Vital capacity as an efficacy measure: con.
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Amyotrophic Lateral Sclerosis↗
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Vital capacity as an efficacy measure: Summary.
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Amyotrophic Lateral Sclerosis↗
Influence of muscle length on human inspiratory and limb muscle endurance.
The influence of muscle length on endurance of the inspiratory muscles and the flexors of the elbow was assessed in 12 healthy subjects who performed series of 18 maximal static voluntary contractions of 10 sec duration separated by rest intervals of 5 sec. Inspiratory contractions were performed at functional residual capacity (FRC) and at FRC plus half inspiratory capacity (FRC + 1/2 IC). Contractions of the flexors of the elbow were performed at 90 degrees and 45 degrees of flexion. Compared with values obtained at the control muscle length, maximal force at the short length was reduced to 78 +/- 10% for the inspiratory muscles and 74 +/- 6% for the flexors of the elbow (n.s.). For each test, indices of endurance were measured as the average (and peak) force attained in the better of the last two contractions expressed as a percentage of that in the best of the first three. For the flexors of the elbow endurance was significantly enhanced at the short length (45 degrees: 61 +/- 3.0%, mean +/- SE) compared with the control length (90 degrees: 55 +/- 2.0%, P less than 0.01). By contrast, this enhancement of endurance did not occur for the inspiratory muscles at the short length (FRC + 1/2 IC: 81 +/- 3.0%; FRC: 87 +/- 3.0%; P less than 0.02). Endurance of the inspiratory muscles was greater than that of the elbow flexors at both muscle lengths. The enhanced endurance of the elbow flexors, when tested at a short muscle length, is consistent with data obtained in isolated muscles.
Adult↗
Exercise-induced changes in diaphragmatic bioenergetic and antioxidant capacity.
The primary inspiratory muscle in mammals is the diaphragm. Endurance exercise elevates both the oxidative and antioxidant capacity of the costal and crural diaphragm. These exercise-induced changes in oxidative and antioxidant capacity occur rapidly after the onset of training and are associated with reduced oxidative injury and improved diaphragmatic endurance.
Animals↗
[Long term domiciliary mechanical ventilation in patients with neuromuscular disease (indications, establishment and follow up)].
UNLABELLED: Neuromuscular diseases represent a heterogeneous group of pathologies which common feature is the development of a restrictive ventilatory failure. BACKGROUND: Respiratory insufficiency of neuromuscular origin manifests itself by functional symptoms that must be carefully searched for in the history, such as headaches, sleep disorders, or dyspnoea of effort, sometimes very mild, or in severe cases associated with orthopnoea. Follow up should be multi-disciplinary. On the respiratory level regular measurement of blood gases, vital capacity, maximum inspiratory and expiratory pressures as well as sleep studies, will detect the criteria for mechanical ventilation (hypercarbia > 45 mm Hg, nocturnal desaturation < 88%, vital capacity < 60%, PImax < 60 cm H2O). STATE OF THE ART: The establishment of mechanical ventilation is a major decision for patients with neuromuscular disease because of the important physical, psychological, social and sometimes financial consequences. The patients and their family must be instructed precisely in order to obtain the best possible observation and compliance. The establishment requires a stay in hospital of several days to optimise the choice of ventilator, its settings, and connections. The link with the organisation managing the domiciliary ventilation is fundamental in ensuring follow up after discharge from hospital. Techniques of cough assistance must be taught to each neuromuscular patient requiring mechanical ventilation. CONCLUSION: Ventilation of neuromuscular patients requires careful evaluation of the indications and rigorous follow up by a multidisciplinary team with wide experience of this type of disease.
Cough↗
Continuous measurement of respiratory resistance in asthmatic children.
In 13 children (7-13 years old) with bronchial asthma in remission, respiratory system resistance was continuously measured by the forced oscillation method at 10 Hz, using on-line digital computer analysis. Corrections were made for mouth impedance which was determined from a prior Valsalva maneuver. Functional residual capacity was also periodically determined by the body plethysmographic technique in order to allow calculation of specific respiratory system conductance (SGRS). The total observation period of 45 min consisted of quiet breathing interrupted by vital capacity maneuvers. In a single-blind design, eight children were given 0.15 mg isoproterenol sulfate from a proprietary spray delivered in the beginning of an inspiratory vital capacity maneuver while five received a placebo (freon propellent alone). A significant increase in SGrs (+53%) was observed 75 sec after isoproterenol sulfate administration. SGrs peaked after 2 min (+ 61%) and remained elevated significantly for 10 min. No significant changes occurred in the placebo group. The immediate decrease in SGrs which was observed following control vital capacity maneuvers, was prevented by isoproterenol sulfate but not by the freon propellent. Our findings suggest that although peak bronchodilation does not occur before 2 min following isoproterenol sulfate inhalation, an effect, namely prevention of bronchoconstriction induced by a deep breath, is already detectable within seconds.
Adolescent↗
Respiratory mechanics in supine subjects during progressive partial curarization.
Respiratory mechanics were studied in six supine conscious volunteers during progressive muscle weakness produced by infusion of d-tubocurarine. Partial curarization was carried out to the point of abolishing head lift ability and handgrip strength. At all levels of partial paralysis, expiratory muscle strength was significantly more impaired than inspiratory strength. Despite this, subjects maintained relatively normal maximal expiratory flow rates, whereas inspiratory flows decreased significantly. The diminished inspiratory flows are not fully explained by decreased driving pressures during force inspiration, since inspiratory resistance increased significantly with the decreased flow. Inspiratory flow patterns suggest a variable extrathoracic obstruction most likely due to the absence of normal airway abductor activity during inspiration. Maximal respiratory muscle weakness decreased forced vital capacity by 29% and total lung capacity by 15%. The decreased level of lung inflation did not alter lung elastic recoil. Functional residual capacity was unchanged, but inspiratory capacity decreased by 25% and residual volume increased by 38%. These changes are in accord with predictions based on the decreased muscle strength and normal respiratory system recoil.
Adult↗
How do patients with either asthma or COPD perceive acute bronchodilation?
The purpose of this study was to assess the perception of bronchodilation, as a change in shortness of breath on a bipolar visual analogue scale (VAS), in 16 asthmatics and 20 subjects with COPD. Bronchodilation was gradually induced by five consecutive terbutaline inhalations (cumulated dose 800 micrograms). The subjects were categorized into high and low perceivers, on the basis of a cut-off of 25% VAS line length (after the fifth inhalation). The quality of perception was studied on a within-subject basis by linear regression analysis of VAS ratings against changes in lung function, and was characterized in terms of strength of correlation (squared correlation coefficient, r2), slope, and VAS axis intercept. Fourteen out of 16 asthmatics, and 13 out of 20 COPD subjects, were high perceivers. In the COPD group, the high perceivers had a larger objective response--particularly in inspiratory vital capacity--than the low perceivers. The strongest correlation between subjective and objective response was obtained in asthmatics when the improvement in shortness of breath was evaluated against the decrease in specific inspiratory resistance (median r2 = 0.831). In COPD low perceivers, subjective and objective response were unrelated, while COPD high perceivers differed from the asthmatics by larger intercepts. The perceptual characteristics were unrelated to the degree of baseline obstruction, whilst a modest relationship (r = 0.51) was found between the increase in forced expiratory volume in one second (FEV1) and r2 of the VAS/delta FEV1 analysis.(ABSTRACT TRUNCATED AT 250 WORDS)
Asthma↗
Inefficient ventilation and reduced respiratory muscle capacity in congestive heart failure.
The extent and time-course of changes in lung volumes, ventilatory efficiency at rest and during exercise, and respiratory muscle function and their influence on exercise limitation in congestive heart failure (CHF) are unclear. It is unknown whether respiratory muscle function may predict changes in exercise limitation or may be impaired in patients with poor outcome. 145 male patients (54 +/- 1 years) suffering from CHF (NYHA class I-III, mean 2.3 +/- 0.1), with a LVEF of 23 +/- 1%, and a mean peak O2 uptake (VO2peak) 15.0 +/- 0.5 mL X min(-1) X kg(-1), were studied. They were grouped in Weber functional classes A to D according to their VO2peak. Significant increases in ventilatory equivalents for O2 and CO2 (VE/VCO2peak) and in dead space ventilation at rest and during exercise were found with increasing exercise limitation. Moreover, there was a correlation of static and dynamic lung volumes (inspiratory vital capacity, IVC, r = 0.43, P < 0.01), as well as of maximal inspiratory pressure (MIP; r = 0.46, P < 0.01) with VO2peak. Patients who died (n = 26) or were heart transplanted (n = 20) during a follow-up (mean 800 +/- 10 days) had a reduced MIP (6.4 +/- 0.4 kPa) as compared with survivors (n = 82; 9.3 +/- 0.7 kPa, P < 0.01). In a subgroup of 33 patients re-evaluated after six months, individual changes in IVC and VE/CO2peak, but not in MIP, correlated to changes in VO2peak (r = 0.69 and r = 0.72 respectively; P < 0.01). In CHF, exercise limitation is associated with reversible lung restriction and inefficient ventilation at rest and during exercise. Patients with severe CHF have a significant reduction in MIP, a finding that is associated with poor outcome.
Adult↗
[Pulmonary ventilation in normal children. II. Mechanics orf respiration: timed vital capacity and maximal expiratory and inspiratory flows].
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Adolescent↗
Effects of lung volume and airflow on the frequency spectrum of vesicular lung sounds.
UNLABELLED: The purpose of this study was to determine whether the vesicular lung sound frequency spectrum is affected by changes in lung volume and airflow. Nine healthy young nonsmokers were studied. The dependent variables were the points that divide the power spectrum of the vesicular lung sound into quarters (1st, 2nd and 3rd quartiles (Q1, Q2 and Q3]. Recording sites were the right upper anterior (RUL) and lower posterior (RLL) chest wall. Lung sounds were high-pass filtered at 100 Hz. To evaluate the effect of volume, lung sounds were recorded during an inspiratory vital capacity (VC) maneuver at near constant airflow rates. The spectral parameters were determined at each sixth of the VC. To assess the effects of airflow, 5 of the subjects breathed from resting lung volume at peak inspiratory airflows of between 1 and 3.0 L/sec for a total of 16 breaths each and the frequency parameters of the lung sounds occurring during peak inspiratory airflows were determined. RESULTS: Volume effects: only at the RUL was there a small but significant decrease in all three parameters with increasing lung volume. Airflow effects: all parameters were independent of airflow except for a weakly positive relationship (r = 0.285, P less than 0.05) for Q3 at the RUL location. Individually, there were weakly significant trends in three of the five subjects. These data suggest that the frequency composition of the vesicular lung sound in groups of healthy adults is not systematically affected by changes in lung volume or airflow.
Adult↗
Flow-volume relationships during spontaneous breathing through endotracheal tubes.
OBJECTIVE: Breathing spontaneously through an endotracheal tube is often equated with "breathing through a straw." The objective of this study was to examine whether endotracheal tubes functionally act as tubular resistors in patients during tidal breathing, machine-initiated breaths, and vital capacity maneuvers. DESIGN: Descriptive study. SETTING: University hospital surgical ICU. PATIENTS: Eighteen mechanically ventilated, critically ill, postoperative patients (34 to 87 yrs). MEASUREMENTS: Flow-volume loops were recorded during tidal and machine breaths, as well as during vital capacity maneuvers. The loops were inspected visually for evidence of air flow limitation. Expiratory characteristics were examined using the ratio of expiratory volume in 1 sec to the expiratory volume in 0.5 sec and the ratio of expiratory volume in 1 sec to peak expiratory flow rate. The ratio of expiratory volume in 1 sec to that in 0.5 sec (greater than 1.5) and the ratio of expiratory volume in 1 sec to peak expiratory flow rate (greater than 10 mL/L/min) are seen with upper airway obstruction. MAIN RESULTS: Mean spontaneous tidal volume was 361 +/- 92 (SD) mL and vital capacity was 1104 +/- 16 mL, while the ratio of expiratory volume in 1 sec to that in 0.5 sec was 1.57 +/- 0.17 and 1.7 +/- 0.1 (p less than .05), respectively. The ratio of expiratory volume in 1 sec to peak expiratory flow rate was 9.9 +/- 1.7 during tidal breathing and 12.9 +/- 1.2 (p less than .05) during vital capacity maneuvers. CONCLUSIONS: Endotracheal tubes of the diameters used in these adult postoperative patients (7 and 8 mm) cause only minimal limitation to air flow during the small volumes and low-flow rates observed during tidal breathing. Evidence of greater air flow limitation was seen during vital capacity maneuvers.
Adult↗
Influence of lung volume on oxygen cost of resistive breathing.
We examined the relationship between the O2 cost of breathing (VO2 resp) and lung volume at constant load, ventilation, work rate, and pressure-time product in five trained normal subjects breathing through an inspiratory resistance at functional residual capacity (FRC) and when lung volume (VL) was increased to 37 +/- 2% (mean +/- SE) of inspiratory capacity (high VL). High VL was maintained using continuous positive airway pressure of 9 +/- 2 cmH2O and with the subjects coached to relax during expiration to minimize respiratory muscle activity. Six paired runs were performed in each subject at constant tidal volume (0.62 +/- 0.2 liters), frequency (23 +/- 1 breaths/min), inspiratory flow rate (0.45 +/- 0.1 l/s), and inspiratory muscle pressure (45 +/- 2% of maximum static pressure at FRC). VO2 resp increased from 109 +/- 15 ml/min at FRC by 41 +/- 11% at high VL (P less than 0.05). Thus the efficiency of breathing at high VL (3.9 +/- 0.2%) was less than that at FRC (5.2 +/- 0.3%, P less than 0.01). The decrease in inspiratory muscle efficiency at high VL may be due to changes in mechanical coupling, in the pattern of recruitment of the respiratory muscles, or in the intrinsic properties of the inspiratory muscles at shorter length. When the work of breathing at high VL was normalized for the decrease in maximum inspiratory muscle pressure with VL, efficiency at high VL (5.2 +/- 0.3%) did not differ from that at FRC (P less than 0.7), suggesting that the fall in efficiency may have been related to the fall in inspiratory muscle strength. During acute hyperinflation the decreased efficiency contributes to the increased O2 cost of breathing and may contribute to the diminished inspiratory muscle endurance.
Adult↗
Respiratory muscle testing: a valuable tool for children with neuromuscular disorders.
RATIONALE: Data on respiratory muscle performance in children with neuromuscular disorders are limited. OBJECTIVES: The aim of this study was to assess respiratory muscle strength by volitional and nonvolitional tests and to compare these tests with forced vital capacity. METHODS: Inspiratory muscle strength was assessed by measuring transdiaphragmatic and esophageal pressures generated during volitional and nonvolitional maneuvers, whereas expiratory muscle strength was assessed by measuring the gastric pressure generated during a cough maneuver. Lung volumes were assessed by measuring forced vital capacity. MEASUREMENTS AND MAIN RESULTS: Forty-one patients with Duchenne muscular dystrophy (n = 20), spinal amyotrophy (n = 8), and congenital myopathy (n = 13) were included, aged 2 to 18 yr. All the patients were able to perform the sniff and the cough maneuver. Sniff transdiaphragmatic pressure decreased with age in Duchenne patients, whereas it increased with age in patients with spinal amyotrophy and congenital myopathy. Magnetic stimulation of the phrenic nerves was obtained in all patients. Twenty-five (61%) patients were able to perform forced vital capacity. In the three groups of patients, a positive correlation was observed between volitional, assessed by the sniff maneuver, and nonvolitional respiratory muscle tests, assessed by the magnetic stimulation of the phrenic nerves. Also, forced vital capacity correlated with sniff transdiaphragmatic pressure and cough gastric pressure. CONCLUSIONS: Volitional respiratory muscle tests correlated with nonvolitional tests and with forced vital capacity. Simple volitional respiratory muscle tests constitute a valuable tool for the assessment of respiratory muscle strength in young patients with neuromuscular disorders.
Adolescent↗
Single-breath washouts in a rotating stretcher.
Vital capacity single-breath washouts using 90% O2-5% He-5% SF6 as a test gas mixture were performed with subjects sitting on a stool (upright) or recumbent on a stretcher (prone, supine, lateral left, lateral right, with or without rotation at end of inhalation). On the basis of the combinations of supine and prone maneuvers, gravity-dependent contributions to N2 phase III slope and N2 phase IV height in the supine posture were estimated at 18% and 68%, respectively. Whereas both He and SF6 slope decreased from supine to prone, the SF6-He slope difference actually increased (P = 0.015). N2 phase III slopes, phase IV heights, and cardiogenic oscillations were smallest in the prone posture, and we observed similarities between the modifications of He and SF6 slopes from upright to prone and from upright to short-term microgravity. These results suggest that phase III slope is partially due to emptying patterns of small units with different ventilation-to-volume ratios, corresponding to acini or groups of acini. Of all body postures under study, the prone position most reduces the inhomogeneities of ventilation during a vital capacity maneuver at both inter- and intraregional levels.
Adult↗
Influence of unequal ventilation on the single breath K(CO) in COPD revealed by comparison with the rebreathing K(CO).
In 16 patients with chronic obstructive pulmonary disease (COPD) we investigated the relation between unequal ventilation and diffusion by means of lung volumes and Krogh factors (K(CO)) using the single breath (SB) and the rebreathing (RB) methods. We used both methods because the SB measurement is sensitive to unequal ventilation and diffusion whereas the RB measurement is not. Because K(CO) depends on inspired volume (VI), the SB and RB measurement have to be performed at the same VI. We therefore determined K(CO)SBm by making a SB measurement at VI equal to the mean inspired volume during the RB measurement and then calculated K(CO)RBm by dividing the RB transfer factor for CO by the mean RB lung volume. In 10 patients K(CO)SBm/K(CO)RBm, a parameter determined by the combined effect of unequal ventilation and diffusion, was almost equal to unequal ventilation, the quotient of the SB and mean RB lung volumes (VSBm/VRBm), just as in normal subjects (Jansons et al., Respiration 67 (2000) 383). This finding means that we can correct for the effects of unequal ventilation by dividing K(CO)SBm by VSBm/VRBm. We suggest that the SB measurement of K(CO) at vital capacity can be corrected in a similar way.
Adult↗
Neuromuscular disease causing acute respiratory failure.
In the developed world, Guillain-Barré syndrome and myasthenia gravis account for the majority of cases of acute respiratory failure associated with neuromuscular disease. The 4 components that contribute to respiratory failure are upper-airway dysfunction, inspiratory-muscle weakness, expiratory-muscle weakness, and the pulmonary complications associated with these conditions. Careful observation and objective monitoring are essential to determine the appropriate timing of intubation and mechanical ventilation. Pulmonary function tests that can help predict the need for mechanical ventilation include vital capacity, peak inspiratory pressure, and peak expiratory pressure. The morbidity and mortality of patients who require mechanical ventilation are not insubstantial. This paper will review the mechanisms underlying acute respiratory failure, the clinical assessment of patients, the predictors of the need for mechanical ventilation, and the intensive-care-unit morbidity and mortality of patients with Guillain-Barré syndrome or myasthenia gravis.
Critical Care↗
Effects of industrial respirators on breathing pattern at different work levels.
The effects of a filtering device and an air-line apparatus on breathing pattern were studied in healthy men with different physical characteristics and work capacity. The subjects comprised nine construction workers aged 35-44, and nine firemen aged 21-35. The construction workers' mean maximal oxygen consumption (VO2max) was 34.5 ml min-1 kg-1, the firemen's 66.9 ml min-1 kg-1. Breathing pattern was analyzed for its components, inspiratory time, expiratory time, breathing frequency, tidal volume, and pulmonary ventilation at rest, during two submaximal treadmill walks when the subjects' absolute work load was equal, and during recovery. Neither the filtering device nor the air-line apparatus had a significant effect on breathing pattern when compared with the control values measured twice with a low-resistance breathing valve. A significantly longer expiratory time, lower breathing frequency, and smaller pulmonary ventilation were found for the firemen with the breathing valve and the industrial respirators. The breathing pattern of the construction workers and the firemen differed, but the alterations were not induced by the use of the filtering device or the air-line apparatus when studied at aerobic work levels up to 60% VO2max.
Adult↗