Critical care ultrasound (CCUS) is an extension of the physical examination. The front-line clinician performs, interprets, and applies goal-directed examinations to rapidly diagnose and manage life-threatening conditions, including acute respiratory failure and undifferentiated shock. The American College of Chest Physicians/La Société de Ré animation de Langue Francaise Statement on Competence in Critical Care Ultrasonography (ACCP/SRLF Statement) highlights five areas of focus for intensivists: cardiac, thoracic (consisting of both the lungs and the pleura), vascular (consisting of both diagnostic and vascular access), and abdominal ultrasound.1 CCUS examinations are not comprehensive examinations that evaluate all anatomic structures and measurements of an organ or body region.
This chapter serves as a brief overview of the most common uses of CCUS. In no way is it meant to be completely comprehensive; however, it serves as an adequate introductory tool and covers the material most frequently tested on the American Board of Internal Medicine Pulmonary and Critical Care board examinations.
It is imperative to have an easily accessible and portable machine that allows for rapid and repeated use. Machines ideally should have a high-frequency vascular probe (Fig. 31-1A) and low-frequency phased array probe (Fig. 31-1B). Appropriate manufacturer warranty and technical support should be included in the purchase because of heavy use and the high likelihood for maintenance.
(A) Note the difference in length of blue lines in diastole and systole indicating the change in thickness of myocardial wall of the interventricular septum. Arrow points to the descending thoracic aorta. (B) Note the difference in LV cavity size in systole and diastole. (C) Note the close approximation of the anterior leaflet of mitral valve to the interventricular septum (arrow). AV, aortic valve; DTA, descending thoracic aorta; LA, left atrium; LV, left ventricle; MV, mitral valve; RVOT, right ventricular outflow tract.
OPERATOR POSITION, MARKER ORIENTATION, AND KNOBOLOGY
It is imperative to develop a consistent approach when obtaining, describing, and interpreting ultrasound images. If possible, the operator should always be positioned immediately down- or upstream (adjacent) to the system console, allowing for ease of image acquisition and manipulation. When appropriate (if possible), patient position should be optimized for the current examination (eg, when possible, goal-directed echocardiography GDE should be performed with the patient in the left lateral decubitus position).
Operators should familiarize themselves with the various functions of the ultrasound interface. For basic CCUS, one must master the functions that manipulate image position (depth) and brightness (gain). Depth should be adjusted so that the structure of interest (eg, the heart) occupies the center of the screen. Gain can be increased or decreased to make structures brighter or darker, respectively. Machines often have near, far, and full screen gain adjustment.