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Ventilation 7 patient-ventilator dyssynchrony
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- 2. Background • Main purposeof ventilator is to decrease the work of breathing • What is work of breathing
- 3. Work of Breathing •respiratory muscles account for 1% to 3% of total oxygen consumption • In patients with acute hypoxemic respiratory failure and shock who are undergoing cardiopulmonary resuscitation, the respiratory muscles account for approximately 20% of total oxygen consumption • This is result of increased work of breathing
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- 6. Facial signs ofrespiratory distress
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- 10. Campbell diagram asused to calculate work of breathing (WOB). Dean R Hess Respir Care 2014;59:1773-1794 (c) 2012 by Daedalus Enterprises, Inc.
- 11. Trigger-Related Dyssynchrony • Trigger-RelatedDyssynchrony • Trigger threshold is too high • Muscle weakness • Outside extra flow in VAC ventilation • Auto PEEP • Expiratory flow limitation • Extra Triggering
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- 18. Cycle-Related Dyssynchrony • Theduration of inspiratory muscle contraction leading to inspiration is known as the patient’sneural inspiratory time (neural TI).
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Editor's Notes
- #4 Asthma, chronic obstructive pulmonary disease (COPD), pneumonia, cardiogenic pulmonary edema, and acute respiratory distress syndrome (ARDS) are just a few of the many conditions that cause an increase in work of breathing and, with it, increased energy expenditure by the respiratory muscles.
- #5 The energy expenditure of the respiratory muscles can be quantified in terms of pressure-time product 2 —the time integral of the difference between the esophageal pressure tracing and the estimated recoil pressure of the chest wall 3 , 4 ( Fig. 4-1 ). The pressure-time product of patients in acute respiratory failure is about four times 5 – 7 the normal value (100 cm H 2 O・s/min), and it can be increased sixfold in individual patients. 5 , 6 The inspiratory pressure-time product can be partitioned into resistive, elastic, and intrinsic positive end-expiratory pressure (PEEP) components ( Fig. 4-1 ). 6 Patients in respiratory distress typically have a 30% to 50% greater inspiratory resistance, 6 100% greater dynamic elastance, 6 and 100% to 200% greater intrinsic PEEP 5 , 6 than do similar patients who are not in acute respiratory failure. Inspiratory effort is almost equally divided in offsetting intrinsic PEEP, elastic recoil, and inspiratory resistance. 6 The increase in respiratory effort means that the respiratory muscles account for a much larger fraction of the body’s oxygen consumption. In healthy subjects, this fraction is only 1% to 3% of total oxygen consumption. In patients with acute hypoxemic respiratory failure and shock who are undergoing cardiopulmonary resuscitation, the respiratory muscles account for approximately 20% of total oxygen consumption. 8
- #6 Respiratory effort during unassisted respiration. Recordings of flow ( inspiration upward ), esophageal ( Pes ), gastric ( Pga ), and transdiaphragmatic ( Pdi ) pressures and electrical activity of the diaphragm ( Edi ) in a stable patient with COPD ( left ) and in a patient with respiratory failure ( right ). The green vertical lines indicate the onset of inspiratory flow and the red vertical lines indicate the onset of expiratory flow. The excursions in Pes and Edi in the patient in respiratory failure are three times greater than in the stable patient, signifying heightened respiratory motor output. The increase in Pga during exhalation in the patient with respiratory failure signifies expiratory muscle recruitment.
- #9 Recordings of flow ( inspiration upward ), rib cage ( RC ), and abdominal ( Ab ) cross-sectional areas in two patients in respiratory distress. The green vertical lines indicate the onset of inspiratory flow and the red vertical lines indicate the onset of expiratory flow. On the left , expansion of the rib cage is occurring faster than expansion of the abdomen (asynchrony). On the right , while the rib cage expands during inspiration, the abdominal cross-sectional area is getting smaller (paradox).
- #11 Campbell diagram as used to calculate work of breathing (WOB). The green area represents elastic WOB, and the blue area represents resistive WOB. The total shaded area represents total WOB.
- #12 Pressure-volume curve of a normal subject (dashed curve) and of a patient with ARDS (solid curve). The pressure-volume curve is shifted downwards on the volume axis and has a reduced total lung capacity (TLC). The sigmoid shape of the curve is much more evident in ARDS. Note the small amount of pressure at the start of the ARDS pressure-volume curve, indicating a small amount of intrinsic PEEP (PEEPi) at end-expiratory lung volume (EELV). Some investigators divide the curve into linear segments: Cstart, Cinf or Clin, and Cend (explained below). Using these segments, the upper and lower Pflex (the pressure at the intersection of 2 lines: a low compliance region at low lung volumes [Cstart] and a higher compliance region at higher lung volumes [Cinf]) were defined by the intersection of these lines. The lower (LIP) and upper (UIP) inflection points are defined by where the curve first begins to deviate from the line Clin. Mathematically, these are not inflection points; the true inflection point (where concavity changes direction) is marked by the arrow. FRC = functional residual capacity. From Reference 47.
- #14 Figure 7.1 Respiratory circuit demonstrating the flow trigger mechanism. (a) A continuous amount of gas flows from the inspiratory limb to the expiratory limb of the ventilator. (b) A patient’s inspiratory effort will cause some of the gas flow to enter the patient instead of returning to the ventilator. If the reduction in flow returning to the ventilator is above the flow trigger threshold, the inspiratory effort would trigger the ventilator. (c) The use of continuous-flow nebulizer treatments adds additional flow into the inspiratory limb of the respiratory circuit. In order for the patient to successfully trigger the ventilator, the patient must inspire all of the flow delivered by the nebulizer, in addition to the threshold amount of continuous flow from the inspiratory limb of the ventilator that is destined for the expiratory limb.
- #19 Flow and pressure waveforms of a flow-targeted mode demonstrating the response to a sustained patient inspiratory effort. A patient inspiratory effort, which decreases alveolar pressure, will not affect the flow waveform because the flow waveform is set in flow-targeted mode. Instead, there will be a decrease in proximal airway pressure during the inspiratory effort, as represented by a divot in the pressure waveform.