Lung recruitment--a guide for clinicians.
ABSTRACT Recruitment manoeuvres play an important role in minimising ventilator associated lung injury (VALI) particularly when lung protective ventilation strategies are employed and as such clinicians should consider their application. This paper provides evidence-based recommendations for clinical practice with regard to alveolar recruitment. It includes recommendations for timing of recruitment, strategies of recruitment and methods of measuring the efficacy of recruitment manoeuvres and contributes to knowledge about the risks associated with recruitment manoeuvres. There are a range of methods for recruiting alveoli, most notably by manipulating positive end expiratory pressure (PEEP) and peak inspiratory pressure (PIP) with consensus as to the most effective not yet determined. A number of studies have demonstrated that improvement in oxygenation is rarely sustained following a recruitment manoeuvre and it is questionable whether improved oxygenation should be the clinician's goal. Transient haemodynamic compromise has been noted in a number of studies with a few studies reporting persistent, harmful sequelae to recruitment manoeuvres. No studies have been located that assess the impact of recruitment manoeuvres on length of ventilation, length of stay, morbidity or mortality. Recruitment manoeuvres restore end expiratory lung volume by overcoming threshold opening pressures and are most effective when applied after circuit disconnection and airway suction. Whether this ultimately improves outcomes in adult or paediatric populations is unknown.
- [show abstract] [hide abstract]
ABSTRACT: To compare the effects of two different recruitment maneuvers repeated multiple times on gas exchange lung injury, hemodynamic, and lung mechanics. Randomized prospective comparison. Animal research laboratory. Nineteen fasted Hampshire sheep. In 15 27-kg sheep with saline lavage lung injury, we compared the effects of two recruitment maneuvers: 40 cm H2O continuous positive airway pressure for 60 secs and 40 cm H2O positive end-expiratory pressure with 20 cm H2O pressure control, rate 10 breaths/min, inspiratory to expiratory ratio 1:1 for 2 mins. Each recruitment maneuver was repeated four times, every 30 mins after a 30-sec ventilator disconnection. An additional group received no recruitment maneuvers. Animals were assigned randomly to the three groups and ventilated with 20 cm H2O positive end-expiratory pressure, pressure control 15 cm H2O, rate 20 breaths/min, inspiratory to expiratory ratio 1:1, and Fio2 1.0 between recruitment maneuver periods. Significant and marked increases in Pao2 were observed in the pressure control recruitment maneuver group but only after the second recruitment maneuver. In both the control group and continuous positive airway pressure groups, Pao2 did not significantly increase after any recruitment maneuver compared with baseline injury. There was a significant decrease in cardiac output immediately after some continuous positive airway pressure recruitment maneuvers and a significant increase in mean pulmonary artery pressure in both continuous positive airway pressure and pressure control groups immediately after recruitment maneuvers, but these changes resolved within 10 mins. There were no marked histologic differences between groups and no volutrauma. In this model, maximal lung recruitment was obtained with 40 cm H2O positive end-expiratory pressure and 20 cm H2O pressure control applied repetitively every 30 mins for 2 mins without physiologic or histologic harm. Multiple recruitment maneuvers in some animals were required for maximum effect.Critical Care Medicine 09/2001; 29(8):1579-86. · 6.12 Impact Factor
- [show abstract] [hide abstract]
ABSTRACT: Recruitment maneuvers (RM) are advocated as a complement to mechanical ventilation during anesthesia and in acute lung injury. However, they produce high intrathoracic pressures and volumes that may compromise hemodynamics. Our aim was to analyze the effect of a RM on hemodynamics in 10 anesthetized pigs. We assessed carotid, pulmonary, femoral, and hepatic arterial pressures, hepatic and portal venous pressures, total splanchnic (celiac trunk + superior mesenteric artery), hepatic, splenic, renal, and carotid arterial flows, and portal venous flow. We recorded hemodynamics, respiratory mechanics and blood gases before and at 8 min after RM (sustained inflation to 40 cm H(2)O of airway pressure lasting 20 s). Hemodynamics were also measured during RM, and at 1, 3, and 5 min after RM. All flows (P = 0.030) and arterial pressures (P < or = 0.048) decreased during RM, whereas venous pressures increased (P = 0.030). Flows and pressures returned to 75%-109% of baseline immediately after RM. Total splanchnic, renal and portal flows remained decreased at 8 min after RM (P < or = 0.042). Oxygenation did not change, and respiratory mechanics improved after the RM. RM produced a marked, though transitory, impairment of blood flow in all studied vessels. Despite prompt partial recovery, total splanchnic circulation remained reduced at 8 min after RM. This residual decrease may present a risk in conditions with markedly compromised circulatory reserves. IMPLICATIONS: Recruitment maneuvers (RM) produce high intrathoracic pressures and volumes that may compromise hemodynamics. We found a marked transient impairment of hemodynamics during a RM in 10 anesthetized pigs. At 8 min after RM, blood flow remained reduced in the celiac trunk, superior mesenteric, and renal arteries, as well as in the portal vein. This residual decrease may present a risk in conditions with markedly compromised circulatory reserves.Anesthesia & Analgesia 06/2004; 98(5):1432-8, table of contents. · 3.30 Impact Factor
- [show abstract] [hide abstract]
ABSTRACT: We examined the effect of ventilation strategy on lung inflammatory mediators in the presence and absence of a preexisting inflammatory stimulus. 55 Sprague-Dawley rats were randomized to either intravenous saline or lipopolysaccharide (LPS). After 50 min of spontaneous respiration, the lungs were excised and randomized to 2 h of ventilation with one of four strategies: (a) control (C), tidal volume (Vt) = 7 cc/kg, positive end expiratory pressure (PEEP) = 3 cm H2O; (b) moderate volume, high PEEP (MVHP), Vt = 15 cc/kg; PEEP = 10 cm H2O; (c) moderate volume, zero PEEP (MVZP), Vt = 15 cc/kg, PEEP = 0; or (d) high volume, zero PEEP (HVZP), Vt = 40 cc/kg, PEEP = 0. Ventilation with zero PEEP (MVZP, HVZP) resulted in significant reductions in lung compliance. Lung lavage levels of TNFalpha, IL-1beta, IL-6, IL-10, MIP-2, and IFNgamma were measured by ELISA. Zero PEEP in combination with high volume ventilation (HVZP) had a synergistic effect on cytokine levels (e.g., 56-fold increase of TNFalpha versus controls). Identical end inspiratory lung distention with PEEP (MVHP) resulted in only a three-fold increase in TNFalpha, whereas MVZP produced a six-fold increase in lavage TNFalpha. Northern blot analysis revealed a similar pattern (C, MVHP < MVZP < HVZP) for induction of c-fos mRNA. These data support the concept that mechanical ventilation can have a significant influence on the inflammatory/anti-inflammatory milieu of the lung, and thus may play a role in initiating or propagating a local, and possibly systemic inflammatory response.Journal of Clinical Investigation 04/1997; 99(5):944-52. · 12.81 Impact Factor