title: Respiratory vulnerability to vehicle buffeting.
abstract: OBJECTIVE
  Buffeting in a jerky ride in a bus or ambulance normally provokes a sustained tachypnoea driven by vibration and sensory mechanisms including vestibular signals. Tachypnoea reinforces the torso against mechanical shocks but results in overbreathing, causing a mild fall in CO(2). However, normal CO(2) is rapidly restored by a reduction in depth of breathing. We test the hypothesis that vulnerable subjects, exemplified by elderly individuals and patients with vestibular disorders, may fail to adapt to buffeting.
  
  
  METHODS
  Respiratory and cardiovascular functions were recorded from five elderly subjects, two patients with bilateral loss of vestibular function and five patients with 'BPPV,' while being exposed to 15-min buffeting in a flight simulator which simulated transport in an ambulance over rough pavement. Results were compared with published norms.
  
  
  RESULTS
  Some subjects sustained overbreathing during motion, through either tachypnoea or deep breathing, causing a marked reduction in CO(2) levels (3/5, 2/2 avestibular, 4/5 elderly, 4/5 BPPV). Others failed to raise breathing frequency which would render them susceptible to mechanical shock (4/5 elderly, 1/2 avestibular). Overbreathing was particularly evident in three anxious subjects.
  
  
  CONCLUSIONS
  Overbreathing during buffeting could be caused by (1) resetting of CO(2) rest levels lower; (2) change in receptor sensitivity; (3) adjustment of central drive to breathing; and (4) stiffening of posture because of motion discomfort reduced the ability to modulate breathing. The buffeting experienced was moderately violent. More profound hypocapnia and mechanical shock are likely to result in vulnerable individuals failing to adapt to severe buffeting in transport on unpaved roads, in war zones or by sea ambulance.
authors.affiliation: Academic Department of Neuro-otology, Division of Experimental Medicine, Imperial College London, Charing Cross Hospital Campus, London, UK.
authors.forename: Wei Lin
authors.initials: WL
authors.lastname: Sung
authors.forename: Neeraj
authors.initials: N
authors.lastname: Kohli
authors.forename: Shamim
authors.initials: S
authors.lastname: Qu'adir
authors.forename: John F
authors.initials: JF
authors.lastname: Golding
authors.forename: Adolfo M
authors.initials: AM
authors.lastname: Bronstein
authors.forename: Michael A
authors.initials: MA
authors.lastname: Gresty
mesh_terms: D000368:Aged; D000552:Ambulances; D001334:Automobile Driving; D005260:Female; D006801:Humans; D001239:Inhalation / Q000502:physiology; D008297:Male; D008875:Middle Aged; D012119:Respiration; D015837:Vestibular Diseases; D035862:Vulnerable Populations