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The role of spontaneous effort during mechanical ventilation: normal lung versus injured lung.

Yoshida T, Uchiyama A, Fujino Y - J Intensive Care (2015)

Bottom Line: Thus, increased transpulmonary pressure provides various benefits for gas exchange, ventilation pattern, and lung aeration.Thus, during the early stages of severe ARDS, the strict control of transpulmonary pressure and prevention of Pendelluft should be achieved with the short-term use of muscle paralysis.When there is preserved spontaneous effort in ARDS, spontaneous effort should be maintained at a modest level, as the transpulmonary pressure and the effect size of Pendelluft depend on the intensity of the spontaneous effort.

View Article: PubMed Central - PubMed

Affiliation: Intensive Care Unit, Osaka University Hospital, 2-15 Yamadaoka, Suita, Osaka 565-0871 Japan.

ABSTRACT
The role of preserving spontaneous effort during mechanical ventilation and its interaction with mechanical ventilation have been actively investigated for several decades. Inspiratory muscle activities can lower the pleural components surrounding the lung, leading to an increase in transpulmonary pressure when spontaneous breathing effort is preserved during mechanical ventilation. Thus, increased transpulmonary pressure provides various benefits for gas exchange, ventilation pattern, and lung aeration. However, it is important to note that these beneficial effects of preserved spontaneous effort have been demonstrated only when spontaneous effort is modest and lung injury is less severe. Recent studies have revealed the 'dark side' of spontaneous effort during mechanical ventilation, especially in severe lung injury. The 'dark side' refers to uncontrollable transpulmonary pressure due to combined high inspiratory pressure with excessive spontaneous effort and the injurious lung inflation pattern of Pendelluft (i.e., the translocation of air from nondependent lung regions to dependent lung regions). Thus, during the early stages of severe ARDS, the strict control of transpulmonary pressure and prevention of Pendelluft should be achieved with the short-term use of muscle paralysis. When there is preserved spontaneous effort in ARDS, spontaneous effort should be maintained at a modest level, as the transpulmonary pressure and the effect size of Pendelluft depend on the intensity of the spontaneous effort.

No MeSH data available.


Related in: MedlinePlus

Transition phase from spontaneous breathing to muscle paralysis in a rabbit. A lung-injured animal was ventilated with assisted pressure control mode. We recorded continuously waveforms of transpulmonary pressure, airway pressure, flow, and esophageal pressure without any change in ventilatory settings, after injection of neuromuscular blocking agent. When spontaneous breathing during mechanical ventilation is diminished, the negative swing in esophageal pressure is decreasing. As a result, inspiratory transpulmonary pressure decreases. Note that inspiratory transpulmonary pressure linearly correlates with the intensity of spontaneous breathing effort.
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Fig2: Transition phase from spontaneous breathing to muscle paralysis in a rabbit. A lung-injured animal was ventilated with assisted pressure control mode. We recorded continuously waveforms of transpulmonary pressure, airway pressure, flow, and esophageal pressure without any change in ventilatory settings, after injection of neuromuscular blocking agent. When spontaneous breathing during mechanical ventilation is diminished, the negative swing in esophageal pressure is decreasing. As a result, inspiratory transpulmonary pressure decreases. Note that inspiratory transpulmonary pressure linearly correlates with the intensity of spontaneous breathing effort.

Mentions: On the other hand, inspiratory muscle contraction can elevate PL with the same Paw applied in muscle paralysis (Figures 1 and 2). During mechanical ventilation, these two different types of pressure work to inflate the lung together. Thus, when spontaneous breathing is preserved during positive-pressure ventilation, negative changes in Ppl may be coupled with positive pressure changes from the ventilator, magnifying PL. For instance, when we deliver 20 cm H2O of inspiratory airway pressure by the mechanical ventilator, a negative change in Ppl is generated by inspiratory muscle contractions (for instance, −5 cm H2O) and is continued until the inspiratory airway pressure reaches its peak. As a result, PL is 25 cm H2O (Figure 1). These inspiratory muscle activities can lower the pleural components surrounding the lung, leading to an increase in PL when spontaneous breathing effort is preserved during mechanical ventilation [28]. Thus, spontaneous breathing is traditionally encouraged during mechanical ventilation [1,2] because it is thought to provide lung expansion at lower levels of Paw, which is a strategy that would result in better local (especially dependent) lung aeration, thereby enhancing gas exchange and potentially improving hemodynamics [2,5-7].Figure 2


The role of spontaneous effort during mechanical ventilation: normal lung versus injured lung.

Yoshida T, Uchiyama A, Fujino Y - J Intensive Care (2015)

Transition phase from spontaneous breathing to muscle paralysis in a rabbit. A lung-injured animal was ventilated with assisted pressure control mode. We recorded continuously waveforms of transpulmonary pressure, airway pressure, flow, and esophageal pressure without any change in ventilatory settings, after injection of neuromuscular blocking agent. When spontaneous breathing during mechanical ventilation is diminished, the negative swing in esophageal pressure is decreasing. As a result, inspiratory transpulmonary pressure decreases. Note that inspiratory transpulmonary pressure linearly correlates with the intensity of spontaneous breathing effort.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4940771&req=5

Fig2: Transition phase from spontaneous breathing to muscle paralysis in a rabbit. A lung-injured animal was ventilated with assisted pressure control mode. We recorded continuously waveforms of transpulmonary pressure, airway pressure, flow, and esophageal pressure without any change in ventilatory settings, after injection of neuromuscular blocking agent. When spontaneous breathing during mechanical ventilation is diminished, the negative swing in esophageal pressure is decreasing. As a result, inspiratory transpulmonary pressure decreases. Note that inspiratory transpulmonary pressure linearly correlates with the intensity of spontaneous breathing effort.
Mentions: On the other hand, inspiratory muscle contraction can elevate PL with the same Paw applied in muscle paralysis (Figures 1 and 2). During mechanical ventilation, these two different types of pressure work to inflate the lung together. Thus, when spontaneous breathing is preserved during positive-pressure ventilation, negative changes in Ppl may be coupled with positive pressure changes from the ventilator, magnifying PL. For instance, when we deliver 20 cm H2O of inspiratory airway pressure by the mechanical ventilator, a negative change in Ppl is generated by inspiratory muscle contractions (for instance, −5 cm H2O) and is continued until the inspiratory airway pressure reaches its peak. As a result, PL is 25 cm H2O (Figure 1). These inspiratory muscle activities can lower the pleural components surrounding the lung, leading to an increase in PL when spontaneous breathing effort is preserved during mechanical ventilation [28]. Thus, spontaneous breathing is traditionally encouraged during mechanical ventilation [1,2] because it is thought to provide lung expansion at lower levels of Paw, which is a strategy that would result in better local (especially dependent) lung aeration, thereby enhancing gas exchange and potentially improving hemodynamics [2,5-7].Figure 2

Bottom Line: Thus, increased transpulmonary pressure provides various benefits for gas exchange, ventilation pattern, and lung aeration.Thus, during the early stages of severe ARDS, the strict control of transpulmonary pressure and prevention of Pendelluft should be achieved with the short-term use of muscle paralysis.When there is preserved spontaneous effort in ARDS, spontaneous effort should be maintained at a modest level, as the transpulmonary pressure and the effect size of Pendelluft depend on the intensity of the spontaneous effort.

View Article: PubMed Central - PubMed

Affiliation: Intensive Care Unit, Osaka University Hospital, 2-15 Yamadaoka, Suita, Osaka 565-0871 Japan.

ABSTRACT
The role of preserving spontaneous effort during mechanical ventilation and its interaction with mechanical ventilation have been actively investigated for several decades. Inspiratory muscle activities can lower the pleural components surrounding the lung, leading to an increase in transpulmonary pressure when spontaneous breathing effort is preserved during mechanical ventilation. Thus, increased transpulmonary pressure provides various benefits for gas exchange, ventilation pattern, and lung aeration. However, it is important to note that these beneficial effects of preserved spontaneous effort have been demonstrated only when spontaneous effort is modest and lung injury is less severe. Recent studies have revealed the 'dark side' of spontaneous effort during mechanical ventilation, especially in severe lung injury. The 'dark side' refers to uncontrollable transpulmonary pressure due to combined high inspiratory pressure with excessive spontaneous effort and the injurious lung inflation pattern of Pendelluft (i.e., the translocation of air from nondependent lung regions to dependent lung regions). Thus, during the early stages of severe ARDS, the strict control of transpulmonary pressure and prevention of Pendelluft should be achieved with the short-term use of muscle paralysis. When there is preserved spontaneous effort in ARDS, spontaneous effort should be maintained at a modest level, as the transpulmonary pressure and the effect size of Pendelluft depend on the intensity of the spontaneous effort.

No MeSH data available.


Related in: MedlinePlus