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Mechanical impedance is experienced to varying degrees by virtually all roots growing through soil. If continuous pores of sufficiently large diameter do not already exist, a root tip must exert a force to deform the soil. This process may considerably decrease root elongation rates, increase the root diameter and change the pattern of lateral root initiation (Russell, 1977). In this paper, the effects of mechanical impedance on root morphology are reviewed and some direct comparisons between soil resistance to root growth and resistance to a penetrometer are discussed. The physical process of. | International Ventilator Users Network An affiliate of Post-Polio Health International PHI HOME VENTILATOR GUIDE This project is made possible by a bequest from ventilator user Ira Holland. Copyright 2013 Post-Polio Health International PHI . All rights reserved. No part of this publication may be reproduced or transmitted in any form without permission in writing from the publisher. What is ventilation respiration Ventilation is the process of moving air in and out of the lungs. Respiration is the process during which the exchange of oxygen O2 and carbon dioxide CO2 occurs in the alveoli of the lungs. The alveoli are small air sacs at the end of the bronchial tree in the lungs and it is through the walls of these air sacs that O2 diffuses into the blood and CO2 diffuses out of the blood. Ventilation is a constant process of maintaining the proper balance between the two. What is a ventilator A ventilator also known as a respirator is the equipment used to mechanically assist breathing by delivering air to the lungs. Many people may be familiar with ventilators in the hospital setting such as the ICU where large complex acute care ventilators are used. The ventilators used in the home are small lightweight and portable they can be mounted on wheelchairs or carts or put on a bedside stand. Most of these operate on household electric current - some have internal batteries - and can be operated with external batteries. It is advisable to have a backup battery or even a generator readily available in case of power outages or emergencies. How does mechanical ventilation work The diaphragm is the primary muscle for inspiration along with the intercostal muscles between the ribs. Other muscles of the chest neck and shoulders play smaller roles. When these breathing muscles are weakened or paralyzed breathing becomes difficult or impossible. A mechanical ventilator can take over the act of breathing completely or make breathing easier by assisting weakened respiratory .