equally distributed according to age from 20 to 80 years. Each subject performed a progressive incremental cycle ergometer exercise test to their symptom-limited maximum. Mean ventilation at the end of exercise (Vemax) was significantly higher in men (mean +/- SD, 97 +/- 25 L/min) than in women (69 +/- 22 L/min) (p less than 0.001). Minute ventilation at the end of exercise as a fraction of predicted maximal voluntary ventilation (Vemax/MVV) for all subjects was 0.61 +/- 0.14 (range, 0.28 to 1.02). There was no difference in Vemax/MVV between men (0.62 +/- 0.14) and women (0.59 +/- 0.14). Tidal volume at the end of exercise (Vtmax) was higher in men (2.70 +/- 0.48 L) than in women (1.92 +/- 0.41 L) (p less than 0.001). Any differences in Vtmax between men and women disappeared when Vtmax was corrected for baseline FVC. Respiratory rate at the end of exercise (RRmax) was 36.1 +/- 9.2 breaths per minute for all subjects. There was no difference in RRmax between men and women. The Vemax correlated best with carbon dioxide output at the end of exercise (r = 0.91; p less than 0.001) and with maximal oxygen uptake (r = 0.90; p less than 0.001) for all subjects. This study of a large group of subjects has demonstrated the wide range of possible breathing patterns which are adopted during exercise and has provided a wide range of "normal" responses which must be taken into consideration when maximal ventilatory data from exercise tests are analyzed.

Adult↗

PubMed1988

Hypothyroidism presenting with respiratory muscle weakness.

A 58-yr-old woman presented with recurrent chest infections, breathlessness, and orthopnea. She complained of nonspecific tiredness and aching limbs. A chest radiograph showed an elevated right hemidiaphragm. Thyroid function tests showed her to be severely hypothyroid (T4 = 23 nmol/L; TSH greater than 50 mU/L). Measurement of maximal respiratory mouth pressures (expiratory: 50 cm H2O, normal, 94 +/- 33; inspiratory: 15 cm H2O, normal, 71 +/- 27) suggested global respiratory muscle weakness. Severe bilateral diaphragm weakness was demonstrated by a greatly reduced maximal transdiaphragmatic pressure (Pdi) (Pdi Pimax = 0, normal, 65 +/- 31 cm H2O; sniff Pdi = 25 cm H2O, normal, 121 +/- 25). No Pdi was detectable on stimulation of the right phrenic nerve, whereas, on the left, it was 11 cm H2O (normal 7 to 15 cm H2O). Phrenic nerve conduction time was prolonged to both sides (right, 12 ms, left, 10 ms; normal, less than 9.5 ms). The relaxation rate of Pdi after a maximal sniff and after bilateral phrenic nerve stimulation was abnormally slow (7.4%/10 ms, 6.3%/10 ms, respectively). Three months after starting treatment with thyroxine she had become euthyroid, and phrenic nerve conduction times and Pdi relaxation rates had returned to normal. Maximal respiratory pressures, vital capacity, and maximal voluntary ventilation improved progressively on treatment, although maximal respiratory pressures still had not reached the normal range after six months. We conclude that hypothyroidism may present with breathlessness due to respiratory muscle weakness and/or phrenic nerve neuropathy and is reversible with treatment.

Diaphragm↗

PubMed1987

Shape of the dose-response curve to cold air inhalation in normal and asthmatic subjects.

Inhalation of cold air at increasing levels of minute ventilation with assessment of bronchomotor tone between each inhalation (dose-response curve) has been used as a method to assess bronchial hyperresponsiveness. However, no information is available on the shape of the obtained dose-response curve, and it is not known if a plateau of response is reached. We investigated this problem in 13 adult asthmatic subjects (PC20 methacholine results varying from 0.04 to 15.2 mg/ml), 5 normal and 2 former asthmatic individuals (PC20 greater than 8 mg/ml). Inhalation dose-response curves were drawn by asking the subjects to inhale dry cold air (-20 degrees C) for 3 min at progressively increasing degrees of ventilation (5, 10, 15, 20, etc., L/min) until maximal voluntary ventilation (MVV) or sufficient bronchoconstriction was reached. FEV1 was assessed after each degree until no further decline was seen. No functional recovery was observed before asking the subject to inhale the next dose of cold air. Maximal falls in FEV1 ranged from 20.7 to 56.5% in the current asthmatic subjects, whereas no significant (less than 10%) changes in FEV1 were obtained in the normal and former asthmatic individuals. Seven to 13 points on the individual dose-response curves were obtained for each current asthmatic subject. Curves were analyzed using the common pharmacologic logistic model. The coefficients of correlation were, in general, highly statistically significant. Curves obtained for the current asthmatic subjects represented a truncated sigmoidal pattern without a plateau. Curves were flat in the normal and former asthmatic individuals.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1988

Changes in respiratory muscle function after neostigmine injection in patients with myasthenia gravis.

In sixteen patients with myasthenia gravis, the weakness of respiratory muscles, especially of expiratory, caused some disturbances in lung function. Thirty minutes after injection of neostigmine, general improvement of muscle function was accompanied by an increase of strength and endurance of respiratory muscles. The mean value of maximal inspiratory mouth pressure (PImax) increased by 33%, maximal expiratory mouth pressure (PEmax) by 23.5% and maximal voluntary ventilation (MVV) by 21%. As a consequence of these changes amelioration of lung function indices was found, vital capacity increasing on average by 13% and residual volume decreasing by 12.5%. We concluded that patients with generalized myasthenia gravis have disturbances in lung function which may be partially improved by neostigmine injection or other anticholinesterase agents.

Adult↗

PubMed1992

Respiratory function in multiple sclerosis. Utility of clinical assessment of respiratory muscle function.

PURPOSE: The aim of this study was to assess the utility of clinical assessment of respiratory muscle weakness in MS. PATIENTS AND METHODS: We studied 40 MS patients who performed pulmonary function tests using standard procedures and measures of respiratory muscle strength. Descriptive clinical indices included a history of detailed neurologic findings, including upper and lower extremity weakness, cerebellar signs, and evidence of cerebral lesions and other clinical signs including dependence in activities of daily living, shortness of breath, weak voice, dysarthria and dysphagia. We devised an index comprised of four clinical signs: the patient's report of difficulty in clearing pulmonary secretions and his report of a weakened cough, the examiner's observation of the patient's cough, and ability to count on a single exhalation. RESULTS: Mean values of TLC (95 percent +/- 14) VC (91 percent +/- 19), and RV (106 percent +/- 34) were normal. By contrast, MVV (68 percent +/- 20), PImax (74 percent +/- 27) and PEmax (51 percent +/- 22) were decreased. Stepwise multiple regression indicated that the best single predictor of expiratory muscle weakness was the index score; the combination of index score, upper extremity weakness, and maximal voluntary ventilation accounted for 60 percent of the variance in PEmax. CONCLUSION: We conclude that clinical assessment is a better predictor of respiratory muscle weakness than spirometry and that a systematic clinical assessment supplemented by respiratory muscle assessment and MVV can uncover subtle respiratory muscle weakness in patients with MS.

Adult↗

PubMed1988

Ventilatory muscle training in the elderly.

To test the hypothesis that declining ventilatory function in the elderly impairs exercise capacity, we tested maximal exercise capacity and ventilatory function before and after a program of ventilatory muscle training in 25 elderly subjects (ages 65-75 yr). Ventilatory muscle training was performed by means of isocapnic hyperpnea for 30 min/day, 4 days/wk for 8 wk. Before and after the training, we measured maximal exercise capacity by means of an incremental exercise test (IET) and ventilatory muscle endurance by means of the maximum sustained ventilatory capacity (MSVC). Ratings of perceived exercise (RPE) for breathlessness and leg effort were evaluated each minute by means of a modified Borg scale during both the IET and a 12-min single-stage exercise test (SST) performed at approximately 70% of the maximal exercise capacity. The trained group showed a significant increase in the MSVC, from 71.9 +/- 26.4 to 86.9 +/- 20.9 l/min (P less than 0.01), whereas the control group showed no change (66.3 +/- 22.5 to 65.1 +/- 22.1 l/min). In addition, the maximal voluntary ventilation increased in the trained group, from 115 +/- 41 to 135 +/- 36 l/min (P less than 0.01). Neither the trained nor the control group showed an increase in maximum O2 uptake, maximum CO2 consumption, or maximum minute ventilation during the IET. Evaluation of the RPE during both the IET and SST showed that although there was a small decrease in RPE for breathing and leg discomfort, changes between the control and treated groups were similar.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗