PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Work of Breathing”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 recordsLinked to original sources
PubMedDate not supplied

The measurement of nonelastic work of breathing using a commercially available respiratory integrator.

The authors compared real-time, breath-by-breath work of breathing (WOB) measurements made with a Hewlett-Packard 8815A respiratory integrator with nonelastic WOB values obtained by planimetry of pressure-volume tracings. They measured WOB while normal subjects breathed through a low-resistane mouthpiece. The integrator-derived values for WOB correlated well with planimeter-derived values (r = 0.97). Valid measurements of nonelastic WOB can be made at the bedside in realtime using the Hewlett-Packard 8815A without the addition of custom-built circuitry or hardware.

Humans↗
PubMed1990

[The effect of pressure support ventilation on breathing patterns and the work of breathing].

We assessed breathing patterns during pressure support ventilation (PSV) and its relationship with the work of breathing in 10 postoperative patients. With increasing levels of pressure support, minute ventilation and tidal volume increased with a decrease in respiratory frequency. Increased minute ventilation was achieved by increased mean inspiratory flow. Duty cycle, however, decreased with PSV. This decrease might allow the diaphragm a longer rest period between contractions, which might decrease the risk of diaphragmatic fatigue. Furthermore, PSV reduced the inspiratory work added by a ventilator to near zero. Oxygen consumption was also decreased with PSV. We conclude that PSV improved the breathing patterns and minimized the work of breathing spontaneously via a ventilator.

Adult↗
PubMed1988

Effects of expiratory flow resistance on inspiratory work of breathing.

To minimize work of breathing, airway pressure should not fluctuate during spontaneous breathing with continuous positive airway pressure (CPAP). However, flow resistance in the inspiratory limb of the breathing circuit and an inadequate continuous gas flow rate result in airway pressure fluctuation and increased work of breathing. Flow resistance of the expiratory pressure/exhalation valve also directly affects the level of airway pressure during spontaneous inhalation with CPAP (the greater the resistance of the valve, the greater the decrease in airway pressure and work of breathing). We compared this effect with three types of expiratory pressure valves: a threshold resistor with low resistance to flow, an inflatable balloon (mushroom) valve with moderate resistance to flow, and a variable-orifice flow resistor with a high resistance to flow. Work increased up to threefold with the balloon valve and more than tenfold with the flow resistor compared with the threshold resistor. To apply CPAP, expiratory pressure valves with low resistance to flow should be used to minimize fluctuations in airway pressure and, thus, in the work of spontaneous breathing.

Humans↗
PubMed1976

[Normal value of ventilatory work of breathing (author's transl)].

Ventilatory work of breathing is defined as a variable referring to the mechanics of the breathing function of the lung, ascertainable from the alveolar pressure-breathing volume diagram. Information on the resistance of the respiratory canal can be obtained. The ventilatory respiration of 93 healthy persons at spontaneous resting breath frequency (15 +/- 3 min) was investigated, with the aid of a body plethysmograph. A mean value of 2.21 g-cm/ml (s = 0.92) was obtained. A dependence on age and sex could not be statistically proved. The value of 4.0 g-cm/ml (= 2s) is discussed as a limit to a pathological increase. With a rise in breath volume, relative weight and also, marginally, the spontaneous resting breath frequency, a significant increase of ventilatory work of breathing in normal persons must be anticipated. A so-called index of ventilatory work of breathing (breath volume/alveolar pressure changes under defined conditions) correlates significantly with ventilatory work of breathing and can thus be regarded as an orientating value for the resistance of the respiratory canal. Its mean value amounts to 3.10 cm/cm, with a SD of 1.12.

Adolescent↗
PubMed1989

Patient-ventilator partitioning of the work of breathing during weaning.

The work of breathing and its division between the patient and the mechanical ventilator were studied during weaning of 5 post-operative surgical patients from Synchronized Intermittent Mandatory Ventilation. Work by the patient (WP) was estimated by integrating the product of flow and pressure over time during intervals when waveforms indicated patient effort; ventilator work (WV) was similarly estimated during positive pressure inspirations. The ratio of WP to the rate of work on the lungs (WL) increased progressively during weaning from 0.14 +/- 0.04 to 1.2 +/- 0.15 while WV/WL dropped from 1.31 +/- 0.08 to 0.13 +/- 0.11. Work on the lungs decreased during weaning. This was due in part to significant improvements in lung mechanics: resistance decreased from 9.9 +/- 0.9 to 6.1 +/- 1.6 cmH2O/1/s and compliance increased from 58 +/- 17 to 102 +/- 30 ml/cmH2O. The patient and ventilator work ratios, and the work of breathing quantify factors which may be directly useful to the clinician and to future systems to automate weaning.

Airway Resistance↗
PubMed1987

Airway caliber and the work of breathing in humans.

Mechanical work rate of breathing was measured in five normal subjects during voluntary eucapnic hyperventilation at rates of approximately 10, 20, 40, 60, and 80 l/min before and after inhalation of 1 mg of ipratropium bromide, an anticholinergic agent. Chest wall recoil pressure was measured over a range of lung volumes in each subject and was used as the reference pressure in the calculation of work rate. There was little change in elastic or resistive work rate at rest when vagal tone was reduced by ipratropium. The mean work at 40, 60, and 80 l/min was 8.9, 17.2, and 34.0 cmH2O.l-1.s before and 5.6, 12.4 and 25.8 cmH2O.l-1.s after ipratropium. This suggests that vagal tone significantly influences the work of breathing at high ventilatory rates, such as occur during strenuous exercise.

Adult↗
PubMed1989

Additional work of breathing imposed by endotracheal tubes, breathing circuits, and intensive care ventilators.

A disadvantage of spontaneous breathing through an endotracheal tube (ETT) and connector attached to a breathing circuit and/or ventilator (breathing device) is an increase in the work of breathing. The work of breathing associated with ETT of 6 to 9-mm diameter and eight breathing devices was determined, using a lung simulator to mimic spontaneous inspiration at flow rates of 20 to 100 L/min and a tidal volume of 500 ml, at both zero end-expiratory pressure (ZEEP) and 10 cm H2O continuous positive airway pressure (CPAP). Work associated with the breathing devices alone (WCIR) ranged from -0.002 kg.m/L (Servo 900-C ventilator, 7-mm ETT, 20 L/min, ZEEP) to 0.1 kg.m/L (continuous flow circuit, 7-mm ETT, 100 L/min, CPAP), the latter representing 196% of the work of normal breathing. When the devices were attached to ETT, total apparatus work (WAPP) ranged from 0.009 kg.m/L (Mapleson-D circuit, 9-mm ETT, 20 L/min, ZEEP) to 0.25 kg.m/L (Drager EV-A, 6-mm ETT, 100 L/min, ZEEP), the latter representing 490% of the work of normal breathing. This additional work imposed by the ETT varied considerably among devices. Spontaneous breathing through modern ventilators, circuits and ETT imposes a burden of increased work, most of which is associated with the presence of the ETT and connector. Whether this burden represents an impediment to the weaning patient, or has training value for the ultimate resumption of unassisted spontaneous ventilation, remains to be determined.

Female↗
PubMed1986

The importance of the balloon reservoir volume of a CPAP system in reducing the work of breathing.

We have previously reported, that the work of breathing in spontaneously breathing patients on CPAP could be significantly reduced by increasing the volume of the balloon reservoir in the circuit of a CPAP system from 3 to 23 l. We now report a study designed to determine the optimum balloon reservoir volume for the minimization of the work of breathing. Twenty intubated, spontaneously breathing patients were connected to a CPAP system with interchangeable balloon reservoirs. In each patient the work of breathing was measured for reservoir volumes of 3, 6, 12, 18, and 24 l attached in random order, while the positive airway pressure was held constant at 10 cm H2O. The balloons were constructed of the same material and had similar compliance. Rebreathing was prevented with use of one-way valves. Significant (p less than 0.001) decreases in the work of breathing were found on increasing reservoir volumes from 3 to 6, 6 to 12, and 12 to 18 l. A less significant (p less than 0.01) decrease in the work of breathing was found between reservoirs of 18 and 24 l. Rebreathing did not occur with significantly (p less than 0.001) lower flow rates when large reservoirs were used. We conclude that a balloon reservoir of 18 l represents the best compromise between reduction in the work of breathing, utilization of low source flow, and convenience of clinical use.

Carbon Dioxide↗
PubMed1976

Mechanical work of breathing derived from rib cage and abdominal V-P partitioning.

Estimates of the mechanical work of breathing derived from measurements of separate rib cage and abdominal volume displacements, each plotted against transthoracic pressure, include the elastic cost of chest wall distortion which may occur during breathing. Inspiratory work is partitioned between the diaphragm and the rib cage musculature by adding measurements of transabdominal pressure. The mechanical work of breathing derived from separate rib cage and abdominal volume-pressure (V-P) tracings (the sum of work done by the diaphragm, rib cage, and abdominal musculature) is compared with ventilatory work estimated from the Campbell diagram (which does not include any distortional work). During resting breathing the two estimates are closely comparable, consistent with little or no distortion of the chest wall during quiet breathing. As ventilation increases, the estimate developed from rib cage and abdominal tracings reveals systematically greater mechanical work than is estimated from the Campbell diagram, consistent with distortion of the chest wall from the relaxed thoracoabdominal configuration at higher levels of ventilation. At ventilations achieved during exercise, the Campbell diagram may underestimate the work of breathing by up to 25%.

Abdomen↗
PubMed1991

Effects of albuterol inhalation on the work of breathing during weaning from mechanical ventilation.

The work of breathing is a major determinant of the success of weaning from mechanical ventilation. The aim of this study was to assess whether an inhaled bronchodilator could reduce the mechanical load on the respiratory muscles and diminish the work. For this purpose, 15 intubated patients in the process of weaning from mechanical ventilation inhaled the beta 2-agonist bronchodilator albuterol via a spacer device filled with 1 mg of the drug and connected to the endotracheal tube. During spontaneous breathing, the mean work of breathing diminished significantly after albuterol, from 9.35 +/- 1.05 to 8.33 +/- 1.13 J/min (p less than 0.01), and seven patients exhibited a decrease superior or equal to 15%. This decrease resulted from a marked reduction in lung and airway resistance, from 12.0 +/- 1.7 to 9.8 +/- 1.4 cm H2O.L-1.s (p less than 0.05). No significant changes were observed in the breathing pattern, intrinsic PEEP or arterial blood gas measurements after albuterol, and peripheral cardiovascular effects were not significant. In seven patients, we were able to compare the changes that occurred after albuterol in the work of breathing during weaning from mechanical ventilation with the changes in pulmonary function induced by albuterol after extubation, as assessed by the forced oscillation method. A close correlation was found between the two types of change, further indicating that the reduction in the work of breathing was more likely to occur in patients with the largest bronchodilating effect of albuterol at baseline.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Inhalation↗
PubMed1986

Excessive work of breathing during intermittent mandatory ventilation.

Difficulties were experienced in weaning a patient from a ventilator by means of intermittent mandatory ventilation (IMV). The difficulty was overcome by installing an alternative IMV system (Hudson "disposable IMV valve") through which the patient drew her spontaneous breaths. Laboratory measurements showed that the resistance of the ventilator breathing system was much higher than that of the alternative system, mainly as a result of the resistance of the humidifier. It was calculated from measurements with a preset pattern of simulated breathing that the extra, external, work of breathing through the ventilator breathing system was approximately 1.5 times the normal internal mechanical work of breathing for a normal patient; with the alternative system, the extra work was only 0.5 times the normal. It is stressed that the breathing systems of IMV ventilators should be judged with the same rigour as other systems through which the patient is required to breathe spontaneously. It is recommended that manufacturers should provide the necessary information.

Aged↗
PubMedDate not supplied

The measurement of the work of breathing for the clinical assessment of ventilator dependence.

The work of breathing was measured in 10 normal subjects and in 28 critically ill patients with acute complications of obstructive pulmonary disease treated with assisted ventilation. The measurement of the work of breathing was found to be a useful objective variable for determining the capability for independent ventilation. Dependence on mechanical ventilation was observed when the respiratory work was greater than or equal to 1.7 kg-m/min. Patients were ordinarily capable of spontaneous ventilation when the respiratory work was less than or equal to 1.0 kg-m/min. Discontinuation of assisted ventilation was likely to be successful in those patients whose respiratory work was less than or equal to 1.5 kg-m/min if the patient was able to increase and maintain his work capability by a factor of two when breathing against an inspiratory resistance of 5 cm H2O for 10 min. Failure to increase the respiratory work when breathing against an inspiratory resistance indicated limitations in respiratory mechanics and was associated with the need for prolonged assisted ventilation. The measurement of the work of breathing against an inspiratory resistance of 5 cm H2O was useful in the identification and quantification of ventilatory reserve in patients with obstructive pulmonary disease.

Adult↗
PubMed1992

Site of pressure measurement during spontaneous breathing with continuous positive airway pressure: effect on calculating imposed work of breathing.

OBJECTIVE: To describe the importance of measuring pressure at the tracheal end of the endotracheal tube during spontaneous breathing with continuous positive airway pressure in order to correctly assess: a) the changes in airway pressure and b) the work imposed by the breathing apparatus. DESIGN: Multitrial tests under simulated clinical conditions using a mechanical lung model. SETTING: A research laboratory at a university medical center. INTERVENTIONS: Spontaneous breathing with continuous positive airway pressure, at peak sinusoidal inspiratory flow-rate demands of 30 and then 60 L/min with sizes 6, 7, 8, and 9 mm internal diameter endotracheal tubes at each flow rate. MEASUREMENTS AND MAIN RESULTS: Pressure, flow rate, and inhaled and exhaled volumes, during simulated spontaneous ventilation with continuous positive airway pressure were measured. Pressure was measured alternately at the "Y" piece of the breathing tubing of the continuous positive airway pressure system and at the tracheal end of the endotracheal tube to calculate the work imposed by the breathing circuit, endotracheal tube, and the total breathing apparatus. Greater changes in pressure and work were measured at the tracheal end of the endotracheal tube than at the "Y" piece of the breathing tubing for all test conditions. For example, at a peak inspiratory flow-rate demand of 30 L/min when pressures measured at the tracheal end of endotracheal tubes were compared with pressures measured at the "Y"piece, the total work imposed by the breathing apparatus increased by approximately 145% with a 6-mm tube, 95% with a 7-mm tube, 50% with an 8-mm tube, and 40% with a 9-mm tube (p less than .05). Measuring pressure at the "Y" piece of the tubing results in significant underestimations of the changes in pressure and the work imposed, especially when the endotracheal tube has a small internal diameter and/or when the peak inspiratory flow-rate demand is high. CONCLUSIONS: The results indicate that pressure should be measured as close to the patient's airway as possible, i.e., at the tracheal end of the endotracheal tube, rather than using the traditional approach of measuring pressure and assessing work at the inspiratory or expiratory limbs, or "Y" piece of the breathing tubing.

Humans↗
PubMed1990

[Methods in mixed ventilation: advantages, disadvantages and consequences for work of breathing].

During partial ventilatory support modes both the ventilator and the patient are performing mechanical work. These modes are currently used as mechanical ventilatory support to provide a better synchronism between the patient and the machine and to avoid a complete rest of the respiratory muscles, or as modes of weaning from mechanical ventilation. Assist control ventilation allows the patient to regulate his own respiratory rate by triggering preset ventilatory cycles. Synchronized intermittent mandatory ventilation includes both controlled cycles and spontaneous breathing cycles. Lastly, during inspiratory pressure support, each spontaneous cycle is assisted by pressurization of the circuit. This latter modality alone seems efficiently to decrease the patients' breathing work while allowing complete synchronism between patient and ventilator.

Humans↗
PubMed1992

The additional work of breathing through Portex Polar 'Blue-Line' pre-formed paediatric tracheal tubes.

The work of breathing through north- and south-facing Portex Polar 'Blue-Line' paediatric tracheal tubes of sizes 3.0-7.0 mm ID has been measured using sinusoidal flow at equivalent ventilatory rates of 10-50 breaths min-1 with tidal volumes of 10-500 ml. North-facing tubes are designed to sit with the connection on the forehead after intubation, whilst south-facing ones are designed so that the connection sits on the chin of the patient. It was found that the total work of breathing through north-facing tubes is approximately 8% higher than the total work of breathing through south-facing tubes of the same size, irrespective of tidal volume or respiration rate. The total work of breathing was dependent on total tube length but independent of tube design. The endotracheal connectors themselves were found to contribute a significant proportion of the total work of breathing but there was no significant difference between the inspiratory and expiratory performance of the tubes.

Anesthesiology↗
PubMed1985

The inspiratory work of breathing during assisted mechanical ventilation.

We quantified the mechanical work of breathing in six normal subjects during assisted mechanical ventilation. Using two volume-cycled ventilators of different design, we investigated the influence of minute ventilation (VE) and machine settings of trigger sensitivity and flow during CO2-driven hyperventilation to moderate and high levels (12-24 L/min). Work estimates were derived from plots of esophageal and airway pressure against inflation volume. Peak flow and trigger sensitivity were important determinants of the energy expended, and for each combination of machine settings the work done by the subject per liter of ventilation increased with VE. During assisted ventilation the subject expended energy equivalent to 33-50 percent of the work of passive inflation, even under the most favorable conditions of VE, sensitivity and flow. Under the least favorable conditions of VE, sensitivity and flow, the subject's inspiratory work of breathing substantially exceeded the energy needed by the ventilator to inflate the passive thorax. These observations imply that exertion of the respiratory muscles continues throughout inflation during assisted mechanical ventilation and call attention to the possibility that inappropriate selection of ventilatory mode or machine settings may contribute to respiratory muscle fatigue and dyspnea.

Adult↗
PubMed1989

The effects of airway impedance on work of breathing during halothane anesthesia.

Humidifiers and small diameter endotracheal tubes placed in the airway circuit increase the impedance to breathing. The effect of such impedances on the work of breathing and respiratory patterns was studied in eight healthy adult patients (60-80 kg) anesthetized with 1 and 2 MAC halothane in oxygen. A Cascade Humidifier and Portex Humid-Vent (dry and water saturated) were evaluated while patients breathed through an 8.0-mm endotracheal tube. A 6.0-mm endotracheal tube was also assessed without the humidifiers. At 1 MAC the Cascade Humidifier and the wet Humid-Vent when used with the 8.0-mm tube increased the work of breathing to 86.8 ml and 76.8 ml, 77% and 70% above baseline levels of 48.1 ml, whereas the 6.0-mm tube without the humidifiers increased work 89% to 78.9 ml. Tidal volume and respiratory frequency were unchanged throughout the study, although inspiratory time was prolonged. Lightly to moderately anesthetized healthy adult patients are able to maintain minute ventilation despite the impedance associated with commonly used humidifiers by significantly increasing work of breathing.

Anesthesia, Inhalation↗