Protective Ventilation

Intraoperative Spontaneous Breathing

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As Your Specialist in Acute Care we understand that over the past two decades it has become a well-established fact that general anaesthesia, although considered safe, may impair the respiratory system. Neuromuscular blockade and subsequent controlled ventilation is suspected to be a major cause of respiratory impairment. Apart from parameters for controlled ventilation, intraoperative spontaneous breathing may well be one of the options for further improvement.

Is spontaneous breathing also an aspect of protective ventilation during general anaesthesia?

Thus far, the discussion on protective ventilation in the OR has focussed on how parameters of mechanical ventilation can be optimised to protect a patient’s lungs. But isn’t there more to this topic than parameters of mandatory mechanical ventilation? Wouldn’t spontaneous breathing be more beneficial, either as early as possible towards the end of general anaesthesia or as soon as possible after securing the airway?

Infographic: Intraoperative spontaneous breathing

The positive impacts of intraoperative spontaneous breathing receive more and more attention. Find interesting background information in our infographic.

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Managing the onset of spontaneous breathing during recovery

Emergence from anaesthesia and the entire postoperative phase are critical periods where pulmonary complications are most frequent. Anaesthesiologists usually strive to keep the depth of anaesthesia as flat as the surgical procedure allows. Towards the end of surgery, the anaesthesiologist discontinues anaesthetic delivery to allow for spontaneous breathing and a subsequent extubation. The wash out of volatile anaesthetic drugs may be performed gradually or quickly by means of high fresh-gas flows and/or hyperventilation. The latter happens at a cost of a decreased PaCO₂ and the subsequent risk of reduced cerebral blood flow. In addition, this quick approach may not leave sufficient time for appropriate drug redistribution from less perfused tissues with higher solubility. A rise of anaesthetic drug levels in the central compartments and a subsequent respiratory depression in the recovery room could follow. Furthermore, lowering PaCO₂ reduces respiratory drive and may delay the return of spontaneous breathing^{4, 5}.

The transition from mandatory ventilation to spontaneous breathing is a common and important aspect of general anaesthesia

A smoother approach to emergence could be the reduction of the depth of anaesthesia well before the end of surgery, promoting the early onset of spontaneous breathing. Particularly after long cases, the reduction in the depth of anaesthesia may be initiated earlier rather than later. Consequently, spontaneous breathing may also return earlier but is likely to be insufficient to maintain proper arterial oxygenation. To prevent hypoxaemia during this phase, adequate support for the spontaneous breathing effort may be beneficial6. It has been stated that spontaneous breathing during general anaesthesia is associated with hypercapnic acidosis and an increased work of breathing in both healthy patients and those with known comorbidities. In order to smooth this process, assisted ventilation modes have been introduced in anaesthesia machines. Pressure support ventilation (PSV) is now commonly available and is intended to support spontaneous breathing while reducing patient-ventilator dysynchrony6. Beyond this, PSV has also been shown to provide more effective gas exchange compared to unassisted CPAP ventilation during anaesthesia with a laryngeal mask airway (LMA). PSV supports the achievement of optimal tidal volumes and, in comparison to unassisted spontaneous breathing, increases minute volume, lowers etCO₂ and improves oxygenation^{6, 7}. In addition, PSV-supported intraoperative spontaneous breathing was found to reduce LMA removal time, emergence time and even Propofol consumption6.

Technology Insights: Spontaneous Breathing in Recovery

This article provides background information on technical ways to support spontaneous breathing during recovery.

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SVC helps maximize spontaneous breathing

Smart Ventilation Control (SVC) supports the patient-oriented transition between fully controlled, assisted and spontaneous breathing. This clinical-knowledge based assistance system can automatically reduce the ventilator support until the patient is ready for extubation.

Video: The Smart Ventilation Assistant - Dräger SVC

SVC is an anaesthetist assist system developed together with clinicians to control ventilation throughout the whole operation, from intubation to extubation.

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The Big Impact of Lung Protective Ventilation

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Get a deeper understanding of how to fit every patient’s lung ventilation needs and learn how you can improve patient outcomes whilst maximising hospital’s resources.

Get in touch with Dräger

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References

Neuman P, Wrigge H. et al. Spontaneous breathing affects the spatial ventilation and perfusion distribution during mechanical ventilatory support. Crit Care Med 2005 Vol. 33, 5
Brimacombe J, Keller C, Hörmann C. Pressure support ventilation versus continuous positive airway pressure with the laryngeal mask airway: a randomized crossover study of anesthetized adult patients. Anesthesiology. 2000 Jun;92(6):1621-3
Capdevila X, Jung B, Bernard N, Dadure C, Biboulet P, Jaber S. Effects of pressure support ventilation mode on emergence time and intra-operative ventilatory function: a randomized controlled trial. PLoS One. 2014 Dec 23;9(12):e115139
Röpcke H, Wartenberg HC. Inducing spontaneous respiration at the end of surgery Anasthesiol Intensivmed Notfallmed Schmerzther. 2000 Jul;35(7):459-60.
Sakata DJ, Gopalakrishnan NA, Orr JA, et al. Hypercapnic hyperventilation shortens emergence time from isoflurane anesthesia. Anesth Analg. 2007 Mar;104(3):587-91.
Capdevila X, Jung B, Bernard N, et al. Effects of pressure support ventilation mode on emergence time and intra-operative ventilatory function: a randomized controlled trial. PLoS One. 2014 Dec 23;9(12):e115139.
Brimacombe J, Keller C, Hörmann C. Pressure support ventilation versus continuous positive airway pressure with the laryngeal mask airway: a randomized crossover study of anesthetized adult patients. Anesthesiology. 2000 Jun;92(6):1621-3.