title: Alteration of the piglet diaphragm contractility in vivo and its recovery after acute hypercapnia.
abstract: BACKGROUND
  The effects of hypercapnic acidosis on the diaphragm and its recovery to normocapnia have been poorly evaluated. The authors studied diaphragmatic contractility facing acute variations of arterial carbon dioxide tension (Paco2) and evaluated the contractile function at 60 min after normocapnia recovery.
  
  
  METHODS
  Thirteen piglets weighing 15-20 kg were anesthetized, ventilated, and separated into two groups: a control group (n = 5) evaluated in normocapnia (time-control experiments) and a hypercapnia group (n = 8) in which animals were acutely and shortly exposed to five consecutive ranges of Paco2 (40, 50, 70, 90, and 110 mmHg). Then carbon dioxide insufflation was stopped. Diaphragmatic contractility was assessed by measuring transdiaphragmatic pressure variations obtained after bilateral transjugular phrenic nerve pacing at increased frequencies (20-120 Hz). For each level of arterial pressure of carbon dioxide, pressure-frequency curves were obtained in vivo by phrenic nerve pacing.
  
  
  RESULTS
  In the hypercapnia group, mean +/- SD transdiaphragmatic pressure significantly decreased from 41 +/- 3 to 29 +/- 3 cm H2O (P < 0.05) between the first (40 mmHg) and fifth (116 mmHg) stages of capnia at the frequency of 100 Hz stimulation. The observed alteration of the contractile force was proportional to the level of Paco2 (r = 0.61, P < 0.01). Normocapnia recuperation allowed a partial recovery of the diaphragmatic contractile force (80% of the baseline value) at 60 min after carbon dioxide insufflation interruption.
  
  
  CONCLUSIONS
  A short exposure to respiratory acidosis decreased diaphragmatic contractility proportionally to the degree of hypercapnia, and this alteration was only partially reversed at 60 min after exposure.
authors: Department of Anesthesiology and Critical Care (DAR B), Centre Hospitalier Universitaire (CHU), Montpellier, France. s-jaber@chu-montpellier.fr
authors: Samir
authors: S
authors: Jaber
authors: Boris
authors: B
authors: Jung
authors: Mustapha
authors: M
authors: Sebbane
authors: Michèle
authors: M
authors: Ramonatxo
authors: Xavier
authors: X
authors: Capdevila
authors: Jacques
authors: J
authors: Mercier
authors: Jean-Jacques
authors: JJ
authors: Eledjam
authors: Stefan
authors: S
authors: Matecki
mesh_terms: D000208:Acute Disease; D000818:Animals; D000831:Animals, Newborn; D003964:Diaphragm / Q000502:physiology*; D006935:Hypercapnia / Q000503:physiopathology*; D009119:Muscle Contraction / Q000502:physiology*; D020127:Recovery of Function / Q000502:physiology*; D013552:Swine