Oxygen and CO2 transport pathways:
- The oxygen transport pathway ensures an adequate supply of oxygen to meet the demands of working tissues. In health oxygen delivery (DO2) is about 4 times greater than oxygen consumption (V02). This provides a considerable reserve which can be drawn upon during periods of increased metabolic demand such as exercise, stress, illness, and repair. Impairments for one component of the pathway can be compensated by another component to maintain normal gas exchange and PaO2 but severe impairment involving several components PaO2 may be compromised, inevitably increasing WOB and CO.
- The carbon dioxide pathway ensures this primary by-product of metabolism is eliminated.
FACTORS WHICH INFLUENCE OXYGEN TRANSPORT FROM THE ATMOSPHERE TO TISSUES:
Efficient transport of oxygen to the tissues relies on a number of interconnecting steps along the oxygen transport pathway:
- Ventilation of alveoli
- Diffusion of O2 across the alveolar capillary membrane
- Perfusion of the lungs
- Biochemical reaction of oxygen with the blood
- Affinity of oxygen with Hb
- Cardiac output (CO)
- Integrity of the peripheral circulation
- Oxygen extraction at tissue level
Optimum cardiopulmonary function and gas exchange rely on optimal matching of oxygen DEMAND and SUPPLY. O2 demand and supply matching relies on the integration of the heart and lungs working as a unit A CARDIOPULMONARY UNIT
O2 transport pathway in pathology:
The reserve capacity becomes compromised during Acute and Chronic pathological conditions:
- Acute: Of abrupt onset or an illness that is of short duration, rapidly progressive, and in need of urgent care
- Chronic: lasting a long time. A chronic condition is one that lasts 3 months or more. Chronic diseases are in contrast to those that are acute or subacute (within the interval between acute and chronic).
What is cardiopulmonary dysfunction:
Occurs when there is IMPAIRMENT in one or more of the steps in the oxygen transport pathway.
Impairment can be compensated for by other steps but severe Impairment results in:
-Reduces arterial oxygenation
-Increases Work of the heart and lungs
-Impairs Tissue oxygenation
-Ultimately Causes Multi-organ dysfunction/ failure, i.e. brain, kidneys, heart, lungs
Factors contributing to cardiopulmonary dysfunction:
4 main factors contribute to cardiopulmonary Dysfunction and impaired oxygen transport:
- Underlying Disease Pathophysiology
- Extrinsic Factors Imposed by Medical Care
- Intrinsic Factors Relating to Patient
- Bed rest/ Recumbency
Disease/pathophysiology factors that compromise O2 transport/cause cardiopulmonary dysfunction:
- Pneumonia/Chest infection: inflammatory exudate fills alveolar space reducing space available for O2 diffusion. Alveolar walls thickened increasing rate of diffusion
- COPD /Bronchiectasis
- Fractured Ribs: affect normal mechanism of breathing reducing ventilation
- Atelectasis
- Post operatively
- Acute Asthma
- Diabetes: poorly controlled may affect peripheral circulation
Relevance of O2 transport components to Physiotherapy:
Physiotherapists manipulate these components to promote oxygen delivery, i.e. Mobilisation and exercise involves the application of progressive exercise to elicit acute cardiopulmonary and cardiovascular responses to enhance oxygen transport and improve gas exchange for removal of CO2. It also strengthens LL enhancing ability of ADLs.
What is mobilisation:
mobilisation refers to any physical activity sufficient to elicit acute physiological effects which counter venous stasis and DVT and enhance: ventilation, central and peripheral perfusion, circulation, muscle metabolism, alertness
Indications for early rehabilitation/mobilisation:
- Evidence supports the use of early rehabilitation to reverse the negative effects of prolonged bed rest and inactivity that are defined as: deconditioning, muscle weakness, dyspnoea, depression and anxiety and reduced health related quality of life
- Early physical activity and rehabilitation within critical care is seen as a safe and feasible intervention after initial cardiovascular or neurological stabilisations.
Benefits of early rehabilitation:
- reduced incidences of pulmonary complications, improved levels of consciousness, hastens recovery, decreases duration of mechanical ventilation and reduces length of ICU or hospital stay.
- In addition improvements in respiratory function can occur as a result of optimising ventilation perfusion matching, increasing airway clearance and increasing lung volumes
Early rehabilitation strategies in order of intensity: In bed
- Passive range of movement to assess joint range and for patient comfort and use of accessory mobilisations if appropriate
- Positioning- passive, active assisted, and active turning e.g. rolling/ side lying
- Active assisted/Active movements and bed exercises
- Cardiac chair (in BED) Patients may only tolerate up to 30 minutes initially. Evaluate and then Increase time and frequency accordingly considering all relevant factors e.g. weaning plans. Aim for 2 times daily 30 to 60 minutes in preparation for sitting out.
- Functional exercises e.g. bridging /rolling/ Chair exercises
- Strengthening and resisted exercises(Physiotherapy tools, COPD exercise booklet)
Early rehabilitation strategies in order of intensity: sitting out to standing
Sit out in multi-function chair (Pat slide/hoist). Evaluate and then Increase time and frequency accordingly considering all relevant factors e.g. weaning plans, CVS instability, fatigue.
- Lie to sit transfers, sit on edge of bed. Sitting balance assessment and practice. Once independent sitting balance is achieved, patients may tolerate sitting in a ward chair.( Consider pressure relief)
- Sit to stand assessment and practice via standing hoist, rota stand ZF as appropriate e.g. pre-level?. Often AO2/3 initially
Early rehabilitation strategies in order of intensity: in standing
- Work in standing to assess and manage balance, posture, endurance, ability to transfer weight in preparation for standing transfers. Use of mechanical aids as appropriate including tilt table. N.B. Within critical care the Tilt table is useful for those patients with orthostatic intolerance (risk of postural hypotension) to acclimatise them to a more upright posture.
- Stepping in place i.e. Marching On The Spot (MOTS)
- Standing Transfer assessment and practice with appropriate aids e.g. Rota- stand, standing hoist, ZF etc.
- Stepping practice and gait re education
- Progress mobility to reduce aids and increase exercise tolerance. Consider therapeutic touch and massage for anxiety at any time
Classification of critical care:
- Level 0: Patients whose needs can be met through normal ward care in an acute hospital
- Level 1: Patients at risk of their condition deteriorating, or those recently relocated from higher levels of care, whose needs can be met on an acute ward with additional advice and support from the Critical Care team
- Level 2: Patients requiring more detailed observation or intervention including support for a single failing organ system or post-operative care and those ‘stepping down’ from higher levels of care
- Level 3: Patients requiring advanced respiratory support alone, or basic respiratory support together with support of at least two organ systems. This level includes all complex patients requiring support for multi-organ failure
- Level 2 and 3 are considered critically ill
Respiratory contraindications to early rehabilitation:
Compromised respiratory function/ sudden deterioration or worsening respiratory failure. Consider:
- fall in saturations of > 4%
- new increase in RR > 35 (not related to anxiety)
- Mechanically ventilated with FiO2 >0.8 and/or PEEP >12 or acutely worsening respiratory failure
- PH <7.25
- PaO2/FiO2 ratio. Ideally in COPD >150-180 and in non COPD > 200-250 if you want to be sure of the patients respiratory reserve
CVS Contraindications to early rehabilitation:
-Intra-Aortic Balloon Pump in situ (IABP)
-MAP ≥ 60 and no sudden or large swings in BP
-Significant dose of vasoactive agents (e.g. noradrenalin > 0.2 mcg/kg/min or equivalent) to maintain MAP >60
-Cardiovascular reserve (Observe resting HR and consider the patients likely maximum HR. This is equal to 220 minus their age)
-During activity the patients HR should ideally only reach 50% to 85% of maximal HR
Any acute cardiac problems such as :
§ Unstable angina
§ Uncontrolled arrhythmias
§ Symptomatic Heart failure
§ Acute myocarditis
§ Acute pericarditis
§ Suspected dissecting aneurysm
§General appearance is an important assessment tool e.g. clamminess, sweating, Pallor.
Other contraindications to early rehabilitation:
- Active bleeding process contra-indicate passive stretching
- unstable spine or extremity fractures with contraindications to mobilise
- Neuromuscular paralysing agent: sensory loss
- Acute neurological event e.g. CVA <24 hours or CSF leak: risk of bleed
Precautions to early rehabilitation:
At any level of rehabilitation the following precautions may need to be considered and intervention tailored appropriately:
- Small dose of vasoactive agents (noradrenalin 0.1-0.2 mcg/kg/min or equivalent) to maintain -MAP >60
- Mechanical Ventilation with Fio2 >60% and/or PEEP >10
- Open abdomen or high risk of dehiscence: Check with surgeons
- Haemofiltration via a femoral line: cautious
- Changes in HR, new ectopics and/or arrythmias
- Increased work of breathing / poor respiratory reserve (calculated using Pao2 Fio2 ratio)
- Poor tolerance of ETT or tracheostomy: exacerbate gagging
-
Assessment13
-
Auscultation17
-
CXR16
-
Positioning + Lung Function21
-
Chest X Ray Abnormalities5
-
Breathing Re-education & Sputum Management55
-
General Anaesthesia22
-
Management of volume loss26
-
Paediatric Respiratory Care19
-
ABGs24
-
Respiratory Failure23
-
O2 Therapy36
-
Management of Breathlessness43
-
Critical Care39
-
Mechanical Ventilation49
-
Management of volume loss in ITU16
-
Mobilisation18
