Protective ventilation in a pig model of acute lung injury: timing is as important as pressure.

Ventilator-induced lung injury (VILI) is a significant risk for patients with acute respiratory distress syndrome (ARDS). Management of the patient with ARDS is currently dominated by the use of low tidal volume mechanical ventilation, the presumption being that this mitigates overdistension (OD) injury to the remaining normal lung tissue. Evidence exists, however, that it may be more important to avoid cyclic recruitment and derecruitment (RD) of lung units, although the relative roles of OD and RD in VILI remain unclear. Forty pigs had a heterogeneous lung injury induced by Tween instillation and were randomized into four groups (n = 10 each) with higher (↑) or lower (↓) levels of OD and/or RD imposed using airway pressure release ventilation (APRV). OD was increased by setting inspiratory airway pressure to 40 cmH2O and lessened with 28 cmH2O. RD was attenuated using a short duration of expiration (∼0.45 s) and increased with a longer duration (∼1.0 s). All groups developed mild ARDS following injury. RD ↑ OD↑ caused the greatest degree of lung injury as determined by [Formula: see text]/[Formula: see text] ratio (226.1 ± 41.4 mmHg). RD ↑ OD↓ ([Formula: see text]/[Formula: see text]= 333.9 ± 33.1 mmHg) and RD ↓ OD↑ ([Formula: see text]/[Formula: see text] = 377.4 ± 43.2 mmHg) were both moderately injurious, whereas RD ↓ OD↓ ([Formula: see text]/[Formula: see text] = 472.3 ± 22.2 mmHg; P < 0.05) was least injurious. Both tidal volume and driving pressure were essentially identical in the RD ↑ OD↓ and RD ↓ OD↑ groups. We, therefore, conclude that considerations of expiratory time may be at least as important as pressure for safely ventilating the injured lung.NEW & NOTEWORTHY In a large animal model of ARDS, recruitment/derecruitment caused greater VILI than overdistension, whereas both mechanisms together caused severe lung damage. These findings suggest that eliminating cyclic recruitment and derecruitment during mechanical ventilation should be a preeminent management goal for the patient with ARDS. The airway pressure release ventilation (APRV) mode of mechanical ventilation can achieve this if delivered with an expiratory duration (TLow) that is brief enough to prevent derecruitment at end expiration.

Bacterial colonization of respiratory therapists' pens in the intensive care unit.

BACKGROUND: Prevention of nosocomial infections is of paramount importance. Person-to-person transmission of microorganisms is well recognized, but the role of fomites in nosocomial infection is not as well understood. Incomplete cleaning of equipment and patient rooms, and medical devices used with multiple patients are well-described means of transmission, but little attention has been paid to nonmedical devices as fomites. We collected bacteria from writing implements (pens) used by respiratory therapists in an intensive care unit, following their work shifts. METHODS: We obtained pens from 20 respiratory therapists, and cultured, enumerated, and identified the bacteria. RESULTS: Bacteria were found on 17 of the 20 pens. The mean +/- SD number of colony-forming units was 126 +/- 277 (range 0-1,250). Coagulase-negative staphylococci were found on all 17 pens. Micrococcus species were found on 4 pens. CONCLUSIONS: Although we found no organisms that are regularly associated with nosocomial infections (eg, methicillin-resistant Staphylococcus aureus or Gram-negative bacilli), pens can be fomites responsible for nosocomial infections. Protocols to reduce the transmission of infectious agents may need to be extended to writing instruments. One possible measure is to assign specific writing instruments to specific rooms.