title: Influence of immersion in water on muscle function and breathing pattern in patients with severe diaphragm weakness.
abstract: OBJECTIVE
  Dyspnea is a common symptom in patients with diaphragm weakness or paralysis. In particular, dyspnea may be aggravated by immersion. We hypothesized that immersion to the neck in water would decrease vital capacity and consequently increase the demand/capacity ratio of the respiratory muscles.
  
  
  METHODS
  Case series study.
  
  
  METHODS
  Seven patients with profound diaphragm weakness or paralysis proven by phrenic nerve stimulation, and seven normal control subjects.
  
  
  METHODS
  We measured land-based and water-based spirometry, breathing pattern, and mouth occlusion pressures.
  
  
  RESULTS
  We found that the patients could preserve minute ventilation despite a fall in vital capacity from a mean of 2.3 to 1.3 L, but this required an increased respiratory rate (RR) [21.4 to 26.7 breaths/min, p = 0.018]. We used mouth occlusion pressure 100 ms after the start of inspiration (P(0.1)) as an estimation of the drive to breath; P(0.1) increased from 1.4 to 3.9 cm H(2)O (p = 0.018) without significant change in tidal volume.
  
  
  CONCLUSIONS
  Relative to control subjects, patients with diaphragm weakness have augmented drive to breathe in order to attempt to defend gas exchange. This conclusion is implied by the presevered minute ventilation with immersion, the augmented RR, and elevated P(0.1) relative to maximum static inspiratory pressure.
authors.affiliation: Krankenhaus Kloster Grafschaft, Zentrum für Pneumologie, Grafschaft, Germany. Bernd.Schoenhofer@t-online.de
authors.forename: Bernd
authors.initials: B
authors.lastname: Schoenhofer
authors.forename: Dieter
authors.initials: D
authors.lastname: Koehler
authors.forename: Michael I
authors.initials: MI
authors.lastname: Polkey
mesh_terms: D000328:Adult; D000368:Aged; D016022:Case-Control Studies; D003964:Diaphragm / Q000503:physiopathology; D004417:Dyspnea / Q000175:diagnosis / Q000209:etiology; D005260:Female; D006801:Humans; D007101:Immersion; D008297:Male; D008875:Middle Aged; D018763:Muscle Fatigue / Q000502:physiology; D010791:Phrenic Nerve / Q000503:physiopathology; D011336:Probability; D011659:Pulmonary Gas Exchange / Q000502:physiology*; D012129:Respiratory Function Tests; D015656:Respiratory Mechanics; D012132:Respiratory Muscles / Q000503:physiopathology*; D012133:Respiratory Paralysis / Q000175:diagnosis*; D012494:Sampling Studies; D012680:Sensitivity and Specificity; D013147:Spirometry; D018709:Statistics, Nonparametric