Airflow distribution with manual hyperinflation as assessed through gamma camera imaging: a crossover randomised trial

ObjectivesManual hyperinflation (MHI) has been shown to improve lung compliance, reduce airway resistance, and enhance secretion removal and peak expiratory flow. The aims of this study were to investigate whether there is a difference in airflow distribution through patients' lungs when using the Laerdal and Mapleson-C circuits at a set level of positive end-expiratory pressure (PEEP), and to establish whether differences in lung compliance and haemodynamic status exist when patients are treated with both these MHI circuits.DesignCrossover randomised controlled trial.SettingAdult multidisciplinary intensive care unit (ICU) at an academic hospital.ParticipantsFifteen adult patients were recruited and served as their own controls.InterventionIn the Nuclear Medicine Department, MHI with PEEP 7.5 cmH2O was performed in the supine position (Day 1) with either Laerdal or Mapleson-C circuits, in a random order, while technetium-99m (Tc-99m) aerosol was administered and images were taken with a gamma camera. Changes in heart rate (HR), mean arterial pressure (MAP) and dynamic lung compliance (CD) were documented at baseline, immediately after return to ICU, and 10, 20 and 30 minutes after return to ICU. The alternative circuit was used on Day 2.ResultsTc-99m deposition was greater in the right lung field (62% and 63% for Laerdal and Mapleson-C circuits, respectively) than the left lung field (38% and 37%, respectively) for all patients, and least deposition occurred in the left lower segments (6% and 6%, respectively). No differences in Tc-99m deposition in the lungs, HR, MAP or CD were noted between the two MHI circuits.ConclusionAirflow distribution through patients' lungs was similar when the Laerdal and Mapleson-C MHI circuits were compared using a set level of PEEP in the supine position.