Impact of ventilation strategies during chest compression. An experimental study with clinical observations.

The optimal ventilation strategy during cardiopulmonary resuscitation (CPR) is unknown. Chest compression (CC) generates circulation, while during decompression, thoracic recoil generates negative pressure and venous return. Continuous flow insufflation of oxygen (CFI) allows noninterrupted CC and generates positive airway pressure (Paw). The main objective of this study was to assess the effects of positive Paw compared with the current recommended ventilation strategy on intrathoracic pressure (P(IT)) variations, ventilation, and lung volume. In a mechanical model, allowing compression of the thorax below an equilibrium volume mimicking functional residual capacity (FRC), CC alone or with manual bag ventilation were compared with two levels of Paw with CFI. Lung volume change below FRC at the end of decompression and P(IT), as well as estimated alveolar ventilation, were measured during the bench study. Recordings were obtained in five cardiac arrest patients to confirm the bench findings. Lung volume was continuously below FRC, and as a consequence P(IT) remained negative during decompression in all situations, including with positive Paw. Compared with manual bag or CC alone, CFI with positive Paw limited the fall in lung volume and resulted in larger positive and negative P(IT) variations. Positive Paw with CFI significantly augmented ventilation induced by CC. Recordings in patients confirmed a major loss of lung volume below FRC during CPR, even with positive Paw. Compared with manual bag ventilation, positive Paw associated with CFI limits the loss in lung volume, enhances CC-induced positive P(IT), maintains negative P(IT) during decompression, and generates more alveolar ventilation.

Respiratory physiotherapy to prevent pulmonary complications after abdominal surgery: a systematic review.

OBJECTIVES: To examine the efficacy of respiratory physiotherapy for prevention of pulmonary complications after abdominal surgery. METHODS: We searched in databases and bibliographies for articles in all languages through November 2005. Randomized trials were included if they investigated prophylactic respiratory physiotherapy and pulmonary outcomes, and if the follow-up was at least 2 days. Efficacy data were expressed as risk differences (RDs) and number needed to treat (NNT), with 95% confidence intervals (CIs). RESULTS: Thirty-five trials tested respiratory physiotherapy treatments. Of 13 trials with a "no intervention" control group, 9 studies (n = 883) did not report on significant differences, and 4 studies (n = 528) did: in 1 study, the incidence of pneumonia was decreased from 37.3 to 13.7% with deep breathing, directed cough, and postural drainage (RD, 23.6%; 95% CI, 7 to 40%; NNT, 4.3; 95% CI, 2.5 to 14); in 1 study, the incidence of atelectasis was decreased from 39 to 15% with deep breathing and directed cough (RD, 24%; 95% CI, 5 to 43%; NNT, 4.2; 95% CI, 2.4 to 18); in 1 study, the incidence of atelectasis was decreased from 77 to 59% with deep breathing, directed cough, and postural drainage (RD, 18%; 95% CI, 5 to 31%; NNT, 5.6; 95% CI, 3.3 to 19); in 1 study, the incidence of unspecified pulmonary complications was decreased from 47.7% to 21.4 to 22.2% with intermittent positive pressure breathing, or incentive spirometry, or deep breathing with directed cough (RD, 25.5 to 26.3%; NNT, 3.8 to 3.9). Twenty-two trials (n = 2,734) compared physiotherapy treatments without no intervention control subjects; no conclusions could be drawn. CONCLUSIONS: There are only a few trials that support the usefulness of prophylactic respiratory physiotherapy. The routine use of respiratory physiotherapy after abdominal surgery does not seem to be justified.

Factors associated with failure of noninvasive positive pressure ventilation in the emergency department.

OBJECTIVES: To determine the factors associated with failure of noninvasive positive pressure ventilation (NPPV) in patients presenting with acute respiratory failure to the emergency department (ED). METHODS: The authors retrospectively analyzed patients admitted to the ED for acute respiratory failure (defined as a PaCO2 level >45 mm Hg, and pH < or = 7.35 or a PaO2/FiO2 ratio < 250 mm Hg) and who were treated with NPPV. NPPV was delivered routinely according to an institutional protocol. Failure of NPPV was defined as the requirement of endotracheal intubation at any time. RESULTS: A total of 104 patients were included. NPPV failed in 31% (32/104), and the mortality was significantly higher in this group (12/32 [44%]) compared with patients who were not intubated (2/72 [3%]) (p < 0.0001). Factors associated with failure of NPPV were Glasgow Coma Scale score < 13 at ED admission (odds ratio [OR], 3.67; 95% confidence interval [CI] = 1.33 to 10.07), pH < or = 7.35 (OR, 3.23; 95% CI = 1.25 to 8.31), and respiratory rate (RR) > or =20 min(-1) (OR, 3.86; 95% CI = 1.33 to 11.17) after one hour of NPPV. The negative predictive value for NPPV failure was 86% (95% CI = 70% to 95%) for RR > or =20 min(-1). In the multivariate analysis, pH < or = 7.35 and RR > or =20 min(-1) after one hour of NPPV were independently associated with NPPV failure (adjusted ORs, 3.51; 95% CI = 1.29 to 9.62 and 3.55; 95% CI = 1.13 to 11.20, respectively). CONCLUSIONS: Patients with pH < or = 7.35 and an RR > or =20 min(-1) after one hour of NPPV had an increased risk of subsequent endotracheal intubation.

Continuous positive airway pressure versus noninvasive pressure support ventilation to treat atelectasis after cardiac surgery.

Atelectasis is common after cardiac surgery and may result in impaired gas exchange. Continuous positive airway pressure (CPAP) is often used to prevent or treat postoperative atelectasis. We hypothesized that noninvasive pressure support ventilation (NIPSV) by increasing tidal volume could improve the evolution of atelectasis more than CPAP. One-hundred-fifty patients admitted to our surgical intensive care unit (SICU) with a Radiological Atelectasis Score >or=2 after cardiac surgery were randomly assigned to receive either CPAP or NIPSV four times a day for 30 min. Positive end-expiratory pressure was set at 5 cm H(2)O in both groups. In the NIPSV group, pressure support was set to provide a tidal volume of 8-10 mL/kg. At SICU discharge, we observed an improvement of the Radiological Atelectasis Score in 60% of the patients with NIPSV versus 40% of those receiving CPAP (P = 0.02). There was no difference in oxygenation (Pao(2)/fraction of inspired oxygen at SICU discharge: 280 +/- 38 in the CPAP group versus 301 +/- 40 in the NIPSV group), pulmonary function tests, or length of stay. Minor complications, such as gastric distensions, were similar in the two groups. NIPSV was superior to CPAP regarding the improvement of atelectasis based on radiological score but did not confer any additional clinical benefit, raising the question of its usefulness for altering outcome.