TEST - Book of PDFs-01_Bowton_IIS Hypoxemic Resp Failure Bowton -CHEST 2016_CMS PC.pptx

01_Bowton_IIS Hypoxemic Resp Failure Bowton -CHEST 2016_CMS PC.pptx - 1

Pdf Summary

This document discusses the effects of positive end-expiratory pressure (PEEP) on cardiovascular and pulmonary systems in different clinical settings. It provides strategies for titrating PEEP based on patient conditions. The case presented is of a severely obese patient with hypoxemic respiratory failure due to influenza, who is placed on mechanical ventilatory support. Raising PEEP from 12 to 17 cm H2O leads to the patient becoming hypotensive. The most likely explanation for the hypotension is reduced right ventricular (RV) preload. The document explains that in patients with normal heart function, PEEP reduces both RV and left ventricular (LV) preload, resulting in a decrease in cardiac output. It warns against indiscriminate volume administration to hypotensive patients and cites studies showing that positive fluid balance is associated with worse outcomes in sepsis and ARDS patients.<br /><br />The document also discusses the effects of PEEP on lung injury. In most animal models, PEEP is protective, reducing shearing forces, recruitment-derecruitment, compression-induced inactivation of surfactant, and volutrauma. However, it notes that lung injury in ARDS is non-homogeneous and not adequately reflected by chest X-ray appearance or PaO2/FiO2 ratios. CT scans can reveal patterns of lung injury and help determine the ability to recruit lung units and susceptibility to overdistension.<br /><br />The document suggests titrating PEEP and tidal volume based on lower inflection point (LIP) and upper inflection point (UIP) on the pressure-volume curve. Keeping PEEP at or above LIP provides adequate lung recruitment while keeping plateau pressure under UIP avoids overdistension. It emphasizes the importance of ventilation on the steep linear portion of the pressure-volume curve.<br /><br />The document concludes by discussing the stress index and its association with cytokine generation in focal or lobar ARDS. Rapidly rising pressure at end-inspiration indicates the need for less PEEP or tidal volume to reduce lung injury. It suggests looking at the relationship between plateau pressure and PEEP, as well as the inflation curve, to determine the appropriate changes in ventilatory settings.

Keywords

positive end-expiratory pressure

PEEP

cardiovascular system

pulmonary system

titrating PEEP

hypotension

lung injury

pressure-volume curve

plateau pressure

ventilatory settings