TY  - CHAP
M1  - Book, Section
TI  - Introduction to Pulmonary Function Testing
A1  - Velez, Maria I.
A1  - Simpson, Tamara D.
A1  - Levine, Stephanie M.
A1  - Peters, Jay I.
A2  - DiPiro, Joseph T.
A2  - Talbert, Robert L.
A2  - Yee, Gary C.
A2  - Matzke, Gary R.
A2  - Wells, Barbara G.
A2  - Posey, L. Michael
PY  - 2017
T2  - Pharmacotherapy: A Pathophysiologic Approach, 10e
AB  - KEY  CONCEPTS  Normal  ventilation–perfusion  ratio.  The  function  of  the  lungs  is  to  maintain  arterial  partial  pressure  of  oxygen  (PaO2)  and  arterial  partial  pressure  of  carbon  dioxide  (PaCO2)  within  normal  ranges.  This  goal  is  accomplished  by  matching  1  mL  mixed  venous  blood  with  1  mL  fresh  air  (V̇/Q̇  =  1).  Normally,  ventilation  (V̇)  is  less  than  perfusion  (Q̇),  and  V̇/Q̇  ratio  is  0.8.  The  air  in  the  lung  is  divided  into  four  compartments:  tidal  volume—air  exhaled  during  quiet  breathing;  inspiratory  reserve  volume  (IRV)—maximal  air  inhaled  above  tidal  volume;  expiratory  reserve  volume  (ERV)—maximum  air  exhaled  below  tidal  volume;  and  residual  volume  (RV)—air  remaining  in  the  lung  after  maximal  exhalation.  The  sum  of  all  four  components  is  the  total  lung  capacity  (TLC).  Obstructive  lung  disease  is  defined  as  an  inability  to  get  air  out  of  the  lung.  It  is  identified  on  spirometry  when  forced  expiratory  volume  in  the  first  second  of  expiration  (FEV1)/forced  vital  capacity  (FVC)  (total  amount  of  air  that  can  be  exhaled  during  a  forced  exhalation)  (FEV1/FVC)  is  less  than  70%  to  75%  (or  below  the  lower  limit  of  normal  (LLN)  based  on  population  studies).  Reversible  airway  obstruction  is  common  in  asthma  and  is  sometimes  seen  in  chronic  obstructive  pulmonary  disease  (COPD).  An  increase  in  FEV1  of  12%  (and  greater  than  0.2  L  in  adults)  after  an  inhaled  β-agonist  suggests  an  acute  bronchodilator  response.  Restrictive  lung  disease  is  defined  as  an  inability  to  get  air  into  the  lung  and  is  best  defined  as  a  reduction  in  TLC  (usually  less  than  80%  predicted).  It  is  suspected  when  FVC  is  low  (less  than  80%  predicted)  and  FEV1/FVC  is  normal.  Restrictive  lung  disease  can  be  produced  by  a  number  of  defects,  such  as  increased  elastic  recoil  (interstitial  lung  disease),  respiratory  muscle  weakness  (myasthenia  gravis),  mechanical  restrictions  (pleural  effusion  or  kyphoscoliosis),  and  poor  effort.  
SN  - 
PB  - McGraw-Hill Education
CY  - New York, NY
Y2  - 2024/04/19
UR  - accesspharmacy.mhmedical.com/content.aspx?aid=1145219444
ER  -