Am. J. Respir. Crit. Care Med., Vol 154, No. 5, Nov 1996, 1543-1550.
Chest X-ray changes in air space disease are associated with parameters of mechanical ventilation in ICU patients
EW Ely, MM Johnson, C Chiles, JT Rushing, DL Bowton, RI Freimanis, RH Choplin and EF Haponik
Department of Medicine, Bowman Gray School of Medicine of Wake Forest University, Winston-Salem, North Carolina, USA.
To assess relationships between parameters of mechanical ventilation (MV)
and portable chest X-ray (CXR) measurements of lung length (LL) and
severity of air space disease, a prospective, randomized, blinded
comparison of 102 adults in a university hospital was performed. Each
patient received two portable, supine CXRs on different MV breaths within 5
min of one another. Ventilator parameters were recorded. All 204 CXRs were
randomly assorted and read independently by three radiologists. Air space
disease was considered more severe with pressure support ventilation (PSV)
breaths than with intermittent mandatory ventilation (IMV) breaths (p =
0.0003), and its extent correlated inversely with static compliance (p =
0.0001, r = -0.40). Among patients having CXRs on both IMV and PSV breaths,
15 of 67 (22%) had their overall degree of air space disease read
differently by one category (mild, moderate, or severe). Increases in LL
between the two CXRs were associated with increasing peak (p = 0.0038) or
mean (p = 0.0065) airway pressure, tidal volume (VT) (p = 0.022), and VT
per kilogram (p = 0.006). We conclude that lung volume changes during MV,
typically not noted nor controlled for during portable chest radiography,
may substantially alter the interpretation of air space disease and LL.
Physicians monitoring intensive care unit (ICU) patients with daily CXRs
should be aware of the variables influencing interpretation of portable
CXRs of ICU patients.
