title: Increased resistance of hygroscopic condenser humidifiers when using a closed circuit suction system.
abstract: OBJECTIVE
  To examine a hygroscopic condenser after clinical use and to describe the interaction of a hygroscopic condenser and a closed circuit suction system used simultaneously.
  
  
  METHODS
  Prospective evaluation of hygroscopic condensers used clinically, and laboratory investigation of a hygroscopic condenser used with a closed circuit suction system.
  
  
  METHODS
  Tertiary referral centers.
  
  
  RESULTS
  The hygroscopic condenser used during mechanical ventilation was removed and peak inflation pressure was measured by delivering a standard tidal volume and inspiratory flow across the isolated hygroscopic condenser while recording the peak inflation pressure. In the laboratory, four 10-mL aliquots of saline were instilled via closed circuit suction system into a test lung with fresh hygroscopic condensers (n = 15) inline. At baseline and after each instillation, the hygroscopic condenser was weighed and the peak inflation pressure was measured while in five condensers, peak expiratory flow rate was also measured. In these five devices, hygroscopic condenser resistance was measured with 100 L/min of constant gas flow while measuring the pressure drop across the hygroscopic condenser. In 11 hygroscopic condensers used for 27.5 +/- 11.9 hrs with no closed circuit suction system, the peak inflation pressure was 3.74 +/- 0.58 cm H2O. In the laboratory, instillation of saline via closed circuit suction system was associated with an increase in hygroscopic condenser weight. Peak inflation pressure increased in a quadratic fashion with the increase in hygroscopic condenser weight, while peak expiratory flow rate decreased in a linear fashion. After four saline instillations, hygroscopic condenser resistance increased from 5.66 +/- 0.31 to 13.9 +/- 2.42 cm H2O/L/sec.
  
  
  CONCLUSIONS
  Clinical use of a hygroscopic condenser alone is not associated with a significant increase in peak inflation pressure. We caution the use of a hygroscopic condenser and a closed circuit suction system simultaneously, as an increase in hygroscopic condenser resistance may develop and may be poorly tolerated in patients with marginal ventilatory reserve.
authors.affiliation: Division of Pulmonary and Critical Care Medicine, University of Michigan Hospital, Ann Arbor.
authors.forename: F J
authors.initials: FJ
authors.lastname: Martinez
authors.forename: S
authors.initials: S
authors.lastname: Pietchel
authors.forename: C
authors.initials: C
authors.lastname: Wise
authors.forename: J
authors.initials: J
authors.lastname: Walek
authors.forename: J F
authors.initials: JF
authors.lastname: Beamis
mesh_terms: D000368:Aged; D000403:Airway Resistance; D003422:Critical Care; D004867:Equipment Design; D005260:Female; D006801:Humans; D008297:Male; D008751:Methylene Blue / Q000008:administration & dosage; D008875:Middle Aged; D010366:Peak Expiratory Flow Rate; D011446:Prospective Studies; D012121:Respiration, Artificial / Q000295:instrumentation*; D012131:Respiratory Insufficiency / Q000628:therapy; D012965:Sodium Chloride / Q000008:administration & dosage; D013396:Suction
chemical_list: D012965:Sodium Chloride; D008751:Methylene Blue