Relation of increased airway resistance to breathing work and breath velocity and acceleration patterns with maximum and near maximum breathing effort.
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Acceleration↗
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The effect of incentive spirometry on chest expansion and breathing work in patients with chronic obstructive airway diseases: comparison of two methods.
BACKGROUND: Chronic obstructive airway diseases (COAD), characterized by mucus hypersecretion, lead to exercise intolerance. Incentive spirometry has been used to prevent postoperative pulmonary atelectasis. METHODS: To compare the efficacy of two incentive spirometers, Coach (volume-oriented) and Triflo (flow-oriented), in the work of breathing in COAD patients, 22 patients were randomized in this study: 12 patients (Triflo-II group) initially used Triflo-II for 10 minutes and then Coach for the same period. In contrast, the Coach group, including 10 patients, started with Coach followed by Triflo-II. After receiving incentive spirometry, lung expansion and work of breathing were assessed. RESULTS: Patients in the Coach group significantly increased chest wall expansion (p = 0.041), as compared with patients using Triflo-II. Similarly, there was also a significantly increased abdominal wall expansion in the Coach group (p = 0.0056), compared with that in the Triflo-II group. The need of accessory muscle assistance for breathing in the Coach group was significantly less than in the Triflo-II group (p = 0.047). It was easier for patients in the Coach group to start a breath (p = 0.0058) than for those in the Triflo-II group. For the entire group, 17 patients (77.3%) preferred Coach to assist their breathing, and only 4 patients (18.2%) favored Triflo-II. CONCLUSION: COAD patients achieved a larger expansion of the chest and abdomen with a Coach device. Our data provide a good rationale for an outcome study on the use of incentive spirometer in COAD patients.
Adult↗
The effects of pressurization rate on breathing pattern, work of breathing, gas exchange and patient comfort in pressure support ventilation.
The aim of this study was to investigate the effects of different pressurization rates during pressure support ventilation on breathing pattern, work of breathing, gas exchange and patient comfort in patients with acute lung injury. The pressurization rate modifies the initial pressure ramp by changing the initial peak flow rate: the increase in pressurization rate is associated with a decrease in the time to reach the level of pressure support ventilation by increasing the peak flow rate. Ten intubated patients (age 64+/-17 yrs, body mass index 24+/-17 Kg x m(-2), arterial oxygen tension/inspired oxygen fraction 214+/-59) were studied in random order varying the pressurization rate at 5 and 15 cmH2O of pressure support ventilation. Breathing comfort was evaluated by a visual analogue scale. Increasing the pressurization rate caused an increase of peak flow rate from 473+/-141 mL x s(-1) to 758+/-302 mL x s(-1) at pressure support ventilation 5 (p<0.05) and from 481+/-126 mL x s(-1) to 1,121+/-175 mL x s(-1) at pressure support ventilation 15 (p<0.05). At the lowest pressurization rate the tidal volume was the lowest, the respiratory rate and the work of breathing were the highest (p<0.05) compared with other pressurization rates. Excluding the lowest pressurization rate, in all the other pressurization rates tested the breathing pattern and the work of breathing did not change. The lowest and the highest pressurization rates caused the worst patient comfort (p<0.05). The gas exchange was stable throughout the study. The presented results suggest: 1) the lowest pressurization rate caused the lowest tidal volume, highest respiratory rate and highest work of breathing; 2) at the other pressurization rates no differences in breathing pattern and work of breathing were observed; and 3) the patient's comfort was worse at the lowest and highest pressurization rates.
Adult↗
[Effect of noninvasive ventilation on work of breathing in obesity].
BACKGROUND: Noninvasive ventilation with nose- or face-masks has been increasingly used in the past. The objective of mechanical ventilation is in addition to improve gas exchange to reduce breathing work. While improvement on breathing work has been shown mainly on normal-weight patients with different respiratory diseases, there is no existing data about the effect of noninvasive ventilation on the breathing work of patients with massive obesity. PATIENTS AND METHODS: Assisted mask-ventilation with bilevel positive airway pressure (BiPAP) was carried out on 5 overweight control subjects (overweight controls), 7 overweight patients with obstructive sleep apnea (OSA), 6 patients with obesitas-hypoventilation syndrome (OHS), and 7 overweight patients with chronic obstructive lung disease (COLD). Inspiratory pressure assist (IPAP) was set to 12 or 16 cm H2O, exspiratory pressure (EPAP) was set to 5 cm H2O. All, subjects were massive overweight (body mass index [BMI] 42.2 +/- 5.8; range 31.8 to 55.4 kg/m2). Respiratory muscle activity was measured as esophageal pressure change (delta Pes) and transdiaphragmatic pressure change (delta Pdi) and calculated as pressure time integral. RESULTS: With noninvasive ventilation respiratory muscle activity was significantly (p < 0.05) reduced in all groups at least 40% compared to baseline values during spontaneous respiration. CONCLUSIONS: Noninvasive ventilation via face masks can efficiently reduce work of breathing in subjects with massive obesity.
Adult↗
[Breathing work in everyday nursing].
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Asthma↗
Effect of different levels of pressure support and proportional assist ventilation on breathing pattern, work of breathing and gas exchange in mechanically ventilated hypercapnic COPD patients with acute respiratory failure.
BACKGROUND: Proportional assist ventilation (PAV) has been shown to maintain better patient-ventilator synchrony than pressure support ventilation (PSV); however, its clinical advantage regarding invasive ventilation of COPD patients has not been clarified. OBJECTIVES: To compare the effect of PAV and PSV on respiratory parameters of hypercapnic COPD patients with acute respiratory failure (ARF). METHODS: Nine intubated hypercapnic COPD patients were placed on the PAV or PSV mode in random sequence. For each mode, four levels (L1-L4) of support were applied. At each level, blood gases, flow, tidal volume (VT), airway pressure (Paw), esophageal pressure (Pes) (n = 7), patient respiratory rate (fp), ventilator rate (fv), missing efforts (ME = fp - fv) were measured. RESULTS: We found increases in ME with increasing levels of PSV but not with PAV. PO2 and VT increased whereas PCO2 decreased significantly with increasing levels of PSV (p < 0.05). With PAV, PCO2 decreased and VT increased significantly only at L4 whereas PO2 increased from L1 to L4. Runaways were observed at L3 and L4 of PAV. The pressure-time product (PTP) was determined for effective and missing breaths. The mean total PTP per minute (of effective plus missing breaths) was 160 +/- 57 cm H2O/s.min in PSV and 194 +/- 60 cm H2O/s.min in PAV. CONCLUSION: We conclude that in COPD patients with hypercapnic ARF, with increasing support, PSV causes the appearance of ME whereas PAV develops runaway phenomena, due to the different patient-ventilator interaction; however, these do not limit the improvement of blood gases with the application of both methods.
Acute Disease↗
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↗
The effect of breath termination criterion on breathing patterns and the work of breathing during pressure support ventilation.
UNLABELLED: With pressure support ventilation (PSV), each PSV breath is flow-cycled, and the breath termination criterion (TC) is usually nonadjustable. When TC does not match the interaction between the patient's inspiratory-expiratory efforts to the opening and closing of the inspiratory and expiratory valves, patient-ventilator asynchrony may occur, and the work of breathing (WOB) may increase. Therefore, we studied the effect of TC on breathing patterns and WOB during PSV in eight patients with acute respiratory distress syndrome or acute lung injury. We studied five levels of TC during PSV-1%, 5%, 20%, 35%, and 45% of the peak inspiratory flow. With increasing levels of TC, the tidal volume decreased and respiratory frequency increased, along with a decrease in duty cycle. WOB markedly increased with increasing levels of TC from 0.31 +/- 0.12 J/L with TC 1% to 0.51 +/- 0.11 J/L with TC 45%. Premature termination with double breathing occurred in one patient with TC 35% and four patients with TC 45%. Delayed termination with a duty cycle of >0.5 occurred in two patients with TC 1%. In conclusion, the proper adjustment of TC improves patient-ventilator synchrony and decreases WOB during PSV. IMPLICATIONS: Although termination criterion (TC) is usually nonadjustable, it influences the effectiveness of pressure support ventilation for mechanical ventilation. The proper adjustment of TC is crucial to improve patient-ventilator synchrony and decrease work of breathing. TC 5% of the peak inspiratory flow may be the optimal value for patients with acute respiratory distress syndrome or acute lung injury.
Aged↗
[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↗
Breathing pattern and additional work of breathing in spontaneously breathing patients with different ventilatory demands during inspiratory pressure support and automatic tube compensation.
OBJECTIVE: We designed a new ventilatory mode to support spontaneously breathing, intubated patients and to improve weaning from mechanical ventilation. This mode, named Automatic Tube Compensation (ATC), compensates for the flow-dependent pressure drop across the endotracheal tube (ETT) and controls tracheal pressure to a constant value. In this study, we compared ATC with conventional patient-triggered inspiratory pressure support (IPS). DESIGN: A prospective, interventional study. SETTING: A medical intensive care unit (ICU) and an ICU for heart and thoracic surgery in a university hospital. PATIENTS: We investigated two groups of intubated, spontaneously breathing patients: ten postoperative patients without lung injury, who had a normal minute ventilation (VE) of 7.6 +/- 1.7 l/min, and six critically ill patients who showed increased ventilatory demand (VE = 16.8 +/- 3.0 l/ min). INTERVENTIONS: We measured the breathing pattern [VE, tidal volume (VT), and respiratory rate (RR)] and additional work of breathing (WOBadd) due to ETT resistance and demand valve resistance. Measurements were performed under IPS of 5, 10, and 15 mbar and under ATC. RESULTS: The response of VT, RR, and WOBadd to different ventilatory modes was different in both patient groups, whereas VE remained unchanged. In postoperative patients, ATC, IPS of 10 mbar, and IPS of 15 mbar were sufficient to compensate for WOBadd. In contrast, WOBadd under IPS was greatly increased in patients with increased ventilatory demand, and only ATC was able to compensate for WOBadd. CONCLUSIONS: The breathing pattern response to IPS and ATC is different in patients with differing ventilatory demand. ATC, in contrast to IPS, is a suitable mode to compensate for WOBadd in patients with increased ventilatory demand. When WOBadd was avoided using ATC, the patients did not need additional pressure support.
Adult↗
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↗
A Gaussian method to improve work-of-breathing calculations.
The work of breathing is a calculated index of pulmonary function in ventilated patients that may be useful in deciding when to wean and when to extubate. However, the accuracy of the calculated work of breathing of the patient (WOBp) can suffer from artifacts introduced by coughing, swallowing, and other non-breathing maneuvers. The WOBp in this case will include not only the usual work of inspiration, but also the work of performing these non-breathing maneuvers. The authors developed a method to objectively eliminate the calculated work of these movements from the work of breathing, based on fitting to a Gaussian curve the variable P, which is obtained from the difference between the esophageal pressure change and the airway pressure change during each breath. In spontaneously breathing adults the normal breaths fit the Gaussian curve, while breaths that contain non-breathing maneuvers do not. In this Gaussian breath-elimination method (GM), breaths that are two standard deviations from that mean obtained by the fit are eliminated. For normally breathing control adult subjects, GM had little effect on WOBp, reducing it from 0.49 to 0.47 J/L (n = 8), while there was a 40% reduction in the coefficient of variation. Non-breathing maneuvers were simulated by coughing, which increased WOBp to 0.88 (n = 6); with the GM correction, WOBp was 0.50 J/L, a value not significantly different from that of normal breathing. Occlusion also increased WOBp to 0.60 J/L, but GM-corrected WOBp was 0.51 J/L, a normal value. As predicted, doubling the respiratory rate did not change the WOBp before or after the GM correction.(ABSTRACT TRUNCATED AT 250 WORDS)
Adult↗
Spontaneously breathing lung model comparison of work of breathing between automatic tube compensation and pressure support.
INTRODUCTION: Automatic tube compensation (ATC), a new ventilation mode that compensates for the work of breathing imposed by endotracheal tube resistance, recently became commercially available. METHODS: We conducted a laboratory study with a lung model and a Nellcor Puritan Bennett 840 ventilator to compare ATC and pressure-support ventilation (PSV). A bellows-in-a-box lung model simulated spontaneous breathing with the following settings: respiratory rate 10 breaths/min, inspiratory time 1.0 s, peak inspiratory flow 60 L/min without connecting to the ventilator and endotracheal tube (ETT). At each ETT size (5, 6, 7, 8 and 9 mm inner diameter) 100% ATC was compared with pressure support (PS) of 0, 2, 4, 6, 8, and 10 cm H(2)O at positive end-expiratory pressure (PEEP) of 0 and 5 cm H(2)O. The negative deflection (PI) of the "alveolar" pressure (ie, pressure inside the bellows, P(alv)) and the delay time were measured. The PI and total pressure-time product (PTP(tot)) integrated from P(alv) were analyzed. PTP(tot) was subdivided into PTP(trig) (the PTP from the beginning of inspiration to the minimum P(alv)) and PTP(supp) (the PTP from the minimum P(alv) to the return to baseline P(alv)). RESULTS: At PEEP of 0 cm H(2)O: with ETTs of 5, 6, and 7 mm the PI values with ATC corresponded to PS of 0-4 cm H(2)O; with the 8-mm ETT the PI values corresponded to PS of 0 cm H(2)O; with the 9-mm ETT the PI values corresponded to PS of 0-2 cm H(2)O. At PEEP of 5 cm H(2)O, with all ETT sizes the PI values corresponded to PS of 0 cm H(2)O. PTP(tot) and PTP(supp) of ATC corresponded to: PS of 2-4 cm H(2)O with the 5-mm ETT; PS of 2 cm H(2)O with the 6-mm ETT; PS of 0-2 cm H(2)O with the 7-mm ETT; and PS of 0 cm H(2)O with the 8- and 9-mm ETTs, at PEEP of 0 cm H(2)O. PEEP of 5 cm H(2)O was not tested for PTP. PTP(trig) with ATC showed comparable or greater values with each size of ETT. CONCLUSIONS: ATC with a Nellcor Puritan Bennett 840 ventilator provided inspiratory ventilatory support corresponding to PS of <or= 4 cm H(2)O, depending on ETT size, which was not enough to compensate for the work of breathing imposed by the ETT.
Humans↗
[Clinical study of imposed work of breathing caused by the breathing apparatus].
OBJECTIVE: The imposed work of breathing caused by the breathing apparatus (endotracheal tube, breathing circuit tubing, and ventilator's valves) may increase patient's work of breathing. To evaluate the imposed work may be useful to determine weaning. METHODS: Work of breathing was observed by Bicore CP-100 breathing monitor at different levels pressure support (PS), T piece and after extubation, and the PS level to compensate imposed work of breathing was computed. RESULTS: When PS level decreased, patient's work of breathing increased significantly. At PS O kPa, the patient's work of breathing increased 57%, which was caused by imposed work of apparatus. Because of the resistance of endotracheal tube, the patient's work of breathing increased 41% at T piece. The PS level that compensated for the imposed work was 0.7 kPa. CONCLUSIONS: When PS level was too low or T piece was applied, the imposed work of breathing caused by apparatus could markedly increase patient's work of breathing.
Adult↗
Tracheal pressure control provides automatic and variable inspiratory pressure assist to decrease the imposed resistive work of breathing.
OBJECTIVE: To evaluate the operation of a continuous positive airway pressure system by using tracheal airway pressure (PT) as the control signal for system operation (i.e., tracheal pressure control). DESIGN: Repeated measures. SETTING: University research laboratory. SUBJECTS: Twelve anesthetized, spontaneously breathing swine. INTERVENTIONS: Subjects were intubated and connected to a tracheal pressure control system (5 cm H2O continuous positive airway pressure). Varying inspiratory flow demands and degrees of partial endotracheal tube occlusion (25%, 50%, and 75%) were studied. Tracheal pressure control was compared with a conventionally controlled system (pressure from breathing circuit Y-piece [PY] used as control signal) during endotracheal tube occlusion. MEASUREMENTS AND RESULTS: Imposed resistive work of breathing (work to spontaneously inhale through endotracheal tube and ventilator circuit), work by ventilation system assisting inhalation, PT, PY, tidal volume, and inspiratory flow demands were measured. As inspiratory flow demands increased (range, 0.2-2.3 L/sec), pressure assist increased automatically (range, 5-40 cm H2O) as well as work of breathing by ventilation system assisting inhalation (range, 0.2-2.5 J/L). Imposed resistive work of breathing was nullified at the lower and was negligible at the higher flow demands. During endotracheal tube occlusion with a conventionally controlled system, PY was unchanged, whereas PT decreased (up to -15 cm H2O) and imposed resistive work of breathing increased (up to 1.05 J/L). With tracheal pressure control, PY increased automatically (range, 8-52 cm H2O), whereas PT varied slightly (range, 2 to -4.6 cm H2O). Imposed resistive work of breathing was negligible (range, 0-0.2 J/L). Breathing circuit pressure (PY), not pulmonary airway pressure (PT), increased significantly during tracheal pressure control. CONCLUSIONS: Tracheal pressure control results in automatic and variable levels of pressure assist to decrease imposed resistive work of breathing under conditions of varying spontaneous inspiratory flow demands and endotracheal tube occlusion. Conventional systems are potentially flawed when PY is used as the control signal because they do not function in this manner and do not accurately assess pulmonary airway pressure.
Animals↗
[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↗
Work of breathing after extubation.
Recently we showed that work of breathing was higher in the immediate period after extubation as compared with spontaneous breathing through an endotracheal tube. In this study, we evaluated the glottis and trachea as potential sites of increased airway resistance after extubation. We measured breathing pattern, work of breathing, and pressure time product in eight patients during weaning from mechanical ventilation. We acquired data during pressure support ventilation and spontaneous breathing via the ventilator, with the endotracheal tube in place, and after extubation. During bronchoscopy at the time of extubation, we examined the trachea and measured the cross-sectional area of the glottis. Work of breathing and pressure time product were significantly lower during pressure support ventilation as compared with spontaneous breathing after extubation (0.43 +/- 0.10 vs 1.49 +/- 0.10 J/L and 101 +/- 22 vs 299 +/- 30 cm H2O.s/min, respectively; p < 0.05). However, both indexes were significantly higher after extubation as compared with breathing through the endotracheal tube (1.49 +/- 0.10 vs 0.95 +/- 0.12 J/L, 299 +/- 31 vs 196 +/- 26 cm H2O.s/min respectively; p < 0.05). During bronchoscopy, no tracheal or glottic narrowing was detected. The glottic cross-sectional area was successfully measured in four patients at the onset of inspiration and found to be 140 +/- 15 mm2. This value was larger than the mean cross-sectional area of the endotracheal tubes used in these patients (50 mm2). We conclude that neither tracheal nor laryngeal disease caused the increase in work of breathing after extubation. Our data suggest that upper airway narrowing at a more proximal site, such as the oropharynx or velopharynx may be the cause of the increase in respiratory work.
Adult↗
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↗