title: Influence of lung collapse distribution on the physiologic response to recruitment maneuvers during noninvasive continuous positive airway pressure.
abstract: OBJECTIVE
  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 (B(L)) distribution of lung involvement would benefit from recruitment maneuvers more than those with unilateral (U(L)) involvement.
  
  
  METHODS
  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 B(L) and 12 U(L)) who underwent four consecutive trials: (1) 30 min breathing through a Venturi mask (V(MASK)), (2) 1 h n-CPAP (n-CPAP1), (3) 1 h n-CPAP plus SIGH (n-CPAP(SIGH)), and (4) 1 h n-CPAP (n-CPAP2).
  
  
  RESULTS
  Compared to V(MASK), n-CPAP at 10 cmH2O delivered via a helmet, increased PaO2/FiO2 and decreased dyspnea in both B(L) and U(L); furthermore, it reduced the respiratory rate and brought PaCO2 up to normal in B(L) only. Compared to n-CPAP, n-CPAP(SIGH) significantly improved PaO2/FiO2 in B(L) (225 ± 88 vs. 308 ± 105, respectively), whereas it produced no further improvement in PaO2/FiO2 in U(L) (232 ± 72 vs. 231 ± 77, respectively). SIGH did not affect hemodynamics in both groups.
  
  
  CONCLUSIONS
  Compared to n-CPAP, n-CPAP(SIGH) further improved arterial oxygenation in B(L) patients, whereas it produced no additional benefit in those with U(L).
authors.affiliation: Università del Piemonte Orientale Amedeo Avogadro-Alessandria-Novara-Vercelli, Dipartimento di Medicina Clinica e Sperimentale, Anesthesia and Intensive Care, University Hospital Maggiore della Carità, Via Solaroli 17, 28100, Novara, Italy.
authors.forename: Gianmaria
authors.initials: G
authors.lastname: Cammarota
authors.forename: Rosanna
authors.initials: R
authors.lastname: Vaschetto
authors.forename: Emilia
authors.initials: E
authors.lastname: Turucz
authors.forename: Fabrizio
authors.initials: F
authors.lastname: Dellapiazza
authors.forename: Davide
authors.initials: D
authors.lastname: Colombo
authors.forename: Cristiana
authors.initials: C
authors.lastname: Blando
authors.forename: Francesco
authors.initials: F
authors.lastname: Della Corte
authors.forename: Salvatore Maurizio
authors.initials: SM
authors.lastname: Maggiore
authors.forename: Paolo
authors.initials: P
authors.lastname: Navalesi
mesh_terms: D000208:Acute Disease; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D045422:Continuous Positive Airway Pressure / Q000295:instrumentation*; D005260:Female; D006439:Hemodynamics / Q000502:physiology; D006801:Humans; D008176:Lung Volume Measurements; D008297:Male; D008875:Middle Aged; D001261:Pulmonary Atelectasis / Q000503:physiopathology*; D012131:Respiratory Insufficiency / Q000209:etiology / Q000503:physiopathology / Q000628:therapy*; D015656:Respiratory Mechanics / Q000502:physiology