Hello. Thanks for asking from HCM. I can understand your concern. There are mainly four manure gases which cause tissue damage - Hydrogen Sulfide, Ammonia, Carbon Monoxide, Methane. They cause mainly irritation of breathing apparatus e.g. nose, oral cavity, larynx, trachea and lungs. This is followed by poor oxygen intake and ultimately hypoxia and asphyxia. Poor oxygen amount in blood leads to damage of brain, heart and rest organs. Direct damage of brain and heart occurs at high concentration of these gases which is usually fatal. Now in case of your husband, damage of heart and brain can only be predicted after evaluating his signs and symptoms. If he is conscious, oriented, following simple commands, able to answer simple yes-no questions, able to remember important date/address/name of family members, able to move his all limbs and do his routine activities, then his brain damage is minimal to mild. If he is totally dependent upon you, not able to converse, having repeated fits, bed-ridden, making no purposeful movements like approaching glass of water etc, then he is having serious brain damage. Similarly heart damage can be mild like no shortness of breath, no chest pains, dyspnea occurs only after exertion, no dependent part swelling like in feet or severe like dyspnea even on lying down, palpitations with chest pain, dependent part swelling. It can only be evaluated after through clinical examination. The neurologist will evaluate him and may advise some tests like MRI of brain and EEG. MRI of brain helps in finding areas of brain damage which further predicts probability of fits, weakness, behavioural and personality changes. EEG will mainly find out chances of fits. After confirmation, he may be prescribed medications for fits (if present) like phenytoin or valproate, some nerve specific vitamins like B12, folic acid, pyridoxine, some nerve regenerator medications like citicoline. Besides all this, you can help him by giving full mental support, helping him in doing active physiotherapy like stretching of limbs and exercise, giving him puzzle questions to enhance his abstract thinking, ask him to play chess or Sudoku to sharpen his thinking, provide him diary to remember things to do daily. All this will be needed if he is having serious brain damage. In mild damage, he will recover completely with time. Thanks. Hope it will help you. Take care