Influence of lung collapse distribution on the physiologic response to recruitment maneuvers during noninvasive continuous positive airway pressure
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- Cammarota, G., Vaschetto, R., Turucz, E. et al. Intensive Care Med (2011) 37: 1095. doi:10.1007/s00134-011-2239-8
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Noninvasive continuous positive airway pressure (n-CPAP) has been proposed for the treatment of hypoxemic acute respiratory failure (h-ARF). Recruitment maneuvers were shown to improve oxygenation, i.e., the ratio of arterial oxygen tension to inspiratory oxygen fraction (PaO2/FiO2), during either invasive mechanical ventilation, and n-CPAP, with a response depending on the distribution of lung collapse. We hypothesized that, during n-CPAP, early h-ARF patients with bilateral (BL) distribution of lung involvement would benefit from recruitment maneuvers more than those with unilateral (UL) involvement.
To perform a recruitment maneuver, once a minute we increased the pressure applied to the airway from 10 cmH2O to 25 cmH2O for 8 s (SIGH). We enrolled 24 patients with h-ARF (12 BL and 12 UL) who underwent four consecutive trials: (1) 30 min breathing through a Venturi mask (VMASK), (2) 1 h n-CPAP (n-CPAP1), (3) 1 h n-CPAP plus SIGH (n-CPAPSIGH), and (4) 1 h n-CPAP (n-CPAP2).
Compared to VMASK, n-CPAP at 10 cmH2O delivered via a helmet, increased PaO2/FiO2 and decreased dyspnea in both BL and UL; furthermore, it reduced the respiratory rate and brought PaCO2 up to normal in BL only. Compared to n-CPAP, n-CPAPSIGH significantly improved PaO2/FiO2 in BL (225 ± 88 vs. 308 ± 105, respectively), whereas it produced no further improvement in PaO2/FiO2 in UL (232 ± 72 vs. 231 ± 77, respectively). SIGH did not affect hemodynamics in both groups.
Compared to n-CPAP, n-CPAPSIGH further improved arterial oxygenation in BL patients, whereas it produced no additional benefit in those with UL.