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ARDS and ALI
Published in T.M. Craft, P.M. Upton, Key Topics In Anaesthesia, 2021
The principles of mechanical ventilation are to provide adequate oxygenation and CO2 removal while minimizing the risk of barotrauma and volutrauma. Dependent, collapsed alveoli should be recruited using positive end expiratory pressure (PEEP) of 5-18 cmH2O. The use of prolonged inspiratory times (i.e., inverse ratio ventilation) will increase intrinsic PEEP (PEEPi) and may be beneficial. Relatively small tidal volumes (< 7 ml kg-1) will minimize peak inspiratory pressures and reduce the potentially damaging shear forces in the alveoli. Inspired O2 concentrations should be reduced to 0.5 as soon as possible by setting targets for acceptable hypoxaemia (e.g. SaO2> 0.88).
Critical care, neurology and analgesia
Published in Evelyne Jacqz-Aigrain, Imti Choonara, Paediatric Clinical Pharmacology, 2021
Evelyne Jacqz-Aigrain, Imti Choonara
There are many indications for the administration of neuromuscular blocking agents in the paediatric intensive care unit (PICU) and these are summarised in Table 1. The most common indications are to facilitate endotracheal intubation and to prevent patient-ventilator dyssynchrony, particularly during “unphysio-logical” techniques such as high frequency oscillatory ventilation, inverse ratio ventilation or controlled hypoventilation. Other indications centre around the management of specific clinical conditions.
Postoperative respiratory complications
Published in Hemanshu Prabhakar, Charu Mahajan, Indu Kapoor, Manual of Neuroanesthesia, 2017
Zulfiqar Ali, Yasir N. Shah, Hemanshu Prabhakar
Pressure-controlled inverse ratio ventilation (PC-IRV) and ventilation in prone position may be used in refractory cases. In PC-IRV, the inspiratory time (I) is prolonged until it is equal to or greater than expiratory time (E), for example, using an I/E ratio of 1:1, 2:1, or 3:1. The physiological rationale of prone ventilation is that it optimizes lung recruitment and ventilation perfusion matching while preventing alveolar overinflation and allowing better postural drainage. Dramatic improvements in oxygenation are often observed in patients who are turned into the prone position for several hours, and this improvement may be sustained when they are returned to the supine position. The technique should be used for 12–24 h. However, there are practical difficulties in turning the critically ill patient and in nursing the patient in the prone position.
Effects of inverse ratio ventilation combined with lung protective ventilation on pulmonary function in patients with severe burns for surgery
Published in Libyan Journal of Medicine, 2020
Yan-Chao Yang, Qiao Huai, Shu-Zhen Cui, Xiao-Wei Cao, Bu-Lang Gao
The inverse ratio ventilation is well known to improve arterial oxygenation in acute respiratory distress syndrome, reduce intrapulmonary shunt, recruit atelectatic alveoli, improve ventilation, and decrease dead space ventilation [9]. Increase of the inspiratory time permits sufficient time to gas exchange. At the same time, short expiratory time in inverse ratio ventilation allows air trapped in the lungs for generation of intrinsic PEEP or auto-PEEP. Moreover, the PEEP generated in inverse ratio ventilation can improve oxygenation, contributing to advantageous effects on pulmonary mechanics [19,20]. The inverse ratio ventilation with increased inspiratory time can also increase the mean distribution time to facilitate distribution and mixture of inhaled gas within the lungs and to enhance CO2 elimination. Increasing the inspiratory time does not affect elimination of CO2 which is probably associated with blood absorption of CO2. This is why there was a significant increase in OI, a significant decrease in D(A-a)O2 but no significant difference in the PaCO2 between the EG with inverse ratio ventilation and CG in this study. In this study, the I:E ratio of 2:1 used is considered as the optimal ratio. Sari et al. [15] studied the effects of alteration of the I:E and found that stepwise prolongation of the I:E ratio from 1:1.9 to 2:1 had significantly decreased the intrapulmonary shunting, whereas increase of the I:E from 2.1 to 2.6 or at 4:1 had not further decreased the intrapulmonary shunting. Therefore, the I:E ratio at 2:1 was used in this study and had proved its effects in improving oxygenation and protecting the lung.